Inhibitors of nucleoside metabolism Number:6,803,455 from the United States Patent and Trademark Office (PTO) owispatent The present invention provides compounds having the formula: ##STR1##wherein A is CH or N; B is chosen from OH, NH.sub.2, NHR, H or halogen; D is chosen from OH, NH.sub.2, NHR, H, halogen or SCH.sub.3 ; R is an optionally substituted alkyl, aralkyl or aryl group; and X and Y are independently selected from H, OH or halogen except that when one of X and Y is hydroxy or halogen, the other is hydrogen; and Z is OH or, when X is hydroxy, Z is selected from hydrogen, halogen, hydroxy, SQ or OQ, Q is an optionally substituted alkyl, aralkyl or aryl group; or a tautomer thereof; or a pharmaceutically acceptable salt thereof; or an ester thereof; or a prodrug thereof; and compounds having the formula: ##STR2##wherein A, X, Y, Z and R are defined for compounds of formula (I) where first shown above; E is chosen from CO.sub.2 H or a corresponding salt form, CO.sub.2 R, CN, CONH.sub.2, CONHR or CONR.sub.2 ; and G is chosen from NH.sub.2, NHCOR, NHCONHR or NHCSNHR; or a tautomer thereof, or a pharmaceutically acceptable salt thereof, or an ester thereof, or a prodrug thereof.The present invention also provides the use of the above compounds as pharmaceuticals, pharmaceutical compositions containing the compounds and processes for preparing the compounds.<H metabolism, nucleoside, Inhibitors, of, n, 6803455.html, Patent, pto, 6803455

Title: Inhibitors of nucleoside metabolism

Abstract: The present invention provides compounds having the formula: ##STR1##wherein A is CH or N; B is chosen from OH, NH.sub.2, NHR, H or halogen; D is chosen from OH, NH.sub.2, NHR, H, halogen or SCH.sub.3 ; R is an optionally substituted alkyl, aralkyl or aryl group; and X and Y are independently selected from H, OH or halogen except that when one of X and Y is hydroxy or halogen, the other is hydrogen; and Z is OH or, when X is hydroxy, Z is selected from hydrogen, halogen, hydroxy, SQ or OQ, Q is an optionally substituted alkyl, aralkyl or aryl group; or a tautomer thereof; or a pharmaceutically acceptable salt thereof; or an ester thereof; or a prodrug thereof; and compounds having the formula: ##STR2##wherein A, X, Y, Z and R are defined for compounds of formula (I) where first shown above; E is chosen from CO.sub.2 H or a corresponding salt form, CO.sub.2 R, CN, CONH.sub.2, CONHR or CONR.sub.2 ; and G is chosen from NH.sub.2, NHCOR, NHCONHR or NHCSNHR; or a tautomer thereof, or a pharmaceutically acceptable salt thereof, or an ester thereof, or a prodrug thereof.The present invention also provides the use of the above compounds as pharmaceuticals, pharmaceutical compositions containing the compounds and processes for preparing the compounds.

Patent Number: 6,803,455 Issued on 10/12/2004 to Furneaux, et al.

Inventors: Furneaux; Richard Hubert (Wellington, NZ); Tyler; Peter Charles (Wellington, NZ); Schramm; Vern L. (New Rochelle, NY)
Assignee: Albert Einstein College of Medicine of Yeshiva University (Bronx, NY)
Industrial Research Limited (Lower Hutt, NZ)

Appl. No.: 10/268,652

Filed: October 10, 2002

Related U.S. Patent Documents


Application Number	Filing Date	Patent Number	Issue Date
820276	Mar., 2001	6492347
496741	Feb., 2000	6228847
172321	Oct., 1998	6066722
949388	Oct., 1997	5985848

Current U.S. Class: 536/4.1 ; 536/23.1

Field of Search: 536/4.1,23.1 514/1,44

References Cited [Referenced By]

U.S. Patent Documents


4711955	December 1987	Ward et al.
5223618	June 1993	Cook et al.
5466786	November 1995	Buhr et al.
5506351	April 1996	McGee
5985848	November 1999	Furneaux et al.
6066722	May 2000	Furneaux et al.
6228847	May 2001	Furneaux et al.
6492347	December 2002	Furneaux et al.

Other References

Furneaux R. H., entitled "Synthesis of Transition State Inhibitors for N-Riboside Hydrolases and Transferases," Tetrahedron, vol. 53, No. 8, pp. 2915-2930, 1997. .
Yan, Jieming et al., entitled "High Performance liquid chromatographic determination of 9-(3-pyridylmethyl)-9-deazaguanine (BCX-34) in biological fluids," Journal of Chromatography B. 690 (1997) 295-303. .
Bols, Michael entitled "Synthesis of a Ribofuranosyl Cation Mimic," Tetrahedron Letters, vol. 37, No. 12, pp. 2097-2100, 1996. .
Miles, Robert W et al., entitled "One-Third-the-Sites Transition-State Inhibitors for Purine Nucleoside Phosphorylase," Biochemistry, vol. 37, No. 24, 1998, pp. 8615-8621. .
Kline, et al., Pre-Steady-State Transition-State Analysis of the Hydrolytic Reaction Catalyzed by Purine Nucleoside Phosphorylase, Biochemistry 1995, 34, 1153-1162..

Primary Examiner: Riley; Jezia
Attorney, Agent or Firm: Amster, Rothstein & Ebenstein LLP

Parent Case Text

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. appplication Ser. No. 09/820,276, filed Mar. 28, 2001, now U.S. Pat. No. 6,492,347 B2, which is a continuation of U.S. application Ser. No. 09/496,741, filed Feb. 3, 2000, now U.S. Pat. No. 6,228,847 B1, which is a continuation of U.S. application Ser. No. 09/172,321, filed Oct. 14, 1998, now U.S. Pat. No. 6,066,722, which is a continuation-in-part of U.S. application Ser. No. 08/949,388, filed Oct. 14, 1997, now U.S. Pat. No. 5,985,848, the contents of which are hereby incorporated by reference in their entirety.

Claims

What is claimed is:

1. A compound having the formula: ##STR25##

wherein A is CH or N; B is chosen from OH, NH.sub.2, NHR, H or halogen; D is chosen from OH, NH.sub.2, NHR, H, halogen or SCH.sub.3 ; R is an optionally substituted alkyl, aralkyl or aryl group; and X and Y are independently selected from H, OH or halogen except that when one of X and Y is hydroxy or halogen, the other is hydrogen; and Z is OH or, when X is hydroxy, Z is selected from hydrogen, halogen, hydroxy, SQ or OQ where Q is an optionally substituted alkyl, aralkyl or aryl group; or a tautomer thereof; or a pharmaceutically acceptable salt thereof.

2. The compound of claim 1, wherein one of B and/or D is NHR, and R is C.sub.1 -C.sub.4 alkyl.

3. The compound of claim 1, wherein either D is H, or B is OH, or both.

4. The compound of claim 1, wherein B is OH, D is H, OH or NH.sub.2, X is OH or H, Y is H.

5. The compound of claim 1, wherein Z is OH, H or methylthio.

6. The compound of claim 5, wherein Z is OH.

7. A pharmaceutical composition for the suppression of T-cell function comprising an amount of a compound of claim 1 effective for inhibiting purine nucleoside phosphorylase, and a pharmaceutically acceptable carrier or diluent.

8. A pharmaceutical composition for treatment and/or prophylaxis of a protozoan infection comprising an amount of a compound of claim 1 effective for inhibiting at least one parasite purine nucleoside hydrolase, purine nucleoside phosphorylase and/or purine phosphoribosyl transferase and a pharmaceutically acceptable carrier or diluent.

9. A method for decreasing T-cell function in a mammal comprising administering to the mammal a compound of claim 1, whereby said compound inhibits purine nucleoside phosphoiylase.

10. A method for treatment and/or prophylaxis of an infection caused by protozoan parasite comprising administering to a subject an amount of a compound of claim 1 effective to inhibit at least purine nucleoside hydrolase, purine nucleoside phosphorylase, and/or purine phosphoribosyl transferase.

11. A method for killing parasites comprising administering to the parasite an amount of a compound of claim 1 effective for inhibiting at least one purine nucleoside hydrolase, purine nucleoside phosphorylase, and/or purine phosphoribosyl transferase.

Description

TECHNICAL FIELD

The invention relates to certain nucleoside analogues, the use of these compounds as pharmaceuticals, pharmaceutical compositions containing the compounds and processes for preparing the compounds.

BACKGROUND OF THE INVENTION

Purine nucleoside phosphorylase (PNP) catalyses the phosphorolytic cleavage of ribo- and deoxyribonucleosides, for example, those of guanine and hypoxanthine to give the corresponding sugar-1-phosphate and guanine, hypoxanthine, or other purine bases.

Humans deficient in purine nucleoside phosphorylase (PNP) suffer a specific T-cell immunodeficiency due to an accumulation of dGTP and its toxicity to stimulated T lymphocytes. Because of this, inhibitors against PNP are immunosuppressive, and are active against T-cell malignancies. Clinical trials are now in progress using 9-(3-pyridylmethyl)-9-deazaguanine in topical form against psoriasis and in oral form for T-cell lymphoma and immunosuppression (BioCryst Pharmaceuticals, Inc). The compound has an IC.sub.50 of 35 nM for the enzyme. In animal studies, a 50 mg/kg oral dose is required for activity in a contact sensitivity ear swelling assay in mice. For human doses, this would mean approximately 3.5 grams for a 70 kg human. With this inhibitor, PNP is difficult to inhibit due to the relatively high activity of the enzyme in blood and mammalian tissues.

Nucleoside and deoxynucleoside hydrolases catalyse the hydrolysis of nucleosides and deoxynucleosides. These enzymes are not found in mammals but are required for nucleoside salvage in some protozoan parasites. Purine phosphoribosyltransferases (PPRT) catalyze the transfer of purine bases to 5-phospho-.alpha.-D-ribose-1-pyrophosphate to form purine nucleotide 5'-phosphates. Protozoan and other parasites contain PPRT which are involved in essential purine salvage pathways. Malignant tissues also contain PPRT. Some protozoan parasites contain purine nucleoside phosphorylases which also function in purine salvage pathways. Inhibitors of nucleoside hydrolases, purine nucleoside phosphorylases and PPRT can be expected to interfere with the metabolism of parasites and therefore be usefully employed against protozoan parasites. Inhibitors of PNP and PPRT can be expected to interfere with purine metabolism in malignant tissues and therefore be usefully employed against malignant tissues.

It is an object of the invention to provide pharmaceuticals which are very effective inhibitors of PNP, PPRT and/or nucleoside hydrolases.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1: FIG. 1 shows purine nucleoside phosphorylase activity with time at a range of concentrations of the product of Example 1 (Compound Ib).

FIG. 2: FIG. 2 shows fitting of a purine nucleoside phosphorylase activity progress curve to the kinetic model.

FIG. 3: FIG. 3 shows K.sub.i * determination by the curve fit method for Compound Ib inhibition of bovine purine nucleoside phosphorylase.

FIG. 4: FIG. 4 shows a progress curve for bovine purine nucleoside phosphorylase showing slow-onset inhibition by Compound Ib.

FIG. 5: FIG. 5 shows the effect of oral administration of Compound Ib on the PNP activity of mouse blood.

FIG. 6: FIG. 6 shows the K.sub.i determination for Compound Ib with protozoan nucleoside hydrolase.

FIG. 7: FIG. 7 shows the progress curve for purine phosphoribosyltransferase showing slow-onset inhibition by the 5'-phosphate of Compound Ib. Inhibition of the malaria enzyme.

FIG. 8: FIG. 8 shows the K.sub.1 * determination for the 5'-phosphate of Compound Ib inhibition of human purine phosphoribosyltransferase.

DETAILED DESCRIPTION OF THE INVENTION

In one aspect the invention provides compounds having the formula: ##STR3##

wherein A is CH or N; B is chosen from OH, NH.sub.2, NHR, H or halogen; D is chosen from OH, NH.sub.2, NHR, H, halogen or SCH.sub.3 ; R is an optionally substituted alkyl, aralkyl or aryl group; and X and Y are independently selected from H, OH or halogen except that when one of X and Y is hydroxy or halogen, the other is hydrogen; and Z is OH or, when X is hydroxy, Z is selected from hydrogen, halogen, hydroxy, SQ or OQ, Q is an optionally substituted alkyl, aralkyl or aryl group; or a tautomer thereof; or a pharmaceutically acceptable salt thereof; or an ester thereof; or a prodrug thereof.

Preferably when either of B and/or D is NHR, then R is C.sub.1- C.sub.4 alkyl.

Preferably when one or more halogens are present they are chosen from chlorine and fluorine.

Preferably when Z is SQ or OQ, Q is C.sub.1 -C.sub.5 alkyl or phenyl.

Preferably D is H, or when D is other than H, B is OH.

More preferably, B is OH, D is H, OH or NH.sub.2, X is OH or H, Y is H, most preferably with Z as OH, H or methylthio, especially OH.

It will be appreciated that the representation of a compound of formula (I) wherein B and/or D is a hydroxy group used herein is of the enol-type tautomeric form of a corresponding amide, and this will largely exist in the amide form. The use of the enol-type tautomeric representation is simply to allow fewer structural formulae to represent the compounds of the invention.

The present invention also provides compounds having the formula: ##STR4##

wherein A, X, Y, Z and R are defined for compounds of formula (I) where first shown above; E is chosen from CO.sub.2 H or a corresponding salt form, CO.sub.2 R, CN, CONH.sub.2, CONHR or CONR.sub.2 ; and G is chosen from NH.sub.2, NHCOR, NHCONHR or NHCSNHR; or a tautomer thereof, or a pharmaceutically acceptable salt thereof, or an ester thereof, or a prodrug thereof.

Preferably E is CONH.sub.2 and G is NH.sub.2.

More preferably, E is CONH.sub.2, G is NH.sub.2, X is OH or H, Y is H, most preferable with Z as OH, H or methylthio, especially OH.

Particularly preferred are the following compounds:

1. (1S)-1,4-dideoxy-1-C-(4-hydroxypyrrolo[3,2-d]pyrimidin-7-yl)-1,4-imino-D-r ibitol

2. (1S)-1-C-(2-amino-4-hydroxypyrrolo[3,2-d]pyrimidin-7-yl)-1,4-dideoxy-1,4-i mino-D-ribitol

3. (1R)-1-C-(4-hydroxypyrrolo[3,2-d]pyrimidin-7-yl)-1,4-imino-1,2,4-trideoxy- D-erythro-pentitol

4. (1S)-1-C-(4-hydroxypyrrolo[3,2-d]pyrimidin-7-yl)-1,4-imino-1,4,5-trideoxy- D-ribitol

5. (1S)-1,4-dideoxy-1-C-(4-hydroxypyrrolo[3,2-d]pyrimidin-7-yl)-1,4-imino-5-m ethylthio-D-ribitol

6. (1S)-1,4-dideoxy-1-C-(2,4-dihydroxypyrrolo[3,2-d]pyrimidin-7-yl)-1,4-imino -D-ribitol

7. (1R)-1-C-(2,4-dihydroxypyrrolo[3,2-d]pyrimidin-7-yl)-1,4-imino-1,2,4-tride oxy-D-erythro-pentitol

8. (1S)-1-C-(2,4-dihydroxypyrrolo[3,2-d]pyrimidin-7-yl)-1,4-imino-1,4,5-tride oxy-D-ribitol

9. (1S)-1,4-dideoxy-1-C-(2,4-dihydroxypyrrolo[3,2-d]pyrimidin-7-yl)-1,4-imino -5-methylthio-D-ribitol

10. (1R)-1-C-(2-amino-4-hydroxypyrrolo[3,2-d]pyrimidin-7-yl)-1,4-imino-1,2,4-t rideoxy-D-erythro-pentitol

11. (1S)-1-C-(2-amino-4-hydroxypyrrolo[3,2-d]pyrimidin-7-yl)-1,4-imino-1,4,5-t rideoxy-D-ribitol

12. (1S)-1-C-(2-amino-4-hydroxypyrrolo[3,2-d]pyrimidin-7-yl)-1,4-dideoxy-1,4-i mino-5-methylthio-D-ribitol

13. (1S)-1,4-dideoxy-1-C-(7-hydroxypyrazolo[4,3-d]pyrimidin-3-yl)-1,4-imino-D- ribitol

14. (1R)-1-C-(7-hydroxypyrazolo[4,3-d]pyrimidin-3-yl)-1,4-imino-1,2,4-trideoxy -D-erythro-pentitol

15. (1S)-1-C-(7-hydroxypyrazolo[4,3-d]pyrimidin-3-yl)-1,4-imino-1,4,5-trideoxy -D-ribitol

16. (1S)-1,4-dideoxy-1-C-(7-hydroxypyrazolo[4,3-d]pyrimidin-3-yl)-1,4-imino-5- methylthio-D-ribitol

17. (1S)-1,4-dideoxy-1-C-(5,7-dihydroxypyrazolo[4,3-d]pyrimidin-3-yl)-1,4-imin o-D-ribitol

18. (1R)-1-C-(5,7-dihydroxypyrazolo[4,3-d]pyrimidin-3-yl)-1,4-imino-1,2,4-trid eoxy-D-erythro-pentitol

19. (1S)-1-C-(5,7-dihydroxypyrazolo[4,3-d]pyrimidin-3-yl)-1,4-imino-1,4,5-trid eoxy-D-ribitol

20. (1S)-1,4-dideoxy-1-C-(5,7-dihydroxypyrazolo[4,3-d]pyrimidin-3-yl)-1,4-imin o-5-methylthio-D-ribitol

21. (1S)-1-C-(5-amino-7-hydroxypyrazolo[4,3-d]pyrimidin-3-yl)-1,4-dideoxy-1,4- imino-D-ribitol

22. (1R)-1-C-(5-amino-7-hydroxypyrazolo[4,3-d]pyrimidin-3-yl)-1,4-imino-1,2,4- trideoxy-D-erythro-pentitol

23. (1S)-1-C-(5-amino-7-hydroxypyrazolo[4,3-d]pyrimidin-3-yl)-1,4-imino-1,4,5- trideoxy-D-ribitol

24. (1S)-1-C-(5-amino-7-hydroxypyrazolo[4,3-d]pyrimidin-3-yl)-1,4-dideoxy-1,4- imino-5-methylthio-D-ribitol

25. (1S)-1-C-(3-amino-2-carboxamido-4-pyrroly)-1,4-dideoxy-1,4-imino-D-ribitol .

26. (1S)-1,4-dideoxy-1-C-(4-hydroxypyrrolo[3,2-d]pyrimidin-7-yl)-1,4-imino-D-r ibitol 5-phosphate

27. (1S)-1-C-(2-amino-4-hydroxypyrrolo[3,2-d]pyrimidin-7-yl)-1,4-imino-D-ribit ol 5-phosphate

28. (1S)-1-C-(3-amino-2-carboxamido-4-pyrrolyl)-1,4-dideoxy-1,4-imino-D-ribito l

Most preferred are compounds Ib and Ic, their tautomers and pharmaceutically acceptable salts. ##STR5##

The biological availability of a compound of formula (I) or formula (Ia) can be enhanced by conversion into a pro-drug form. Such a pro-drug can have improved lipophilicity relative to the compound of formula (I) or formula (Ia), and this can result in enhanced membrane permeability. One particularly useful form of a pro-drug is an ester derivative. Its utility relies upon the action of one or more of the ubiquitous intracellular lipases to catalyse the hydrolysis of these ester group(s), to release the compound of formula (I) and formula (Ia) at or near its site of action.

In one form of a prodrug, one or more of the hydroxy groups in a compound of formula (I) or formula (Ia) can be O-acylated, to make, for example a 5-O-butyrate or a 2,3-di-O-butyrate derivative.

Prodrug forms of 5-phosphate ester derivative of a compounds of formula (I) or formula (Ia) can also be made and may be particularly useful, since the anionic nature of the 5-phosphate may limit its ability to cross cellular membranes. Conveniently, such a 5-phosphate derivative can be converted to an uncharged bis(acyloxymethyl) ester derivative. The utility of such a pro-drug relies upon the action of one or more of the ubiquitous intracellular lipases to catalyse the hydrolysis of these ester group(s), releasing a molecule of formaldehyde and the compound of formula (I) or formula (Ia) at or near its site of action.

Specific examples of the utility of, and general methods for making, such acyloxymethyl ester pro-drug forms of phosphorylated carbohydrate derivatives have been described, e.g. Kang et al., Nucleosides Nucleotides 17 (1998) 1089; Jiang et al., J. Biol. Chem., 273 (1998) 11017; Li et al., Tetrahedron 53 (1997) 12017; and Kruppa et al., Bioorg. Med. Chem. Lett., 7 (1997) 945.

According to another aspect of the invention, there is provided a pharmaceutical composition comprising a pharmaceutically effective amount of a compound of the first aspect of the invention.

Preferably the pharmaceutical composition comprises a compound chosen from the preferred compounds of the first aspect of the invention; more preferably the compound is chosen from the more preferred compounds of the first aspect. Most preferably the compound is the compound of formula Ib or Ic.

In another aspect the invention provides methods for treatment of diseases or conditions in which it is desirable to decrease the level of T lymphocyte activity. The methods comprise administering a pharmaceutically effective dose of a compound of the invention to a patient requiring treatment.

The diseases include T-cell malignancies and autoimmune diseases including arthritis and lupus. This aspect of the invention also includes use of the compounds for immunosuppression for organ transplantation and for inflammatory disorders. The invention includes use of the compounds for manufacture of medicaments for these treatments.

In another aspect the invention provides a method for treatment and/or prophylaxis of parasitic infections, particularly those caused by protozoan parasites. Included among the protozoan parasites are those of the genera Giardia, Trichomonas, Leishmania, Trypanosoma, Crithidia, Herpetomonas, Leptomonas, Histomonas, Eimeria, Isopora and Plasmodium. An example of a parasitic infection caused by Plasinodium is malaria. The method can be advantageously applied with any parasite containing one or more nucleoside hydrolases inhibited by the compound of the invention when administered in an amount providing an effective concentration of the compound at the location of the enzyme.

In another aspect, the invention provides a method of preparing the compounds of the first aspect of the invention. The method may include one or more of methods (A)-(Z) and (AA)-(AF).

Method (A): (4-hydroxypyrrolo[3,2-d]pyrimidines and access to 5'-deoxy--, 5'-deoxy-5'-halogeno-, 5'-ether and 5'-thio-analogues)

reacting a compound of formula (II) ##STR6##

[wherein Z' is a hydrogen or halogen atom, a group of formula SQ or OQ, or a trialkylsilyloxy, alkyldiarylsilyloxy or optionally substituted triarylmethoxy group and Q is an optionally substituted alkyl, aralkyl or aryl group,] (typically Z' is a tert-butyldimethylsilyloxy, trityloxy or similar group) sequentially with N-chlorosuccinimide then a sterically hindered base (such as lithium tetramethylpiperadide) to form an imine, then with the anion of acetonitrile (typically made by treatment of acetonitrile with n-butyllithium) followed by di-tert-butyl dicarbonate. This generates a compound of formula (III) ##STR7##

[wherein Z' is as defined for formula (II) where first shown above] which is then elaborated following the approach used to prepare 9-deazainosine [Lim et al., J. Org. Chem., 48 (1983) 780] in which a compound of formula (III) is condensed with (Me.sub.2 N).sub.2 CHOBu.sup.t and hydrolyzed under weakly acidic conditions to a compound of formula (IV) ##STR8##

[wherein Z' is as defined for formula (II) where first shown above] which is then sequentially condensed with a simple ester of glycine (e.g. ethyl glycinate) under mildly basic conditions, cyclized by reaction with a simple ester of chloroformic acid (e.g. benzyl chloroformate or methyl chloroformate) and then deprotected on the pyrrole nitrogen by hydrogenolysis in the presence of a noble metal catalyst (e.g. Pd/C) in the case of a benzyl group or under mildly basic conditions in the case of a simple alkyl group such as a methyl group, to give a compound of formula (V) ##STR9##

[wherein Z' is as defined for formula (II) where first shown above, and R is an alkyl group] (typically R is a methyl or ethyl group) which is then condensed with formamidine acetate to give a compound of formula (VI) ##STR10##

[wherein Z' is as defined for formula (II) where first shown above] which is then fully deprotected under acidic conditions, e.g. by treatment with trifluoroacetic acid.

Methods for the preparation of a compourd of formula (II) wherein Z' is a tert-butyldimethylsilyloxy group are detailed in Furneaux et al, Tetrahedron 53 (1997) 2915 and references therein.

A compound of formula (II) [wherein Z' is a halogen atom], can be prepared from a compound of formula (II) [wherein Z' is a hydroxy group], by selective N-alkyl- or aralkyl-oxycarbonylation (typically with di-tert-butyl dicarbonate, benzyl chloroformate, or methyl chloroformate and a base) or N-acylation (typically with trifluoroacetic anhydride and a base) to give a compound of formula (VII): ##STR11##

[wherein R is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl-carbonyl group and Z' is a hydroxy group] which is then either:

(i) 5-O-sulfonylated (typically with p-toluenesulfonyl chloride, methanesulfonyl chloride or trifluoromethanesulfonic anhydride and a base) to give a compound of formula (VII) [wherein R is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl-carbonyl group and Z' is an optionally substituted alkyl- or aryl-sulfonyloxy group], then subjected to a sulfonate displacement reaction with a reagent capable of providing a nucleophilic source of halide ion (typically nedium, lithium or a tetraalkylammonium fluoride, chloride, bromide, or iodide); or

(ii) subjected to a reagent system capable of directly replacing a primary hydroxy group with a halogen atom, for example as in the Mitsunobu reaction (e.g. using triphenylphosphine, diethyl azodicarboxylate and a nucleophilic source of halide ion as above), by reaction with diethylaminosulfur trifluoride (DAST), or by reaction with methyltriphenoxyphosphonium iodide in dimethylformamide [see e.g. Stoeckler et al, Cancer Res., 46 (1986) 1774] or by reaction with thionyl chloride or bromide in a polar solvent such as hexamethylphosphoramide [Kitagawa and Ichino, Tetrahedron Lett., (1971) 87] to give a compound of formula (VII) [wherein R is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl-carbonyl group and Z' is a halogen atom], which is then selectively N-deprotected by acid- or alkali-catalyzed hydrolysis or alcoholysis or catalytic hydrogenolysis as required for the N-protecting group in use.

A compound of formula (VII) [wherein R is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl-carbonyl group and Z' is a hydroxy group] can also be prepared from a compound of formula (II) [wherein Z' is a trialkylsilyloxy, alkyldiarylsilyloxy or optionaily substituted triarylmethoxy group], by N-alkyl- or aralkyl-carboxylation or N-acylation as above, then selective 5-O-deprotection by acid-catalyzed hydrolysis or alcoholysis, catalytic hydrogenolysis, or treatment with a source of fluoride ion (eg tetrabutylammonium fluoride) as required for the 5-O-protecting group in use.

The compound of formula (II) [wherein Z' is a hydrogen atom] can be prepared from either:

(i) a 5-hydroxy compound of formula (VII) [wherein R is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl-carbonyl group and Z' is a hydroxy group], by formation and radical deoxygenation of a 5-O-thioacyl derivative; or

(ii) a 5-deoxy-5-halogeno-compound of formula (VII) [wherein Z' is a chlorine, bromine or iodine atom] by reduction, either using a hydride reagent such as tributyltin hydride under free radical conditions, or by catalytic hydrogenolysis, typically with hydrogen over a palladium catalyst; followed by selective N-deprotection by acid- or alkali-catalyzed hydrolysis or alcoholysis or catalytic hydrogenolysis as required for the N-protecting group in use.

A compound of formula (II) [wherein Z' is an optionally substituted alkylthio, aralkylthio or arylthio group] can be prepared by reaction of a 5-deoxy-5-halogeno or a 5-O-sulfonate derivative of formula (VII) [wherein R is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl-carbonyl group and Z' is a halogen atom or an optionally substituted alkyl- or aryl-sulfonyloxy group] mentioned above, with an alkali metal or tetraalkylammonium salt of the corresponding optionally substituted alkylthiol, aralkylthiol or arylthiol followed by selective N-deprotection by acid- or alkali-catalyzed hydrolysis or alcoholysis or catalytic hydrogenolysis as required for the N-protecting group in use [see e.g. Montgomery et al., J. Med. Chem., 17 (1974) 1197].

The compound of formula (II) [wherein Z' is a group of formula OQ, and Q is an optionally substituted alkyl, aralkyl or aryl group] can be prepared from a 5-hydroxy compound of formula (VII) [wherein R is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl-carbonyl group and Z is a hydroxy group], by

(i) reaction with an alkyl or aralkyl halide in the presence of a base (e.g. methyl iodide and sodium hydride, or benzyl bromide and sodium hydride, in tetrahydrofuran as solvent); or

(ii) sequential conversion to a 5-O-sulfonate derivative (as above) and reaction with an alkali metal or tetraalkylammonium salt of the desired phenol, followed by selective N-deprotection by acid- or alkali-catalyzed hydrolysis or alcoholysis or catalytic hydrogenolysis as required for the N-protecting group in use.

It will be appreciated that the conversions above are conventional reactions employed in carbohydrate chemistry. Many alternative reagents and reaction conditions can be employed that will effect these conversions, and references to many of these can be found in the Specialist Periodical Reports "Carbohydrate Chemistry", Volumes 1-28, published by the Royal Society of Chemistry, particularly in the chapters on Halogeno-sugars, Amino-sugars, Thio-sugars, Esters, Deoxy-sugars, and Nucleosides.

Method (B): (2-amino-4-hydroxypyrrolo[3,2-d]pyrimidines)

reacting a compound of formula (V) [wherein Z' is as defined for formula (II) where first shown above, and R is an alkyl group] with benzoyl isothiocyanate then methyl iodide in the presence of a base (e.g. DBU or DBN) following the approach used to prepare 9-deazaguanosine and its derivatives [see e.g. Montgomery et al., J. Med. Chem., 36 (1993) 55, Lim et al., J. Org. Chem., 48 (1983) 780, and references therein] to give a compound of formula (VIII) ##STR12##

[wherein Z' is a trialkylsilyloxy, alkyldiarylsilyloxy or optionally substituted triarylmethoxy group, a hydrogen or halogen atom, SQ or OQ wherein Q is an optionally substituted alkyl, aralkyl or aryl group and R is an alkyl group] (typically Z', when a protected hydroxy group, is a tert-butyldimethylsilyloxy, trityloxy or similar group, and R is a methyl or ethyl group) which is then cyclized in the presence of ammonia to give a separable mixture of compounds of formula (IX) ##STR13##

[wherein D is an amino or methylthio group, and Z' and R are as defined for formula (VIII) where first shown above, or Z' is a hydroxy group] (where for example a tert-butyldimethylsilyloxy group has been cleaved under the reaction conditions) and the product of formula (IX) [wherein D is an amino or methylthio group] is fully deprotected under acidic conditions by the procedures set out in Method (A).

Method (C):(4-aminopyrrolo[3,2-d]pyrimidines)

reacting a compound of formula (IV) [wherein Z' is as defined for formula (II) where first shown above] with aminoacetonitrile under mildly basic conditions, cyclization of the product by reaction with a simple ester of chloroformic acid (typically benzyl chloroformate or methyl chloroformate) to give a compound of formula (X) ##STR14##

[wherein Z' is a trialkylsilyloxy, alkyldiarylsilyloxy or optionally substituted triarylmethoxy group, a hydrogen or halogen atom, SQ or OQ wherein Q is an optionally substituted alkyl, aralkyl or aryl group and R is an aralkyl or alkyl group] (typically Z', when a protected hydroxy group, is a tert-butyldimethylsilyloxy, trityloxy or similar group, and R is a benzyl or methyl group) which is then deprotected on the pyrrole nitrogen by hydrogenolysis in the presence of a noble metal catalyst (e.g. Pd/C) in the case of a benzyl group or under mildly basic conditions in the case of a simple alkyl group such as a methyl group, and processed as described above for the transformation (V).fwdarw.(VI).fwdarw.(I) or (V).fwdarw.(VIII).fwdarw.(IX).fwdarw.(I). This method follows the approach used to prepare 9-deazaadenosine and its analogues [Lim and Klein, Tetrahedron Lett., 22 (1981) 25, and Xiang et al., Nucleosides Nucleotides 15 (1996) 1821].

Method (D): (7-hydroxypyrazolo[4,3-d]pyrimidines--Daves' methodology)

reacting a compound of formula (II) [as defined where first shown above] sequentially with N-chlorosuccinimide and a hindered base (such as lithium tetramethylpiperidide) to form an imine, then condensing this with the anion produced by abstraction of the bromine or iodine atom from a compound of formula (XIb) or (XIc) ##STR15##

[wherein R.sup.3 is a bromine or iodine atom and R.sup.4 is a tetrahydropyran-2-yl group) typically using butyllithium or magnesium, to give a product which is then fully deprotected under acidic conditions (as in Method (A)). Methods for preparing compounds of formula (XIb) and (XIc) and mixtures thereof are described in Zhang and Daves, J. Org. Chem., 57 (1992) 4690, Stone et al., J. Org. Chem., 44 (1979) 505, and references therein.

It will be appreciated that while the tetrahydropyran-2-yl group is favoured as the protecting group for this reaction, other O,N-protecting groups can be used, and that this method will also be applicable to the synthesis of analogous pyrazolo[4,3-d]pyrimidines bearing substituents at position-5 and/or -7 of the pyrazolo[4,3-d]pyrimidine ring independently chosen from a hydroxy group, an amino, alkylamino, or aralkylamino group or a hydrogen atom using analogues of compounds of formula (XIb) and (XIc) in which the ionizable hydrogen atoms of any hydroxy or amino groups have been replaced by a suitable protecting groups.

Method (E): (7-hydroxypyrazolo[4,3-d]pyrimidines--Yokoyama method)

subjecting a 5-O-ether protected 2,3-O-isopropylidene-D-ribofuranose derivative, where the 5-ether substituent is typically a trialkylsilyl, alkyldiarylsilyl, an optionally substituted triarylmethyl or an optionally substituted aralkyl group, particularly a tert-butyldimethylsilyl, tert-butyldiphenylsilyl, triisopropylsilyl, trityl or benzyl group, to the following reaction sequence:

(i) condensation with the anion produced by abstraction of the bromine or iodine atom from a compound of formula (XIb) or (XIc) from Method (D);

(ii) oxidation of the resulting diol to a diketone, typically using a Swern oxidation or a variant thereof using a dimethylsulfoxide-based oxidant (e.g. using a dimethylsulfoxide and trifluoroacetic anhydride reagent combination in dichloromethane solution at low temperature, typically -78.degree. C., followed by triethylamine and warming to room temperature);

(iii) double reductive amination to form a 1,4-dideoxy-1,4-imino-D-ribitol moiety, typically with sodium cyanoborohydride and ammonium formate, ammonium acetate or benzhydrylamine in methanol; and

(iv) removal of the protecting groups by acid-catalyzed hydrolysis (e.g. with 70% aqueous trifluoroacetic acid) and if required (as in the case of the product made with benzhydrylamine or where an optionally substituted aralkyl group has been used for protecting the primary hydroxyl group in the iminoribitol moiety) hydrogenolysis over a metal catalyst (typically a palladium catalyst) or if desired (as in the case of silyl ether protecting group) exposure to a reagent capable of acting as a source of fluoride ion, e.g. tetrabutylammonium fluoride in tetrahydrofuran or ammonium fluoride in methanol). Conditions suitable for effecting this sequence of reactions are reported in Yokoyama et al., J. Org. Chem., 61 (1996) 6079, and conditions for double reductive amination with ammonium acetate or benzhydrylamine can be found in Furneaux et al., Tetrahedron 42 (1993) 9605 and references therein.

Method (F): (7-hydroxypyrazolo[4,3-d]pyrimidines--the Kalvoda method)

reacting a compound of formula (II) [as defined where first shown above] sequentially with N-chlorosuccinimide and a hindered base (such as lithium tetramethylpiperadide) to form an imine, then with a combination of trimethylsilyl cyanide and a Lewis acid (typically boron trifluoride diethyl etherate) followed by acid catalyzed hydrolysis to give a compound of formula (XII) ##STR16##

[wherein Z' is a hydrogen or halogen atom, a hydroxy group, or a group of formula SQ or OQ where Q is an optionally substituted alkyl, aralkyl or aryl group] which is then converted by sequential selective N-protection (typically with trifluoroacetic anhydride, di-tert-butyl dicarbonate, benzyl chloroformate, or methyl chloroformate and a base), and O-protection with an acyl chloride or anhydride and a base (typically acetic anhydride or benzoyl chloride in pyridine) to a suitably protected derivative of formula (XIII) ##STR17##

[wherein R.sup.1 is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl-carbonyl group, Z' is a hydrogen or a halogen atom, a group of formula SQ or OQ where Q is an optionally substituted alkyl, aralkyl or aryl group, or a group of formula R.sup.2 O, and R.sup.2 is an alkylcarbonyl or optionally substituted arylcarbonyl group] (typically R.sup.1 will be a trifluoroacetyl, tert-butoxycarbonyl or benzyloxycarbonyl group, and R.sup.2 will be an acetyl or benzoyl group).

The carboxylic acid moiety in the resulting compound of formula (XIII) is then transformed into a pyrazolo[4,3-d]pyrimidin-7-one-3-yl moiety following the method described by Kalvoda [Collect. Czech. Chem. Commun., 43 (1978) 1431], by the following sequence of reactions:

(i) chlorination of the carboxylic acid moiety to form an acyl chloride, typically with thionyl chloride with a catalytic amount of dimethylformamide in an inert solvent;

(ii) use of the resulting acyl chloride to acylate hydrogen cyanide in the presence of tert-butoxycarbonyltriphenylphosphorane (i.e. Ph.sub.3 P.dbd.CHCO.sub.2 Bu.sup.t) to give a 3-cyano-2-propenoate derivative;

(iii) cycloaddition of this with diazoacetonitrile (which can be prepared from aminoacetonitrile hydrochloride and sodium nitrite) with concomitant elimination of hydrogen cyanide to give a pyrazole derivative;

(iv) acid-catalyzed hydrolysis of the tert-butyl ester in this pyrazole derivative to its equivalent carboxylic acid;

(v) Curtius reaction, typically with phenylphosphoryl azide and 2,2,2-trichloroethanol in the presence of triethylamine, which converts the carboxylic acid moiety into a 2,2,2-trichloroethoxycarbonylamino group (i.e. the product is a carbamate);

(vi) reductive cleavage of this trichloroethyl carbamate, typically with zinc dust in methanol containing ammonium chloride;

(vii) condensation of the resulting ethyl 4-amino-3-substituted-1H-pyrazole-5-carboxylate with formamidine acetate to give a compound of formula (XIV) ##STR18##

[wherein R.sup.1 is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl-carbonyl group, Z' is a hydrogen or a halogen atom, SQ or OQ where Q is an optionally substituted alkyl, aralkyl or aryl group, or a group of formula R.sup.2 O, and R.sup.2 is an alkylcarbonyl or optionally substituted arylcarbonyl group, A is a nitrogen atom, B is a hydroxy group and D is a hydrogen atom] which is then--and O-deprotected by acid- or alkali-catalyzed hydrolysis or alcoholysis or catalytic hydrogenolysis as required for the O- and N-protecting groups in use.

Method (G): (7-aminopyrazolo[4,3-d]pyrimidines--the Buchanan method)

reacting a compound of formula (II) [as defined where first shown above] sequentially with N-chlorosuccinimide and a hindered base (such as lithium tetramethylpiperadide) to form an imine, which is then transformed into a 7-amino-pyrazolo[4,3-d]pyrimidine derivative following the approach used to prepare formycin and its analogues by Buchanan and co-workers [J. Chem. Soc., Perkin Trans. I (1991) 1077 and references therein], by the following sequence of reactions:

(i) addition of 3,3-diethoxyprop-1-ynylmagnesium bromide or 3,3-diethoxyprop-1-ynyllithium to the imine;

(ii) N-protection, typically with trifluoroacetic anhydride, di-tert-butyl dicarbonate, benzyl chloroformate, or methyl chloroformate and a base;

(iii) mild acid hydrolysis to remove the acid sensitive O-protecting groups and convert the diethyl acetal moiety into an aldehydic moiety;

(iv) condensation with hydrazine to convert the 3-substituted prop-2-ynal derivative into a 3-substituted pyrazole derivative;

(v) acylation, typically with acetic anhydride or benzoyl chloride in pyridine;

(vi) nitration, typically with ammonium nitrate, trifluoroacetic anhydride and trifluoroacetic acid, to produce an 3-substituted 1,4-dinitopyrazole derivative;

(vii) reaction with a reagent capable of delivering cyanide ion, typically sodium cyanide in aqueous ethanol to cause a cine-substitution of one of the two nitro-groups;

(viii) reduction of the residual nitro-group, typically with sodium dithionite or by catalytic hydrogenation over a metal catalyst;

(ix) condensation with formamidine acetate to give a compound of formula (XIV) [wherein R.sup.1 is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl-carbonyl group, Z' is a hydrogen or a halogen atom, SQ or OQ where Q is an optionally substituted alkyl, aralkyl or aryl group, or a group of formula R.sup.2 O wherein R.sup.2 is an alkylcarbonyl or optionally substituted arylcarbonyl group, A is a nitrogen atom, B is an amino group and D is a hydrogen atom] which is then--and O-deprotected by acid- or alkali-catalyzed hydrolysis or alcoholysis or catalytic hydrogenolysis as required for the O- and N-protecting groups in use.

Method (H): (2'-deoxy-analogues)

effecting the overall 2'-deoxygenation of a compound of formula (I) [wherein X and Z are hydroxy groups, Y is a hydrogen atom, and A, B and D are as defined where this formula is first shown above] through sequential:

(i) selective N-alkyl- or aralkyl-oxycarbonylation (typically with di-tert-butyl dicarbonate, benzyl chloroformate, or methyl chloroformate and a base) or N-acylation (typically with trilluoroacetic anhydride and a base) of the 1,4-dideoxy-1,4-iminoribitol moiety in such a compound of formula (I); and

(ii) 3',5'-O-protection of the resulting product by reaction with 1,3-dichloro-1,1,3,3-tetraisopropyldisiloxane and a base to give a compound of formula (XV): ##STR19##

[wherein R.sup.1 is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl-carbonyl group, R.sup.2 is either the same as R.sup.1 or is a hydrogen atom, and A, B and D are as defined for formula (I) where first shown above]

(iii) 2'-O-thioacylation of the resulting compound of formula (XV) (typically with phenoxythionocarbonyl chloride and a base; or sodium hydride, carbon disulfide and methyl iodide);

(iv) Barton radical deoxygenation (typically with tributyltin hydride and a radical initiator);

(v) cleavage of the silyl protecting group by a reagent capable of acting as a source of fluoride ion, e.g. tetrabutylammonium fluoride in tetrahydrofuran or ammonium fluoride in methanol; and

(vi) cleavage of the residual N- and O-protecting groups by acid- or alkali-catalyzed hydrolysis or alcoholysis or catalytic hydrogenolysis as required for the protecting groups in use.

Reagents and reaction conditions suitable for conducting the key steps in this transformation can be found in Robins et al., J. Am. Chem. Soc., 105 (1983) 4059; Solan and Rosowsky, Nucleosides Nucleotides 8 (1989) 1369; and Upadhya et al., Nucleic Acid Res., 14(1986) 1747.

It will be appreciated that a compound of formula (I) has a nitrogen atom in its pyrrole or pyrazole ring capable of undergoing alkyl- or aralkyl-oxycarbonylation or acylation during step (i), or thioacylation during step (ii), depending upon the reaction conditions employed. Should such derivatives be formed, the pyrrole or pyrazole N-substituents in the resulting derivatives are either sufficiently labile that they can be removed by mild acid- or alkali-catalyzed hydrolysis or alcoholysis, or do not interfere with the subsequent chemistry in the imino-ribitol moiety, and can be removed during the final deprotection step(s). If desired, this approach can be applied to a compound of formula (XV) [as defined above, but additionally bearing N-protecting groups on the pyrazolo- or pyrrolo-pyrimidine moiety]. Methods suitable for preparing such N-protected compounds can be found in Ciszewski et al., Nucleosides Nucleotides 12 (1993) 487; and Kambhampati et al., Nucleosides and Nucleotides 5 (1986) 539, as can methods to effect their 2'-deoxygenation, and conditions suitable for N-deprotection.

Method (I): (2'-epi-analogues)

effecting the overall C-2' epimerization of a compound of formula (I), by oxidizing and then reducing a compound of formula (XV) [as defined where first shown above] to give compound of formula (XVI): ##STR20##

[wherein R.sup.1, R.sup.2, A, B and D are as defined for formula (XV) where first shown above] which may be present in a mixture with the starting alcohol of formula (XV), and then fully deprotecting this compound of formula (XVI) as set out in steps (v) and (vi) of Method (H).

Reagents and reaction conditions suitable for conducting the key steps in this transformation can be found in Robins et al., Tetrahedron 53 (1997) 447.

Method (J): (2'-deoxy-2'-halogeno- and 2'-deoxy-2'-epi-2'-halogeno-analogues)

reacting compound of formula (XV) or (XVI) [as defined where first shown above] by the methods set out in Method (A) for the preparation of a compound of formula (II) [wherein Z' is a halogen atom] which involve either:

(i) 2'-O-sulfonylation and sulfonate displacement with a halide ion; or

(ii) direct replacement of the 2'-hydroxy group with a halogen atom, e.g by the Mitsunobu reaction or reaction with diethylaminosulfur trifluoride (DAST) to give a compound of inverted stereochemistry at C-2', which is then fully deprotected as set out in steps (v) and (vi) of Method (H).

It will be appreciated that a compound of formula (XV) or (XVI) has a nitrogen atom in its pyrrole or pyrazole ring capable of undergoing sulfonylation during step (i), depending upon the reaction conditions employed. Should such derivatives be formed, the pyrrole or pyrazole N-sulfonate substituents in the resulting derivatives are either sufficiently labile that they can be removed by mild acid- or alkali-catalyzed hydrolysis or alcoholysis, or do not interfere with the subsequent chemistry in the iminoribitol moiety, and can be removed during the final deprotection step(s).

If desired, this approach can be applied to a compound of formula (XV) or (XVI) [as defined above, but additionally bearing N-protecting groups on the pyrazolo- or pyrrolo-pyrimidine moiety). Methods suitable for preparing such N-protected compounds can be found in Ciszewski et al., Nucleosides Nucleotides 12 (1993) 487; and Kambhampati et al., Nucleosides and Nucleotides 5 (1986) 539, as can methods to effect 2'-O-triflate formation and displacement by halide ion with inversion, and conditions suitable for N-deprotection.

Method (K): (5'S -deoxy-, 5'-deoxy-5'-halogeno-, 5'-ether and 5'-thio-analogues)

by applying the procedures described in Method (A) for converting a compound of formula (VII) [wherein R is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl-carbonyl group and Z' is a hydroxy group] into a compound of formula (II) [wherein Z' is a halogen or hydrogen atom or SQ or OQ where Q is an optionally substituted alkyl, aralkyl or aryl group alkylthio group of one to five carbon atoms] to a compound of formula (XVII): ##STR21##

[wherein R is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl-carbonyl group, Z' is a hydroxy group, and A, B and D are as defined for formula (I) where first shown above] which is then fully deprotected under acidic conditions, e.g. by treatment with aqueous trifluoroacetic acid.

Such a compound of formula (XVII) can be prepared from a compound of formula (I) [wherein X and Z are both hydroxy groups, Y is a hydrogen atom and A, B, and D have the meanings defined for formula (I) where first shown above] in the following two reaction steps, which may be applied in either order:

(i) selective N-alkyl- or aralkyl-oxycarbonylation (typically with di-tert-butyl dicarbonate, benzyl chloroformate, or methyl chloroformate and a base) or N-acylation (typically with trifluoroacetic anhydride and a base) of the 1,4-dideoxy-1,4-iminoribitol moiety; and

(ii) 2',3'-O-isopropylidenation, which may be effected with a variety of reagents, e.g. acetone and anhydrous copper sulfate with or without added sulfuric acid; acetone and sulfuric acid; 2,2-dimethoxypropane and an acid catalyst; or 2-methoxypropene and an acid catalyst.

It will be appreciated that such a compound of formula (I) or formula (XVII) has a nitrogen atom in its pyrrole or pyrazole ring capable of undergoing sulfonylation, thioacylation, acylation or aralkyl-oxycarbonylation, depending upon the reaction conditions employed. Should such derivatives be formed, the pyrrole or pyrazole N-substituents in the resulting derivatives are either sufficiently labile that they can be removed by mild acid- or alkali-catalyzed hydrolysis or alcoholysis, or do not interfere with the subsequent chemistry in the iminoribitol moiety, and can be removed during the final deprotection step(s).

Method (L): (2- and 4-aminopyrrolo[3,2-d]pyrimidine and 5- and 7-aminopyrazolo[4,3-d]pyrimidine analogues)

chlorinating a compound of formula (XVIII) ##STR22##

[wherein R.sup.1 is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl-carbonyl group, R.sup.2 is an alkylcarbonyl or optionally substituted arylcarbonyl group, X and Y are independently chosen from a hydrogen or halogen atom, or a group of formula R.sup.2 O, except that when one of X or Y is a halogen atom or a group of formula R.sup.2 O, the other is a hydrogen atom, Z' is a group of formula R.sup.2 O or, when X is a group of formula R.sup.2 O, Z' is a hydrogen or halogen atom, a group of formula R.sup.2 O or of formula OQ or SQ wherein Q is an optionally substituted alkyl, aralkyl or an aryl group, A is a nitrogen atom or a methine group, and one of B or D is a hydroxy group, and the other is a chlorine, bromine or hydrogen atom] with a chlorinating reagent, and then displacing the chlorine atom with a nitrogen nucleophile by one of the following methods:

(i) ammoniolysis, typically using liquid ammonia, concentrated aqueous ammonia, or a solution of ammonia in an alcohol such as methanol; or

(ii) conversion first to a triazole derivative, by addition of 4-chlorophenyl phosphorodichloridate to a solution of the chloride and 1,2,4-triazole in pyridine, and alkaline hydrolysis of both the tetrazole moiety and the ester protecting groups with ammonium hydroxide;

(iii) reaction with a source of azide ion, e.g. an alkali metal azide or tetraalkylammonium azide, and reduction of the resulting product, typically by catalytic hydrogenation; or

(iv) reaction with an alkylamine or aralkylamine, such as methylamine or benzylamine in methanol.

These conditions are sufficiently basic that O-ester groups will generally be cleaved but any residual O- or N-protecting groups can then be removed by acid- or alkali-catalyzed hydrolysis or alcoholysis or catalytic hydrogenolysis as required for the protecting groups in use.

Suitable chlorinating agents are thionyl chloride-dimethylformamide complex [Ikehara and Uno, Chem. Pharm. Bull., 13 (1965) 221], triphenylphosphine in carbon tetrachloride and dichloromethane with or without added 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) [De Napoli et al., J. Chem. Soc., Perkin Trans.1 (1995) 15 and references therein], phosphoryl chloride [Imai, Chem. Pharm. Bull., 12 (1964) 1030], or phenylphosphoryl chloride and sodium hydride.

Suitable conditions for such an ammoniolysis or a reaction with an alkylamine can be found in Ikehara and Uno, Chem. Pharm. Bull., 13 (1965) 221; Robins and Tripp, Biochemistry 12 (1973) 2179; Marumoto et al., Chem. Pharm. Bull., 23 (1975) 759; and Hutchinson et al., J. Med. Chem., 33 (1990) 1919].

Suitable conditions for conversion of a such a chloride to an amine via a tetrazole derivative can be found in Lin et al., Tetrahedron 51 (1995) 1055.

Suitable conditions for reaction with azide ion followed by reduction can be found in Marumoto et al., Chem. Pharm. Bull., 23 (1975) 759.

Such a compound of formula (XVIII) can be prepared from a compound of formula (I) by selective N-alky- or aralkyl-oxycarbonylation (typically with di-tert-butyl dicarbonate, benzyl chloroformate, or methyl chloroformate and a base) or N-acylation of the 1,4-dideoxy-1,4-iminoribitol moiety and then O-acylation (typically with acetic anhydride or benzoyl chloride in pyridine). It will be appreciated that such a compound of formula (I) has a nitrogen atom in its pyrrole or pyrazole ring capable of undergoing alkyl- or aralkyl-oxycarbonylation or acylation depending upon the reaction conditions employed. Should such derivatives be formed, the pyrrole or pyrazole N-substituents in the resulting derivatives are either sufficiently labile that they can be removed by mild acid- or alkali-catalyzed hydrolysis or alcoholysis, or do not interfere with the subsequent chemistry, and can be removed during the final deprotection step(s).

The above chlorination--amination--deprotection sequence can also be applied to a compound of formula (XVII) [wherein B is a hydroxy group, D is a hydrogen atom, Z' is a hydrogen or halogen atom, or a group of formula R.sup.2 O, R.sup.2 is a trialkylsilyloxy or alkyldibrylsilyloxy group, or an optionally substituted triarylmethoxy, alkylcarbonyl or arylcarbonyl group, R and A are as defined for formula (XVII) where first shown above]. Suitable conditions for conducting this reaction sequence can be found in Ikehara et al., Chem. Pharm. Bull., 12 (1964) 267.

Method (M): (2,4-dihydroxypyrrolo[3,2-d]pyrimidine and 5,7-dihydroxypyrazolo[4,3-d]pyrimidine analogues)

oxidation of either:

(i) a compound of formula (XVIII) [wherein R.sup.2 is a hydrogen atom; X and Y are independently chosen from a hydrogen or halogen atom, or a hydroxy group, except that when one of X or Y is a halogen atom or a hydroxy group, the other is a hydrogen atom; Z' is a hydroxy group or, when X is a hydroxy group, Z' is a hydrogen or halogen atom, a hydroxy group, or OQ; Q is an optionally substituted alkyl, aralkyl or aryl group; B is a hydroxy group or an amino group; D is a hydrogen atom; and R.sup.1 and A are as defined for formula (XVIII) where first shown above] with bromine in water; or

(ii) a compound of formula (XVIII) [wherein Z' is a hydrogen or a halogen atom, or a group of formula R.sup.2 O, or OQ; Q is an optionally substituted alkyl, aralkyl or aryl group; B is a hydroxy group or an amino group, D is a hydrogen atom and R.sup.1, R.sup.2, X, Y and A are as defined for formula (XVIII) where first shown above], with bromine or potassium permanganate in water or in an aqueous solvent mixture containing an inert, water-miscible solvent to improve the solubility of the substrate, to give a related compound of formula (XVIII) [but wherein B and D are now hydroxy groups], and then removal of any O- and N-protecting groups by acid- or alkali-catalyzed hydrolysis or alcoholysis or catalytic hydrogenolysis as required for the protecting groups in use.

Such a compound of formula (XVIII) required for step (i) above can be prepared from a compound of formula (I) [wherein Z is Z', and X, Y, Z, A, B and D are as defined for the required compound of formula (XVIII)] by selective N-alkyl- or aralkyl-oxycarbonylation (typically with di-tert-butyl dicarbonate, benzyl chloroformate, or methyl chloroformate and a base) or N-acylation (typically with trifluoroacetic anhydride and a base) of the 1,4-dideoxy-1,4-iminoribitol moiety. This can then be converted to the corresponding compound of formula (XVIII) required for step (ii) above by O-acylation (typically with acetic anhydride or benzoyl chloride in pyridine). It will be appreciated that such a compound of formula (I) has a nitrogen atom in its pyrrole or pyrazole ring capable of undergoing alkyl- or aralkyl-oxycarbonylation or acylation depending upon the reaction conditions employed. Should such derivatives be formed, the pyrrole or pyrazole N-substituents in the resulting derivatives are either sufficiently labile that they can be removed by mild acid- or alkali-catalyzed hydrolysis or alcoholysis, or do not interfere with the subsequent chemistry, and can be removed during the final deprotection step(s).

Method (N): (4-amino-2-chloropyrrolo[3,2-d]pyrimidine and 7-amino-5-chloropyrazolo[4,3-d]pyrimidine analogues)

chlorinating a compound of formula (XVIII) [wherein B and D are hydroxy groups and R.sup.1, R.sup.2, X, Y, Z' and A are as defined for formula (XVIII) where first shown above] to give a corresponding dichloro-derivative of formula (XVIII) [wherein B and D are chlorine atoms], typically with neat phosphorous oxychloride, and then displacing the more reactive chloro-substituent selectively by ammoniolysis, typically using anhydrous liquid ammonia in a pressure bomb or methanolic ammonia, which simultaneously cleaves the O-ester protecting groups. The residual N-protecting group is then removed by acid-catalyzed hydrolysis or alcoholysis or catalytic hydrogenolysis as required for the protecting groups in use, to give a compound of formula (I) [wherein B is an amino-group and D is a chlorine atom].

The above dichloro-derivative of formula (XVIII) can be converted into a compound of formula (I) [wherein B and D are chlorine atoms] by removal of the O- and N-protecting groups by acid- or alkali-catalyzed hydrolysis or alcoholysis as required for the protecting groups in use. It will be appreciated that one of the chlorine atoms in the aforementioned compound of formula (XVII) or of formula (I) is quite reactive and that conditions chosen for deprotection must be mild enough that they limit unwanted reactions involving this atom.

Suitable reaction conditions for the key steps in this method can be found in Upadhya et al., Nucleic Acid Res., 14 (1986) 1747 and Kitagawa et al., J. Med. Chem., 16 (1973) 1381.

Method (O): (2-chloro-4-hydroxypyrrolo[3,2-d]pyrimidine and 5-chloro-7-hydroxypyrazolo[4,3-d]pyrimidine analogues from dichloro-compounds)

hydrolysis of a compound of formula (XVIII) [wherein B and D are chlorine atoms] available as an intermediate from the first reaction of Method (N), typically with aqueous potassium hydroxide or sodium carbonate, in the presence of an inert, water-miscible solvent such as dioxane to enhance solubility as required, followed by removal of the residual N-protecting group by acid-catalyzed hydrolysis or alcoholysis or catalytic hydrogenolysis as required for the protecting groups in use, to give a compound of formula (I) [wherein B is a hydroxy group and D is a chlorine atom].

Method (P): (2-chloro-4-hydroxypyrrolo[3,2-d]pyrimidine and 5-chloro-7-hydroxypyrazolo[4,3-d]pyrimidine analogues from aminochloro-compounds)

deamination of a compound of formula (XVIII) [wherein B is an amino group, D is a chlorine atom, R.sup.1 is an alkyl- or aralkyl-oxycarbonyl group or an optionally substituted alkyl- or aryl-carbonyl group, R.sup.2 is a hydrogen atom, Z'.dbd.Z and X, Y, Z and A are as defined for formula (I) where first shown above], available as an intermediate following the chlorination and ammonyolysis reactions of Method (N), by reaction with nitrosyl chloride, followed by removal of the protecting groups as set out in Method (N). Typical reaction conditions can be found in Sanghvi et al., Nucleosides Nucleotides 10 (1991) 1417.

Method (Q): (4-halogenopyrrolo[3,2-d]pyrimidine and 7-halogenopyrazolo[4,3-d]pyrimidine analogues)

reacting a compound of formula (XVIII) [wherein R.sup.1 is tert-butoxycarbonyl group, B is a hydroxy group, D is a hydrogen atom and R.sup.2, X, Y, Z' and A are as defined for formula (XVIII) where first shown above] by a method used to prepare halogeno-formycin analogues [Watanabe et al., J. Antibiotic, Ser. A 19 (1966) 93] which involves sequential treatment with:

(i) phosphorous pentasulfide by heating in pyridine and water under reflux to give a mercapto-derivative;

(ii) methyl iodide to give a methylthio-derivative;

(iii) a base in a simple alcohol or an aqueous solution of a simple alcohol, e.g. sodium methoxide in methanol, to remove the O-protecting groups; and

(iv) chlorine, bromine or iodine in absolute methanol to give a halogeno-derivative which is then N-deprotected by reaction with aqueous acid, typically a concentrated trifluoroacetic acid solution.

Method (R): (pyrrolo[3,2-d]pyrimidine and pyrazolo[4,3-d]pyrimidine analogues)

hydrogenolytic cleavage of the chloride intermediate resulting from the chlorination reaction used as the first reaction in Method (L), or the chloride intermediate resulting from the chlorination reaction step (iv) in Method (Q), or the compound of formula (I) produced by Method (Q), typically using hydrogen over palladium on charcoal as the catalyst, optionally with magnesium oxide present to neutralize released acid, followed by cleavage of any residual O- or N-protecting groups by acid- or alkali-catalyzed hydrolysis or alcoholysis as required for the protecting groups in use.

Method (S): (N-alkylated 4-aminopyrrolo[3,2-d]pyrimidine and 7-aminopyrazolo[4,3-d]pyrimidine analogues)

heating an O-deprotected methylthio-derivative produced by step (iii) of Method (Q) with an amine, e.g. methylamine, in absolute methanol in a sealed tube or bomb, and then removing the N-protecting group by reaction with aqueous acid, typically a concentrated trifluoroacetic acid solution. This method has been used to prepare N-alkylated-formycin analogues [Watanabe et al., J. Antibiotic, Ser. A 19 (1966) 93]; or reacting a compound of formula (I) [wherein either B or D is an amino group] with 1,2-bis[(dimethylamino)methylene]hydrazine and trimethylsilyl chloride in toluene to convert the amino group into a 1,3,4-triazole group, hydrolysis to cl