Synthesis of acylic derivatives of prolylleucylglycinamide

Tert-butyloxycarbonylprolylleucylglycinamide is obtained both by the interaction of tert-butyloxycarbonylprol ylleucylglycine ethyl ester with a methanolic ammonia solution and by the reaction of glycine amide with a mixed anhydride which was synthesized from tert-butyloxycarbonylprolylleucine and isobutylchloroformate. The removal of the tert-butyloxycarbonyl group by the action of formic acid or a dioxane solution of hydrogen chloride and treatment of the resulting salts with the corresponding base yielded a prolylleucylglycinamide, by the interaction of which with acetic, benzoic or 5-phenylisoxazole-3-carboxylic acids chlorides acyl derivatives of prolylleucylglycinamide are obtained.

Synthesis of 8-Amino- and N-Substituted 8-Aminoadenine Derivatives of Acyclic Nucleoside and Nucleotide Analogs

8-Aminoadenine derivatives 2 were obtained from 8-bromoadenines 1 in one-pot reaction via 8-azidoadenines. Reaction of 8-bromoadenines 1 with methylamine or dimethylamine in ethanol afforded the corresponding N9-substituted 8-(methylamino)adenines 3 and 8-(dimethylamino)adenines 4. Alkylation of 8-aminoadenine (2a) with diverse alkylation agents afforded N9-substituted 8-aminoadenine derivatives 2, and alkylation of 8-(dimethylamino)adenine (4a) gave mixtures of the corresponding N9-substituted 8-(dimethylamino)adenines 4 and their N3-substituted regioisomers 5. 8,3'-N-Anhydro derivatives 7 were prepared by tosylation of (S)-8-bromo-9-{2-[(diisopropoxyphosphoryl)- methoxy]-3-hydroxypropyl}adenine (1c) followed by treatment with methanolic ammonia or methylamine solution.

Synthesis of 5-Phenyl-2(1H)-pyrimidinone Nucleosides

Reaction of 2-phenyltrimethinium salt 1 with thiourea and subsequent reaction with chloroacetic acid afforded 5-phenyl-2(1H)-pyrimidinone (3). Its silyl derivative 4 was condensed with 1-O-acetyl-2,3,5-tri-O-benzoyl-D-ribofuranose under catalysis with tin tetrachloride or trimethylsilyl trifluoromethanesulfonate to give protected nucleoside 5 together with 5',O6-cyclo-5-phenyl-1,3-bis- (β-D-ribofuranosyl)-6-hydroxy-5,6-dihydro-2(1H,3H)-pyrimidinone (7). The greatest amounts of 7 were formed with the latter catalyst. Nucleosidation of the silyl derivative 4 with protected methyl 2-deoxy-D-ribofuranoside 8 or 2-deoxy-D-ribofuranosyl chloride 9 afforded 1-(2-deoxy-3,5-di-O-p-toluoyl-β-D-ribofuranosyl)-5-phenyl-2(1H)-pyrimidinone (10) and its α-anomer 11. Reaction of 10 and 11 with methanolic ammonia gave free 2'-deoxynucleosides 12 and 13. Compound 13 was converted into 5'-O-tert-butyldiphenylsilyl-3'-O-mesyl derivative 14 which on heating with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and subsequent cleavage with tetrabutylammonium fluoride afforded 2',3'-dideoxy-2',3'-didehydronucleoside 15. Reaction of the silyl derivative 4 with 1,2-di-O-acetyl-3,5-di-O-benzoylxylofuranose (18), catalyzed with tin tetrachloride, furnished 1-(2-O-acetyl-3,5-di-O-benzoyl-β-D-xylofuranosyl)-2(1H)-pyrimidinone (19) which was deprotected to give the β-D-xylofuranosyl derivative 22. As a side product, the nucleosidation afforded the β-D-xylopyranosyl derivative 23. Deacetylation of compound 19 gave 1-(3,5-di-O-benzoyl-β-D-xylofuranosyl)-5-phenyl-2(1H)-pyrimidinone (24) which on reaction with thionyl chloride afforded 2'-chloro-2'-deoxynucleoside 25 and 2',O6-cyclonucleoside 26. Heating of compound 25 with DBU in dimethylformamide furnished the lyxo-epoxide 27 which on reaction with methanolic ammonia was converted into free 1-(2,3-anhydro-β-D-lyxofuranosyl)-5-phenyl-2(1H)-pyrimidinone (28). Reaction of 1,2-di-O-acetyl-5-O-benzoyl-3-O-methanesulfonyl-D-xylofuranose (30) with silyl derivative 4 gave the nucleoside 31 which by treatment with DBU was converted into an equilibrium mixture of 5'-benzoylated arabinofuranoside 33a and its 2',6-anhydro derivative 33b.

Synthesis of Deoxy, Dideoxy and Didehydrodideoxy Analogs of 9-(β-D-Hexofuranosyl)adenine

Condensation of 1,2-di-O-acetyl-3,5,6-tri-O-benzoyl-D-glucofuranose with N6-benzoyladenine, catalyzed with tin tetrachloride, afforded nucleoside I. Partial deacetylation of I, followed by mesylation, gave 9-(3,5,6-tri-O-benzoyl-2-O-methanesulfonyl-β-D-glucofuranosyl)adenine (III). 9-(2,5,6-Tri-O-acetyl-3-O-methanesulfonyl-β-D-glucofuranosyl)-N6-benzoyladenine (IV) was prepared by condensation of 1,2,5,6-tetra-O-acetyl-3-O-methanesulfonyl-D-glucofuranose with N6-benzoyladenine. Reaction of mesyl derivative III with methanolic sodium methoxide and of mesyl derivative IV with methanolic ammonia led to 2',3'-anhydronucleosides V and VI which were acetylated to give the respective 9-(5,6-di-O-acetyl-2,3-anhydro-β-D-mannofuranosyl)adenine (VII) and 9-(5,6-di-O-acetyl-2,3-anhydro-β-D-allofuranosyl)adenine (VIII). Epoxy derivative VII was cleaved with bromotrimethylsilane, affording a mixture of 9-(5,6-di-O-acetyl-2-bromo-2-deoxy-β-D-glucofuranosyl)adenine (Xa) and 9-(5,6-di-O-acetyl-3-bromo-3-deoxy-β-D-altrofuranosyl)adenine (XIa), epoxy derivative VIII was cleaved analogously to give 9-(5,6-di-O-acetyl-3-bromo-3-deoxy-β-D-glucofuranosyl)adenine (XIIa). Their dehalogenation with tributylstannane and subsequent deacetylation led to 9-(2-deoxy-β-D-arabino-hexofuranosyl)adenine (Xc), 9-(3-deoxy-β-D-arabino-hexofuranosyl)adenine (XIc) and 9-(3-deoxy-β-D-ribo-hexofuranosyl)adenine (XIIc). 9-(2,5,6-Tri-O-acetyl-3-bromo-3-deoxy-β-D-glucofuranosyl)adenine (XIId), which was prepared by acetylation of XIIa, on reductive elimination with Cu/Zn couple and subsequent deacetylation gave 9-(2,3-dideoxy-β-D-erythro-hex-2-enofuranosyl)adenine (XIV). 9-(2,3-Dideoxy-β-D-erythro-hexofuranosyl)adenine (XVI) was obtained either by catalytic hydrogenation of bromo derivative XIId followed by deacetylation, or by catalytic hydrogenation of didehydro derivative XIV. The synthesized nucleosides were tested for antiviral activity.