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Synthesis An allopurinol locked nucleic acid (LNA) monomer was prepared by a novel strategy through C6 deamination of the corresponding 8-aza-7-bromo-7- deazaadenine LNA monomer with aqueous sodium hydroxide. An 8-aza-7-deazaadenine LNA monomer was also synthesized by a modification of the new synthetic pathway. N-Glycosylation at the 8-position was prevented by steric hindrance from the 7-bromo atom in the starting material 8-aza-7-bromo-7-deazaadenine. In the final step of the synthesis, the bromine was removed together with a benzyl protecting group by catalytic reduction with ammonium formate to give the required LNA monomers.

Methyl 2,3-dideoxy-3-fluoro-5-0-(4-phenylbenzoyl)-β-D-erythro-pentofuranoside was condensed with trimethylsilylated 5-substituted uracils to give nucleosides using trimethylsilyl trifluoromethanesulfonate as catalyst. In the case of 5-nitrouracil an acyclic nucleoside believed to be an intermediate for the corresponding nucleoside was isolated. The 5-substituents were selected from neural network calculations on compounds with potential activity against HIV-1. All compounds from the condensation reactions were deacylated by treatment with sodium methoxide in methanol

Convergent syntheses, in which a synthetic 2,3-dideoxy-furanose intermediate is condensed with a synthetic base with the aim of producing 2'-substituted-, 3'-substituted- or unsubstituted-2',3'dideoxy nucleosides-potential HIV inhibitors - are reviewed. It is demonstrated that this approach provides a potential for structural variations, including unnatural configurations, otherwise unattainable. Starting from both carbohydrate and noncarbohydrate precursors synthetic routes to the carbohydrate moiety are emphasized and syntheses of related compounds considered

Reaction of methyl 2-bromo-2,3-dideoxy-5-O-(4-methylbenzoyl)-D-erythro-pentofuranoside (7)with silylated uracils using trimethylsilyl triflate as catalyst afforded the corresponding 2'-bromonucleosides(10). 2,3-Didehydro sugar was prepared by heating 7 with sodium azide in dimethylformamide. 2,2'-Anhydronucleosides were prepared by treating the nucleosides 10 with sodium methoxide at room temperature. 1-(2-Azido-2,3-dideoxy-β-D-threo-pentofuranosyl)thymine (15) and its α-anomer (16) were prepared by treating 10 with sodium azide and subsequently methanolic ammonia

α,β-Unsaturated aldehyde prepared from tri-O-acetyl-D-glucal was acetalated and benzoylated to give α,β-unsaturated acetal . Hydrogenation of the double bond followed by methanolysis resulted in methyl 2,3-dideoxyfuranosyl glycoside which was used for nucleoside coupling with silylated N 6 -isobutyrylcytosine and silylated thymine. Protected 3-azido-2,3-dideoxy-arabino-furanose was prepared by 1,4-addition of hydrazoic acid to disilylated α,β-unsaturated aldehyde followed by acetylation

5-O-Acetyl-2,3,6-trideoxy-3-phthalimido-β-L-ribo-hexofuranose (2) was converted to its corresponding methyl glycoside 3. After deprotection with 33% methylamine in ethanol and subsequent protection of the amino group with trifluoroacetic anhydride and the hydroxy group with 4-nitrobenzoyl chloride, the resulting compound 5 was transformed into the appropriate glycosyl bromide 7 via the 1-O-acetyl derivative 6. Compound 7 was coupled with daunomycinone in the presence of yellow mercury(II) oxide and mercury(II) bromide