Synthesis of N-homobicyclic dideoxynucleoside analogues

Syntheses of six N-homobicyclic dideoxynucleoside analogues are described. The reaction of mannose diacetonide with trimethylsulfoxonium iodide gave a mixture of diastereomeric hydroxymethyl mannose diacetonides in a ratio of 2:5, which was separated by fractional crystallization. The two stereoisomers were converted to bicyclic furanolactols each of which was coupled with three nucleoside bases. Further debenzylations gave the six target N-homobicyclic dideoxynucleosides.