| abstract |
The present invention relates to a process for producing predominantly pure cis nucleoside analogues of formula (I), wherein X is S, or O; Y is S, CH 2 , O or CH(R); wherein R is azido or halogen; and R 2 is a purine or pyrimidine base; via the coupling of a silylated purine or pyrimidine base in the presence of an appropriate Lewis acid with a bicyclic intermediate of formula (III) wherein Z is S or O; followed by conversion of the resulting intermediate of formula (II) to an alkyl ester and reduction to yield a compound of formula (I). ##STR1## |