Stereoselective method for the preparation of nucleoside analogues

Abstract From the Canadian patent

A process for producing predominantly cis nucleosides or nucleoside analogues and derivatives of formula (A): wherein R1 is a pyrimidine base or a pharmaceutically acceptable derivative thereof and Q is oxygen carbon or , sulphur, comprising a coupling step of the pyrimidine base with a molecule of formula (B) described herein in a suitable coupling solvent in the presence , of catalytic amounts of an element or combination of elements of groups 1B or 11B of the periodic table, a tertiary amine and a Lewis acid to obtained an intermediate of formula (D) which is deprotected in the subsequent step to generate the product of formula (A).