Abstract Stereoselectivities in the coupling reaction between 1-O-methyl-3, 5-di-Op-toluoyl-2- deoxyribofuranoside and suitably protected purine and pyrimidine derivatives have been examined in acetonitrile with varying equivalents of SnCl 4. The best result in α-nucleoside formation was obtained when the coupling reaction was carried out in the presence of ten equivalents of SnCl 4.
