Synthesis of cyclic silyl nucleosides having bulky groups on the silicon atom

Synthesis of cyclic silyl nucleosides having bulky tert-butyl groups on the silicon atom has been investigated. Cyclic silyl deoxyribonucleosides having one tert-butyl group on the silicon atom was obtained without difficulty in the standard silylation reaction using dichlorosilane and imidazole. However, under similar conditions the reaction with di-tert-butyldichloro-silane proceeded only slowly by virtue of steric hindrance. The reaction has been largely improved by the use of 1-hydroxy-benzotriazole as a catalyst for silyl transfer and silver salts of acids to generate silylating reagents of high reactivity.