The synthesis of nucleosides derived from 5-ethynyluracil and 5-ethynylcytosine

Abstract

5-Ethynyluridine and 2′-deoxy-5-ethynyluridine have been synthesised by condensation of the trimethylsilyl derivative of 5-ethynyluracil with the appropriate blocked sugar derivatives and removal of the blocking groups. The α-anomer of 2′-deoxy-5-ethynyluridine was also obtained. 2,4-Dichloro-5-(1-chlorovinyl)pyrimidine upon treatment with ammonia gave a mixture of 2-amino-4-chloro-5-(1-chlorovinyl)pyrimidine and 4-amino-2-chloro-5-(1-chlorovinyl)pyrimidine. The latter upon treatment with potassium hydroxide in aqueous dioxan gave 5-ethynylcytosine. Condensation of the trimethylsilyl derivative of 5-ethynylcytosine with appropriate protected sugar derivatives and removal of the protecting groups gave 5-ethynylcytidine, 2′-deoxy-5-ethynylcytidine, and its α-anomer.