A Facile Synthesis of 6-Aryl-5-cyano-2-(#beta#-D-pyranosyl or #beta#-D-furanosyl)-2-thiocytosines

摘要

The treatment of a piperidinium salt of 6-aryl-5-cyano-2-thiouracil with an O-peracetyl-#alpha#-D-pyranosyl bromide produces a mixture of N1-(#beta#-D-pyranosyl)-2-thiouracil and its N1,S~2-disubstituted analog.By contrast,the reaction of a silyl derivative of the 2-thiouracil with an O-peraceyl-#beta#-D-pyranose furnishes the mononucleoside selectively.Both the mononucleoside/dinucleoside mixture and pure mononucleoside undergo ammonolysis under mid conditions to give the #beta#-D-nucleoside of 6-aryl-5-cyano-2-thiocytosine.The silyl method also provides an easy access to #beta#-D-ribosyl nucleosides.