The synthesis of optically pure unsaturated carbocyclic nucleoside ana
logues is described. (3,4S)-Bis(t-butyldiphenyl silyloxymethyl)-1R and
1S cyclopent-2-en-1-ol were coupled with 6-chloropurine and 2-amino-6
-chloropurine respectively, using a modified Mitsunobu reaction. The p
roducts were reacted further using standard procedures to give compoun
ds 12, 14, 16 and 18.