The silylated AzddThd 5 and AzddUrd 6 prepared from 2, 3'-anhydronucleoside derivatives 3 and 4 were transformed to formamides 7 and 8 by using the sequence RN3-RN= P (C6H5)- RNHCHO. Formamides 7 and 8 were dehydrated to the protected 3'4socyano derivatives 9 and 10; deblocking gave 11 and 12. Neither 3'4socyano-3'-deoxythymidine (1 1) nor 3'- isocyano-2', 3'-dideoxyuridine (12) showed anti-HIV activity at noncytotoxic concentrations ...