NOVEL DIASTEREOMERIC THYMIDINE CYCLIC 3',5'-THREO-PHOSPHORAMIDATES

Novel diastereomeric thymidine cyclic 3',5'-threo-phosphoramidates wer e prepared by the treatment of 5'-azido derivative of threo-thymidine with triphenyl phosphite as well as by the treatment of the correspond ing amino derivative with phenyl phosphodichloridate. Phosphoramidatio n of the regioisomeric 3'- and 5'-azido derivatives of erythro-thymidi ne by means of triphenyl phosphite afforded the open-chain 3'- and 5'- phosphoramidates. The reaction which afforded the cyclic products was assumed to proceed via the cyclic tetraoxazaphosphorane intermediates.