CONFORMATIONAL AND ORIENTATIONAL SWITCHING OF URIDINE DERIVATIVES BY BORATES

We have demonstrated for the first time that the syn-anti orientation of 5'-amino-5'-deoxyuridine (Ib) can readily be switched by adding ber ate as an external controlling factor. In berate added phosphate buffe r, the synlanti ratio of Ib dramatically increased with increasing ber ate concentration This unique syn preference is most probably driven b y the cooperative action of cyclic esterification of the Ib's 2',3'-ci s-diol with berate and of hydrogen-bonding formation between 2-carbony l oxygen and 5'-amino proton.