Studies on Nucleosides and Nucleotides, VII. Preparation of Pyrimidine Nucleoside 5′-Phosphates and N3,5′-Purine Cyclonucleosides by Selective Activation of the 5′-Hydroxyl Group

The reaction of thymidine or uridine with 1.5 molar equivalents each of dibenzyl hydrogenphosphate, diethyl azodicarboxylate, and triphenylphosphine in HMPT at room temperature for 1 day, followed by debenzylation, afforded dpT and pU in 73 and 78% yields, respectively. Neither nucleoside 3′-phosphate nor 3′,5′-diphosphate was formed. 5′-O-Benzoyl thymidine 3′-(2-cyanoethyl)phosphate also reacted smoothly with thymidine at room temperature giving d-bzT3′p(CNEt)5′T in a 54% yield. Adenosine and Guanosine gave the corresponding N3,5′-cyclonucleosides as main products, less than 1% pA and pG being formed.