THE SYNTHESIS OF SOME 5-SUBSTITUTED-6-AZA-2'-DEOXYURIDINES

toluoyl-beta-D-erythro-pentofuranosyl)-6-azauracil VIII and toluoyl- beta-D-erythro-pentofuranosyl)-6-azauracil X were obtained in high y ields (93.5% and 81.3% respectively) exclusively as beta anomers, by c ondensation of the corresponding silylated triazine bases with 2-deoxy -3,5-di-O-p-toluoyl-D-erythro-pentosyl chloride in chloroform. After d eblocking both nucleosides with sodium methoxide in methanol, 5-(2-thi enyl)-6-aza-2'-deoxyuridine IX and 5-cyclopropyl-6-aza-2'-deoxyuridi ne XI were obtained. The nucleoside IX was further acetylated, bromi nated with Br-2/CCl4 and deblocked with methanolic ammonia to give 6-a za-52-(5-bromothienyl)-2'-deoxyuridine XIV.