Reaction of 2'5'-dichloro-2'5'-dideoxyuridine with nucleophiles

Reaction of 2',5'-dichlorouridine (1) with amines and thiols afforded 2-N-substituted 2',5'-anhydroisocytidine derivatives (2) and 2,2'-anhydro-5'-thiouridine derivatives (5), respectively. When 2,2'-anhydro-5'-acetylthiouridine (5a) was treated with NaOMe, 3',5'-S-cyclouridine (6) was obtained.