An intramolecular anionic migration of a stannyl group from the 6-positionof 1-(2-deoxy-D-erythro-pent-1-enofuranosyl)uracil to the 2 '-position: synthesis of 2 '-substituted 1 ',2 '-unsaturated uridines

Lithiation of 1-[3,5-bis-O-(tert-butyldimethylsilyl)-2-deoxy-D-erythro-pent -1-enofuranosyl)uracil (1) takes place exclusively at the 6-position of the uracil base. The 6-tributylstannyl (or 6-trimethylsilyl) derivative prepar ed by quenching the C6-lithiated species with Bu3SnCl (or Me3SiCl) was foun d to undergo an intramolecular anionic migration to the 2'-positon of the f uranoid glycal portion. By manipulation of the 2'-stannyl group, 2'-halogen o and 2'-carbon-substituted 1',2'-unsaturated uridines were prepared for th e first time. In contrast to the reported instability of 1 during deprotect ion, the 2'-substituted analogs synthesized in the present study gave the c orresponding free nucleosides uniformly in high yields upon treatment with NH4F in MeOH. (C) 2000 Elsevier Science Ltd. All rights reserved.