Unique Reactions of Glycosyl Iodides with Oxa- and Thiocycloalkane Acceptors
摘要:
[GRAPHICS]Glc: R, R'''' = H; R', R'',R''' =OBn Gal: R', R''' =H; R', R'', R''' = OBn Man: R, R'''=H;R-1, R'''' =OBn; R''=OAcGlucosyl-, galactosyl-, and mannosyl iodides efficiently react with strained oxacycloalkane acceptors to afford O-glycosides with high-beta-selectivity. The mechanism of ring opening was investigated by reacting mannosyl iodides with pure enantiomers of propylene oxide and styrene oxide. Competition experiments between three- and five-membered oxacycloalkanes were also investigated. Finally, beta-thiomannosides were synthesized from thiocycloalkane acceptors.