β-Directing Effect of Electron-Withdrawing Groups at <i>O</i>-3, <i>O</i>-4, and <i>O</i>-6 Positions and α-Directing Effect by Remote Participation of 3-<i>O</i>-Acyl and 6-<i>O</i>-Acetyl Groups of Donors in Mannopyranosylations
作者:Ju Yuel Baek、Bo-Young Lee、Myung Gi Jo、Kwan Soo Kim
DOI:10.1021/ja907252u
日期:2009.12.9
isolation of a stable bicyclic trichlorooxazine ring resulting from the intramolecular trapping of the anomeric oxocarbenium ion by 3-O-trichloroacetimidoyl group provided evidence for this remote participation. The triflate anion, counteranion of the mannosyl oxocarbenium ion, was essential for the beta-selectivity, and covalent alpha-mannosyl triflates with an electron-withdrawing group at O-3, O-4