C-Aryl glycosides: electrophile-initiated cyclizations of 6-aryl-5-hexen-2-ols
摘要:
An approach to the synthesis of C-aryl glycosides is described. Treatment of beta-lactam 9 with N-bromosuccinimide (NBS) or N-iodosuccinimide (NIS) afforded trans-2,6-disubstituted pyrans 11a and 11b. Treatment of 9 with phenylselenenyl chloride (PhSeCl) or N-(phenylselenenyl)phthalimide (N-PSP) gave 11c and cis-2,6-disubstituted pyran 12c in different ratios depending on the reaction conditions. Treatment of beta-lactam 10 with NBS, NIS, PhSeCl, or N-PSP gave mixtures of pyrans 16 and 17. Treatment of unsaturated alcohol 24a with PhSeCl gave pyran 23a. Conversion of 23a to virenose analog 22, a C-aryl glycoside related to the chrysomycins, was accomplished using a selenoxide elimination-osmium tetraoxide oxidation sequence.
Polymer-Supported Synthesis of a Branched Trisaccharide of the Type IA Group B Streptococcus Capsular Polysaccharide: 3-Iodo-4-methoxybenzyl as a New O-Protecting Group
作者:Seema Mehta、Dennis M. Whitfield
DOI:10.1016/s0040-4020(00)00612-8
日期:2000.8
independently synthesized and used to introduce this new protectinggroup. The levulinoyl and the IPMB protectinggroups have been used in an orthogonal manner to create 3,4-branching on a galactopyranosyl residue. Due to the enhanced acid stability of the IPMB group over the PMB group, the former group was critical to the success of the synthesis. The final trisaccharide and its intermediates were cleaved
C-Aryl glycosides: electrophile-initiated cyclizations of 6-aryl-5-hexen-2-ols
作者:David J. Hart、Vincent Leroy、Gregory H. Merriman、David G. J. Young
DOI:10.1021/jo00047a020
日期:1992.10
An approach to the synthesis of C-aryl glycosides is described. Treatment of beta-lactam 9 with N-bromosuccinimide (NBS) or N-iodosuccinimide (NIS) afforded trans-2,6-disubstituted pyrans 11a and 11b. Treatment of 9 with phenylselenenyl chloride (PhSeCl) or N-(phenylselenenyl)phthalimide (N-PSP) gave 11c and cis-2,6-disubstituted pyran 12c in different ratios depending on the reaction conditions. Treatment of beta-lactam 10 with NBS, NIS, PhSeCl, or N-PSP gave mixtures of pyrans 16 and 17. Treatment of unsaturated alcohol 24a with PhSeCl gave pyran 23a. Conversion of 23a to virenose analog 22, a C-aryl glycoside related to the chrysomycins, was accomplished using a selenoxide elimination-osmium tetraoxide oxidation sequence.