1-Hydroxysugars were dehydratively coupled with a variety of alcohols including thiophenol in the presence of a catalytic amount of ytterbium(III) triflate [Yb(OTf) 3 ] and methoxyacetic acid to give the corresponding glycosides in good to excellent yields, and in some cases, with high stereoselectivities. The reaction proceeds through selective esterification of 1-hydroxysugars with methoxyacetic
A Simple Synthesis of Methyl 2,3,6- and 2,4,6-Tri-<i>O</i>-benzyl-α-D-mannosides
作者:Shinkiti Koto、Kazuhiro Takenaka、Naohiko Morishima、Akiko Sugimoto、Shonosuke Zen
DOI:10.1246/bcsj.57.3603
日期:1984.12
Cotrolled benzylation of methyl α-D-mannopyranoside with benzyl chloride and LiOH selectively gave the 2,3,6-tribenzyl ether in a 53% yield. Such a reaction using benzyl chloride and KOH afforded mainly the 2,4,6-tribenzyl ether in a 41% yield. The products were allylated and then hydrolyzed to give the corresponding 1-OH derivatives.
Copper-mediated anomeric <i>O</i>-arylation with organoboron reagents
作者:Victoria Dimakos、Jacklyn J. W. Liu、Zhenlu Ge、Mark S. Taylor
DOI:10.1039/c9ob01022j
日期:——
Copper-mediated couplings of arylboroxines with glycosyl hemiacetals furnish O-aryl glycosides via Csp2-O bond formation. The method enables the anomeric O-arylation of protected pyranose and furanose derivatives, and is tolerant of functionalized arylboroxine partners. Whereas mixtures of anomers are formed from glucopyranose, galactopyranose and arabinofuranose hemiacetals, the α-anomer is generated