Iron(<scp>iii</scp>) chloride modulated selective 1,2-trans glycosylation based on glycosyl trichloroacetimidate donors and its application in orthogonal glycosylation
作者:Mana Mohan Mukherjee、Nabamita Basu、Rina Ghosh
DOI:10.1039/c6ra21859h
日期:——
FeCl3 can also modulate the 1,2-trans selectivity of the reaction of 2-O-alkylated gluco- and galacto-pyranosyl trichloroacetimidates with phenolic compounds leading to the generation of the corresponding β-O-aryl glycosides in excellent yield and selectivity. Apart from these the present methodology has been successfully utilized for double glycosylation and orthogonal glycosylation reactions along
Selective Formation of β-<i>O</i>-Aryl Glycosides in the Absence of the C(2)-Ester Neighboring Group
作者:Matthew J. McKay、Benjamin D. Naab、Gregory J. Mercer、Hien M. Nguyen
DOI:10.1021/jo9002807
日期:2009.7.3
electron-withdrawing, and hindered phenols. The reaction is likely to proceed through a seven-membered ring intermediate, wherein the palladium catalyst coordinates to both C(1)-trichloroacetimidate nitrogen and C(2)-oxygen of the donor, blocking the α-face. As a result, the phenol nucleophile preferentially approaches to the top face of the activated donor, leading to formation of the β-O-aryl glycoside.
Use of Novel Homochiral Thioureas Camphor Derived as Asymmetric Organocatalysts in the Stereoselective Formation of Glycosidic Bonds
作者:Mildred López、Gabriela Huelgas、Mario Sánchez、Adalid Armenta、Angel Mendoza、José Daniel Lozada-Ramírez、Cecilia Anaya de Parrodi
DOI:10.3390/molecules29040811
日期:——
and 1:73 α:β stereoselectivity; under the same reaction conditions, without using a catalyst, the obtained stereoselectivity was 1:35 α:β. Computational calculations prior to the formation of the products were modeled, using density functional theory, M06-2X/6-31G(d,p) and M06-2X/6-311++G(2d,2p) methods. We observed that the preference for β glycoside formation, through a stereoselective inverted substitution
described using 2–20 mol% FeCl3/C as the catalyst and benzylated propargyl glycosides as the donors to reach yields up to 96% under mild condition. With an octatomic-ring intermediate at the α-face of FeCl3/C with alkyne of propargyl glycosides, a panel of aglycones comprising aliphatic, alicyclic, unsaturated alcohols, halogenated alcohols, and phenols with different substitution were examined successfully