Synthesis and Glycosylation of a Series of 6-Mono-, Di-, and Trifluoro <i>S</i>-Phenyl 2,3,4-Tri-<i>O</i>-benzyl-thiorhamnopyranosides. Effect of the Fluorine Substituents on Glycosylation Stereoselectivity
作者:David Crich、Olga Vinogradova
DOI:10.1021/ja0730258
日期:2007.9.1
A series of 6-mono-, di-, and trifluoro analogs of S-phenyl 2,3,4-tri-O-benzyl-D- or L-thiorhamnopyranoside has been synthesized and used as donors in glycosylation reactions, with activation by the 1-benzenesulfinyl pipe ridine/triflic anhydride system. The stereochemical outcome of the glycosylation reactions was found to depend on the electron-withdrawing capability of the disarming substituent at the 6-position, i.e., on the number of fluorine atoms present. The results are explained with regard to the increased stability of the glycosyl triflates, shown to be intermediates in the reaction by low-temperature H-1 NMR experiments, with increased fluorine content.
Increasing the inhibitory potency of l-arabino-imidazolo-[1,2]-piperidinose towards β-d-glucosidase and β-d-galactosidase
The synthesis of some potent inhibitors of two retaining beta-glycosidases was achieved by introducing aglycon-mimics into the imidazole moiety Of L-arabino azasugar 1. The strongest inhibition was observed with the phenyl-ethyl substituent at C(2) of 1 against beta-D-galactosidase and beta-D-glucosidase, whereas the hydroxymethyl group at C(2) increased only slightly the inhibitory properties. (C) 2003 Published by Elsevier Science Ltd.