LIFETIME OF THE GLUCOSYL OXOCARBENIUM ION AND STEREOSELECTIVITY IN THE GLYCOSIDATION OF PHENOLS WITH 2-ANHYDRO-3,4,6-TRI-O-METHYL-ALPHA-D-GLUCOPYRANOSE

Authors
CHIAPPE C LOMORO G MUNFORTE P
Citation
C. Chiappe et al., LIFETIME OF THE GLUCOSYL OXOCARBENIUM ION AND STEREOSELECTIVITY IN THE GLYCOSIDATION OF PHENOLS WITH 2-ANHYDRO-3,4,6-TRI-O-METHYL-ALPHA-D-GLUCOPYRANOSE, Tetrahedron, 53(30), 1997, pp. 10471-10478
Citations number
20
Categorie Soggetti
Chemistry Inorganic & Nuclear
Journal title
Tetrahedron → ACNP
ISSN journal
00404020
Volume
53
Issue
30
Year of publication
1997
Pages
10471 - 10478
Database
ISI
SICI code
0040-4020(1997)53:30<10471:LOTGOI>2.0.ZU;2-#
Abstract
The glycosidation of para substitued phenols with -anhydro-3,4,6-tri-O -methyl-alpha-D-glucopyranose. ZnCl2 catalysed, gives predominantly th e corresponding a-anomers. In the presence of an amino base, 1.1,3,3-t etramethylguanidine. however, enhances the beta-selectivity, which bec omes practically complete when the reaction is carried out under basic conditions, by addition of K2CO3 and 18-crown-6. A rationalisation ba sed on the lifetime of the oxocarbenium ion intermediate and on the nu cleophilicity of the phenols is proposed. (C) 1997 Elsevier Science Lt d.