2,6-Disubstituted Benzoates As Neighboring Groups for Enhanced Diastereoselectivity in beta-Galactosylation Reactions: Synthesis of beta-1,3-Linked Oligogalactosides Related to Arabinogalactan Proteins
Nathan W McGill, Spencer J Williams
JOURNAL OF ORGANIC CHEMISTRY | AMER CHEMICAL SOC | Published : 2009
Arabinogalactan proteins (AGPs) are plant glycoproteins which contain a beta-1,3-linked galactan core. The synthesis of the beta-galactopyranose-1,3-beta-galactopyranose linkage using various 2-O-acyl-protected glycosyl donors has been plagued with poor stereoselectivity and side reactions including orthoester formation and transesterification of the 2-O-acyl group from the donor to the acceptor. We have investigated the use of 2,6-disubstituted benzoyl groups as bulky neighboring groups on the glycosyl donor. A 2,4,6-trimethylbenzoyl group was found to be optimal and enabled the formation of the beta-galactopyranose-1,3-beta-galactopyranose linkage to disarmed ester-protected acceptors, sup..View full abstract
We express our appreciation to Mr, J. Johnson for his assistance. This work was supported by Biosupplies Australia Ltd. and the Australian Research Council. N.W.M. gratefully acknowledges financial support from the Albert Shimmins Memorial Fund. The late Emeritus Prof. Bruce Stone is acknowledged as a source of inspiration for this work.