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

作者：McGill Nathan W; Williams Spencer J^*

来源：Journal of Organic Chemistry, 2009, 74(24): 9388-9398.

DOI：10.1021/jo902100q

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, suppressing transesterification and reducing orthoester formation while enhancing the P-selectivity of galactosylation reactions. A series of beta-1,3-linked oligogalactosides were prepared and elaborated to neoglycoconjugates for the study of AGP biosynthesis and AGP binding proteins.

• 出版日期2009-12-18