title: Stereoselective β-Mannosylation by Neighboring-Group Participation.
abstract: The stereoselective synthesis of glycosidic bonds is the main challenge of oligosaccharide synthesis. Neighboring-group participation (NGP) of C2 acyl substituents can be used to provide 1,2-trans-glycosides. Recently, the application of NGP has been extended to the preparation of 1,2-cis-glycosides with the advent of C2 chiral auxiliaries. However, this methodology has been strictly limited to the synthesis of 1,2-cis-gluco-type sugars. Reported herein is the design and synthesis of novel mannosyl donors which provide 1,2-cis-mannosides by NGP of thioether auxiliaries. A key element in the design is the use of (1) C4 locked mannuronic acid lactones to enable NGP of the C2 auxiliary. In addition to C2 participation a new mode of remote participation of the C4 benzyl group was identified and provides 1,2-cis-mannosides.
authors.affiliation: Institute for Molecules and Materials, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands.
authors.forename: Hidde
authors.initials: H
authors.lastname: Elferink
authors.affiliation: Institute for Molecules and Materials, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands.
authors.forename: Rens A
authors.initials: RA
authors.lastname: Mensink
authors.affiliation: Institute for Molecules and Materials, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands.
authors.forename: Paul B
authors.initials: PB
authors.lastname: White
authors.affiliation: Institute for Molecules and Materials, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands. t.boltje@science.ru.nl.
authors.forename: Thomas J
authors.identifier: 0000-0001-9141-8784
authors.initials: TJ
authors.lastname: Boltje
keywords: chiral auxiliaries; glycosylation; neighboring-group effects; stereoselectivity; sulfur