Abstract
AbstractThe stereoselective introduction of a glycosidic bond presents the greatest challenge to complex oligosaccharide synthesis. Important developments such as automated polymer‐supported oligosaccharide synthesis will not realize their full potential until this problem is addressed. In this paper, a novel approach for stereoselective glycosylations is described whereby a chiral auxiliary at C‐2 of a glycosyl donor controls the anomeric outcome of a glycosylation. It was found that participation of an (S)‐ethoxycarbonylbenzyl auxiliary led to the formation of 1,2‐cis glycosides, probably through a trans‐fused dioxolenium ion intermediate. On the other hand, the use of an auxiliary with (R) configuration gave 1,2‐trans glycosides, and this glycosylation proceeds through a cis‐fused dioxolenium ion intermediate. The auxiliary could conveniently be removed by Birch reduction. Computational studies support the formation of the proposed ethoxy‐carbonium ion intermediate with all pseudo‐equatorial substituents. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
