A Chemoenzymatic Approach for the Synthesis of Unnatural Disaccharides Containing D‐Galacto‐ or D‐Fucofuranosides

Abstract

AbstractUnusual diglycosides composed of D‐hexofuranosyl entities were prepared by a chemoenzymatic route using the α‐L‐arabinofuranosidase, AbfD3. The required, unprotected monosaccharidic donors were first prepared according to multi‐step syntheses. Since one goal of this study was the investigation of donor –1 subsite in the active site of the enzyme, we focused on D‐fucofuranosyl and 6‐deoxy‐6‐fluoro‐D‐galactofuranosyl derivatives which present stereochemical similarities with L‐arabinose series, but also structural variations on the side arm. These substrates were then used in AbfD3‐catalysed hydrolyses to determine the parameters Km and kcat and in AbfD3‐catalysed transglycosylation to evaluate their ability to serve as donor/acceptor. Four disaccharides were thus isolated and characterised, two resulting from β‐(1,2) connection along with two β‐(1,3)‐regioisomers. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)