Claisen rearrangement of hexenopyranoside allyl ethers: A new approach to α-branched-chain dicarbonyl sugars

Abstract The β-hydroxy phenylselenides prepared by cleavage of 2,3-anhydropyranosides with sodium phenylselenide were quantitatively transformed into the corresponding allyl ethers. Oxidation of the allyl ethers, followed by thermal elimination and rearrangement, gave C -allylhexosuloses in good yield. Rearrangement of ethers 10a and 10c was especially stereoselective, giving axially oriented C -allylhexosulose derivatives, which were readily epimerized to their equatorial isomers in quantitative yield. In the Claisen rearrangement of the crotyl ether 14c , the chirality of the sugar was transferred to the newly formed asymmetric carbon atom. This procedure provides a convenient method to convert an anhydro sugar into a C -allylhexosulose derivative.