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

Article abstract of DOI:10.1016/0008-6215(91)80006-9

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. 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.