Ortho ester Claisen rearrangements of three 3-C-(hydroxymethyl)methylene derivatives of hexofuranose: stereoselective introduction of a quaternary center on C-3 of D-ribo-, L-lyxo-, and D-arabino-hexofuranoses
The ortho ester Claisenrearrangement of D-ribo- or L-lyxo- hexofuranose derivative which possesses an allyl alcohol functionality on C-3, proceeds stereoselectively to give a 3-C-dialkylated product. The stereochemistry of a newly introduced quaternary center of the product was unambiguously established by a chemical modification.