Regiochemical control of the ring opening of 1,2-epoxides by means of chelating processes.: Part 17:: Synthesis and opening reactions of cis- and trans-oxides derived from (2S,6R)-2-benzyloxy-6-methyl-3,6-dihydro-2H-pyran, (2R,6R)- and (2S,6R)-2-methoxy-6-methyl-5,6-dihydro-2H-pyran

The regiochemical behavior of the title deoxy anhydrosugars, prepared in an enantioselective way starting from methyl alpha-D-glucopyranoside, was examined in opening reactions, both under standard and chelating conditions. The results clearly indicate the influence of the reaction conditions and the importance of the relative orientation of the methyl group with respect to the oxirane ring on the regiochemical outcome of these epoxides. An useful inversion of regioselectivity is obtained in some cases. (C) 2002 Elsevier Science Ltd. All rights reserved.