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-Metoxy-6-methyl-5,6-dihydro-2H-pyran

The regiochem. behavior of the title deoxy anhydrosugars, prepd. in an enantioselective way starting from Me α-D-glucopyranoside, was examd. in opening reactions, both under std. and chelating conditions. The results clearly indicate the influence of the reaction conditions and the importance of the relative orientation of the Me group with respect to the oxirane ring on the regiochem. outcome of these epoxides. A useful inversion of regioselectivity is obtained in some cases