(±)-3α,5α-Bis(methoxycarbonyl)-3β-methyl-6α-phenyltetrahydro-2H-pyran-2-one

The structure determination of the title compound, dimethyl (+/-)-3 beta-methyl-2-oxo-6 alpha-phenyl-3,4,5,6-te hydro-2H-pyran-3 alpha, 5 alpha-dicarboxylate, C16H18O6. Unequivocally establishes its relative stereochemistry. The results provide strong support for the proposal that enolates derived from cis-5,6-disubstituted tetrahydro-2H-pyran-2-ones react very selectively with electrophiles trans to the C(5) and C(6) substituents.