A rapid divergent synthesis of highly substituted delta-lactones.

[reaction: see text] Nucleophilic 1,2-addition of (Z)-gamma-silyloxyvinylzinc reagents to ethyl glyoxylate followed by desilylation and cyclization affords 3,6-dihydro-3-hydroxypyran-2-ones in good chemical yields. In situ formation of allylic phosphates followed by reaction with RCu(CN)Li reagents affords substituted 5,6-dihydropyran-2-ones. The parent compound, 3,6-dihydro-3-hydroxypyran-2-one, undergoes allylic phosphate formation, cuprate-mediated allylic substitution, and 1,4-conjugate addition to afford trans-4,5-disubstituted tetrahydropyran-2-ones in a one-pot process.