Concise asymmetric synthesis of two natural oxacyclododecindione-type macrolactones from industrial waste.

( S )-5-Methyl-tetrahydropyran-2-one 1 is a by-product in the production of key intermediates of steroidal hormones. Asymmetric synthesis of natural oxacyclododecindione-type macrolactones 2 and 3 has been realized for the first time from ( S )-1 in seven and eight steps with 37% and 27% overall yield, respectively.