The title bicyclic lactone, C(19)H(19)NO(3), is an inter-mediate in the synthesis of chiral α-methyl-prolines and branched C-methyl pyrrolidines; the absolute configuration was determined by the use of d-erythronolactone as the starting material. It exhibits no unusual crystal packing features, and each mol-ecule acts as a donor and acceptor for one C-H⋯O hydrogen bond.