Lactams derived from hetero Diels-Alder adducts were stereospecifically converted into cis- 2, 4-pyrrolidinedicarboxylic acid and cis-2, 5-piperidinedicarboxylic acid by ruthenium tetroxide oxidation. Optically active (2S, 4S)-(-)-2, 4-pyrrolidinedicarboxylic acid and (2R, 4R)-(+)-2, 4-pyrrolidinedicarboxylic acid were synthesized from (1S, 4R)-(+)-2-azabicyclo [2.2. 1] hept-5-en-3-one and (1R, 4S)-(-)-2-azabicyclo [2.2. 1] hept-5-en-3-one, ...