The total synthesis of enantiomerically enriched (3S, 5R, 3'S, 5'R)-capsorubin (1) by aldol condensation of (1R, 4S)-1-(4-hydroxy-1,2,2-trimethyl-cyclopentyl) ethanone (2a) and crocetindial (3) is described. An alternative, short eight-step synthesis of the optically active compound 2a (ee 89%) is also reported.
carotenoid; capsorubin; crocetindial; cyclopentane keto-alkohol; synthesis