Total synthesis of (3S, 5R, 3'S, 5'R)-capsorubin

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.