Partial synthesis and characterization of capsokarpoxanthins and 3,6-epoxycapsanthins

The acid-catalyzed hydrolysis of (3S, 5R, 6S, 3'S, 5'R)-5,6-epoxycapsanthin (5) led to (3S,5R,6R,3' S,5' R)- (7) and (3S,5R,6S,3'S,5'R)-capsokarpoxanthin (8). In addition, (3S,5R,8R,3'S,5'R)- (9), (3S,5R,8S,3'S,5'R)-capsochrome (10), and (3S,5R,6R,3'S,5'R)-3,6-epoxycapsanthin (11) were obtained. The acid-catalyzed hydrolysis of (3S,5S,6R,3'S,5'R)-5,6-epoxycapsanthin (6) afforded (3S,5S,6R,3'S,5'R)-capsokarpoxanthin (12), (3S,5S.SS,3'S,5'R)-(13) and (3S,5S,8R,3'S,5'S)-capsochrome (14) as well as (3S,5S,6R,3'S,5'R)-3,6-epoxyepicapsanthin (15). Compounds 5-15 were isolated in crystalline form and characterized by their UV/VIS, CD, H-1- and C-13-NMR, and mass spectra.