Stereoselective synthesis and absolute configuration of the C33–C42 fragment of symbiodinolide

Cross-metathesis of methyl ester which was prepared from symbiodinolide with ethylene was performed to give the C33–C42 degraded fragment. This fragment was estimated to be (36S,40S)-diol by the modified Mosher method. Stereoselective synthesis of the (36S,40S)-diol and its diastereomer (36R,40S)-diol was achieved from l-aspartic acid. Synthetic bis-(S)- and (R)-MTPA esters which were derivatized from the (36S,40S)-diol exhibited spectroscopic data identical with those of bis-(S)- and (R)-MTPA esters derived from the degraded product. Thus, the absolute stereochemistry of the C33–C42 fragment was elucidated to be (36S,40S).