The participation of the beta -hydroxyketone part of callystatin A in the p
otent cytotoxicity was analyzed through the analogue-syntheses and the asse
ssment of their biological potencies. The ketonic carbonyl, the 19-hydroxyl
, and the three asymmetric methyl groups located in the beta -hydroxyketone
part of callystatin A were revealed to contribute to the cytotoxic potency
, respectively. Moreover, the alpha,beta -unsaturated delta -lactone portio
n was shown to serve as a conclusive functional group for the cytotoxic act
ivity. (C) 2000 Elsevier Science Ltd. All rights reserved.