Absolute stereochemistry and antitumor activity of iejimalides

The absolute configurations at five chiral centers, except for C-32(S) reported previously, in iejimalides A, C, and D, potent cytotoxic 24-membered macrolides isolated from a tunicate Eudistoma cf. rigida, were assigned as 4R, 9S, 17S, 22S, and 23S on the basis of detailed analysis of NMR data and chemical means. Furthermore, the structures proposed for iejimalides A, C, and D were revised to their 13Z-isomers. Iejimalides A-D (1-4) exhibited antitumor activity in vivo.