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Total syntheses of the cytotoxic marine natural products bengamides B and E are described. Both bengamides are prepared via amide coupling of a protected polyhydroxylated lactone intermediate 9 with a suitably substituted aminocaprolactam intermediate. Lactone 9 is prepared in five steps from commercially available alpha-D-glucoheptonic gamma-lactone. The key reactions are a selective deprotection of a 1,2-acetonide in the presence of a 1,3-acetonide and an (E)-selective olefination of an unstable aldehyde using a gem-dichromium reagent. The bengamide B lactam intermediate 10 is prepared in seven steps from commercially available (5R)-5-hydroxy-L-lysine (12). The desired S-configuration at the gamma-OH lactam position is established using the Mitsunobu reaction.

The structural chemistry and biological activity of the bengamide class of compounds have been further characterized. Extracts prepared from recollected Jaspis cf. coriacea from five sites in Fiji were pooled. Six new bengamides, M (7b), N (8a), O (8b), P (9a), Q (9b), and R (10), were identified, accompanied by the known bengamides A (1a), B (1b), E (3a), F (3b), Y (5), Z (6), L (7a), G (11a), H (11b), and I (12). The structures of the new compounds were determined from spectroscopic data, and some were additionally confirmed by semisynthesis. Cytotoxicity screening data were obtained from the NCI-DTP 60 cell screen for bengamides A, B, and P. Bengamides A and B were more potent than bengamide P, with average IC(50) values of 0.046, 0.011, and 2.70 FM, respectively. The in vitro antitumor activity against MDA-MB-435 human mammary carcinoma was also determined for natural bengamides A, B, E, F, P, M, O, and Z and for synthetic samples of B and O. The best activity was observed for the natural bengamides A (IC(50) = 1 nM) and O (IC(50) = 0.3 nM).