Biologically active compounds from tunicates and a sponge

Abstract

Part I. Studies on structures and biological activities of didemnins. Six new cyclic depsipeptides related to didemnins were isolated from a relatively polar extract of the tunicate T. solidum. Their structures were determined by spectroscopic techniques and chemical degradations as follows: didemnins X ((R)-3-hydroxydecanoyl-(Gln)$\sb3$-Lac-Pro-didemnin A); Y ((R)-3-hydroxydecanoyl-(Gln)$\sb4$-Lac-Pro-didemnin A); M (pGlu-Gln-Lac-Pro-didemnin A); N ( (Tyr$\sp5$) didemnin B); nordidemnin N ( (Tyr$\sp5$) nordidemnin B); and epididemnin A ( ($2S,4R$-Hip$\sp2$) didemnin A). Twenty two new didemnin analogues were prepared semisynthetically. Structure elucidation, chemical conversion, biological activities including cytotoxicity, antiviral and immunosuppressive activities and structure-activity relationships for the above compounds are described.

Part II. Ecteinascidins 736 and 722: New antitumor alkaloids from the Caribbean tunicate Ecteinascidia turbinata. Four known ecteiascidins (Et's) 743, 729, 745 and 759B, and triptamine hydrochloride, and two new compounds Et's 736 and 722 were isolated from the extract of Caribbean tunicate E. turbinata. Structures of three ecteinascidins, Et's 736, 722 and 759B, were determined spectroscopically. In vitro antimicrobial activity, cytotoxicity, and immunosuppressive activity for all of the above compounds and antitumor activities for Et's 722 and 729 are reported. Both Et's 722 and 729 showed significant activity against P388, B16 and Lewis lung carcinoma models in mice.

Part III. A new polyether acid from a cold water marine sponge, a Phakellia species. A new polyether acid 14,15-dihydrodinophysistoxin-1 was isolated from a cold water marine sponge Phakellia sp. along with the related known compounds okadaic acid and dinophysistoxin-1. These compound showed strong cytotoxicity against L1210 murine leukemia cells (IC$\sb{50}$'s 3 ng/mL).