Total synthesis of the marine sponge pigment fascaplysin

✍ Scribed by Benjamin Pelcman; Gordon W Gribble

• Book ID: 104228625
• Publisher: Elsevier Science
• Year: 1990
• Tongue: French
• Weight: 248 KB
• Volume: 31
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)97367-2

✦ Synopsis

Fascaplysin (I), an antimicrobial and cytotoxic red pigment from the marine sponge Fascaplysinopsis sp., has been synthesized in seven steps from indole (65% yield). The pivotal intermediate in the synthesis is diindole 3 which is induced to undergo acid-catalyzed cyclization and dehydrogenation to afford the desired pentacycle 2 in > 90% yield. Peracid oxidation of 2 yields fascaplysin.

A red pigment, fascaplysin, was recently isolated from the Fijian sponge Fascapfysinopsis Bergquist sp. and characterized as the novel lW-pyrido[l,2-a:3,4-Wldiindole 1, a ring system (2) that is apparently unique among natural products.1 Fascaplysin (1) inhibits the growth of several microbes and is active against the L-1210 mouse leukemia system in virro.1 Herein we describe the first total synthesis of fascaplysin.

Our approach to the synthesis of 1 was predicated on the belief that diindole 3 would undergo regioselective electmphilic attack at the presumed more reactive unsubstituted indole-pposition2 and concomitant cyclization to 4. Subsequent oxidation would complete the synthesis.