Approaches to Construction of the Medium-Sized Ring Structure in Zetekitoxin AB by Ring-Closing Metathesis.

Zetekitoxin AB (ZTX), a member of the saxitoxin (STX) family isolated from the Panamanian golden frog , shows extremely potent Na-inhibitory activity. Here, we investigate the synthesis of 12-membered ring structure with the C11 tertiary hydroxyl group in ZTX by means of the Mislow-Evans rearrangement reaction and subsequent ring-closing metathesis reaction. Although this approach did not provide access to the 12-membered macrocycle, we obtained a new STX analog with an 18-membered macrolactam structure as a synthetic mimic of ZTX.