Ulbactins F and G, Polycyclic Thiazoline Derivatives with Tumor Cell Migration Inhibitory Activity from Brevibacillus sp.

Two new structurally unique compounds bearing a nitrogen- and sulfur-containing tricyclic ring system, ulbactin F (<b>1</b>) and its diastereomeric isomer ulbactin G (<b>2</b>), were isolated from the culture extract of a sponge-derived Brevibacillus sp. The structures and absolute configurations of <b>1</b> and <b>2</b> were determined by NMR analysis and X-ray crystallographic analysis. These compounds inhibit the migration of tumor cells in the submicromolar to micromolar range