A new imidazole alkaloid from the marine sponge Leucetta microrhaphis

The marine sponge Leucetta microrhaphis yields a new imidazole alkaloid along with the known clathridine zinc complex. The new metabolite, (9E)-clathridine 9-N-(2-sulfoethyl)imine, crystallizes as a yellow needle with a melting point of 275-277 degrees C. High-resolution mass measurement sets its molecular formula as C18H20N6O6S. Spectroscopic studies suggest a 1,3,4-trisubstituted benzene ring, with a methyleneoxy ring occupying the C-3 and C-4 positions. The major difference with the zinc complex is a two-carbon unit attached to ring A. An X-ray study also reveals a taurine residue at C-9 that hinders complexation with zinc.