CORALLOIDIN-C CORALLOIDIN-D, AND CORALLOIDIN-E - NOVEL EUDESMANE SESQUITERPENOIDS FROM THE MEDITERRANEAN ALCYONACEAN ALCYONIUM-CORALLOIDES

The Mediterranean alcyonacean Alcyonium (=Parerythropodium) coralloides (Pallas, 1766) is shown to contain the novel eudesmane sesquiterpenoids coralloidin C (=(-)-(4R,10S)-eudesma-5,7(11)-dien-15-yl acetate; (-)-4), coralloidin D (=(-)-(10R*)-eudesma-4,7(11)-diene-12,13-diyl diacetate; (-)7), and coralloidin E (=(+)-(4R*,10R*)-eudesma-5,7-dien-11-ol; (+)-8). The absolute configuration of (-)-4 is derived by the exciton-coupling method, applied to deacetylcoralloidin C p-anisate ((-)-6). Coralloidin E ((+)-8), being also obtained on treatment of deacetylcoralloidin A (=(+)-(4R*.8R*,10R*)-eudesma-5,7(11)-dien-8-ol; (+)-2) with (COCl)2 in DMSO is configurationally correlated to coralloidin A (=(+)-(4R*,8R*,10R*)-eudesma-5,7(11)-dien-8-yl acetate; (+)-1). Under acidic conditions, (+)-2 undergoes a complex rearrangement giving (+)-(3R*,4S*,5R*,6R*,7S*)-arist-10-(1)-en-3-ol ((+)-9), which is also obtained, together with (+)-8, on attempts to mesylate (+)-2.