ALMAZOLE-C, A NEW INDOLE ALKALOID BEARING AN UNUSUALLY 2,5-DISUBSTITUTED OXAZOLE MOIETY, AND ITS PUTATIVE BIOGENETIC PEPTIDIC PRECURSORS, FROM A SENEGALESE DELESSERIACEAN SEAWEED

From product isolation and biomimetic synthesis - which also establish es absolute configurations - the known oxazole alkaloids almazoles A ( (+)-1) and B ((+)-2) seem to arise in a Senegalese delesseriacean seaw eed from, in sequence, the new modified peptide prealmazole C ((+)-4) and the oxazole alkaloid almazole C ((+)-3a). N,N- Dimethyl-L-phenylal aninamide ((+)-7) and the new peptides (+)-5 and (+)-6, as well as a s eries of known small units, are also involved. In all cases, the oxazo le ring is peculiarly 2,5-inserted.