Novel alkaloids from the red ascidian botryllus leachi

Abstract The red ascidian Botryllus leachi contains two novel pyrazine alkaloids, botryllazine A ( 1 ) and botryllazine B ( 2 ) together with the new imidazole alkaloid 2-( p -hydroxybenzoyl)-4-( p -hydroxyphenyl)imidazole ( 3 ). The structures of compounds 1 – 3 were elucidated by interpretation of spectral data, with special emphasis on the analyses of 1 H- 13 C couplings. Botryllazine A ( 1 ) represents the first example of a marine alkaloid containing a pyrazine nucleus derived from three tyrosine precursors. It is proposed that the biogenetic pathway leading from two tyrosine precursors to botryllazine B ( 2 ) involves amide formation and, subsequently, cyclization via imine formation. The cytotoxicity assay results of the new compounds 1 – 3 against four tumor cell lines are presented.