Abstract
Three peptide-like yellow compounds (1, 2, 3) containing a guanidine moiety, one of which (named hymenialdisine, 2) is a monobrominated derivative, and six 3β-hydroxymethyl-A-norsterane derivatives [purified as the acetates : 4a, 5a, 6a, 7a (a mixture of two compounds), and 8a] were isolated from the Okinawan marine sponge Hymeniacidon aldis and their structures were elucidated on the basis of physicochemical evidence including the X-ray crystallographic analysis of 2.