2 ACYCLIC KAHALALIDES FROM THE SACOGLOSSAN-MOLLUSK ELYSIA-RUFESCENS

The sacoglossan mollusk Elysia rufescens elaborates six cyclic depsipe ptides, kahalalides A-F. Its green algal diet (Bryopsis sp.) contains kahalalide G, which is an acyclic analogue of kahalalide F. Further an alysis of the molluskan extract revealed two new acyclic peptides, kah alalide H (1) and kahalalide J (2), which share only four amino acids (leucine, phenylalanine, serine, and valine) with kahalalide F. Both c ontain aspartic acid and 4-hydroxyproline residues, and kahalalide J ( 2) also contains lysine. They have in common beta-hydroxy fatty acid, 3-hydroxy-9-methyldecanoic, previously encountered in kahalalide E. Fo r kahalalide Il (1) we succeeded in determining the sequential positio ns of the antipodal D- and L-phenylalanine. In common with the acyclic constituent of the alga, kahalalide G, the new compounds lack signifi cant cytotoxicity.