Proline‐Containing Dipeptides from a Marine Sponge of a Callyspongia Species

Abstract magnified image A detailed analysis of the chemical constituents of a marine sponge of Callyspongia sp. was performed. A new proline‐containing dipeptide, callyspongidipeptide A (cyclo ‐ (( S )‐Pro ‐ 8 ‐ hydroxy ‐ ( R )‐Ile); 1 ) along with cyclo‐(( S )‐Pro‐( R )‐Leu) ( 3 ) and seco‐(( S )‐Pro‐( R )‐Val) ( 2 ) were isolated. The structures were determined on the basis of NMR and MS analysis, and the absolute configuration was determined by comparison of the optical rotation with known compounds.