1'-(2-Phenyl-ethylene)-ditryptophenaline, a new dimeric diketopiperazine from Aspergillus flavus.

A new diketopiperazine dimer, 1'-(2-phenyl-ethylene)-ditryptophenaline [1], was isolated together with ditryptophenaline [2] from the fungus Aspergillus flavus. The structure of 1 was determined by analysis of spectroscopic data. In contrast to the structurally related substance-P antagonist WIN 64821 [3], both 1 and 2 are weak substance-P inhibitors, indicating that stereochemistry at the position of dimerization is an important determinant of biological potency for these molecules.