Conformational Studies of Some Piperazine-2,5-Diones: Crystal Structures of Three Isomeric Forms of Methylanhydropicroroccellin (Derivative of a Lichen Diketopiperazine) and a Derivative Bromohydrin

Abstract

Single-crystal X-ray structure determinations have been carried out on three isomeric forms of the lichen diketopiperazine metabolite methylanhydropicroroccellin , C₂₁H₂₂N₂O₃, and a related bromohydrin , C₂₀H_l9BrN₂O₃; all are based on a 6-benzyl-3-benzylidene-1,4- dimethylpiperazine-2,5-dione but differ in the substituents on the α and β carbons at position 6, enabling comparison of the resulting variation in conformation.