Conformational studies on tricyclic quinazolones derived from cyclodipeptides incorporating sarcosine

Abstract

Ring C of the tricyclic quinazolone 2-methyl-1,2-dihydropyrazino[2,1-b]quinazoline-3(4H),6-dione (VII) has conformational flexibility. However, introduction of a 4-methyl group as in (IX) locks the molecule in the conformation in which the 4-methyl group is axial.