Solution conformations of two synthetic analogues of quinoxaline antibiotics

Abstract

The solution conformations of two synthetic quinoxaline antibiotics (TANDEM and ELSERTA) have been determined by proton n.m.r. The parameters utilised include chemical shifts, coupling constants, and the temperature variation of NH chemical shifts (all in the solvents [²H]chloroform, [²H₅]pyridine, and [²H₆]dimethyl sulphoxide). The conclusions have then been checked and amplified by the measurement of nuclear Overhauser effects in CDCl₃ solution to indicate proximities of the various protons. The structures deduced are compared with other conformationally detailed structures of quinoxaline antibiotics, and their relevance to DNA-binding studies is discussed.