STRUCTURE ELUCIDATION OF A58365A AND A58365B, ANGIOTENSIN CONVERTING ENZYME INHIBITORS PRODUCED BY STREPTOMYCES CHROMOFUSCUS

Abstract

A58365A and A58365B, angiotensin converting enzyme inhibitors isolated from the culture filtrate of Streptomyces chromofuscus NRRL 15098, are homologous compounds of molecular formulas C₁₂H₁₃NO₆ and C₁₃H₁₅NO₆. The molecular similarities of the two inhibitors were established by comparison of their ¹H NMR, ¹³C NMR, and UV spectra. Catalytic hydrogenation of A58365A led to a tetrahydro-deoxy derivative, C₁₂H₁₇NO₅; extensive 1H NMR decoupling studies at 360 MHz allowed all the non-exchangeable protons of the derivative to be connected in a continuous substructure. This fragment was combined with information from other spectroscopic methods to suggest the structures for A58365A (1) and A58365B (2); the conclusions were confirmed by an X-ray crystallographic analysis of A58365A-dimethyl-ester.