Propioxatins A and B, new enkephalinase B inhibitors. II. Structural elucidation

The structures of propioxatins A (C17H29N3O6) and B (C18H31N3O6), new enkephalinase B inhibitors produced by Kitasatosporia setae SANK 60684, were determined. Both propioxatins consist of N-acyl-L-prolyl-L-valine. N-Acyl moieties of propioxatins A and B were alpha-propyl and alpha-isobutyl succinic acid beta-hydroxamic acid, respectively.