Electrospray Ionization Mass Spectra of Piperazimycins A and B and γ-Butyrolactones from a Marine-derived Streptomyces sp.†

Chemical investigation of the marine-derived Streptomyces sp. Act8015 led to the isolation of two cyclic peptide antibiotics, piperazimycins A and B (1a, 1b). Their structures were confirmed on the basis of a detailed HRESI-MS/MS analysis. Additionally, a new butanolide, 4,10-dihydroxy-10-methyl-dodecan-4-olide (2), and the respective acid, 4,10-dihydroxy-10-methyl-dodecanoic acid (3a) were identified. Further isolated compounds were staurosporin, adenine, indole-3-carboxylic acid, ferulic acid, tryptophol, and three γ-butyrolactones: virginiae butanolide E (4e) and Graefe's Factors I (4f) and III (4g). The structures of 2 and 3a were confirmed by detailed 1D and 2D NMR studies and MS spectra and by comparison with related structures. A full signal assignment of virginiae butanolide E (4e) is reported here for the first time.