Myxochromide B3, a new member of the myxochromide family of secondary metabolites.

Myxochromides are cyclic depsipeptides with an unsaturated polyketide side chain, which have been reported from different myxobacterial species, e.g., Myxococcus xanthus and Stigmatella aurantiaca. To date, myxochromides are subdivided into the groups A and S, according to their peptidic core structure. The peptide moiety of the new myxochromide B3 (1), which was isolated from a myxobacterial strain of the genus Myxococcus, differs from that of myxochromides A and S. Compound 1 thus is the first representative of a new group of myxochromides. For myxochromide A3 (2) the complete and assigned spectroscopic data are described. For the structure elucidation one- and two-dimensional NMR spectroscopy as well as mass spectrometry have been applied. Configurational analysis has been accomplished by chiral GC-MS and HPLC.