MK4588, a new antibiotic related to xanthocillin

A new antibiotic, MK4588, structurally related to xanthocillin, was isolated from the culture broth of Leptosphaeria sp. L-179. Antibiotic MK4588 exhibited inhibitory activity against a limited range of Gram-positive and Gram-negative bacteria. The antibiotic was degraded by alkali to a more active product. The structures of MK4588 and the degradation product were determined to be (1R*,6S*,7S*)-7-(Z)-(1-isocyano-2-(4-methoxyphenyl]ethenyl-1-hydro xy-7- isocyanobicyclo[4,2,0]oct-2-en-4-one and (Z)-2,3-diisocyano-1-(4-methoxyphenyl)buta-1,3-diene, respectively, by NMR spectral analyses coupled with X-ray crystallographic analysis of MK4588.