Cyclic Ether-Containing Macrolactins, Antimicrobial 24-Membered Isomeric Macrolactones from a Marine Bacillus sp.

Bioassay-guided isolation of bioactive metabolites from the ethyl acetate extract of a marine Bacillus sp. fermentation broth has led to the discovery of three new 24-membered macrolactones, macrolactins 1-3, which contain an oxetane, an epoxide, and a tetrahydropyran ring, respectively. The configurations of 1-3 were assigned by a combination of coupling constants, ROESY data analysis, and application of the modified Mosher's method. Compounds 1-3 showed in vitro antimicrobial activity.