Bu-2313, a new antibiotic complex active against anaerobes. III. Semi-synthesis of Bu-2313 A and B, and their analogs.

Analogs of Bu-2313 A and B were prepared by C-acylation of tetramic acid derivatives with the dienoic acid moiety obtained by periodate oxidation of Bu-2313 A or B. The C-acylation proceeded in the presence of a strong base such as potassium t-butoxide, sodium hydride or lithium hydride, whereas the use of triethylamine afforded O-acylated products. The semi-synthetic Bu-2313 analogs exhibited antibacterial spectra similar to the parent antibiotic but none exceeded Bu-2313 B in activity.