Esperinic acid

From B. mesentericus a peptidolipid exhibiting antibiotic properties was isolated and called esperin. It had m.p. 238 °C and — 24° (methanol). Mild saponification opened a lactone ring, thus giving esperinic acid of m.p. 195 °C, [a]p + 12.5° (methanol). A tentative structure (41) was proposed (103). However, because of differences in the properties of esperinic acid and a synthetic sample of the peptidolipid (41) the proposed structure was found to be incorrect (104),... 

Esperinic acid was studied by mass spectrometry and the revised structure (42) was established (705), in which 30% of the C-terminal l-leucine was replaced by L-valine. In order to locate the lactone ring esperin was treated with hydrazine followed by Curtius rearrangement... 

Esperin a cyclic antibiotic depsipeptide from Bacillus mesentericus. It contains a long-chain a-hydro-xy-fatty acid which is linked by an amide bond to the A-terminus of the sequence Glu-Leu-Leu-Val-Asp-Leu-Leu, and also forms a lactone with the y-carboxyl group of the Asp residue. 

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