N-Acylheptapeptides Surfactin, Esperin and Related Compounds

By screening more than 100 strains of Gram positive bacteria for the presence of compounds with surfactant activity, a protoplast-bursting 

The optimal rate of surfactin synthesis occurs at the end of the exponential growth phase. A study of the incorporation of labelled 

An incompletely characterized peptidolipid with the same amino acid composition as surfactin has been isolated from the Marburg strain of Bacillus subtilis, and appeared to be located in the cell membrane. It was synthesized continuously during the growth of the bacteria and its content increased in phosphate-limited cultures (100). 

In the course of screening for inhibitors of cyclic adenosine-3, 5 -monophosphate phosphodiesterase, a strain of B. subtilis was found to produce a series of such inhibitors. These compounds with a m.p. of 136-139 °C and an optical rotation of -h 37° to 38.5° (chloroform), — 33° to — 38° (methanol), were lipopeptides with the same peptide moiety as surfactin. Their fatty acid components were 3-hydroxy-ll-methyldodecanoic acid, 3-hydroxy-10-methyldodecanoic add, 3-hydroxytetradecanoic acid (the major component), 3-hydroxy-13-methyltetradecanoic acid (the same acid as that of surfactin) and 3-hydroxy-12-methyltetradecanoic acid (707, 702). The location of the lactone ring was established by the same method as that used for surfactin 96), Therefore these inhibitors had structures quite similar to, and for one of them identical with, that of surfactin (40). 

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), 

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