Chemical Studies on the Antibiotic Esperin

Esperin is an acidic antibiotic with a molecular formula of C₃₉H₆₇N₅O₁₁ and, on hydrolysis with acid, it afforded l-aspartic acid, l-glutamic acid, l-valine, l-leucine, d-leucine and 2-tridecenoic acid. By treatment with alkali, esperin was transformed to esperinic acid, C₃₉H₆₉N₅O₁₂, which was shown to be β-hydroxytridecanoyl-glutamyl-aspartyl-valyl-leucyl-leucine. From chemical and physical studies, esperin was proved to be the lactone of esperinic acid, represented by the formula III.