The Peptidolipide J (CH(3)-(CH(2))(n)-CO-D Phe-L Ile-L Ile-L Phe-L Ala-O-CH(3)) is obtained also in acidic form by a chromatographic artefact. In chloroformic solutions the ester and the acid behave in a very different way: the acid has a stable conformation, as shown by the infra-red spectra and the optical rotary dispersion; this conformation is stabilized by hydrogen bonding between two peptide chains associated as a carboxylic dimer.
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Faculté des Sciences de Toulouse, 31, Toulouse, France