Isolation and structure determination of two new analogs of teicoplanin, a glycopeptide antibiotic

Teicoplanin is an antibiotic produced by fermentation of Actinoplanes teichomyceticus as a complex formed by five closely related glycopeptides characterized by different fatty acid chains of ten and eleven carbon atoms. In addition, minor quantities of related substances are present. Two of them, named RS-1 and RS-2, were shown to be teicoplanins having as fatty acid chains 10-methylundecanoic acid and n-dodecanoic acid, respectively. Other two related substances, named RS-3 and RS-4, have now been isolated and purified starting from fermentation broths of a mutant of the same microorganism producing them in substantial amounts. This was achieved by semipreparative reversed-phase liquid chromatography carried out on high-pressure scale. The structures were assigned on the basis of 1H NMR spectra and homonuclear COSY 2D experiments and fast atom bombardment MS spectrometry, in comparison with the large mass of data till now accumulated on teicoplanin. RS-3 and RS-4 are teicoplanins having as fatty acid chains 6-methyloctanoic acid and n-nonanoic acid, respectively.