Isolation and structure determination of the main related substances of teicoplanin, a glycopeptide antibiotic.

Teicoplanin is a complex formed by five closely related glycopeptides and by a small amount of a hydrolysis product. Minor quantities of related substances are also present. Two of them (named RS-1 and RS-2) were isolated and purified starting from the tailing fractions of a teicoplanin batch. Preparative reversed-phase liquid chromatography on large low-pressure and medium high-pressure scales, concentration, desalting, and freeze-drying steps were applied. 300 mg of RS-1 and 900 mg of RS-2 were obtained in a purity grade (about 90%) sufficient for structural investigation. Starting from considerations on the HPLC retentivity and on biosynthesis, the structures were assigned on the basis of 1H-N.M.R. spectra and homonuclear CO-SY 2D experiments, FAB-MS spectrometry, and GC-MS of the esters of the fatty acids obtained by hydrolysis. RS-1 and RS-2 are teicoplanins having 10-methyl-undecanoic acid and n-dodecanoic acid, respectively as fatty acid chains. No major difference in the in vitro activity of these teicoplanins emerged in comparison with teicoplanin complex.