Template effect of vancomycin aglycon in the oxidative oligomerization of 1,6-dithio-d-mannitol: A MALDI-TOF MS and solvent effect study

Oxidative oligomerization of 1,6-dithio-d-mannitol (DTM) using air as oxidant is reported. It was found that both ring and chain oligomers were formed with a degree of polymerization up to 11–12 as determined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). It was found that the relative amounts of rings to chains were significantly dependent on the solvent employed: in water or in dimethyl formamide (DMF) yielded ring oligomers with a relative amount of higher than 90% (on the average), and almost exclusive formation of chain oligomers was observed in methanol or in dioxane. The oxidative oligomerization of DTM was also carried out in the presence of vancomycin aglycon as a template. It was observed that in water the vancomycin aglycon induced the exclusive formation of chain oligomers from DTM. The non-covalent, strong interaction existing between the vancomycin aglycon and the chain dimer of DTM was further supported by electrospray ionization mass spectrometry (ESI-MS).