Thermospray mass spectral analyses of corynomycolic acids and their derivatives

Thermospray mass spectral (TSP-MS) analyses were carried out on methyl corynomycolates, their 3-O-acetyl and 3-O-benzoyl derivatives, and on corynomycolic acids and their 3-O-acetyl derivatives, using an ion generating solvent system consisting of water/isopropanol (99:1, v/v) containing 0.1 M ammonium acetate. Methyl corynomycolates generated three groups of peaks corresponding to adducts M-18 + H, M + H and M + NH4, while two groups of peaks representing adducts M-60 + H and M + H + NH4 were seen in the spectra of 3-O-acetyl methyl corynomycolates. The 3-O-benzoyl methyl corynomycolates gave a series of peaks representing the adducts M-122 + H, M + 2H and M + H + NH4. In the spectra of 3-O-acetyl corynomycolic acids, a series of peaks which represented M-60 + H and M + NH4 was observed, and in turn, mass spectra of corynomycolic acids revealed peaks that represented the adducts M-18 + H and M + NH4. Therefore, methyl corynomycolates, 3-O-acyl derivatives of methyl corynomycolates,. 3-O-acetylated derivatives of corynomycolic acids and the underivatized corynomycolic acids all exhibited the formation of an adduct of the anhydro compounds. These anhydro forms were generated by a generalized process.