Structural elucidation studies on 14- and 16-membered macrolide aglycones by accurate-mass electrospray sequential mass spectrometry

Abstract

Collision induced dissociation sequential mass spectrometry was used to investigate the fragmentation of the heptaketide macrolide aglycones, 6-deoxyerythronolide B (6-dEB), erythronolide B (EB), and acetate-starter EB (Ac-EB). The fragmentations of two previously reported octaketide analogs produced by "stuttering" of the erythromycin polyketide synthase, stuttered-6-dEB and acetate-starter stuttered-6-dEB were also studied. The accuracy with which the mass of each fragment was measured allowed it to be attributed to an unambiguous formula. Most of the experiments were repeated using samples dissolved in deuterated solvents. These data were then used to deduce plausible fragmentation pathways of the five compounds which were shown to have a high degree of similarity. Preliminary fragmentation analysis of a novel octaketide analog was performed and the structure was predicted as stuttered EB. Subsequent scale-up of the bacterial fermentations, followed by isolation and characterization by nuclear magnetic resonance spectroscopy confirmed this prediction. Further fragmentation experiments were then performed on this compound, which provided further evidence of the similarity of the fragmentation schemes. These results demonstrate the utility of collision induced dissociation sequential mass spectrometry analysis in the preliminary screening of bacterial fermentations for new polyketides. These studies were performed by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry. (J Am Soc Mass Spectrom 2002, 13, 862-874)

Electrospray ionization mass spectrometry screening of piperidine alkaloids from Senna spectabilis (Fabaceae) extracts: fast identification of new constituents and co-metabolites

“…11,[23][24][25][26][27] Advances in the development of high-resolution MS and the elucidation of gas-phase fragmentation chemistry is now helping in the analysis of new compounds and new organic reactions. [28][29][30][31][32] In this study, we report a ESI-MS/MS spectrometric method for characterization of piperidine alkaloids from flowers and fruits extracts of S. spectabilis. This technique is also shown to be an excellent tool for analysis of the different alkaloid isomers co-metabolites as a homologous series, which constitutes the chemical profile or "fingerprint" in whole tissues.…”

Fragmentation pathways of new aza derivatives of 16‐membered macrolide antibiotic—analog of Josamycin investigated by ESI and FAB mass spectrometric methods

“…The cleavages of J1-J3 lactone rings are not visible in the FAB and ESI mass spectra in contrast to the ESI-FTICR MS-MS spectra of other 14-and 16-membered macrolide aglycones. [23] The kind of the substituent in the amine part within J1-J3 derivatives influences the stability of protonated aza derivatives of 2,3-unsaturated JOS under FAB and ESI conditions.…”

Fragmentation studies on tetronasin by accurate-mass electrospray tandem mass spectrometry

“…ϩ are investigated using the conditions previously optimized in our laboratory [13]. The fragmentation analyses were performed on an FT-ICR instrument to produce accurate-mass data and to enable the elucidation of fragmentation routes by multistage tandem mass spectrometry (MS n ).…”