Structural elucidation studies of 15-membered azalide macrocycles using H/D exchange and ESI-MSn

• The azithromycin aglycone and its derivatives were analyzed by ESI-MSn.
• The fragmentation reactions of macrocycles were studied by H/D exchange and HRMS.
• The fragmentation pathways of [M+H]+ and [M+Na]+ ions were proposed.

A comprehensive study of fragmentation pathways of 15-membered azalide macrocycles using electrospray ionisation with multistage mass spectrometry (ESI-MSn) is presented in this work. Hydrogen/deuterium (H/D) exchange experiments and high-resolution mass spectrometry were used to investigate the proposed fragmentation pathways. In addition, the fragmentation patterns of sodium adduct ions [M+Na]+ of the macrocycles were also investigated as the presence of an alkali metal interacting with the aglycone ring influences the product-ion spectra.

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