API-mass spectrometry of polyketides. II. Fragmentation analysis of 6-deoxyerythronolide B analogs.
The API-MS spectra of 6-deoxyerythronolide B (6-dEB) and a number of its analogs have been studied to gain information into the fragmentation patterns of 6-deoxyerythronolides under atmospheric pressure ionization conditions. The API-MS spectrum of 6-dEB shows five major families of fragments. The spectra of a series of desmethyl-6-dEBs allow assignment of these fragment families to structural subunits as well as provide information regarding the fragmentation mechanisms. The spectrum of [9-(18)O]-6-dEB is consistent with loss of the ketone oxygen during the first dehydration, and the spectra of other oxygen-modified analogs implicate the non-obligate formation of a 5,9-hemiacetal in the initial stages of fragmentation. These results taken together are used to propose a model for the fragmentation of 6-dEB and its analogs under API conditions.
Ashley
Gary W
GW
Department of Chemistry, Kosan Biosciences, Inc., 3832 Bay Center Place, Hayward, CA 94545, USA. ashley@kosan.com
Carney
John R
JR
D001274:Atmospheric Pressure; D004917:Erythromycin / Q000031:analogs & derivatives* / Q000032:analysis* / Q000737:chemistry*; D005818:Genetic Engineering; D013058:Mass Spectrometry / Q000379:methods*
C034277:6-deoxyerythronolide B; D004917:Erythromycin