Semduramicin, structure

LC-ISP-MS proved to be an attractive approach for the determination of semduramicin in chicken liver (120). Tandem MS using CID of the molecular ions could further enhance the specificity, providing structure elucidation and selective detection down to 30 ppb under SRM conditions. 

The C-30 skeleton group accounts for about 60% of the polyethers for which structures have been determined. Most of these contain a sugar moiety, usually 2,3,6-trideoxy-4-0-methyl-D-erythro pyranose [65104-53-2], The single spiroketal subset is illustrated by two closely related compounds, semduramicin (4, R = H, R =) and maduramicin alpha (4, R = CH3, R/ = ). Maduramicin is marketed as an anticoccidial and semduramicin is under development for the same application. 

Confirmation of the Identities of Metabolites and F by IH-NMR. Metabolites E and F of semduramicin were isolated in sufficient quantity to obtain IH-NMR spectra and to characterize structural changes based on observed differences with the parent structure. Although the most intense signals were from "experimental background , the spectral intensity of the two methoxy methyl groups was sufficiently clear to permit unambiguous assignment. 

Likewise, analysis of the spectrum of metabolite "F showed the methyl singlet at 3.36 ppm intact suggesting loss of the ether linked methyl at position 45. Loss of the apparent triplet at 3.11 ppm (proton in position 6 of semduramicin) and the presence of a seemingly unchanged multiplet at 2.81 ppm (similar to proton in position 41 of semduramicin) supported this interpretation. Thus, the structures postulated for metabolites E and F by mass spectrometric analysis were confirmed by IH NMR. 

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