Spontaneous Stereoselective Oxidation of Crystalline Avermectin B 1a to Its C-8a-( S )-Hydroperoxide

Prolonged storage of technical abamectin as well as avermectin B samples yielded a previously unknown derivative, designated here as compound . Detailed NMR analysis and X-ray crystallography allowed us to determine the structure of this compound and revealed the presence of a hydroperoxide group (-...

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Bibliographic Details
Published in:Journal of natural products (Washington, D.C.) D.C.), 2019-12, Vol.82 (12), p.3477-3481
Main Authors: Gliński, Jan A, Proudfoot, John, Madura, Izabela, Zhang, Huaping, Gleńsk, Michał, Day, Victor, Dudek, Marta K
Format: Article
Language:English
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Summary:Prolonged storage of technical abamectin as well as avermectin B samples yielded a previously unknown derivative, designated here as compound . Detailed NMR analysis and X-ray crystallography allowed us to determine the structure of this compound and revealed the presence of a hydroperoxide group (-OOH) attached stereoselectively with configuration to the C-8a carbon. This surprising result involves the formation of the peroxide bond in solid crystalline avermectin B upon exposure to air with no involvement of light or recognized catalytic factors and is consistent with a topotactic mechanism for the oxidation reaction. Compound is stable in the absence of reducing agents and has potential as a starting point in structural modification of the tetrahydrofuran ring of avermectin B . It could also serve as a marker in assessing the quality of stored technical abamectin.
ISSN:0163-3864
1520-6025
DOI:10.1021/acs.jnatprod.9b00524