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Determination of the Stereochemistry of Anhydroerythromycin A, the Principal Degradation Product of the Antibiotic Erythromycin A

Determination of the Stereochemistry of Anhydroerythromycin A, the Principal Degradation Product of the Antibiotic Erythromycin A

Addolreza Hassanzadeh, Madeleine Helliwell, Jill Barber

Org Biomol Chem. 2006 Mar 21;4(6):1014-9.

PMID: 16525545

Abstract:

Anhydroerythromycin A arises from the acid-catalysed degradation of erythromycin A both in vitro and in vivo. It has negligible antibacterial activity, but inhibits drug oxidation in the liver, and is responsible for unwanted drug-drug interactions. Its structure has 18 chiral centres common with erythromycin A, but C-9 (the spiro carbon) is also chiral in anhydroerythromycin and its stereochemistry has not previously been reported; both 9R- and 9S-anhydroerythromycin A are plausible structures. An understanding of the chirality at C-9 was expected to throw light on the mechanism of acid-catalysed degradation of erythromycin A, a subject that has been debated in the literature over several decades. We now report a determination of the three-dimensional structure of anhydroerythromycin A, including the stereochemistry at C-9, by NMR and molecular modelling. In parallel, the relative stereochemistry of anhydroerythromycin A 2'-acetate was determined by X-ray crystallography. Both compounds were shown to have 9R stereochemistry, and anhydroerythromycin A exhibited considerable conformational flexibility in solution.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP23893132	Anhydroerythromycin A		23893-13-2	Price

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