An unambiguous and practical synthesis of Oroxylin A: a commonly misidentified flavone

Abstract

Oroxylin A, a major flavonoid in the extracts of Oroxylum indicum as well as Scutellaria baicalensis possesses useful medicinal properties. Many of the published routes claiming the synthesis of Oroxylin A (1) have in fact led to a regioisomer Negletein that was misinterpreted as Oroxylin A. In the present work, we describe a novel, straight-forward and scalable semi-synthetic approach for rapid access to the title compound, the structure of which is unambiguously secured by NMR and X-ray crystallographic analysis of a derivative. This work also encompasses the synthesis of a glycosylated derivative of Oroxylin A viz OAGME (2), which has marked pharmacological importance.

Graphical Abstract

Keywords:

• Oroxylin A
• Negletein
• Oroxylum indicum
• Scutellaria baicalensis
• semi-synthesis

Disclosure statement

Portions of the results in this manuscript form part of a patent application by the authors.