- An unambiguous and practical synthesis of Oroxylin A: a commonly misidentified flavone
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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.
- Hemantha, Hosahalli P.,Ramanujam, Rajendran,Majeed, Muhammed,Nagabhushanam, Kalyanam
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p. 1413 - 1420
(2019/08/22)
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- PROCESS FOR SYNTHESIS OF OROXYLIN A
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Disclosed is a novel, simple, scalable and environment friendly process for the synthesis of Oroxylin A from Baicalin. Baicalm is esterified to obtain a methyl ester which is further selectively methylated to provide Oroxylin A gluciironide methyl ester w
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Page/Page column 7; 14
(2020/03/02)
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- Crystal structures of the flavonoid Oroxylin A and the regioisomers Negletein and Wogonin
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The flavonoid Oroxylin A (6-methoxychrysin or 5,7-dihydroxy-6-methoxy-2- phenyl-4H-chromen-4-one, C16H12O5) and its regioisomers are of increasing interest for a variety of bioactive functions and their pharmaceutical formulation is of importance. Previous difficulties in the separation and misidentification of Oroxylin A from its regioisomers Wogonin (8-methoxychrysin or 5,7-dihydroxy-8-methoxy-2-phenyl-4H-chromen-4-one) and Negletein (5,6- dihydroxy-7-methoxyflavone or 5,6-dihydroxy-7-methoxy-2-phenyl-4H-chromen- 4-one) render its full structural and powder X-ray characterization highly desirable. The low-temperature (100 K) crystal structures of Oroxylin A, Negletein and Wogonin sesquihydrate are reported for the first time. Wogonin crystallizes in two related but distinct hydrated forms. These have very similar powder diffractograms, indicating that such issues need to be addressed for its pharmaceutical formulation.
- Grano, Ruel Valerio Robles De,Nisar, Madiha,Sung, Herman H.-Y.,Vashchenko, Elena V.,Vashchenko, Valerii V.,Williams, Ian D.
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p. 490 - 499
(2020/05/18)
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- Process for synthesis of Oroxylin A
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Disclosed is a novel, simple, scalable and environment friendly process for the synthesis of Oroxylin A from Baicalin. Baicalin is esterified to obtain a methyl ester which is further selectively methylated to provide Oroxylin A glucuronide methyl ester which on de-glycosylation results in the formation of Oroxylin A.
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Page/Page column 4; 13
(2019/09/23)
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