163395-93-5Relevant academic research and scientific papers
Glycosyl Imidates, 69. - Synthesis of Flavone C-Glycosides Vitexin, Isovitexin, and Isoembigenin
Mahling, Juergen-Andreas,Jung, Karl-Heinz,Schmidt, Richard R.
, p. 461 - 466 (2007/10/02)
2-Hydroxy-4,6-dimethoxyacetophenone (4) was glycosylated with O-(2,3,4,6-tetra-O-benzyl-α-D-glucopyranosyl) trichloroacetimidate (5) and trimethylsilyl triflate as promoter to yield directly the C-glycoside 6.Construction of the flavone system by application of a Baker-Venkataraman-type rearrangement followed by deprotection yielded isoembigenin (2).Glycosylation of 4,6-bis(tert-butyldimethylsilyloxy)-2-hydroxyacetophenone (17) with the trichloroacetimidate 5 afforded the O-glycoside intermediate 18 which was converted via Fries rearrangement into the C-glycoside 21.Applying again the Baker-Venkataraman rearrangement and cyclization gave isovitexin and vitexin derivatives 25 and 26, which were completely deprotected to yield isovitexin (1b) and vitexin (1a), respectively. - Key Words: Glycosides / Flavones / Vitexin / Isovitexin / Isoembigenin / Carbohydrates / Trichloroacetimidates / Fries rearrangement / Baker-Venkataraman rearrangement
