Synthesis of Kaempferol 3-O-(3,6-Di-O-E-p-coumaroyl)β-D-glucopyranoside, Efficient Glycosylation of Flavonol 3-OH with Glycosyl o-Alkynylbenzoates as Donors

Kaempferol 3-O-(3 '',6 ''-di-O-E-p-coumaroyl)-beta-D-glucopyranoside (1), an optimal metabolite of Scots pine seedlings for protection of deep-lying tissue against damaging UV-B, represents a typical acylated flavonol 3-O-glycoside This compound was synthesized km the first time via two approaches The first approach starting with kaempterol. featured formation or the flavonol 3-O-glycosidic linkage with a glycosyl biomide under conventional PTC conditions In the second approach. 5.7 4'-tri-O-benzyl-kampferol was readily prepared from oxyacetophenone and p-hydroxybenzoic acid, which was coupled with a glucopyranosyl o-hexynylbenzoate under the catalysis of a gold(I) complex to provide the desired 3-O-glycoside in excellent yield A variety of the glycosyl o-hexanylbenzoates equipped with the 2-O-benzoyl group were C also pi oven to he highly efficient donors for construction of the flavonol 3-O-glycosidic linkages