Convergent synthesis of a trisaccharide as its 2-(trimethylsilyl)ethyl glycoside related to the flavonoid triglycoside from Gymnema sylvestre

The glycone part of the flavonoid triglycoside, kaempferol 3-O-β-d-glucopyranosyl-(1→4)-α-l-rhamnopyranosyl-(1→6)-β-d-galactopyranoside, has been synthesized in good yield and stereoselectivity using N-iodosuccinimide and HClO4–silica promoted glycosylations of thioglycoside donors.