How do you Synthesise Glycosides of flavonoids and stilbenoids?
I suggest to forget about the enzymes.

Pepare for a probably lengthy synthesis - you will need patience and a clever protection/deprotection scheme.

The following is definitely not applicable to all starting materials but might give some directions.



If the flavonoid contains a catechol moiety, just like quercetin (1), the vicinal phenolic $\ce{OH}$ groups can be protected as an acetal by heating the starting material with $\alpha,\alpha$-dichlordiphenylmethane in diphenylether (DOI). The protecting groups is easily removed by hydrogenation over $\ce{Pd/C}$ at 1 atm.

Note that the PMB (4-methoxybenzyl) group is another protecting group for (phenolic) $\ce{OH}$ that gets off by hydrogenation. 

As far as selectivities for the protection of the other $\ce{OH}$ groups in 1 are concerned, have a look at the 1962 paper by Leonard Jurd, who described that the methylation of quercetine pentaacetate in dry acetone predominantly furnishes 7-O-methylquercetin. There are quite some more recent articles citing this!