One-step and regioselective acylation of flavonoid glucosides was achieved by lipase-catalyzed transesterification in dry organic media. For example, isoquercitrin (quercetin 3-O-glucoside), one of the flavonol monoglucosides, was converted efficiently to the corresponding aromatic acid ester (isoquercitrin 6"-O-cinnamate) by a lipase with vinyl cinnamate as an acyl donor. The method described, which is the first allowing the direct synthesis of aromatic acid esters of flavonoid glucosides, can be applied to the acylation of other glucosides, including naringin, rutin, callistephin, and chrysanthemin.