Synthesis of 17-OH-Isosteviol

Stevioside(1), an ent-kaurene glycoside commer-cially extracted from Stevia rebaudiana Bertoni[1] is used as a non-caloric sweetener for food in many countries[2]. The increasing demand for low calory and natural food contributes to the increasing popularity of that glycoside[3]. It has recently been demonstrated that stevioside and its derivatives have inhibitory ef-fects on the inflammatory ear edema of mice and sup-press the tumor-promoting effect in mouse skinl[4].