A process capable of conveniently preparing voglibose at a low cost in a safe process, and an intermediate which can be suitably used in the process and a process for preparing the intermediate are provided. An inositol derivative represented by the formula (VI):
wherein Prt is a protecting group of hydroxyl group; a process for preparing the inositol derivative, wherein a cyclohexanone compound represented by the formula (IV):
wherein Prt is as defined above,
is dihydroxyaminated using a dihydroxyaminating agent and a reducing agent; and a process for preparing voglibose represented by the formula (VIII):
wherein the inositol derivative is oxidized to give an inositol compound, and the protecting group, Prt of the inositol compound is deprotected.