PURPOSE: To obtain the subject compound which is a synthetic intermediate for neurontransmitters, antitumor substances, etc., in high optical purity, by bringing a specific carbonyl compound into contact with a reducing agent complex prepared by including a reducing agent in cyclodextrin using a readily available and inexpensive raw material.

CONSTITUTION: A reducing agent complex prepared by including a reducing agent in cyclodextrin in a powdery form is directly dispersed in a supersaturated aqueous solution of various inorganic salts or organic solvent by cutting off light and a carbonyl compound having an optional organic residue without interfering reductive reaction is added and reacted therewith at -60W90°C, preferably -20W50°C for 5W100hr to afford the aimed compound. Furthermore, the reducing agent used is preferably a Lewis base complex of borane. The clathrate compound of the reducing agent is obtained by, e.g., adding water (in an amount of about 0.1W6 times based on the cyclodextrin) to the cyclodextrin and kneading the resultant pasty mixture with a reducing agent compound to be included.