To obtain amines having a configuration under industrially practicable reactional conditions by reducing a solution of a specific compound in the presence of a boron compound with a reducing agent.

(A) A solution of a compound represented by formula I [R1 and R2 are each H or a 1-10C alkyl; R3 is a protecting group of hydroxyl group such as acetyl or benzyl; R4 is a (protecting group-substituted) amino] is subjected to reduction in the presence of (B) a boron compound with (C) a reducing agent to reduce the compound represented by formula I into an amine having a configuration represented by formula II [R'1 and R'2 are each H or a 1-10C alkyl; R'3 is a protecting group of the hydroxyl group such as acetyl or benzyl; R'4 is a (protecting group-substituted) amino]. A boric acid ester, an alkylboron or an arylboron is cited as the component B and a compound represented by the formula BR'5 (R'5 is a 1-3C alkoxyl or an aromatic oxyl, a 1-5C alkyl or an aryl) is specifically cited. An aluminum-based hydride is preferred as the component C.