To readily produce a threo-1,2-diaryl-1,2-ethanediol derivative useful as a raw material for a source of asymmetry in an asymmetric synthesis reaction under a mild condition by reacting an alkali metal alkoxide on an erythro-1,2-diaryl-1,2-ethanediol derivative in a nonprotonic solvent to isomerize the derivative.

An erythro derivative of formula I [R1 and R2 are each a (substituted) aryl; R3 and R4 are each an acyl or H; R1 and R2, R1 and R3, R1 and R4, R2 and R4, and R3 and R4 may form a cyclic structure by binding to each other], (e.g. erythro-1,2-diphenyl-1,2-ethanediol) is reacted in a nonprotonic solvent (,e.g. tetrahydrofuran) by adding an alkali metal alkoxide (e.g. potassium t-butoxide) at 0-150°C for 30 min to 24 hr to provide the objective threo derivative of formula II.