PURPOSE: To obtain the titled erythro-derivative, useful as pharmaceuticals for the circulatory system, exclusively, in high selectivity, easily, and economically, by reducing an α-aminopropiophenone derivative in the form of salt or in the presence of an acidic substance, with HaBH 4 .
CONSTITUTION: An α-aminopropiophenone derivative of formula I (X is H, OH, benzyloxy, or halogen; R 1 and R 2 are H, 1W6C alkyl, aralkyl, or R 1 and R 2 together with a 4W6C group form a nitrogen-containing ring) is reduced in the form of salt or in the presence of an acidic substance (e.g. hydrochloric acid, acetic acid, etc.) with NaBH 4 to give erythro-2-amino-1-phenylpropanol derivative of formula II.
EFFECT: The reduction of the hydrochloride of the propiophenone derivative gives the erythro-isomer in an extremely high selectively (erythro/threo is 96.6%/0.2%), in contrast with the reduction of the derivative in the form of free base, in which the ratio of the threo-isomer or the undesirable type of the steric isomers, becomes high.