Optiical Resolution of 3-Aminobenzoic Acid Salt of (±)-2-Amino-lphenylethanol by Preferential Crystallization

Abstract

The optical resolution of substituted benzoic acid salts of (±)-2-anino-1-phenylethanol ((±)-APE) by preferential crystallization procedure has been inve stigated. The benzoic acids employed were 2-amino-, 3-amino-, 3-methyl-, 4-methyl-, 2-chloro-, 4-chloro-, 2-nitro-, and 3-nitrobenzoic acids, and benzoic acid. The racemic structures of the (±)-benzoates were examined by comparing their enthalpies of fusion of the (±)-benzoates with those of the corresponding ()-benzoates, the free energies of formation of racemic compound, and the binary phase diagrams of melting point. The results indicated that only (±)-APE salt of 3-aminobenzoic acid ((±)-3-AB salt) is a conglomerate and other (±)-benzoates form a racemic compound. The optical resolution of (±)-3-AB salt was carried out at 10°C in tetrahydrofuran. The (-)-3-AB salt with optical purity of about 90% was obtained wit h degree of resolution of about 60% by adding 0.02 g of seed crystals in a racemic solution with the degree of supersaturation of 200%.