Optical resolution of 2-(2'-hydroxyethylamino)-1-phenylethanol, and the crystal structures of two polymorphic modifications of the (2R,3R)-O,O'-dibenzoyl hydrogen tartrate salt of the (S)-(+)-enantiomer

Successful separation of the enantiomers of 2-(2'-hydroxyethylamino)-1-phenylethanol was achieved using (2R,3R)-O,O'-dibenzoyltartaric acid as a resolving agent. The less soluble salt, (S)-N-(2'-hydroxyethyl)-2-phenyl-2-hydroxyethylammonium (2R,3R)-O,O'-dibenzoyl hydrogen tartrate, was found to crystallize in two polymorphic modifications. The more stable modification is orthorhombic, space group P2(1)2(1)2(1) with cell dimensions a = 8.0096(8), b = 12.0536(13), c = 28.063(4) Angstrom, V = 2709.3(6) Angstrom(3), Z = 4, D-x = 1.323 g cm(-3). X-Ray diffraction data measured at 295.7(5)K with CuK alpha (lambda = 1.541 84 Angstrom) radiation were used for the crystal structure determination, R = 0.0501 for 4951 reflections with I>2 sigma(I). The less stable modification is monoclinic, space group P2(1). X-Ray diffraction data measured at 122.0(5)K conform to a cell of a = 8.0047(8), b = 11.865(2), c = 28.065(5)Angstrom, beta = 91.410(11)degrees, V = 2664.7(7)Angstrom(3), Z = 4, D-x = 1.345 g cm(-3) for CuK alpha (lambda = 1.541 84 Angstrom) radiation. This monoclinic crystal structure was refined to R = 0.0503 for 3233 reflections with I > 2 sigma(I); the two independent ion pairs are almost related by the pseudotranslational symmetry of c/2. Both crystal structures established that the (+)(D) rotation of the 2-(2'-hydroxyethylamino)-1-phenylethanol corresponds to the S enantiomer. The hydrogen bonding scheme is identical in the two modifications, leading to hydrogen bonded sheets. In the monoclinic modification each crystallographically independent ion pair forms separate sheets related by the pseudotranslational symmetry of c/2. A two-fold screw axis parallel to c relates the sheets in the orthorhombic modification.