Solvent-free optical resolution of N-methylamphetamine by distillation after partial diastereoisomeric salt formation

Solvent-free optical resolution of N-methylamphetamine was developed by dis tillation after partial diastereoisomeric salt formation. From the 18 chira l acids tested by this method, five provide by this method resolution: O,O ' -dibenzoyltartaric acid, O,O ' -di-p-toluoyltartaric acid, 6-methoxy-alph a -methyl-2-naphthaleneacetic acid (Naproxen), the cis-permetrinic acid, an d the 2-phenoxypropionic acid. Among them the O,O ' -dibenzoyltartaric acid in water-free form provided the more effective resolution. The efficiency of this resolution S = 0.74, is in the range of the industrial-scale resolu tions and not worse than the efficiency achieved by optical resolution via fractional crystallization. (C) 2001 Wiley-Liss, Inc.