Assignment of Absolute Configuration to Enantiomers of Anti-Alzheimer Drug Candidate Blarcamesine

Blarcamesine is a promising investigational drug for the treatment of Alzheimer's disease. The international nonproprietary name blarcamesine refers to a racemic compound, although it seems likely that it will be marketed in an enantiopure form. A resolution process has been described in the literature, but the absolute configurations of the enantiomers have not yet been disclosed. In the present study, crystals of (R)-(-)- and (S)-(+)-mandelate salts of (+)- and (-)-blarcamesine and also that of (R)-(+)-blarcamesine itself, suitable for single-crystal X-ray diffraction measurement were prepared and the absolute configurations of (+)- and (-)-blarcamesine have been determined.