CRYSTAL-STRUCTURES OF ANALOGS OF THREO-METHYLPHENIDATE

The crystal structures of the chloride salts of five analogs of threo- methylphenidate have been obtained. Four of these have different subst ituents on the phenyl ring while the fifth is the ethyl ester of methy lphenidate. All five structures have similar three-dimensional conform ations and these are compared with the global minimum obtained by MM2- 87 calculations. There is good agreement between the crystal structure s and the computed global minimum with the major difference being the presence of a chloride counterion in the crystal structures that preve nts the carbonyl oxygen from approaching the equatorial ammonium hydro gen as closely as in the computed global minimum.