| abstract |
The invention relates to a novel process for preparing the optical isomers of 2,2-dimethyl-3-(2,2-disubstituted vinyl)cyclopropanecarboxylic acids of general formula (I), wherein R?1 and R2¿, independently from another, stand for halogen or a C¿1-4?alkyl group. The process of the invention comprises reacting a racemic compound of general formula (I), wherein R?1 and R2¿ are as defined above, or a salt thereof with a phenylglycine derivate of general formula (II), wherein R3 means a cyano or carboxamide group, or an acid addition salt thereof, separating the member of the diastereoisomeric salt pair, which precipitates in crystalline form, in a manner known per se and liberating by an acid therefrom the optically active acid of general formula (I) containing (1S) configuration when R3 in the compound of general formula (II) used means cyano group, or the optically active acid containing (1R) configuration, respectively, when R3 in the compound of general formula (II) used means carboxamide group, repeating, if desired, this operation 1 to 5 times, recovering the diastereoisomeric salt remaining in the mother liquor in a manner known per se and obtaining therefrom the optically active antipode acid of general formula (I) in a manner known per se. |