VERFAHREN ZUR UMKEHRUNG DER KONFIGURATION OPTISCH AKTIVER VERBINDUNGEN UND OPTISCH AKTIVE ZWISCHENPRODUKTE DIESES VERFAHRENS

For the contracting states BE, CH, DE, FR, GB, IT, LI, NL, SE 1. A process for inverting the configuration at the optically active carbon atom (*) in compounds of the formula I see diagramm : EP0102520,P6,F1 in which A represents a cyclopentylphenyl radical and R represents the t-butyl radical, which comprises converting these compounds by formylation into optically active compounds of the formula II see diagramm : EP0102520,P6,F2 in which A and R have the meanings defined above, while maintaining the configuration at the carbon atom (*), converting these compounds, by treatment with a strong acid or an acid halide, into optically active cyclic compounds of the formula III see diagramm : EP0102520,P6,F3 in which A and R have the meanings defined above and in which X**(anion) represents the anion of a strong acid or of a halogen atom, and converting these oxazolinium derivatives (III), by acid or alkaline hydrolysis, if appropriate via the stage of the N-formyl compound, into optically active compounds of the formula IV see diagramm : EP0102520,P7,F4 in which A and R have the meanings defined above, possessing the same structure as the starting material I, but having an opposite configuration at the carbon atom (*). For the contracting state AT 1. A process for inverting the configuration at the optically active carbon atom (*) in compounds of the formula I see diagramm : EP0102520,P7,F1 in which A represents a cyclopentylphenyl radical and R represents the t-butyl radical, which comprises converting these compounds by formylation into optically active compounds of the formula II see diagramm : EP0102520,P7,F2 in which A and R have the meanings defined above, while maintaining the configuration at the carbon atom (*), converting these compounds, by treatment with a strong acid or an acid halide, into optically active cyclic compounds of the formula III see diagramm : EP0102520,P7,F3 in which A and R have the meanings defined above and in which X**(anion) represents the anion of a strong acid or of a halogen atom, and converting these oxazolinium derivatives (III), by acid or alkaline hydrolysis, if appropriate via the stage of the N-formyl compound, into optically active compounds of the formula IV see diagramm : EP0102520,P7,F4 in which A and R have the meanings defined above, possessing the same structure as the starting materail I, but having an opposite configuration at the carbon atom (*).