derivatives of preparation method of the (trans) -4-phenyl-l-proline

derivative A process for preparing (trans) -4-phenyl-L-proline, involving the Friedel-Crafts alkylation of benzene with a proline derivative, comprising reacting a proline derivative, formula (CF DRAWING iN BOPI) or proline lactone of formula (CF DRAWING iN BOPI) wherein R is a protecting group for nitrogen, R1 is hydrogen or an aryl, arylalkyl or lower alkyl, and X is a leaving group such as fluorine or mesyl, with benzene, in the presence of a deLewis acid such as aluminum trichloride, to form the derivative of (trans) -4-phenyl-L-proline of formula (CF DRAWING iN BOPI) wherein R1 must be hydrogen when it is proline, which is used as starting material. These derivatives are useful in the preparation of certain angiotensin-converting enzyme.