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This thesis deals with new methods for the synthesis of (chiefly unnatural) amino acids. A general survey of common methods for the synthesis of amino acids is given in Chapter 1. In Chapter 2 a new approach is described wherein glycine esters, further activated as the Schiff bases by condensation with an aldehyde or ketone, are allowed to react with various Michael acceptors. This route has been employed to synthesize various 5-substituted and 3,5-disubstituted prolines by subsequent ring-closure of the Michael adducts. ' In Chapter 3 the Schiff bases of glycine esters are allowed to react with aldehydes to form R-hydroxy-a-amino acid derivatives. The procedure involves in situ formation of a silyl ketene derivative by silylation of the enolate. Reaction with an aldehyde in the presence of a catalytic amount of ZnC1, affords chiefly the syn adducts; use of stoichiometric amounts of ZnC1, leads to a predominance of anti adduct. A tentative explanation is given for this result. Chapters 4 and 5 are devoted to tne synchesis of a-ally1 substituted a-amino acids by means of a palladium catalyzed rearrangement (Carroll rearrangement) of the ally1 esters of the a-amino acids protected/activated as their Schiff bases. The metal catalyzed rearrangement occurs smoothly with the enolates; a pronGnced effect of counterion of the enolate is observed, however.The thesis is written in English. The major goal of this thesis was to develop catalytic methods for the synthesis in optically pure form of new a-hydroxy acid derivatives of synthetic and/or medicinal interest. Catalytic enantioselective synthesis was envisaged using transition metals provided with designed optically active ligands.hydroxy acids as well as various target compounds is given in Chapter 1. 1n.Chapter 2 the results of the catalytic alkylation of the dioxolanones derived by condensation of commercially available a-hydroxy acids (lactic and mandelic) with acetone (acid catalyzed exchange with 2,2-dimethoxypropane) with n-ally1 complexes of Pd(0) are given. The catalytic reaction proceeds extremexy well. with excellent tolerance for structural variation in the allylic acetate used to form the n-ally1 complex. Results using optically ligands were more disappointing, however. Various relations are laid becween cne scructure of Optically active llgands and the enantiomeric excesses of the derived coupling products. The best result obtained was a 35% enantiomeric excess.nation of enantiomeric excesses by examination of the NMR spectra of the coupling products of the a-hydroxy acids with S-2-chloropropionyl chlorides obtained by diazotization of Salanine. This method is simple, reliable, and can be applied widely.In Chapters 4 and 5 pig liver esterase '(PLE) is examined for the kinetic resolution of the esters of the newly made ahydroxy acids. Excellent results (up to -85% enantiomeric excess) were obtained in the mandelic acid series. An empirical model for PLE is examined by comparing structures and kinetic parameters of the ester substrates with the steric predi...