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An example of a solvent-driven [alpha]/[3.sub.10]-helix dimorphismis described for a peptide molecule in the crystalline state. The studies have shown that the interconversion between [alpha]- and [3.sub.10]-helices might be allowed even in peptides composed by [C.sup.[alpha]]-tetrasubstituted [alpha]-amino acids and has provided clues for understanding the interactions of 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP) with helical peptides.

The purification, cloning and heterologous expression in Escherichia coli of the L-specific amidase from Ochrobactrum anthropi NCIMB 40321 wild-type cells are described. The results have shown that this amidase is responsible for the remarkably relaxed substrate specificity of this microorganism.

The asymmetric aldol condensation of acetone with isatin, its N-alkylated derivatives, and 5-` is described. A new quaternary stereocenter is obtained with good enantioselectivity, which can easily be enriched by silica flash chromatography and the effect proved to be general for the class of compounds.

A set of analogues and dipeptide amides characterized by chiral C(super alpha)-tetrasubstituted alpha-amino acids of varied bulkiness and optical configurations are examined. Results confirm the close relationship between the beta-hairpin 3D-structure and the catalytic activity of the peptides.

Super-cells containing different ratios of resolving agents in the diastereomeric salts are constructed and optimized and their lattice energy is computed as well as the energy difference between these simulated solid solutions and the native structures are related in an understandable fashion to the probability of solid solution formation. This is applied to a family of diastereomeric salts of ephedrine and cyclic phosphoric acids.

Research has been conducted on the N-protected alpha-amino acid bromides. Results indicate that these compounds have been generated under mild conditions from the corresponding amino acids.

Research has been conducted on the short peptide frameworks for the catalyst construction. The fluorination reaction with the tetramethylfluoroformamidinium hexafluorophosphate has been investigated and the reactivity of the C (super)alpha -tetrasubstituted amino acids has been analyzed.

A study was made on the synthesis of alpha-substituted alpha-amino acids using highly electrophilic iminium ions, bearing carbonyl substituents as key cationic intermediates. Numerous alpha-substituted precursors were employed to assess the generality of the approach and to determine the reaction mechanism. The results indicated that CC-bond formation can be made using the cationic intermediates but proton loss from the intermediate is a key side reaction. Further studies are encouraged on other alpha-substituents and the development of an asymmetric version of the synthetic approach for the alpha-phenyl-substituted compounds.

The synthesis of saturated and gamma,delta-unsaturated alpha-amino acids with mediation of boron trifluoride etherate in reactions of alpha-methoxyglycine amide derivatives with allysilanes were investigated. The formation of alpha-methoxyglycine esters followed the S(sub N)1-type mechanism. The coupling reactions of alpha-methoxyglycine amide and its N-substituted derivatives with allylsilanes were presented and the products protected by allyloxycarbonyl groups and transprotected by Pd(0)-catalyzed reactions.

A study of unprotected and differently protected (at the NH2, COOH or both) amino acids reveals their racemization behavior in their reactions with sulfur-based (R-S-H) radicals. The study shows that, apart from the dependence of racemization on the type of protection and on the R-S-H character, the yield (64-100%) depends critically on the solvent system, which must completely dissolve both the AA and the RSH for optimum results. Unsaturated AAs such as alpha-allylglycines can serve as common intermediates in the synthesis of these optically active trifunctional AAs.

The experimental proof-of-concept is presented for the emergence of the single solid-phase chiral state for an intrinsically chiral molecule starting from a racemic mixture of enantiomorphic crystals. The results have shown that the concept of attrition-enhanced solid-phase enantioenrichment is extended from simple achiral salts to include biologically relevant enantiomeric molecules.