Enzymatic resolution of Cα-fluoroalkyl substituted amino acids

Trifluoromethylated proline analogues as efficient tools to enhance the hydrophobicity and to promote passive diffusion transport of the l-prolyl-l-leucyl glycinamide (PLG) tripeptide

The synthesis of four CF3-proline analogues of the PLG peptide is reported. Our results show that the incorporation of trifluoromethylated amino acids (Tfm-AAs) at the N-terminal position of a peptide significantly increases its hydrophobicity. In addition, depending on the relative configuration and the position of the CF3 group, Tfm-AAs can also promote passive diffusion transport.

Synthesis of protected enantiopure (R) and (S)-α-trifluoromethylalanine containing dipeptide building blocks ready to use for solid phase peptide synthesis

Considering the increasing importance of fluorinated peptides, the development of efficient and reliable synthetic methods for the incorporation of unnatural fluorinated amino acids into peptides is a current matter of interest. In this study, we report the convenient Boc/benzyl and Cbz/tert-butyl protection of both enantiomers of the quaternarized amino acid α-trifluoromethylalanine [(R)- and (S)-α-Tfm-Ala]. Because of the deactivation of the nitrogen atom of this synthetic amino acid by the strong electron withdrawing trifluoromethyl group, the peptide coupling on this position is a challenge. In order to provide a robust synthetic methodology for the incorporation of enantiopure (R)- and (S)-α-trifluoromethylalanines into peptides, we report herein the preparation of dipeptides ready to use for solid phase peptide synthesis. The difficult peptide coupling on the nitrogen atom of the α-trifluoromethylalanines was performed in solution phase by means of highly electrophilic amino acid chlorides or mixed anhydrides. The synthetic effectiveness of this fluorinated dipeptide building block strategy is illustrated by the solid phase peptide synthesis (SPPS) of the Ac-Ala-Phe-(R)-α-Tfm-Ala-Ala-NH2 tetrapeptide.

Fluorine teams up with water to restore inhibitor activity to mutant BPTI

Fluorinated derivatives of aminobutyric acid engage in unique interactions with structural waters within the BPTI/trypsin interface and restore inhibitor activity.

Introducing fluorine into molecules has a wide range of effects on their physicochemical properties, often desirable but in most cases unpredictable. The fluorine atom imparts the C–F bond with low polarizability and high polarity, and significantly affects the behavior of neighboring functional groups, in a covalent or noncovalent manner. Here, we report that fluorine, present in the form of a single fluoroalkyl amino acid side chain in the P1 position of the well-characterized serine-protease inhibitor BPTI, can fully restore inhibitor activity to a mutant that contains the corresponding hydrocarbon side chain at the same site. High resolution crystal structures were obtained for four BPTI variants in complex with bovine β-trypsin, revealing changes in the stoichiometry and dynamics of water molecules in the S1 subsite. These results demonstrate that the introduction of fluorine into a protein environment can result in “chemical complementation” that has a significantly favorable impact on protein–protein interactions.

Synthesis of 2-trifluoromethyl-1,3-oxazolidines as hydrolytically stable pseudoprolines

Trifluoromethyl group containing oxazolidines (Fox) are conveniently synthesized by condensation of serine esters with trifluoroacetaldehyde hemiacetal or trifluoroacetone. These oxazolidines can undergo N-acylation and amidification reactions and are completely configurationally and hydrolytically stable. Therefore, they can be considered as highly valuable proline surrogates (Tfm-pseudoprolines).

Chemical labeling strategy with (R)- and (S)-trifluoromethylalanine for solid state 19F NMR analysis of peptaibols in membranes

Substitution of a single Aib-residue in a peptaibol with (R)- and (S)-trifluoromethylalanine yields two local orientational constraints theta by solid state (19)F NMR. The structure of the membrane-perturbing antibiotic alamethicin in DMPC bilayers was analyzed in terms of two angles tau and rho from six such constraints, showing that the N-terminus (up to a kink at Pro14) is folded as an alpha-helix, tilted away from the membrane normal by 8 degrees, and assembled as an oligomer. The new (19)F NMR label CF(3)-Ala has thus been demonstrated to be highly sensitive, virtually unperturbing, and ideally suited to characterize peptaibols in membranes.

Concise Synthesis of Enantiopure α-Trifluoromethyl Alanines, Diamines, and Amino Alcohols via the Strecker-type Reaction

Diastereomerically pure alpha-trifluoromethyl alpha-amino nitriles obtained by Strecker-type reactions from chiral CF3 imines and iminium proved to be very attractive versatile intermediates for the synthesis of various alpha-trifluoromethyl amino compounds. From these synthons, both enantiomers of alpha-trifluoromethyl alanine, trifluoromethyl 1,2-diamines, and amino alcohols were conveniently obtained in enantiopure form in high yields in a few steps.

A Convenient Enantioselective Synthesis of (S)-α-Trifluoromethylisoserine

[reaction: see text] This report describes two straightforward synthetic methodologies to obtain alpha-CF3-isoserine, a new alpha,alpha-disubstituted beta-amino acid, from alpha-(trifluoromethyl)acrylic acid. The routes involve the synthesis of five-membered cyclic sulfates (using sulfuryl chloride) or sulfamidates (using the Burgess reagent) from the corresponding chiral diols, which are obtained by a catalytic asymmetric dihydroxylation (AD) reaction.