α-Trifluoromethyl α-amino acids were synthesized from β-trifluoromethyl α-ketiminoesters by addition of different Grignard reagents. These racemic α-trifluoromethyl α-amino were converted into diastereomers of (R)-BINOL ester, and these diastereomers were separated by flash column chromatography. Hydrolysis of the esters provided enantiomerically pure α-trifluoromethyl α-amino acids. Then, we synthesized L-leucine peptides with (R)- or (S)-α-trifluoromethyl alanine (α-CF3-Ala) by solution-phase method. Conformational analysis of L-Leu2-[(R)-α-CF3-Ala]- L-Leu2 and L-Leu2-[(S)-α-CF3-Ala]- L-Leu2 revealed that both pentapeptides showed similar 310-helical structures. Therefore, influence of the stereochemistry of α-CF3-Ala on its secondary structure is limited for pentapeptide level.

Synthesis of enantiomerically pure α-trifluoromethyl α-amino acids and conformational studies of their L-leucine-based peptides

254th National Meeting (2017)

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