Fluorinated β²- and β³-amino acids: Synthesis and inhibition of α-chymotrypsin

The synthesis of a series of -fluorinated β²- and β³-amino acid derivatives is described. Stereoselective fluorination at the -carbon of the β³-amino acids was achieved by deprotonation with lithium diisopropylamide followed by treatment with N-fluorobenzenesulfonimide. Fluorination of β²-amino acids employed the chiral auxiliary (4R)-4-benzyl-2-oxazolidinone. The α-fluorinated amino acids and their non-fluorinated precursors were found to competitively inhibit α-chymotrypsin.