FLUORINATED AMINO-ACIDS AND PEPTIDES - SYNTHESIS OF 3,3-DIFLUORO-2-AMINO ACIDS, PEPTIDES AND CYCLODIPEPTIDES INCORPORATING 3,3-DIFLUORO-2-AMINOBUTYRIC ACID OR 3,3-DIFLUOROPHENYLALANINE RESIDUES IN THEIR STRUCTURES

Convenient syntheses have been developed for N-9-fluorenylmethyloxycarbonyl-DL-2-amino-3,3-difluoro-butanoic acid and N-9-fluorenylmethyloxycarbonyl-DL-3,3-difluorophenylalanine which have been successfully introduced into peptide syntheses. Several fluorinated peptides have been obtained either by active ester coupling methods, mixed anhydride synthesis or with the aid of dicyclohexylcarbodiimide (DCC) in presence of 1-hydroxybenzotriazole (HOBt). The method has been applied to the preparation of seven hitherto unpublished representative 3-(1,1'-difluoroalkyl)-2,5-dioxopiperazines for biological purposes and structural chemistry studies.