Racemic trans 3-(9-fluorenylmethyloxycarbonylamino)-1-oxyl-2,2,5,5-tetramethylpyrrolidine-4-carboxylic acid (Fmoc-POAC-OH), prepared by conventional methods, was resolved upon esterification with (a R)-2,2′-dihydroxy-1,1′-binaphthyl. Separation of the obtained diastereomeric monoesters Fmoc-(±)- trans-POAC- O-(a R)-binaphthol by crystallization/chromatography, and removal of the chiral auxiliary by saponification of the aryl ester function furnished both enantiomers (+)-(3 R,4 R)-Fmoc-POAC-OH and (−)-(3 S,4 S)-Fmoc-POAC-OH. The absolute configuration of the asymmetric C 3, C 4 carbons of POAC were assigned from the induced circular dichroism of a flexible biphenyl probe present in the terminally protected dipeptide derivatives Boc-Bip-(+)-POAC-OMe and Boc-Bip-(−)-POAC-OMe (Bip, 2′,1′:1,2;1″,2″:3,4-dibenzcyclohepta-1,3-diene-6-amino-6-carboxylic acid). This assignment was confirmed by X-ray diffraction analysis of the diastereomeric monoester Fmoc-(+)- trans-POAC- O-(a R)-binaphthol, shown to be (a R,3 R,4 R). Solution synthesis of peptides to the hexamer level, based on the (3 R,4 R)-POAC enantiomer combined with (1 S,2 S)-2-aminocyclopentane-1-carboxylic acid, was carried out to examine coupling conditions at both C- and N-termini of the POAC residue, in view of further syntheses and 3D-structural investigations.