Preparation and conformational study of CF3-containing enkephalin-derived oligopeptide

Incorporation of (2S,3S)-4,4,4-trifluorothreonine (F3-Thr) instead of Thr in the enkephalin-derived hexapeptide led to the apparent conformational alteration due to the strong electron-withdrawing effect of the trifluoromethyl group by comparison with the original compound on the basis of their various NMR measurements.