Trifluoromethyl-substituted imidazolines: novel precursors of trifluoromethyl ketones amenable to peptide synthesis

A 1,3-dipolar cycloaddition reaction between an azomethine ylide and dipolarophile was performed to synthesize trifluoromethyl ketones (TFMK) via 4-trifluoromethyl-substituted delta(sup 3)-imidazolines. The latter, which acts as a protected form of TFMKs, were incorporated into peptides through standard Fmoc-peptide synthesis methods using Carpino's carbamate-protected amino acid fluorides. This was followed by hydrolization with mild acid to produce the desired TFMKs.