A solution of rhodanine-3-acetic acid (461 mg, 2.41 mmol, 1 eq), 3-[(S)-1-phenyl-2,2,2-trifluoroethoxy]-4-[(S)-2-phenylpropoxy]benzaldehyde (1.0 g, 2.41 mmol, 1 eq) and ammonium acetate (558 mg, 7.24 mmol, 3 eq) in N,N-dimethylformamide (10 mL) was heated to 90° C. and stirred for 15 min. It was then cooled to room temperature and diluted with ethyl acetate (100 mL). The organic solution was washed with 1M HCl (2×200 mL), and brine (200 mL), then dried over sodium sulfate and evaporated. The residue was purified by chromatography on silica gel; elution with ethyl acetate followed by ethyl acetate:methanol (9:1) gave a yellow gum which was dissolved in methanol (5 mL) and added dropwise to stirred ice-cold water (100 mL). A fine suspension was obtained, which was freeze-dried over 3 days to give the product as a yellow powder (1.04 g, 73%) mp 73–80° C.: 1H NMR (d6 DMSO) δ 7.64 (s, 1H, C═C—H), 6.04 (q, 1H, J 6.4 Hz, CHCF3), 4.61 (s, 2H, CH2CO2H), 4.22 (m, 2H, OCH2CHCH3Ph), 3.26 (m, 1H, OCH2CHCH3Ph), 1.38 (d, 3H, J 7.2 Hz, OCH2CHCH3Ph) 19F NMR (d6 DMSO) −75.80. Anal. Found: C, 59.31; H, 4.42; N, 2.36; Calcd for C29H24F3NO5S2: C, 59.27; H, 4.12; N, 2.38.
