m), 980 (w), 905 (w), 860 (w), 830 (w) cm-I; HRMS calcd for CZ4-H,,N305 (M + H) 444.251, found 444.247. Compound 22 can be obtained from 20b by using same procedure, and all the physical and spectral data are identical. Cyclo[N-[ 3-[4 (2-(Z )-aminoviny I) phenoxy) (2S,3S)-prolyl]-( S ) -isoleucyl] (23). To a solution of compound 22 (0.0580 g, 0.139 mmol) andthioanisole (0.173 g. 1.39 mmol) in methylene chloride (3 mL) at 5 'C was added trifluoroacetic acid (TFA) (0.316 g, 2.78 mmol). After 5 h, the reaction was diluted with methylene chloride (10 mL) and made basic with a saturated sodium bicarbonate solution (20 mL). The organic layer was separated and extracted with a 5% citric acid solution (2 mL, twice), and the aqueous layers were combined. The aqueous layer was made basic with a saturated NaHCO, solution, extracted with methylene chloride (20 mL, five times), dried over Na2S04, and filtered, and the filtrate was concentrated under reduced pressure to provide pure 23 (0.0130 g, 28% yield): R~0.52 (methylene chloride:ethanol90:10); [a]"D J = 6.9), 0.84-0.90 (3 H, m), 0.91-0.98 (1 H, m), 1.21-1.33 (1 H, m), 2.07-2.13 (1 H, m), 2.17-2.18 (2 H, m), 2.35-2.43 (1 H, m), 3.04-3.09 (1 H, m), 3.23-3.24 (2 H, m), 4.22-4.25 (1 H, m), 5.18-5.22 (1 H, m), 5.55 (1 H, d, J = 9.
