Trifluoroacetic acid → (4R)-4-(Benzyloxy)-1-{[(9H-fluoren-9-yl)methoxy]carbonyl}-L-proline

Participants

Reaction Steps

To a solution of (2S,4R)-4-(benzyloxy)pyrrolidine-2-carboxylic acid, TFA (522 mg, 1.557 mmol) in 1,4-dioxane (4 mL) and water (16 mL) was added potassium carbonate (861 mg, 6.23 mmol) followed by (9H-fluoren-9-yl)methyl carbonochloridate (403 mg, 1.557 mmol) at 0° C. The mixture was stirred at RT for 18 hrs and treated with water (10 ml). The resulting mixture was extracted with diethyl ether (2×15 ml). The aqueous phase was acidified with aq. HCl (1M) to pH 2-3, and extracted with DCM (3×20 ml). The combined organic layers were dried over MgSO4 and concentrated to give the crude product. The crude product was purified via prep HPLC (10-100% CH3CN:Water 0.1% TFA buffer) to afford the pure product (2S,4R)-1-(((9H-fluoren-9-yl)methoxy)carbonyl)-4-(benzyloxy)pyrrolidine-2-carboxylic acid (430 mg, 62.3% yield) as a white solid. 1H NMR (500 MHz, methanol-d4) d 7.86-7.76 (m, 2H), 7.71-7.57 (m, 2H), 7.44-7.27 (m, 9H), 4.58-4.50 (m, 2H), 4.49-4.33 (m, 3H), 4.29-4.19 (m, 2H), 3.72-3.49 (m, 2H), 2.49 (br. s., 1H), 2.10 (ddd, J=13.4, 8.2, 4.8 Hz, 1H). ESI-MS (+) m/z=444 (M+H).

Provenance & Evidence