Trifluoroacetic acid → N-{[4-((2R,3R)-1-(4-fluorophenyl)-3-([2-(4-fluorophenyl)-2-hydroxyethyl]thio}-4-oxoazetidin-2-yl)phenoxy]acetyl}-D-serine

Participants

Reaction Steps

A solution of [4-((2R,3R)-1-(4-fluorophenyl)-3-{[2-(4-fluorophenyl)-2-oxoethyl]thio}-4-oxoazetidin-2-yl)phenoxy]acetic acid (0.050 g, 0.103 mmol), O-(tert-butyl)-D-serine tert-butyl ester hydrochloride (0.032 g, 0.147 mmol) and N-methylmorpholine (0.035 ml, 0.318 mmol) in DCM (4 ml) was stirred for 5 min. TBTU (0.044 g, 0.137 mmol) was added. The formation of the ester was confirmed after 3 h. M/z: 683.1. TFA (2 ml) was added and the mixture was stirred for 22 h. The solvent was removed under reduced pressure. The residue was dissolved in MeOH (4 ml) and NaBH4 (totally 0.130 g, 3.44 mmol) was added in small portions. The reaction was quenched by the addition of 0.1M ammonium acetate buffer (3 ml). The methanol was removed under reduced pressure. The remaining solution was purified by preparative HPLC using a gradient of 20-60% MeCN in 0.1M ammonium acetate buffer as eluent. After freeze-drying, 0.021 g (36% yield) of the title product was obtained as a white solid. M/z: 573.1. 1H NMR (DMSO, 400 MHz): δ 2.84-2.96 (m, 2H), 3.47 (dd, 1H), 3.69 (dd, 1H), 3.97-4.06 (m, 1H), 4.27-4.32 (m, 1H), 4.52 (ABq, 2H), 4.68-4.77 (m, 1H), 5.04-5.09 (m, 1H), 5.65 (bs, 1H), 6.99 (d, 2H), 7.07-7.41 (m, 10H), 7.89 (d, 1H).

Provenance & Evidence