O-(Benzotriazol-1-yl)-N,N,N',N'-tetramethyluronium tetrafluoroborate → N-[(2R)-2-({[4-((2R,3R)-1-(4-fluorophenyl)-3-{[2-(4-fluorophenyl)-2-hydroxyethyl]thio}-4-oxoazetidin-2-yl)phenoxy]acetyl}amino)-2-phenylacetyl]-L-alanine

Participants

Reaction Steps

(2R)-({[4-((2R,3R)-1-(4-Fluorophenyl)-3-{[2-(4-fluorophenyl)-2-oxoethyl]thio}-4-oxoazetidin-2-yl)phenoxy]acetyl}amino)(phenyl)acetic acid (0.040 g, 0.065 mmol) was dissolved in CH2Cl2 (5 ml). tert-Butyl L-alaninate hydrochloride (0.014 g, 0.078 mmol) and N-methyl-morphiline (0.020 g, 0.195 mmol) were added. After 5 minutes TBTU (0.027 g, 0.084 mmol) was added. The reaction was allowed to stir for 1 h after which the resulting tert-butyl ester was purified by chromatography on silica gel and eluted with EtOAc/CH2Cl2 25/75. Pure fractions were concentrated and dissolved in CH2Cl2 (4 ml) and trifluoroacetic acid (0.5 ml). After 1.5 h at room temperature, full conversion to the corresponding acid was obtained. The reaction mixture was concentrated and the residue of TFA was removed by co-evaporation with toluene (3 ml). The crude acid was dissolved in MeOH (3 ml) and NaBH4-(0.010 g, 0.260 mmol) was added. Full conversion to the corresponding alcohol was obtained after 5 minutes. The reaction was quenched by the addition of 0.1M NH4OAc buffer (1 ml). The mixture was concentrated and the residue was purified by preparative HPLC using a gradient of 20-50% CH3CN in 0.1M NH4OAc buffer as mobile phase. Freeze-drying afforded the title compound (0.020 g, 45%) as a colourless solid. M/z: 688.4 (M−1). 1H NMR [(CD3)2SO), 400 MH] δ 2.30-2.35 (m, 3H), 2.86-2.94 (m, 2H), 3.15-3.31 (m, 1H), 4.26-4.28 (m, 1H), 4.59 (d, 1H), 4.64 (d, 1H), 4.70-4.76 (m, 1H), 5.04-5.07 (m, 1H), 5.46 (d, 1H), 6.94-7.36 (m, 17H), 8.43-8.55 (m, 2H).

Provenance & Evidence