Acetic Acid → (2S,4R)-1-[3-(5-Bromo-3-fluoro-pyridin-2-yl)-1-methyl-azetidine-3-carbonyl]-4-(2-chloro-benzenesulfonyl)-pyrrolidine-2-carboxylic acid (1-cyano-cyclopropyl)-amide

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Reaction Steps

To a mixture of example 13 (0.05 g, 81.8 μmol, Eq: 1.00), sodium acetate (14.8 mg, 180 μmol, Eq: 2.2) and acetic acid (10.8 mg, 10.3 μl, 180 μmol, Eq: 2.2) in dichloromethane (0.5 ml) was added at 25° C. aqueous formaldehyde solution (36%; 19.1 mg, 17.5 μl, 229 μmol, Eq: 2.8). The mixture was stirred for 45 min, then sodium triacetoxyborohydride (55.5 mg, 262 μmol, Eq: 3.2) was added in one portion at 0-5° C. The cooling bath was removed after 10 min and stirring was continued at 25° C. for further 18 h. The reaction mixture was quenched with aqueous 0.5 M NaOH-solution (2 ml), stirred for 2 min, then the layers were separated. The aqueous layer was extracted with three portions of AcOEt (each 5 ml). The combined organic layers were washed with brine, dried over Na2SO4 and concentrated in vacuo. The crude material was purified by preparative HPLC to yield the title compound as a colorless amorphous solid (0.0206 g; 40%). m/z=626.1 [M+H]+.

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