N-Boc-trans-4-hydroxy-L-prolinol → Trifluoroacetic acid

Participants

Reaction Steps

Formation of the amide bond was carried out using an adaptation of General Method A, above. A mixture of commercially available (2S,4R)-tert-butyl 4-hydroxy-2-(hydroxymethyl)pyrrolidine-1-carboxylate (3.26 g, 15 mmol) in 50 mL of DCM/TFA (3:2, v/v) was stirred at rt for 4 h, concentrated in vacuo to give a brown oil as a crude TFA salt of (3R,5S)-5-(hydroxymethyl)pyrrolidin-3-ol, which was dissolved in DMF (28 mL), added with biphenyl-2-carboxylic acid (3.05 g, 15.4 mmol) and HATU (5.86 g, 15.4 mmol). The resulting solution was cooled to 0° C., added with Et3N (8.8 mL, 63 mmol) dropwise and was allowed to warm to rt gradually and stirred overnight. 2M NaOH (aq.) was added and the mixture was extracted with EtOAc (3×). The combined EtOAc solution was washed with brine, dried over MgSO4 and concentrated in vacuo to a brown oil, which was purified by column chromatography on silica gel (10% MeOH in EtOAc) to provide biphenyl-2-yl((2S,4R)-4-hydroxy-2-(hydroxymethyl)pyrrolidin-1-yl)methanone as an off-white solid (2.0 g, 45% yield over two steps). 1H NMR (CDCl3, 400 MHz) δ 7.59-7.57 (m, 2H), 7.54-7.40 (m, 7H), 4.44 (brs, 1H), 4.10 (s, 1H), 3.77-3.72 (m, 1H), 3.62 (brs, 1H), 3.32 (brs, 1H), 3.04-2.96 (m, 1H), 2.60 (brs, 1H), 2.00-1.95 (m, 1H), 1.61 (brs, 2H). MS (ESI) 298.04 (M+H).

Provenance & Evidence