反应详情

To a solution of (4-amino-4,5,6,7-tetrahydro-indazol-1-yl)-acetic acid ethyl ester (60 mg, 0.27 mmol) in 5% sodium carbonate (0.57 mL) and 1,4-1,4-dioxane (1 mL) was added benzyl chloroformate (58 uL, 0.40 mmol) at 0° C. The reaction mixture was allowed to warm to room temperature slowly, and stirred overnight. The reaction mixture was partitioned between water (10 mL) and dichloromethane (20 mL×3). The combined organic layers were collected and dried over sodium sulfate, filtered and concentrated in vacuo. The residue was purified by column chromatography (50% ethyl acetate in hexanes) to afford racemic (4-benzyloxycarbonylamino-4,5,6,7-tetrahydro-indazol-1-yl)-acetic acid ethyl ester (94.2 mg, 98.2%) as a white solid. 1H NMR (400 MHz, CDCl3) δ ppm 7.54 (s, 1 H), 7.49-7.35 (m, 4 H), 5.18 (s, 2 H), 5.23 (s, 2 H), 4.92-4.80 (m, 3 H), 4.23 (dd, J=7.2 Hz, 2 H), 2.52 (m, 2 H), 2.05-1.88 (m, 4 H), 1.30 (t, J=7.2 Hz, 3 H). MS calcd. for C19H23N3O4 357, obsd. (ESI+) [(M+H)+] 358. The chrial separation (Gilson instrument: column: AS-H; flow rate: 15 mL/min; gradient: 55% hexane in propan-2-ol) gave ((R)-4-benzyloxycarbonylamino-4,5,6,7-tetrahydro-indazol-1-yl)-acetic acid ethyl ester (retention time 7.2 minutes) and ((S)-4-benzyloxycarbonylamino-4,5,6,7-tetrahydro-indazol-1-yl)-acetic acid ethyl ester (retention time 8.7 minutes). The recovery for both isomers together was 70%.

1. customThe reaction mixture was partitioned between water (10 mL) and dichloromethane (20 mL×3)
2. customThe combined organic layers were collected
3. dry with materialdried over sodium sulfate
4. filtrationfiltered
5. concentrationconcentrated in vacuo
6. customThe residue was purified by column chromatography (50% ethyl acetate in hexanes)