[C:1]([O:5][C:6]([N:8]1[C@@H:17]([C:18](O)=[O:19])[CH2:16][C:15]2[C:10](=[CH:11][CH:12]=[CH:13][CH:14]=2)[CH2:9]1)=[O:7])([CH3:4])([CH3:3])[CH3:2].C(N(CC)CC)C.ClC(OCC)=O.[BH4-].[Na+]>C1COCC1.CO>[OH:19][CH2:18][C@H:17]1[CH2:16][C:15]2[C:10](=[CH:11][CH:12]=[CH:13][CH:14]=2)[CH2:9][N:8]1[C:6]([O:5][C:1]([CH3:4])([CH3:3])[CH3:2])=[O:7]
To a solution of the compound of Step A (1) ((R)-2-(tert-butoxycarbonyl)-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid, 6.3 g, 23 mmol) in THF (200 mL) was added triethylamine (36.5 mmol) followed by ethyl chloroformate (27.3 mmol). The mixture was stirred at rt for 2 h. NaBH4 (91.0 mmol) was then added and the mixture was stirred for 10 min. To the resulting mixture was added MeOH (40 ml) very slowly. When the addition was complete, the mixture was stirred for 3 h. The reaction was then concentrated in vacuo and the residue was partitioned between 1N NaOH and ethyl acetate (600 mL). The organic phase was washed with H2O, dried (Na2SO4), and concentrated in vacuo to give 5.5 g (91%) of the title compound: 1H NMR (CDCl3, 500 MHz) δ 1.49 (9H, s), 3.02 (1H, dd, J=5, 15 Hz), 3.50 (2H, brd s), 3.61 (1H, d, J=10 Hz), 4.30 (1H, d, J=15 Hz), 4.44-4.52 (1H, m), 4.67-4.76 (1H, m), 7.09-7.18 (4H, m). MS (ESI) (M+H)+ 264.19.
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