[CH:1]([C@@H:3]([NH:8][C:9](=[O:15])[O:10][C:11]([CH3:14])([CH3:13])[CH3:12])[CH2:4][CH2:5][CH2:6][CH3:7])=[O:2].O.CC(C)(O)[C:19]#[N:20].[C-]#N.[K+]>C1(C)C=CC=CC=1.[I-].C([N+](CCCC)(CCCC)CCCC)CCC>[C:19]([CH:1]([OH:2])[C@@H:3]([NH:8][C:9](=[O:15])[O:10][C:11]([CH3:14])([CH3:13])[CH3:12])[CH2:4][CH2:5][CH2:6][CH3:7])#[N:20]
To a stirred solution of tert-butyl (1S)-1-formylpentylcarbamate in toluene was added water (50 mL), acetone cyanohydrin (16.4 mL, 180.0 mmol), potassium cyanide (250 mg) and tetrabutylammonium iodide (300 mg). The mixture was stirred at ambient temperature for 20 h, and then the layers were separated. The organic layer was washed with water (5×60 mL), dried with magnesium sulfate and concentrated in vacuo to afford the title compound (26.7 g, 92%) as a thick oil. The 1H NMR spectrum showed an approximately equal mixture of diastereomers. 1H NMR (400 MHz, DMSO-d6): δ 6.91,6.83 (2d, J=8 Hz, J=9 Hz, 1H), 6.54, 6.47 (2d, J=7 Hz, J=6 Hz, 1H), 4.44, 4.17 (2t, J=5 Hz, J=8 Hz, 1H), 3.60-3.50 (m, 1H), 1.65-1.10 (m, 6H), 1.34 (s, 9H), 0.80 (t, J=6 Hz, 3H).
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