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mL) and treated with 1M HCl (50 mL). The aqueous layer was extracted with Et2O (2 x 50 mL),
and the organic layers were combined, washed with 1M HCl (50 mL), dried over MgSO4, and
concentrated under vacuum to afford a yellow oil.
Step 2. Methyl ester formation: The yellow oil was dissolved in DMF (5 mL). Pulverized
KHCO3 (515 mg, 5.09 mmol) was added at rt, followed by addition of MeI (256 µL, 4.08 mmol)
via a syringe. The reaction mixture was stirred for 2 h, and then diluted with water (100 mL).
The cloudy mixture was extracted with EtOAc (3 x 75 mL), the organic layers were combined,
washed with brine, dried over MgSO4 and concentrated under vacuum. Purification of the crude
residue by flash chromatography (gradient elution; hexanes-EtOAc, 10 : 0 to 4 : 1, v/v) afforded
65b (555 mg, 73%).
65b : 1 H NMR (300 MHz, CDCl3): δ 7.42-7.28 (m, 5H), 5.78 (bs, 1H), 5.49 (dt, J = 7.0, 3.5 Hz,
1H), 5.13 (d, J = 12.4 Hz, 1H), 5.07 (d, J = 12.3 Hz, 1H), 3.70 (s, 3H), 2.37 (sex, J = 6.3 Hz,
1H). 1.92-1.86 (m, 2H), 1.70 (s, 3H), 1.36-1.27 (m, 4H), 1.05 (s, 3H), 1.03 (s, 3H), 0.88 (t, J =
7.2 Hz, 1H); 13 C NMR (75 MHz, CDCl3): δ 198.7, 173.5, 154.8, 137.0, 128.7, 128.2, 108.0,
105.8, 77.5, 66.7, 60.9, 52.9, 30.4, 28.9, 27.0, 22.7, 22.6, 14.2; IR (thin film): ν 3416, 2958,
1728, 1493, 1273 cm -1 ; MS m/z (%) 373 (11), 314 (9), 183 (21), 91 (100); EI-HRMS calcd for
C22H31NO4 m/z [M] + 373.2253; found 373.2268.
MeO 2C
•
H
C6H13 Bn
NHBoc
65a
2-Benzyl-2-tert-butoxycarbonylamino-3-methylundeca-3,4-dienoic acid methyl ester (65a).
Prepared by following general procedure D, using: LDA (1.58 mmol), 64a (265 mg, 0.661
mmol), ZnCl2 (158 µL of a 0.5 M solution in THF, 0.793 mmol), KHCO3 (62 mg, 0.62 mmol),
158