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CbzN
MeO 2C
Me
73h
2-[Benzyloxycarbonyl(3-trimethylsilylprop-2-ynyl)amino]-2-methylhexa-3,4-dienoic acid,
methyl ester (73h). To a solution of 65d (134 mg, 0.464 mmol), in THF (4 mL) was added KH
(68 mg of 35% wt. dispersion in mineral oil, 0.51 mmol) at rt, followed by addition of (3-
bromoprop-1-ynyl)-trimethylsilane (131 µL, 0.93 mmol). The reaction mixture was stirred at rt
for 10 h. The reaction mixture was then poured into a beaker containing EtOAc (50 mL) and
water (50 mL). The aqueous layer was extracted with EtOAc and the organic layers were
combined, washed with brine, dried over MgSO4, and concentrated under vacuum. Purification
by flash chromatography (hexanes-EtOAc, 9 : 1, v/v) afforded 73h (128 mg, 86%).
1 H NMR (300 MHz, CDCl3, 310 K): δ 7.37-7.27 (m, 5H), 5.48 – 5.34 (m, 2H), 5.20 (d, J = 12.5
Hz, 1H), 5.15 (d, J = 12.7 Hz, 1H), 4.38 (d, J = 18.3 Hz, 1H), 4.18 (d, J = 18.4 Hz, 1H), 3.59 (bs,
3H), 1.73 (dd, J = 6.7, 2.9 Hz, 3H), 1.66 (s, 3H), 0.16 (s, 9H); 13 C NMR (75 MHz, CDCl3, 310
K): δ 205.3, 172.5, 155.1, 136.3, 128.3, 127.9, 102.7, 92.9, 90.5, 88.0, 67.5, 64.5, 52.3, 34.8,
13.8, -0.3; IR (thin film): ν 2954, 2177, 1967, 1748, 1707, 1251 cm -1 ; MS m/z (%) 399 (5), 384
(9), 340 (25), 91 (100); EI-HRMS calcd for C22H29NO4Si m/z [M] + 399.1866; found 339.1875.
CbzN
MeO 2C
Me
73i
2-[Benzyloxycarbonyl(3-phenylprop-2-ynyl)amino]-2-methylhexa-3,4-dienoic acid methyl
ester (73i). Prepared by following general procedure F, using: 65d (210 mg, 0.72 mmol), NaH
(58 mg of 60% dispersion in mineral oil, 1.4 mmol), (3-bromoprop-1-ynyl)-benzene (281 mg,
1.44 mmol). Purification by flash chromatography (hexanes-EtOAc, 9 : 1, v/v) afforded 73i (199
173
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TMS
Ph
H
H