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2H), 5.39-5.30 (m, 1H), 5.13 (s, 2H), 3.96 (br d, 2H), 3.67 (bs, 3H), 1.68 (dd, J = 7.0, 3.1 Hz,<br />

3H), 1.69-1.67 (m, 3H), 1.52 (s, 3H); 13 C NMR (CDCl3, 75 MHz): δ 205.0, 173.3, 156.0, 136.8,<br />

128.7, 128.5, 128.2, 127.4, 125.2, 93.9, 90.9, 67.6, 64.5, 52.6, 17.9, 14.0; IR (thin film): ν 2949,<br />

1965, 1746, 1698, 1450 cm -1 ; MS (GC/MS) m/z 284 [M-59] + .<br />

CbzN<br />

MeO 2C<br />

75d<br />

2-(Benzyloxycarbonylbut-2-enylamino)-2,6-dimethylhepta-3,4-dienoic acid methyl ester<br />

(75d). Prepared by following the general procedure F, using: 65e (60 mg, 0.19 mmol), NaH<br />

(60% dispersion in mineral oil, 15 mg, 0.38 mmol), crotyl bromide (39 µL, 0.38 mmol).<br />

Purification by flash chromatography (hexanes-EtOAc, 9 : 1, v/v) afforded 75d (43 mg, 61%).<br />

1 H NMR (300 MHz, CDCl3, 323K): δ 7.34-7.27 (m, 5H), 5.69-5.50 (m, 3H), 5.40 (t, J = 6.1 Hz,<br />

1H), 5.13 (s, 2H), 3.98 (d, J = 4.1 Hz, 2H), 3.59 (s, 3H), 2.41-2.29 (m, 1H), 1.1.68 (d, J = 6.2 Hz,<br />

3H), 1.54 (s, 3H), 1.04 (d, J = 6.7 Hz, 6H); Two additional signals were observed in the 1 H NMR<br />

spectrum at 4.10 (d, J = 2.8 Hz), 1.61 (d, J = 4.3 Hz) and are attributed to carbamate rotational<br />

isomerism. 13 C NMR (CDCl3, 75 MHz, 323 K): δ 202.4, 172.8, 155.8, 136.6, 128.3, 128.0,<br />

127.9, 127.0, 103.0, 95.3, 67.3, 64.5, 52.2, 28.1, 22.5, 22.4, 17.5, 12.8; IR (thin film): ν 2959,<br />

1962, 1747, 1701, 1252 cm -1 ; MS m/z (%) 371 (24), 312 (25), 258 (31), 91 (100); EI-HRMS<br />

calcd for C22H29NO4 [M] + , m/z 371.2097, found 371.2104.<br />

184<br />

•<br />

H

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