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1H), 5.49 (dd, J = 17.3, 1.8 Hz, 1H), 5.43 (q, J = 7.1 Hz, 1H), 5.18 (dd, J = 10.7, 1.8 Hz, 1H),
4.46 (d, J = 9.0 Hz, 1H), 4.23-4.11 (m, 2H), 4.06 (d, J = 9.0 Hz, 1H), 4.02 (d, J = 13.3 Hz, 1H),
3.78 (d, J = 14.2 Hz, 1H), 3.35 (d, J = 14.1 Hz, 1H), 2.95 (d, J = 13.2 Hz, 1H), 1.86 (t, J = 2.3
Hz, 3H), 1.30 (d, J = 7.1 Hz, 1H).
176: Synthesized according to the following scheme:
•
O
BzHN
a •
b BzN
c
O
O
N O >95% >95%
• 89%
O
Ph
O
180 333 334
a) 2-butyne-1-ol (2 equiv.), Et 3N (cat.); b) NaH (2 equiv.), 1-bromo-2-butyne (2 equiv.), DMF; c) 5 mol% [Rh(CO) 2Cl] 2, toluene, rt.
2-Benzoylamino-2-methylhexa-3,4-dienoic acid but-2-ynyl ester (333). 2-Butyn-1-ol (0.170
mL, 2.23 mmol) was added to neat oxazolone 180 ll (0.253 g, 1.11 mmol) followed by addition of
Et3N (10 µL) and the reaction was stirred for 30 min. All volatiles were removed under vacuum,
and the remaining yellow residue was purified by flash chromatography (hexanes/EtOAc, 4 : 1,
v/v) to afford 333 (0.320 g, 96% as a mixture of inseparable diastereomers in 1.5 : 1 ratio).
1 H NMR (300 MHz, CDCl3): δ 7.78-7.75 (m, 2H), 7.50-7.38 (m, 3H), 6.93 (bs, 0.4H), 6.90 (bs,
0.6H), 5.56-5.38 (m, 2H), 4.80-4.64 (m, 2H), 1.83-1.81 (m, 3H), 1.79 (s, 1.2H), 1.77 (s, 1.8H),
1.73-1.69 (m, 3H); 13 C NMR (75 MHz, CDCl3): δ 203.0, 202.9, 171.9, 171.8, 166.3, 166.3,
134.3, 131.4, 128.4, 128.2, 126.9, 94.0, 91.6, 83.3, 83.2, 72.8, 72.8, 58.4, 54.0, 54.0, 23.0, 22.9,
13.9, 13.9, 3.5; IR (thin film): ν 3308, 2322, 2923, 2243, 2117, 1968, 1744, 1640 cm -1 ; MS m/z
(%) 297 (38), 282 (21), 244 (73), 200 (55), 105 (100); EI-HRMS calcd for C18H19NO3 m/z [M] +
297.1365; found 297.1364.
ll See page 224 for preparation of intermediate 180.
221
O
Bz
O
N
176