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13.5 Hz, 1H), 3.03 (d, J = 13.5 Hz, 1H), 1.99 (d, J = 7.5 Hz, 3H), 1.90 (sep, J = 6.7 Hz, 1H), 0.96
(d, J = 6.6 Hz, 3H), 0.95 (d, J = 6.6 Hz, 3H); 13 C NMR (75 MHz, CDCl3): δ 160.5, 149.1, 146.9,
144.0, 138.5, 132.7, 132.2, 130.8, 128.2, 127.8, 126.8, 119.3, 119.2, 66.0, 55.3, 47.4, 29.2, 20.4,
16.2; IR (thin film): ν 2956, 1836, 1743, 1269 cm -1 ; MS m/z (%) 364 (6), 320 (19), 229 (33), 173
(100), 91 (63); EI-HRMS calcd for C22H24N2O3 m/z [M] + 364.1787; found 364.1786.
General procedure K for preparation of cycloadducts 156a and 156b.
MeO 2C
O
O
O
N
H
N
Bn
O
N
Ph
(10c-Benzyl-5-ethylidene-3,4,8,10-tetraoxo-9-phenyl-4,5,7,7a,8,9,10,10a,10b,10c-decahydro-
2-oxa-3a,9-diazadicyclopenta[a,h]naphthalen-1-ylideneamino)-acetic acid methyl ester
(156a). A solution of triene 155a (0.063 g, 0.17 mmol) and N-phenylmaleimide (0.037 g, 0.22
mmol) in toluene (4 mL) was heated to 90 ºC until the starting material was completely
consumed as evidenced by TLC analysis. During this time, 156a began precipitating as a white
solid. The mixture was cooled to 0 ºC in a test tube and centrifuged for 15 min. The toluene was
decanted away and the solid was rinsed with hexanes and dried under vacuum to afford 156a
(0.067 g, 73%).
1 H NMR (300 MHz, CDCl3): δ 7.41-7.29 (m, 6H), 7.09-7.00 (m, 4H), 6.65 (q, J = 7.3 Hz, 1H),
6.25-6.19 (m, 1H), 4.36 (d, J = 18.0 Hz, 1H), 4.34 (dd, J = 9.0, 5.2 Hz, 1H), 4.22 (d, J = 18.1 Hz,
1H), 3.78 (s, 3H), 3.46 (t, J = 7.9 Hz, 1H), 3.37 (d, J = 13.5 Hz, 1H), 3.27 (d, J = 13.5 Hz, 1H),
3.10 (bs, 1H), 3.09-3.02 (m, 1H), 2.31 (d, J = 7.4 Hz, 3H), 2.35-2.25 (m, 1H); 13 C NMR (75
MHz, CDCl3): δ 177.8, 176.1, 170.1, 159.5, 153.6, 146.2, 141.3, 135.6, 132.2, 131.1, 130.0,
212
156a
O