V. Bernat et al. / Tetrahedron 65 (2009) 7372–7379
7377
5.7.2. Diastereoisomer 11b
49.3 (CH, CCHCHCHCH2), 51.1, 51.7 (2C, 2CH3CCH3), 51.8, 52.6 (2C,
2CH3CCH3), 113.4–113.5 (2C, 2C(OH)]C), 131.3 (CH, CH]CH),
138.6 (CH, CH]CH), 189.7, 189.8 (2C, 2C(OH)]C), 193.3, 193.5
(2C, 2C(OH)]C–C]O), 212.3, 212.5 (2C, 2C]O) ppm. MS (DCI/
NH3, CH2Cl2, positive mode, m/z): 469 [MH]þ, 486 [MNH4]þ.
HRMS (DCI/CH4, CH2Cl2, positive mode, m/z): calculated for
C28H37O6 469.2590, found 469.2596.
Rf (pet. ether/AcOEt 8:2) 0.41. 1H NMR (300 MHz, CDCl3)
d¼0.99,
1.32, 1.35, 1.39 (4s, 3H, 4CH3), 1.44, 2.30 (m, 2H, two parts of ABX
system, CCH2CH), 2.03, 2.30 (m, 2H, two parts of ABX system,
CHCH2CH), 2.78 (m, 1H, CH2CHCH2), 3.06 (m, 1H, CCHCH]CH), 6.17
(dd, 1H, CCHCH]CH, 3JHH¼3.0, ¼5.6 Hz), 6.50 (dd, 1H, CCHCH]CH,
3JHH¼3.2, ¼5.6 Hz), 6.97 (s, 1H, C]CH) ppm. 13C NMR (75.46 MHz,
CDCl3)
d
¼15.2, 20.8, 24.5, 24.6 (4CH3), 39.7 (CH2, CCH2CH), 42.29
(CH, CCH2CH), 47.7 (CH2,CCHCH2), 51.0 (CH, CCHCH]CH), 51.7, 54.8
(2C, 2CH3CCH3), 89.8 (C, C]CH–C–O), 97.3 (C, CO(OH)), 131.8 (CH,
CCHCH]CH), 132.4 (C, C]CH), 142.9 (CH, CCHCH]CH), 143.4 (CH,
C]CH),198.2 (C, C]C–C]O); 210.8 (C, C]O) ppm. MS (ESI, CH2Cl2/
MeOH, positive mode, m/z): 341 [MNa]þ. HRMS (ESI, MeOH, posi-
tive mode, m/z): calculated for C18H22O5Na 341.1365, found
341.1390.
5.10. Synthesis of endoperoxides 15a (anti) and 15b (syn)
Theprocedurewasthesameasthatpreviouslydescribedbutusing
2,2-dimethyl-1,3-dioxolane-4-carboxaldehyde(309 mg, 2.374 mmol)
and syncarpic acid (433 mg, 2.374 mmol). Enone was kept under air
for 6 days. After purification bysilicagel column chromatography (pet.
ether/AcOEt 8:2), a major fraction (252 mg) was obtained containing
both endoperoxide 15a (71 mg by estimation on 1H NMR spectrum,
0.216 mmol, 9%) and ether 16 (181 mg, 0.616 mmol) besides endo-
peroxide 15b (43 mg, 0.132 mmol, 6%) obtained as a white solid, ep-
oxide 17 (22 mg, 0.071 mmol, 3%), and Michael adduct 18 (33 mg,
0.069 mmol, 3%).
5.8. 2,2,4,4-Tetramethyl-6-(3-(bicyclo[2.2.1]hept-5-
en-2-yl))oxiranyl-cyclohexane-1,3,5-trione (12)
5.8.1. Diastereoisomer 12a
Rf (pet. ether/AcOEt 9:1) 0.57. 1H NMR (300 MHz, CDCl3)
d
¼0.67 and 1.66 (m, 2H, two parts of ABX system,
5.10.1. (3R
*
,8aS )-3-(2,2-Dimethyl-1,3-dioxolan-4-yl)-8,8a-
*
(O)CHCHCH2CH), 0.99 and 1.23 (m, 2H, two parts of ABX system,
CHCH2CH), 1.28, 1.34, 1.35, 1.44 (4s, 3H, 4CH3), 1.96 (m, 1H,
(O)CHCH), 2.86 (m, 1H, (O)CHCHCH2CH), 3.14 (m, 1H, (O)CHCHCH),
3.20 (d, 1H, CH(O)), 6.18 (m, 2H, CH]CH) ppm. 13C NMR
dihydro-8a-hydroxy-6,6,8,8-tetramethylbenzo[c][1,2]dioxine-
5,7(3H,6H)-dione (15a)
Rf (EP/AcOEt 7:3) 0.38. 1H NMR (300 MHz, CDCl3)
d
¼1.08, 1.33,
1.35, 1.37 (4s, 3H, 4CH3), 1.48, 1.58 (2s, 3H, 2CH3, ketal), 4.03 and
(75.46 MHz, CDCl3)
d
¼19.3, 21.3, 23.9, 24.0 (4CH3), 29.2 (CH2,
2
4.14 (d, 2H, two parts of AB system, CH2, JHH¼10.2 Hz), 6.91 (s,
(O)CHCHCH2CH), 35.8 (CH, (O)CHCH), 42.5 (CH, (O)CHCHCH2CH),
45.8 (CH, (O)CHCHCH), 49.4 (CH2, CHCH2CH), 59.7–60.2 (2C,
2CH3CCH3), 63.8 (C, O]C–C(O)–C]O), 73.1 (CH, C(O)CH), 132.6–
138.0 (2CH, C]C), 201.9–202.1 (2C, 2(C]O)C(O)), 207.3 (C,
C]O) ppm. MS (DCI/NH3, CH2Cl2, positive mode, m/z): 320
[MNH4]þ, 337 [MN2H7]þ, 622 [2MNH4]þ. HRMS (DCI/CH4, CH2Cl2,
positive mode, m/z): calculated for C18H23O4 303.1596, found
303.1594.
1H, C]CH) ppm. 13C NMR (75.46 MHz, CDCl3)
d
¼14.8, 21.0, 24.0,
26.4 (4CH3), 26.1, 26.4 (2CH3, ketal), 52.0, 55.0 (2C, 2CH3CCH3),
71.5 (CH2, CCH2O), 97.0 (C, CO(OH)), 103.4 (C, C(O)2CH2), 114.0 (C,
C(O)2(CH3)2), 132.1 (CH, C]CH), 135.1 (C, C]CH), 198.0 (C, C]C–
C]O), 210.1 (C, C]O) ppm. MS: (DCI/NH3, CH2Cl2, positive mode,
m/z): 344 [MNH4]þ. HRMS (ESI, MeOH, positive mode, m/z):
calculated for C16H22O7Na 349.1263, found 349.1169.
5.10.2. (3R
*
,8aR )-3-(2,2-Dimethyl-1,3-dioxolan-4-yl)-8,8a-
*
5.8.2. Diastereoisomer 12b
dihydro-8a-hydroxy-6,6,8,8-tetramethylbenzo[c][1,2]dioxine-
Rf (EP/AcOEt 9:1) 0.57. 1H NMR (300 MHz, CDCl3)
d
¼0.94 and
5,7(3H,6H)-dione (15b)
1.88 (m, 2H, two parts of ABX system, (O)CHCHCH2CH), 1.01 and
1.19 (m, 2H, two parts of ABX system, CHCH2CH), 1.36, 1.40, 1.42,
1.45 (4s, 3H, 4CH3), 1.94 (m, 1H, (O)CHCH), 2.58 (m, 1H,
(O)CHCHCH), 2.90 (m, 1H, (O)CHCHCH2CH), 3.23 (d, 1H, CH(O)),
5.90 (m, 1H, CH]CH), 6.28 (m, 1H, CH]CH) ppm. 13C NMR
Rf (EP/AcOEt 7:3) 0.56. 1H NMR (300 MHz, CDCl3)
d
¼0.99, 1.29,
1.35, 1.37 (4s, 3H, 4CH3), 1.46, 1.54 (2s, 3H, 2CH3 ketal), 3.96 and
2
4.48 (2d, 2H, two parts of AB system, CH2, JHH¼9.7 Hz), 6.96 (s,
1H, C]CH) ppm. 13C NMR (75.46 MHz, CDCl3)
d
¼14.6, 20.8, 24.0,
26.4 (4CH3), 25.4, 27.3 (2CH3, ketal), 51.6, 54.8 (2C, 2CH3CCH3),
71.3 (CH2, CCH2O), 97.7 (C, CO(OH)), 105.3 (C, C(O)2CH2), 114.9 (C,
C(O)2(CH3)2), 133.7 (CH, C]CH), 137.5 (C, C]CH), 197.5 (C, C]C–
C]O), 209.8 (C, C]O) ppm. MS (ESI, MeOH, positive mode, m/z):
349 [MNa]þ, 675 [2MNa]þ. HRMS (ESI, MeOH, positive mode, m/
z): calculated for C16H22O7Na 349.1263, found 349.1169.
(75.46 MHz, CDCl3)
d
¼20.5, 21.7, 23.0, 23.5 (4CH3), 31.0 (CH2,
(O)CHCHCH2CH), 36.2 (CH, (O)CHCH), 42.3 (CH, (O)CHCHCH2CH),
44.6 (CH, (O)CHCHCH), 49.9 (CH2, CHCH2CH), 59.7, 60.2 (2C,
2CH3CCH3), 63.8 (C, O]C–C(O)–C]O), 73.5 (CH, C(O)CH), 131.2
(CH, C]C), 139.2 (CH, C]C), 201.9–202.1 (2C, 2(C]O)C(O)), 207.3
(C, C]O) ppm. MS (DCI/NH3, CH2Cl2, positive mode, m/z): 320
[MNH4]þ, 337 [MN2H7]þ, 622 [2MNH4]þ. HRMS (DCI/CH4, CH2Cl2,
positive mode, m/z): calculated for C18H23O4 303.1596, found
303.1594.
5.11. 2,3-Dihydro-2-(2,2-dimethyl-1,3-dioxolan-4-yl)-5,5,7,7-
tetramethylbenzofuran-4,6(5H,7H)-dione (16)
5.9. 4-((Bicyclo[2.2.1]hept-5-en-2-yl)(2-hydroxy-3,3,5,5-
tetramethyl-4,6-dioxocyclohex-1-enyl)methyl)-5-hydroxy-
2,2,6,6-tetramethylcyclohex-4-ene-1,3-dione (13)
Rf (EP/AcOEt 7:3) 0.38. 1H NMR (300 MHz, CDCl3)
d
¼1.31, 1.33,
1.38, 1.41, (4s, 3H, 4CH3), 1.43, 1.54 (2s, 3H, 2CH3 ketal), 3.02 and
3.06 (2d, 2H, two parts of AB system, C]C–CH2, 2JHH¼16.3 Hz), 4.04
3
and 4.36 (2d, 2H, two parts of AB system, CH2, JHH¼9.6 Hz) ppm.
Rf (pet. ether/AcOEt 8:2) 0.50. 1H NMR (300 MHz, CDCl3)
13C NMR (75.46 MHz, CDCl3)
(2CH3 ketal), 33.7 (CH2, C]C–CH2), 45.1, 55.35 (2C, 2CH3CCH3), 73.6
(CH2, CCH2O), 108.6 (C, C]C–CH2), 113.2 (C, C(O)2(CH3)2), 116.4 (C,
C(O)2(CH2)2), 175.2 (C, C]C–O), 194.2 (C, C]C–C]O), 213.2 (C,
d
¼24.0, 24.2, 24.7, (4CH3), 25.8, 27.1
d
¼0.30 and 1.71 (m, 2H, two parts of ABX system, CHCH2CH),
1.30 and 1.44 (m, 2H, two parts of ABX system, CHCH2CH), 1.33,
1.35, 1.36, 1.39, 1.40, 1.42, 1.47, 1.53 (8s, 24H, 8CH3), 2.57 (m, 1H,
CHCHCHCH2), 2.76 (m, 1H, CH2CHCH2), 3.31 (m, 2H, 2CHCH), 5.68
C]O) ppm. IR (diamond compression system) n: 2983–2876 (CH2
3
(dd, 1H, CH]CH, JHH¼2.7, ¼5.8 Hz), 6.21 (dd, 1H, CH]CH,
and CH3), 1717 (C]O), 1626 (C]C), 1057 (C–O) cmꢀ1. MS (DCI/NH3,
CH2Cl2, positive mode, m/z): [MH]þ 295, [MNH4]þ 312. HRMS (DCI/
CH4, CH2Cl2, positive mode, m/z): calculated for C16H23O5 295.1545,
found 295.1568.
3JHH¼3.1, ¼5.8 Hz), 13.36 (1H, OH) ppm. 13C NMR (75.46 MHz,
CDCl3)
d
¼24.6, 25.1, 25.1, 25.7, 23.3, 24.5, 25.6, 36.6 (8CH3), 31.7
(CH2, CCHCHCH2), 42.6 (CH, CCHCHCH2C), 45.1 (CH, CCHCHCH),