5756
M. A. Brimble et al. / Tetrahedron 60 (2004) 5751–5758
t
CDCl3) 1.41 (9H, s, Bu), 3.04 (2H, apparent d, J¼5.4 Hz,
H-3), 3.99 (3H, s, OMe), 5.28 (1H, t, J¼5.4 Hz, H-3a), 5.93
(1H, d, J¼5.4 Hz, H-10b), 7.59 (2H, m, H-6 and H-7), 7.89
(1H, m, H-5), 8.59 (1H, m, H-8), 11.09 (1H, s, OH); dC
(100 MHz, CDCl3) 27.8 (CH3, CMe3), 38.1 (CH2, C-3), 52.0
(CH3, OMe), 65.7 (CH, C-10b), 79.4 (CH, C-3a), 83.5 (C,
CMe3), 105.1 (C, C-10), 114.5 (C, C-10a), 121.7 (CH, C-5),
123.5 (C, C-4b), 124.3 (C, C-8a), 126.2 (CH, C-7), 129.0
(CH, C-6), 150.2 (C, C-4a), 150.3 (C, NCO2), 154.0 (C,
C-9), 179.5 (C, C-2), 171.2 (C, CO2Me); m/z 399 (Mþ, 3%),
326 (M2OtBu, 1), 299 (62), 267 (100).
(CH, C-60), 126.9 (CH, C-70), 127.8 (C, C-4a0), 143.3 (C,
C-10), 145.9 (C, C-40), 157.4 (C, NCO), 205.4 (C, COMe).
Three quaternary carbons (C-20, C-30 and C-8a0) were not
observed; m/z 497 (Mþ, 12%), 366 (M2tBuMe2SiO, 33), 73
(OtBu, 100), 57 (C4H6, 46).
3.1.11. tert-Butyl 2-(3-acetyl-5-methoxy-1,4-dihydroxy-
2-naphthyl)-5-(tert-butyldimethylsilyloxy)-1H-pyrrole-
1-carboxylate 13. To an ice-cooled solution of 2-acetyl-8-
methoxy-1,4-naphthoquinone 8 (30 mg, 0.156 mmol) in
acetonitrile (2 mL) was added a solution of TBSOP 3
(78 mg, 0.313 mmol) in acetonitrile (1.5 mL) dropwise
under nitrogen. After 1 h, the solution was warmed to room
temperature then stirred overnight. The solvent was
removed under reduced pressure to afford a brown residue
which was purified by flash chromatography using hexane–
ethyl acetate (4:1) as eluent to afford the title compound 13
(26 mg, 38%) as a yellow oil, (Found: Mþ, 527.2334,
C28H37NO7Si requires 527.2339); dH (300 MHz, CDCl3)
0.27 (6H, d, J¼1.6 Hz, Met2BuSi), 1.01 (9H, s, Met2BuSi),
3.1.9. tert-Butyl 2-(2-acetyl-1,4-dihydroxy-3-phenyl)-5-
(tert-butyldimethylsilyloxy)-1H-pyrrole-1-carboxylate
11. To an ice-cooled solution of 2-acetyl-1,4-benzoquinone
6 (200 mg, 1.33 mmol) dissolved in acetonitrile (6 mL) was
added a solution of TBSOP 3 (790 mg, 2.66 mmol) in
acetonitrile (14 mL) dropwise with stirring under nitrogen.
After 20 h the solvent was removed under reduced pressure
to afford a brown residue that was purified by flash
chromatography using hexane–ethyl acetate as eluent
(gradient elution 9:1 to 1:9) to afford the title compound
11 (334 mg, 56%) as yellow crystals, mp 94–97 8C, (Found:
Mþ, 447.2076, C22H33NO6Si requires 447.2077); nmax
(film)/cm21 3338v (OH), 2929m, 1763m (NCvO),
1621m (CvO), 1290m (Si–C); dH (400 MHz, CDCl3)
0.25 (6H, s, SiMet2Bu), 1.01 (9H, s, SiMet2Bu), 1.20 (9H, s,
tBu), 2.03 (3H, s, COMe), 4.30 (1H, s, OH), 5.46 (1H, d,
J¼3.6 Hz, H-4), 6.00 (1H, d, J¼3.6 Hz, H-3), 6.92 (1H, d,
J¼8.9 Hz, H-60), 7.08 (1H, d, J¼8.9 Hz, H-50), 11.69 (1H, s,
OH); dC (100 MHz, CDCl3) 25.1 (CH3, SiMeMetBu), 24.9
(CH3, SiMeMe tBu), 18.1 (C, CMe3), 25.5 (CH3, SiMet2Bu),
28.0 (CH3, COMe), 29.3 (CH3, CMe3), 92.6 (CH, C-4),
112.9 (CH, C-3), 116.8 (C, C-2), 119.00(CH, C-60), 120.4 (C,
C-5), 121.1 (0C, C-30), 121.3 0(C, C-2 ), 122.7 (CH, C-50),
145.7 (C, C-4 ), 147.4 (C, C-1 ), 155.5 (C, NCO2), 205.9 (C,
COMe); m/z 447 (Mþ, 11%), 391 (M2C4H8, 5), 347
(M2C4H8CO2, 100), 316 (M2tBuMe2SiO, 20), 73 (OtBu,
90), 57 (C4H6, 62).
t
1.10 (9H, s, Bu), 2.22 (3H, s, COMe), 4.06 (3H, s, OMe),
5.41 (1H, d, J¼3.5 Hz, H-4), 5.58 (1H, s, OH), 6.04 (1H, d,
J¼3.5 Hz, H-3), 6.91 (1H, d, J¼8.0 Hz, H-60), 7.45 (1H, t,
J¼8.0 Hz, H-70), 7.82 (1H, d, J¼8.0 Hz, H-80), 11.32 (1H, s,
OH); m/z 527 (Mþ, 10%), 366 (M2tBuMe2SiO, 36), 73
(OtBu, 100), 57 (C4H6, 41).
3.1.12. tert-Butyl (3aS p,10bS p)-10-acetyl-9-hydroxy-2-
oxo-2,3,3a,10b-tetrahydro-1H-[1]naphthofuro[3,2-
b]pyrrole-1-carboxylate 14. To a solution of 2-acetyl-1,4-
naphthoquinone 7 (30 mg, 0.15 mmol) in anhydrous
dichloromethane (4 mL) was added Eu(fod)3 (158 mg,
0.15 mmol) and the mixture was stirred under nitrogen at
room temperature for 50 min. The mixture was then cooled
to 278 8C and a solution of TBSOP 3 (43 mg, 0.15 mmol)
in anhydrous dichloromethane (2 mL) was added dropwise.
The mixture was then warmed to room temperature and
stirred for 16 h. The reaction mixture was quenched with
H2O (5 mL) and extracted with dichloromethane (3£5 mL).
The combined organic extracts were washed with H2O
(10 mL) and dried over MgSO4. The solvent was removed
under reduced pressure to give a red–brown oil that was
purified by flash chromatography with hexane–ethyl acetate
(9:1 then 8:2 then 1:1) as eluent to give the title compound
14 (19 mg, 33%) as a yellow oil, (Found: Mþ, 383.1371,
C21H21NO6 requires 383.1369); nmax (film)/cm21 3445br
(OH), 1773m (CvO), 1714m (CvO); dH (300 MHz,
3.1.10. tert-Butyl 2-(3-acetyl-1,4-dihydroxy-2-naphthyl)-
5-(tert-butyldimethylsilyloxy)-1H-pyrrole-1-carboxylate
12. To an ice-cooled solution of 2-acetyl-1,4-naphtho-
quinone 7 (16 mg, 0.08 mmol) in acetonitrile (1.5 mL) was
added a solution of TBSOP 3 (47 mg, 0.16 mmol) in
acetonitrile (1.5 mL) dropwise under nitrogen atmosphere.
After 1 h, the mixture was warmed to room temperature and
then left stirred overnight. The solvent was evaporated
under reduced pressure to afford a brown residue that was
purified by flash chromatography using hexane–ethyl
acetate (95:5) as eluent to give the title compound 12
(25 mg, 64%) as a yellow oil, (Found: Mþ, 497.2231,
C27H35NO6Si requires 497.2234); nmax (film)/cm21 3485v
(OH), 2930m, 1754m (CvO), 1675m (CvO); dH
(200 MHz, CDCl3) 0.28 (6H, s, SiMet2Bu), 1.02 (9H, s,
SiMet2Bu), 1.04 (9H, s, tBu), 2.08 (3H, s, Me), 5.50 (1H, d,
J¼3.5 Hz, H-4), 6.14 (1H, d, J¼3.5 Hz, H-3), 7.54–7.77
(2H, m, H-60, H-70), 8.18 (1H, d, J¼8.0 Hz, H-50), 8.48 (1H,
d, J¼7.7 Hz, H-80); dC (50 MHz, CDCl3) 24.9 (CH3,
SiMe2), 24.8 (CH3, SiMe2), 18.3 (C, SiCMe3), 25.6 (CH3,
SiCMe3), 27.1 (CH3, Me), 28.9 (CH3, CMe3), 84.0 (C,
CMe3), 92.6 (CH, C-4), 113.0 (CH, C-3), 114.5 (C, C-5),
117.0 (C, C-2), 119.4 (CH, C-80), 122.6 (CH, C-50), 124.5
t
CDCl3) 1.38 (9H, s, Bu), 2.83 (3H, s, COMe), 3.02 (1H,
dd, J¼18.0, 5.1 Hz, H-3A), 3.13 (1H, d, J¼18 Hz, H-3B),
5.34 (1H, t, J¼5.1 Hz, H-3a), 5.84 (1H, d, J¼5.1 Hz,
H-10b), 7.57 (1H, ddd, J¼7.5, 7.5, 1.5 Hz, H-7), 7.63 (1H,
ddd, J¼7.5, 7.5, 1.5 Hz, H-6), 7.89 (1H, ddd, J¼7.5, 1.5,
0.6 Hz, H-5), 8.40 (1H, ddd, J¼7.5, 1.5, 0.6 Hz, H-8), 12.99
(1H, s, OH); dC (75 MHz, CDCl3) 27.7 (CH3, CMe3) 31.5
(CH3, COMe), 38.3 (CH2, C-3), 66.2 (CH, C-10b), 78.3
(CH, C-3a), 83.0 (C, CMe3), 84.0 (C, C-10), 113.2 (C,
C-10a), 121.9 (CH, C-5), 123.9 (C, C-8a), 124.9 (CH, C-8),
127.0 (C, C-4b), 127.5 (CH, C-7), 129.6 (CH, C-6), 149.5
(C, C-4a), 150.6 (C, NCO2), 155.1 (C, C-9), 169.1 (C, C-2),
204.1 (C, COMe); m/z (EI) 383 (Mþ, 3%), 310 (M2OtBu,
3), 283 (M2tBu–COMe, 66), 239 (M2COt2Bu–COMe,
70), 73 (OtBu, 100). Silyloxypyrrole 12 (32 mg, 43%) was
also recovered from the reaction.