J. A. Valderrama et al. / Tetrahedron 58 ,2002) 881±886
885
2.1). IR n 3423 *O±H), 1650 *CvO). 1H NMR d 11.36 *s,
1H, 6-OH), 9.60 *s, 1H, CHO), 7.30 *s, 1H, H-10), 7.20 *d,
1H, J9.1 Hz, H-4), 6.94 *d, 1H, J9.1 Hz, H-5), 5.72 *s,
1H, 3-OH), 2.70 *ddd, J1.6, 6.5, 17.0 Hz, H-40eq), 2.42
*ddd, J7.2, 11.3, 17.0 Hz, H-40ax), 2.01 *br d, 1H,
J10.8 Hz, H-90eq), 1.90±1.31 *m, 8H), 1.25 *s, 3H, 90a-
Me), 0.95 *s, 3H, 60-Me), 0.92 *s, 3H, 60-Me0). 13C NMR d
196.7, 156.7, 146.9, 139.3, 138.9, 136.7, 126.1, 123.3,
119.4, 118.5, 117.2, 51.2, 41.9, 39.2, 34.1, 33.5 33.2, 25.0,
21.6, 21.6, 18.9, 18.8.
was removed under reduced pressure and the residue was
column chromatographed on silica gel *dichloromethane)
to give 2-methoxycarbonyl-3-*60,60,90a-trimethyl-40,50,
50aS,60,70,80,90,90aS-octahydronaphtho[1,2-c]furan-30-yl)-
1,4-benzoquinone *6c) *181 mg, 77% referred to 0.5 equiv.
of 3c) as red crystals mp 119±1208C *Found: C, 72.51; H,
6.91. C23H26O5 requires: C, 72.23; H, 6.85); IR n 1744
1
*CvO), 1672 *CvO). H NMR d 7.25 *s, 1H, H-10), 6.79
*s, 2H, H-5 and H-6), 3.88 *s, 3H, OMe), 2.86 *ddd, 1H,
0
J2.2, 6.9, 18.4Hz, H-4 eq), 2.75 *ddd, 1H, J6.8, 11.0,
18.2 Hz, H-40ax), 1.95 *br d, 1H, J12.1 Hz, H-90eq),
1.87±1.23 *m, 8H), 1.20 *s, 3H, 90a-Me), 0.94*s, 3H,
60-Me), 0.90 *s, 3H, 60-Me0). 13C NMR d 185.1, 183.7,
165.3, 141.7, 141.7, 139.6, 136.5, 136.0, 132.4, 131.1,
131.1, 52.5, 50.6, 41.7, 39.2, 34.0, 33.4, 33.0, 24.9, 24.0,
21.5, 18.9, 18.8.
3.1.2. Reaction of furan 2 with 2-formyl-1,4-benzoqui-
none /3a). A suspension of 2,5-dihydroxybenzaldehyde
*177 mg, 1.28 mmol), silver*I) oxide *350 mg, 1.52 mmol)
and sodium sulfate *500 mg) in benzene was stirred at 408C
for 2 h. The mixture was ®ltered and the ®ltrate was added
to a solution of furan 2 *280 mg, 1.28 mmol) in benzene
*25 mL) and the mixture was left at room temperature for
5 min. Evaporation of the solvent followed by column chro-
matography *dichloromethane) of the residue afforded 5a
*342 mg, 76%).
3.1.5. Reaction of furan 2 with in situ generated 2-nitro-
1,4-benzoquinone /3d). A suspension of 2-nitro-1,4-di-
hydroxybenzene *179 mg, 1.15 mmol), furan 2 *251 mg,
1.15 mmol), silver*I) oxide *300 mg, 1.3 mmol) and sodium
sulfate *500 mg) in dichloromethane *30 mL) was stirred at
rt for 15 min. The mixture was ®ltered through kieselguhr,
the ®ltrate was evaporated under reduced pressure and the
residue was chromatographed on silica gel *dichloro-
methane). Evaporation of the less polar fraction gave
2-nitro-3-*60,60,90a-trimethyl-40,50,50aS,60,70,80,90,90aS-
octahydronaphtho[1,2-c]furan-30-yl)-1,4-benzoquinone
*6d) *196 mg, 46%; respect to 0.5 equiv. of 2-nitro-1,4-
dihydroxybenzene) as violet crystals mp 162±1638C
*Found: C, 67.90; H, 6.24; N, 3.84. C21H23NO5 requires:
C, 68.28; H, 6.28; N, 3.79); IR n 2929 *C±H), 1680
3.1.3. Reaction of furan 2 with 2-acetyl-1,4-benzoqui-
none /5b). A solution of furan 2 *218 mg, 1.0 mmol), and
quinone 3b *150 mg, 1.0 mmol) in dichloromethane
*35 mL) was left at room temperature for 5 h. The solvent
was removed under reduced pressure and the residue was
column chromatographed on silica gel *dichloromethane).
The less polar fraction gave pure 3,6-dihydroxy-2-
*60,60,90a-trimethyl-40,50,50aS,60,70,80,90,90aS-octahydro-
naphtho[1,2-c]furan-30-yl)-acetophenone *5b) *61 mg,
17%) as yellow crystals mp 130.8±131.08C *Found: C,
75.36; H, 7.56. C23H28O4 requires: C, 74.97; H, 7.66);
1
*CvO), 1661 *CvO), 1543 *NO2). H NMR d 7.34*s,
31
[a]D 222.26 *c, 5.39). IR n 3415 *OH), 2935 *C±H),
1H, H-10), 6.88 *s, 2H, 0 H-5 and H-6), 2.93 *ddd, 1H,
J2.5, 7.1, 18.1 Hz, H-4 eq), 2.81 *ddd, 1H, J6.7, 11.3,
18.9 Hz, H-40ax), 1.96 *br d, 1H, J11.0 Hz, H-90eq),
1.89±1.23 *m, 8H), 1.20 *s, 3H, 90a-Me), 0.95 *s, 3H,
60-Me), 0.91 *s, 3H, 60-Me0). 13C NMR d 184.3, 176.9,
142.4, 142.3, 142.2, 137.0, 136.7, 135.4, 134.9, 124.9,
50.6, 41.7, 39.1, 34.1, 33.3, 33.0, 24.8, 24.4, 21.5, 18.8,
18.7.
1
1635 *CvO). H NMR d 11.46 *s, 1H, 6-OH), 7.31 *s,
1H, H-10), 7.13 *d, 1H, J9.0 Hz, H-4), 6.97 *d, 1H,
J9.1 Hz, H-5), 5.41 *s, 1H, 3-OH), 2.63 *dd, J6.0,
16.5 Hz, H-40eq), 2.36 *ddd, J7.0, 11.3, 17.5 Hz, H-40ax),
2.02 *br d, 1H, J10.9 Hz, H-90eq), 1.84*s, 3H, COMe),
0
1.81±1.27 *m, 8H), 1.24*s, 3H, 9 a-Me), 0.95 *s, 3H, 60-
Me), 0.92 *s, 3H, 60-Me0). 13C NMR d 205.5, 155.5, 147.0,
140.6, 140.0, 136.5, 123.5, 122.0, 120.5, 120.4, 115.9, 51.5,
41.9, 39.3, 34.1, 33.5, 33.2, 28.3, 25.1, 21.6, 21.3, 18.9,
18.8.
From the more polar fraction 3,6-dihydroxy-2-*60,60,90a-
trimethyl-40,50,50aS,60,70,80,90,90aS-octahydronaphtho[1,2-
c]furan-30-yl)-nitrobenzene *5d) *117 mg, 27%) was
isolated as yellow crystals mp 104.0±104.58C *Found: C,
67.83; H, 6.31; N, 3.88. C21H25NO5 requires: C, 67.91; H,
From the more polar fraction 2-acetyl-3-*60,60,90a-
trimethyl-40,50,50aS,60,70,80,90,90aS-octahydronaphtho[1,2-
c]furan-30-yl)-1,4-benzoquinone *6b) *147 mg, 80%;
referred to 0.5 equiv. of 3b) was isolated as red crystals
mp 145±1468C *Found: C, 75.24%; H, 7.33. C23H26O4
requires: C, 75.38; H, 7.15); IR n 1772 *CvO), 1713
25
6.78; N, 3.77); [a]D 1102.4* c, 21). IR n 3451 *OH),
1
2944 *C±H), 1532 *NO2). H NMR d 9.56 *s, 1H, 6-OH),
7.25 *s, 1H, H-10), 7.22 *d, 1H, J9.5 Hz, H-4), 7.12 *d, 1H,
J9.5 Hz, H-5), 5.77 *s, 1H, 3-OH), 2.57 *ddd, 1H, J1.6,
6.4, 16.9 Hz, H-40eq), 2.32 *ddd, 1H, J7.1, 11.4, 17.3 Hz,
H-40ax), 2.00 *br d, 1H, J11.8 Hz, H-90eq), 1.97±1.28 *m,
1
*CvO), 1672 *CvO). H NMR d 7.23 *s, 1H, H-10), 6.76
*s, 2H, H-5 and H-6), 2.92±2.73 *m, 2H, H-40), 2.40 *s, 3H,
MeCO), 1.97±1.23 *m, 8H), 1.20 *s, 3H, 90a-Me), 0.94*s,
3H, 60-Me), 0.90 *s, 3H, 60-Me0). 13C NMR d 200.7, 185.5,
185.4, 141.7, 139.5, 139.1, 138.2, 136.4, 136.0, 131.1,
130.6, 50.7, 41.7, 39.2, 34.1, 33.4, 33.1, 31.4, 24.9, 23.7,
21.5, 18.9, 18.8.
0
8H), 1.25 *s, 3H, 90a-Me), 0.94*s, 3H, 6 -Me), 0.91 *s, 3H,
60-Me0). 13C NMR d 148.7, 147.9, 139.2, 137.7, 136.8,
133.3, 124.6, 121.3, 121.1, 111.6, 51.2, 41.9, 39.2, 34.1,
33.5, 33.2, 25.1, 21.6, 21.1, 19.0, 18.8.
3.1.6. Reaction of furan 2 with in situ generated 2-cyano-
1,4-benzoquinone /3e). A stirred suspension of 2,5-di-
3.1.4. Reaction of furan 2 with 2-methoxycarbonyl-1,4-
benzoquinone /3c). A solution of 2 *270 mg, 1.23 mmol)
and quinone 3c *205 mg, 1.23 mmol) in dichloromethane
*35 mL) was left at room temperature for 20 h. The solvent
hydroxybenzonitrile *100 mg, 0.74mmol), furan
*162 mg, 0.74mmol), silver*I) oxide *927 mg, 4.0 mmol),
and sodium sulfate *500 mg) in dichloromethane *25 mL)
2