886
M. A. Brimble et al. / Tetrahedron 63 (2007) 880–887
0
0
dH 1.39 (3H, t, J 7.1 Hz, CH3), 3.31 (2H, d, J1 ,2 6.7 Hz,
which was purified by flash column chromatography on
silica (hexanes/ethyl acetate 9:1) to give the title compound
11 as a pale yellow oil (160 mg, 72%). C20H24O7 found
376.1522, requires 376.1522. nmax 3054, 2928, 1723, 1621,
1343, 1265. dH 1.40 (3H, t, J 7.1 Hz, CH3), 2.16 (3H, s,
30-H), 3.74 (3H, s, 4-OCH3), 3.86 (2H, s, 10-H), 3.93 (3H,
s, 7-OCH3), 3.96 (3H, 1-OCH3), 3.98 (3H, s, 5-OCH3),
4.41 (2H, q, J 7.1 Hz, OCH2), 6.61 (1H, d, J6,8 2.2 Hz,
6-H), 7.02 (1H, d, J8,6 2.2 Hz, 8-H). dC 14.1 (CH3, CH3),
29.2 (CH3, C-30), 42.4 (CH2, C-10), 55.4 (CH3, 7-OCH3),
56.2 (CH3, 5-OCH3), 61.6 (CH2, OCH2), 62.2 (CH3,
4-OCH3), 62.8 (CH3, 1-OCH3), 93.6 (CH, C-8), 100.6
(CH, C-6), 117.4 (C, C-4a), 119.8 (C, C-2 or C-3), 126.0
(C, C-3 or C-2), 131.5 (C, C-8a), 149.1 (C, C-1), 151.3 (C,
C-4), 157.3 (C, C-5), 158.8 (C, C-7), 167.6 (C, C]Oester),
206.4 (C, C-20).
10-H), 3.94 (3H, s, OCH3), 3.97 (3H, s, OCH3), 4.42 (2H,
0
0
q, J 7.1 Hz, OCH2), 5.09 (1H, dd, J3 (cis),2 10.0 Hz,
0
J3 (cis),3 (trans) 1.3 Hz, 30(cis)-H), 5.18 (1H, dd, J3 (trans),2
0
0
0
17.1 Hz, J3 (trans),3 (cis) 1.3 Hz, 30(trans)-H), 5.86 (1H, tdd,
0
0
J2 ,3 (trans) 17.1 Hz, J2 ,3 (cis) 10.0 Hz, J2 ,1 6.7 Hz, 20-H),
6.74 (1H, d, J6,8 2.4 Hz, 6-H), 7.23 (1H, d, J8,6 2.4 Hz,
8-H). dC 15.9 (CH3, CH3), 35.9 (CH2, C-10), 55.8 (CH3,
OCH3), 56.2 (CH3, OCH3), 61.3 (CH2, OCH2), 108.3 (CH,
C-8), 110.0 (CH, C-6), 116.2 (C, C-2), 118.1 (CH2, C-30),
132.7 (CH, C-20), 134.8 (C, C-8a), 139.7 (C, C-2), 149.8
(C, C-3), 165.4 (C, C-5), 165.8 (C, C]Oester), 170.3
(C, C-7), 181.2 (C, C-1), 181.7 (C, C-4).
0
0
0
0
0
0
3.12. Ethyl 3-allyl-1,4,5,7-tetramethoxynaphthalene-
2-carboxylate (18)
To a solution of ethyl 3-allyl-5,7-dimethoxy-1,4-naphtho-
quinone-2-carboxylate 17 (820 mg, 2.5 mmol) and tetrabu-
tylammonium iodide (97 mg, 2.6 mmol) in tetrahydrofuran
(50 mL) and water (25 mL) under nitrogen was added
sodium dithionite (2.6 g, 14.9 mmol) in water (30 mL).
After stirring the mixture for 15 min, potassium hydroxide
(3.20 g, 57.0 mmol) in water (20 mL) was added followed
by dimethyl sulfate (4.9 mL, 52.2 mmol). The solution
was stirred for 21 h then extracted into dichloromethane
(3ꢂ40 mL). The organic layer was washed with brine
(100 mL), dried (magnesium sulfate) and the solvent was
removed under vacuum to give a yellow oil. Purification
by flash column chromatography on silica (hexanes/ethyl
acetate 9:1) gave the title compound 18 as a beige wax
(500 mg, 55%). C20H24O6 found 360.1571, requires
360.1573. nmax 2936, 1726, 1621, 1342. dH 1.41 (3H, t,
3.14. (20S)-Ethyl 3-(20-hydroxypropyl)-1,4,5,7-tetra-
methoxynaphthalene-2-carboxylate (19)
To a stirred solution of (R)-Me-CBS catalyst (Aldrich,
1.6 mL, 1.6 mmol, 1 mol Lꢀ1 in toluene) in tetrahydrofuran
(0.5 mL) was added borane dimethyl sulfide (0.16 mL,
1.6 mmol, 10 mol Lꢀ1 in tetrahydrofuran). After stirring for
15 min, the mixture was cooled to ꢀ40 ꢁC and a solution of
methyl ketone 11 (30 mg, 0.08 mmol) in tetrahydrofuran
(1 mL) was added. After stirring for 2 h, methanol (0.2 mL)
was added followed by dilute hydrochloric acid (5 mL) and
the mixture was stirred for 5 min. The acidified mixture was
extracted with dichloromethane (20 mL), washed with satu-
rated sodium chloride (15 mL), dried (magnesium sulfate)
and the solvent was removed under vacuum to give a white
solid. Purification by flash column chromatography (hex-
anes/ethyl acetate 3:1) gave the title compound 19 as a yellow
oil (29 mg, 97%). The enantiomeric excess was determined
to be 65% (chiral HPLC, 24 cmꢂ0.4 mm Daicel AD-H
column, 90:10 hexanes/tert-butyl alcohol, retention time¼
44.3 min (major), 62.1 min (minor)). C20H26O7 found
378.1675, requires 378.1678. nmax 3583, 1726, 1620, 1341.
0
0
0
0
J 7.1 Hz, CH3), 3.56 (2H, dt, J1 ,2 6.2 Hz, J1 ,3 1.6 Hz,
10-H), 3.78 (3H, s, 4-OCH3), 3.92 (3H, s, 7-OCH3), 3.94
(3H, s, 5-OCH3), 3.98 (3H, s, 1-OCH3), 4.43 (2H, q,
J 7.1 Hz, OCH2), 4.98–5.06 (2H, m, 30-H), 5.96 (1H, tdd,
J2 ,3 (trans) 17.0 Hz, J2 ,3 (cis) 10.2 Hz, J2 ,1 6.2 Hz, 20-H),
6.58 (1H, d, J8,6 2.3 Hz, 8-H), 6.98 (1H, d, J6,8 2.3 Hz,
6-H). dc 14.2 (CH3, CH3), 31.3 (CH2, C-10), 55.4 (CH3,
7-OCH3), 56.2 (CH3, 1-OCH3), 61.3 (CH2, OCH2), 62.67
(CH3, 4-OCH3), 62.72 (CH3, 5-OCH3), 93.3 (CH, C-6),
100.2 (CH, C-8), 115.4 (CH2, C-30), 117.4 (C, C-4a),
123.9 (C, C-2 or C-3), 126.9 (C, C-3 or C-2), 130.7 (C,
C-8a), 137.1 (CH, C-20), 148.4 (C, C-5), 150.9 (C, C-4),
157.4 (C, C-1), 158.4 (C, C-7), 167.8 (C, C]O).
0
0
0
0
0
0
dH 1.25 (3H, d, J3 ,2 6.4 Hz, 30-H), 1.43 (3H, t, J 7.0 Hz,
CH3), 2.75–2.92 (3H, m, H10, OH), 3.79 (3H, s 4-OCH3),
3.92 (3H, s, 7-OCH3), 3.93 (3H, s, OCH3), 3.98 (3H, s,
OCH3), 4.07–4.13 (1H, m, 20-H), 4.46 (2H, q, J 7.0 Hz,
OCH2), 6.59 (1H, d, J6,8 2.2 Hz, 6-H), 6.98 (1H, d, J8,6
2.2 Hz, 8-H). dC 14.2 (CH3, CH3), 23.9 (CH3, C-30), 37.4
(CH2, C-10), 55.3 (CH3, 7-OCH3), 56.1 (CH3, OCH3), 61.6
(CH2, OCH2), 62.0 (CH3, 4-OCH3), 62.6 (CH3, OCH3),
68.8 (CH, C-20), 93.2 (CH, C-6 or C-8), 100.4 (CH, C-8 or
C-6), 117.3 (C, C-4a), 123.0 (C, C-3), 127.0 (C, C-2), 130.8
(C, C-8a), 148.5 (C, C-1 or C-5), 151.2 (C, C-4), 157.1 (C,
C-5 or C-1), 158.5 (C, C-7), 168.3 (C, C]Oester).
0
0
3.13. Ethyl 3-(20-oxopropyl)-1,4,5,7-tetramethoxynaph-
thalene-2-carboxylate (11)
A mixture of copper(I) chloride (73 mg, 0.74 mmol) and
palladium(II) chloride (23 mg, 0.13 mmol) in N,N-dimethyl-
formamide (12 mL) and water (2 mL) was stirred under an
oxygen atmosphere for 3 h. A solution of ethyl 3-allyl-
1,4,5,7-tetramethoxy-1,4-naphthoquinone-2-carboxylate 18
(21 mg, 0.58 mmol) in N,N-dimethylformamide (8 mL) was
added and the mixture was stirred for 66 h under an oxygen
atmosphere. Water (80 mL) was added to the reaction fol-
lowed by dilute hydrochloric acid until the cloudy solution
cleared. The mixture was extracted with ethyl acetate
(3ꢂ30 mL) and the organic phase was washed with water
(70 mL) and brine (70 mL) and dried (magnesium sulfate).
The solvent was removed under vacuum to give a yellow oil,
3.15. (3S)-3-Methyl-5,6,8,10-tetramethoxynaphtho-
[2,3-c]pyran-1-one (20)
A solution of alcohol 19 (14 mg, 0.4 mmol) in tetrahydro-
furan (1.5 mL) was stirred with sodium hydride (11 mg,
0.03 mmol) for 1 h under nitrogen. The reaction was
quenched with dilute sulfuric acid (2 mL) and then extracted
with ethyl acetate (20 mL). The organic layer was washed
with saturated sodium hydrogen carbonate (15 mL) and
saturated sodium chloride (15 mL), dried (magnesium sul-
fate) and the solvent was removed under vacuum to give