Tang et al.
JOCArticle
1H), 3.88-3.94 (m, 1H), 3.23 (s, 1H), 3.02 (s, 1H), 2.68-2.78 (m,
2H), 2.42-2.46 (m, 2H), 2.25-2.28 (m, 2H), 1.77-1.84 (m, 2H),
1.53-1.66 (m, 2H); 13C NMR (100 MHz, CDCl3) δ 164.0, 144.6,
141.8, 130.8, 130.0, 128.4, 128.3, 125.9, 121.6, 77.7, 72.2, 71.8, 42.5,
40.9, 39.7, 31.7, 29.8; IR ν (cm-1) 3399, 2921, 2855, 1710, 1494,
1385, 1250, 1054, 1020, 970, 818, 701, 575, 486.
130.6, 129.8, 128.4, 128.2, 126.1, 121.4, 77.7, 66.8, 48.5, 44.9,
39.1, 29.6, 29.3; IR ν (cm-1) 3424, 2922, 1710, 1383, 1248, 1046,
970, 817, 749, 701, 480; HRMS (ESI) calcd for C19H26NO4 [M þ
NH4]þ 332.1856, found 332.1850.
(þ)-Strictifolione 1 (Second-Generation Synthesis). To a stirred
suspension of tetramethylammonium triacetoxyborohydride
(145 mg, 0.55 mmol) in acetonitrile (0.5 mL) was added glacial
acetic acid (0.5 mL). The mixture was stirred at rt for 30 min. After
cooling to -20 °C, the β-hydroxy ketone 12 (35 mg, 0.11 mmol) in a
mixture of acetic acid and acetonitrile (v/v=1:1, 0.6 mL) was added
dropwise. The mixture was stirred at -20 °C for over 10 h. A satu-
rated solution of sodium potassium tartrate (2 mL) and EtOAc
(2 mL) was added followed by vigorous stirring at rt for 30 min. The
mixture was extracted with EtOAc (3 ꢀ 15 mL). The combined
organic layers were washed with water (5 mL), saturated aqueous
NaHCO3 solution (2 ꢀ 5 mL), and brine, dried over anhydrous
Na2SO4, filtered, and concentrated under reduced pressure to give a
residue which was purified by flash column chromatography on
silica gel (hexane/EtOAc, 1:2) to afford (þ)-strictifolione 1 (32 mg,
(E)-1,5-anti-Ene-diol 14. Diol 14 was prepared by a similar
protocol that was employed for the preparation of (E)-1,5-anti-
ene-diol 13 from 3-butenal 15, boryl-substituted allylborane 5,
and aldehyde 17 in 55% yield as a colorless oil: 92% ee; [R]20
D
þ1 (c=1.0, CHCl3); 1H NMR (400 MHz, CDCl3) δ 7.17-7.30
(m, 5H), 5.66-5.84 (m, 2H), 5.57 (dd, J = 15.2, 6.4 Hz, 1H),
5.09-5.14 (m, 2H), 4.14 (q, J=6.4 Hz, 1H), 3.94-4.04 (m, 5H),
3.60 (s, 1H), 2.67 (t, J = 8.4 Hz, 2H), 2.17-2.32 (m, 4H), 2.07
(s, 1H), 1.94-2.04 (m, 2H), 1.75-1.88 (m, 2H); 13C NMR (100
MHz, CDCl3) δ 141.6, 135.1, 134.4, 128.4, 128.2, 127.4, 125.8,
117.9, 111.5, 71.5, 67.4, 65.0, 64.7, 42.3, 41.8, 40.1, 39.1, 30.0; IR
ν (cm-1) 3420, 2925, 1642, 1496, 1428, 1311, 1133, 1034, 975,
916, 750, 702, 505; HRMS (ESI) calcd for C20H32NO4 [M þ
NH4]þ 350.2326, found 350.2320.
91% yield, dr = 96:4) as a white solid: mp 112-114 °C; [R]20
=
D
Biacrylate 25. Biacrylate 25 was prepared by a similar proto-
col that was employed for the preparation of biacrylate 18 from
þ43 (c=1.0, CHCl3); 1H NMR (400 MHz, CDCl3) δ 7.15-7.29
(m, 5H), 6.85-6.89 (m, 1H), 6.02 (dd, J=9.6, 1.6 Hz, 1H), 5.85 (dt,
J=15.6, 7.2 Hz, 1H), 5.65 (dd, J=15.6, 6.4 Hz, 1H), 4.86 (q, J=
3.2 Hz, 1H), 3.94-4.03 (m, 2H), 2.90-3.20 (br, 2H), 2.75-2.79 (m,
1H), 2.65-2.69 (m, 1H), 2.40-2.43 (m, 2H), 2.25-2.29 (m, 2H),
1.75-1.87 (m, 2H), 1.63 (t, J=6.0 Hz, 2H); 13C NMR (100 MHz,
CDCl3) δ 164.1, 144.9, 141.9, 131.4, 129.6, 128.4, 128.3, 125.8,
121.3, 77.8, 68.5, 68.2, 42.2, 40.2, 38.9, 32.1, 29.6; IR ν (cm-1) 3343,
2932, 1719, 1494, 1393, 1242, 1050, 967, 818, 751, 701, 484; HRMS
(ESI) calcdforC19H28NO4 [M þ NH4]þ 334.2013, found 334.2023.
(E)-1,5-anti-Ene-diol 28. Diol 28 was prepared by a similar
protocol that was employed for the preparation of (E)-1,5-anti-
ene-diol 13 from 3-butenal 15, boryl-substituted allylborane 29
(generated from lIpc2BH), and aldehyde 30 in 52% yield as a color-
less oil: 92% ee; [R]20D -2 (c=1.0, CHCl3); 1H NMR (400 MHz,
CDCl3) δ 7.15-7.29 (m, 5H), 5.66-5.82 (m, 2H), 5.57 (dd, J =
15.6, 6.4 Hz, 1H), 5.10-5.15 (m, 2H), 4.14 (d, J = 6.0 Hz, 1H),
3.90-3.99 (m, 5H), 3.58 (s, 1H), 2.61 (t, J=7.6 Hz, 2H), 2.16-2.32
(m, 4H), 1.86 (s, 1H), 1.81 (dd, J=14.4, 1.6 Hz, 1H), 1.59-1.73 (m,
5H), 1.37-1.42 (m, 2H); 13C NMR (100 MHz, CDCl3) δ 142.4,
135.0, 134.4, 128.3, 128.2, 127.6, 125.7, 117.9, 112.0, 71.6, 67.5, 64.9,
64.6, 42.1, 41.9, 40.1, 37.1, 35.8, 31.5, 23.5; IR ν (cm-1) 3428, 3025,
2931, 1641, 1496, 1427, 1314, 1137, 1040, 974, 827, 742, 701, 498;
HRMS (ESI) calcd for C22H32NaO4 [M þ Na]þ 383.2193, found
383.2186.
(E)-1,5-anti-ene-diol 14 in 95% yield as a colorless oil: [R]20
D
þ31 (c=1.0, CHCl3); 1H NMR (400 MHz, CDCl3) δ 7.16-7.28
(m, 5H), 6.37 (dt, J=17.2, 1.6 Hz, 2H), 6.05-6.12 (m, 2H), 5.79
(dt, J=10.4, 1.6 Hz, 2H), 5.68-5.72 (m, 2H), 5.52 (dd, J=15.6,
7.2 Hz, 1H), 5.33 (q, J = 6.4 Hz, 1H), 5.22-5.28 (m, 1H),
5.04-5.10 (m, 2H), 3.92-3.97 (m, 4H), 2.67 (dq, J=8.0, 2.4 Hz,
2H), 2.34-2.41 (m, 4H), 2.04 (q, J=7.6 Hz, 1H), 1.86-1.95 (m,
3H); 13C NMR (100 MHz, CDCl3) δ 165.4, 165.3, 141.9, 133.1,
131.3, 130.5, 130.4, 128.9, 128.8, 128.7, 128.3, 128.2, 125.7,
117.9, 109.9, 69.4, 64.9, 64.8, 40.1, 39.5, 38.9, 38.0, 29.9; IR
ν (cm-1) 3074, 2955, 2929, 1722, 1638, 1406, 1271, 1193, 1045,
973, 809, 702, 503; HRMS (ESI) calcd for C26H36NO6 [M þ
NH4]þ 458.2537, found 458.2532.
r,β-Unsaturated Lactone 26. R,β-Unsaturated lactone 26 was
prepared by a similar protocol that was employed for the pre-
paration of R,β-unsaturated lactone 19 from biacrylate 25 in
63% yield as a colorless oil: [R]20 þ52 (c = 1.0, CHCl3);
D
1H NMR (400 MHz, CDCl3) δ 7.17-7.28 (m, 5H), 6.82-6.87
(m, 1H), 6.38 (dd, J = 17.2, 1.2 Hz, 1H), 6.01-6.13 (m, 2H),
5.76-5.82 (m, 2H), 5.65 (dd, J = 15.6, 6.4 Hz, 1H), 5.23-5.29
(m, 1H), 4.87 (dt, J = 15.2, 6.4 Hz, 1H), 3.93-4.00 (m, 4H),
2.65-2.71 (m, 2H), 2.31-2.49 (m, 4H), 2.08 (dd, J = 14.8, 7.6
Hz, 1H), 1.87-1.95 (m, 3H); 13C NMR (100 MHz, CDCl3) δ
165.5, 163.8, 144.5, 141.8, 130.6, 130.3, 129.8, 128.7, 128.3, 128.2,
125.8, 121.6, 109.9, 77.7, 69.2, 64.9, 64.8, 40.4, 39.4, 38.1, 29.9, 29.6;
IR ν (cm-1): 3060, 2926, 1720, 1406, 1383, 1246, 1197, 1047, 972,
815, 702, 666; HRMS (ESI) calcd for C24H32NO6 [M þ NH4]þ
430.2224, found 430.2218.
Ketone 31. A solution of diol 28 (180 mg, 0.5 mmol) in wet
acetone (10 mL) containing PPTS (63 mg, 0.25 mmol) was
refluxed for 5 h. Excess solvent was then removed under reduced
pressure. The residual mixture was diluted with EtOAc, washed
with saturated aqueous NaHCO3 and brine, dried over Na2SO4,
and concentrated by rotary evaporation. Purification by flash
chromatography on silica gel (hexane/EtOAc, 2:1) afforded 144
Ketone 12. To a solution of compound 26 (83 mg, 0.2 mmol) in
4.0 mL of THF was added 1.0 mL of aqueous LiOH solution
(1.0 M, 1 mmol), and the mixture was stirred for 12 h at rt. Then
3.0 mL of aqueous HCl solution (2.0 M, 6 mmol) was added, and
the mixture was stirred for 3 h at rt. After that, it was quenched
with saturated aqueous NH4Cl solution, and the resulting
mixture was extracted with EtOAc (3 ꢀ 20 mL). The combined
organic layers were dried over anhydrous Na2SO4, filtered, and
concentrated under reduced pressure to give a residual oil which
was purified by flash column chromatography on silica gel
(hexane/EtOAc, 2:1) to afford the title compound 12 (49 mg,
mg (0.456 mmol, 91% yield) of ketone 31 as a colorless oil:
1
[R]20 -26 (c = 1.0, CHCl3); H NMR (400 MHz, CDCl3) δ
D
7.15-7.29 (m, 5H), 5.74-5.85 (m, 1H), 5.64-5.71 (m, 1H), 5.57
(dd, J = 15.6, 6.4 Hz, 1H), 5.10-5.15 (m, 2H), 4.14 (q, J = 6.4
Hz, 1H), 4.08 (s, 1H), 3.12 (s, 1H), 2.42-2.61 (m, 6H), 2.19-2.32
(m, 4H), 2.07 (s, 1H), 1.60-1.63 (m, 4H); 13C NMR (100 MHz,
CDCl3) δ211.6, 142.0, 135.6, 134.2, 128.3, 128.2, 126.9, 125.7, 118.1,
71.4, 67.1, 48.3, 43.4, 41.9, 39.2, 35.6, 30.8, 23.1; IR ν (cm-1) 3398,
2930, 1706, 1496, 1408, 1028, 975, 916, 746, 700, 638, 497; HRMS
(ESI) calcd for C20H28NaO3 [M þ Na]þ 339.1931, found 339.1941.
Acetonide 32. To a stirred suspension of tetramethylammo-
nium triacetoxyborohydride (316 mg, 1.2 mmol) in acetonitrile
(1.0 mL) was added glacial acetic acid (1.0 mL). The mixture was
stirred at rt for 30 min. After cooling to -20 °C, the β-hydroxy
ketone 31 (63 mg, 0.20 mmol) in a mixture of acetic acid and
acetonitrile (v/v = 1:1, 1.0 mL) was added dropwise. The mixture
78% yield) as a colorless oil: [R]20 þ58 (c = 1.0, CHCl3);
D
1H NMR (400 MHz, CDCl3) δ 7.16-7.29 (m, 5H), 6.85-6.90
(m, 1H), 6.38 (dt, J=9.6, 1.6 Hz, 1H), 5.79-5.87 (m, 1H), 5.66
(dd, J = 15.6, 6.4 Hz, 1H), 4.87 (dt, J = 15.2, 6.4 Hz, 1H),
4.08-4.13 (m, 1H), 3.17 (d, J=3.6 Hz, 1H), 2.90 (t, J=7.6 Hz,
2H), 2.77 (t, J=7.6 Hz, 2H), 2.40-2.61 (m, 4H), 2.19-2.31 (m,
2H); 13C NMR (100 MHz, CDCl3) δ 210.6, 163.9, 144.7, 140.5,
J. Org. Chem. Vol. 75, No. 23, 2010 8239