Journal of Natural Products
Article
10% (w/w) methanolic KOH (30 mL) solution dropwise. After
stirring for 18 h, CH2Cl2 (100 mL) was added and the white
precipitate dissolved. Water (100 mL) was then added and the phases
were separated. The organic phase was washed with HCl (1 M, 100
mL), NaHCO3 (saturated aqueous, 100 mL), and water (100 mL) and
dried. Concentration in vacuo and recrystallization from acetone−
cyclohexane gave the 3β-alcohol 14 (4.5 g, 99%) as colorless crystals:
mp 262.1−262.8 °C; IR (neat) νmax 3521, 3450, 3306, 3240, 2952,
2921, 2856, 1703, 1449, 1374, 1345, 1242, 1176, 1157, 1135, 1097,
at reflux for 2 d, the reaction mixture was cooled to rt and HCl (1M,
100 mL) added dropwise. After stirring for another 10 min the phases
were separated and the aqueous phase was extracted with CH2Cl2 (2 ×
100 mL). The combined organic phase was then concentrated in
vacuo, and the residue dissolved in minimal CH2Cl2 and subjected to
sgc (gravity, 3:97 acetone−CH2Cl2) to deliver an amorphous, colorless
solid. Recrystallization from acetone−n-hexane afforded diene 17 as
colorless needles (6.96 g, 72%): mp 132.3−132.9 °C; IR (neat) νmax
2931, 2920, 2852, 1710, 1704, 1447, 1416, 1379, 1315, 1273, 1214,
1
1
1073, 1040, 1036, 1007, 979, 953, 918, 862, 778, 668, 605 cm−1; H
1172, 1128, 1096, 1069, 1033, 884, 860, 741, 730, 613, 612 cm−1; H
NMR (300 MHz, CDCl3) δ 4.35 (1H, m, H-16α), 3.59 (1H, m, H-3α),
3.48 (1H, m, H-26β), 3.34 (1H, t, J = 10.8 Hz, H-26α), 2.51 (1H, t, J =
6.9 Hz, H-17α), 2.40 (1H, t, J = 14.4 Hz, H-11β), 2.22 (1H, m, H-11α),
2.11 (1H, m, H-15α), 1.91 (1H, m), 1.78 (3H, m), 1.59 (7H, m), 1.44
(4H, m), 1.36 (3H, m), 1.28 (1H, m), 1.11 (2H, m), 1.07 (3H), 1.04
(3H), 0.90 (3H), 0.78 (3H, d, J = 6.0 Hz); 13C NMR (126 MHz,
CDCl3) δ 213.1 (C-12), 108.7 (C-22), 78.7 (C-16), 70.3 (C-3), 66.4
(C-26), 55.3, 55.0, 54.6, 53.0, 44.1, 41.7, 37.3, 37.2, 36.0, 35.6, 33.8,
31.0, 30.9, 30.8, 30.7, 30.6, 29.6, 27.8, 16.6, 15.5, 12.7, 11.4; HRMS
(APCI+) m/z calcd for C27H42O4 430.30831, found 431.31643 [M +
H].
NMR (300 MHz, CDCl3) δ 4.69 (2H, m, H-26α,β), 3.26 (1H, d, J =
10.2 Hz, H-17α), 2.52 (1H, t, J = 13.2 Hz, H-11α), 2.30 (2H, m, H-2α,
H-4α), 2.24 (2H, m, H-15α, H-11β), 2.20 (2H, m, H-2β, H-4β), 2.17
(2H, m, H-23α,β), 1.87 (3H, m), 1.61 (4H, m), 1.72 (3H, s), 1.59 (3H,
s), 1.42 (4H, m), 1.16 (2H, m), 1.10 (3H, s), 0.96 (3H); 13C NMR
(126 MHz, CDCl3) δ 213.1 (C-12), 210.8 (C-3), 152.0 (C-22), 145.2
(C-25), 110.2 (C-26), 103.5 (C-20), 82.6 (C-16), 57.3, 55.5, 55.4,
54.4, 44.7, 38.2, 37.8, 37.5, 37.1, 35.1, 34.2, 33.9, 31.8, 31.2, 28.2, 24.4,
22.2, 14.0, 11.9, 11.2; HRMS (APCI+) m/z calcd for C27H38O3
410.28210, found 411.29094 [M + H]. Anal. Calcd for C27H38O3: C
78.98; H 9.33. Found: C 78.76; H 9.20.
3-Oxo-5α-Hecogenin (15). To a stirred suspension of 14 (1.0 g,
2.32 mmol) in acetone (50 mL) at rt was added Jones reagent (1.94
M, 25 mL). After stirring for 20 min, isopropyl alcohol (2 mL) was
added and the suspension turned from green to blue. After stirring an
additional 5 min, H2O (30 mL) and CH2Cl2 (50 mL) were added,
and, following separation of the phases, the aqueous phase was
extracted with CH2Cl2 (1 × 30 mL). The combined organic phase was
then dried, concentrated in vacuo, and recrystallized from acetone−
cyclohexane to provide 3,12-dione 15 (0.98 g, 99%) as colorless
crystals: mp 222.5−223.2 °C; IR (neat) νmax 2950, 2927, 2859, 1710,
1703, 1452, 1419, 1377, 1345, 1237, 1176, 1156, 1132, 1097, 1074,
3,12-Dioxo-(25R,25S)-dihydroxy-5α-furostan-20(22)-ene (18S,
18R). To a stirred suspension of AD mix α (137 mg, 1.41 g AD
mix α/mmol olefin) at 0 °C in t-BuOH−H2O (1:1; 3 mL) was added
17 (40 mg, 0.097 mmol). After vigorous stirring in the dark for 8 h at 0
°C, the suspension was allowed to equilibrate to rt. After stirring for an
additional 1 d, the suspension was cooled to 0 °C and Na2SO3 (40
mg) added. After stirring for an additional 2 h, CH2Cl2−H2O (1:1; 6
mL) was added and the phases were separated. After separation of the
phases the aqueous phase was extracted with CH2Cl2 (2 × 3 mL) and
the combined organic phase concentrated in vacuo, dissolved in
minimal CH2Cl2, and subjected to sgc (gravity, 1:39 i-PrOH−CH2Cl2)
to afford a mixture of 18R and 18S diols (21 mg, 49% combined) as an
amorphous, colorless solid. Separation of the diol mixture, dissolved in
minimal CH2Cl2, utilizing sgc (gravity, 1:39 i-PrOH−CH2Cl2,
performed twice) afforded 14 mg (33% overall) of 18S and 7 mg
(17% overall) of 18R as amorphous, colorless solids in a ratio of 2:1
(S:R). Recrystallization from acetone−cyclohexane afforded colorless,
twinned crystals: mp 152.4−152.9 °C; IR (neat) νmax 3342, 3274,
3243, 2931, 2920, 2852, 1710, 1704, 1447, 1416, 1379, 1315, 1273,
1214, 1172, 1128, 1096, 1069, 1033, 884, 860, 741, 730, 613, 612
1
1056, 1008, 980, 941, 920, 863, 778, 668, 609 cm−1; H NMR (300
MHz, CDCl3) δ 4.35 (1H, m, H-16α), 3.48 (1H, m, H-26β), 3.33 (1H,
t, J = 10.8 Hz, H-26α), 2.51 (1H, t, J = 6.9 Hz, H-17α), 2.40 (2H, m, H-
11β, 2α), 2.31 (3H, m, H-2β, H-4α,β), 2.22 (1H, m, H-11α), 2.11 (1H,
m, H-15α), 1.91 (1H, m), 1.78 (2H, m), 1.59 (5H, m), 1.44 (4H, m),
1.36 (3H, m), 1.28 (1H, m), 1.11 (2H, m), 1.07 (3H), 1.04 (3H), 0.90
(3H), 0.78 (3H, d, J = 6.0 Hz); 13C NMR (126 MHz, CDCl3) δ 213.1
(C-12), 210.8 (C-3), 108.7 (C-22), 78.6 (C-16), 66.4 (C-26), 54.9,
54.6, 54.4, 53.1, 45.7, 43.9, 41.7, 37.3, 35.7, 33.8, 33.8, 30.9, 30.7, 29.7,
28.3, 28.0, 27.5, 27.1, 16.6, 15.5, 12.7, 10.6; HRMS (APCI+) m/z calcd
for C27H40O4 428.29266, found 429.30102 [M + H].
1
cm−1; H NMR (300 MHz, CDCl3) δ 3.26 (1H, d, J = 10.2 Hz, H-
17α), 2.52 (1H, t, J = 13.2 Hz, H-11α), 2.30 (2H, m, H-2α, H-4α), 2.24
(2H, m, H-15α, H-11β), 2.20 (2H, m, H-2β, H-4β), 2.17 (2H, m, H-
23α,β), 1.87 (3H, m), 1.61 (4H, m), 1.72 (3H, s), 1.59 (3H, s), 1.42
(4H, m), 1.16 (2H, m), 1.10 (3H, s), 0.96 (3H); 13C NMR (126 MHz,
CDCl3) δ 213.1 (C-12), 210.8 (C-3), 152.0 (C-22), 103.5 (C-20),
82.6 (C-16), 76.5 (C-26), 72.0 (C-25), 57.9, 55.9, 55.6, 54.7, 44.7,
38.2, 37.8, 37.5, 37.1, 35.1, 34.2, 33.9, 31.8, 31.2, 28.2, 23.9, 22.2, 14.0,
11.9, 11.2; HRMS (APCI+) m/z calcd for C27H40O5 444.28758, found
409.27444 [M + H − 2H2O].
3,12-Dioxo-25-hydroxy-26-acetoxy-5α-furostan-20(22)-ene (19).
To a stirred solution of 18S (25 mg, 0.051 mmol) and DMAP (cat.) at
−10 °C under Ar in CH2Cl2−pyridine (3 mL; 2:1) was added
dropwise acetic anhydride (0.50 mL, 5.32 mmol). The solution, after
gradually equilibrating to rt for 22 h, was concentrated in vacuo, and
the residue was dissolved in CH2Cl2 (3 mL) and extracted with HCl
(1 M, 3 × 3 mL) and H2O (1 × 3 mL). The organic phase was dried,
concentrated in vacuo, dissolved in minimal CH2Cl2, and subjected to
sgc (gravity, 1:39 i-PrOH−CH2Cl2) to give 19 as an amorphous,
colorless solid (23 mg, 85%): mp 166.7−167.9 °C; IR (neat) νmax
3279, 3243, 2935, 2930, 2859, 1710, 1702, 1447, 1430, 1416, 1379,
1350, 1315, 1273, 1240, 1214, 1172, 1128, 1096, 1069, 1033, 884, 860,
741, 730, 613, 612 cm−1; 1H NMR (300 MHz, CDCl3) δ 3.26 (1H, d,
J = 10.2 Hz, H-17α), 2.52 (1H, t, J = 13.2 Hz, H-11α), 2.30 (2H, m, H-
2α, H-4α), 2.24 (2H, m, H-15α, H-11β), 2.20 (2H, m, H-2β, H-4β) 2.17
(2H, m, H-23α,β), 2.03 (3H, s, −OCOCH3), 1.87 (3H, m), 1.61 (4H,
m), 1.72 (3H, s) 1.59 (3H, s), 1.42 (4H, m), 1.16 (2H, m), 1.10 (3H,
s), 0.96 (3H); 13C NMR (126 MHz, CDCl3) δ 213.1 (C-12), 210.8
(C-3), 171.0 (-OCOCH3), 152.0 (C-22), 103.5 (C-20), 82.6 (C-16),
3,12-Dioxo-26-chloro-5α-furostan-20(22)-ene (16). To a stirred
solution of 15 (0.80 g, 1.87 mmol) and triphenylphosphine (1.30 g,
4.96 mmol) in 1,1,2,2-tetrachloroethane (20 mL) at rt under Ar was
added 2,6-lutidine (3.4 mL, 29.2 mmol), and the solution heated to
reflux for 5 d. After cooling to rt, the reaction was concentrated in
vacuo and dissolved in CH2Cl2−H2O (1:1; 40 mL). After separation
of the phases the aqueous phase was extracted with CH2Cl2 (2 × 20
mL) and the combined organic phase concentrated in vacuo, adsorbed
onto silica gel (gravity), and subjected to sgc (gravity, 1:48 i-PrOH−
CH2Cl2) to obtain an amorphous, light tan solid. Recrystallization
from acetone−cyclohexane yielded 26-chloride 16 as colorless needles
(0.45 g, 54%): mp 162.6−163.1 °C; IR (neat) νmax 2952, 2923, 2854,
1711, 1704, 1448, 1419, 1378, 1313, 1273, 1227, 1197, 1172, 1127,
1069, 1045, 985, 930, 857, 729, 613 cm−1; 1H NMR (300 MHz,
CDCl3) δ 4.66 (1H, m, H-16α), 3.40 (2H, m, H-26α,β), 3.22 (1H, d, J =
10.2 Hz, H-17α), 2.48 (1H, t, J = 6.9 Hz, H-11α), 2.25 (4H, m, H-11β,
H-2α, H-15α, H-4α), 2.11 (2H, m, H-23α,β), 1.82 (5H, m), 1.58 (6H,
m), 1.35 (2H, m), 1.18 (1H, m), 1.07 (3H, s), 0.98 (3H, s), 0.96 (3H,
s), 0.92 (3H); 13C NMR (126 MHz, CDCl3) δ 213.4 (C-12), 210.6
(C-3), 152.2 (C-22), 103.7 (C-20), 82.6 (C-16), 73.3 (C-3), 57.4,
55.6, 55.4, 54.3, 50.9, 44.5, 38.0, 37.3, 37.1, 34.9, 34.2, 33.8, 33.5, 31.3,
28.2, 27.2, 23.2, 17.6, 14.0, 11.8, 11.2; HRMS (APCI+) m/z calcd for
C27H39Cl35O3 446.25877, found 447.26564 [M(Cl35) + H]. Anal.
Calcd for C27H39Cl35O4: C 72.54; H 8.79. Found: C 72.58; H 9.14.
3,12-Dioxo-5α-furostan-20(22),25-diene (17). To a stirred sol-
ution of 16 (11.5 g, 23.4 mmol) in toluene (600 mL) at rt under Ar
was added potassium tert-butoxide (28.5 g, 254 mmol). After heating
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J. Nat. Prod. 2015, 78, 1067−1072