Formation of Agathic and Dihydroagathic Acids
J ournal of Natural Products, 1998, Vol. 61, No. 1 55
1
(c 1.1, CH3OH) [lit.26 [R]D +47.5° (c 0.8, CH3OH)]; H
NMR (CDCl3, 600 MHz) and 13C NMR (CDCl3, 90 MHz)
were as previously reported;26 HRFABMS m/z [M +
Na]+ 341.2092 (calcd for C20H30O3Na, 341.2092).
(13R,S)-dihydroagathic acid (6) as a colorless oil: [R]26
D
+44.5° (c 1.1, EtOH); HRFABMS m/z [M - H + 2 Na]+
1
381.2017 (calcd for C20H31O4Na2, 381.2017); H NMR
was closely comparable to that for (13S)-6; 13C NMR
identical with that for (13S)-6 except that all signals
were twinned.
Con ver sion of 2 t o La b d a -8(17),13-d ien e-15,19-
d ioic Acid (4). A 50 mL, two-necked round-bottomed
flask containing 32 mg of 2, 27 mg of NaCN, 2 mL of
CH3OH, two drops of acetic acid, and 183 mg of MnO2
was stirred under N2 at room temperature overnight.
After filtration through Celite, the filtrate was concen-
trated and diluted with water. The mixture was
extracted with diethyl ether, and the combined ether
extracts were dried and concentrated. The crude prod-
uct (24.4 mg) was purified by Si gel column chromatog-
raphy to give 14.5 mg of a mixture of 3E and 3Z:
HRFABMS (dimethyl ester) gave m/z [M + Na]+
385.2350 (calcd for C22H34O4Na+ 385.2354). GC/MS of
the combined methyl esters gave peaks at tR 8.90 (m/z
362) and tR 9.17 (m/z 362). A 9 mg mixture of 13,14-
(E,Z)-3 in 0.2 mL of CH3OH was mixed with 2 mL of
2% NaOH and stirred at room temperature. The
mixture was acidified with 1 N HCl and extracted with
CH2Cl2. The extract was dried over anhydrous Na2SO4
to give an oil that was purified over Si gel column
chromatography (7 × 0.5 cm CH2Cl2-CH3OH, 25:0.5)
to give 2 mg of 4E and 1 mg of 4Z.
Isola tion of Im br ica ta loic Acid (5). P. ponderosa
needles were extracted as described for the bark. After
repeated chromatograpy over silica gel, 21 mg of im-
bricataloic acid (5) was obtainted as a colorless oil:
[R]27D +43.3° (c 1.7, CHCl3); 1H NMR (CDCl3, 600 MHz)
was as previously reported;18,19 13C NMR (CDCl3, 90
MHz) δ 203.1 (C-15), 183.2 (C-19), 148.1 (C-8), 106.4 (C-
17), 56.5 (C-9), 56.3 (C-5), 50.8 (C-14), 44.2 (C-4), 40.6
(C-10), 39.2 (C-1), 38.7 (C-7), 38 (C-3), 36.1 (C-12), 29.0
(C-18), 28.9 (C-13), 26.0 (C-6), 21.2 (C-11), 20.2 (C-16),
19.9 (C-2), 12.8 (C-20); HRFABMS m/z [M + Na]+
343.2255 (calcd for C20H32O3Na, 343.2249).
Oxid a tion of Im br ica ta loic Acid (5) to Dih yd r oa -
ga th ic Acid (6). KMnO4 (23 mg, 0.125 mmol), dis-
solved in a mixture of 0.5 mL of H2O and 0.5 mL of
acetone, was added dropwise to 40 mg (0.125 mmol) of
imbricataloic acid (5) in 2 mL of acetone. The reaction
mixture was stirred at room temperature for 2 h, diluted
with 3.5 mL of H2O, and extracted with diethyl ether.
The ether layer was then extracted with 5% NaHCO3.
The NaHCO3 extract was washed with ether, and the
NaHCO3 aqueous layer was acidified with 0.1 N HCl
and reextracted with ether. The ether extract was dried
over MgSO4 and concentrated to an oil (12 mg). The
crude product was purified by silica gel column chro-
matography (7 × 0.5 cm, petroleum ether-EtOAc, 10:
1) to give 4 mg of labd-8(17)-ene-15,19-dioic acid (dihy-
droagathic acid) (6) as a colorless oil: [R]29D +34° (c 1.7,
EtOH) [lit.20 [R]D +33.8° (c 1, EtOH)]; 1H NMR (CDCl3,
600 MHz) and 13C NMR (CDCl3, 90 MHz) were closely
comparable to the reported spectral data;26,28 EIMS (50
eV) [M + dimethyl ester]+ m/z 364 (1), 305 (7), 304 (14),
289 (2), 235 (4), 221 (8), 189 (3), 181 (7), 161 (13), 149
(5), 122 (20), 121 (100); HRFABMS m/z [M + Na]+
359.2205 (calcd for C20H32O4Na, 359.2198).
Labda-8(17),13(E)-diene-15,19-dioic acid (4E) was
obtained as a colorless oil: [R]29 +55.5° (c 2.0, EtOH)
D
[lit.20 [R]D +56.1° (EtOH)]; 1H NMR (CD3OD, 600 MHz)
and 13C NMR (CDCl3, 90 MHz) were as reported;13,14,27
EIMS (50 eV) [M + dimethyl ester]+ m/z 362 (1), 347
(5), 303 (7), 302 (10), 288 (6), 235 (2), 221 (4), 189 (31),
173 (6), 161 (14), 149 (6), 122 (14), 121 (100); HRFABMS
m/z [M + Na]+ 357.2041 (calcd for C20H30O4Na,
357.2041).
Labda-8(17),13(Z)-diene-15,19-dioic acid (4Z) was ob-
tained as a colorless oil: [R]28 +14.8° (c 1.8, EtOH);
D
1H NMR (CD3OD, 600 MHz) δ 5.63 (1H, br s, H-14),
4.91 (1H, s, H-17b), 4.69 (1H, s, H-17a), 2.50 (2H, m,
H-12), 2.38 (1H, m, H-7), 2.10 (1H, m, H-3), 1.83-2.01
(5H, m, H-1, H-2, H-6, H-7), 1.88 (3H, d, J ) 1.2 Hz,
Me-16), 1.65-1.71 (2H, m, H-9, H-11), 1.46-1.56 (2H,
m, H-2, H-11), 1.33 (1H, dd, J ) 3, 12 Hz, H-5), 1.19
(3H, s, Me-18), 1.12 (1H, m, H-1), 1.02 (1H, dt, J ) 4.2,
13.2 Hz, H-3), 0.59 (3H, s, Me-20); 13C NMR (CDCl3, 90
MHz) δ 181.3 (C-19), 169.9 (C-15), 162.1 (C-13), 149.5
(C-8), 117.4 (C-14), 107.1 (C-17), 57.8 (C-5), 57.6 (C-9),
45.2 (C-4), 41.7 (C-10), 40.5 (C-1), 40 (C-7), 39.4 (C-3),
33.7 (C-12), 29.6 (C-18), 27.6 (C-6), 25.6 (C-16), 23.8 (C-
11), 21.2 (C-2), 13.4 (C-20); EIMS (50 eV) [M + dimethyl
ester]+ m/z 362 (2), 347 (6), 303 (11), 302 (14), 288 (6),
235 (8), 221 (5), 189 (37), 173 (7), 161 (18), 149 (9), 122
(13), 121 (100); HRFABMS m/z [M + Na]+ 357.2036
(calcd for C20H30O4Na, 357.2041).
Ack n ow led gm en t. We acknowledge financial sup-
port through a USDA grant, and financial support
through a fellowship afforded by the National Science
Council, Taipei, Taiwan. U.S. Department of Agricul-
ture, Agricultural Research Service, Northern Plains
Area, is an Equal Opportunity/Affirmative Action em-
ployer and all Agency services are available without
discrimination.
Refer en ces a n d Notes
(1) Lacey, J . R.; J ames, L. F.; Short, R. E. In The Ecology and
Economic Impact of Poisonous Plants on Livestock Production;
J ames, L. F., Ralphs, M., Neilson, D. B., Eds.; Westview Press:
Boulder, CO, 1988; pp 95-106.
(2) Al-Mahmoud, M. S.; Ford, S. P.; Short, R. E.; Farley, D. B.;
Christenson, L. K.; Rosazza, J . P. N. J . Agric. Food Chem. 1995,
43, 2154-2161.
(3) Gardner, D. R.; Molyneux, R. J .; J ames, L. F.; Panter, K. E.;
Stegelmeier, B. L. J . Agric. Food Chem. 1994, 42, 756-761.
(4) Ford, S. P.; Christenson, L. K.; Rosazza, J . P. N.; Short, R. E. J .
Anim. Sci. 1992, 70, 1604-1608.
(5) Short, R. E.; J ames, L. F.; Panter, K. E.; Staigmiller, R. B.;
Bellows, R. A.; Malcolm, J .; Ford, S. P. J . Anim. Sci. 1992, 70,
3498-3504.
(6) Short, R. E.; Ford, S. P.; Grings, E. E.; Kronberg, S. L. J . Anim.
Sci. 1995, 73, 2102-2104.
Red u ction of (E,Z)-Aga th ic Acid (4) to (13R,S)-
Dih yd r oa ga th ic Acid (6). To a refluxing and stirred
solution of (E,Z)-agathic acid (70 mg) in 8 mL of butanol
was added 380 mg of sodium metal. After 30 min, the
solution was cooled, diluted with water (10 mL), and
concentrated in vacuo to remove butanol. Acidification,
extraction with diethyl ether, drying, and evaporation
afforded 120 mg of a viscous residue. Purification by
silica gel column chromatography (petroleum ether-
EtOAc 6:1 or CH2Cl2-CH3OH 25:1) gave 40 mg of