PREPARATION OF 2,3-SECODIACIDS OF THE LUPANE SERIES

Article abstract of DOI:10.1135/cccc19941420

2,3-Seco-2,3-diacids of the 28-hydroxy-20(29)-lupene and 28-hydroxylupane series (VIIa and VIIb, respectively) and their derivatives VIII - XIV were prepared from 28-acetoxy-20(29)-lupen-3-one (IIIa) and 28-acetoxy-3-lupanone (IIIb), respectively, by oxidation to diosphenols Va and Vb and subsequent oxidative cleavage of the C(2)-C(3) bond.

Full text of DOI:10.1135/cccc19941420

1420
Endova, Klinotova, Sejbal, Maca, Klinot, Protiva:
PREPARATION OF 2,3-SECODIACIDS OF THE LUPANE SERIES*
Magdalena ENDOVA**, Eva KLINOTOVA, Jan SEJBAL, Bohumil MACA,
Jiri KLINOT and Jiri PROTIVA
Department of Organic Chemistry,
Charles University, 128 40 Prague 2, The Czech Republic
Received November 23, 1993
Accepted December 1, 1993
2,3-Seco-2,3-diacids of the 28-hydroxy-20(29)-lupene and 28-hydroxylupane series (VIIa and VIIb,
respectively) and their derivatives VIII – XIV were prepared from 28-acetoxy-20(29)-lupen-3-one
(IIIa) and 28-acetoxy-3-lupanone (IIIb), respectively, by oxidation to diosphenols Va and Vb and sub-
sequent oxidative cleavage of the C(2)−C(3) bond.
Triterpenoid A-seco derivatives are considerably widespread in nature and are assumed
to be a part of the plant defense system1. Most of the natural A-seco compounds are
3,4-seco-3-acids and their derivatives; they have been studied also from the biological
viewpoint (e.g. their antibacterial activities; see refs1,2 and references therein). On the
other hand, 2,3-secotriterpenoids are less common; some of them were also isolated
from natural sources (see, e.g. refs1,3–6), others were obtained by oxidative cleavage of
known triterpenoids7–9, including lupane derivatives10,11. Oxidative cleavage of ring A
is generally considered1 to be a simple way of introducing biological activity into triter-
penoid derivatives, comparable with other types of oxidative functionalization.
In the present paper we describe the preparation of 2,3-seco-2,3-dioic acids of the
lupane series with hydroxy group in position 28. Two parallel series of the acids were
synthesized: unsaturated acids (series a), prepared from 20(29)-lupene-3β,28-diol (Ia)
as the starting compound, and saturated acids (series b) the synthesis of which started
from the dihydro derivative of Ia, 3β,28-lupanediol (Ib). Both diols Ia and Ib were
acetylated with acetic anhydride in pyridine at 0 °C (for the procedure see ref.12) to
give 28-monoacetates IIa (described in ref.12,13) and IIb (ref.14) which were oxidized
with potassium dichromate to ketones IIIa (ref.13) and IIIb. Alkaline hydrolysis of the
* Part CIII in the series Triterpenes; Part CII: Collect. Czech. Chem. Commun. 58, 2737 (1993).
**Present address: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech
Republic, 166 10 Prague 6, The Czech Republic.
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1421
acetate groups led to hydroxy ketones IVa (ref.15) and IVb (ref.16). The ketone IVa was
recently isolated17 from the bark of Betula lenta L.
Ketones IIIa and IIIb were oxidized with oxygen in the presence of potassium
tert-butoxide to give diosphenols Va and Vb. With triterpenoid derivatives, this reaction
is used (see e.g. refs10,18–20) with small variations in the experimental conditions and
gives good yields of the desired 2,3-diketones. In our case, the best results were ob-
tained when the oxidation was performed in tert-butyl alcohol at about 40 °C for
20 – 30 min, the yields of diosphenols Va and Vb being 70 – 80%. The compounds Va
and Vb were accompanied with only minor amounts of further oxidative degradation
product which, according to spectral data and analogy19, are lactols VIa and VIb.
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Endova, Klinotova, Sejbal, Maca, Klinot, Protiva:
By analogy7,10, diosphenols Va and Vb were oxidatively cleaved with hydrogen per-
oxide in methanol in the presence of potassium hydroxide. As the principal products we
obtained diacids VIIa and VIIb; as side-products we isolated only monomethyl esters
with the ester functionality in position 2 (IXa and IXb) or 3 (Xa and Xb). These mono-
methyl esters, as well as the free acids VIIa and VIIb, were converted into dimethyl
esters VIIIa and VIIIb by treatment with ethereal diazomethane. Partial esterification of
acid VIIa with methanol afforded monoester IXa. Acetylation of dimethyl esters VIIIa
and VIIIb with acetic anhydride in pyridine at room temperature afforded 28-acetates
XIa and XIb; under these conditions, acids VIIa and VIIb were converted into anhy-
drides XIVa and XIVb.
In the saturated series b, we tried to obtain the 2,3-seco derivatives also by oxidative
cleavage of 2α-hydroxy-3-ketone XV which was prepared by reaction of ketone IIIb
with m-chloroperoxybenzoic acid in the presence of methanol and trace of sulfuric acid
according to a described21 procedure. The α-configuration of the hydroxy group on
C(2) in ketone XV follows from the values22 of coupling constants J(1α,2β) (12.7 Hz)
and J(1β,2β) (6.8 Hz). Oxidation of the hydroxy ketone XV with lead tetraacetate in
acetic acid at room temperature led to complex mixtures of products among which we
identified only anhydride XIVb. More advantageous was oxidation in acetic acid in the
presence of methanol: this gave the anhydride XIVb (24%) together with a mixture of
monomethyl esters XII and XIII (55%) which were not separated. According to
1H NMR spectrum, compound XII predominated in the mixture in the ratio 2 : 1. On
treatment with diazomethane, the mixture of monomethyl esters was converted into
dimethyl ester XIb.
1
The structure of the prepared compounds was confirmed by infrared, H NMR and
mass spectra. In the mass spectra of 2,3-secodiacids VIIa and VIIb and their esters VIIIa
and VIIIb – XIa and XIb, cleavage of the C(1)−C(10) and C(4)−C(5) bonds represented
the main fragmentation trend. The former cleavage leads to elimination of radical
•
ROOC(2)−C(1)H2 (59 and 73 mass units for R = H and R = CH3, respectively) or, with
hydrogen transfer, to elimination of acetic acid or its methyl ester (loss of 60 or 74
mass units). Analogously, cleavage of the C(4)−C(5) bond results in loss of radical
[ROOC(3)−C(4)(CH3)2]• (87 or 101 units for R = H or CH3) or a molecule of 2-methyl-
propanoic acid or its methyl ester (88 or 102 mass units). Moreover, the molecule loses
the substituent in position 17β (loss of radical •CH2OR, where R = H or COCH3) or
a molecule of water or acetic acid. The spectra exhibit relatively abundant ions corre-
sponding to combination of the mentioned losses; in the low mass region there are ions
of m/z 88 or 102, corresponding to 2-methylpropanoic acid or its methyl ester. On the
basis of this fragmentation it was possible to determine position of the ester and free
carboxyl groups in the monoesters IXa, IXb, Xa and Xb.
The isomeric monomethyl esters can also be distinguished by IR and 1H NMR spec-
tra: in the IR spectra of 2-methyl esters IXa and IXb both carbonyl bands appear at
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

Triterpenes
1423
lower wavenumbers (about 1 728 and 1 698 cm−1) than those of Xa and Xb with the
1
ester grouping in position 3 (1 740 and 1 718 cm−1). In the H NMR spectra, the chemi-
cal shifts of methoxyl singlets in 2-methyl esters IXa and IXb (δ 3.62) differ from those
in 3-methyl esters Xa and Xb (δ 3.67).
Compounds VIa, VIIa, VIIb, IXa, IXb, Xa and Xb exhibited no antibacterial activity
against Escherichia coli.
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Endova, Klinotova, Sejbal, Maca, Klinot, Protiva:
EXPERIMENTAL
The melting points were determined on a Kofler block and are uncorrected. The optical rotations
were measured in chloroform (c 0.3 – 0.8) on an automatic polarimeter ETL-NPL (Bendix–Ericsson),
accuracy ±2°. Infrared spectra were recorded in chlorofom on a PE 684 (Perkin–Elmer) spectrometer,
wavenumbers are given in cm−1. The 1H NMR spectra were measured on an FT-NMR spectrometer
Tesla BS 587 A (80 MHz) in deuteriochloroform with tetramethylsilane as internal standard. The
values of proton chemical shifts (ppm, δ-scale) and interproton coupling constants (in Hz) were obtained
by the first order analysis; the two-spin systems were analyzed as AB systems. Mass spectra were
measured on an INCOS 50 (Finnigan MAT) spectrometer, ionizing electron energy 70 eV, ion source
temperature 150 °C. The samples were introduced from direct exposure probe at heating rate 10 mA/s.
The identity of substances prepared by different procedures was checked by thin-layer chromato-
graphy, melting points and IR spectra. Thin-layer chromatography (TLC) was carried out on silica
gel G (Merck), detection by spraying with 10% sulfuric acid and heating, or on Silufol foils (Kavalier,
Votice), detection by 5% ethanolic phosphomolybdic acid and heating. Preparative TLC was per-
formed on silica gel G (Merck), column chromatography on silica gel Silpearl (Kavalier, Votice).
The “usual work-up procedure” denotes partition of the reaction mixture between water and ether,
washing the ethereal phase successively with water, dilute hydrochloric acid or sodium hydrogen car-
bonate solution, and water, drying over sodium sulfate and evaporation of the solvent. Analytical
samples were dried over phosphorus pentoxide at 100 °C under reduced pressure.
20(29)-Lupene-3β,28-diol 28-Acetate (IIa)
Diol Ia (13.9 g, 31.4 mmol) was treated with acetic anhydride (45 ml) in pyridine (100 ml) at 0 °C
for 50 min according to ref.12. The obtained mixture was chromatographed on silica gel in benzene–
ether (10 : 1 to 1: 1) to give monoacetate IIa (9.7 g, 64%), m.p. 217 – 219 °C (chloroform–methanol),
[α]D +13°. Reported12 m.p. 216 – 218 °C, [α]D +14.6°; ref.13 reports m.p. 275 °C (ethanol–ether),
[α]D +11°. In addition, the mixture afforded 20(29)-lupene-3β,28-diol diacetate (2.3 g, 14%) and the
starting diol Ia (0.5 g, 4%).
3β,28-Lupanediol 28-Acetate (IIb)
Diol Ib (8.3 g, 18.7 mmol) was converted into the title compound IIb (6.02 g, 66%) as described in
the preceding experiment; m.p. 242 – 244 °C (chloroform–methanol), [α]D −18° (reported14 m.p.
243 – 245 °C and (with erroneous sign) [α]D +21°). In addition, the mixture afforded lupane-3β,28-diol
diacetate (0.80 g, 8%) and the starting diol Ib (0.35 g, 4%).
28-Acetoxy-20(29)-lupen-3-one (IIIa)
A solution of monoacetate IIa (5.0 g, 10.3 mmol) and potassium dichromate (2.5 g, 8.5 mmol) in
acetic acid (350 ml) was set aside at room temperature for 2 days and the mixture was then worked
up in the usual manner. Crystallization from methanol afforded ketone IIIa (4.0 g, 80%), m.p.
114 – 118 °C, [α]D +36.5° (reported13 m.p. 238 °C (ethanol–ethyl acetate), [α]D +31.4}. IR spectrum:
1 725, 1 699, 1 640, 1 244, 890. Mass spectrum, m/z (%): 482 (M+, 15), 467 (2), 422 (15), 409 (17),
379 (4), 245 (14), 203 (62), 189 (46), 43 (100).
28-Acetoxy-3-lupanone (IIIb)
A solution of monoacetate IIb (0.85 g, 1.7 mmol) and potassium dichromate (0.65 g, 2.2 mmol) in
acetic acid (80 ml) was heated at 60 °C for 5 h and then set aside at room temperature for 3 days.
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

Triterpenes
1425
The mixture was worked up in the usual manner and the product was crystallized from methanol;
yield 0.83 g (98%) of ketone IIIb, m.p. 127 – 130 °C, [α]D +4°. IR spectrum: 1 725, 1 699, 1 245.
1H NMR spectrum: 0.78 d, 3 H (J = 6.6); 0.84 d, 3 H (J = 6.6); 0.94 bs, 3 H; 0.96 s, 3 H; 1.03 s,
3 H and 1.08 s, 6 H (7 × CH3); 2.05 s, 3 H (OAc); 2.3 – 2.6 m, 2 H (2 × H-2); 3.82 d, 1 H and 4.26 d,
1 H (2 × H-28, J = 11). Mass spectrum, m/z (%): 484 (M+, 18), 441 (2), 424 (7), 411 (36), 381 (5),
205 (45), 191 (53), 43 (100). For C32H52O3 (484.8) calculated: 79.29% C, 10.81% H; found: 79.05% C,
10.96% H.
28-Hydroxy-20(29)-lupen-3-one (IVa)
A solution of ketone IIIa (500 mg, 1.04 mmol) in benzene (5 ml) was mixed with 3% ethanolic
solution (5 ml) of potassium hydroxide. After refluxing for 1 h, the mixture was processed in the
usual manner to give ketone IVa (430 mg, 94%), m.p. 180 – 182 °C (ether–heptane), [α]D +49° (re-
1
ported15 m.p. 188 – 189 °C, [α]D +54°). IR spectrum: 3 624, 1 697, 1 639, 889. H NMR spectrum:
0.93 s, 3 H; 0.99 s, 3 H; 1.02 s, 3 H; 1.07 s, 6 H and 1.75 bs, 3 H (6 × CH3); 2.3 – 2.6 m, 2 H
(2 × H-2); 3.33 d, 1 H and 3.81 bd, 1 H (2 × H-28, J ≈ 11); 4.58 bs, 1 H and 4.69 bs, 1 H (2 ×
H-29). Mass spectrum, m/z (%): 440 (M+, 25), 422 (12), 409 (65), 203 (77), 189 (69), 81 (99), 55
(100).
28-Hydroxy-3-lupanone (IVb)
Ketone IIIb (500 mg, 1.03 mmol) was hydrolyzed analogously as described for ketone IIIa. The title
ketone IVb (420 mg, 92%) melted at 209 – 212 °C (ether–heptane), [α]D +12° (reported16 m.p. 210 °C).
1
IR spectrum: 3 624, 1 698. H NMR spectrum: 0.77 d, 3 H (J = 6.6); 0.85 d, 3 H (J = 6.4); 0.94 s,
3 H; 0.97 s, 3 H; 1.03 s, 3 H and 1.07 s, 6 H (7 × CH3); 2.3 – 2.6 m, 2 H (2 × H-2); 3.30 d, 1 H
and 3.78 d, 1 H (2 × H-28, J = 11). Mass spectrum, m/z (%): 442 (M+, 12), 424 (2), 411 (100), 205
(55), 191 (67).
Oxidation of Ketone IIIa
Ketone IIIa (500 mg, 1.04 mmol) was added to a solution of potassium tert-butoxide, prepared by
dissolving 1.6 g of potassium in 40 ml of tert-butyl alcohol. The solution was warmed to 40 °C for
30 min under constant introduction of oxygen, then poured into dilute hydrochloric acid and worked
up in the usual manner. Chromatography of the product mixture (420 mg) on silica gel (40 g) in
benzene and then in benzene–ether (10 : 1) afforded diosphenol Va (370 mg, 78%), m.p. 215 – 218 °C
(ether) or 146 – 150 °C (chloroform–heptane), [α] +61°. IR spectrum: 3 623, 3 450, 1 666, 1 644,
1
889. H NMR spectrum: 0.97 s, 3 H; 1.09 s, 3 H; 1.10 s, 3 H; 1.12 s, 3 H; 1.19 s, 3 H and 1.68 bs,
3 H (6 × CH3); 3.34 d, 1 H (J = 11) and 3.80 dd, 1 H (J = 11 and 1.7, 2 × H-28); 4.60 m, 1 H and
4.69 m, 1 H (2 × H-29); 6.42 s, 1 H (H-1). Mass spectrum, m/z (%): 454 (M+, 28), 436 (5), 424 (13),
423 (8), 326 (12), 229 (23), 189 (41), 43 (100). For C30H46O3 (454.7) calculated: 79.25% C, 10.20% H;
found: 79.43% C, 10.31% H.
Further elution afforded lactol VIa (30 mg, 6%), m.p. 194 – 196 °C (chloroform–heptane), [α]D
1
+18.5°. IR spectrum: 3 627, 3 599, 1 720, 1 640, 889. H NMR spectrum: 1.01 s, 3 H; 1.03 s, 3 H;
1.07 s, 3 H; 1.19 s, 3 H; 1.26 s, 3 H and 1.67 bs, 3 H (6 × CH3); 3.35 d, 1 H and 3.79 d, 1 H (2 ×
H-28, J = 11); 4.58 m, 1 H and 4.68 m, 1 H (2 × H-29); 5.30 bs, 1 H (H-1, W1/2 = 15 Hz). Mass
spectrum, m/z (%): 458 (M+, 3), 440 (4), 427 (15), 412 (29), 399 (25), 245 (61), 189 (62), 95 (100).
For C29H46O4 (458.7) calculated: 75.94% C, 10.11% H; found: 75.87% C, 10.03% H.
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Endova, Klinotova, Sejbal, Maca, Klinot, Protiva:
Oxidation of Ketone IIIb
Ketone IIIb (900 mg, 1.86 mmol) was treated as described in the preceding experiment to give dios-
phenol Vb (690 mg, 81%), m.p. 219 – 222 °C (ether–heptane), [α]D +13°. IR spectrum: 3 624, 3 452,
1
1 667, 1 645. H NMR spectrum: 0.78 d, 3 H (J = 6.5); 0.90 d, 3 H (J = 6.5); 0.95 s, 3 H; 1.10 s, 3 H;
1.11 s, 3 H; 1.13 s, 3 H and 1.21 s, 3 H (7 × CH3); 3.31 d, 1 H (J = 11) and 3.77 dd, 1 H (J = 11
and 1.4, 2 × H-28); 6.43 s, 1 H (H-1). Mass spectrum, m/z (%): 456 (M+, 35), 438 (12), 426 (32),
425 (28), 328 (22), 229 (38), 191 (82), 43 (100). For C30H48O3 (456.7) calculated: 78.90% C, 10.59% H;
found: 79.03% C, 10.87% H.
Lactol VIb (120 mg, 14%) was obtained as a side-product; m.p. 186 – 189 °C (ether–heptane),
1
[α]D −17°. IR spectrum: 3 625, 3 602, 1 721. H NMR spectrum: 0.76 d, 3 H (J = 6.5); 0.84 d, 3 H
(J = 6.5); 1.02 s, 6 H; 1.08 s, 3 H; 1.19 s, 3 H and 1.26 s, 3 H (7 × CH3); 3.32 d, 1 H and 3.77 d,
1 H (2 × H-28, J = 11); 5.29 bs, 1 H (H-1, W1/2 = 16 Hz). Mass spectrum, m/z (%): 442 (M+ − 18, 2),
429 (8), 414 (22), 411 (13), 401 (32), 247 (58), 191 (100). For C29H48O4 (460.7) calculated: 75.61% C,
10.50% H; found: 75.55% C, 10.73% H.
Oxidative Cleavage of Diosphenol Va
Diosphenol Va (720 mg, 1.58 mmol) and 30% aqueous solution of hydrogen peroxide (2.5 ml) were
added to a solution of potassium hydroxide (3 g) in methanol (110 ml). A further amount (10 ml) of
hydrogen peroxide was added portionwise into the reaction mixture in the course of the 100 minutes’
boiling. The reaction was quenched by pouring the mixture into dilute hydrochloric acid. The precipi-
tate was collected on filter, dissolved in chloroform and the solution was filtered through a layer of
silica gel. Chromatography on silica gel (80 g) in benzene and then benzene–ether (10 : 1 to 1 : 1)
afforded successively monomethyl esters Xa (60 mg, 8%) and IXa (30 mg, 4%) and diacid VIIa
(570 mg, 74%).
Diacid VIIa: m.p. 174 – 178 °C (ether–heptane), [α ]D +57°. IR spectrum: 3 621, 3 500 – 2 600,
1 706, 1 641, 891. Mass spectrum, m/z (%): 488 (M+, 1), 470 (2.5), 457 (6), 456 (4), 439 (3), 428
(10), 401 (22), 383 (35), 371 (18), 341 (20), 189 (63), 155 (35), 121 (90), 88 (27), 95 (100).
Dimethyl ester VIIIa was prepared from diacid VIIa and from monoesters IXa and Xa by treatment
with ethereal solution of diazomethane; m.p. 145 – 147 °C (heptane), [α]D +16°. IR spectrum: 3 625,
1 731, 1 719, 1 639, 1 434, 1 154, 888. 1H NMR spectrum: 0.90 s, 3 H; 1.01 s, 3 H; 1.02 s, 3 H;
1.23 s, 6 H and 1.67 bs, 3 H (6 × CH3); 2.34 m, 4 H; 3.33 d, 1 H and 3.78 d, 1 H (2 × H-28, J = 11);
3.60 s, 3 H and 3.64 s, 3 H (2 × OCH3); 4.57 m, 1 H and 4.66 m, 1 H (2 × H-29). Mass spectrum,
m/z (%): 516 (M+, 1), 498 (1), 486 (2), 485 (4), 457 (4), 443 (13), 442 (10), 425 (6), 415 (11), 397
(18), 385 (16), 341 (75), 169 (60), 121 (84), 102 (100), 95 (96). For C32H52O5 (516.8) calculated:
74.38% C, 10.14% H; found: 74.12% C, 9.92% H.
Monomethyl ester IXa: m.p. 133 – 136 °C (ether–heptane), [α]D +22°. IR spectrum: 3 624, 3 507
1
(broad), 1 728, 1 698, 1 639, 1 435, 1 157, 889. H NMR spectrum: 0.93 s, 3 H; 1.02 s, 3 H; 1.03 s,
3 H; 1.26 s, 6 H and 1.67 bs, 3 H (6 × CH3); 2.45 m, 4 H; 3.34 d, 1 H and 3.77 d, 1 H (2 × H-28,
J = 11); 3.62 s, 3 H (OCH3); 4.58 m, 1 H and 4.67 m, 1 H (2 × H-29). Mass spectrum, m/z (%): 502
(M+, 0.5), 484 (0.5), 471 (1.5), 429 (2.5), 428 (2.5), 415 (4), 397 (6), 385 (5), 341 (13), 169 (15), 88
(18), 43 (100).
Monomethyl ester Xa: m.p. 248 – 250 °C (chloroform–heptane), [α]D +18°. IR spectrum: 3 618,
1
3 507 (broad), 1 740, 1718, 1 644, 1 433, 1 148, 888. H NMR spectrum: 0.93 s, 3 H; 1.00 s, 3 H;
1.04 s, 3 H; 1.23 s, 3 H; 1.24 s, 3 H and 1.67 bs, 3 H (6 × CH3); 3.35 d, 1 H and 3.80 d, 1 H (2 ×
H-28, J = 11); 3.67 s, 3 H (OCH3); 4.58 m, 1 H and 4.68 m, 1 H (2 × H-29). Mass spectrum, m/z
(%): 502 (M+, 1), 484 (2), 471 (3), 443 (5), 442 (6), 401 (8), 383 (16), 371 (7), 341 (9), 155 (25),
102 (100).
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1427
Acetyl derivative XIa was prepared from dimethyl ester VIIIa (130 mg, 0.25 mmol) by treatment
with acetic anhydride (1 ml) in pyridine (5 ml) at room temperature for 3 days, followed by the usual
work-up; yield 80 mg (57%) of acetyl derivative XIa, m.p. 134 – 136 °C, [α]D +9°. IR spectrum:
1 725, 1 640, 1 434, 1 244, 1 153, 888. 1H NMR spectrum: 0.90 s, 3 H; 1.00 s, 3 H; 1.03 s, 3 H;
1.23 s, 6 H and 1.67 bs, 3 H (6 × CH3); 2.06 s, 3 H (OAc); 2.35 m, 3 H; 3.61 s, 3 H and 3.64 s, 3 H
(2 × OCH3); 3.85 d, 1 H and 4.24 bd, 1 H (2 × H-28, J = 11); 4.58 m, 1 H and 4.68 m, 1 H (2 ×
H-29). Mass spectrum, m/z (%): 558 (M+, 0.5), 527 (1), 499 (2), 498 (1), 485 (6), 484 (4), 457 (3),
425 (8), 397 (16), 383 (26), 323 (26), 169 (100), 102 (53). For C34H54O6 (558.8) calculated: 73.08% C,
9.74% H; found: 72.82% C, 10.05% H.
Anhydride XIVa
A solution of diacid VIIa (200 mg, 0.41 mmol) in a mixture of pyridine (4 ml) and acetic anhydride
(1 ml) was allowed to stand at room temperature for 4 h. The usual work-up afforded anhydride
XIVa (110 mg, 52%), m.p. 155 – 158 °C (ether–heptane), [α]D +51°. IR spectrum: 1 796, 1 752,
1
1 731, 1 640, 1 242, 891. H NMR spectrum: 0.99 s, 3 H; 1.04 s, 3 H; 1.07 s, 3 H; 1.26 s, 3 H; 1.37 s,
3 H and 1.68 bs, 3 H (6 × CH3); 2.06 s, 3 H (OAc); 2.12 d, 1 H and 2.84 d, 1 H (2 × H-1, J = 13.9);
3.82 d, 1 H and 4.27 bd, 1 H (2 × H-28, J = 10.3); 4.60 m, 1 H and 4.69 m, 1 H (2 × H-29). Mass
spectrum, m/z (%): 512 (M+, 1), 484 (1.5), 452 (5.5), 439 (4), 424 (3.5), 409 (2), 342 (2), 43 (100).
For C32H48O5 (512.7) calculated: 74.96% C, 9.44% H; found: 74.71% C, 9.21% H.
Partial Esterification of Diacid VIIa
A mixture of diacid VIIa (200 mg, 0.41 mmol), methanol (20 ml) and concentrated sulfuric acid
(1 ml) was refluxed for 1.5 h. The usual work-up and chromatography on silica gel (15 g) in light
petroleum–ether (1 : 1) and then in ether afforded diester VIIIa (55 mg, 26%), monoester IXa
(95 mg, 46%) and the starting diacid VIIa (40 mg, 20%); the obtained compounds were identical
with the authentic compounds obtained as described above.
Oxidative Cleavage of Diosphenol Vb
To a solution of diosphenol Vb (200 mg, 0.44 mmol) and potassium hydroxide (650 mg) in methanol
(30 ml) was added 30% aqueous solution of hydrogen peroxide (1.1 ml); a further portion of the
peroxide (1.1 ml) was added after boiling for 20 min. The mixture was then boiled for 1 h, poured
into dilute hydrochloric acid and worked up as usual. Chromatography on silica gel (30 g, elution
with light petroleum–ether 5 : 3 to 1 : 1 and then with ether) afforded successively monomethyl
esters Xb (45 mg, 20%) and IXb (25 mg, 11%) and diacid VIIb (105 mg, 49%).
Diacid VIIb: m.p. 166 – 169 °C (ether–heptane). IR spectrum: 3 625, 3 500 – 2 400, 1 706. Mass
spectrum, m/z (%): 490 (M+, 1), 472 (3), 459 (9), 441 (6), 430 (9), 413 (9), 385 (77), 373 (14), 343
(9), 155 (42), 55 (100).
Dimethyl ester VIIIb was prepared by treatment of diacid VIIb or monomethyl esters IXb and Xb
with ethereal solution of diazomethane; m.p. 149 – 152 °C (ether–methanol), [α]D −11°. IR spectrum:
1
3 624, 1 729, 1 719, 1 434, 1 153. H NMR spectrum: 0.76 d, 3 H (J = 6.5); 0.84 d, 3 H (J = 6.5);
0.92 s, 3 H; 0.99 s, 3 H; 1.03 s, 3 H and 1.24 s, 6 H (7 × CH3); 2.35 m, 3 H; 3.31 d, 1 H and 3.77 d,
1 H (2 × H-28, J = 11); 3.61 s, 3 H and 3.65 s, 3 H (2 × OCH3). Mass spectrum, m/z (%): 518 (M+, 1),
500 (1), 487 (9), 445 (5), 417 (6), 399 (15), 387 (7), 343 (32), 169 (60), 102 (100), 95 (98). For
C32H54O5 (518.8) calculated: 74.09% C, 10.49% H; found: 73.88% C, 10.21% H.
Monomethyl ester IXb: m.p. 190 – 194 °C (ether–heptane), [α]D −10°. IR spectrum: 3 624, 3 505
1
(broad), 1 728, 1 698, 1 435, 1 156. H NMR spectrum: 0.76 d, 3 H (J = 6.5); 0.84 d, 3 H (J = 6.5);
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1428
Endova, Klinotova, Sejbal, Maca, Klinot, Protiva:
0.94 s, 3 H; 0.99 s, 3 H, 1.04 s, 3 H and 1.26 s, 6 H, (7 × CH3); 2.41 m, 3 H; 3.31 d, 1 H and 3.77 d,
1 H (2 × H-28, J = 11); 3.63 s, 3 H (OCH3). Mass spectrum, m/z (%): 504 (M+, 0.1), 486 (0.2), 473
(1), 455 (1), 431 (1.2), 430 (1.5), 417 (5), 399 (20), 343 (20), 169 (45), 88 (19), 95 (100), 43 (99).
Monomethyl ester Xb: m.p. 243 – 247 °C (ether–heptane). IR spectrum: 3 614, 3 515 (broad),
1
1 740, 1 718, 1 433, 1 145. H NMR spectrum: 0.75 d, 3 H (J = 6.5); 0.84 d, 3 H (J = 6.5); 0.93 s,
3 H; 0.96 s, 3 H; 1.04 s, 3 H; 1.24 s, 3 H and 1.25 s, 3 H (7 × CH3); 2.38 m, 3 H; 3.31 d, 1 H and
3.78 d, 1 H (2 × H-28, J = 11); 3.67 s, 3 H (OCH3). Mass spectrum, m/z (%): 504 (M+, 1), 486 (4),
473 (7), 445 (11), 444 (12), 427 (4), 413 (6), 403 (18), 385 (65), 343 (25), 191 (80), 155 (40), 102
(100).
Acetyl derivative XIb was obtained either from dimethyl ester VIIIb by treatment with acetic an-
hydride in pyridine under conditions described for compound XIa or by reaction of a mixture of
monomethyl esters XII and XIII with ethereal diazomethane; m.p. 128 – 132 °C (methanol), [α]D
1
−17°. IR spectrum: 1 720, 1 434, 1 245, 1 153. H NMR spectrum: 0.75 d, 3 H (J = 6.3); 0.83 d, 3 H
(J = 6.3); 0.92 s, 3 H; 0.98 s, 3 H; 1.03 s, 3 H and 1.39 s, 6 H (7 × CH3); 2.04 s, 3 H (OAc); 2.23 m,
3 H; 3.60 s, 3 H and 3.65 s, 3 H (2 × OCH3); 3.81 d, 1 H and 4.24 bd, 1 H (2 × H-28, J = 10.7).
Mass spectrum, m/z (%): 501 (M+ − 59, 1), 500 (0.3), 487 (2), 459 (1), 427 (5), 399 (12), 385 (12),
325 (14), 191 (50), 169 (90), 102 (60), 43 (100). For C34H56O6 (560.8) calculated: 72.82% C, 10.06% H;
found: 72.57% C, 9.82% H.
28-Acetoxy-2α-hydroxylupan-3-one (XV)
A solution of sulfuric acid in methanol (25 ml of 0.05% solution) was added to a solution of ketone
IIIb (500 mg, 1.03 mmol) and 70% m-chloroperoxybenzoic acid (500 mg, 2.03 mmol) in dichloro-
methane (12.5 ml) and the mixture was set aside at room temperature for 5 h. After addition of ether
(50 ml), the solution was successively washed with water, solutions of potassium iodide, sodium
thiosulfate and sodium hydrogen carbonate, and with water. After drying over sodium sulfate and
evaporation of the solvent, the crude product (460 mg) was dissolved in a mixture of benzene–ether
(10 : 1) and the solution was filtered through a small column of silica gel. Crystallization from ether
afforded hydroxy ketone XV (440 mg, 85%), m.p. 168 – 172 °C, [α]D −15°. IR spectrum: 3 487,
1 727, 1 703, 1 245. 1H NMR spectrum: 0.76 d, 3 H (J = 6.5); 0.84 d, 3 H (J = 6.5); 0.93 s, 3 H;
1.10 s, 6 H; 1.15 s, 3 H and 1.18 s, 3 H (7 × CH3); 2.06 s, 3 H (OAc); 2.47 dd, 1 H (H-1β, J(1α, 1β)
= 13.0, J(1β, 2β) = 6.8); 3.28 bs, 1 H (OH); 3.80 d, 1 H and 4.27 d, 1 H (2 × H-28, J = 11); 4.54 dd,
1 H (H-2β, J(1α,2β) = 12.7, J(1β, 2β) = 6.8). Mass spectrum, m/z (%): 500 (M+, 16), 482 (2), 440
(7), 427 (13), 397 (4), 191 (44), 43 (100). For C32H52O4 (500.8) calculated: 76.75% C, 10.47% H;
found: 76.47% C, 10.51% H.
Oxidative Cleavage of Hydroxy Ketone XV
Methanol (2 ml) and lead tetraacetate (300 mg, 1.15 mmol) were added in two equivalent portions to
a solution of hydroxy ketone XV (200 mg, 0.4 mmol) in acetic acid (20 ml), the second portion being
added after stirring at room temperature for 2 h. After standing for further 15 h at room temperature,
the reaction mixture was worked up in the usual manner and the products were separated by chroma-
tography on silica gel (24 g; elution with light petroleum–ether 10 : 3, 5 : 3, and then with ether);
yield 50 mg (24%) of anhydride XIVb and 120 mg (55%) of a mixture of methyl esters XII and XIII
in the ratio of 2 : 1.
Anhydride XIVb: m.p. 202 – 204 °C (ether–heptane), [α]D +18.5°. IR spectrum: 1 796, 1 752,
1
1725, 1 245. H NMR spectrum: 0.77 d, 3 H (J = 6.5); 0.85 d, 3 H (J = 6.5); 0.97 s, 3 H; 1.06 s, 3
H; 1.08 s, 3 H; 1.27 s, 3 H and 1.38 s, 3 H (7 × CH3); 2.06 s, 3 H (OAc); 2.23 d, 1 H and 2.85 d,
1 H (2 × H-1, J = 14); 3.80 d, 1 H and 4.26 d, 1 H (2 × H-28, J = 11). Mass spectrum, m/z (%): 514
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

Triterpenes
1429
(M+, 2), 454 (15), 441 (13), 426 (4), 411 (4), 397 (3), 191 (56), 43 (100). For C32H50O5 (514.8)
calculated: 74.67% C, 9.79% H; found: 74.49% C, 9.53% H. Anhydride XIVb was also obtained from
diacid VIIb by treatment with acetic anhydride in pyridine under conditions described for anhydride
XIVa.
Mixture of monomethyl esters XII and XIII: IR spectrum: 3 516 (broad), 1 728, 1 700 sh, 1 435,
1
1 246, 1 155. H NMR spectrum: 0.76 d (J = 6.3); 0.84 d (J = 6.3); 0.95 s, 0.99 s and 1.05 s (5 × CH3);
1.24 s and 1.25 s (2 × CH3 in isomer XII); 1.27 s (2 × CH3 in isomer XIII); 2.05 s, (OAc); 2.3 – 2.5 m;
3.64 s (OCH3 of isomer XII); 3.66 s (OCH3 of isomer XIII); 3.81 d and 4.25 d (2 × H-28, J = 11).
Mass spectrum, m/z (%): 486 (M+ − 60, 0.5), 473 (0.5), 459 (0.5), 445 (1), 427 (1), 413 (2), 399 (6),
385 (8), 325 (6), 191 (40), 169 (50), 43 (100).
The authors are indebted to Dr S. Hilgard for measurement of IR spectra and to Mrs J. Cecrdlova for
elemental analyses. Their thanks are also due to Dr I. Votruba (Institute of Organic Chemistry and
Biochemistry, Academy of Sciences of the Czech Republic, Prague) for the antibacterial activity tests.
Financial support from the Grant Agency of the Czech Republic (Reg. No. 203/93/2468) is gratefully
acknowledged.
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Translated by M. Tichy.
Collect. Czech. Chem. Commun. (Vol. 59) (1994)