SESQUITERPENIC LACTONES OF SOME SPECIES OF GENUS Vernonia Schreb.

Article abstract of DOI:10.1135/cccc19940913

Four species of the genus Vernonia, endemic in Cuba, have been investigated on the presence of sesquiterpenic lactones.In addition to two derivatives of lupeol, scopoletin, genkwanin and velutin, total 15 sesquiterpenic lactones have been isolated, four of which are described for the first time.

Full text of DOI:10.1135/cccc19940913

On Terpenes
913
SESQUITERPENIC LACTONES OF SOME SPECIES
OF GENUS Vernonia SCHREB.*
a
b
a
Milos BUDESINSKY , Nestor PEREZ SOUTO and Miroslav HOLUB
a
Institute of Organic Chemistry and Biochemistry,
Academy of Sciences of the Czech Republic, 166 10 Prague 6, The Czech Republic
b
National Center of Scientific Research, Habana, Cuba
Received July 20, 1993
Accepted September 19, 1993
Four species of the genus Vernonia, endemic in Cuba, have been investigated on the presence of
sesquiterpenic lactones. In addition to two derivatives of lupeol, scopoletin, genkwanin and velutin,
total 15 sesquiterpenic lactones have been isolated, four of which are described for the first time.
The genus Vernonia SCHREB. (family Asteraceae, tribe Vernonieae) comprises about
1
1
000 species of which 45 grow in Cuba, all but one being Cuban endemites . Because
the content of sesquiterpenic lactones in these Cuban Vernonia species has not been
studied so far, we decided ten years ago to study at least several endemic Cuban
2
species , accessible to us.
As the first we studied aerial parts of species Vernonia angusticeps EKM. From the
chloroform extract we isolated lupeol acetate (I), coumarin derivative scopoletin (II)
and three sesquiterpenic lactones: 3-oxograndolide (III), 3β-hydroxygrandolide (IV)
and reynosin (V). The lactone III was isolated some time ago from the aerial part of
species Arctotis grandis THUNB. (family Asteraceae, tribe Arctotae) and its structure as
3
,4
well as absolute configuration was determined . Later on, lactone III was described as
5
a constituent of species Liabum floribundum LESS. (Asteraceae, Liabae) . Reynosin (V)
6
was obtained from species Ambrosia confertiflora DC (Asteraceae, Heliantheae) , and
probably also from species Chrysanthemum parthenium BERNH. (Asteraceae, Anthe-
7
8
mideae) and Tanacetum vulgare L. (Asteraceae, Anthemideae) . Its structure and abso-
5
– 7
lute configuration are also known
.
Further we studied aerial parts of species Vernonia acunnae ALAIN. From the light
petroleum and chloroform extracts we isolated in relatively high yield the known lupeol
palmitate (VI) and five sesquiterpenic lactones. One of them, glaucolide A (VII), is
*
Part CCCVI in the series On Terpenes; Part CCCV: Collect. Czech. Chem. Commun. 58, 909 (1993).
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

9
14
Budesinsky, Perez, Holub:
9
relatively common in species of Vernonia genus from the American continent and its
structure has been confirmed by X-ray diffraction analysis . The other lactones were
1
0
piptocarphin A (VIII), isolated previously from species Piptocarpha chontalensis PALL.
1
1
(
Asteraceae, Vernoniae), whose structure has been established , and tulipinolide (IX),
obtained more than twenty years ago from species Liliodendron tulipifera L. (family
1
2
Magnoliaceae), also of known structure . Later on, lactone IX was obtained also from
1
3
Ambrosia camphorata (GREENE) PAYNE (Asteraceae, Heliantheae) . The two further
isolated lactones were guaianolides of closely similar structure; shortly before our
study, one of them, 1αH,5αH,6βH,7αH,8α-hydroxyguai-4(15),10(14),11(13)-trien-
6
,12-olide (X) was described as the native compound of species Centaurea canariensis
WILLD. (Asteraceae, Cynareae) and its structure (but not absolute configuration) was
14
established . The second lactone, 1αH,5αH,6βH,7αH,8α-acetoxyguai-4(15),10(14),11(13)-
trien-6,12-olide (XI) was obtained from species Gochnatia smithii ROBINSON et GREEN
1
5
2
(
Asteraceae, Mutisieae) shortly after our isolation .
The aerial part of species Vernonia menthaefolia (POEPP. et SPRENG.) LESS. afforded,
beside the already known flavonoids velutin (XII) and genkwanin (XIII), three unde-
scribed sesquiterpenic lactones: 8α-(2′-methyl)acryloyloxy-13-methoxyvernojalca-
nolide − [1β,4α-dihydroxy-5β,10α-diacetoxy-8α-(2′-methyl)acryloyloxy-13-methoxycadin
-
[
7(11)-en-6,12-olide] (XIV), 8α-(2′-methyl)acryloyloxy-13-ethoxyvernojalcanolide –
1β,4α-dihydroxy-5β,10α-diacetoxy-8α-(2′-methyl)acryloyloxy-13-ethoxycadin-7(11)-
en-6,12-olide] (XV) and 1α,10α-dihydroxy-8α-(2′-methyl)acryloyloxy-13-methoxy-
hirsutinolide (XVI). The lactone XVI was then isolated as the acetate from species Ver-
1
6
nonia jalcana CUATR. .
Finally, we studied aerial parts of Vernonia moaensis ALAIN from which, in addition
to lupeol acetate (I) and lupeol palmitate (VI), we isolated the relatively widespread
9
sesquiterpenic lactone costunolide (XVII) and the long time ago described dihydrode-
1
7
hydrocostuslactone (XVIII) . Further we isolated 3β-hydroxy-4,15-dehydrograndolide
XIX) and 1α,10α-dihydroxy-8α-acetoxy-13-ethoxyhirsutinolide (XX). Last year, the
lactone XIX was described as constituent of species Venidium fastuosum STAP. (Aster-
(
1
8
aceae, Arctotae) .
RESULTS AND DISCUSSION
As already mentioned, from species Vernonia angusticeps we obtained, in addition to
other compounds, also 3β-hydroxygrandolide (IV), m.p. 162 – 165 °C, [α] +6.5°,
D
composition C H O . Its infrared spectrum proved the presence of a hydroxy group
1
5
22
4
−
1
−1
−1
(
3 610 and 3 490 cm ), a γ-lactone (1 768 cm ) and a double bond (1 643 cm ). Its
mass spectrum exhibited molecular peak 266 and characteristic fragments 248 (M − 18)
1
and 230 (248 − 18). CD spectrum had a maximum at 216 nm (∆ε +1.1). H NMR
spectrum in CDCl proved a trans-annelated C-6-lactone (H-6: 3.87 t, J(6,5) ≈ J(6,7) =
3
9
.8 Hz), two secondary hydroxyl groups in positions 3 and 9 (H-3: 3.73 dt; H-9: 4.07
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

On Terpenes
915
bdd), an exomethylene group in position 10 (H-14 and H-14′: 5.49 b and 5.15 d) and
secondary methyl groups in positions 4 (1.20 d) and 11 (H-13: 1.24 d). The confi-
guration of substituents in positions 6, 9 and 11, as well as cis-annelation at atoms C(1)
and C(5), was reliably derived from the coupling constants. The determination of confi-
guration at carbon atoms C(3) and C(4) of the five-membered ring was complicated by
overlap of signals due to H-2, H-4, H-5 and H-7. Change in the solvent (use of 1 : 1
mixture of CDCl and C H ) led to partial separation of the signals and only in situ
3
6
6
TAI-acylation, performed in this solvent mixture, resulted in such distribution of
signals from which we were able to obtain the values of all the coupling constants and
to use selective difference NOE. On saturation of signals of H-15 methyl protons, we
observed 3% NOE of H-4, 3.5% NOE of H-3 and 2% NOE of H-5α. From this it
follows that the methyl group (H-15) is cis-oriented relatively to the protons in posi-
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

9
16
Budesinsky, Perez, Holub:
tions 3 and 5 and, consequently, the configuration of the substituents on the five-
membered ring is 3β-OH and 4α-CH . The absolute configuration at C(11) in 3β-
3
hydroxygrandolide (IV) is (S) as derived from the positive CD maximum at 216 nm
1
9,20
using sector rule
. Thus, formula IV depicts also the absolute configuration of this
lactone. The lactone IV was prepared by reduction of 3-oxograndolide (III) with sodium
borohydride.
1
A detailed analysis of H NMR spectra of the lactone IV from V. angusticeps and the
lactone from Arctotis grandis, originally supposed to be identical with lactone IV
4
1
(
ref. ), showed that the compounds are different. Our new H NMR data (Table I) show
values almost identical with those found for lactone IV, except for the protons of the
five-membered ring. As in the case of lactone IV, the degeneration of signals of protons
in position 2 (at δ 2.06) in CDCl3 was not suppressed by use of a CDCl3–C6H6
mixture (1 : 1) (both H-2 and H-5 are again at δ ≈ 1.85) and good resolution was again
obtained only upon TAI-acylation in the said solvent mixture. In a selective difference
NOE experiment, saturation of the methyl signal (H-15) resulted in 4.5% NOE for the
H-4 and 4% NOE for the H-6β protons whereas no NOE was observed for the proton
H-3. Accordingly, in this lactone the substituents on the five-membered ring have con-
figuration 3β-OH and 4β-CH3 and the compound is 3β-hydroxy-4-epigrandolide, de-
scribed by formula XXI. The lactone is obviously identical with the lactone described in
2
1
5
ref. , originally characterized by formula IV which was later revised in favour of the
structure XXI.
2
From species Vernonia acunnae we as the first isolated and described the sesquiter-
penic lactone XI, m.p. 112 – 114 °C, [α]D +78.8°, composition C17H20O4. Its IR spec-
−
1
trum showed the presence of a γ-lactone (1 763 cm ), an acetate (1 739 and 1 245
−
1
−1
cm ) and a double bond (1 643 and 1 657 cm ). In the mass spectrum there was
+
molecular peak M 288 and characteristic fragments 246 (M − CH2=CO) and 228 (M − 60).
CD maximum was located at 220 nm (∆ε −3.8). H NMR spectrum (Table II) proved
1
the presence of an acetate in position 8α (OAc: 2.15 s; H-8: 4.98 dt, J(8,7) = 10.2,
J(8,9) = 5.1 and 5.4 Hz), an exomethylene γ-lactone, trans-annelated in positions 6 and
7
=
(H-13: 6.25 d, J(13,7) = 3.5 Hz; H-13′: 5.66 d, J(13′,7) = 3.0 Hz; H-6: 4.02 dd, J(6,5)
10.3, J(6,7) = 8.9 Hz), and two other exomethylene groups (signals at δ 4.94, 5.05,
5
.10 and 5.30). Detailed analysis of our NMR data (which are in good accord with the
1
5
published incomplete 80 MHz data) led to the structure XI.
The structure of the further isolated lactone, X, was suggested on the basis of com-
1
parison of its H NMR spectrum with that of compound XI. The absence of acetate
group, accompanied by an upfield shift of the H-8 signal (δ 3.93), retention of signals
of all other protons in the molecule and proof of a hydroxy group by TAI-acylation,
have shown that compound X is the deacetyl derivative of lactone XI. This was con-
firmed by hydrolysis of compound XI which afforded lactone X. The physical constants
1
14
as well as H NMR data for X (Table II) agree well with the published ones . The
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

On Terpenes
917
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

9
18
Budesinsky, Perez, Holub:
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

On Terpenes
919
TABLE II
1
H NMR parameters of guaianolide derivatives X, XI, and XIX. The values of coupling constants are
given in parentheses; TAI-induced acylation shifts are given in square brackets
Proton
H-1
X
XI
XIX
3.00 q
8.3 (3 ×))
[0.02]
2.99 q
2.88 m
2.43 dt
(
(8.7; 8.0 (2 ×))
H-2
H-2′
H-3
1.75 – 1.90 m
1.75 – 1.90 m
2.49 m
1.75 – 1.90 m
(
14.2; 8.4 (2 ×))
1.82 ddd
14.2; 5.9; 4.6)
4.60 ddt
1.75 – 1.90 m
(
[0.02]
2.46 m
[1.10]
(
8.4; 6.0; 2.3; 2.0)
H-5
H-6
H-7
2.80 bdd
[0.04]
[0.08]
[0.39]
2.82 bdd
(10.3; 8.7)
2.80 m
(
10.4; 8.7)
3.97 dd
10.4; 9.0)
2.84 tt
4.02 dd
(10.3; 8.9)
3.97 t
(9.8 (2 ×))
[0.04]
(
3.14 tt
1.92 ddt
(
9.0 (2 ×); 3.5; 3.2)
(10.0; 8.9; 3.5; 3.0)
(12.3; 11.9; 9.7; 3.0)
2.44 ddd
H-8
3.93 dt
[1.16]
4.98 dt
(
9.1; 5.3; 4.8)
(10.2; 5.4; 5.1)
(12.4; 4.8; 3.1)
H-8′
–
–
1.33 dt
(
12.3 (2 ×); 10.6)
H-9
2.70 dd
13.8; 5.3)
2.28 dd
[0.12]
[0.20]
2.69 dd
(14.2; 5.4)
4.14 bdd
(10.8; 4.8)
[1.03]
(
H-9′
2.31 ddd
–
(
13.8; 4.8)
(14.2; 5.1; 0.7)
H-11
H-13
H-13′
H-14
H-14′
H-15
–
–
2.25 dq
(
11.9; 7.0 (3 ×))
6.27 dd
3.5; 0.9)
6.16 dd
3.2; 0.9)
[0.03]
[−0.41]
[0.06]
[0.03]
[0.01]
6.25 d
(3.5)
1.26 d
(7.0)
[0.02]
(
5.66 d
(3.0)
–
(
5.05 b
4.96 b
5.29 m
5.05 b
5.44 t
[0.00]
[0.01]
[0.17]
(
1.3 (2 ×))
4.94 d
0.07)
5.21 b
(
5.30 m
5.35 t
(2.3; 2.0)
5.31 t
(2.2; 2.0)
–
(
2.5; 1.5 (2 ×); 1.0)
(2.6 (2 ×); 2.0; 1.9)
5.10 m
H-15′
5.09 m
[0.02]
[0.16]
(
2.8; 2.0 (2 ×); 1.0)
(2.1 (2 ×); 2.0; 0.9)
2.15 s
OAc
–
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

9
20
Budesinsky, Perez, Holub:
absolute configuration of lactones X and XI was found to be 8(S), as derived from the
sense of the difference in molecular rotations of the acetate XI and alcohol X on appli-
2
2
cation of the Brewster rule .
In the species V. menthaefolia we found three lactones, XIV – XVI. The first, lactone
XIV, melted at 188 – 192 °C, [α]D 0°, composition C24H32O11. Its IR spectrum showed
−
1
−1
the presence of a hydroxyl (3 595 and 3 460 cm ), an acetate (1 740 and 1 235 cm ),
−
1
−1
a γ-lactone (1 760 cm ), an unsaturated ester (1 710 and 1 637 cm ) and a methoxy
group (2 820 cm ). The mass spectrum exhibited molecular peak M 496 and charac-
−
1
teristic fragments 481 (M − CH3), 464 (M − CH3OH), 446 (464 − 18), 404 (464 − 60),
3
78 (464 − C3H5COOH), 350 (M − C3H5COOH − 60), 318 (378 − 60), 276 (318 −
CH2=CO), 258 (318 − 60) and 69 (C3H5CO). CD spectrum had a maximum at 205 nm
1
(
∆ε −7.4) and 240 nm (∆ε +9.2). The H NMR spectrum (Table III) proved two methyl
groups at tertiary carbon atoms of the type C(OR)CH3 (δ 1.39 and 1.70 s), two acetate
groups (δ 1.95 s and 2.16 s), a methoxy group (δ 3.36 s) and a methacrylate moiety
(
=CH2: 5.98 p and 5.62 p, CH3: 1.91 dd). Further we identified an isolated −CH2O−
group (δ 4.53 d and 4.26 d, J = 12.2 Hz), two protons of the type CH−OCOR of which
one is isolated (δ 5.86 s) and the second is adjacent to a CH2 group (δ 5.77 dd, J = 4.3
and 2.3 Hz) and, finally, an isolated −CH2−CH2− fragment. Comparison of the elemen-
tal formula and the proton NMR data indicated the presence of two OH groups of
1
3
which only one was confirmed by in situ TAI-acylation (Table III). The C NMR
spectrum (Table IV) confirmed the above-mentioned structural fragments and, in addi-
tion, proved one tetrasubstituted double bond (δ 157.67 and 129.42). Detailed analysis
of the NMR spectral data led us to suggestion of structure XIV whose acetate was later
1
6
described and its structure solved . The nonreactivity of the hydroxy group in position
1
6
1
, which we observed in the TAI-acylation, was reported by the German authors for
classical acetylation and was explained by steric hindrance.
Another hitherto undescribed lactone of this kind, isolated in the present study, was
lactone XV, m.p. 180 – 183 °C, [α]D +30.3°, composition C25H34O11. Its IR spectrum
−
1
−1
showed the presence of a hydroxyl (3 585 and 3 450 cm ), a γ-lactone (1 758 cm ),
−
1
−1
−1
an acetate (1 738 cm and 1 235 cm ) and a conjugated ester (1 710 sh and 1 634 cm ).
In addition to the molecular peak (510), the mass spectrum exhibited characteristic
fragments 481 (M − C2H5), 464 (M − C2H5OH), 450 (M − 60), 446 (464 − 18), 432
(
450 − 18), 404 (464 − 60), 378 (464 − C3H5COOH), 318 (378 − 60), 276 (318 −
CH2=CO), 258 (318 − 60), 69 (C3H5CO), 43 (CH3CO). CD spectrum contained
1
maxima at 210 nm (∆ε −4.5) and 240 nm (∆ε +10.0). Comparison of the H NMR
spectra showed that the lactone XV differs from lactone XIV only in that it contains an
ethoxy instead of a methoxy group in position 13 (CH3: 1.17 t; CH2O: 3.51 q, J = 7.0 Hz).
As follows from comparison of NMR spectra, both the mentioned lactones XIV and XV
were prepared last year synthetically from glaucolide A (VII) but no characteristic chi-
2
3
roptical data were reported for them .
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

On Terpenes
921
The last of the three mentioned lactones isolated from V. menthaefolia species was
noncrystalline lactone XVI, [α]D +124.0°, composition C20H26O8. According to IR
−
1
−1
spectrum, it contains a hydroxyl (3 550 cm ), a methoxyl (2 820 cm ), a γ-lactone
(
−1
−1
1 758 cm ), a conjugated ester (1 721 and 1 637 cm ) and a double bond (1 608 and
TABLE III
1
H NMR parameters of compounds XIV – XVI and XX. The coupling constants are given in parenthe-
ses; TAI-induced acylation shifts for 4-OTAC-derivatives XIV and XV and 4,10-diOTAC derivative
XVI are given in square brackets
Proton
H-2
XIV
XV
XVI
XX
2.37 ddd [0.05]
2.38 ddd [0.05]
(14.5; 4.5; 3.5)
1.68 ddd [0.05]
(14.5; 12.5; 5.0)
2.32 ddd [0.27]
(14.5; 12.5; 4.5)
1.87 ddd [0.75]
(14.5; 5.0; 3.5)
2.44 dt
2.42 dt
(
14.5; 4.5; 3.5)
1.70 ddd [0.05]
14.5; 12.5; 5.0)
2.34 ddd [0.27]
14.5; 12.5; 4.5)
1.86 ddd [0.75]
14.5; 5.0; 3.5)
5.86 s [0.31]
(12.4; 12.4; 7.1)
(12.4; 12.4; 7.1)
a
a
H-2′
H-3
(
a
a
a
a
(
H-3′
(
H-5
H-8
5.86 s
[0.30]
5.85 bs [0.17]
5.87 bs
5.77 dd [−0.04] 5.83 dd [−0.05] 6.57 bd
4.3; 2.3) (4.3; 2.2) (10.5; <2)
3.46 dd [−0.01] 3.45 dd [−0.01] 2.59 dd
6.42 bd
(10.5; <2)
2.53 dd
(
H-9
(
16.0; 2.3)
2.10 dd [0.03]
16.0; 4.3)
4.53 d
12.2)
4.26 d
12.2)
(16.0; 2.2)
(16.2; 10.5)
2.11 bd
(16.0; 9.6)
a
H-9′
2.09 dd [0.01]
(16.0; 4.3)
(
(16.2; <2)
H-13
[0.02]
[0.00]
4.55 d
(12.4)
[0.03]
4.58 bd [−0.31] 4.52 d
(12.1)
(
(12.2)
H-13′
4.31 d
(12.4)
[−0.01] 4.28 d
[-0.10] 4.31 d
(12.2)
(
(12.1)
H-14
H-15
OAc
1.70 s
1.39 s
1.95 s
[0.02]
[0.46]
1.71 s
[0.01]
1.58 s
1.23 s
–
[0.00]
[0.42]
1.58 s
1.22 s
2.11 s
1.40 bs [0.45]
[−0.03] 1.95 s
[−0.03] 2.17 s
[−0.03]
[−0.00]
2
.16 s
OMe
OEt
3.36 s
[0.08]
–
3.41 s
[−0.06]
–
–
–
3.51 q
1.17 t
[−0.01]
[0.00]
–
–
3.56 q
1.22 t
OCOC(CH3)=CH2 5.98 p
[0.01]
[−0.01] 5.61 p
5.98 p
[0.01]
[0.00]
6.29 p
5.68 p
[−0.04]
[0.07]
–
–
5
.62 p
1
.91 dd [0.02]
1.91 dd [0.02]
1.96 dd [0.01]
–
a
Proton signal was not assigned.
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

9
22
Budesinsky, Perez, Holub:
−
1
1
655 cm ). Mass spectrum exhibited molecular peak M 394 and characteristic frag-
ments 362 (M − CH3OH), 344 (362 − 18), 320 (362 − CH2=CO), 308 (M −
C3H5COOH), 276 (308 − CH3OH), 234 (276 − CH2=CO), 216 (234 − 18) and 69
(
(
C3H5CO). In the CD spectrum there were three maxima: at 210 nm (∆ε −9.0), 255 nm
∆ε +10.0) and at 318 nm (∆ε −0.6). H NMR spectrum (Table III) showed the
1
presence of two tertiary methyl groups (singlets at δ 1.23 and 1.58), a methacrylate
moiety (=CH2: 6.29 p and 5.68 p; CH3: 1.96 dd), a methoxy group (δ 3.41) and two
hydroxy groups (broadened signals at δ 4.10 and 3.84, disappearing on addition of
D2O). In the lowfield region of the spectrum we further assigned signals to a CH−O
proton in position 8 (broad doublet at δ 6.57 belonging to an isolated ABX system with
CH2 protons in position 9 at δ 2.59 dd and 2.11 bd), to an isolated olefinic proton in
position 5 (δ 5.85 bs) and protons of isolated CH2−O group in position 13 (δ 4.58 bd
and 4.28 d, J = 12.1 Hz). Our proton NMR data and the structure XVI derived from
1
6
them are in accord with the data described later .
In addition to compounds I, V, XVII and XVIII, obtained already earlier from other
plant species, we isolated from species V. moaensis a hitherto undescribed noncrystal-
line lactone XIX, [α]D +39.9°, composition C15H20O4. Its IR spectrum indicated the
−
1
−1
presence of a hydroxyl (3 605 and 3 470 cm ), a γ-lactone (1 770 cm ) and a double
−
1
bond (1 645 cm ). Mass spectrum contained molecular peak M 264 and characteristic
TABLE IV
Carbon-13 chemical shifts of compounds XIV and XV
Carbon
XIV
XV
Carbon
XIV
XV
1
2
3
4
5
6
7
8
9
89.20
29.35
35.29
72.71
75.73
~77.00
157.67
65.95
33.87
84.18
129.42
160.07
62.66
88.84
30.78
35.89
73.20
76.43
~77.00
157.14
66.17
34.20
84.25
130.53
169.12
61.44
14
19.17
22.89
58.04
–
19.66
23.44
–
15
OMe
OEt
66.36
15.11
171.67
171.26
23.37
20.39
167.64
136.33
125.81
18.20
–
a
a
OAc
171.59
171.05
22.77
19.90
167.47
135.89
125.39
17.68
1
1
1
1
0
1
2
3
OCOC(CH3)=CH2
a
The signal is overlapped with a strong signal of CDCl3.
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

On Terpenes
923
fragments 246 (M − 18), 231 (M − 18 − CH3), 218 (246 − CO) and 200 (218 − 18). CD
1
maximum was located at 220 nm (∆ε +0.7). H NMR spectrum (Table II) proved the
presence of a secondary methyl group (δ 1.26 d, J = 7.0 Hz), two exomethylene groups
in position 14 and 15 (δ 5.44 t, 5.21 bs, 5.35 t and 5.31 t) and CH−O protons in posi-
tions 3, 6 and 9 (δ 4.60 ddt, 3.97 t and 4.14 bdd). The presence of hydroxyl groups in
positions 3 and 9 was proved by in situ TAI-acylation (induced TAI-acylation shifts
1
(
.10 and 1.03 ppm, respectively, see Table II). Detailed analysis of the NMR data
particularly coupling constants) led us to the structure XIX. Last year, lactone of the
structure XIX was found in the aerial parts of species Venidium fastuosum STAP. (Aster-
1
8
aceae, Arctotae) and its physical constants agree with our data.
So far undescribed was also the noncrystalline lactone XX, [α]D +48.1°, composition
−
1
C19H26O8. According to IR spectrum, it contained a hydroxy group (3 535 cm ), an
−
1
−1
ethoxy group (2 860 cm ), a γ-lactone (1 755 cm ) and a double bond (1 653, 1 636
−
1
and 1 604 cm ). Mass spectrum exhibited molecular peak M 382 and characteristic
fragments 336 (M − C2H5OH), 322 (M − 60), 294 (336 − CH2=CO), 276 (336 − 60),
2
3
34 (276 − 42) and 216 (234 − 18). CD maxima were located at 250 nm (∆ε +2.2) and
10 nm (∆ε −0.7). Its H NMR spectrum showed marked structural similarity with
1
lactone XVI, except for substituents in positions 8 and 13 which in lactone XX are
acetate (δ 2.11 s) and ethoxy group (δ 1.22 t and 3.56 q, J = 7.0 Hz), respectively,
instead of methacrylate and methoxy groups in the lactone XVI.
In the present study we describe the isolation and structure determination of a series
of sesquiterpenic lactones from four species of the Vernonia genus that are endemic in
Cuba. The basic skeletons of these lactones (eudesmanolide, guaianolide (including the
grandolide type), germacranolide (with hirsutinolide and glaucolide type specification)
and cadinanolide (with vernojalcanolide type specification)) do not differ from those of
sesquiterpenic lactones obtained from Vernonia species native in the New World (see
9
,16
e.g. refs ). From the viewpoint of chemosystematics of genus Vernonia, the Cuban
endemites can be included among other species of the mentioned genus that are native
particularly in Central and South America.
The sesquiterpenic lactones of the hirsutinolide and cadinanolide type, which had
been described already by several authors as constituents of some species of the genus
Vernonia and which were isolated also by us from several Cuban Vernonia, are re-
2
3
garded as artifacts; this could have some implications in chemosystematics, biogen-
2
3
esis, etc. This opinion is based on the fact that these hirsutinolides and cadinanolides
were prepared from glaucolide A (VII) by treatment with methanol or ethanol in the
presence of silica gel or alumina. However, we think that the cited results cannot serve
as unequivocal arguments for regarding hirsutinolides and cadinanolides as artifacts. In
a living plant organism, native compounds of the glaucolide A type (VII) may undergo
many enzymatic reactions leading to products identical with those obtained by other
mechanisms, e.g. by a chemical way. Moreover, in the processing of the aerial part of
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

9
24
Budesinsky, Perez, Holub:
species V. menthaefolia we did not use ethanol at all and methanol was employed only
in the last stage of the chromatography when both hirsutinolide XVI and cadinanolides
XIV and XV had been already eluted with less polar solvents. Similarly, although the
mentioned solvents were not used at all in the work-up of the aerial parts of V.
moaensis, we isolated hirsutinolide XX. We therefore assume that there is no proof of
the artifact character of hirsutinolides and cadinanolides found in species of Vernonia
genus.
EXPERIMENTAL
Melting points were determined on a Kofler block and are uncorrected. IR spectra were recorded on
a Perkin–Elmer PE 580 spectrometer in chloroform solution unless stated otherwise; wavenumbers
−1
are given in cm . Optical rotations were measured in methanol, unless stated otherwise, on objective
polarimeter Perkin–Elmer 141. Mass spectra were measured on a ZAB-EQ V.G. Analytical spectro-
meter (Manchester, U.K.); electron impact, 70 eV. CD spectra (nm, ∆ε, methanol) were measured on
1
an autodichrograph Jobin–Yvonne Mark V. H NMR spectra were taken in deuteriochloroform (with
tetramethylsilane as internal reference) on a Varian XL-200 (at 200 MHz) and/or Varian UNITY-500
(
at 500 MHz) FT NMR spectrometer. 2D-COSY spectra were used for the assignment of coupled
protons. Interproton NOE’s were determined from difference 1D-NOE spectra: first spectrum was
run with selective irradiation of given proton during time-period (6 s) before the acqusition time and
then reference spectrum (taken under the same conditions but with off-resonance decoupling
frequency setting) was acquired and substracted from the first one to give difference NOE spectrum.
2
4
In situ TAI-acylation was done by the addition of small excess of TAI to the CDCl solution of
3
1
13
compound in NMR sample tube and product was characterized by H NMR spectrum. C NMR
spectra were run in the same solvent on the Varian UNITY-500 (at 125.7 MHz) spectrometer, using
“
attached proton test” pulse sequence for the classification of carbons by the number of directly
bound protons.
Isolation of Constituents
The known compounds – lupeol acetate (I), scopoletin (II), lupeol palmitate (VI), velutin (XII) and
1
genkwanin (XIII) – were identified on the basis of their spectral properties (IR, MS, UV, H NMR),
melting points and specific rotation.
a) From Vernonia angusticeps. Aerial parts of species Vernonia angusticeps EKM., collected in
April 1980 at San Piedra, Santiago de Cuba (voucher HAJB 41577 is deposited in Herbarium of the
National Botanical Garden in Habana), were dried and finely ground (900 g). As shown by IR
spectrum, light petroleum extract of this material contained no compounds with a γ-lactone ring.
Further extraction of the mentioned material with chloroform and evaporation of the solvent afforded
a residue (15 g) which was chromatographed on a column of silica gel (400 g). Elution with
toluene–diethyl ether (9 : 1) gave lupeol acetate (I), m.p. 208 – 210 °C (acetone) and [α] +45.7°
D
1
(
c 0.35, CHCl ). H NMR spectrum (CDCl ): 0.78, 0.84, 0.85, 0.93, 1.03 s (5 × CH ); 1.6 dd (CH −C=,
3
3
3
3
J = 1.3 and 0.7 Hz); 2.04 s (OAc); 2.38 dt (H-19, J = 11, 11.5 and 5.0 Hz); 4.47 dd (H-3, J = 11.0
and 5.0 Hz); 4.57 m (H-29); 4.69 m (H-29′). Mass spectrum (m/z): 468 (M), 408 (M − 60). IR
−
1
spectrum (cm ): 1 722, 1 254 (acetate); 1 639 (double bond). Elution with toluene–diethyl ether
(
(
4 : 1), followed by preparative thin-layer chromatography, afforded scopoletin (II), m.p. 195 – 197 °C
methanol). UV spectrum (nm): 227, 296, 394. Mass spectrum (m/z): 192 (M). Elution with toluene–
diethyl ether (6 : 4) gave 3-oxograndolide (III), m.p. 139 – 143 °C (ethyl acetate) and [α ]D +93°
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

On Terpenes
925
(
c 0.35). Its IR, 1H NMR, mass and CD spectra were identical with those of the described
3
– 5
compound
and no mixture melting point depression was observed. Further elution with ethyl
acetate–diethyl ether (1 : 1) furnished 3β-hydroxygrandolide (IV), m.p. 162 – 165 °C, [α] +6.5° (c 0.42),
D
−1
composition C15H22O . IR spectrum (cm ): 1 768 (γ-lactone); 3 610 and 3 490 (hydroxyl); 1 643
4
(
+
double bond). Mass spectrum (m/z): 266 (M), 248 (M − 18), 230 (M − 18 − 18). CD spectrum: 216,
1.1. For H NMR spectrum see Table I. For C15H22O4 (266.3) calculated: 67.64% C, 8.33% H;
1
found: 67.58% C, 8.47% H. Ethyl acetate eluted reynosin (V), m.p. 140 – 143 °C, [α] +135.5° (c 0.28).
D
6
– 8
1
Its identity with a standard
mixture melting point.
was proved by comparison of H NMR, IR, CD, and mass spectra and
b) From Vernonia acunnae. Aerial parts of species V. acunnae ALAIN., collected in April 1980 in
the region of river Yagrumaje, Moa, Oriente (voucher HAC 29170 is deposited in Herbarium of the
Cuban Academy of Sciences, Habana), were dried and finely ground (580 g). On extraction with
light petroleum and the usual work-up, this material afforded a sirupy residue (21 g) which was chro-
matographed on a column of silica gel (500 g). Elution with light petroleum gave lupeol palmitate
1
(
VI), m.p. 74 – 77 °C, [α] +28.9° (c 0.35, CHCl ). H NMR spectrum (CDCl ): signals of the lupeol
D
3
3
part identical with lupeol acetate (vide supra); 0.88 t (CH , J = 6.5 Hz); 1.25 bs ((CH ) ), 2.29 t
3
2 n
(
COCH ). Mass spectrum (m/z): 664 (M), 409 (M − C15H31COO). Elution with light petroleum–
2
toluene (1 : 1) afforded lupeol acetate (I), identical in all respects with compound obtained from V.
angusticeps. Toluene–ethyl acetate (4 : 1) eluted glaucolide A (VII), m.p. 152 – 155 °C, [α] −13.0°
D
1
10
(
c 0.36). Its H NMR, IR and mass spectra corresponded to the literature data . Further elution with
toluene–ethyl acetate (4 : 1), followed by preparative thin-layer chromatography, afforded
1
noncrystalline piptocarphin A (VIII), [α] +71.0° (c 0.6, CHCl3). H NMR, IR and mass spectrum
D
1
1
were identical with the published data . After extraction with light petroleum, the plant material was
extracted with chloroform. The sirupy residue (10 g), obtained on evaporation of the solvent, was
column chromatographed on silica gel (250 g). Elution with toluene–chloroform (1 : 1) afforded
1
αH,5αH,6βH,7αH,8α-acetoxyguai-4(15),10(14),11(13)-trien-6,12-olide (XI), m.p. 112 – 114 °C
(
(
(
ethyl acetate–light petroleum), [α]D +78.8° (c 0.34). IR spectrum: 1 763 (γ-lactone); 1 739, 1 245
acetate); 1 643, 1 657 (double bond). Mass spectrum (m/z): 288 (M), 246 (M − CH =CO), 228
2
M − 60), 148, 91, 43. CD spectrum: 220, −3.8. For C H O (288.3) calculated: 70.83% C, 6.94% H;
1
7
20
4
1
found: 70.69% C, 6.85% H. For H NMR spectrum see Table II. Elution with chloroform gave tuli-
pinolide (IX), m.p. 178 – 182 °C, [α]D +231.0° (c 0.51, CHCl ). Its H NMR, IR and mass spectra
1
3
1
2,13
were in accord with the published ones
αH,5αH,6βH,7αH,8α-hydroxyguai-4(15),10(14),11(13)-trien-6,12-olide, (X), m.p. 92 – 95 °C, [α]
. Chloroform–methanol (99 : 1) washed out
1
+
D
1
57.2 (c 0.45, acetone). Its H NMR (Table II), IR and mass spectrum corresponded to the literature
1
5
values
.
c) From Vernonia menthaefolia. The aerial parts of species V. menthaefolia (PAPP. ex SPRENG.)
LESS., collected in April 1980 at Gran Piedra, Santiago de Cuba (voucher HAJB 41576 is deposited
at Herbarium of the National Botanical Garden, Habana), were dried and finely ground (800 g).
Extraction with light petroleum and the usual processing afforded a sirupy residue (18 g) which was
chromatographed on a column of silica gel (500 g). Elution with toluene–ethyl acetate (4 : 1) gave
crystalline velutin (XII), m.p. 228 – 233 °C (ethyl acetate–toluene). UV spectrum (nm): 235, 255,
1
3
40. Mass spectrum (m/z): 314 (M), 167 (C H O ), 148 (C H O ). H NMR spectrum (CDCl ): 3.89 s
8
7
4
9
8
2
3
and 4.01 s (2 × OCH ); 6.38 d (H-6, J(6,8) = 2.3 Hz); 6.49 d (H-8, J(8,6) = 2.3 Hz); 6.57 s (H-3);
3
7
.04 d (H-5′, J(5′,6′) = 8.4 Hz); 7.34 d (H-2′, J(2′,6′) = 2.1 Hz); 7.49 dd (H-6′, J(6′,5′) = 8.4 and
J(6′,2′) = 2.1 Hz). Further elution with the same solvent mixture gave genkwanin (XIII), m.p. 286 – 289 °C.
1
H NMR spectrum (CD SOCD ): 3.87 s (OCH ); 6.39 d (H-6, J(6,8) = 2.3 Hz); 6.77 d (H-8, J(8,6)
3
3
3
=
2.3 Hz); 6.85 s (H-3); 6.94 m (H-3′ and H-5′); 7.96 m (H-2′ and H-6′). Elution with toluene–ethyl
acetate (3 : 2) followed by preparative thin-layer chromatography, furnished noncrystalline 1α,10α-
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

9
26
Budesinsky, Perez, Holub:
dihydroxy-8α-(2′-methyl)acryloyloxy-13-methoxyhirsutinolide (XVI), [α]D +124.0° (c 0.38), compo-
sition C H O . IR spectrum: 3 550 (hydroxyl); 2 820 (methoxyl); 1 758 (γ-lactone); 1 721 (α,β-
2
0
26
8
unsaturated ester); 1 655, 1 637, 1 608 (double bond). Mass spectrum (m/z): 394 (M), 362 (M −
CH OH), 344 (362 − 18), 320 (362 − CH =CO), 308 (M − C H COOH), 276 (308 − CH OH), 234
3
2
3
5
3
(
−
276 − CH =CO), 216 (234 − 18), 148, 99, 69 (C H CO). CD spectrum: 210, −9.0; 255, +10.0; 318,
2 3 5
0.6. For H NMR spectrum see Table III. For C H O (394.4) calculated: 60.90% C, 6.65% H;
20 26 8
1
found: 61.25% C, 6.84% H. Toluene–ethyl acetate mixture (2 : 3) washed out material (3.1 g) which
was rechromatographed on silica gel (300 g). The first ethyl acetate fractions gave 8α-(2′-
methyl)acryloyloxy-13-ethoxyvernojalcanolide (XV), m.p. 180 – 183 °C (acetone–ethyl acetate), [α]D
+
(
30.3° (c 0.6, acetone), composition C25H34O11. IR spectrum: 3 585, 3 450 (hydroxyl); 1 758
γ-lactone); 1 738, 1 235 (acetate); 1 710 sh (α,β-unsaturated ester); 1 634 (double bond). Mass
spectrum (m/z): 510 (M), 481 (M − C H ), 464 (M − C H OH), 450 (M − 60), 446 (464 − 18), 432
2
5
2
5
(
9
450 − 18), 404 (464 − 60), 378 (464 − C H COOH), 318 (378 − 60), 276 (318 − CH CO), 258 (318 − 60),
9, 69 (C H CO), 43 (CH CO). CD spectrum: 210, −4.5; 240, +10.0. For H and C NMR spectral
3 5 3
3
5
2
1
13
data see Tables III and IV. For C25H34O11 (510.5) calculated: 58.81% C, 6.71% H; found: 58.69% C,
.92% H. The last ethyl acetate fractions afforded 8α-(2′-methyl)acryloyloxy-13-methoxyverno-
6
jalcanolide (XIV), m.p. 188 – 192 °C (ethyl acetate), [α]D 0° (c 0.29), composition C24H32O11. IR
spectrum: 3 595, 3 460 (hydroxyl); 2 820 (methoxyl); 1 760 (γ-lactone); 1 740, 1 235 (acetate); 1 710
(
(
(
(
α,β-unsaturated ester); 1 637 (double bond). Mass spectrum (m/z): 496 (M), 481 (M − CH ), 464
3
M − CH OH), 446 (464 − 18), 418 (M − 18 − 60), 404 (464 − 60), 378 (464 − C H COOH), 350
3
3
5
M − C H COOH − 60), 318 (378 − 60), 276 (318 − 42), 258 (318 − 60), 99, 69 (C H CO), 43
3
5
3
5
1
13
CH CO). CD spectrum: 205, −7.4; 240, +9.2. For H and C NMR spectra see Tables III and IV.
3
For C24H32O11 (496.5) calculated: 58.05% C, 6.50% H; found: 57.87% C, 6.64% H.
d) From Vernonia moaensis. Aerial parts of species V. moaensis ALAIN., collected in April 1980 in
the region of river Yagrumaje, Moa, Oriente (voucher HAC 29169 is deposited at Herbarium of the
Cuban Academy of Sciences, Habana), were dried and finely ground (750 g). The usual processing
of the light petroleum extract afforded a sirupy residue (16 g) which was column chromatographed
on silica gel (400 g). Light petroleum–benzene (1 : 1) eluted lupeol palmitate (VI) and lupeol acetate
(
I). Both compounds I and VI were identical with the analogous compounds obtained from V. angua-
ticeps and V. acunnae. Elution with benzene–chloroform (1 : 1) afforded costunolide (XVII), m.p.
1
1
02 – 106 °C, [α]D +115.2° (c 0.5, chloroform). Its IR, H NMR, CD and mass spectra corresponded
2
5
to the published data . Subsequent extraction of the plant material with chloroform, followed by
usual work-up, gave a sirupy residue (12 g) which was chromatographed on a column of silica gel
(
300 g). Elution with benzene–chloroform (4 : 1) and repeated preparative thin-layer chromatography
furnished noncrystalline dihydrodehydrocostuslactone (XVIII), [α] +7.3° (c 0.4, chloroform). Its
D
1
17
H NMR, IR and mass spectra were in accord with the published data . Elution with benzene–chlo-
roform (1 : 1) and repeated column and preparative thin-layer chromatography afforded noncrystalline
α,10α-dihydroxy-8α-acetoxy-13-ethoxyhirsutinolide (XX) (75 mg), [α]D +48.1° (c 0.5). IR
1
spectrum: 3 535 (hydroxyl); 2 860 (ethoxyl); 1 755 (γ-lactone); 1 653, 1 636, 1 604 (double bond).
Mass spectrum (m/z): 382 (M), 336 (M − C H OH), 322 (M − 60), 294 (336 − 42), 276 (336 − 60),
2
5
1
2
34 (276 − 42), 216 (234 − 18), 188, 148, 99. CD spectrum: 250, +2.2; 310, −0.7. For H NMR
spectrum see Table III. For C19H26O8 (382.4) calculated: 59.67% C, 6.85% H; found: 59.79% C,
.98% H. Elution with chloroform with 1% of methanol gave noncrystalline 3β-hydroxy-4,15-
dehydrograndolide (XIX) (55 mg), [α]D +39.9° (c 0.34). IR spectrum: 3 605, 3 470 (hydroxyl); 1 770
γ-lactone); 1 645 (double bond). Mass spectrum (m/z): 264 (M), 246 (M − 18), 231, 218, 200, 173,
6
(
7
6
1
7. CD spectrum: 220, +0.7. For H NMR spectrum see Table II. For C H O (264.3) calculated:
15 20 4
8.16% C, 7.87% H; found: 68.07% C, 7.87% H.
Collect. Czech. Chem. Commun. (Vol. 59) (1994)

On Terpenes
927
Preparation of 3β-Hydroxygrandolide (IV) from 3-Oxograndolide (III)
A suspension of NaBH (50 mg) in methanol (4 ml) was added to a solution of 3-oxograndolide (50 mg)
4
in methanol (4 ml). After stirring at room temperature for 1 h, water (6 ml) was added and the
mixture was acidified with 5% sulfuric acid. The product was taken up in chloroform, the extract was
worked up as usual and the residue was purified by chromatography to afford 3β-hydroxygrandolide
(
IV, 20 mg), identical in all respects (including the mixture melting point) with a standard.
Preparation of Compound X from Lactone XI
A solution of Na CO (200 mg) in water (10 ml) was added to a solution of lactone XI (60 mg) in
2
3
methanol (10 ml). After standing at room temperature for 1 h, the mixture was acidified with 5%
sulfuric acid and the product was extracted with chloroform. The chloroform extract was worked up
in the usual manner and the residue (37 mg) was chromatographed on a thin layer of silica gel in
chloroform–methanol (9 : 1) to give lactone X, identical in all respects with a standard. No mixed
melting point depression was observed.
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1
9
1
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1
1
1
1
1
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1
7. Mathur S. B., Hiremath S. V., Kulkarni G. H., Kelkar G. R., Bhattacharyya S. C., Simonovic D.,
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1
1
2
2
2
8. Ali A. A., El-Emary N. A., Khalifa A. A., Frahm A. W.: Phytochemistry 31, 2781 (1992).
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Budesinsky, Perez, Holub:
2
3. Martinez-Vazquez M., Sepulveda S., Belmont M. A., Rubio M., Joseph-Nathan P.: J. Nat. Prod.
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5
2
2
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Translated by M. Tichy.
Collect. Czech. Chem. Commun. (Vol. 59) (1994)