Synthesis and analgesic activity of new heterocyclic compounds derived from monoterpenoids

Article abstract of DOI:10.1007/s00044-012-0310-9

A set of new heterocyclic compounds with different types of framework, including a new type of framework, were synthesized by reactions of verbenol epoxide and (1R,2R,6S)-3-methyl-6-(prop-1-en-2-yl)cyclohex-3-ene-1,2-diol with aromatic aldehydes containing three methoxy groups. The analgesic activity of these substances was studied. Three compounds possessed considerable activity in vivo in the acetic acid-induced writhing test. (2S,4R,4aR,8S,8aR)-4,7-Dimethyl- 2-(2,4,5-trimethoxyphenyl)-3,4,4a,5,8,8a-hexahydro-2H-4,8-epoxychromene exhibited high analgesic activity in both acetic acid-induced writhing and hot plate tests; its selectivity index IS₅₀ exceeded 60.

Full text of DOI:10.1007/s00044-012-0310-9

MEDICINAL
CHEMISTRY
RESEARCH
Med Chem Res (2013) 22:3026–3034
DOI 10.1007/s00044-012-0310-9
ORIGINAL RESEARCH
Synthesis and analgesic activity of new heterocyclic compounds
derived from monoterpenoids
•
Oksana Mikhalchenko Irina Il’ina Alla Pavlova Ekaterina Morozova
•
•
•
•
Dina Korchagina Tat’yana Tolstikova Evgeny Pokushalov
•
•
•
Konstantin Volcho Nariman Salakhutdinov
Received: 17 April 2012 / Accepted: 24 October 2012 / Published online: 9 November 2012
Ó Springer Science+Business Media New York 2012
Abstract A set of new heterocyclic compounds with dif-
ferent types of framework, including a new type of frame-
work, were synthesized by reactions of verbenol epoxide and
(1R,2R,6S)-3-methyl-6-(prop-1-en-2-yl)cyclohex-3-ene-1,
2-diol with aromatic aldehydes containing three methoxy
groups. The analgesic activity of these substances was
studied. Three compounds possessed considerable activity
in vivo in the acetic acid-induced writhing test. (2S,4R,4aR,
8S,8aR)-4,7-Dimethyl-2-(2,4,5-trimethoxyphenyl)-3,4,4a,
5,8,8a-hexahydro-2H-4,8-epoxychromene exhibited high
analgesic activity in both acetic acid-induced writhing and
hot plate tests; its selectivity index IS50 exceeded 60.
advances in understanding the biology of pain, new anal-
gesics, and improvements in analgesic delivery methods,
the treatment of pain is still inadequate and continues to be
a substantial worldwide public health concern especially
under treatment of cancer related pain (White et al., 2005;
Juniper et al., 2009). Thus, it is necessary to find highly
effective approaches or novel analgesic substances for pain
relief.
Earlier, we found (Il’ina et al., 2011) that the reaction of
monoterpenoids (-)-cis-verbenol epoxide 1 and (1R,2R,6S)-
3-methyl-6-(prop-1-en-2-yl)cyclohex-3-ene-1,2-diol 2 with
3,4,5-trimethoxybenzaldehyde 3a in the presence of mont-
morillonite clay K10 gave a set of intermolecular products
with differenttypesofframework:amixtureofdiastereomers
(5R)- and (5S)-4a with a chromene framework, compound 5
with a benzodioxine framework, and the product of addition
of two aldehyde molecules to epoxide 1 with an (epoxy-
methano)chromene framework 6a (Scheme 1). Although
rather complex reactionmixtureswereformed, theindividual
products were relatively easy to isolate because of noticeable
differences in the molecular mass and chemical nature of
these compounds.
Keywords Verbenol epoxide ꢀ Terpenoid ꢀ
Heterocyclic compounds ꢀ Analgesic activity ꢀ
Acetic acid-induced writhing test ꢀ Hot plate test
Introduction
Pain is the most common symptom for which patients seek
medical attention (Wolff et al., 2011). Despite exponential
Cannabinoids and their analogs with a combination of
a monoterpene fragment and the aromatic ring are known
to have a considerable analgesic activity (Finn and
Chapman, 2004; Costa, 2007; Lambert and Fowler,
2005). On the other hand, it was shown that the intro-
duction of several methoxy groups in the aromatic ring
led to increased analgesic activity of compounds with
different structural types (Palomba et al., 2000; Husain
et al., 2005; Wagle et al., 2008). Therefore, it seemed
promising (and is the goal of the present work) to syn-
thesize analogs of compounds 4a–6a with different
positions of methoxy groups for further studies of their
analgesic activity.
O. Mikhalchenko
Novosibirsk State University, Pirogova 2,
630090 Novosibirsk, Russian Federation
I. Il’ina ꢀ A. Pavlova ꢀ E. Morozova ꢀ D. Korchagina ꢀ
T. Tolstikova ꢀ K. Volcho (&) ꢀ N. Salakhutdinov
Novosibirsk Institute of Organic Chemistry, Siberian Branch,
Russian Academy of Sciences, Lavrentjev Ave.,
9, 630090 Novosibirsk, Russian Federation
e-mail: volcho@nioch.nsc.ru
E. Pokushalov
State Research Institute of Circulation Pathology,
Rechkunovskaya 15, 630055 Novosibirsk, Russian Federation
123

Med Chem Res (2013) 22:3026–3034
3027
O
MeO
MeO
OMe
OMe
MeO
O
OMe
OMe
MeO
MeO
CHO
OH
MeO
MeO
MeO
H
1
OH
OH
OMe
OMe
OMe
O
O
or
3a
O
H
+
+
H
O
5
O
OH
OH
OH
6a
4a
5
2
Scheme 1 The interaction of compounds 1 and 2 with 3,4,5-trimethoxybenaldehyde 3a
Chemistry
2,3,4-trimethoxybenzaldehyde 3b and 2,4,6-trimethoxy-
benzaldehyde 3d. It can be supposed that isomerization of
verbenol epoxide 1 into monoterpenoids 2, 7, and 8 may
proceed on various acidic centers of the clay. Aldehydes,
depending on the location of methoxy groups at the aro-
matic ring, in the process of adsorption on clay can block
some of the acidic sites, thus affecting the direction of
isomerization.
The interaction of verbenol epoxide 1 with aldehydes
3b–d, each containing three methoxy groups in different
positions of the aromatic ring, in the presence of clay K10
in CH2Cl2 for 1.5 h led to the formation of intermolecular
products 4b–d and 6b, in addition to the products of
isomerization 2, 7, and 8 (Table 1; Scheme 2).
It is interesting that the structure of the starting aldehyde
had a significant effect not only on the composition and
yield of intermolecular products but also on the ratio of
isomerization products. For example, in the case of 3,4,
5-trimethoxybenzaldehyde 3a and 2,4,5-trimethoxybenz-
aldehyde 3c, the reaction mixtures contained considerable
amounts of diol 2, which was absent in reactions with
The main intermolecular products were compounds 4
with a chromene framework in all instances, but in the
reaction of aldehyde 3d (containing substituents in both
ortho-positions) the yield of 4d was insignificant probably
because of steric hindrances. The ratio of (5S/5R)-diaste-
reomers in 4a–d depended considerably on the structure of
the aldehyde used; the reactions with 3a, b formed isomers
in approximately equal ratios, while the reactions with 3c,
d were much more selective and predominantly led to
(5S)-isomers.
Table 1 Yields of products in the reaction of (-)-cis-verbenol
epoxide 1 with aldehydes 3a–d
The reaction of diol 2 with aldehydes 3a–d in the
presence of clay K10 was much more sluggish than similar
reactions with epoxide 1. Although these reactions were
performed without a solvent and were thus considerably
accelerated (Volcho et al., 1999), the reaction mixture had
to be stored for 1–7 days to attain a complete conversion of
diol 2. It should be noted that CH2Cl2 was used for evenly
deposition of reagents on clay; CH2Cl2 then was
evaporated.
Aldehyde
Yields of products (%)
Intramolecular Intermolecular
N
Substituents
2
7
8
4 (5S:5R) 5
6
3aa R2, R6 = H; R3, R4,
R5 = OMe
10 12
7
6
6
25
(50:50)
15
(60:40)
11
(89:11)
17 13 3 (93:7)
6
–
–
–
5
3b R5, R6 = H; R2, R3,
R4 = OMe
–
15
2
–
–
3c R3, R6 = H; R2, R4,
R5 = OMe
11 17
The yield of compounds 4 with a chromene framework
was almost independent of the structure of aldehyde in all
reactions, except the reaction involving sterically crowded
aldehyde 3d (Scheme 3; Table 2). As in the case of
3d R3, R5 = H; R2, R4,
R6 = OMe
–
a
Il’ina et al. (2011)
Scheme 2 The interaction of
verbenol epoxide 1 with
aldehydes 3b–d
CHO
OH
CHO
O
OH
OH
R6
R5
R2
R3
OH
+
+
H
8
O
7
R4
3b-d
K10, CH2Cl2
2
R5
O
OH
R6
R4
R3
H
MeO
O
OMe
OMe
1
OH
3b, 4b R5, R6=H; R2, R3, R4=OMe
3c, 4c R3, R6=H; R2, R4, R5=OMe
3d, 4d R3, R5=H; R2, R4, R6=OMe
H
+
O
MeO
H
O
R2
4b-d
5
OMe
MeO
OH
6b
123

3028
Med Chem Res (2013) 22:3026–3034
18
R5
O
15
R6
R4
R3
15 OMe
OMe
H
MeO
O 3
9
1
CHO
R4
OH
1
7
27
R6
R5
R2
R3
13
23
18
3
O
H
9
11
11
+
MeO
H
R2
5
5
O
13
7
25
17
OMe
17
4b-d
OH
MeO
6b
OH
OH
3b-d
K10
MeO
OMe
OMe
13
14
15
13
OH
15
OMe
OMe
OMe
15
1
OH
1
O
1
12
2
17
2
6
18
18
9
3
13
3
O
3
O
9
11
+
10
4
+
11
11
3b, 4b R5, R6=H; R2, R3, R4=OMe
3c, 4c R3, R6=H; R2, R4, R5=OMe
3d, 4d R3, R5=H; R2, R4, R6=OMe
9
7
HO
OMe
5
8
7
OMe
5
7
5
OMe
H
11
10
17
O
9
17
16
Scheme 3 The interaction of compound 2 with aldehydes 3b–d
the allyl hydroxy group, followed by heterocyclization
accompanied by the elimination of water leading to inter-
mediate 13 (Scheme 5). The protonation of the benzyl
hydroxy group in 13, subsequent carbocyclization and water
elimination-addition can just lead to the formation of 11.
Thus, we obtained a set of new chiral compounds with
different types of framework, including a monoterpene
fragment and an aromatic ring with three methoxy groups
in different positions by one-pot synthesis from monot-
erpenoids 1 and 2.
Table 2 Yields of products in reactions of diol 2 with aldehydes
3a–d
Aldehyde
Yields of products (%)
N
Substituents
4 (5S:5R)
5
6
9
10 11
3aa R2, R6 = H; R3, R4,
R5 = OMe
39 (60:40)
3
9
–
–
–
–
2
–
3b R5, R6 = H; R2, R3,
R4 = OMe
39 (57:43)
39 (67:33)
14 (75:25)
–
–
–
9
–
–
7
–
–
–
3c R3, R6 = H; R2, R4,
R5 = OMe
15
–
3d R3, R5 = H; R2, R4,
R6 = OMe
Biology
a
Il’ina et al. (2011)
All the synthesized compounds, except 11 obtained with a
yield of only 2 %, were tested for analgesic activity. In the
case of compounds 4 we used mixtures of diastereomers
obtained in the reactions with diol 2 (Table 2) without
separation.
verbenol epoxide 1, the reaction became more diastereo-
selective on passing from aldehydes 3a, b to aldehydes 3c,
d, but the effect was less significant. At the same time, the
structure of minor intermolecular products influenced by
the structure of the aldehyde used. For example, compound
5 with a benzodioxine framework was formed only in the
case of aldehyde 3a, the diene 9 was isolated in the reaction
with aldehyde 3b, and tricyclic compounds 10 and 11 were
formed in the reaction with aldehyde 3c.
The analgesic activity of the compounds in a dose of
10.0 mg/kg (oral administration) was studied in the stan-
dard experimental pain models, namely the acetic acid-
induced writhing (0.75 % acetic acid, 0.1 ml for one
animal, intraperitoneally) and hot plate (thermal stimula-
tion, T = 54 0.5 °C) tests (Koster et al., 1959; Eddy and
Leimbach, 1953). Sodium diclofenac in the same dose was
used as a reference drug.
Compound 9 is evidently formed from 4b as a result of
dehydration. A possible mechanism of the formation of
compound 10 is presented in Scheme 4. It involves intra-
molecular heterocyclization in compound (5S)-4c. The
formation of 10 from isomer (5R)-4c seems impossible for
steric reasons. The suggested mechanism was confirmed by
the presence of 10 in the reaction mixture after storing 4c
under reaction conditions with diastereomer (5S)-4c spent
in predominant amounts (GLC-MS data), just as would be
expected in this case. To the best of our knowledge, the
framework of epoxychromene 10 is new.
The data of Table 3 show that compounds 4b, 6a, and 10
taken in a dose of 10 mg/kg exhibited a considerable anal-
gesic activity in the acetic acid-induced writhing test, sig-
nificantly reducing the writhing caused by the introduction of
acetic acid in animals. The highest activity in this test was
observed for compound 4b with two-thirds of animals
showing no writhing at all in this case (in the control group of
mice, writhing was observed for all animals).
In the hot plate test, however, only tricyclic compound
10 showed analgesic activity (Table 4). Compound 10 was
more effective than the sodium diclofenac reference taken
in the same dose in this test.
The supposed mechanism of the formation of minor tri-
cyclic compound 11 can involve an attack of double bond of
diol 2 at the protonated aldehyde 3c, the addition of a water
molecule to the resulting carbocation 12 and protonation of
123

Med Chem Res (2013) 22:3026–3034
3029
Scheme 4 The mechanism of
formation of compound 10
OMe
OMe
MeO
O
OMe
OMe
MeO
O
OMe
OMe
OH
H
OH2
H
OMe
O
+H+
-H2O
-H+
O
OH
(5S)-4c
OH
H
10
OH
OH2
O
HO
MeO
MeO
OH
OH
OH
HO
OH
OH +H2O
+H+
- H O
OH
2
OMe
MeO
MeO
MeO
MeO
- H+
MeO
MeO
OH
OMe
OMe
2
12
OMe
13
HO
+H+
HO
H2O
O
MeO
OH
OMe
O
OH
OH
H2O
MeO
MeO
- H+
HO
OMe
11
MeO
MeO
OMe
OMe
O
Scheme 5 The mechanism of formation of compound 11
Curiously, analgesic activity was found in compounds of
different structural types with methoxy groups in different
positions of the aromatic ring, stimulating further search
for new analgesics among compounds with combinations
of monoterpene and aromatic fragments.
of 10 was determined by the Kerber method by a single
intragastric administration in mice. LD50 (median lethal
dose) is the quantity of an agent that will kill 50 % of the
test subjects. Compound 10 proved moderately toxic, it’s
LD50 exceeding 1,500 mg/kg. Thus, the selectivity index
IS50 (LD50/ED50) of 10 exceeded 60 for both tests. For
comparison, the IS50 of acetylsalicylic acid in the acetic
acid-induced writhing test is 10.3 (Syubaev et al., 1986).
For compound 10, which exhibited high analgesic
activity in both tests, we determined ED50 (the ‘‘median
effective dose’’ is a dose which produces the 50 % of
protection) (22 mg/kg in the acetic acid-induced writhing
test and 25 mg/kg in the hot plate test). The acute toxicity
Conclusion
Table 3 Analgesic activity of compounds 4a–d, 5, 6a, b, and 10 and
sodium diclofenac in the acetic acid-induced writhing test (10 mg/kg
dose)
To summarize, we synthesized a set of new polycyclic
compounds with different types of framework, including
Compound
Mean SD
Control
Pain inhibition (%)
(percent of animals
without symptoms)
Table 4 Analgesic activity of compounds 4a–d, 5, 6a, b, and 10 and
sodium diclofenac in the hot plate test (10 mg/kg dose)
4a
4b
4c
4d
5
8.5 1.9
2.8 1.6
7.5 1.5
12.1 1.0
12.6 1.3
6.3 1.6
7.8 1.3
3.8 0.9
0.8 0.4
10.1 0.7
10.9 0.9
10.1 0.7
13.9 1.0
14.4 0.9
12.6 1.3
10.1 0.7
10.9 0.9
8.4 0.8
16
74# (63)
Compound
Mean SD
Control
Protection (%)
4a
13.1 1.2
11.8 1.2
15.4 1.2
13.3 2.4
14.3 1.0
14.6 2.0
13.4 1.9
18.1 1.9
33.4 2.3
12.3 1.7
10.5 1.8
12.3 1.7
11.9 1.3
12.3 0.9
12.3 0.9
12.3 1.7
10.5 1.8
20.4 2.2
7
12
25
12
16
19
9
26
4b
13
4c
13
4d
6a
6b
10
50* (25)
5
23
65# (25)
90# (87.5)
6a
6b
Diclofenac
sodium
10
72#
64*
Diclofenac sodium
% of protection = (texp - tcontrol)/tcontrol 9 100 %
#
* p \ 0.01; p \ 0.001 in comparison with control
#
* p \ 0.01; p \ 0.001 in comparison with control
123

3030
Med Chem Res (2013) 22:3026–3034
new ones, by reactions of monoterpenoids verbenol epox-
ide 1 and diol 2 with aromatic aldehydes each containing
three methoxy groups. Studies of the analgesic activity of
these compounds showed that three compounds (4b, 6a,
and 10) had a considerable activity in vivo in the acetic
acid-induced writhing test. One of these substances
(10) also showed high analgesic activity in the hot plate
test. The selectivity index IS50 of 10 exceeded 60 for both
tests.
solvent distilled off, and the residue was separated on a
SiO2 column.
With 2,3,4-trimethoxybenzaldehyde 3b
The reaction of epoxide 1 (0.800 g) and aldehyde 3b
(0.930 g) in the presence of clay K10 (3.5 g) gave
compounds 7 (0.120 g, 15 %), 8 (0.048 g, 6 %), 4b
(5S:5R = 60:40) (0.260 g, 15 %), and 6b (0.052 g, 2 %).
The spectral data of 7 and 8 coincided with those reported
in the literature (Il’ina et al., 2007; Ardashov et al., 2007).
The NMR spectra of isomers (5S)- and (5R)-4b were
recorded for the mixture of isomers.
Experimental
Chemistry
Here and below, the ratio of diastereomers (5S:5R) for
products of type 4 was determined from the NMR spectrum
by the ratio of the peak areas of Ha-3. Methyl group at the
carbon atom C(5) (Scheme 2) is axial in (5S)-4, as indi-
All the chemicals reagents were of commercial grade. As
catalyst, weusedK10clay(Fluka). Theclaywascalcinatedat
110 °C for 3 h immediately before use. CH2Cl2 was passed
through calcined Al2O3. (-)-cis-Verbenol epoxide (1)
4
cated by the presence of long range J(C17H3, Ha-4) of
0.8 Hz, but equatorial in (5R)-4. In the latter case, as would
be expected, the axial OH group causes a paramagnetic
shift Dd = 0.34 of the Ha-3 signal due to the 1,3-diaxial
interaction.
20
(½aꢁ580 = -60 (c = 0.41, CHCl3)) and (1R,2R,6S)-3-methyl-
31
6-(prop-1-en-2-yl)cyclohex-3-ene-1,2-diol (½aꢁD = -49.1
(c = 2.6, CHCl3)) were synthesized according to (Il’ina
et al., 2007) from (-)-verbenone (Aldrich), the content of the
main substance was not less than 98.0 %. All product yields
(except compound 11) are given for pure compounds isolated
by column chromatography. Column chromatography (CC):
silica gel (SiO2; 60–200l; Macherey–Nagel); hexane/EtOAc
100/0 ? 0/100, acetone. GC/MS (purity control and prod-
ucts analysis): Hewlett–Packard 5890/II gas chromatograph
with a quadrupole mass spectrometer (HP MSD 5971) as a
detector, HP-5MS quartz column, 30 m 9 0.25 mm, He as
carrier gas. Optical rotation: polAAr 3005 spectrometer,
CHCl3 soln. HR-MS: DFS-Thermo-Scientific spectrometer
in a full scan mode (15–500 m/z, 70 eV electron-impact
(2S,4S,4aR,8R,8aR)-4,7-Dimethyl-2-(2,3,4-trimethoxyphenyl)-
3,4,4a,5,8,8a-hexahydro-2H-chromene-4,8-diol ((5S)-
4b) 1H NMR (CDCl3): 1.52 (s, 3H, H-17); 1.62 (ddd,
J(4e,4a) = 13.4 Hz, J(4e,3a) = 2.7 Hz, J(4e,6) = 1.1 Hz,
1H, He-4); 1.79 (m, all J B 2.5 Hz, 3H, H-18); 1.77–1.84 (m,
1H, Ha-6); 1.94 (dd, J(4a,4e) = 13.4 Hz, J(4a,3a) =
12.0 Hz, 1H, Ha-4); 2.16–2.21 (m, 2H, H-7); 3.80 (s,
OC21H3); 3.824 (s, OC20H3); 3.86 (s, OC19H3); 3.81 (dd,
J(1e,6) = 2.4 Hz, J(1e,10e) = 2.0 Hz, 1H, He-1); 3.87
(br.s, 1H, He-10); 4.67 (dd, J(3a,4a) = 12.0 Hz, J(3a,4e) =
2.7 Hz, 1H, Ha-3); 5.62–5.63 (m, 1H, H-8); 6.63 (d,
J(15,16) = 8.5 Hz, 1H, H-15); 7.00 (d, J(16,15) = 8.5 Hz,
1H, H-16).
13C NMR (CDCl3): 77.74 (d, C-1); 72.41 (d, C-3); 42.02
(t, C-4); 71.13 (s, C-5); 38.38 (d, C-6); 22.73 (t, C-7);
124.63 (d, C-8); 131.39 (s, C-9); 70.55 (d, C-10); 127.92 (s,
C-11); 150.80 (s, C-12); 141.93 (s, C-13); 153.06 (s, C-14);
107.53 (d, C-15); 121.14 (d, C-16) 26.91 (q, C-17); 20.67
(q, C-18); 61.23 (q, C-19); 60.59 (q, C-20); 55.89 (q, C-21).
HR-MS: 364.1881 (M?, C20H28O6?; calc. 364.1880).
ionization, direct sample introduction). H and 13C NMR:
1
Bruker DRX-500 apparatus at 500.13 MHz (1H) and
125.76 MHz (13C) in CDCl3; chemical shifts d in ppm rela-
tive to residual CHCl3 (d(H) 7.24, d(C) 76.90 ppm), J in Hz;
structure determinations by analyzing the 1H NMR spectra,
1H–1H double resonance spectra, J-modulated 13C NMR
spectra (JMOD), 13C NMR spectra with proton off-resonance
saturation, and 13C–1H 2D heteronuclear correlation with
one-bond and long-range spin–spin coupling constants (C–H
COSY, 1J(C,H) = 135 Hz, COLOC, 2,3J(C, H) = 10 Hz).
(2S,4R,4aR,8R,8aR)-4,7-Dimethyl-2-(2,3,4-trimethoxyphenyl)-
3,4,4a,5,8,8a-hexahydro-2H-chromene-4,8-diol ((5R)-
4b) 1H NMR (CDCl3): 1.21 (s, 3H, H-17); 1.57 (ddd,
J(4e,4a) = 14.2 Hz, J(4e,3a) = 2.7 Hz, J(4e,6) = 1.3 Hz,
1H, He-4); 1.70 (br.t, J(6a,7) = 9 Hz, 1H, Ha-6); 1.79 (m,
all J B 2.5 Hz, 3H, H-18); 1,84 (dd, J(4a,4e) = 14.2 Hz;
J(4a,3a) = 11.8 Hz, 1H, Ha-4); 1.99–2.04 (m, 2H, H-7);
3.79 (s, OC21H3); 3.825 (s, OC20H3); 3.85 (s, OC19H3);
3.89 (br.s, 1H, He-10); 4.25 (dd, J(1e,6a) = 2.5 Hz,
Reaction of (-)-cis-verbenol epoxide 1 with aldehydes
3b–d on clay K10: general procedure
An appropriate aldehyde was added to a suspension of clay
K10 in CH2Cl2 (10 ml). A solution of epoxide 1 in CH2Cl2
(20 ml) was added dropwise with stirring and the reaction
mixture was stirred for 1.5 h at r.t. Then, ethyl acetate
(20 ml) was added. The catalyst was filtered off, the
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Med Chem Res (2013) 22:3026–3034
3031
(2S,4S,4aR,8R,8aR)-4,7-Dimethyl-2-(2,4,5-trimethoxyphenyl)-
3,4,4a,5,8,8a-hexahydro-2H-chromene-4,8-diol ((5S)-4c) 1H
NMR (CDCl3): 1.52 (s, 3H, H-17); 1.68 (ddd, J(4e,4a) =
13.2 Hz, J(4e,3a) = 2.7 Hz, J(4e,6) = 1.1 Hz, 1H, He-4);
1.77–1.85 (m, 2H, H- 6, Ha-4); 1.81 (m, all J B 2.5 Hz,
3H, H-18); 2.15–2.20 (m, 2H, H-7); 3.78 s, 3.79 s, 3.84 s,
(3 OCH3); 3.81 (dd, J(1e,6) = 2.4 Hz, J(1e,10e) =
2.0 Hz, 1H, He-1); 3.90 (br.s, 1H, He-10); 4.76 (dd,
J(3a,4a) = 11.4 Hz, J(3a,4e) = 2.7 Hz, 1H, Ha-3);
5.63–5.67 (m, 1H, H-8); 6.46 (s, 1H, H-13); 6.88 (s, 1H,
H-16).
J(1e,10e) = 2.0 Hz, 1H, He-1); 4.98 (dd, J(3a,4a) =
11.8 Hz, J(3a,4e) = 2.7 Hz, 1H, Ha-3); 5.56–5.59 (m, 1H,
H-8); 6.61 (d, J(15,16) = 8.5 Hz, 1H, H-15); 6.99 (d,
J(16,15) = 8.5 Hz, 1H, H-16).
13C NMR (CDCl3): 75.26 (d, C-1); 71.14 (d, C-3); 40.97
(t, C-4); 70.79 (s, C-5); 37.87 (d, C-6); 24.56 (t, C-7);
123.95 (d, C-8); 131.90 (s, C-9); 70.52 (d, C-10); 128.56 (s,
C-11); 150.95 (s, C-12); 142.04 (s, C-13); 152.93 (s, C-14);
107.53 (d, C-15); 121.36 (d, C-16); 28.30 (q, C-17); 20.77
(q, C-18); 61.29 (q, C-19); 60.59 (q, C-20); 55.89 (q, C-21).
HR-MS: 364.1881 (M?, C20H28O6?; calc. 364.1880).
13C NMR (CDCl3): 77.72 (d, C-1); 71.58 (d, C-3); 41.87
(t, C-4); 71.16 (s, C-5); 38.50 (d, C-6); 22.71 (t, C-7);
124.58 (d, C-8); 131.43 (s, C-9); 70.61 (d, C-10); 122.09 (s,
C-11); 150.24 (s, C-12); 97.67 (d, C-13); 149.03 (s, C-14);
143.31 (s, C-15); 111.10 (d, C-16); 27.00 (q, C-17); 20.67
(q, C-18); 56.07, 56.49 and 56.77 (3q, C-19, C-20, C-21).
HR-MS: 364.1878 (M?, C20H28O6?; calc. 364.1880).
(2R,4S,4aR,6S,7R,8aR,9S)-4,7-Dimethyl-2,9-bis(2,3,4-
trimethoxyphenyl)hexahydro-2H-4,6-(epoxymethano)
chromen-8(8aH)-one (6b) 1H NMR (CDCl3): 1.07 (d,
J(18,9) = 7.5 Hz, 3H, H-18); 1.40 (s, 3H, H-17); 1.67 (dd,
J(4a,4e) = 13.8 Hz, J(4a,3e) = 12.0 Hz, 1H, Ha-4); 1.92
(m, all J B 3.1 Hz, 1H, He-8); 1.93 (dd, J(4e,4a) =
13.8 Hz, J(4e,3a) = 2.6 Hz, 1H, He-4); 2.00 (ddd,
J(7a,7e) = 14.2 Hz, J(7a,6e) = 3.3 Hz, J(7a,8) = 3.0 Hz,
1H, Ha-7); 2.31 (dddd, J(6e,1a) = 5.9 Hz, J(6e,7a) =
3.3 Hz, J(6e,7e) = 3.1 Hz, J(6e,8e) = 0.5 Hz, 1H, He-6);
2.43 (dddd, J(7e,7a) = 14.2 Hz, J(7e,6e) = 3.1 Hz,
J(7e,8) = 3.1 Hz, J(7e,9e) = 1.8 Hz, 1H, He-7); 2.46
(qdd, J(9e,18) = 7.5 Hz, J(9e,8e) = 2.2 Hz, J(9e,7e) =
1.8 Hz, 1H, He-9); 3.809 s and 3.822 s (OC21H3,
OC31H3); 3.816 (s, OC30H3); 3.85 (s, OC20H3); 3.87 (s,
OC29H3); 3.96 (s, OC19H3); 4.38 (d, J(1a, 6e) = 5.9 Hz,
1H, Ha-1); 5.24 (d, J(22,8e) = 2.1 Hz, H-22); 5.38 (dd,
J(3a,4a) = 12.0 Hz, J(3a,4e) = 2.6 Hz, 1H, Ha-3); 6.65
(d, J(15,16) = 8.6 Hz, H- 15); 6.70 (d, J(27,28) =
8.6 Hz, 1H, H-27); 7.04 (d, J(28,27) = 8.6 Hz, 1H,
H-28); 7.14 (d, J(16,15) = 8.6 Hz, 1H, H-16).
(2S,4R,4aR,8R,8aR)-4,7-Dimethyl-2-(2,4,5-trimethoxyphenyl)-
3,4,4a,5,8,8a-hexahydro-2H-chromene-4,8-diol ((5R)-4c) 1H
NMR (CDCl3): 1.20 (s, 3H, H-17); 1.62 (ddd, J(4e,4a) =
14.2 Hz, J(4e,3a) = 3.2 Hz, J(4e,6) = 1.3 Hz, 1H, He-4);
1.65–1.69 (m, 1H, H- 6); 1.69 (dd, J(4a,4e) = 14.2 Hz;
J(4a,3a) = 11.4 Hz, 1H, Ha-4); 1.99–2.04 (m, 2H, H-7);
3.77 s, 3.79 s, 3.83 s (3 OMe); 3.91 (br.s, 1H, He-10); 4.24
(dd, J(1e,6) = 2.4 Hz, J(1e,10e) = 2.1 Hz, 1H, He-1);
5.08 (dd, J(3a,4a) = 11.4 Hz, J(3a,4e) = 3.2 Hz, 1H, Ha-
3); 5.57–5.61 (m, 1H, H-8); 6.47 (s, 1H, H-13); 6.89 (s, 1H,
H-16).
13C NMR (CDCl3): 75.28 (d, C-1); 70.09 (d, C-3); 40.91
(t, C-4); 70.86 (s, C-5); 38.04 (d, C-6); 24.60 (t, C-7);
123.91 (d, C-8); 131.94 (s, C-9); 70.58 (d, C-10); 122.78 (s,
C-11); 150.33 (s, C-12); 97.79 (d, C-13); 148.89 (s, C-14);
143.29 (s, C-15); 111.32 (d, C-16); 28.32 (q, C-17); 20.77
(q, C-18); 56.12, 56.51 and 56.77 (3 q, C-19, C-20, C-21).
HR-MS: 364.1878 (M?, C20H28O6?; calc. 364.1880).
13C NMR (CDCl3): 76.49 (d, C-1); 64.80 (d, C-3); 45.79
(t, C-4); 72.92 (s, C-5); 41.22 (d, C-6); 22.38(t, C-7); 40.36
(d, C-8); 43.75 (d, C-9); 210.11 (s, C-10); 128.37 (s, C-11);
151.09 (s, C-12); 141.97 (s, C-13), 152.79 (s, C-14); 107.50
(d, C-15); 121.25 (d, C-16); 21.89 (q, C-17); 17.54 (q,
C-18); 61.17 (q, C-19); 60.58, 60.61 and 60.53 (3q, C-20,
C-29, C-30); 55.80 and 55.88 (2 q, C-21, C-31); 71.04 (d,
C-22); 125.73 (s, C-23); 149.56 (s, C-24); 141.42 (s, C-25);
152.71 (s, C-26); 107.19 (d, C-27); 122.11 (d, C-28).
With 2,4,6-trimethoxybenzaldehyde 3d
The reaction of epoxide 1 (0.800 g) and aldehyde 3d
(0.800 g) in the presence of clay K10 (3.0 g) gave com-
21
½aꢁD = - 46,7 (c = 1.99); HR-MS: 542.2513 (M?,
pounds
7 (0.140 g, 17 %), 8 (0.103 g, 13 %), 4d
C30H38O9?; calc. 542.2510).
(5S:5R = 93:7) (0.057 g, 3 %), and 6b (0.052 g, 2 %).
The NMR spectra of isomers (5S)- and (5R)-4d were
recorded for the mixture of isomers.
With 2,4,5-trimethoxybenzaldehyde 3c
(2S,4S,4aR,8R,8aR)-4,7-Dimethyl-2-(2,4,6-trimethoxyphenyl)-
3,4,4a,5,8,8a-hexahydro-2H-chromene-4,8-diol ((5S)-4d) 1H
NMR (CDCl3): 1.31 (ddd, J(4e,4a) = 13.1 Hz, J(4e,3a) =
3.1 Hz, J(4e,6a) = 1.1 Hz, 1H, He-4); 1.49 (s, 3H, H-17);
1.73 (dddd, J(6a,7a) = 11.0 Hz, J(6a,7e) = 5.8 Hz,
J(6a,1e) = 2.4 Hz, J(6a,4e) = 1.1 Hz, 1H, Ha-6); 1.77
The reaction of epoxide 1 (0.700 g) and aldehyde 3c
(0.800 g) in the presence of clay K10 (3.0 g) gave com-
pounds 7 (0.100 g, 17 %), 8 (0.033 g, 6 %), 2 (0.075 g,
11 %), 4c (5S:5R = 89:11) (0.160 g, 11 %).
The NMR spectra of isomers (5S)- and (5R)-4c were
recorded for the mixture of isomers.
123

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Med Chem Res (2013) 22:3026–3034
(br.s, 3H, H-18); 2.13 (dddq, J(7e,7a) = 17.5 Hz,
J(7e,6a) = 5.8 Hz, J(7e,8) = 5.2 Hz, J(7e,18) = 1.5 Hz,
1H, He-7); 2.40 (ddm, J(7a,7e) = 17.5 Hz, J(7a,6a) =
11.0 Hz, 1H, Ha-7); 2.66 (dd, J(4a,4e) = 13.1 Hz,
J(4a,3a) = 12.2 Hz, 1H, Ha-4); 3.73 (s, 6H, 3H-19, 3H-
21); 3.73 (br.s, 1H, He-1); 3.75 (s, 3H, OC20H3); 3.88 (br.s,
1H, He-10); 5.01 (dd, J(3a,4a) = 12.2 Hz, J(3a,4e) =
3.1 Hz, 1H, Ha-3); 5.63–5.67 (m, 1H, H-8), 6,09 (s, 2H,
H-13, H-15).
13C NMR (CDCl3): 77.64 (d, C-1); 69.39 (d, C-3); 38.47
(t, C-4); 71.47 (s, C-5); 38.98 (d, C-6); 22.70 (t, C-7);
124.97 (d, C-8); 131.30 (s, C-9); 70.74 (d, C-10); 110.44 (s,
C-11); 159.55 (s, C-12); 91.83 (d, C-13); 160.70 (s, C-14);
91.83 (d, C-15); 159.55 (s, C-16); 26.82 (q, C-17); 20.58
(q, C-18); 56.04 (q, C-19); 55.16 (q, C-20); 56.04 (q, C-21).
HR-MS: 364.1877 (M?, C20 H28 O6?; calc. 364.1880).
compounds 4b (5S:5R = 57:43) (0.747 g, 43 %), and 9
(0.108 g, 7 %).
(2S,4aS,8R,8aR)-7-Methyl-4-methylene-2-(2,3,4-
trimethoxyphenyl)-3,4,4a,5,8,8a-hexahydro-2H-chromen-
8-ol (9) 1H NMR (CDCl3): 1.80 (br.s, 3H, H-18); 1.95
(dddq, J(7e,7a) = 17.7 Hz, J(7e,6a) = 6.4 Hz, J(7e,8) =
5.1 Hz, J(7e,18) = 1.5 Hz, 1H, He-7); 2.26 (dd, J(4e,4a) =
14.1 Hz, J(4e,3a) = 2.9 Hz, 1H, He-4); 2.37 (dddqd,
J(7a,7e) = 17.7 Hz, J(7a,6a) = 10.8 Hz, J(7a,8) =2.5 Hz,
J(7a,18) = 2.5 Hz, J(7a,10e) = 1.5 Hz, 1H, Ha-7);
2.50–2.57 (m, 2H, Ha-6, Ha-4); 3,73 (dd, J(1e,6a) =
2.4 Hz; J(1e,10e) = 2.0 Hz, 1H, He-1); 3.81 (s, 3H,
OC21H3); 3.84 (s, 3H, OC20H3); 3.86 (s, 3H, OC19H3); 3.88
(br.s, 1H, He-10); 4.61 (dd, J(3a,4a) = 11.6 Hz, J(3a,4e) =
2.9 Hz, 1H, Ha-3); 4.78 (dd, J(17,170) = 2.5 Hz,
J(17,6a) = 2.0 Hz, 1H, H-17); 4.88 (dd, J(170,17) =
2.5 Hz, J(170,4a) = 2.0 Hz, 1H, H-170); 5.60-5.64 (m, 1H,
H-8); 6.64 (d, J(15,16) = 8.5 Hz, 1H, H-15); 7.05 (d,
J(16,15) = 8.5 Hz, 1H, H-16).
(2S,4R,4aR,8R,8aR)-4,7-Dimethyl-2-(2,4,6-trimethoxyphenyl)-
3,4,4a,5,8,8a-hexahydro-2H-chromene-4,8-diol ((5R)-4d) 1H
NMR (CDCl3): 1.21 (s, 3H, H-17); 1.25 (ddd, J(4e,4a) =
14.0 Hz, J(4e,3a) = 3.2 Hz, J(4e,6) = 1.3 Hz, 1H, He-4);
1.59–1.64 (m, 1H, H-6); 1.77 (br.s, 3H, H-18); 1.97 (dddq,
J(7e,7a) = 17.5 Hz, J(7e,6) = 5.9 Hz, J(7e,8) = 5.2 Hz,
J(7e,18) = 1.3 Hz, 1H, He-7); 2.20–2.29 (m, 1H, Ha-7);
2.56 (dd, J(4a,4e) = 14.0 Hz, J(4a,3a) = 12.1 Hz, 1H, Ha-
4); 3.72 (s, 6H, OC19H3, OC21H3); 3.74 (s, 3H, OC20H3);
3.89 (br.s, 1H, He-10); 4.17 (dd, J(1e,6) = 2.4 Hz,
J(1e,10e) = 2.0 Hz, 1H, He-1); 5.33 (dd, J(3a,4a) =
12.1 Hz, J(3a,4e) = 3.2 Hz, 1H, Ha-3); 5.56–5.60 (m, 1H,
H-8); 6.09 (2H, H-13, H-15).
13C NMR (CDCl3): 80.55 (d, C-1); 75.64 (d, C-3); 37.59
(t, C-4); 147.15 (s, C-5); 36.81 (d, C-6); 26.28 (t, C-7);
124.43 (d, C-8); 131.52 (s, C-9); 70.36 (d, C-10); 128.27 (s,
C-11); 150.91 (s, C-12); 141.98 (s, C-13); 153.05 (s, C-14);
107.51 (d, C-15); 121.12 (d, C-16); 109.45 (t, C-17); 20.85
(q, C-18); 61.24 (q, C-19); 60.59 (q, C-20); 55.90 (q, C-21).
21
½aꢁD = - 32.25 (c = 0.8); HR-MS: 346.1769 (M?,
C26H30O5?; calc. 346.1774).
With 2,4,5-trimethoxybenzaldehyde 3c
13C NMR (CDCl3): 75.16 (d, C-1); 67.69 (d, C-3); 37.38
(t, C-4); 71.13 (s, C-5); 38.45 (d, C-6); 24.50 (t, C-7);
124.41 (d, C-8); 131.73 (s, C-9); 70.70 (d, C-10); 111.05 (s,
C-11); 159.71 (s, C-12); 92.05 (d, C-13); 160.60 (s, C-14);
92.05 (d, C-15); 159.71 (s, C-16); 28.61 (q, C-17); 20.69
(q, C-18); 56.14 (q, C-19); 55.16 (q, C-20); 56.14 (q, C-21).
HR-MS: 364.1877 (M?, C20 H28 O6?; calc. 364.1880).
The reaction of diol 2 (0.700 g) and aldehyde 3c (0.800 g)
for 1 week in the presence of clay K10 (3.0 g) gave mix-
ture 4c and 11 (0.216 g 4c and 0.029 g 11, calc. yield of 11
is 2 %), 4c (5S:5R = 67:33) (0.371 g, 24 %), overall yield
of 4c is 39 %, 10 (0.217 g, 15 %).
(2S,4R,4aR,8S,8aR)-4,7-Dimethyl-2-(2,4,5-trimethoxyphenyl)-
(10) 1H
Reaction of diol 2 with aldehydes 3b–d on clay K10:
general procedure
3,4,4a,5,8,8a-hexahydro-2H-4,8-epoxychromene
NMR (CDCl3): 1.36 (s, 3H, H-17); 1.52 (dd, J(4a,4e) =
13.1 Hz, J(4a,3a) = 10.6 Hz, 1H, Ha-4); 1.75 (m, all
J B 2.5 Hz, 3H, H-18); 1.91 (dd, J(4e,4a) = 13.1 Hz;
J(4e,3a) = 4.2 Hz, 1H, He-4); 2.08 (br.d, J(6,7) = 5.6 Hz;
1H, H-6); 2.37 (dddq, 2J = 18.6 Hz, J(7,6) = 5.6 Hz,
J(7,8) = 3.0 Hz, J(7,18) = 2.2 Hz, 1H, H-7); 2.53 (dm,
2J = 18.6 Hz, 1H, H’-7); 3.77 (s, 3H, OC19H3); 3.84 (s,
3H, OC21H3); 3.85 (s, 3H, OC20H3); 4.25 (br.s, 1H, H-10);
4.44 (d, J(1,6) = 1.2 Hz, 1H, H-1); 5.13–5.17 (m, 1H,
H-8); 5.42 (dd, J(3a,4a) = 10.6 Hz; J(3a,4e) = 4.2 Hz,
1H, Ha-3); 6.47 (s, 1H, H-13); 7.01 (s, 1H, H-16).
An appropriate aldehyde was added to a suspension of clay
K10 in CH2Cl2 (10 ml). A solution of diol 2 in CH2Cl2
(20 ml) was added dropwise with stirring. The solvent was
distilled off. The mixture was stored at r.t. for the required
period of time. Then, ethyl acetate (20 ml) was added. The
catalyst was filtered off, the solvent distilled off, and the
residue was separated on a SiO2 column.
With 2,3,4-trimethoxybenzaldehyde 3b
13C NMR (CDCl3): 81.07 (d, C-1); 68.21 (d, C-3); 45.69
(t, C-4); 83.33 (s, C-5); 45.66 (d, C-6); 28.20 (t, C-7);
120.66 (d, C-8); 139.86 (s, C-9); 80.21 (d, C-10); 122.15 (s,
The reaction of diol 2 (0.800 g) and aldehyde 3b (0.930 g)
for 24 h in the presence of clay K10 (3.5 g) gave
123

Med Chem Res (2013) 22:3026–3034
3033
C-11); 150.31 (s, C-12); 97.44 (d, C-13); 148.54 (s, C-14);
143.20 (s, C-15); 110.67 (d, C-16); 21.48 (q, C-17); 20.91
(q, C-18); 56.27 (q, C-19); 56.07 (q, C-20); 56.51 (q, C-21).
testing. Analgesic activity of test agents was assessed using
acetic acid-induced writhing test and hot plate test.
In the acetic acid-induced writhing test, the pain reaction
was determined by the number of abdominal convulsions,
recorded from the fifth to eighth minute following the
acetic acid injection (0.75 %, 0.1 mL/mouse) (Koster
et al., 1959). The percentage of pain reaction inhibition
was calculated according to the following equation: %
inhibition = 100 9 (A-B)/A, where A is the mean num-
ber of writhes in the control group, and B is the mean
number of writhes in the test group.
23
½aꢁD = - 4.3 (c = 0.6). HR-MS: 346.1774 (M?,
C20H26O5?; calc. 346.1774).
(2S,3aR,4R,5R,6S,7aS,8R)-7a,8-Dimethyl-6-(2,4,5-trime-
thoxyphenyl)octahydro-2,5-methanobenzofuran-4,8-diol
(11): the NMR spectra of 11 were recorded for the
mixture with 4c 1H NMR (CDCl3): 1.30 (s, 3H, H-16);
1.58 (s, 3H, H-17); 1.90–1.97 (m, 2H, H-2, H-7); 1.96 (dd,
J(4e,4a) = 13.1 Hz, J(4e,3a) = 8.2 Hz, 1H, He-4);
2.02–2.06 (m, 1H, H-6); 2.14 (d, 2J = 11.4 Hz, 1H, H’-7);
2.47 (dd, J(4a,4e) = 13.1 Hz, J(4a,3a) = 10.4 Hz, 1H,
Ha-4); 3.65 (dd, J(3a,4a) = 10.4 Hz, J(3a,4e) = 8.2 Hz,
1H, Ha-3); 3.77–3.79 (m, 1H, H-8); 3.78 (s, 3H, OC18H3);
3.80 (s, 3H, OC20H3); 3.85 (s, 3H, OC19H3); 4.35 (d,
J(1,2) = 4.4 Hz, 1H, H-1); 6.47 (s, 1H, H-12); 7.20 (s, 1H,
H-15).
13C NMR (CDCl3): 72.50 (d, C-1); 54.00 (d, C-2); 30.55
(d, C-3); 35.17 (t, C-4); 80.80 (s, C-5); 46.43 (d, C-6);
32.17 (t, C-7); 83.21 (d, C-8); 75.28 (s, C-9); 126.11 (s,
C-10); 151.42 (s, C-11); 97.45 (d, C-12); 147.49 (s, C-13);
142.34 (s, C-14); 113.43 (d, C-15); 27.95 (q, C-16); 26.33
(q, C-17); 55.68 (q, C-18); 56.12 (q, C-19); 56.71 (q, C-20).
In the hot plate test, animals were placed individually on
a metallic plate warmed to 54 0.5 °C and the time until
either licking of the hind paw or jumping occurred was
recorded by a stopwatch (Eddy and Leimbach, 1953).
Statistical data processing was carried out by a Statistica
6.0 program.
Acknowledgments Authors are grateful to the Presidium of Russian
Academy of Sciences (Program No. 28) and Russian Foundation for
Basic Research (Grant No. 10-03-00230a) for the financial support.
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