Synthesis and analgesic-like effect of (6R, 4S)-p-Mentha-1,8-dien-6- ylmethylene-p-toluenesulfonamide

Article abstract of DOI:10.1515/znb-2009-0319

The synthesis of a monoterpene-based para-toluenesulfonamide is reported starting from naturally occurring (R)- (-)-carvone (1), by 1,2-addition of HCN followed by reduction with lithium aluminum hydride to afford the amino alcohols 3a and 3b. Tosylation

Full text of DOI:10.1515/znb-2009-0319

Note
351
diterpene skeletons. Among the monoterpene starting
materials, probably the (+)- and (−)-forms of car-
vone are the most versatile. The best source of (R)-
(−)-carvone is spearmint oil, whereas the (S)-(+)-
enantiomer is a constituent of dill and caraway oils.
The cost of (R)-(−)-carvone is usually much lower
than that of the (+)-isomer, but both enantiomers of
carvone have been used as chirons in the synthesis of
diverse intermediates and natural compounds, princi-
pally terpenoids [1 – 4].
The range of pharmacological activity that has been
recorded for terpenes is remarkably wide. They are
found to function as anticonvulsant, antinociceptive,
sedative, and anxiolytic agents [5 – 11]. The range
of pharmacological effects of this family of natu-
ral products is apparently due to a variety of ac-
tion mechanisms. Terpene derivatives also have been
shown to have several effects on the central ner-
vous system (CNS), including antinociceptive [12, 13]
and sedative [14] activity. These facts led us to
Synthesis and Analgesic-like Effect
of (6R, 4S)-p-Mentha-1,8-dien-6-yl-
methylene-p-toluenesulfonamide
Damia˜o P. de Sousaa, Franklin F. F. No´ bregab,
Reinaldo N. de Almeidab, and Timothy J. Brocksomc
a Laborato´rio de Qu´ımica de Produtos Naturais e Sinte´ticos
Bioativos (LAPROBIO), Departamento de Fisiologia,
Universidade Federal de Sergipe,
CEP 49100-000 Sa˜o Cristo´va˜o, Sergipe, Brazil
b
Laborato´rio de Tecnologia Farmaceˆutica, Universidade
Federal da Para´ıba; Caixa Postal 5009, CEP 58051 – 970,
Joa˜o Pessoa, Para´ıba, Brazil
c Laborato´rio de Qu´ımica Bio-Orgaˆnica, Departamento de
Qu´ımica, Universidade Federal de Sa˜o Carlos,
Caixa Postal 676, 13565-905 Sa˜o Carlos, SP, Brazil
Reprint requests to Dr. Damia˜o P. de Sousa.
E-mail: damiao desousa@yahoo.com.br
Z. Naturforsch. 2009, 64b, 351 – 355;
received October 19, 2008
The synthesis of a monoterpene-based para-toluenesulf- verify in mice the psychopharmacological profile
onamide is reported starting from naturally occurring (R)-
of (6R,4S)-p-mentha-1,8-dien-6-yl-methylene-p-tolu-
(−)-carvone (1), by 1,2-addition of HCN followed by reduc-
enesulfonamide (4), an intermediate prepared from
tion with lithium aluminum hydride to afford the amino alco-
(R)-(−)-carvone (1) in our terpene total synthesis
hols 3a and 3b. Tosylation of this mixture with p-toluenesulf-
studies.
onyl chloride furnished sulfonamide 4 in 55 % overall yield.
Compound 4 was evaluated in behavior animal models to in-
vestigate its effects on the central nervous system. It showed
low toxicity and sedative action in mice, indicating it to be
psychoactive. It also caused a decrease in the spontaneous
motor activity of mice. This depressant effect was confirmed
in the acetic acid-induced writhing test, which demonstrated
a significant antinociceptive response more potent than 1.
The present results provide evidence that sulfonamide 4 has
analgesic-like psychopharmacological activity.
Results and Discussion
(R)-(−)-Carvone (1) is an excellent, cheap and com-
mercially available, chiral enantiopure starting mate-
rial for the synthesis of natural occurring compounds.
We have already reported the synthesis of a chiral
synthetic intermediate for perhydroazulene terpenoids,
starting from (R)-(−)-carvone (1) with initial 1,2-
addition of the nucleophile trimethylsilyl cyanide [3].
In the present paper we report the synthesis of a
p-toluenesulfonamide beginning with 1,4-addition of
cyanide to (R)-(−)-carvone (1), a reaction already
known to furnish selectively the adduct 2 in 90 % yield,
isolated by crystallization [15, 16].
Key words: p-Toluenesulfonamide, Carvone,
Monoterpene, Analgesic Activity,
Antinociceptive Activity
Introduction
Thus, the reaction of (R)-(−)-carvone (1) with
The total synthesis of naturally occurring terpenes potassium cyanide and acetic acid in ethanol under
has always been an important research area, with the the published conditions [16] produced the nitrile 2
use of simple, chiral, enantiopure monoterpenes as (Scheme 1). Reduction of compound 2 with LiAlH4
starting materials being a relevant option [1, 2]. These gave a 95 : 5 mixture of amino alcohols 3a and 3b in
monoterpene starting materials are readily available, 89 % yield. The constitution of the 3a/3b mixture was
frequently in both enantiomeric forms, and contain sig- confirmed by micro-analysis of the L-(+)-tartaric acid
nificant scaffolds of the desired mono-, sesqui-, and salts. Sulfonylation of these amino alcohols using p-
c
0932–0776 / 09 / 0300–0351 $ 06.00 ꢀ 2009 Verlag der Zeitschrift fu¨r Naturforschung, Tu¨bingen · http://znaturforsch.com
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352
Note
CN
HO
O
CH2NH2
O
KCN, EtOH, H2O
acetic acid, 0 oC, 90 %
LiAlH4, THF
r. t., 89 %
1
2
3a: a-OH
3b: -OH
β
O
S
CH2NH
O
Scheme 1. Synthesis of (6R, 4S)-p-
mentha-1,8-dien-6-yl-methylene-p-tolu-
enesulfonamide (4).
4
Fig. 1. Effect of sulfonamide 4 on spon-
taneous motoric activity in mice. n = 8;
* p < 0.05, ** p < 0.01 significantly dif-
ferent from control.
Fig. 2. Effect of sulfonamide 4, (R)-
(−)-carvone, morphine on acetic acid-
induced writhing in mice. n = 8; * p <
0.01 significantly different from control.
toluenesulfonyl chloride afforded the easily purified p- ioral screening were suggestive of a central depres-
toluenesulfonamide 4, in 69 % yield. TLC analysis of sant effect. The animals were found to show de-
the reaction product suggested that both aminoalco- creased locomotive activity and an increase in sedation
hols, 3a and 3b, had reacted. Noteworthy in this re- at 0.5 h and 1 h (Fig. 1) after administration of com-
action is the concomitant dehydration of the secondary pound 4 (60 mg kg−1) indicating that the sulfonamide
alcohol under the reaction conditions, which was not is psychoactive. In the evaluation of the antinocicep-
entirely unexpected with the temperature used.
tive profile, 4 (30, 60, 90 mg kg−1) significantly de-
creased the incidence of acetic acid-induced writhing
(Fig. 2). Compound 4 at 90 mg kg−1 produced a near-
maximal inhibition of the writhing response, similar
to 3 mg kg−1 of morphine. In comparison with the re-
sults found for unprotected terpenes, such as (R)-(−)-
carvone (1) [6, 9], compound 4 was more potent and
less toxic. The LD50 value reported for (R)-(−)-carv-
one is 426.6 (389.0– 478.6) mg kg−1 [6]. Fig. 2 shows
The pharmacological effects of the sulfonamide 4 on
the CNS were then evaluated. The toxicological evalu-
ation of compound 4 did not induce mortality up to a
dose of 1000 mg/kg in mice, and no significant toxic
effect was found during the observation period.
On the basis of animal observation, 4 (60 mg kg−1
)
did not affect the motoric coordination and mus-
cle tone. However, the parameters of the behav-
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Note
353
that a sulfonamide group in the structure of 4 enhances (1S,2S,4R,6S)-6-Aminomethyl-8-p-menthen-2-ol (3a) and
(1S,2R,4R,6S)-6-aminomethyl-8-p-menthen-2-ol (3b)
the pharmacological effect and reduces the toxicity.
A dry, nitrogen-purged, 100 mL three-necked flask with a
magnetic stirrer was charged with a suspension of lithium
aluminum hydride (1.189 g, 31.3 mmol) in anhydrous
tetrahydrofuran (76 mL). A solution of 8.0 g (45.19 mmol)
of nitrile 2 in tetrahydrofuran (12.5 mL) was added drop-
wise over 20 min to this suspension and the stirring con-
tinued for a further 1 h. Destruction of the excess lithium
aluminum hydride was effected by cautious dropwise ad-
dition of water (10 mL), followed by dropwise addition
of 15 % NaOH (10 mL), and subsequent addition of water
(30 mL). Stirring was continued until a granular white pre-
cipitate was formed. Filtration yielded a clear tetrahydrofu-
ran solution which was dried over anhydrous sodium sulfate.
The aminoalcohols 3a and 3b, in a 95 : 5 ratio according to
gas chromatographic analysis, were isolated as free amines
by removal of the tetrahydrofuran under reduced pressure
(7.341 g, 40.11 mmol, 89 % yield). The 3a/3b mixture (1.0 g)
was subjected to column chromatography over neutral alu-
mina, eluting with hexane-EtOAc (1 : 1) to afford aminoal-
cohol 3a (0.792 g, 79 % yield). Compound 3a: M. p. 72.8 –
Conclusions
The data reported in this paper demonstrate the psy-
chopharmacological activity of compound 4 in mice.
The study shows that 4 has a CNS-depressant effect
similar to some commonly used drugs. This effect of
the sulfonamide was not different from that observed
for other psychoactive terpenes [8, 9, 17]. However, 4
showed low toxicity, fewer side effects, and an im-
proved pharmacological profile. Our experimental re-
sults also suggest that by appropriate structural modifi-
cation of monoterpenesit should be possible to develop
novel analgesic drugs.
Experimental Section
General
GLC analyses were performed on a Shimadzu GC-17A
instrument equipped with a flame-ionization detector, us-
ing a DB-1 (30 m × 0.25 mm) glass column. Column chro-
matography was performed on silica gel 60 (70 – 230 mesh
ASTM Merck). Radial thin-layer chromatography was car-
ried out on a Chromatotron model 8924 (silica gel 60PF274
Merck). Melting points were determined on a Microqu´ımica
MQWAPF-301 apparatus and are uncorrected. Infrared spec-
tra were recorded with a Bomen Hartman & Braun MB-
Series spectrometer. 1H and 13C NMR spectra were recorded
at 200 and 50 MHz, respectively, on a Bruker ARX-200
spectrometer or at 400 and 100 MHz on a Bruker DRX-400
spectrometer, in CDCl3 with TMS as internal standard. The
mass spectra were recorded on a Micromass mass spectrom-
◦
73.5 C. – [α]3D0 = +7.0 (c = 1.0; CHCl3). – IR (film): ν =
3489, 2933, 1647, 1037, 993, 887 cm−1. – 1H NMR: δ =
4.73 (2H, s), 3.75 (1H, q, J = 3.2 Hz), 2.92 (2H, s), 2.84 (2H,
d, J = 3.4 Hz), 2.35 (1H, tt, J = 3.6 Hz; 11.6 Hz), 2.00 –
1.93 (1H, m), 1.92 – 1.89 (1H, m), 1.87 – 1.84 (1H, m), 1.74
(3H, s), 1.68 (1H, s), 1.65 – 1.59 (1H, m), 1.46 – 1.20 (2H,
m), 1.05 (3H, d, J = 6.8 Hz). – 13C NMR: δ = 149.9, 108.6,
68.9, 41.5, 39.3, 39.0, 37.6, 35.7, 34.3, 21.0, 14.9. – MS:
m/z = 184 [M+1]+.
Tartrate salts of amino alcohol 3a and 3b
A 50 mL flask with a magnetic stirrer was charged
eter Quattro LC, coupled with a chemical ionization source with distilled water (4.55 mL). L-(+)-Tartaric acid (1.025 g,
(reagent MeOH) under atmospheric pressure (APCI). Micro- 6.83 mmol) was added with stirring in one portion. The so-
analyses were performed on a Fisons EA 1108 CHNS-O ana- lution was stirred as 1.0 g (5.46 mmol) of the aminoalco-
lyzer, at the Chemistry Department, Universidade Federal de hols 3a – b was carefully added in one portion. A slurry was
Sa˜o Carlos. Solvents were purified prior to use: ethyl acetate formed initially, but complete dissolution was observed once
and hexane were refluxed over P2O5, distilled and stored the addition was complete. The solution was heated to 90 ◦C.
over molecular sieves; pyridine was stirred and refluxed over Glacial acetic acid (0.75 mL) was then added in one por-
KOH, distilled and stored over KOH. Tetrahydrofuran (THF) tion. The product began to precipitate during the addition and
was distilled from sodium under nitrogen.
continued to precipitate while the reaction mixture was al-
lowed to cool from 90 ◦C to 5 ◦C, with stirring, over 3 h. The
◦
temperature was maintained at 5 C for an additional hour,
(−)-(1R,2R,5R)-2-Methyl-5-(1’-methylvinyl)-3-oxocyclo-
hexanecarbonitrile (2)
and the product was isolated by filtration. The filter cake was
washed wi◦th cold (5 ◦C) water (5 mL). The product was dried
Reaction of (R)-(−)-carvone (1), (12.500 g), with hy- at 40 – 45 C under reduced pressure to give the aminoalco-
drogen cyanide gave nitrile 2 in 90 % yield, m. p. 91.5 – hols 3a, b as tartrate salts (1.456 g, 4.37 mmol, 80 % yield)
92.2 ◦C. – [α]3D0 = −3.8 (c = 1.20 in CHCl3) (lit. [16]: as a white amorphous solid. – Anal. for C15H27NO7:
◦
93 – 94 C. – [α]1D8 = −4.0 (c = 1.04 in CHCl3). – 1H and calcd. C 54.04, H 8.16, N 4.20; found C 54.10, H 8.14,
13C NMR data were in agreement with the literature [16].
N 4.21.
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354
Note
(6R, 4S)-p-Mentha-1,8-dien-6-yl-methylene-p-toluene-
Statistical analysis
sulfonamide (4)
The statistical analysis was performed using analysis of
variance, followed by Dunnet’s test. A probability level
of 0.05 was regarded as significant.
To a stirred solution of the aminoalcohols (3a, b) (0.300 g,
1.63 mmol) in dry pyridine (0.8 mL, 9.78 mmol) under
a nitrogen atmosphere was added p-toluenesulfonyl chlo-
ride (0.622 g, 3.26 mmol) at r. t. The solution was heated
to 120 ◦C for 3 h, and then cooled to r. t. After addition
of water (10 mL) the reaction mixture was extracted with
ethyl acetate, washed with saturated copper sulfate, water,
sodium bicarbonate, dried over anhydrous sodium sulfate
and concentrated under reduced pressure. The residue was
purified by radial chromatography (90 : 10 hexane-EtOAc)
on silica gel to yield the pure product 4 (0.375 g, 1.12 mmol,
69 % yield). – [α]D29 = +100.8 (c = 2.1; C2H5OH). – IR
(film): ν = 3520, 3283, 2933, 1645, 1325, 887, 660 cm−1. –
1H NMR: δ = 7.75 (2H, d, J = 8.1 Hz), 7.30 (2H, d, J =
8.1 Hz), 5.52 – 5.48 (1H, m), 4.70 (1H, t, J = 1.8 Hz),
4.64 – 4.62 (1H, m), 4.39 (1H, t, J = 6.4 Hz), 3.17 – 3.06
(1H, m), 2.92 – 2.79 (1H, m), 2.42 (3H, s), 2.17 – 2.10
(1H, m), 2.09 – 2.05 (1H, m), 2.04 – 1.87 (2H, m), 1.68
(3H, s), 1.63 – 1.56 (2H, m), 1.59 (3H, s). – 13C NMR:
δ = 149.0, 143.2, 136.8, 132.2, 129.6, 127.0, 124.7, 108.7,
44.8, 39.1, 35.6, 30.6, 29.7, 21.7, 21.4, 20.7. – MS: m/z =
320 [M+1]+. Anal. for C18H25NO2S: calcd. C 67.68,
H 7.89, N 4.38, S 10.04; found C 67.61, H 7.91, N 4.37,
S 10.06.
Acute toxicity and behavioral effects
Different doses of 4 were administered intraperitoneally
(i. p.) to groups of mice (n = 10), and mortality was recorded
for 48 h for the determination of LD50 [18]. The behavioral
screening of the mice was performed at 0.5 and 1 h after
injection of 4 (60 mg kg−1, i. p.) [19].
Locomotor activity
Mice were divided into four groups of eight each. Vehicle
(control) and 4 (60 mg/kg, i. p.) were injected. The sponta-
neous motor activity of the animals was assessed in an ac-
tivity cage (controller model 7441 and Grid-Floor Detecting
Arrangement Cage model 7432; Ugo Basile, Italy) at 0.5, 1,
and 2 h after administration [20].
Acetic acid-induced writhing
The mice were divided into five groups (n = 8). The
first group was pretreated with saline 0.9 % (control). Com-
pound 4 (30, 60, and 90 mg kg−1 i. p.) (R)-(−)-carvone 1
(90 mg/kg, i. p.) and morphine (3 mg kg−1 i. p.) were ad-
ministered. After 30 min an acetic acid solution (0.8 %;
0.1 mL/10 g i. p.) was injected. After a further 10 min, the
number of constrictions was recorded for 10 min [17, 21].
Animals
Male Swiss mice (28 – 34 g) were obtained from the
research animal facility of the Laborato´rio de Tecnologia
Farmaceˆutica. The animals were maintained at constant
r. t. (26
1
◦C) and on a 12/12-h light-dark cycle (light
Acknowledgements
from 06:00 to 18:00), with free access to food and water. All
behavioral observations were conducted between 08:00 and
17:00 h and carried out in accordance with ethical committee
approvals.
We thank FAPESP, CNPq and CAPES for financial sup-
port. The (R)-(−)-carvone was generously donated by Fir-
menich S.A.
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