Forty amides, formamidines and trifluoromethylsulfonylamides bearing on the nitrogen a cyclohexyl residue, eventually 2-substituted, were prepared and tested for analgesic activity against a chemical stimulus. Good activity was exhibited by amides 9, 11 and 28, by formamidine 34, as well as by triflyamide 40. Eleven additional compounds exhibited a moderate activity

Boatto, Gianpiero

Cerri, Riccardo

Nicolai, Marco

Palomba, Michele Francesco Luigi

Pau, Amedeo

Sparatore, Fabio

Varoni, Maria Vittoria

English

UnissResearch

, 
IL FARMACO, 48 (9),1291-1299; 1993 
AM IDES AND FORMAMIDINES WITH 
ANTINOCICEPTIVE ACTIVITY (NOTE II) 
AMEDEO PAU - GIANPIERO BOATTO - RICCARDO CERRI (*) 
MICHELE PALOMBA - MARCO NICOLAI 
ISTITUTO Dl ANALlTICA FARMACEUTICA - UNIVERSITA Dl SAS SARI 
VIA MURONI 23, 07100 SASSARI - ITALY 
FABIO SPARATORE 
ISTITUTO Dl SCIENCE FARMACEUTICHE - UNIVERSITA Dl GENOVA 
V,LE BENEDETfO XV 3,16132 GENOVA - ITALY 
MARIA VITTORIA V ARONI 
CATTEDRA Dl TOSSICOLOGIA - FACOLTA Dl MEDICINA VETERINARIA - UNIVERSITA DJ SASSARI 
VIA VIENNA 2,07100 SASSARI - ITALY 
SUMMARY Forty amides, jormamidines and trijluoromethylsu/jonylamides 
bearing on the nitrogen a cyC/ohexyl residue, eventually 2-substituted, were prepared 
and tested jor analgesic activity against a chemical stimulus. Good activity was ex-
hibited by amides 9, 11 and 28, by jormamidine 34, as well as by trijlylamide 40. 
Eleven additional compounds exhibited a moderate activity. 
RI ASS UNTO Si riporta la sintesi di numerosi derivati ammidici, jormam-
midinici e trijluorometilso/jonammidici, recanti sull'azoto un residuo cic/oesilico, 
eventualmente 2-sostituito, che sono stati saggiati per la ricerca dell'attivita analge-
sica contro stimolo chimico. Buona attivita e stata mostrata dalle ammidi, 9, 11 e 
28, dalla jormammidina 34 e dalla trijlilammide 40. Aftri undici composti hanno 
mostrato moderata attivita. 
, Introduction 
During our researches on new structures endowed with antiinflamma-
tory and/or analgesic activities (l-4), the peripheral antinociceptive activity 
of some N-substituted cyclopentylamine derivatives was revealed. 
Such activity was strongly influenced by the nature of the substituents 
on the nitrogen and on the cyclopentane ring, so that on changing the for-
mer the structural requirements of the latter for the best activity changed too. 
(*) To whom correspondence should be addressed. 
, 
.' 
1292 A. PAU et al. 
In an attempt to further support those observations some sets of cyclo-
hexylamine derivatives were prepared and screened for antinociceptive ac-
tivity against phenylquinone induced writhings. 
The prepared compounds are listed in Scheme 1. 
N o~ 
o 
( I ) 
la • 1 
Ib = 2 
le = 3 
1d-4 
le = 5 
Cl 
NH ..... J 
o 
( V ) 
Va " 21 
Vb = 22 
Vc = 23 
Vd· 24 
Ve = 25 
Sd1eUit 1 
JR' 
./"' ..... .,-CI 
o 
( I ) 
IIa " 11 
III : 1 
lie = 8 
lid - 9 
lie = 10 
IJR' 
o 
o 
( II ) 
!la • 11 
Ill> = 12 
lie = 13 
lid = 14 
lie = 15 
OCH:, 
.. 
( VI ) 
Via = 28 
VIb • 27 
Vie " 28 
VId = 29 
Vie .. 30 
a=R'=H 
b = R' = CH3 
C = R' = t-(C4H9) 
d = R' = CH2CSH5 
e=R'=OH 
J R' 
( VII ) 
VIIa = 31 
VIIb • 32 
Vile" 33 
VIId = 34 
Vile· 35 
~/,R' 
NH 
o 
( w ) 
Na ,. 111 
I\tb '= 11 
Ne • 18 
IVd = 19 
Ne = 20 
( VII ) 
Vlla '" 38 
Vllb • 37 
Vile = 38 
VIId • 39 
Vile .. 40 
• 
• 
Amides and formamidines with anti nociceptive activity (II) 1293 
Chemistry 
The preparation of ami des 1-30 was effected by stirring the benzene 
solution of the suitable amino compound with an excess of appropriate acyl 
halide, in the presence of triethylamine at room temperature. The formami-
dines 31-35 and the trifluoromethylsulfonylamides 36-40 were prepared, as 
already described (1-4), by reacting the 2-substituted cyclohexylamine with 
dimethylformamide dimethyl acetal and trifluoromethylsulfonic anhydride 
respectively. 
The characteristics of compounds 1-40 are collected in Table I. 
. The structure of the obtained compounds was generally supported by 
elemental analysis and NMR spectra (Table 11); in the case of formamidines 
and trifluoromethylsulfonylamides by GC-MS spectra (Table Ill). 
Of the required starting amines cyclohexylamine and 2-
methylcyclohexylamine were commercial products; 2-tert-butyl- and 2-
benzylcyclohexylamine were prepared reducing the oximes of 2-tert-butyl-
and 2-benzyl-cyclohexanone, respectively with sodium and absolute ethanol 
(5,6). 2-tert-butylcyclohexanone was commercially available, while 2-
benzylcyclohexanone was prepared through the alkylation (7) of 1-
pyrrolidino-l-cyclohexene (8). The oximes were prepared according to (9). 
At last (± )trans-2-aminocyclohexanol was prepared through ammonolysis 
of cyclohexene oxide (10,11). 
Chemical experimental section 
Melting points were determined using a Kofler apparatus and were not corrected. 
Elemental analyses (C,H,N) were performed at the Micro analytical Laborato-
ry of the Department of Pharmaceutical Sciences, Padua University, and the ana-
lytical results for the elements indicated were within ± 0.3070 of the calculated values. 
'H-NMR spectra were taken on a Varian VXR 300 (at the CNR laboratories, 
Sassari), using CDClJ or DMSO as solvents with TMS as internal standard. Mass 
spectra (31-40) were obtained on a HP 5970A apparatus, using a capillary column 
HPl of 25m length; programmed temperature was from l50°C to 300°C (lO°C/min), 
detector temp. was 300°C and the carrier gas was Helium of 99.9998% purity, at 
10 psi pressure. 
N-acyl- or N-aroylcyc!ohexylamides 2 monosubstituted (1-30) 
A stoichiometric quantity of the required acyl halide, increased of 25%, dis-
solved in 10-15 ml of benzene, was dropped into a solution of 5 mmoles of amine 
and 6.5 mmoles of TEA in 30 ml of benzene. The mixture was stirred at room tem-
perature for a time varying from 30 minutes to 2 hours (Table I); then the reaction 
mixture was filtered and the benzene solution was shaken with a solution of 
NaHCO) (5%) and subsequently with water. After benzene removal, pure com-
pounds were obtained generally by crystallization of the residue from alcohol or 
hydroalcoholic mixtures, whereas in some cases it was necessary a chromatography 
on silica gel (Table I). 
• 
1294 A. PAU et al. 
TABLE I 
Characteristics oJ compounds 1-40 
eOlllp. Furuwia M.W ,<\mlyse; Ill.p. o>r Yield Reaction Method ,)f 
b.p.(ndn Hg) 0/ 0 • purification tUlI" 
"'C 
1 Cl oH I ,.NOz 185 CHN 58-59 36 2h 
, • A 
2 Cl I H21 NO, 199 CHN 100 i l 40 2h fl 
• C I4H2)N02 241 CHN 48-49 30 211 A 
" 
.. C I1 H2SNO:: 275 CHN 73-75 40 2h A 
S C lOH19NO, 201 CHN 120-130il 4~ 2h H 
6 C13H16NOCI 2.38 CHN 179-180 78 30' A 
"' C14H1SNOCI 252 CHN 181-182 72 Ih A , 
8 C 17H24NOCI 294 CHN 210-211 75 Ih A 
9 C20H2ZNOCI 328 eHN 173-174 ~~ -- Ib A 
to C 13H I6N02CI 253 CHN ]73-]75 62 Ih A 
J] C16H23N04 293 eRN 180-181 75 30' \ . 
12 Cl ;"25N04 307 CHN 196-198 40 Ih ,.\ 
13 C20H31NO~ 249 CHN 22~-226 44 Ih A 
14 C23H2~04 383 CRN 208-210 47 Ih A 
IS C16H2}NO~ 309 eHN 174-175 51 Ih A 
16 CI5Hl~O 229 CHN 180-181 43 ih (' 
. 
17 C 16Hz1 NO 243 (,HN 162-164 50 Ih A 
18 Cl~27NO 285 CHN 218-219 60 Ih A 
19 C22H2SNO 319 CHN 191-192 46 III A 
20 CI5Hl~02 245 CHN 122-124 40 Ih A 
21 C 1sH 1SNOCI 264 CRN 203-204 75 Ib A 
22 C I6H2()NOCI 278 CRN 195-196 60 Ih A 
23 C19H16NOCI 320 CRN 184-186 30 III A 
24 Cn Hz4NOCI 354 CHN 180-182 50 III A 
2S C IsH I sN02CI 280 CHN 195-197 40 Ih D 
26 CISH25N04 319 CHN 205-206 57 III C 
2"' C I9H27N04 333 CHN 208-210 59 Ib C 
28 C22H))N04 375 CHN 74-75 60 Ih A 
29 C 25HjlN04 409 CHN 186-188 45 Ib J) 
30 C!SH25N05 335 CHN 168-170 45 III D 
• (~onbnlle 'I 
. , 
A) ' . "'0 (ethanol), D) (silica gel column, elum ; benzene - acet..'lI\ 
8/2 ). C) Di>1.illatim under V8('\Jum (bulb to bulb). D) Crylll.allizatioo (ethanol-Wafer I l l). 
Amides and formamidines with antinociceptive activity (11) 1295 
continuation TABLE I 
Comp. FOiiUUIa M.W Analyses m.p. or Yield Reaction Me1hodof 
b.p.(lmn H8) % , i.ne purification QC 
64 B 
32 CIOHwN2 GC-MS 80-90n 70 Ih B 
33 CI3H26N2 GC-MS 95-100/3 65 Ih B 
34 CI6H24N2 GC-MS 135-145/5 34 Ih B 
3!! C~18N20 GC-MS 117-119 52 Ih B 
36 C)HI2N02SF3 231 GC-MS 64-65 37 Ih D 
37 CSHJ 4N02SF J 245 GC-MS 73-74 24 lh D 
38 CJIH20NOJSF) GC-MS 96-97 • 38 Ih D 
39 CI4HISN02SF3 321 GC-MS 90-92 26 Ih D 
40 C1H12NO)SF3 GC-MS 96-98 50 Ih D 
A) Cryj/lllljzmiOll (ethanol). B) Chromatography (silica se! oo)umn, eluem : benune - aceron 
8/2 ). C) DistiUatioollll&r vacuum (bulb to bulb). D) 111). 
TABLE Il 
'H-NMR spectra collected jor molecules with similar structures 
COlD,. 
.5 ..... 
0.9-1(m, CH3t-butyl); 1.1-1.3(1. CH3);1-2(m, CH2); 2.5-3.7(11. CH2"}; 
1-5 3.7-3.8(8, OCH2CO); 6.2-7.4{m, aromatics). 
6-10 
0.98-O.9S(d, CH3); 1.2-2.2(01, CH2); 3.4(8, OH for the product 10); 4.S(01,CH); 
S.8(s, NH); 7.2-7.7(m, aromalico). 
0.95-0.99(01, CH3); 1-3(m, CH2); 3.8-3.9(., OCH3); 4.7(8, OH for the product 15); 
11-15 4-4.S(m, CH); S.9-6.1(s, NH); 6.9-7.3(m, aromatics) . 
• 
0.94-0.96(m, CH]); 1.1-2(01, CH2); 4.6(s, OH for the product 20); 6.4-6.8(d, CH=CH); 
16-20 5.5-S.9(8, NH); 7-7.S(m, aromatics). 
0 .94-O.96{O1, CH3); 1.1-2.l(m, CH2); 3.7-4.S(m, CH); 4.7(s, OH for the product 25); 
21 -25 5.5-5.9(1, NH); 6.2-6.7(d, CH=CH); 7-7.7(01, 
0.8-1.2(m, CH3); 0.9-2(m, CH2); 3.7-3.8(s, OCH3); 4.7(s, OH for the product 30); 
26-30 5.5-6(8, NH); 6-6.S(m, CH=CH); 6.7-7.8(m, aromatics). 
Solver'" used CDCI3; a mixture CDClrDMSO (1: 1) for the product 21-25. 
1296 A. PAU et al. 
TABLE III 
GC-MASS spectra of compounds 31-40 
tr 
Products (min) Most Impor1ant (M'"/e) 
31 8.76 154: (M+); 97:( N-C6Hll); 57: [CH-N(CH3n J; 44:[ N-(CH3n J 
168 :( M~ ;97: (2 methylcycloexyle) ;71 :[ N=CH-N(CH3nJ ; 
32 9.08 57 :[ CH-N(CH3n ]; 44 :[ N-(CH3n ] 
. 
33 9.94 
210 : (M+) ; 84:[ CH2-CH2-c(CH3h ]; 57 : [CH-N(CH3n] ; 
44 :[N-(CH3n ] 
34 14.69 
244 : (M~ ; 111 :[ CH2=CH-CH-N=CH-N(CH3n]; 
91 :(CH2-C6HS ~ 57 :[ CH-N(CH3n]; 44:[ N-(CH3)21 
35 3.42 
170 : (~; 99 : (C6HII0H); 71 :[ N=CH-N(CH3n] ; 
57 :[ CH-N(CH3hl ; 44 :[ N-(CH3n 1 
36 5,69 
231 : (M+j; 188: (CH2=CH-CH2-NHS02CF3); 83 : (cyclobexyle); 
69 :( CF3); 64 :( S02 ); 55 :( CH2=CH-CH-NH) 
245 : (M+) ; 202 :( CH3-CH=CH-NHS02CF3); 96:(cyclobexylallline ); 
37 5.99 69 :( CF3 ); 64 :( S02 ); 55 : (CH2=CH-CH-NH) 
. 
• 287 : (M~ ; 57: [C(CH3h] ; 55 : (CH2=CH-CH-NH); 
38 4.06 41 : ( CH2-CH=CH2) 
39 9.13 
321 : (M~; 188:( CH2=CH-CH2-NHS02CF3); 91 :( CH2-C6HS); 
69: (CF3); 64 :( S02); 41 :( CHrCH=CH2) 
40 3.19 
247: (M+); 114 :( NH-C6Hl00H); 97 : (NH-C6HIO); 69: (CF3 ); 
64 :( S02 ); 57 : (CH2-CH=CHOH); 55 :(CH2=CH-CH-NH) 
N,N-Dimethyl-N'-cyclohexyljormamidines 2 monosubstituted (31-35) 
A stoichiometric quantity plus a 200/0 excess of dimethylformamide dimethylace-
tal was dropped rapidly into a boiling solution of 5 mmoles of amine in 15 ml of 
benzene and the mixture was further refluxed for 0.5 to 1 hour. The solvent was 
removed under reduced pressure and the crude oils were distilled under vacuum (Table 
I). 
(N- Trif/uoromethylsuljonyl)cyclohexylamides 2 monosubstituted (36-40) 
A solution of 5 mmoles of amine in 30 ml of dichloromethane was cooled, un-
der stirring, with a suitable immersion cooler (SEDAS DF 100). When the solution's 
temperature reached - 30°C a stoichiometric quantity of triethylamine was added 
and when the temperature reached - 80°C the stoichiometric quantity plus a 10% 
excess of trifluoromethylsulfonic anhydride was slowly dropped. Finally the tem-
perature was allowed to rise slowly to room value and the solvent was removed un-
der reduced pressure. The crude oils were distilled under vacuum (Table I) leaving 
back a substantial amount of tar. 
Amides and formamidines with antinociceptive activity (11) 
Pharmacology 
Materials and methods 
1297 
For the detection of anti nociceptive properties, male Swiss mice (Nossan) were 
used. The animals, weighing 18-22 g, were divided in groups of ten and stabulated 
at constant temperature (21 ± 1°C) and humidity (60 ± 5OJo) with alternating 12 hour 
periods of light and dark. 
The animals were fed with Nossan feed in pellets and aqua Jontis ad libitum. 
Antinociceptive activity against a chemical stimulus (peripheral analgesia) 
This type of analgesia was evaluated through the inhibition of writhings induced 
by the i.p. injection of phenylquinone (2 mg/kg as a 0.02% solution in 5% ethanol). 
The test compounds were administered per os at the dose of 0.167 mmollkg 
suspended in a 10% arabic gum solution. 
The animals were dosed 60 minutes before the phenylquinone injection. 
For every point three groups of 10 mice each were used. For each experiment 
two groups (one at the beginning and one at the end) of control animals were em-
ployed receiving only the quinone i.p. and the arabic gum per os. 
After the injection of phenylquinone the animals were introduced into a glass 
cylinder and the writhings were recorded for 20 minutes starting from the fifth minute 
after injection. 
The results are expressed as a percent variation in writhings number compared 
to that of the control animals (Table IV). 
In order to detect any gross overall effect of the absorption-elimination rate 
and/or of metabolic activation, the anti nociceptive activity of the three most active 
compounds (11,28,34) was measured 15,60 and 120 minutes after the drug (0.167 
mmoles/ kg; p.o.) administration (Table V). 
Results and Discussion 
The results of the writhing test on 31 of the 40 compounds described 
are shown in Tables IV and V. Nine compounds were not tested due to the 
scarcety of material. 
Of the tested compounds three (11,28,34) exhibited a good activity with 
writhing inhibition going from 56 to 65%; other thirteen compounds showed 
a moderate activity with writhing inhibition ranging between 25 and 440/0. 
The r~maining compounds were poorly active or completely inactive, but 
only one compound was endowed with hyperalgesic activity increasing the 
writhings for 28.7%. These results already indicate a clear difference be-
tween these substances and the cyclopentylderivatives previously studied (4), 
only a few of which were active as analgetics and many were characterized 
by hyperalgesic activity. Moreover mortality was never observed at the test-
ed dose (0.167 mmoles/kg), thus the triflykyclohexylamides differed strik-
ingly from the corresponding cyclopentylderivatives previously studied. 
Although active compounds were found in all the groups of cyclohex-
ylamine derivatives now considered, the active compounds were mainly der-
1298 A. PAU et al. 
TABLE IV 
Antinociceptive activity: phenylquinone writhing test (aj 
Comp. I 3 4 6 7 8 9 11 
Var. %(b) -6.0 -29.4 -31.3 -4.5 +8.0 -15.3 - 43 .S - 58.6 
Comp: 12 13 14 15 17 18 19 • 21 
Var. % -? - 6 •. :> . -14.4 -28.5 -32.5 -8.5 -29.1 -24.6 -12.4 
Comp. 22 24 26 27 28 30 31 32 
Var. % -5.4 -9.1 +'7, , .- -6.5 -64.7 -8.3 -~6 . 1 +28.7 
-t 
Comp. 33 34 35 37 38 39 40 
Var.% -31.9 -55.7 -26.9 -29.6 +3.4 -13.7 -40.0 
\a) Dose; 0.167 mmoles!kg 
tb) Var. % : percent variation ofwrithings during 20 mill, compared with controlllllimals 
(inhibition - , increase + ). Reading was started 5 min. after phenylquinone injection; the irri-
tani was ultroduced 60 min. after compounds administration. 
TABLE V 
Wrighings inhibition at different timefrom drug administration (0.167 mmolesl kgj 
% Inhibition 
f"'=:: tarn. 
t:om . 15' 60' 120' 
J 1 +1.9 -58.6 -33.5 
214 -11.2 -64.7 -31.5 
• 
34 -63.0 -SS.7 .2,6 
Amides and formamidines with anti nociceptive activity (1I) 1299 
ived from 2-benzyl- and 2-tert-butylcyclohexylamine. For what concerns the 
acyl moiety, the activity was mainly bound to the trimethoxybenzoic and 
the dimethylformamidinic residues; however, apart from the 4-
chlorocinnamoyl residue, the remaining acyl or aroyl residues gave some 
active compounds. 
It should be observed once more that on changing the substituents on 
the alicyclic ring the structural requirements for the acyl or aroyl residue 
to give the best activity were also changing, so that the overall correlation 
between structure or physical properties and activity resulted rather elusive. 
Good activity was found for the highly lipophilic N-(3,4,5-
trimethoxycinnamoyl)-2-benzylcyclohexylamine (28) and for the rather 
hydrophilic N -(triflyl)-2-hydroxycyclohexylamine (40). 
Finally, on the three most active compounds (11,28,34) the temporal 
variation of activity was investigated (Table V). 
Compounds 11 and 28 exhibited the maximal activity after 60 minutes 
from administration but this activity was slowly decreasing, remaining 
moderate after 2 hours. 
On the contrary the amidine 34 showed a rapid onset of activity being 
highly active already after 15 minutes; such activity was still present after 
one hour but ceased completely during the next hour. 
Acknowledgement 
The financial support from the M. U.R.S. T. is gratefully acknowledged. 
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•• 5) SCHOPF C., BOETTCHER E., Ann., 448, 7; 1926. 
6) LYCAN W.H., PUNTAMBEKER S.V., MARVEL C.S., Organic Syntheses, Vol. II, Call, 
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Received June 2, 1993; accepted June 21, 1993. 


DEMONTlS M.P., submitted for pubblication of II Farmaco .

Amides and formamidines with antinociceptive activity: note II

Amides and formamidines with antinociceptive activity: note II

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