Synthesis and Vasodilator Activity of New Piperazine Derivatives G. I,. REGNIER,R. J. CANEVARI, Chemical Research Division
11. J . IAUBIE, AND J. c. L E DOUAREC Pharmacologiral Rpsearch Diiiision, Scienw C’nion et Associes, Groupe de Rechwches des Lnhoratozres Servier, 9 2 Swesnes, Franre Rewived M a y 14, 1968 Thirty-seven 1,4-disubstitiited piperazines have been prepared in whirh the 1 sithatititents are benzyl or phenylalkyl or its mono- or polyalkoxy, alkylenedioxy, or alkoxyhydroxy derivatives, and the 4 sitbstiti~eiitsare pyrimidyl and its srtbstitiited derivatives, quinazoliiiyl or triazinyl. Some derivat ives were foiind to have potent vasodilating properties in anesthetized rabbits. Furthermore some of them exhibit analgetic and aiitii~iflammatory properties. A structure-activity relationship study was carried out.
S(~HEME I
A considerable body of literature is recorded on the biological effects of compounds containing the piperazine moiety. I n the field of the 4-substituted l-aralkylpiperazines, hypotensive and vasodilator effects have been reported. )lore recently, we have described2 the potent coronary vasodilator properties of a piperonylpiperazine derivative (I). This observation stim-
\
< l a - C H I \ I I \ CA Hic6Hr,)2
I
ulated our interest in the preparation and testing of other piperonylpiperazine derivatives and led us to synthesize 1, which was found to have significant peripheral vasodilator properties.
c1
W
tlomethane according t o the method of Bredereck, et aL4 The 1-substituted 3-(2-s-triazinyl)piperazine was then ( ) tl t air led. Structure-Activity Relationships. Vasodilating Action (Table IV).-Half of the compounds were inactive ah vasodilator*; only 29 mas analgetic and antiitiflanimatury. The active structure seems to be -tr.ictlv related t o the starting compound (1). To rctain :I high activit? , the following changes could t w ni:itle. (a) The methylenedioxy group could only I)r replaced ti!. cthylenedioxy (29), OH- or OCHI(4) H
Bredereck, F Effenberger, 1 IIofmann and 11 H a ~ e k l w r ! t
Ciiern Intern Ed C / o 1 , 2 , 6 5 5 (1967)
aubstituted benzyl derivatives being far less :mtivc (30-34). Likewise the lengthening of the distanct. between the piperazine nitrogen and the phenyl ring, or the deletion of methylene groups, tlecreased the activity (35-40). (b) The piperazine moiety could be substituted by CH,, the most favorable position being 2 (24). Quaternization or exchange of the piperazine moiety into homopiperazine or N,S'dimethylethyleriediamine abolished the activity (2628). (c) Among the substituents of the pyrimidine moiety. tidy 4-CH3 and 4-NH2 (10, 13) were the most favorable. If the pyrimidine ring is linked in the 1 position to the piperazine K-atom (3), the activity is
1153
VASODILATORY PIPERAZIXE DERIVATIVES
November 1908
Yield crystd,
C
NO.
Crystno solvent
70
Method
29 3,4-[O(CH2)20]CsH,CHz A 30 3,4-(CH30)2CeHsCH? A 31 2,4-(CH30)zC,H,CH, C 32 ~,~,~-(CH,O)~CF,H~CHZ A 33 3-(CH,O)-4-OHCsH,CHz C 34 3,4-(OH)zCeH,CHz C 35 2-CHzOCeH4 A 36 3-CH3OCeH5 A 37 4-CH30CsH4 A 38 3,4-(OCH,O)C,H,(CH,)z B 39 3,4-(OCH2O)CeH,O(CH,)z B 40 (C&)&H A a - c See footnotes a, b, and e, respectively, in Table I.
45 75. .? 3 7 . ,j 60
AE AP AE AP
55
AM
49 39 65 76 31 58 26
A4 98 AE AM
AE
MP, of amine or salt
220-226 101 2 10-2 14 105 183-188 207-2 12 73
77-78
AE AE E 98
108-110 233-233 102 170
No.
Toxicity, LD60, m g / k ip (mice)
23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
-50 830 -600 -300 -75 -125 720 406 207 210 -400 -400 482 178 248 400 ~ 1 0 0 P0O 269
TABLE I\' Toxicity,
LDaa, NO.
m n / k ip (mice)
690.3 1 244 3 622 4 498 5 201 7 >loo0 8 393 9 -400 10 -800 11 576 12 195 13 51.6 14 130 15 -150 16 -750 17 432 18 -200 20 -400 21 >500 22 a Per cent increase in blood flow of the 73, = 25-50. d = duration of action
-
+
Vasodilating action"
++++ d + ++ 0 ++ 0 ++ +++ d 0 0
++++ ++++ ++ d 0 0 0 Vasoconstrictive effect
+++ ++++ d
femoral artery relative to control values: 3 10 min.
lost, unless this ring is 4-substituted by S H 2 (14). Likewise, replacement of the pyrimidine by a tr'azine group led to an inactive substance (18). The activity was unexpectedly almost recovered by two additional OCH3 substituents in the 4 and 6 positions (21). At best, the pyrimidine ring could be replaced by quinazoline linked in the 2 or 4 position without losing activity (22, 23). Other cardiovascular tests showed that all these vasodilating substances are inactive in the nictitating membrane test in the cat and reserpine hypertension test in pithed rats. The lack of such properties indicates that these products do not interfere with sympathetic transmission and catecholamine stores. The most active compound, 1-(2-pyrimidyl)-4-piperonlypiperazine (1), was tested in anesthetized dogs. Slow intravenous perfusion (10 pg/kg/min during 10 min) did not affect arterial pressure nor cardiac frequency and output. The venous and arterial femoral output were raised considerably (>1 0 0 ~ o ) and this increase lasted longer than 60 min. The same effects were observed by intraduodenal administration
>
Vasodilating actionu
++++ d +++ ++ +0 0
++++ d
+0 0 0
++ + 0 +0 Insoluble in water
++
++++ = 100, +++ = 75-100, + + = 50-
of 0.5-1 mg/kg of 1. This compound, as all the others, had no action on the coronary, cerebral, and renal circulations. Analgetic and Antiinflammatory Actions.-Two compounds (29, 38) were as active as aminopyrine at 100 mg/kg and 50 mg/kg ip, respectively, in the modified hot plate test. Only three compounds (13,38,39)were equipotent to phenylbutazone and four (1, 7, 12, 30) exhibited a mild activity in the kaolin paw edema test. Experimental Section5 Pharmacological Methods. (a) Vasodilating Action (Table IV).-Drugs were studied for possible vasodilating activity in anesthetized rabbits. The femoral artery was perfused a t constant pressure. The substances were administered by the intravenous route a t a dosage range of 1-5 mg/kg. The changes in flow of the femoral artery reflected the changes in the vascular ( 5 ) All melting and boiling points are not corrected. Where analyses are indicated only by symbols of t h e elements or functions, analytical results obtained for those elements or functions were within +0.4Yo of t h e theoretical values.
Xovember 1968
111
rlCETYLENTC ~ A R B A I T A T E S .
in 75 ml of boiling HI0 and the solution \vas filtered and neutralized a t pH 8 with K2C03. The crystalline base was collected 011 a filter, washed (HIO), and recrystallized from 60 ml of DMF. On cooling to O", the crystals were filtered off, washed (cold MeOH), and dried in a vacuum desiccator, yielding 9.8 g (69.5y0) of product, mp 214'. Method F. 1-(3,4-MethylenedioxybenzyI)-4-guanidinopiperazine sulfate.--A mixture of 55 g (0.25 mole) of l-piperonylpiperazine and 35.3 g (0.254 mole) of S-methylisothiuronium sulfate in 250 ml of HlO v a s heated to tioiling for G hr. On cooling to room temperature overnight, the crystallized product was cdlrsrtcd on a filter and recrystallized from 60% 2-PrOH yielding 40 g (63( ) of neiitral siilfate, mp 260-262'. Anal. ( C l ~ I I & & ~ ~ 0 ,5112S04)C, € I , N, S. 1-(3,4-Methylenedioxybenzy1)-4-(2-o-triazinyl)piperazine Hydrochloride (l).-.l mixture of 35.6 g (0.114 mole) of the above
1155
sulfate and 150 ml of IIRIF was treated with 3 2 ml (0.114 mole) of concentrated H2SOa and 22 g (0.154 mole) of triformamidomethane.26 The mixture was then heated for 5 hr a t 150". There was incomplete dissolution. After cooling a t lo", the iiisoluble crystals were filtered off arid the solution was concentrated zn vacuo. The oily residue was taken up in 50 ml of 4 NaOH and extracted several times into 150 ml of CHCl,. After washing arid drying (KBCOI),the solvent was evaporated to dryness and the residiie weighing 29 g was dissolved in 75 ml of ailhydrous EtOII. The solution was saturated with HC1 gas and after cooling 19.5 g of crystals of salt was obtained; they were recrystalliLed fiom 32.5 ml of 9gC, 5IeOIT to give 14.2 g 133 uf white prodiict, mp 207-21 1'. (26) H Rredereck, R G o m p p e r , H Reiiipfer, 1% 1ilee111.and 1 C Heck, , 92, 329 (1959)
Bel
Acetylenic Carbamates. 111. The N-Cycloaliphatic Derivatives H. D. DILLARII, G. A. POORE, S. R. EASTOX, 11, J . SWEESEY,and IT'. K. GIBSOA The Lilly Research Laboratories, Indianapolis, Indiana Received April 19, 1968 The series of acetylenic carbamates was extended with emphasis 011 the N-cycloaliphatic derivatives. The Ncycloaliphatics had much less cell culture cytotoxicity and neurotoxicity as determined by intrathecal studies ~ I dogs than the NHz compounds, even though their acutcb toxicities were about the same. 11Iost of the N-cycloaliphatic compounds exhibited ant it umor activity.
It has recently been reported' that a series of acetylenic carbamates possessed potent antiturnor activity against several experimental neoplasms in animals. From the initial structure-activity relatioriship study, it was apparent that the K-cycloaliphatic groups were very beneficial in promoting antitumor activity. This paper presents the investigation of the relationship of certain toxicological effects to substitution on the nitrogen and an extensive structure-activity study of the carbamates with the S-cycloaliphatic moiety, using the X5563 and C149S tumor systems. Chemistry.-Since the compounds in this series all involve monosubstitution on S, use was made of the reaction of the 2-propyn-1-01s with a cycloaliphatic isocyanate as previously described.' An improvement in this method was utilized that greatly accelerated the reaction, and yields up to SOY0 u-ere obtained. This involved the use of CH2C12or NeCX as solvent with addition of a catalytic amount of R&O, and a trace of H20 and EtOH. All products are listed in Tables I OH 1
R-~~-C=CTT
I
+ R*N=CO
KlCOa
trace of HoO CtOH
+
11'
I
I1
R' I11
and 11; their purity was determined by the usual physical methods (nmr and ir spectra and elemental analyses). Pharmacology. Toxicity Studies.-The influence of structural changes on certain toxicological effects n-ere investigated with particular emphasis on the S H , and S-cycloaliphatic carbamates. The acute toxicities* in mice of six of the carbamates are listed in Table 111. (1) R . D . Dillard. G. Poore, D . R . Cassady, and N . R . Easton, J . M e d . Cfiem., 10, 40 (1967). ( 2 ) Long-term toxicity studies nit11 t n o of the rarlmmates, 48 and 60, nil1
lip
pirlrlislied elsewhere
There appear to be no significant differences in acute toxicities of the S H , and S-cycloaliphatic compounds (48 arid 50, see Chart I) ; however, a comparison of the phenyl with p-fluorophenyl shows that the fluoro conipourid is more toxic (50 and 51). C H ~ R Ia T
4a
OCONH W
-
m
C
OCONHR2
I:-C-C=CII
I
50
0
49
H
F 51
Studied in diverse in vitro cell systems, dramatic differences in activity were observed (Table 111). The KH, carbamates 48 and 49 showed inhibition against the nonparasitic protozoa Tetrahymena pyriformis, Euglena gyacilis, and Ochromonas malhamensis, the algae Chlorella vulgaris and Scenedesmus basiliensis, and the human cell HeLa, previously used to detect potential antitumor agents. For the S-cycloaliphatics 50, 51, 29, and 31 a complete lack of cytotoxicity was demonstrated (although these do show potent antitumor effects). This difference in cytotoxicity has been demonstrated against other tissue culture and bacterial cell systems. The in vitro cell studies were extended t o all of the
