Maloiianiic Esters.
A New- Class of Seclative--'rranyuilirr,t.l.k
TABLE I PROPERTIES OF R;IALONAMIC ESTERS
R1 R3OCOCCOX
I
RP It I
COllll,d
1 2(V)
CSIIS C6H3 CJL
4 5
C6Hi
R2
R3
x
11e
Me H Me Me Xe Et 2-Pr
SHZ
Et Et Et Et Et
KH? XHB KHlIe XlIe?
Alp.
i/C
50 37 91 60 i0
oc
93-96 118-120e 90-100,5
f
Overt effects' i n rat
300 >300 .50 300 300 50 300 >300 >300 >300 >300 123
EDso, mg,'ke PO Anti-metc 31ESd
MAh SSA 21
MA$
Formula'
8.5 SSAh
CiiHi3Kjo3
76 X S 35
C12HisN03 CiaHiiNO, ClaHiJ'J03 CnHiiN03
31-52 SSh CJI: 73-i-lQ .i2 NHz 13 6 CsHs SH, 50 111.3-111 NSA 7 CsHj Et a 1.53-1 54 SSA S 8(VI) CsHi Et, -C (CH,),SH9 CsH5 Bri Ale NHP 13 131-132 NSA X 10 CGHi CsTIj Me NHz 30 192-193,3 Sd.4 SSA C16HljN03 11 (CH~),CIICHZCHP Et, l\le KH, 60 96-97 SSA SSI CiiHnNO, 47 120 Meprobamate .io 33 24 Phenobarbital Protection against metraMinimum dose (mg/kg PO) at which overt effects are produced. Based on I11 or immediate precursor. zol-induced convulsions in rats. d Protection against maximal electroshock seizltrep in mice. e E. Testa, L. Fontailella, G. F. Criqtiani, T o signifiBp 122' (0.025 mm). 0 Lit.e mp 78-79'. and L. Mariarii [Helu. Chim. A c t a , 42, 2370 (1959)] reported mp 112-113". Active at a cant activity at a dose of 50 mg:'kg PO. i All compounds were analyzed for C, H, and N except 2, a known compoiiiid. dose of 100 mg/kg PO.
-_
'
'
acetone
KaOR
ROCOCCOOH
I
RL
0
Iv
I11
1
i
(1)SOCI,
(Z)NH,OF
NH,OH
c&5
I HOCOCCONH, I CBHj
CH,K?
T
ROCOCCONH,
I
R2
V
VI
nificsntly decreases CKS depressant activity as measured by gross obbervatiori in t he rodent. Substitution on the amide h' (4 and 5) way found to eliminate most of the CSS depres5:iiit activity. Conbequently, subsequent studies were done with urisubstituted amides. The ethyl ester 6 a t the EDjodose produced only weak
protection against the clonic couvulsion induced by intravenously administered metrazol. Higher esters are much less active and the free acid is inactive in our test procedures. Activity for C I S depressant action required one aryl and alkyl group, since diary1 (10) or dialkyl (11) compounds produced little overt CKS depressant activity in t'he rodent. There was little significant difference in the activity of cl-, 1-, or dl-I.
Pharmacology of Methyl Ethylphenylmalonamate (I).-In animals methyl et8hylphenylmalonamate (I, 3 in Table I) has sedative and tranquilizing activity. I t produces overt signs of C S S depression in all species of animals tested, sharing many of the pharmacological properties of phenobarbital, meprobamate, and glutet'himide. Methyl ethylphenylmalonamate, phenobarbital, arid glut'ethimide produce ataxia in the mouse at approximately the same minimal dose levels of 50 mg 0 orttlly. These studies showed t h a t I differs froin p h ~ i i o harbital in that it exhibits :I faster oriset ut' actioii, :I shorter duration of actioii, aiid is much less toxic in :mimals. Iri addition, this agent does not produce the marked degree of excit'emerit, hypersensitivity, confus-
\
85 ti
+HI
1:
1 \ I I I[)\. O b
VI
\I
111 \1
o\
l\l\ 1I
C,H
OH
I 1 CH,OCOCCONHCHCCI I CH
I
IX C ,H ( (
I
I ( HO
CH,OCOCNHCOOCH C,H
I
CH OCOCCS I c' I3 \.;TI
ioii, or increase 111 spotitaiieoii> mot ut activity iii niice that is produced by phenobarbital or glutethimide. Experiments were carried out using the measurement of 3pontaneous motor activity in mice as an indicator of the depressant action of compounds on the C 3 X 4 The data in Table I1 show that I produces only decreased motor activity after administration of 130 or 200 mg bg pi I t cau.eq either very slight iticreaies or decrease3 in -poiitaneou.s motor :ictivity, depcwding on the time of recording after drug treatment. at doses of 2 5 , 50, or 100 irig/kg. The maximum increahc in motor activity i5 only . X ~following o a dose of 100 mg lig. On the other hand, phenobarbital causes :it1 iiicreiiqe in motor act i \ ity nfter ntlrniiiistratioii of doseb ranging from 25 t o 100 111g kg p ( 1 I t should be further rioted that a dose ui 100 mg 1,g Of phenobarbital produces an increase in sporitaneou\ motor activity of 1877, over the control 1 1 1 ( o o k , I . t \ \ e d l w It \\ r o l 1rpLl 7 l i v r i i p 113, I I 1 I Y i i 1
\lotii-
.ml 1'
\
\lait,.
7 I
01.
12
~ I A L O K AESTERS MIC
September 1969
,-
Test
_
_
~
JI et h vl et lis lphen3 1malonamate (1)
Pentylenetetrazole 24 (17-34) antag ( r a t ) ('AH,' (rat) 66 Fightiiig behavior 30 (25-7.;) [moube) ~ I H X electrohhwk i6 (63-89) (mouse) 13;, (82-223) Strychnine antag (mouse) a Estimated values.
E.D,o. mg kp--Sodium phenoharbi tal
\I eprobaiuat e
io
47 (36-611 340
44 (34-56)
84 (56-126)
24 (18-25) 111 (79-157)
132 (12'2-143) 300 (99-906)
26 ( I X - 8 X )
ditioned avoidance response (CAR) in r a t s 4 The inhibition of the CAR appears to be nonselective since blockade of the conditioned response is accompanied by a block of the unconditioned response. I n mice this compound also prevents the foot shock induced fighting behavior16prevents the convulsions produced after maximal electroshock7 and subcutaneously adminstered strychnine18and potentiates hexobarbital sleeping time. Methyl ethylphenylmalonamate is well tolerated by the animals. Daily oral administration of 100 mg/kg of the drug fails to produce cumulative toxic effects; repeated daily administration does not produce appreciable tolerance as determined by using the incidence and duration of ataxia. I does not influence autonomic standard test agents when tested intravenously in the anesthetized dog (120 mg,'kg). It has no effect on mean arterial blood pressure in the anesthetized dog in doses up to 10 mg/kg iv. A dose of 20 mg/kg iv causes only a transient depressor response, slight respiratory depression, and a slight decrease in the heart rate. I n the unanesthetized dog, this compound fails to show any electrocardiographic evidence of toxicity after acute doses of 100 mg/ kg orally. The EL), values for I, meprobamate, and phenobarbital in a number of pharmacological tests are presented in Table 111. Since it ih well known that phenobarbital is capable of stimulating microsomal enzyme activity, I was evaluated for possible similar action. Groups of rats were treated orally with doses of 100 mg/kg of phenobarbital, 100 mg/kg of barbital, or 150 mg/kg of I daily for 4 consecutive days. On day 4,hexobarbital wa9 administered. Sleeping time was markedly reduced in those rats which received phenobarbital or barbital. On the other hand, sleeping times of the I-treated rats were essentially the same ab those of the control rats which received hexobarbital alone. Thus I does iiot resemble phenobarbital in its ability to stimulate microsomal metabolism of hexabarbitol, as indicated by its lack of effect 011 hexobarbital sleeping time.
(6) R. E. Tedeschi. 1).H. Tedeschi. .iMuctia. . L. Cook, P. A . Mattis, and E. J. Fellows. J . Phurmocnl. Ezptl. T h e r n p . , 126, 28 (19.59). (7) J. E. P. Toma? and L. S.Goodman. Proc. Assoc. Res. .Vemous Mental Diaease, 26, 141 ( l W i ) . (8) M. J. Orloff. H. I.. \Villiain>, a n d C. C. PfeiEer, I'roc. Soc. E i p t l . B i d . .Wed., 70, '254 (1829).
s57
Deneau and coworkerss tested I in beagle dogs made physically dependent on a dose of 100 mg/kg of sodium barbital, orally, once daily. Dogs on this dose of sodium barbital will show convulsions and delirium during withdrawal. Substitution of I for sodium barbital in the above protocol resulted in delirium and severe tremorb at 30 hr. I t \$-asconcluded that I does not possess any barbiturate-like physiological dependence capacity. Metabolism.-Analysis of the urine of rats dosed acutely with 100 mg/kg of I orally, showed the presence of some unchanged drug and some ethylphenylmalonamic acid (V). S o decarboxylated material, aphenylbutyramide, could be detected in the urine. Because of certain structural similarities to phenobarbital, the urine of these animals was also analyzed for the presence of phenobarbital and its metabolites, but none were found. For the same reason, the urine of rats dosed with phenobarbital was analyzed for the prehence of I or its metabolite, ethylphenylmalonamic acid, but no traces of either were found.1° Summary.-Methyl ethylphenylmalonamate (I) may be characterized as a sedative with a component of tranquilizing properties; it shares properties with both phenobarbital and meprobamate. I n addition, preliminary studies indicate that I differs from the barbiturates in that it does not appear to stimulate microsomal activity in the liver and does not possess any barbiturate-like physiological dependence capacity. Experimental Section" Substituted Malonic Acids. General Procedure.-A solution of 1.5 moles of S a O H dissolved in 100 ml of H20 was added slowly to a stirred solation containing 0.2 mole of the malonic ester in 40 ml of 11IeOH. The reaction was usually exothermic; a white precipitate soon formed. The stirred suspension was heated for 2-4 hr, then put under vacuum to remove most of t'he XeOH. The solution was cooled and extracted once with Et,O, then the aqueous layer was cooled and acidified with dilute HC1, and the malonic acid separated as a solid and Tvas filtered or as an oil which was isolated by extraction wit,h Et,O. The acids can be used in the following steps without purification. All of the acids were known compounds. 2,2-Dimethyl-5-phenyI-5-alkyl-4,6-dioxo-l,3-dioxane (Acetonides, 111). General Procedure.'-A suspension of 0.033 mole of t,he malonic acid in 10 ml of AcZO was cooled to l5O, then 0.5 ml of concentrated H2S04 was added. To the resulting solution was then added 10 nil of dry NeaCO dropwise over 5 min while maintaining the temperature a t 15". The solution was stirred 1 hr then kept a t 0" overnight. I n most cases the solid acetonide separated in pure form and was filtered and rinsed with ice water. An additional quantity of product was obtained by pouring the organic filtrate into ice water. An oil separated and then crystallized on stirring. The acetonides can be recrystallized from i-PrzO or used without further purification. The acetonides show a characteristic doublet a t 5.63 ( m ) and 5.78 p (s) in the ir; they also show strong absorptions a t 8.2-8.3 and 9.3-9.4 (mulls). The following new acetonides were prepared: 5-, mp 144-146' (:OFc yield); 5-pheii;\-l-,5-butyl-, yield); 5-ethyl-5-i$oanij.1-, bp !)4-10'~o(0.2 mni) (85yc yield). . i d . (CmI-I,,04)C, H. F u r 5-phenylncet~,nide (9) G . A. Deneau and M.Wilson, Addendum t o Annual Report, Problems of Drug Dependence, 31st Meeting of Committee on Problems of Drug Dependence, National Academy of Sciences, National Research Council, Feh 24-26, l 8 6 Y , Indianapolis, Ind. Compound I is referred t o as S K F 24288 and N I H No. 8248. (10) We are indebted t o E. L. IIaines. .\. P u a t . u n J 11. Eisele uf U U I IaLuratories for these chromatographic studies. (11) All meltin& points (Thomas-Hoo r e r apparatus) are correcteci; anal?.ses were performed by the Analytioa 1 Department of these laboratories. Where analyses are indicated on1.v hy symbols of the elements, analytical results obtained for those elements \vere within &0Ac& of the theoretical values.
phenylbutyric acid (VII, 100 g ) was added to a solution of 100 g of quinine in 200 ml of AIeOH. The solution was cooled in an ice bath and stirred vigoroilsly until a precipitate formed. The suspeiisiun was theii fiirther rooled in a D r y Ice-JlenCO bath :md then filtered. The solid was stirred with i-PrOII atid fillered, dryness, i n z~ucuo,t l J give 5.8 g of a yellow oil. The oil, when then stirred with Et& a ~ l dfiltered agaiii, yielditig 87 g of halt, triturated 1vit.h hesane, cryhtallized t o give a white solid, mp 89partially meltiiig :it 125-135", with the \)al:itic-e melting a t 145115', 4.6 g. The solid was recq-atallized from i-PrZO and then 147', [ a ] Z 5-110" u (in .\LeOI-I; :dl r,ol:rtioti~are of 1'; ctrnceiitmfrom CCh and CHCl, to give 0.6 g of prodiict, mp 141-143.5'. tion holiitioti). .i 2-g sainple was coiivertecl t l J the free acid by d i s d v i n g iii diliiie Ii('lj estr:ictiiig the aqiieoiis inistiire slid Il;t)Oj aiid coiicentr:~tii~gthe Ki?O luyer to give 0.8 g of the acid ah a , . Pb(O.lt), (2.2 g, 0.05 mole) was added to-a solLition of I in hIeOH. colorless oil, n % 1.4!1!)8, [ a ]2 G ~-j 1:;' (iit CHC1,). The qiiitiine The system was flashed with S?,and the solution wa5 then heated salt was recrystallized three time:. by rapidly dihaolvirig iri CHClr at reflux for 1 hr Tvhile Xs was bLtbbled through the system. The and precipitatitig with i-l'rd), t o give 60 g of salt. sample. from color first became bright yellow, then later disappeared. Dilute t allizat io t 1.s gave t lie followi I I aqueoris Na2C03wab added, the misture was extracted with Et?O, iid -121' ( i i i JLeOII). I:e arid the Et20 extracted was dried arid concentrated to give 10.5 g JIeOI-I did l l t J t c*Iiairgethe rot:ition. 1Tydr.r .tallized O I I stiwiiig with a little i-Pr&, mp 60[ o ] % - I!)' (it1 CTICl:j),n% 1.51:;!). Methyl ( - )-2-Cyanophenylbutyrate.-( - )-%-C~-aiio-2-pheria1 wit;. purified by "dry column" chromatogra- I phy'j on an aliimitia coliiniti, 58.6 X 3.8 cm, using CH2C1, as ylbkityric. acid (17 g ) wxs cotiver(ed to the methyl ester (14 g ) solvent. B?- thia means 5 g of an oil that crystallized, mp 72with CHaS,, by the procediire described earlier, [CY]2 5 ~-39.2" 74", was obtained. Recrystallization from hexane gave 3.9 g of ~ ) H, S . (in CHCI,). Artal. ( C , J J l ~ Y O .C, product, mp 73-75". -anal. ( C L B R I ~ NC, O H, ~ ) N. Methyl ( )-Ethylphenylma1onamate.-JIethyl ( - )-2-cyaiioMethyl 2-Phenyl-2-acetamidobutyrate(XI).-Pb(0Ac)r (40 2-pheiiylbrityi,ate (14 g ) was hydrolyzed with H2S04 by the prog, 0.09 mole) was added to a d u t i o i i of 20 g of I in 400 ml of cedure desci,ibed pievioii,4y, to give 5 g of prodilct, [ a ] % +39.3" a I n u l . (CI?Ill:SO:j) c,IT, S . ilc0H. The soliiiion was heated a t reflux for 4 hr, then diluted (in CHCld),nip !)X-!JYo. with HpO and estrarted with CH2C1?. Concentration of the (+)-2-Cyano-2-phenylbutyric Acid.--The combined fill rater organic layer gave 18 g of a dark oil. Five grams of this oil waj illizatioti of the qriiriiiie salt prepared from cll-2chromatographed by the ''dry columii" procedure'j on a column iityi,ic acid (ahove) were concentrated and hydrolyzed t o the :ic,id. ( - )-:i-Phe1iyl-2-ami1ll,pl.c,~:lne (14.5 g ) was added t o 20 g c i f this :ic.id dihsolved iii 200 nil of Et. Y O O n separated, 12.5 g , nip !11.5-02,5°. After three r mp 153-154'. .Inal. (C1,Hl;XOl) C, H, X . tion?;from CHC1,-EtyO, 7.8 g of salt obtaitied, mp 95-95.q5a, Metabolic Studies.-The urine of rats dosed with 100 mg/kg with the followitig t~ot:itions: [ a ] 2 5 u-40.75, -43.5, -43.7" p o of methyl ethylphenylmalonaniate was collected for 5 hr following admitlistration. The iirine was chromatographed1° (in CHC1:i). Hydmlysi, of 5.5 g of the salt gave 3.3 g of the acid, on silica gel G plates using a C6He-dioxane-.4cOH system [a] 2 5 ~ 18.5" (in CHCI,). (90:25: 4)) and spots were located using a Hg(0.4~)~-diphenylMethyl ( - j-Ethylphenylma1onamate.-( )-%-Cyano-2-phencarbazone spray reagent. In this system, the following Xr's and ylbkityi,ic acid \vas coiiverted t,o methyl ( - )-ethylphenylmaloiiacdors are obtained: ethylphenylmalonamic acid (V, Ri 0.45, mate, [ a ] 2 5-4J.9' u ( i t i CHCI:
