September 1969
s51
2- (N,N-DIALKYLAMINO) ETHYL a-(3-PYRIDYL)MASDELATES
@-methylgroup would be nearly eclipsed in the bound state. This conclusion appears improbable on the basis of energy considerations. h skewed conformation such as in V is more appealing; a slightly twisted conformation for I1 is a reasonable approximation of V. If the comparisons are valid, the conclusion emerges that binding on active sites may not necessarily involve the thermodynamically preferred conformation of the ligand, a fact which was recently brought to light in the case of a constrained substrate of chymotrypsin." Results of X-ray studies on crystal^,^,' as well as theoretical ~ a l c u l a t i o n s predict ,~~ opposite conclusions; the obvious reason for this is that no account is taken of the fact that proteins display conformational specificity.l' Owing to internal comperisatiori effect^,^ strained conformations of substrates and inhibitors may be readily stabilized through the translocation of conformational energy within the protein. The reduction of the free energy of activation encountered in enzymecatalyzed reactions has, in fact, been explained by
JencksZ6as resulting from the induction of a strained conformation approaching in structure that of the transition state. Isotope-eff ect studies on the binding of substrates on enzymes have led us to similar con~lusions.~~ * ~ not seem impossible therefore It~ does that IV and V may represent the biologically active conformations a t the binding site level. Finally, it is of interest to note that the configurational handedness of the AChE binding sites is similar to that of the muscarinic receptor binding sites. Acknowledgments.-The authors are grateful to the Defence Research Board of Canada and the Kational Research Council of Canada for the financial support of this work. The 3-quinuclidinol was generously donated by Dr. R. Heggie of the DRB. (26) W. P. Jencks, in "Current Aspects of Biochemical Energetics," N. Kaplan and E. Kennedy, Ed., -4cademic Press, New York, N. Y., 1966,
p 273. (27) B. Belleau and J. Moran, Ann. S . Y AcadSct.. 10'7, 822 (1963). (28) B. Belleau, Stud. B t o p k y s . . 4, 95 (1967).
2-(N,N-Dialkylamino)ethyl Esters of ~(3-Pyridy1)mandelicAcids. Synthesis and Pharmacological Evaluation A. SOVELLI, J. R. BBRRIO, Departamento de Quimica Orgcinica AND
Depui luruenlo d e Farmacoloyia, Facultad de Farmacia
H . HCIDOBRO Bioquimica, liniversidad de Uuenos Aires, Uuenos A ires, J r y e n l i n a
Received A p r i l 1, 1969
2-(N,N-Dialkylamino)ethylesters of ~(3-pyridy1)mandelicacids were prepared and screened for pharmacological activity. Compounds VIIb and e compared favorably with benactyzine hydrochloride as inhibitors of spontaneous motility. Some of them (VIIa, b, d, and e) also show anticholinergic, spasmolytic, antihistaminic, and anti-5-HT effects.
Aminoalkyl benzilate esters (I) possess pharmacological effects t,hat have several clinical applicat,ions.* The presence of a pyridyl instead of a phenyl radical should change their pharmacological properties. To prove this assumpt'ion, synthesis of type I1 derivat'ives containing a 3-pyridyl radical was undertaken.
@ @LC/0H 'co2y-7x< , I I
q
1 / I I'
Q C / 0'c0.r-m H J
SCHEME I R
It'
K'
111
I1
T h e general process of synthesis is shown in Scheme 1. IIZa (Table I) was obtained in good yields by condensing ethyl phenylacetate and ethyl nicotinate in NaOEt. ( 1 ) (a) A. Astrom. Acta Pharmncol. Tozicol., 8 , 363 (1952); (b) E. Jaoobsen. Danish M P ~Bull., . 2, 159 (1955); ( c ) E. Jacobnen a n d T. Sliaarup, Actu f'hurniirrol. Torirul., 11, 117 (1955): id) 1,;. Jacobsrn and E. Sonne. ibid., 11, 135 (l(155); (e) zbrd., 12, 310 (1Y56); ( f ) 11. G r e t h e a n d E . Jacobsen, ibid., 18, 125 (1957); ( 9 ) H. Holten and E. Sunne, i b i d . , 11, 148 (1955). ( h ) RI. J. Raymond and C. J. Lucas, Brit. .Wed. J . , 1, 952 (1956): (i) U. Larsen a n d C. H. Holten, Acta Pharmacol. Tozicol., 12, 346 (1956); ( j ) L. Alexander, J . Am. .Wed. Assoc., 162, 966 (1956). ( 3 ( a ) I . h l u r ~ k ~ a.4rto d P . , \ ~ c u ? " / . ,+,I,,,/,, 3 0 , 72y [IYAT,); (1,) 1s. E.l)avies, Brit. M e d . J . . 1, -1 5 6 ) ; ( c ) C . 11. llulten, A c t a I>liarmt~col. 7'oricol.. 15, 113 (1957); (d) JI ardes and SI. Laulan. Presse .We,/,, 65, 180 (1957); (e) A. Coady and E. C. 0. Jewesbury, Brit. Med. J . , 1, 485 ,1956); ( f ) L. Alexander, J . A m . M e d . Assoc.. 166, 1019 (1958).
vI
\'I1
Using the same method, mono- (IIIb) and dimethoxy (IIIc) derivatives were obtained from the ethyl esters uf homoanisic arid homoveratric acids, respectively. Legrand and Lozac'h obtained the p-keto ester by condensing ethyl nicotinate and ethyl phenylacetate i1i low yields o i ~ l y . ~When coiiclensatioii was carried out with ethyl 3-pyridylacetate and ethyl
(lix)
(3) I,. Legrand and N Lozac'li, Bull. Soc Chzm Frnr'ce, 79 (1955).
i ) y ~ i ( ~ y l ~ i i i : i i i (:i(*idq l ~ , l i (with ~
2-S ,S-tli~ill\?.l:iiiiino:tlcowith yir>ld. Iwt\\(vn tint1 JOG( (nic.thoti H ) I t \\a. :11w pos\ihle to prep:ti~)\-II:i a i i t l \ ' I I d w i t h I i L v yield5 by heating :i L'-S,S-tliiilkvl:~nlino:tlcohol I\ itti Lu-(X-pyridyl)maiidelic acid, using excess H2SOa (methoti -1) I t \vat not posqible to obtain the ?-[S,S-diaIkylaniiiio)alkyl e*tws of tlrc, niethoxv wid, by t h i in et li( )( 1. If the ecjuilibi iuni oi tlie w a c t i u r i i\ r i o t diap1:ic~d1 ) ~ cliitilhtion of the EtOH produced during its courw, tht. yields of transestcrification become condernbly lowvri.. ' l l i - \I:IS found i n the prep:u:ition of \'I I a :tiid VITc. hut Tvhcii :in attcmpt \v;ts mndc, to prep:^^ \'[It) k)y t 1 1 ~ hame techniyucl. the niaiii product isolated u :i< .$pyridgl p-methoxyphenyl ketone (VIII). Pharmacological Evaluation.--The 2- (S,S-dialbv Iamino)ethyl ester. \\ ere screened for pharmucologic.:il activity arid t h e reaults of the observations are sumrnnrized in Table TV. ( ' o n i ~ ) o ~ i i i ~1.1 l h 11) :ti111 \'He (nioiioinctho -lie\\ c d +qiitir:iiit inhibition of hpont:iiieous motility, hcilh
2- (N,N-DIALKYLAMISO) ETHYL
Septembcr 1969
TABLE IT' ~-
7
Doso, (:ol11pd
mg/ml
\-11a
0.01 1 0 ,0 1 0.1 1 1
~~1111
\.IIc T?Id
\lie
\TIf
0.1 1 0.01 0.1 1
Guinea pig ileuma Anticholinergic Spasmolytic Antihistaminic etrect effect effect
45 70 0 10 100
0
70 100 10 60 0
40 60 0 8 S.i 0
30 100 10
4.5 0
50 70 0
(Y-
833
(3-I'YRIDY L) MASDELATES
-__.inti+HT etfect
30
--
.A)
0
10 !IO
S.i
0
0
G .i 100 16 60 0
G .i 100 10 GO 0
I
.-----Spontaneous Dose, mg/kq
0.1 10 0. 1
IO 0.I 10 0.1 10 0.1 10 0.1 10
motilityh--Activity Duration cage inin
0 19 IS 75
2) 17
0 17
,I.)
0 2:::
a6
19 70 0 11'
--
::S ti .i 1'1)
Beuactyzine HCl 10 27 .lo ChlordiazeIO 0 poxide 50 30 3) a Heduction of spontaneous contractions (%) against acetylcholine chloride, 0.1 fig/nil; BaCI,, 100 fig/ml; histamine dihydrochloride, 0.01 fig/ml; and S H T , 0.1 kg/ml, respectively. These pharmacological assays were performed on isolated organs (R. A. Turner, "Screening Methods in Pharmacology," Academic Press, h'ew York, h'. Y., 1965, p 43). The test compounds were added to the bath 30-60 see before the agoni . * Reduction of spontaneous motility of mice in jiggle cages (J. R. Boissier, Therapit,, 13, 1074 (1958)). Ten mice x w e used for each dose level and the animals were iiijected iiitraperit,oneally. Controls were injected with saline. When the (wnipoiiiid was active, the effect appe:wed 4-7 niin after iiijectii)ii
with :i prolonged effect. Compounds VIIa, c, d, and f were moderately effective. All the compounds tested were nontosic :it 0.1 mgJ;g; however, a t higher doses (10 mg/kg), the decreased spontaneous motor activity was usually accompanied by respiratory depression and/or tremors or convulsions. S o n e of the compounds was lethal a t 10 mg/kg. VIIa, b, d, and e also showed anticholinergic, spasmolytic, antihistaminic, arid anti-5-HT effects, while T'IIc :ind T'IIf (diniethoxylxted) mere ineffective.
Experimental Section6 Benzyl 3-Pyridyl Ketone (IIIa).--A mixture of 37.7 g (0.25 mole) of el hy1 iiicotinate and 44.0 g (0.26 mole) of ethyl phenylacetate
\vas added, over a period of 45 min, to 27 g (0.39 mole) of S a O E t ,
with vigorous stirring. The mixture was kept a t 20-25" for 0.5 hr and theii heated for 12 hr a t 60-70' with constant stirring. After coolittg, 78 nil of concentrated HCI were added, and the inistm,e was heated uiider reflux for 3 hr. On cooling, benzyl :bpyridyl ketone hydrochloride crystallized and was rollerted :iiitl \ ~ a s h e dwith CHCI,. The crude product was dissolved i n If2(), and the ketone was separated with 105; SaOI-I, filtel,ed, ivashed, (Ivied, and reci~ystallized. 4-Methoxybenzyl 3-Pyridyl Ketone (IIIb).-The technique iised was the same as for I I I a but the hydrochloride did not crystallize. HZO (100 ml) was added and the aqueous layer w w extracted twicae with CHClr. The ketone was precipitated by adding l0yo S a O H , filtered, washed, arid recrystallized. Similarly, 3,4-dimethoxybenzyl 3-pyridyl ketone IIIIc) was prepared. Condensation of Ethyl Benzoate and Ethyl 3-Pyridy1acetate.The general procedure described for I I I b was employed. K h e n the aqiieoiib extract was made alkaline, the oil that separated was extrarted \vith CIIClp aiid dried (SlgSOr). The solveiit was removed ~ i i t l the residite was distilled, bp 175-1'J0° ( 5 inm). On coi~liiig,the distillate solidified arid was extracted with cold Et,(). The i,ecrystallized residiie gave 1,3-bis(3-pyridyl)propanone (IIIe). The ethereal extract was dried (hlgSOd), a i d the solveiit rvitpwated. The rec~i.ystaIlizedresidue gave IIId. . __ - . ( 6 ) All nieltiny points were taken in capillaries a n d are uncorreated Infrared spectra were measured an a Perkin-Elmer Model 137 B Infracord. Satisfactory ir spectra were recorded for all compounds listed in t h e tables. Nmr spectra were determined on a Varian A-60 (TMS). Microanalyses were lrerformed a t this laboratory. Where analyses are indicated only by symbols of the elements. analytical results obtained for those elements were within z t O . 4 % of the theoretical values.
Substituted l-Phenyl-2-(3-pyridyI)glyoxals. General Procedure.-Tii a solution of 0.10 mole of the appropriate benzyl ketone i i i 200 in1 of AcOI-T, 11 .1 g (0.10 riii~le) ofsiihlirneil SeO, was added and the mixture \vas heated a t 120' for 4 hr. After cooling, Se was filtered off and the filtrate was poured into 500 ml of H 2 0 and neutralized with concentrated KHaOH. If the product crystallized, it was filtered, washed, and purified. If it was an oil it was extracted with CHCla and dried (llgSO4), and the solvent evaporated. The residtie was distilled under reduced ement. General Procedure.The appropriate glyoxal (20 g) suspended in a solution of 20 g of IiOH in 100 ml of 1120was heated on a water bath a t 80" for 10 min. The solution was cooled and acidified with concentrated HCI to p H 4. The acid was filtered off, washed (CHCL), and recrya t allized. Ethyl Esters. General Procedure.-The appropriate acid (11.0 g ) was added to a cold mixture of 17.5 ml of concentrated HpSOa and 200 ml of absolute EtOH, n-ith stirring and heating under reflux for 4 hr. Most, of the alcohol was evaporated under reduced pressure. Then 200 ml of H 2 0 was added and the ester was precipitat,ed by adding 10% SaOH. The solid was filtered, washedj and recrystallized. 2-(N,N-Dialkylamino)ethylEsters. Method A.-a-(3-I'yridyl)mandelic acid (1.0 g ) was added to a cold mixt1ir.e of 3.3 ml [ i f coiicentrated HzSOa and 3.0 ml of 2-(X,N-dialkylaminc1)ethand: the mixture was heated a t 100" for 4 hr, then cooled and poured into 10 ml of H20. The 2-(S,S-dialkylamino)alkylester was separated by adding Concentrated SHaOH, extracted (CHCla), and dried (MgSUd), the solvent was evaporated, and the hydrochloride was prepared. Method B.--lr'a (50 mg) was added to a niixtrve of anhydrous 2-1h',~-dialkylamiiit1)ethaiiol(5 nil, excess) and dry CeH, (40 ml), in a flask fitted wibh a short fractionating column and a still head. The solution was heated rmtil it reflrixed (bp 80"). The appropriate ethyl ester (2 g ) in C6H6 (30 ml) was then added sk~wly,the vapor temperatiire falling to 60-65". C61f6-EtC)EI wan then distilled off until all the ester had been added and the vapor temperatiire had risen to 80". The PhII solution was washed three times (Ii,O) and dried (AlgS04), the solvent \vas evaporated in vacuo, and the hydrochloride \vas pepared. 3-Pyridyl p-Methoxyphenyl Ketone (VIII).-2- (S,S-1)inlet hy1ttmino)ethanol (2 ml) was added to 20 mg of S a i n 10 nil (JF PhMe. The mixture wad heated until it refluxed; th \'Ib in 20 1111 of PhMe was added dropwise arid the ni heated for 5 hr. The I'hble whition was washed three H2O and the solvent was distilled in tiacuo. The residue was extracted with hot petroleum ether (bp 40-60') and aft.er 24 hr
Maloiianiic Esters.
A New- Class of Seclative--'rranyuilirr,t.l.k
