J, Med. Chem. 1983,26, 649-657
`Antihypertensive 0-Adrenergic Blocking Agents: N-Aralkyl Analogues of
`2 4 3- ( tert -But ylamino)-2- hydroxy propoxy l-3-cyano pyridine'
`
`649
`
`David E. McClure,*pt John J. Baldwin,’ William C. Randall,+ Thomas F. Lyon,? K. Mender,? G. F. Lundell,?
`A. W. Raab,+ Dennis Gross,$ Edwin A. Risley,’ Charles S. Sweet,$ and Michael Williams$
`Merck Sharp & Dohme Research Laboratories and Merck Institute for Therapeutic Research,
`West Point, Pennsylvania 19486. Received August 2, 1982
`An interest in dual-acting antihypertensive agents, specifically those related to (S)-2-[3-(tert-butylamino)-2-
`hydroxypropoxy]-3-~yanopyridine (l), led us to probe the contribution of the side-chain amino substituent in this
`series. The ability of 1 and its various analogues to displace radiolabeled a1 (WB-4101 and prazosin) and P
`(dihydroalprenolol) adrenergic receptor ligands wm assessed by receptor-binding techniques. Most of the compounds
`exhibited high P-adrenoceptor binding affinities, but only the N-aralkylamino-substituted compounds showed high
`a,-adrenoceptor affinities. Therefore, the vasodilation shown by 1 was not due to an interaction with the a1
`adrenoceptor. The aralkylamino analogues of 1 in spontaneously hypertensive rats and anesthetized dogs exhibited
`antihypertensive activity and al-adrenoceptor blocking properties. Unlike the preference shown by P-adrenoceptors
`for S enantiomers in this oxymethylene class of blockers, the chirality at the secondary hydroxy center made only
`a minor contribution to the affinity for the al-adrenoceptor and even less of a contribution to the observed
`antihypertensive effects. This lack of chiral influence at the hydroxy center confirmed what had been previously
`observed in more limited studies with the isomers of both labetalol and medroxalol.
`Adrenergic receptors have been classified as a or @ de-
`pending upon their relative responses to various adrenergic
`agonists.2 This classification was further refined to define
`al, a2 and pl, p2 receptor subtypesa2 Side effects associated
`with antihypertensive agents operating via a-adrenergic
`blockade are reflex tachycardia and postural hypotension?
`In principle, the reflex tachycardia should be eliminated
`by concomitant @,-adrenergic blockade. Problems asso-
`ciated with nonselective @-adrenergic receptor blockade
`
`are bronchoconstriction and Raynaud’s ~yndrome;~+~ these,
`in principle, should be alleviated by the presence of al-
`adrenergic blocking activity. Thus, the complementary
`pharmacological profiles suggest that a properly balanced
`a,@-adrenoceptor antagonist would be free of many of the
`side effects associated with the use of either type of agent
`alone.
`The application of a strategy considering this comple-
`mentarity was investigated as part of our program directed
`toward the development of antihypertensive @-adrenergic
`receptor antagonist^.^ As a first step, it was necessary to
`assess the contribution of a,-adrenergic receptor blockade
`to the increased peripheral blood flow observed with
`(S)-2- [ 3-(tert-butylamino)-2-hydroxypropoxy]-3-cyano-
`pyridine (l).5 This analysis was followed by the re-
`
`Scheme I
`
`Method A
`
`CN
`
`CN
`
`NHR
`
`(SI-9
`
`placement of the tert-butylamino group in 1 with various
`aralkylamino substituents to determine if such moieties
`might introduce, or enhance, a-adrenergic blockade. Re-
`cently, other dual-acting compounds have been reported.
`These include labetalol(2),6J medroxalol(3),S and sulfinalol
`
`1, R = tert-butyl
`
`2
`
`OH
`
`3
`
`YH
`
`4
`
`This paper has been presented in part; see “Abstracts of
`Papers”, 181st National Meeting of the American Chemical
`Society, Atlanta, GA, Mar 29-April 3, 1981; American Chem-
`ical Society: Washington, DC, 1981; Abstr MEDI 55.
`Lefkowitz, R. J. Annu. Rep. Med. Chem. 1980,15, 217. PI and
`Pz: Evans, D. B.; Fox, R.; Hauck, F. P. Ibid. 1979, 14, 81.
`Leclerc, G.; Rouot, B.; Velly, J.; Schwartz, J. Curr. Rev.
`Biomed., 1981,1, 78. Smith, L. H. J. Appl. Chem. Biotechnol.
`1978,28, 201. O’Donnell, S. R.; Wanstall, J. C. Life Sci. 1980,
`27,671. a1 and a2: Hoffman, B. B.; Lefkowitz, R. J.; N . Engl.
`J. Med. 1980,302,1390. McGrath, J. C. Biochem. Pharmacol.
`1982, 31, 467.
`Beilin, L. F.; Juel-Jensen, B. E. Lancet 1979, 1, 979.
`Frishman, R.; Silverman, R.; Strom, J.; Elkayam, U.; Sonnen-
`blick, E. Am. Heart J. 1979, 98, 256.
`Baldwin, J. J.; Lumma, W. C., Jr.; Lundell, G. F.; Ponticello,
`G. S.; Raab, A. W.; Engelhardt, E. L.; Hirschmann, R. J. Med.
`Chem. 1979,22, 1284.
`* Merck Institute for Therapeutic Research.
`Bragden, R. N.; Heel, R. C.; Speight, T. M.; Avery, G. S. Drugs
`1978, 15, 251.
`0022-2623/83/l826-0649$01.50/0 0 1983 American Chemical Society
`
`Merck Sharp & Dohme Research Laboratories.
`
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`
`650 Journal of Medicinal Chemistry, 1983, Vol. 26, No. 5
`(4),9 all of which bear aralkylamino groups but belong to
`the ethanolamine class. In this article, we describe the
`effect of such aralkylamino substitution in the oxy-
`methylene class of @-adrenergic blocking agents. In ad-
`dition, the influences of chirality on the relative affinities
`(DHA, p), the [3H]clonidine
`for the [3H]dihydr~alpren~lol
`(az), and the [3H]WB-4101 (cy1) or [3H]prazosin (a1)
`binding sites were determined.
`Chemistry. The compounds summarized in Table I
`were synthesized by one of two general methods. The first
`involved the reaction of various amines with (RS)-, (R)-,
`or (5')-cyanopyridyloxymethyloxiranes (5) (Scheme I;
`method A). These intermediate epoxides were obtained
`from the respective glycidols and 2-chloro-3-cyanopyridine
`(6).1° The second approach (method B) involved the
`reaction of 2-chloro-3-cyanopyridine (6) with the N-sub-
`stituted (RS)-, (R)-, or (S)-substituted-glycolamines pro-
`tected as their benzaldehyde oxa~olidines.~J~ Although
`the schemes show the synthesis of enantiomers only, the
`sequences were also applicable to the preparation of the
`corresponding racemates.
`In addition, the presence of the 1-methyl-3-phenyl-
`propylamino and related chiral groups in 2-4 resulted in
`diastereomeric mixtures, which presented complications
`with regard to the interpretation of biological results. Two
`approaches were considered to resolve this problem in the
`study of the analogues of 1; the first involved the prepa-
`ration of the four individual isomers, while the second
`focused on the elimination of the chiral center associated
`with the amino component through the utilization of 1,l-
`dimethyl-3-phenylpropylamino and related achiral sub-
`stituents. In order to evaluate the structure-activity re-
`lationships in the example bearing the l-methyl-3-
`phenylpropylamino substituent (28), the individual isomers
`were prepared. The ready availability of both (R)- and
`(S)-5 and the utilization of the resolved l-methyl-3-
`phenylpropylamine (8)l2 allowed for the direct synthesis
`of the individual isomers.
`
`&"2
`
`8
`
`The resolution of 8 has been reported,12 but some con-
`fusion exists as to the assignment of the absolute config-
`
`Sybertz, E. J.; Sabin, C. S.; Pula, K. K.; Vander Vliet, G.;
`Glennon, J.; Gold, E. H.; Baum, T. J. Pharmacol. Exp. Ther.
`1981, 218, 435. Baum, T.; Watkins, R. W.; Sybertz, E. J.;
`Vemillapelli, S.; Pula, K. K.; Eynon, E.; Nelson, S.; Vander
`Vliet, G.; Glennon, J.; Moran, R. M. Ibid. 1981, 218, 444.
`Grisar, J. M.; Claxton, G. P.; Bare, T. M.; Dage, R. C.; Cheng,
`H. C.; Woodward, J. K. J. Med. Chem. 1981,24,327. Cheng,
`H. C.; Reavis, 0. K., Jr.; Grisar, J. M.; Claxton, G. P.; Weiner,
`D. L.; Woodward, J. K. Life Sei. 1980, 27, 2529.
`Hernandez, P. H.; Lape, H. E.; Philion, R. E. Fed. Roc., Fed.
`Am. SOC. Exp. Bid. 1979, 38, 738. Benziger, D. P.; Fritz, A.;
`Edelson, J. Drug Metab. Dispos. 1981, 9, 493.
`McClure, D. E.; Engelhardt, E. L.; Mender, K.; King, S.; Saari,
`W. S.; Huff, J. R.; Baldwin, J. J. J. Org. Chem. 1979,44, 1826.
`Weinstock, L. M.; Mulvey, D. M.; Tull, R. J. Org. Chem. 1976,
`41, 3121.
`(a) van Dijk, J.; Keizer, V. G.; Mold, H. D. Recl. Trau. Chim.
`Pays-Bas 1963, 82, 189. (b) Cannata, V.; Samori, B.; Tra-
`montini, M. Tetrahedron 1971, 27, 5247. (c) Cervinka, 0.;
`Kroupova, E.; Belovsky, 0. Collect. Czech. Chem. Commun.
`1968, 33, 3551. (d) Potapov, V. M.; Dem'yanovick, V. M.;
`Teret'ev, A. P. Zh. Obshch. Khim. 1965,35,1538; Chem. Abstr.
`l965,63,17854h. (e) Yamamoto, Y.; Oda, J.; Inouye, Y. Bull.
`Chem. Jpn. 1975,48, 3744.
`
`McClure et al.
`urations12 due to the change of sign between chirally pure
`free bases [(R)-8, [ a ] ~
`(c = 1, cyclohexane)]12b and
`-18'
`the corresponding hydrochloride salts [ (R)-&HCl, [ a ] D +
`13' (c = 1, HzO)].12b Following the reported procedure12a
`for the resolution of 8 via the mandelic acid salt, (+)-8
`+15.8' (c = 1.23, cyclohexane)] and (-)-8 [[a]."~
`[[.Iz5D
`-14.9'
`(C = 0.996, cyclohexane)] were obtained. Reaction
`of chiral8 with (R)- or (S)-5 resulted in the formation of
`each of the individual isomers (40-43, Table 11).
`In order to unambiguously determine the absolute
`configurations of 40-43, the amides derived from 1-
`methyl-3-phenylpropylamine (8) and (S)-0-methyl-
`mandelic acid were separated by HPLC and one of these,
`the S,S isomer, was subjected to single-crystal X-ray
`ana1y~is.l~ This determination also confirmed the as-
`signment of the absolute configuration as @)-(-)-& as
`assigned in ref 12b,d,e.
`The diastereomeric purity of 28 and 40-43 was estab-
`lished by NMR techniques. The methyl region in the 'H
`NMR exhibited two doublets of about equal intensity in
`28, and several of the 13C peaks also showed doubling in
`28 indicative of an approximately 1:l diastereomeric com-
`position. On the other hand, none of the pure isomers
`(40-43) indicated the presence of any of these doublings
`by lH NMR and/or 13C NMR. Thus, the maximum dia-
`stereomeric contamination in any of these samples was
`1 5 % . The evaluation of pure isomers rather than mix-
`tures, as was done with medroxalol,* avoided potential
`problems in interpretation of results. These NMR tech-
`niques were also used to ascertain that the diastereomeric
`mixtures shown in Table I were approximately 1:l mix-
`tures of the expected diastereomers (29, 33-39).
`The enantiomeric purity of the compounds in Table I
`was taken to be 198%. This conclusion stemmed from
`the analysis of the NMR spectra of the precursor epoxides,
`(R)- or (S)-5,lo and several of the compounds in Table I
`(25, 27, 31, 32) in the presence of a chiral shift reagent,
`Eu(hfbc),.lo In all cases examined, none of the opposite
`enantiomer was detected, indicating a chiral purity of
`198%.
`Pharmacology. Since the blockade at both a- and
`@-adrenergic receptors could be important in the phar-
`macology of 1, the various N-substituted derivatives were
`assessed by receptor-binding techniques in isolated mem-
`brane preparations by using [3H]WB-4101 (a1) and [3H]-
`dihydroalprenolol (DHA, @) as radioligands (Table 111).
`The acute antihypertensive effect was also evaluated in
`the spontaneously hypertensive rat (SH rat, Table IV).
`Additional in vivo studies in anesthesized dogs were also
`performed on selected compounds to determine a- and
`@-adrenoceptor blockade in a whole animal model (Table
`VI).
`Since alteration of the amino substituent usually pro-
`duced relatively minor changes in P-receptor affinity, these
`derivatives of the highly potent @-adrenoceptor antagonist
`1 would be expected to exhibit relatively low KI values vs.
`[3H]DHA (Table 111). All of the compounds were rather
`potent at displacing [3H]DHA from rat neocortical mem-
`brane homogenates, although only a few (27, 28, 31, 34)
`approached the affinity of 1. When comparisons were
`made between S enantiomers and their corresponding
`racemates (24, 25; 26, 27; 30-32; 33, 34), the S isomers
`
`(13) The HPLC separation of the amides was accomplished by Y.
`Girard, M. Larue, J. Rokach, and J. Atkinson at Merck Frosst
`Canada, Inc., in Montreal. J. Hirshfield in our Rahway labo-
`ratories was responsible for the solution of the X-ray crystal
`structure. We are indebted to these co-workers for their re-
`sults, the details of which will be reported in the near future.
`
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`
`Antihypertensive P-Adrenergic Blocking Agents
`
`exhibited affinities higher than, or at least equal to, the
`respective racemate as would be expected for oxy-
`methylene @-adrenoceptor antagonists.14
`The potential of these compounds for a,-adrenergic
`receptor blockade was evaluated via the radioligand dis-
`placement of [3H] WB-4101 from calf neocortical mem-
`brane homogenates, and the dissociation constants (KI’s)
`were calculated (Table 111). Even though this ligand
`showed biphasic displacement curves,15 it was still selective
`for the a, adrenoceptor, and it provided comparative data
`for mechanistic consideration. For the isomeric 1-
`methyl-3-phenylpropylamino analogues (28, 40-43), the
`more specific a, radioligand, [3H]prazosin, was emp10yed.l~
`Both 1 and the alkylamino analogues 10-19 showed a
`very low affinity, i.e., high KI values, for the displacement
`of [3H]WB-4101 from a,-adrenoceptors. Compound 19
`bearing a 4-tert-butylcyclohexylamino substituent had the
`highest affinity for the a, adrenoceptor in this series (KI
`= 400 nM). The aralkylamino analogues (20-39) repre-
`sented a demarcation in pharmacological profile; most
`possessed KI’s ranging from 18-380 nM against [3H] W-
`B-4101. The most active compounds in this series (27,28,
`33,34, 36) and labetalol(2) exhibited similar affinities for
`a,-adrenergic receptors. Thus, the presence of an N-ar-
`alkylamino group induced an interaction with the a1
`adrenoceptor, yielding compounds that showed potencies
`up to 500 times greater than 1 and related alkylamino
`analogues with the only exception being 19. The most
`obvious aralkylamino exception to this rule was the indanyl
`derivative 22; reduction of flexibility may be a causative
`factor in this result.
`Comparisons of pure enantiomers and the corresponding
`racemates (24, 25; 26, 27; 30-32; 33, 34) suggested that
`structural features other than chirality at the secondary
`hydroxy center were much more important in determining
`the al-adrenergic receptor binding characteristics. In some
`cases the R enantiomer showed a higher affinity (24,25;
`30-321, while in others the isomer with higher affinity had
`the S configuration (26, 27; 28, 40-43). Comparisons of
`pure enantiomers and the corresponding racemates (24,
`25; 26,27; 30--32; 33,34) indicated that the antihyperten-
`sive activity (Table IV) was not highly dependent upon
`the chirality at the secondary hydroxy center, which was
`in agreement with the low chiral influence found in the
`radioligand displacement studies. Although the influence
`of chirality on a-adrenoceptor affinity in the related eth-
`
`anolamine class had been previously p r ~ b e d , ~ a the mix-
`tures of isomers used in the study of the medroxalol iso-
`mer@ complicated the interpretation of these results, while
`detailed pharmacology was presented on only one of the
`isomers of labetalol (R,R isomer, SCH 19927).7 The ar-
`alkylamino derivatives of 1 provided the first documen-
`tation within the oxymethylene class for the importance
`of chirality at the alcohol center on @-adrenoceptor, but
`not a,-adrenoceptor, affinity. Patil et al.14 had earlier
`suggested that such may be the case for various a- and
`@-adrenoceptor antagonists.
`None of the alkylamino-substituted analogues (2, 10-19)
`showed an antihypertensive potency comparable to 1
`(Table IV) in the SH rat. In contrast, most of the aral-
`kylamino analogues (20-39) exhibited acute antihyper-
`tensive activity with a potency somewhat less than the
`standard 1. Since @-adrenergic antagonists generally ex-
`hibited only modest acute antihypertensive effects,16 it was
`
`(14) Patil, P.; Miller, D.; Trendelenberg, U. Pharmacol. Reu. 1974,
`26, 323.
`(15) Lyon, T. F.; Randall, W. C. Life Sci. 1980, 26, 1121.
`
`~~
`
`Journal of Medicinal Chemistry, 1983, Vol. 26, No. 5 651
`attractive to postulate that the observed antihypertensive
`response in compounds other than 1 resulted from a,-
`adrenoceptor blockade. Upon analysis, a statistically
`significant correlation was found between antihypertensive
`activity in the SH rat and in vitro &,-binding affinity.17
`Compounds in the group 20-39 for which there was data
`available (21-32, 34, 37) were used to construct a plot of
`in vitro a,-adrenoceptor affinity (log KI vs. [3H]WB-4101)
`vs. antihypertensive activity in the SH rat at an oral dose
`of 5 mg/kg, giving a correlation coefficient of 0.673.17
`Although statistically significant, this correlation was not
`a particularly good one, and other mechanisms may con-
`tribute to the observed antihypertensive response. Since
`1 was a potent antihypertensive agent6 via a mechanism
`that did not involve a-adrenoceptor blockade, these ar-
`alkylamino analogues may also reduce blood pressure by
`mechanisms other than a-adrenergic receptor antagonism.
`This was somewhat similar to the results observed with
`the isomers of medroxaloP and labetalol,’ i.e., the isomers
`exhibited similar antihypertensive activity in the SH rat
`while showing widely different a-adrenoceptor blocking
`properties in vitro. In these cases a statistically significant
`correlation was not observed, perhaps due to the much
`smaller sample size of their studies. Of course, the ab-
`sorption, distribution, and metabolism of drugs may also
`complicate the interpretation of any comparisons of in vivo
`and in vitro responses.
`Based on high cy1- and @-adrenoceptor affinities in ra-
`dioligand displacements, the diastereomeric mixture 28 was
`a prime candidate for further pharmacological study. It
`was of interest to prepare and evaluate each of the four
`isomers to determine the influence of chirality on the
`pharmacological profile. While the S configuration at the
`alcohol center had been well established as the biologically
`active isomer in the aminohydroxypropoxy class of @-ad-
`renergic blocking agents,14 the influence of chirality on
`a,-adrenergic receptor blockade has been only recently
`described in the ethanolamine class with the isomers of
`labetalo17J6 and medroxalol.8 The configuration at the
`hydroxy carbon in the potent (S)-oxymethylene class of
`0 blockers corresponds to the R configuration in the eth-
`anolamine class, each of which corresponds to the absolute
`configuration found in (R)-norepinephrine.
`The displacements of various radioligands from mam-
`malian cerebral cortex membrane homogenates allowed for
`the determination of KI values at a- and @-adrenergic re-
`ceptors for the four isomers (40-43, Table v). In addition
`to [3H]WB-4101 as the a,-adrenoceptor ligand, the dis-
`placements of [3H]prazosin (an a,-selective ligand) and
`L3H]clonidine (an a,-selective ligand) were also examined
`in the binding studies. Since [3H]prazosin appeared to be
`more selective for the a,-adrenoceptor and to give mono-
`phasic displacement curves,15 the al results presented were
`derived from its displacement. Each isomer displaced
`clonidine with KI’S greater than 1 pM, values much greater
`
`than those obtained from the [3H]praz~~in studies. Thus,
`these isomerically related compounds were all selective for
`the a,-adrenoceptor. Ratios range from -25 for the least
`selective compound (43) to -135 for the most selective
`
`(16) Watson, L. S.; Ludden, C . T. “New Antihypertensive Drugs”;
`Scriabine, A.; Sweet, C. S., Eds.; Spectrum Publications:
`Holliswood, NY, 1976; p 227.
`(17) We thank a referee for pointing out that this correlation with
`12 degrees of freedom was statistically significant. See George
`W. Snedecor and William G. Cochran, “Statistical Methods”,
`7th ed., The Iowa State University Press: Ames, IA, 1980.
`(18) Nakagawa, Y.; Shimamoto, N.; Nakazawa, M.; Imai, S. Jpn. J.
`Pharmacol. 1980, 30, 743.
`
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`
`652 Journal of Medicinal Chemistry, 1983, Vol. 26, No. 5
`
`McClure et al.
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`

`
`Antihypertensive P- Adrenergic Blocking Agents
`
`Journal of Medicinal Chemistry, 1983, Vol. 26, No. 5 653
`
`N
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`

`
`654 Journal of Medicinal Chemistry, 1983, Vol. 26, No. 5
`
`McClure et al.
`
`Table 11. 2-[3-[( l-Methyl-3-phenylpropyl)amino]-2-hydroxypropoxy]-3-cyanopyridine Maleate Isomers (C,,H,,N,O,~C,H,O,)
`
`FH3
`
`CN a0-p/,
`
`chirality
`,CH3
`- CH
`'CH,CH,C~H~
`R S
`R
`R
`S
`S
`
`CHzCHzC6H5
`
`OH
`
`method
`A
`A
`A
`A
`A
`
`yield,
`%
`38
`31
`43
`47
`47
`
`crystn solvent
`i-PrOH
`i-PrOH-Et,O
`i-PrOH-Et,O
`i-PrOH-Et,O
`i-PrOH-Et,O
`
`mp, "C
`117-118
`110-112
`113-115
`112-114
`105-108
`
`anal.
`[a]"n, deg (c, solv)
`-0.42 (1.185, MeOH)
`C, H, N
`-6.32 (1.06, MeOH)
`C, H, N
`t 17.64 (1.015, MeOH) C, H, N
`-18.19 (1.035, MeOH) C, H, N
`t4.91 (1.05, MeOH)
`C, H, N
`
`compd
`-CHOH-
`R,S
`28
`40
`S
`41
`R
`42
`S
`-
`43
`R
`Inhibition of [3H]WB-4101 and [,HIDHA
`Table 111.
`Bin ding to Mammalian Neocortical Membranes
`&,-receptor
`chirality: KI,b nM, for
`-CHOH-
`[3H]WB-4101
`9000 * 2000
`S
`S
`7000 f 1000
`R,S
`R,S
`S
`S
`S
`S
`S
`S
`R,S
`S
`S
`S
`R,S
`R S
`S
`R S
`S
`R,S
`R,S
`R S
`S
`R
`R,S
`S
`R,S
`R,S
`R S
`R S
`R S
`
`p-receptor
`K I , ~ nM, for
`compd
`[3HlDHAa
`0.68 f 0.10
`1
`1.90 * 0.57
`10
`11.7 f 3.0
`11
`255 + 40
`12
`60.1 f 2.5
`6000f 1000
`13
`11.6 f 6.9
`6000f 2000
`14
`28.9 f 6.2
`3100f 500
`15
`7000 f 2000
`67.1 f 2.0
`16
`60001: 2000
`1.99 + 0.09
`17
`7000 + 2000
`31.5 f 3.2
`18
`7.16 f 2.0
`400f 60
`19
`89f 9
`38.5 f 3.9
`20
`6.85 f 0.36
`210f 10
`21
`5.03 f 1.5
`1 O O O f 100
`22
`1.54 f 0.28
`72* 3
`23
`4.82 f 1.0
`125 f 9
`24
`5.72 f 1.5
`190f 20
`25
`1.90 f 0.19
`8 4 f 9
`26
`1.40 f 0.0
`6 0 * 10
`27
`1.45 + 0.36
`6 3 f 5
`28
`8.90 + 1.0
`160+ 20
`29
`2.38 f 0.42
`120f 10
`30
`280 + 20
`1.40 f 0.41
`31
`110 f 20
`9.41 f 2.3
`32
`1.88 f 0.14
`4 0 * 10
`33
`18f 7
`0.58 f 0.22
`34
`14.4 f 1.9
`2301: 20
`35
`2.49 f 0.15
`51+ 7
`36
`7.01 + 1.7
`73f 5
`37
`6.16 f 1.4
`180 f 10
`38
`6.41 + 1.9
`380 f 40
`39
`7 4 + 9
`19.2 f 2.2
`2 (labetalol)
`The results are
`~~~ a [3H]DHA = [3H]dihydroalprenolo1.
`SD for two or more separate determinations.
`the mean
`The results are the mean * SD for three or more separate
`determinations.
`compound (40) when [3H]clonidine (ap) displacement was
`compared with the results using [3H]prazosin (a1). The
`S isomers at the hydroxy center (40, 42) showed greater
`affinities for both the al- and @-receptors than did the
`corresponding isomeric (R)-alcohols (41, 43). It was in-
`teresting to note that the chirality at each asymmetric
`carbon was worth about 0.5 kcal/center (Table V); the best
`bound S,R isomer (40), which showed the highest affinity
`vs. [3H]prazosin, had a free energy of binding almost 1
`kcal/mol greater than the lowest affinity R,S isomer (43).
`Although free-energy differences of this order could be
`important in overall drug action, they were small compared
`to the overall free energies for binding. These values were
`also small when one considers the importance of chirality
`at the @-adrenergic re~ept0r.l~ The S chirality at the hy-
`
`droxy center led to an approximately tenfold increase in
`affinity for the @adrenergic receptor when compared to
`the corresponding R enantiomers (40 vs. 41, 42 vs. 43),
`amounting to a thermodynamic preference of 1.3 or 1.5
`kcal/mol for either S isomer.
`The most interesting compounds having KI (a1) < 100
`nM and KI (0) < 10 nM were examined in anesthetized
`dogs in order to assess their a- and @-adrenoceptor
`blockade in a whole animal model (Table VI). However,
`it should be emphasized that these results are only pre-
`liminary. The a-adrenergic receptor blocking activity of
`these compounds was established by their antagonism of
`phenylephrine-induced increase in arterial pressure, while
`their antagonism of isoproterenol-induced tachycardia
`allowed for a determination of the @-adrenoceptor block-
`ade. In general, the trends observed in the anesthetized
`dog in terms of a,@-adrenoceptor blockade followed those
`found in the al- and @-radioligand displacement studies.
`The most interesting compounds in this series were equal
`to, or slightly more potent than, labetalol (2) as a-antag-
`onists and substantially more potent than labetalol as
`@-antagonists (Tables 111, V, and VI). The effect of such
`an increase in @-adrenoceptor affinity without change in
`the a-adrenoceptor potency increased the separation be-
`tween the two activities.
`From the KI values of [3H]WB-4101, it can be concluded
`that the vasodilation exhibited by 1 was not due to an
`interaction with the al-adrenoceptor; the mode by which
`1 produced vasodilation is, therefore, still an open question.
`The introduction of an aralkylamino substituent into the
`P-blocking side chain of 1 led to a series of compounds
`showing in vitro and in vivo a-adrenergic receptor binding
`properties. With the dual-acting a,@-adrenergic blocking
`agents from this series as well as labetalol' and medrox-
`dol: the chirality at the hydroxy center made only a minor
`contribution to the affinity for the a,-adrenoceptor and
`even less of a contribution to the observed antihypertensive
`effects.
`Experimental Section
`Optical rotation measurements were obtained on a Perkin-
`Elmer 141 polarimeter. NMR spectra were determined in the
`indicated solvent on a Varian T-60 or EM-390 with tetra-
`methylsilane as Buchi internal standard for proton spectra.
`Chemical shifts are given in 6 units, and coupling constants are
`in hertz. Splitting patterns are designated as follows: s, singlet;
`br s, broad singlet; fs s, finely split singlet; d, doublet; t, triplet;
`q, quartet; p, pentet; m, multiplet. Chiral shift NMR analyses
`were conducted on a Varian SC-300 operating in the FT mode.
`Other high-field NMR spectra were obtained on either a Varian
`SC-300 or a Nicolet NT-360 spectrometer, and I3C NMR spectra
`were obtained on a Varian CFT-20 instrument. Melting points
`were determined on a Thomas-Hoover apparatus, in open capillary
`tubes, and are uncorrected. Microanalyses are within 0.4% of
`
`LOWER DRUG PRICES FOR CONSUMERS, LLC
`Exhibit 1037-6
`IPR2016-00379
`
`

`
`Antihypertensive ,&Adrenergic Blocking Agents
`
`Journal of Medicinal Chemistry, 1983, Vol. 26, No. 5 655
`
`compd
`1
`
`1 0
`
`11
`1 2
`13
`14
`
`15
`
`16
`17
`
`18
`
`19
`20
`
`21
`
`22
`
`23
`
`24
`
`25
`
`26
`
`27
`
`28
`
`29
`
`30
`
`Table IV. Comparative Effect of Compounds on Arterial
`Pressure of Spontaneously Hypertensive Rats
`max fall
`in MAP,
`no. of
`route SHR mmHgf SE
`4
`4 7 * 5
`3 0 f 4
`8
`4
`1 9 * 2
`3
`57 f 1 2
`2
`4
`1 5
`2
`2
`1 6
`17
`2
`2
`24
`2
`1 4
`8
`39 f 1 0
`8
`2 2 i 4
`1 2 * 5
`6
`2
`20
`2
`42
`31
`2
`2
`30
`2
`1 0
`2
`45
`2
`40
`2
`11
`2
`38
`2
`20
`2
`11
`2
`33
`2
`1 3
`2
`67
`2
`32
`3
`171- 7
`2
`4 3
`0
`2
`2
`39
`2
`30
`3
`2 0 % 1
`2
`61
`2
`38
`4
`2 7 f 5
`4
`5 0 f 1 3
`5
`2 8 * 9
`4
`2 1 f 4
`3 8 f 6
`6
`4
`2 6 i 5
`2
`1 6
`2
`40
`2
`29
`2
`8
`2
`54
`2
`38
`2
`24
`2
`26
`2
`4
`2
`37
`2
`41
`4
`2 4 5 5
`2
`17
`2
`70
`4
`73 f 1 6
`2
`57
`71
`2
`3
`8 4 f 6
`2
`38
`3
`58 f 9
`2
`48
`3 6 * 9
`4
`2
`29
`2
`50
`4
`3 8 f 11
`3
`21 f 1
`4
`2 * 1 6
`
`dose,
`mg/kg
`1.25
`0.312
`0.078
`5.0
`0.312
`20.0
`20.0
`20.0
`20.0
`5.0
`20.0
`5.0
`1.25
`20.0
`20.0
`5.0
`20.0
`5.0
`20.0
`20.0
`20.0
`5.0
`1.25
`0.312
`20.0
`5.0
`5.0
`1.25
`0.312
`5.0
`1.25
`5.0
`1.25
`0.312
`20.0
`20.0
`5.0
`5.0
`1.25
`0.312
`5.0
`1.25
`0.312
`20.0
`5.0
`1.25
`20.0
`5.0
`1.25
`0.312
`0.078
`5.0
`1.25
`0.312
`0.078
`20.0
`5.0
`20.0
`5.0
`1.25
`20.0
`20.0
`20.0
`5.0
`20.0
`20.0
`20.0
`5.0
`1.25
`
`filtered, and the filtrate was concentrated to dryness on a Buchi
`rotary evaporator under water-aspirator pressure (20 mm).
`Method A General Procedure. Reaction of the appropriate
`epoxide 51° with 1.0-2.0 molar equiv of the required amine was
`accomplished by heating neat in an oil bath at 6G-70 "C overnight.
`Chromatography on silica gel 60 by eluting with 2-4%
`CH30H/CHC13 or CHzClz separated the desired product from
`excess residual amine. Salt formation, followed by recrystalli-
`zation, gave the compounds listed in Tables I and 11. The
`preparation of (S)-2- [ 3- [ (1 ,l-dimethyl-3-phenylpropyl)amino] -2-
`hydroxypropoxy]-3-~yanopyridine maleate (27) is given as an
`example.
`A stirred mixture of (S)-5 (3.52 g, 0.02 mol) and 1,l-di-
`methyl-3-phenylpropylamine (3.3 g, 0.02 mol) was heated in an
`oil bath at 60 "C overnight. The mixture was chromatographed
`on -250 g of silica gel 60 by eluting with 3% CH30H/CHC13.
`After isolation of the appropriate fractions, the maleate salt was
`prepared in 2-propanol. Recrystallization from 2-propanol gave
`27 (24.0%): mp 151-153 "C; lH NMR (Me2SO-d6) 6 1.4 (6 H, s),
`1.9 (2 H, m), 2.6 (2 H, m), 3.2 (2 H, m), 4.3 (1 H, m), 4.5 (2 H,
`d), 6.1 (2 H, s), 7.3 (6 H, m), 8.3 (1 H, dd), 8.5 (1 H, dd).
`2-[3-[ [ l,l-Dimethyl-2-(4-hydroxyphenyl)ethyl]amino]-2-
`hydroxypropoxy]-3-~yanopyridine Hydrochloride (23). For
`solid, high-melting amines the following procedure was employed.
`The epoxide (RS)-51° (1.41 g, 0.008 mol) and l,l-dimethyl-2-(4-
`hydroxypheny1)ethylamine (1.37 g, 0.008 mol) were dissolved in
`CH3CN (20 mL) and H,O (5 mL). This mixture was stirred at
`room temperature for 1 week. After concentration, the residue
`was taken up in CHzC12 and washed with H20. Drying and
`concentration gave the crude product, which was chromatographed
`on -200 g silica gel 60 by eluting with NH3 saturated 5%
`CH3OH/CHCl3 The HC1 salt was prepared in 2-propanol/ether.
`Recrystallization from 2-propanol/ether gave 23 (37.0%): mp
`193-196 "C; 'H NMR (Me2SO-d6) 6 1.3 (6 H, s), 2.9 (2 H, br s),
`3.3 (2 H, m), 5.5 (3 H, br s), 6.7 (2 H, d), 7.1 (2 H, d), 7.2 (1 H,
`dd), 8.2 (1 H, dd), 8.4 (1 H, dd).
`Method B General Procedure. Reaction of the oxazolidine
`alcohols [(RS)- or (S)-7], prepared as previously described,5J1 with
`NaH in DMF formed the sodium alkoxide. To this mixture was
`added 2-chloro-3-cyanopyridine, and the reaction was stirred
`overnight. Acid-catalyzed hydrolysis of the oxazolidine ring gave
`the desired products. The preparation of (S)-2-[3-[(3-methyl-
`butyl)amino]-2-hydroxypropoxy]-3-cyanopyridine maleate ( 13)
`is given as an example.
`To (S) -2-phenyl-3- (3-methylbutyl) -5- (hydroxymethyl) oxazo-
`lidine [(S)-7, R = (CH3)zCHCHzCH2; 6.01 g, 0.024 mol] in DMF
`(50 mL) was added NaH (1.16 g, 50% oil dispersion, 0.024 mol)
`in portions. After heating on a steam bath for 15 min, the mixture
`was cooled for 1 h prior to the addition of 2-chloro-3-cyanopyridine
`(3.34 g, 0.024 mol). After stirring overnight, the mixture was
`poured into 100 mL of ice-water and extracted with ether (4
`times). The combined ether extracts were washed with water.
`The basic materials were extracted into 1.5 N HCl (2 X 50 mL)
`and H20 (1 x 100 mL), and the combined aqueous acidic extracts
`were heated on a steam bath for 0.5 h. After cooling, the mixture
`was washed with benzene (4 times). The aqueous phase was then
`basified by adding solid Na2C03 with ice cooling. Extracting with
`ethyl acetate, drying, and concentrating gave the crude product.
`The maleic acid salt was prepared in ethanol/ether. Recrys-
`tallization from ethanol/ether gave 13 (47.2%): mp 95-98 "C;
`'H NMR (Me2SO) 6 0.9 (6 H, d), 1.5 (3 H, m), 3.0 (4 H, m), 4.3
`(3 H, m), 6.0 (2 H, s), 7.2 (1 H, dd), 8.3 (1 H, dd), 8.5 (1 H, dd).
`Pharmacology. a-Adrenergic Receptor Binding Assays.
`[3HlPrazosin was obtained from Amersham Corp. at a specific
`activity of 33 Ci/mmol. [3H]Clonidine and [3H] WB-4101 were
`obtained from New England Nuclear Corp. at specific activities
`of 23.8 and 25 Ci/mmol, respectively. Radiochemical purity of
`each radioligand was periodically determined by thin-layer
`chromatography by using conditions recommended by the man-
`ufacturers.
`The radioligand displacement assays involved incubating a fied
`concentration of the radioligand with calf cerebral cortical
`membrane suspensions in the presence of five triplicate concen-
`t