JAMESAND WILLIAMS
670 Journal of Medicinal Chemislry, 1971, Val. 14,No. 8
variation in the activity of a set of congeners. For example, in a set of neutral congeners having log Po of 5.5 and a dependence of activity on log P of 0.6 (slope) in the linear relation between log 1/C and log P , the difference in activity of derivatives of log P = 0 and log P = 5 will be 3 log units. Unless this large variation in activity can be separated in structureactivity relationship discussions, it is quite difficult to begin t o mechanistically classify different functional groups, especially when one gets beyond simple homologous series. How valuable such scales as that in
Table I11 will ultimately be will not be known until more extensive studies have been made. Acknowledgment.-We \vis11 to thank Miss Catherine Church (Smith Kline and E'rench research associate), Dr. William Glave, Dr. William D u m , and Mr. David Soderberg for determining a number of the partition coefficients employed in this uork. We thank Dr. Paul Craig of Smith Kline and 1:rench for the pK, of N-2-hydroxj.et hylimidazoline.
Crystal Structure of dl-Brompheniramine Maleate
[l-(p-Bromophenyl)-l-(2-p~ridyl)-3-N,N-dimeth~lpropylamine maleate] 11. S.G. JAMES A N D G . J. €3.
U-ILLIAMS
Dcpnrtnienl of Bzochemislry, T h e I.niversity of Alberta, Edmonton, Alberta, Canada Kecewed January 6 , 1 9 ? 1
B,
l t a c e ~ i ot)roniphetiiraniitie maleate crystallizes iti space group 1'21,'~with a = 9.863 0 = 10.836 A, c = 13 = 115.83". The crystal structure was solved by convetitiorial Patterson and Fourier techniques mid refined by least square5 to weighted and unweighted IZ factors of 6.3i atid 4.55c&, respectively. The propylamine chain is fkilly extended atid adopts an asymmetrical dispoiition with respect to the 2 aryl moieties. The p-bromobei~ylgroup ia partially occluded by the asymmetry and the 2-pyridyl ring is exposed, thus giving the molecrile ail open side. The maleic acid is i n the nioiioaiiion form atid is H bonded to the YlIe2 group. Molec.ular pwanieters are close to expected values with the exception of the location of the second ba2e dissociable proton of the maleate, which is engaged in a very short asymmetric iiitraiori H bond of length 2.415 -4. 21.494 A , and
Tlic aiiti1iist:imiiiic drugs as a cl wert their :ictioii bj. successful competition with histaniiiic for the :illergic ( H l ) receptor site on the walls of smooth muscle tissue.' The title compound is :1 potciit histamine :iritagoiiist and, because receptor sites arc difficult to study directly, it \\-as thought that uscful iriformatioii regarding molecular conformations of :intihist:imiriic drugs could be obtained by defining t h e structurc of this effector molecule. Thc structure of histamhe has recentlj, been complet cd by t w o independent groups? and, more recently, one of these groups has published their preliminary results of the first X-ray study of :in ,, I h p present ivorl; u x s begun in an attempt to delineate sonic of the seemingly relevant structural parameters for :intihist:iminic action. It is reasonable to suppose that if the, :ititihistamiiie acts :is a competitive inhibitor of 1iist:imine then there should be some points of sigiiific:int structur:il similarity between them. In particulnr it secmcd jmportunt t o know if the S-S dist:iip in brompherii mine vas comparable to the 3.%-A (list :iI ice Iingle bond, th:tt C(1)-O(1) (1.209 . ~ ) o c o r r e spoiids to a double bond and that the C ( 4 ) - 0 ( 3 ) (1.26.5 .\) :t~ld bonds are of intermediate order.*" If i t is :tcC(4 )-O(4) (1.230 cepted that the €I is indeed between the t w o oxygen3 thzn these distances are compelling evidence fur a c.i)valerit i i . c . , 1.0 >L)bond rcb-
Figure .?.-The viewh of the maleate ion and the N atom to which i t ib H bonded. .4toniic coding here iy consistent with that of Figure- 3 and 4 . puiuids t o bind similarly to the 111 site it is almost certain that, they do not, since the outcome of the site-effector molecule iiiteractioii is qiiite different in the two cases. The various diagrams of this paper show that the N,N-dimethy1pro~~ylamiiiostrricatiiral feature is frilly extended and :idopts a11 asymmetric. miforination with respect to the two :wyl groups. The asynimel r i d dispositioii of the alkylamiiie chain may be desrribed by three parameters; the distance of the saturated K from the centroid of the pyridyl ring of 6.212 A, the angle betweeii this ring and the basal plniie of the "N pyramid" [defined by the atoms C(9), C, CIJ of 34' *57',and the angle between the C(7)-N(1) vector and the normal to the plane of the pyridyl i,ing of 59"; corresponding figures for the benzene ring are 5.368 .I, 71' 20', and 105". I t may be thought that close Van der \+"Is contacts could be responsible for the molecular dissymriletry, but neither an extensive search through lists of computed iiiter:itomic distances nor n close examination of a space-filling (~ci~~ey-Paiiliiig-Kolt~in niolecular model has revealed any such iiitei,actioii. The conclusion then is that the solid-state conformal ion is probably that predominating in solution and that i t i,rflec.ts some iiitrinsic property of the species. If this viewpoint is accepted, the open-sided nature of this cuiiform:itioii becomes more meaningful and it can be correlated very nicely with the suggestions of Barlowl regarding the binding o f the pheiiiramiries and of triprodiline to the receptor site. The c~cinforination of this latter compound is not known with any reliability and we have begun a crystallographic study of it in older to gain more informatioii about histamine antagonists. The preliniiiiary crystallographic data on trip~olidine.HCloare as follow>: space group is Z21,fc, a = 14.91 A, b = 9.66 A, c = 1:3.22",p = 90.3", pmctt.= 1.20 g/cma, pealoLi for 4 formula units { i f Cl~I12aONsCl,!cell = 1.18 g/c.m".
(16) "Handbook of Chemistry and Physics," R . C . IVeast, Ed.. 49th elf, Chemical Rubber Co., Cleveland, Ohio, 1969, p 90. (17) H. h l . E. Cardrvell, J . D. Dunita, and L. E . Orgel, J . C h e m . Soc., 3740 (1953). (18) M. Siiahst, A c t t i . Crysfollogr., 6, 783 (1952). (19) S. F. Darlow and W. Cochran. ibid., 14, 1250 ( l Y 6 l ) . ( 2 0 ) R . D . Ellison and H. .\. Levy, ibid., 19, 260 (1969). (21) A . S.N . Murthy, S. S . Bhat. and C . N. R . Rao. J . Chew&.S o c . d , 1251 (1970). (22) D . W J. Cruickshank and .I, P. Itol,ertuon, .1cf,L Cru,dnllogr., 6 , 698 (1953).
(23) J. D . Dunitl; and P. Strickler, in "Structural Clieniistry and Rlolecular Biology," A . Rich and N. Daridson, Ed., S . €1. Fieeman, San Francisco, Calif., 1968.
Journal of Medicinal Chemistry, 1971, Vol. 14, N o . 8 675
AKDROGKN BIOSYNTHESIS INHIljITORS between O(2) and H(1) and a H bond type linkage (albeit a strong one) between O(3) and H(1). The very strong interactions of this arrangement are partially relieved in 2 ways. As in the K H l I a l , KHClMal, and maleic acid structures the internal angles of the ring system are strained considerably. The two angles 0(2)-C(l)-C(2) and 0(3)-C(4)C(3) are not significantly different from each other and average 119O 36' =k 42'. Similarly the angles C(l)-C(2)-C(3) and C(2)C(3)-C(4) are in4gnifirantly different and average 130" 24' f 24'. These angles are however significantly different from their unst rained counterparts of 121' 18' and 121" 30', respectively.24 A situation closely paralleling this has been found in the 3 structures mentioned above. The second manner in which the strain it: relieved is by rotation of the C0.H groLips around their $-C bonds. The atoms of the C spine here are all within 0.007 : I of the plane with equa0 . 4 9 4 0 ~- 0.30272 - 6.0502 = 0. (x* = 3.6). tion - 0 . 8 1 . i ~ The O ( l ) , 0 ( 2 ) , 0 ( 3 ) , and O(4) atoms on tke other hand are 0.163(,5), -0.1.56(4), -0.133(4), aitd 0.126(4) from this plane. These figures imply that the torsion angle about C(l)-C(2) for COyH 1 is 8" 23' and that about C(3)-C(4) for COZH 2 is 6' 46' the directions of twist being such as to put O(2) and O ( 3 )
+
(24) S. F . Darlow, Acta Crystallogr., 14, 1257 (1961).
on the same side of the plane of t,he carbons. A view of the ion showing this conformation is included in Figure 5. A similar situation was found in KHClMal but not in KHMal or maleic acid. At present there seems little reason for O ( 2 ) and O(3) being on the same side of the C spine but is is intended to investigate the structures of disodium maleate and maleic acid in the hope of shedding some light on this question, or a t least partially delineate its occurrence.
Acknowledgments.-We thank the Schering Corporation for the sample of dl-brompheniramine maleate used in this analysis. Doctors A. F. Casy and R. R. Isoii of the Department of Pharmacy of t'his University originally suggested this project to us and have continued t o be a source of information regarding it. One of us (G. W.) would like to thank Dr. Ison for a copy of his Doctoral Dissertation. illessrs. L. P. Simonsen and R. J. Ulrich worked on this project as senior undergraduates and we thank t'hem for their help. Financial support from the Medical Research Council of Canada is gratefully acknowledged. The crystallographic computer programs of Dr. F. R. Ahmed, Sational Research Council of Canada have been invaluable in this work.
Steroidal Androgen Biosynthesis Inhibitors G. E. ARTH,*A. A. PATCHETT, T. JEFOPOULUS, R. L. BUGIANESI, L. H. PETERSON, Synthetic Chemical Department, Merck Sharp & Dohme Research Laboratories, Rahway, Xew Jersey
07065
E. A. HAM,F. A. KUEHL,JR.,A N D K. G. BRINK Merck Institute for Therapeutic Research, hferck Sharp & Dohme Research Laboratories, Rahway, A'ew Jersey
07066
Received September g6, 1970 A screening procedure using a rat testicular microsomal preparation with [21-14C]17a-hydroxyprogesterone as substrate was used to search for inhibitors of 17,20-lyase. A series of 17p-acylaminoandrost-4-en-3-ones and derivatives has been prepared and their syntheses have been described; they are shown to be androgen synthesis inhibitors in vitro and in vivo. These steroidal androgen synthesis inhibitors are demonstrated to be more specific in their action than the nonsteroidal inhibitors previously known. A mechanism for the action of these compounds is postulated.
Selective control of androgen biosynthesis is of potential interest in the treatment of benign prostatic hypertrophy, hirsutism, acne, arid androgen-dependent tumors. Konsteroidal synthesis inhibitors are known* which display varying degrees of selectivity in respect to enzymes involved in the adrerial and testicular synthesis of steroids including androgens.* The major pat h1va3.3~8~ which have been established for testicular androgen biosynthesis involve hydroxylation of progesterone and pregnenolone to the 17ahydroxyl derivatives and cleavage by 17,20-1yase(s) to yield androst -4-ene-3,17-dione and 30-hydroxyandrost5-en-l7--one, respectively. Testosterone arises by reduction of the former a t C-17 and in the latter by the combined action of 3(or 17)P-hydroxy steroid: S A D (1') oxidoreductase, 1.1.1.51, and 3-keto steroid A5,A4isomerase, 5.3.3.1. The possibility of direct formation of testosterone from progesterone has also been sug(1) R. Keher and F .
\V. Kahnt. E'zperientia, 21, 310 (1965).
(2) For an excellent review of this general subject see R . Gaunt, B . G . Steinet,, and J . J. Chart, Clin. Pharmacol. Ther., 9, 657 (1968). (3) J. H . Richards and J. B. Hendrickson, "The Biosynthesis of Steroids, Terpenes and Acetogenins," \V. A . Benjamin, Inc., New York, N. Y.. 1964, pp 351-357.
gested but riot conclusively e ~ t a b l i s h e d . ~Of several possibilities we chose to search for inhibitors of the 17,20-1yase step in androgen synthesis because of its key role in the conversion of C-21 to C-17 steroids atid in the hope that the enzyme might show considerable structural specificity with respect to inhibitors. Konsteroidal inhibitors were not excluded from consideration but steroidal inhibitors were judged to have the best, chance to show a selective action. Assay Method.-An in vitro screening procedure \vas used which involved measurement of [ 14C]acetate formed in the side-chain cleavage of [21-14C]17a-hydroxypr~gesterone~ by a rat testicular microsomal preparation. (See footnote a, Table I for the protocol used.) Chemisttry.-The first significant observation \vas that testosterone acetate but not testosterone was a potent inhibitor of the 17,20-lyase, and prompted a (4) (a) R . I . Dorfmsn, E. Forchielli, and M. G u t , Recent Progr. Horm. Res., 19, 14 (1963); (b) R . I . Dorfman and F . Ungar, "Metabolism of Steroid Hormones," Academic Press, S e w York, N. Y., 1965, p 1127; (c) M . A . Drosdowky, E. Forcliielli, and R. I . Dorfman, J . Eur. Steroides, I,515 (1967). (5) Kindly supplied t o us by Dr. Robert E. Erickson, formerly of these laboratories.
