J . Med. Chem. 1992,35, 4221-4229
4221
Isobenzofurans as Conformationally Constrained Miconazole Analogues with Improved Antifungal Potency' Raymond G. Lovey,'lt Arthur J. Elliott,' James J. Kaminski,'p+ David Loebenberg,*J Raulo M. Parmegiani,t D. F. Rane,t Viyyoor M. Girijavallabhan,t Russel E. Pike,? Henry Guzik,t Barry Antonacci,t and Taisa Y. Tomainet Schering-Plough Research Institute, 60 Orange Street, Bloomfield, New Jersey 07003 Received June 10, 1992
A series of halogen-substituted isobenzofuran analogues was synthesized, which represented conformationally constrained analogues of miconazole (I). In vitro and in vivo topical antifungal activity against both dermatophytes and Candida species varied widely, but 13c proved to be significantly superior to both 1 and clotrimazole against a vaginal Candida infection in hamsters, while 13b was significantly more active than 1 against a a topical Trichophyton infection in guinea pigs. None of the compounds were orally active. When the most direct analogue of 1 proved to be among the least active, a molecular modeling study was done using 1, the two active analogues 13b and 13c, and the inactive analogue 13a. All four compounds possessed skeletally similar conformations either at or energetically readily accessible from the global minimum energy conformations. This common conformation of the inactive analogue 13a,however, occupies unique molecular volume space associated with two chlorine atoms, which must also present unique electrostatic properties at the receptor. The conformation-activity relationships discussed may contribute toward deduction of additional structural requirements for pharmacophore optimization and more efficacious antifungal drugs. antifungals still remain a viable lead structure in pursuit Miconazole (1) has become a well-established drug for the treatment of many mycotic infections since it was first of a more efficacious orally active, broad spectrum, described.2 It acta by competitive inhibition3t4through systemic fungicidal drug. Moreover, it is one of the few direct interaction" of the cytochromeP-450 enzyme which classes of compounds offering a clear identity of the target catalyzes the 14-a-demethylationof 24-methylene-24,25enzyme and adequate specificity for fungal organisms. dihydrolanosterol (P-45014aDM). This inhibition of 14-aMiconazoleis a flexible molecule containingsix rotatable demethylation of 24-methylene-24,25-dihydrolanosterol bonds (Figure 1). Examination of the gas-phase conforresults in a lethal disruption in the normal sterol biosynmational hyperspace available to 1 starting from, and thesis chain in fungi, but is of minimal consequence to including, ita initial conformation,and defined about the mammals. Miconazole was the first commercially signifrotatable bonds described in Figure 1, suggests that 1can icant example of what has become known as a broad class adopt a great number of energetically accessible conforof a-arylazolylethanol derivatives, but ita use has been mations. The total number of valid conformations availlimited by a lack of oral absorption, limited spectrum of able to 1, C = 827 valid conformations, also includes ita activity, and occasional undesirable side effects observed bioactive conformation,Le., that conformation of 1 which when administered at therapeutic doses intraven~usly.~~~is responsible for expression of ita biological activity at Despite intensive research efforts over the years, azole the P'4501kDM binding site. It is conceivable that a conformationally constrained t Chemical Research Department. analogue that mimics the bioactive conformation might BiologicalResearch Department. (1)Presented in part at the 29th Interscience Conference on Antiexhibit a higher level of intrinsic antifungal potency such microbial Agents and Chemotherapy, Houston, TX, September 1989, that the analogue, or further structural modification of Abstract 729. the analogue, could produce a candidate from this series (2) Godefroi, E. F.; Heeres, J.; van Cutsem, J.; Janssen, P. A. The Preparation and Antimycotic Properties of Derivatives of 1-Phenethfor preclinicalprogression. Furthermore, it is also possible yliiidazoles. J. Med. Chem. 1969, 12, 784-791. that a conformationallyconstrained analogue of 1 might (3) Vanden-Bmche, H.; Lauwers, W.; Willemsens, G.; Marichal, P.; not be as suitable a substrate for mammalian aromatase Cornellisen, F.; Cools, W. Molecular Basis for the Antimycotic and Antibacterial Activity of N-Substituted Imidazoles and Triazoles: the enzymes. Thus, by virtue of introducing this conformaInhibition of Isoprenoid Synthesis. Pestic. Sci. 1984, 15, 188-198. tional constraint, a potential liability of this series might (4) Henry, M. J.; Sisler, H. D. Effects of Sterol Biosynthesis Inhibiting FungicidesonCytochromeP-450Oxygenationsin Fungi. Pestic. Biochem. be eliminated. Physiol. 1984,22, 262-275. This report describes a series of azolylisobenzofurans (5) Yoehida, Y.; Aoyama, Y. Interaction of Azole Antifungal Agents that are skeletalanaloguesof 1,but whose conformationally with Cytochrome P-45016DM Purified from S. cereuisiae Microsomes. Biochem. Pharmacol. 1987,36, 22!+235. constrained structure allows them to adopt only a limited (6)Rodrigues, A. D.; Gibson, G. G.; Ioannides, C.; Parke, D. V. subset of conformations relative to 1, possibly including Interactions of Imidazole Antifungal Agents with Purified Cytochrome P-450 Proteins. Biochem. Pharmacol. 1987,36, 4277-4281. the bioactive conformation. f
(7) Hitchcock, C. A.; Dickinson, K.;Brown, S.B.; Evans, E. G. V.; Adame,D.J. Interaction of AzoleAntifungal Antibiotics with Cytochrome P-4Wdependant l4u-sterolDemethylasePurified from Candida albicans. Biochem. J. 1990,266,475480. (8)Kan,P. B.; Hint, M. A.; Feldman, D. J. Inhibition of Steroidogenic Cytochrome P-450 Enzymes in Rat Testes by Ketoconazole and Related Imidazole Anti-Fungal Drugs. Steroid Biochem. 1985,23, 1023. (9) Mason, J. I.; Murray, B. A.; Olcott, M.; Shets, J. J. Imidazole Antimycotice: Inhibitors of Steroid Aromatase. Biochem. Pharmacol. 1986,34, 1087-1092.
Chemistry Substituted 2-(azolylmethyl)isobenzofurans 13 were prepared by one of two methods shown in Schemes I and II.l0 Method A was based upon acid-catalyzeddehydrative (10) Lovey, R. G.; Elliott, A. J. US.Patent 4,737,508, 1988.
0022-262319211835-4221$Q3.QQ/Q 0 1992 American Chemical
Society
Louey et al.
4222 Journal of Medicinal Chemistry, 1992, Vol. 35, No. 22
Scheme I11 a
Scheme I a Method A G-H
Y
2: G = O ; n - 1 : Y - H : 3: G - O : n = l ; Y = H ; 4: G = O ; n - Z Y = H : 5: G = S ; n = l ; Y = H ; 6: G.0: n = 1: Y =CI:
G-THP
Y
Z=H Z-CI Z=H Z=H
C
7: G - O ; n = l ; Y = H : Z = H B:G=O;n.l;Y-H;Z.CI Q:G-On=2;Y=H;Z.H lO:G=S;n=l;Y=H:Y=H
I
W
19
CI
2-CI
9
CI &J
Y C'
20
X 118: R = H l l b - h : R-THP
12.: R - H 12b.h: R-THP
131-h
a (a) Dihydropyran, TsOH, CHzClz (2-5); (b) n-BuLi, THF, -70 OC (6); (c) Mg, THF, 50 OC; (d) 1-sodium l,2,4-triazole or 1-sodium imidazole, DMF, 80 OC; (e) 6 N HC1, reflux.
Scheme I1 a Method B
14
15 1 6 I'
Q-- CI
d
Q-CI
17
e, f
-t
Q CI
18
131
(a) Ethylene glycol, TsOH, CHzC12; (b) Mg, THF, 50 "C; (c) 1-sodium1,2,44riazole, DMF, 80 "C; (d)oxalic acid, aqueous dioxane, reflux; (e) NaEiHh, aqueous EtOH (06 N HCl, reflux. a
cyclization of o-bis(hydroxymethy1)benzenes as adapted from Martin." Substituted o-bromobenzylalcohols 2 and 3 were protected as THP ethers 7 and 8 and treated with magnesium in THF to form a Grignard reagent, which required heatingat near reflux temperature to both initiate and maintain the reaction. The Grignard reagents were reacted with a substituted phenacyl chloride to form chlorohydrins, which cyclized in situ to epoxides 11 under the reaction conditions used.12 The epoxides were then treated with the freshly prepared sodium derivative of an azoleto afford the azolyl ethanols 12. Heating 12at reflux in aqueous HC1removed the THP protecting group when present and affected cyclization of the intermediate diols to the desired isobenzofurans 13. The intermediate diols could be obtained by conducting the hydrolysis in an aqueous oxalic acid-dioxane mixture. (11)Bauer, V. J.; Duffy, B. J.; Hoffman, D.; Klioze, S. S.; Kosley, R. W., Jr.;McFadden,A.R.;Martin,L.L.;Ong, H.H.;Geyer, H. M. Synthesis of SpUo[ieobenzofuran-l(3H),4'-piperidines]aa Potential CentralNervous System Agenta. J. Med. Chem. 1976, 19, 1315-1324. (12) Worthington, P. A. Recent Developmenta in the Chemistry of Azole Fungicides. 1984Br. Crop h o t . Conf.-PestsDis.1984,9B-4,955962.
21
(a) Mg, THF, 50 OC; (b) 1-sodium imidazole, DMF, 80 OC; (c) 6 N HC1, reflux.
An exception to the general procedure of method A was required when the Grignard reagent of the THP ether of 6 failed to form under all forcing conditions tried. However, by treating 6 with 2 equiv of n-butyllithium at below -65 "C, a marginally stable o-lithioarylintermediate was formed. When alkylated immediately with 2,4dichlorophenacylchloride,1 la could be obtained in modest yield and subsequently reacted as for its THP etherprotected analogues. MethodB (Scheme11)entailed much the same chemistry except that the starting material was a benzaldehyde rather than benzylic alcohol and was protected as a dioxolane. Followingmetallation,alkylation,and azole incorporation, the product of acid-catalyzed deprotection/cyclizationof, e.g., 17 was the lactol 18. The crude product of the reduction of 18 by NaBH4, predominantly the diol analagous to 12a,was directly cyclized in aqueous HCl at reflux to the isobenzofuran 13f. Unless the lactol was desired, reduction of benzaldehydes to benzyl alcohols for use via method A proved experimentallymore convenient. Compounds 13b and 13f,and isobenzofurans in general, have also been prepared by other methods.13 Method A was used to prepare the structural variants 19-2 1 (Scheme 111). When 3-chloro-1-(4-chloropheny1)propanone14 was reacted with the Grignard reagent of 7, the chlorobenzyl analogue 19 was obtained. When 2-(2bromopheny1)ethanoll6(4) was used to prepare the Grignard reagent of 9, the benzopyran 20 was obtained. Similarly, the Grignard reagent of 10 provided the isobenzothiophene analogue 21. Most of the alcohols used as starting materials for 2-5 were commercially available. Alcohol 6, not previously known, was prepared by electrophilicbromination of 2,4dichlorotoluene,followed by peroxide-catalyzed benzylic (13) Clough,J. M.; Beautement, K. Brit. UK Pat. Appl. GB 2,143,523, 1985. (14)Yoshida, N.; Kuniyuki, T.; Kazuyuki, W. Synthesis of a-Haloa'-hydroxyimino Ketones. Sonkyo Kenkyuaho Nempo 1970,22,W89; Chem. Abstr. 1971, 75, 63325d. (15)Yale, H. L.; Petigara, R. B. Novel Heterocycles. XI. Synthesis of 11,12-Dihydropyrido[2,1-b][1,3]benzodiazepinesand GH-Pyrido[l,Sc1[1,3,51benzoxadiazepines. J.Heterocycl.Chem. 1974,11,331-337: bp 130-132 O C (8 torr).
Journal of Medicinal Chemistry, 1992, Vol. 35, No. 22 4223
Conformationally Constrained Miconazole Analogues
Table I. Physical Data for Substituted azolylisobenzofurans and analogues Y
x 1-h
A -
W
X
Y
2
mD. _ .OC
c1 H c1 c1 F H H H
c1 c1
c1 H H H H H H H
c1
200-203 192-193 220-222 195-198 143-146 188-196 221-224 209-212 215-2 17 118-124 dec 154-158 219-222
formula anal. CleH12CLiNzO.HC1.2H20 H ClsH1&lN20.HCl H c1 Ci&I1&12N20-HCl c1 c1 CleH13C13N20.HCl F H C1eH1~F2N20*HClJ/2CH3CNb c1 H CI~H~&IN~O*HCI Ph H C24H2&420*HCl H H C18Hl&O*HCl Ci7Hi4ClN302 ClsH17ClN20.HCl C~~H1~ClN20*HCl*'/2H20 CisHisN&HCl .. .- a C: calcd, 44.89; found, 44.46. * Recrystallization solvent and observed in NMR spectrum. N: calcd, 61.98; found, 61.55. C: calcd, 65.74; found, 66.23. no.
13a 13b 13c 13d 1% 13f 13g 13h 18 19 20 21
CH CH CH CH CH N CH CH
Table 11. Antifungal Minimum Inhibitory Concentration Ranges (pg/mL)
SDB medium, pH 5.7 organismsa T.m. T.r. Ma. M.c.
no. C.a. C.t. C.S. C.P. 1 2-8 4 8
