Synthesis of novel tetrahydroisoquinoline bronchodilators

Article abstract of DOI:10.1016/j.bmcl.2010.07.057

The synthesis and bronchorelaxing effects of a series of novel tetrahydroisoquinoline amides are described. The compounds were evaluated for their ability to relax LTD4 contracted isolated human small airways ex-vivo. Several compounds demonstrated highly

Full text of DOI:10.1016/j.bmcl.2010.07.057

Bioorganic & Medicinal Chemistry Letters 20 (2010) 4999–5003
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis of novel tetrahydroisoquinoline bronchodilators
*
Maria F. Dalence-Guzmán, Jörgen Toftered, Viveca Thornqvist Oltner, David Wensbo, Martin H. Johansson
Respiratorius AB, Magistratsvägen 10, SE 226 43 Lund, Sweden
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis and bronchorelaxing effects of a series of novel tetrahydroisoquinoline amides are
described. The compounds were evaluated for their ability to relax LTD4 contracted isolated human small
airways ex-vivo. Several compounds demonstrated highly efficacious bronchorelaxing properties. Cinna-
mide 71 was selected for further studies and constitutes a promising candidate as a novel bronchorelax-
ing agent for the treatment of pulmonary disorders.
Received 8 June 2010
Revised 13 July 2010
Accepted 14 July 2010
Available online 19 July 2010
Ó 2010 Elsevier Ltd. All rights reserved.
Dedicated to the memory of Salo Gronowitz
Keywords:
Asthma
COPD
Bronchodilator
Tetrahydroisoquinoline
Palladium catalyzed cross-coupling
Bronchodilators, alone or in combination with anti-inflamma-
tory agents, are the mainstay of asthma and COPD therapies. Cur-
rently used bronchodilators, b2-agonists and anti-cholinergics, rely
on two pharmacological principles; stimulation of adrenergic
receptors and blockade of muscarinic receptors to acetylcholine
activation, respectively. In the treatment of severe (refractory)
asthma and COPD there is an increased awareness of the role that
the small (peripheral or distal) airways play in these diseases.1
Improvements in pulmonary function and health status have been
closely linked to the relaxation of the small airways.2 However,
current treatments have not been optimized to target the small
airways.3 Improving the bronchodilatory response in the small,
peripheral airways can be achieved through optimizing delivery
or addressing new targets/pathways. The use of ultrafine formula-
tions of b2-agonist/steroid treatments in limited trials suggest that
this might lead to improved outcomes.4 Conversely, we5 and oth-
ers6 have demonstrated that b2-agonists have a reduced efficacy
in relaxing contracted small airways compared to larger airways
suggesting the need of finding novel mechanisms and optimizing
compounds that can lead to the efficacious relaxation of the small
airways. New principles of smooth muscle relaxation should there-
fore be viewed as a possible strategy for finding improved asthma
and COPD therapies.7 In this context it is important to realize that
there are differences between large and small airways just as there
are differences in pulmonary physiology and pharmacology be-
tween species. Finding novel compounds that can relax human
small airways should thus focus on studying human small airways
to the largest extent.
We recently described capsazepine (1) and related capsazepi-
noid compounds (e.g., 2) as constituting a novel class of bronchod-
ilators (Fig. 1).5,8 We now wish to describe the further development
of this class of compounds and the improvement of their drug-like
properties.
Wanting to avoid the thiourea moiety present in most of the pre-
vious compounds,8 we followed up on the fact that the previously
described amide 3 was roughly equipotent to thiourea 2.8d We also
focused on the improvement of physical–chemical properties to
allow a lung selective action following inhaled administration.
A series of (hetero)aromatic amide derivatives were therefore
prepared to evaluate for their bronchorelaxing properties ex-vivo
using isolated human small airways.
Previous work had established the crucial role of the 4,7-di-
chloro-5,6-dihydroxy tetrahydroisoquinoline core structure for
obtaining good bronchorelaxing properties so this was retained
throughout this study.8c The desired butanoyl amides were pre-
pared by coupling the tetrahydroisoquinoline scaffold with the
corresponding acids.
The necessary carboxylic acids, depicted in Scheme 1, were syn-
thesized via Negishi couplings between the corresponding aryl ha-
lides 4–11 and 4-ethoxy-4-oxobutylzinc bromide using PEPPSI-IPr
as catalyst.9 Attempts using Pd(PPh3)4 gave lower yields.10 Hydro-
lysis of the resulting esters 12–19 gave the desired acids 20–27.
3,5-Disubstituted 2-pyridyl butanoic acids, 33–36, shown in
Scheme 2 were synthesized from 2,3-dichloro-5-(trifluoromethyl)-
pyridine. A regioselective Negishi coupling yielded the desired
isomer (29) as the major product. Suzuki couplings of 29 with
* Corresponding author. Tel.: +46 46162060; fax: +46 46162069.
E-mail address: martin.johansson@respiratorius.com (M.H. Johansson).
0960-894X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2010.07.057

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M. F. Dalence-Guzmán et al. / Bioorg. Med. Chem. Lett. 20 (2010) 4999–5003
Figure 1.
Scheme 1. Reagents and conditions: (a) For 4–9 and 11; 4-ethoxy-4-oxobutylzinc bromide, PEPPSI-Ipr, THF, rt, 48 h, yields >80%. For 10; 4-ethoxy-4-oxobutylzinc bromide,
Pd(Ph3P)4, THF, rt, 48 h; (b) NaOH (1 N aq), EtOH/THF (1:1).
Scheme 2. Reagents and conditions: (a) 4-ethoxy-4-oxobutylzinc bromide, PEPPSI-Ipr, THF, rt, 56%; (b) trimethyl boroxine, 1,3-bis(2,6-diisopropylphenyl)imidazol-2-
ylidene(1,4-naphthoquinone)palladium(0) dimer, CsF, 1,2-dimethoxyethane, microwave, 100 °C, 45 min, 64%; (c) cyclohexylzinc bromide, PEPPSI-Ipr, THF, rt, 40 h, 27%;
(d) phenyl boronic acid, 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene(1,4-naphthoquinone)palladium(0) dimer, CsF, 1,2-dimethoxyethane, microwave, 100 °C, 45 min,
80%; (e) NaOH (1 N aq), EtOH/THF (1:1).
trimethylboroxine11 and phenylboronic acid yielded esters 30 and
32 respectively, while a Negishi coupling with cyclohexylzinc bro-
mide yielded 31. Finally, the esters were hydrolyzed to the corre-
sponding carboxylic acids.
In attempt to vary the length and flexibility of the linker, cinna-
mide 39 was prepared by coupling of 378c and cinnamoyl chloride
(Scheme 3). The cinnamide 39 displayed bronchorelaxing proper-
ties similar to butanamide 3 (vide infra) so a series of cinnamides
were also prepared.
The synthesis of cinnamic acid derivatives is outlined in Scheme
4. Knoevenagel condensation using aldehyde 40 and malonic acid
yielded acid 41.12 A halogen lithium exchange of compound 42
followed by acylation using N,N-dimethylacetamide gave acetylpyr-
idine 43. Subsequent Horner–Wadsworth–Emmons reaction be-
tween 43 and triethylphosphonoacetate13 yielded compound 44
which was hydrolyzed to acid 46. Carboxylic acids 47 and 50 were
synthesized from 5-bromo-2-(trifluoromethyl)pyridine (42) and
5-bromo-4-methyl-2-(trifluoromethyl)pyrimidine (48) via Heck
reactions11,14 followed by hydrolysis. Finally, trisubstituted pyridine
carboxylic acid 54 was synthesized from 2-chloro-3-iodo-6-(trifluo-
romethyl)pyridine (51) by a Heck reaction to introduce the acryl
moiety followed by a Suzuki coupling with trimethylboroxine to
introduce the methyl group in the 2-position.15
The target amides were prepared using one of the procedures
shown in Scheme 5. Compounds 68 and 69 were prepared from
commercially available (E)-3-(pyridin-3-yl)acrylic acid and 4-
methoxycinnamic acid, respectively.
It was previously established that dichlorination of the dihy-
droxy tetrahydroisoquinoline moiety greatly increased the bron-
chorelaxing potency within the capsazepinoid series.8c To further
Scheme 3. Reagents and conditions: (a) Et3N, DMF, rt, 16 h, 40%.

M. F. Dalence-Guzmán et al. / Bioorg. Med. Chem. Lett. 20 (2010) 4999–5003
5001
Scheme 4. Reagents and conditions: (a) Malonic acid, pyridine, piperidine, 115 °C, 2 h, 45%; (b) sec-BuLi, N,N-dimethylaminoacetamide, Et2O, À78 °C, 1 h, then rt 16 h, 54%;
(c) Triethyl phosphonoacetate, NaH, THF, 0 °C, 30 min, reflux, 125 °C, 6 h, 100%; (d) NaOH (1 N aq), EtOH–THF (1:1), 75%; (e) ethyl acrylate, Pd(OAc)2, DABCO, K2CO3, 125 °C,
12 h, 97%; (f) methyl acrylate, P(OCH3)3, Pd(OAc)2, Et3N, DMF, 110 °C, 1.5 h, 72%. (g) NaOH (1 N aq), MeOH, 65%; (h) methyl acrylate, Pd(OAc)2, DABCO, K2CO3, DMF, 120 °C,
4 h, 67%; (i) trimethyl boroxine, Pd(PPh3)4, K2CO3, 1,4-dioxane, 110 °C, 24 h, 82%; (j) NaOH (1 N aq), MeOH, 40 °C, 2 h, 100%.
This amine was then coupled with 47 to obtain the dimethylat-
ed analogue 78.
Difluorinated catechols are relatively scarce and derivative 84
proved to be a more challenging target (Scheme 7). Difluorodi-
methoxybenzene 80 was obtained from tetrafluorobenzene 79.17
Formylation was then performed with dichloromethyl methyl
ether.18 Reductive amination of 81 gave 82. This amine was cou-
pled with acid 47 and then cyclized under acidic conditions to give
Scheme 5. Reagents and conditions: Procedure A: (i) 55, EDCÁHCl, HOBt, DMAP,
dihydroisoquinoline 83.19 Palladium-catalyzed transfer-hydroge-
Cs2CO3, DMF, rt, 48 h; (ii) BBr3, CH2Cl2, 0 °C, 1 h, rt, 18 h; (iii) MeOH, NaHCO3, rt,
30 min. Procedure B: 37, EDCÁHCl, HOBt, DMAP, Cs2CO3, DMF, rt, 48 h. Procedure C:
nation, unfortunately which also led to reduction of the cinnamide
moiety, followed by demethylation afforded compound 84.
The bis-fused dihydrofuran analogue 89 was prepared using a
bis-lithiation/Parham cyclization strategy (Scheme 8).20 6,7-Dihy-
droxy-tetrahydroisoquinoline 85 was brominated and protected
using Boc-anhydride. Di-alkylation and chlorination yielded cycli-
zation precursor 87. Rapid addition of n-BuLi at 0 °C gave the dou-
bly fused tetrahydrobenzodifuran 88. Deprotection and coupling
afforded the desired compound 89.
All compounds were tested for their bronchorelaxing properties
on isolated human small airways (inner diameter <2.0 mm) using a
procedure and apparatus previously described.5,8 The measure of
bronchorelaxing efficacy is given as percentage remaining contrac-
tion (%RC) which is defined as the quote of the remaining contrac-
(i) CDI, EtOAC, reflux, 1 h. (ii) 37, HOBt, reflux, 3 h.
investigate this phenomenon the dimethyl-, difluoro- and bis-
fused benzotetrahydrofuran analogues were prepared to see if
lipophilic, electronic or other factors were responsible for the in-
crease in potency.
The dimethylated tetrahydroisoquinoline analogue 78 was
prepared by a halomethylation procedure (Scheme 6). Thus, com-
mercially available 75 was acetylated and treated with 2-methoxy-
acetylchloride to obtain bis-benzyl chloride 76.16 Reductive
substitution with sodium cyanoborohydride followed by alkaline
hydrolysis afforded the desired amine 77.
Scheme 6. Reagents and conditions: (a) AcCl, Et3N, CH2Cl2, rt, 0.5 h; (b) 2-methoxyacetylchloride, SnCl4, CH3NO2, rt, 24 h, 14% (over 2 steps); (c) NaCNBH3, DMF, 100 °C, 16 h;
(d) NaOH, H2O, dioxane, reflux, 21 h, 42% (over 2 steps); (e) 47, PyBrOP, DMAP, THF, rt, 2.5 h, 87%; (f) BBr3, CH2Cl2, 0 °C then rt, 3.5 h, reflux 1.5 h, 93%.

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M. F. Dalence-Guzmán et al. / Bioorg. Med. Chem. Lett. 20 (2010) 4999–5003
Scheme 7. Reagents and conditions: (a) NaOH, ethyleneglycol, 180 °C, 24 h, 58%; (b) Cs2CO3, DMF, 160 °C, 17 h, 45%; (c) AlCl3, toluene, 110 °C, 4 h, quant; (d) Me2SO4, K2CO3,
acetone, reflux, 3 h, 47%; (e) MeOCHCl2, TiCl4, CH2Cl2, 0 °C, 30 min, rt, 2 h; (f) 2,2-dimethoxyethanamine, benzene, reflux, 16 h, 72% (over 2 steps); (g) NaBH4, MeOH, 0 °C,
0.5 h, 81%; (h) 47, EDCÁHCl, HOBt, DMF, rt, 2 h, 73%; (i) AlCl3, 1,2-dichloroethane, rt, 10 min, 33%; (j) Pd/C, HCO2NH4, MeOH, rt, 3 h, 17%; (k) BBr3, CH2Cl2, 0 °C, 1 h, 49%.
Scheme 8. Reagents conditions: (a) Br2, AcOH, rt, 16 h, 80%; (b) (Boc)2O, Et3N THF/H2O (6:1), rt, 2 h, 92%; (c) 2-chloroethanol, NaOH, EtOH/H2O, reflux, 4 h, 6%; (d) PPh3, CCl4,
reflux, 3 h, 41%; (e) n-BuLi, THF, 0 °C, 15 min, 47%; (f) TFA, CHCl3, rt, 1 h, 77%; (g) 47, EDCÁHCl, HOBt, DMF, rt, 16 h, 32%.
tion in the presence of the test item at a given concentration (usu-
ally 10 M) and the maximum contraction evoked by the contrac-
tile agent (LTD4) in the absence of test item.
a single major metabolite (99%) compared to 3 which gave rise
to multiple metabolites. This major metabolite was identified as
a glucuronide.
l
In the butanoyl amide series changing a phenyl for a pyridyl,
preferably a 2-pyridyl, did not affect the potency (cf. 3 and 59,
Table 1). However, changing the phenyl for a heteroaromatic ring
had a pronounced effect on the in vitro metabolism. The in vitro
disappearances and metabolic profiles of 3 and 56 were deter-
mined using human liver homogenate incubations. Compound 56
showed a rapid disappearance as determined by LC/UV and gave
Small lipophilic ortho substituent combined with a trifluoro-
methyl group in the para position improved the potency as wit-
nessed by compounds 64 and 65 (–Cl and Me, respectively).
Larger ortho substituents (e.g., 66 and 67) decreased or did not
improve potency. Larger, polar groups in the para position were
not tolerated as witnessed by the loss of potency of the sulfone
analogue 62.
The SAR of the cinnamides followed the same trend with a para
trifluoromethyl group improving potency (cf. 68 and 72, Table 2).
3-Pyridyls were the preferred heteroaromatics, being slightly more
potent than the corresponding pyrimidine (cf. 73 and 74). ortho
Substitution with a small lipophilic group (74) did not significantly
Table 1
Butanoyl amides
Table 2
Cinnamides
Compound
R1
R2
X
Y
Coupling
% RCa
% RCa
procedure
10
lM
1 lM
3
56
57
58
59
60
61
62
63
64
65
66
67
Cl
F
NO2
CF3
Cl
H
H
H
H
H
H
H
H
CH
N
N
N
N
N
N
N
CH
N
CH
CH
CH
CH
CH
CH
CH
CH
N
CH
CH
CH
CH
Ref8d
A
A
A
A
A
A
A
B
A
B
B
B
16
25
33
19
15
34
31
72
26
5
80
89
74
72
85
86
96
99
93
61
67
ndb
90
a
a
Compound R1
R2
R3
X
Y
Z
Coupling
procedure (10
% RC
% RC
l
l
M) (1
M)
CN
39
68
69
70
71
72
73
74
H
H
H
H
H
H
OH
F
H
H
H
H
H
H
CH CH CH Scheme 3
CH
CH CH CH
N
CH
CH
41
44
32
24
7
6
18
9
83
100
ndb
ndb
74
87
88
71
OMe
SO2Me
CF3
CF3
CF3
CF3
CF3
N
CH
A
A
A
A
C
C
B
H
CH CH
Cl
Me
cHex
Ph
Me CF3
N
N
N
CH
CH
N
N
N
N
7
77
38
H
H
H
CF3
CF3 Me CH
CF3 Me CH CH
N
a
a
Percentage remaining contraction at the indicated concentration in the pres-
Percentage remaining contraction at the indicated concentration in the pres-
ence of test compound and LTD4 compared to the maximum contraction caused by
LTD4.
ence of test compound and LTD4 compared to the maximum contraction caused by
LTD4 alone.
b
b
Not determined.
Not determined.

M. F. Dalence-Guzmán et al. / Bioorg. Med. Chem. Lett. 20 (2010) 4999–5003
5003
Table 3
suggesting that 71 has a suitable profile for selective pulmonary
delivery with low systemic exposure.
Interestingly, 71 also displayed relevant anti-inflammatory
properties. LTB4 and MCP-1 production in LPS stimulated human
peripheral mononuclear blood cells was significantly inhibited by
71 at 10 lM.
The combination of the demonstrated relaxing effects on con-
tracted human small airways (ex-vivo), anti-inflammatory proper-
ties and lung selective pharmacokinetics makes 71 a very suitable
candidate for further development towards the treatment of pul-
monary diseases such as COPD and asthma.
Compound
% RCa 10
lM
90b
84
78
89
29
85
75
91
a
References and notes
Percentage remaining contraction at the indicated
concentration in the presence of test compound and
LTD4 compared to the maximum contraction caused by
LTD4.
1. (a) Contoli, M.; Bousquet, J.; Fabbri, L. M.; Magnussen, H.; Rabe, K. F.; Siafakas,
N. M.; Hamid, Q.; Kraft, M. Allergy 2010, 65, 141; (b) Sturton, G.; Persson, C.;
Barnes, P. J. Trends Pharmacol. Sci. 2008, 29, 340.
b
Prepared by catalytic transfer hydrogenation of 72.
2. (a) Takeda, T.; Oga, T.; Niimi, A.; Matsumoto, H.; Ito, I.; Yamaguchi, M.;
Matsuoka, H.; Jinnai, M.; Otsuka, K.; Oguma, T.; Nakaji, H.; Chin, K.; Mishima,
M. Respiration 2009. doi:10.1159/000242113; (b) Hasegawa, M.; Makita, H.;
Nasuhara, Y.; Odajima, N.; Nagai, K.; Ito, Y.; Betsuyaku, T.; Nishimura, M. Thorax
2009, 64, 332.
3. Janssen, L. J.; Killian, K. Respir. Res. 2006, 7, 123.
4. Huchon, G.; Magnussen, H.; Chuchalin, A.; Dymek, L.; Gonod, F. B.; Bousquet, J.
Respir. Med. 2009, 103, 41.
5. Skogvall, S.; Dalence-Guzmán, M. F.; Berglund, M.; Svensson, K.; Mesic, A.;
Jönsson, P.; Persson, C. G. A.; Sterner, O. Pulm. Pharmacol. Ther. 2008, 21, 125.
6. (a) Finney, M. J.; Karlsson, J. A.; Persson, C. G. Br. J. Pharmacol. 1985, 85, 29; (b)
Wagner, E. M.; Bleecker, E. R.; Permutt, S.; Liu, M. C. Am. J. Respir. Crit. Care Med.
1998, 157, 447.
7. Baroffio, M.; Emanuele, C.; Brusasco, V. Ther. Adv. Respir. Dis. 2008, 2, 129.
8. (a) Skogvall, S.; Berglund, M.; Dalence-Guzmán, M. F.; Svensson, K.; Jönsson, P.;
Persson, C. G. A.; Sterner, O. Pulm. Pharmacol. Ther. 2007, 20, 273; (b) Dalence-
Guzmán, M. F.; Berglund, M.; Skogvall, S.; Sterner, O. Bioorg. Med. Chem. 2008,
16, 2499; (c) Berglund, M.; Dalence-Guzmán, M. F.; Skogvall, S.; Sterner, O.
Bioorg. Med. Chem. 2008, 16, 2513; (d) Berglund, M.; Dalence-Guzmán, M. F.;
Skogvall, S.; Sterner, O. Bioorg. Med. Chem. 2008, 16, 2529.
improve the potency as seen in the butanoyl amide series. How-
ever, substitution of the cinnamide moiety was allowed (71).
Finally the role of dichlorination was evaluated. As can be seen
in Table 3 only the di-chlorinated analogue 90 displayed retained
potency. Neither di-fluorination nor di-methylation provided
active compounds (84 and 78, respectively). Although chlorine
has an inductive effect, intramolecular hydrogen bonding plays a
dominant role in lowering the pKa of chlorophenols.21 We suggest
that the role of the chlorine atoms is to provide intramolecular
hydrogen bonding to the hydroxyl groups, lowering the pKa of
both hydroxyl groups and providing a partial dianion character.
This is partially verified by the difluorinated analogue as it has
been experimentally demonstrated that fluorine provides a much
smaller hydrogen bond in ortho-halogenated phenols.22 If the
hydrogen bonding only improved the bidentate binding capability
of the catechol it was believed that the bis-dihydrofuran derivative
89 would show activity, which was not the case.
9. Organ, M. G.; Avola, S.; Dubovyk, I.; Hadei, N.; Kantchev, E. A. B.; O’Brien, C. J.;
Valente, C. Chem. Eur. J. 2006, 12, 4749.
10. Blommaert, A.; Turcaud, S.; Anne, C.; Roques, B. P. Bioorg. Med. Chem. 2004, 12,
3055.
11. Kwok, T. J.; Virgilio, J. A. Org. Process. Res. Dev. 2005, 9, 694.
12. Hynd, G.; Ray, N. C.; Finch, H.; Middlemiss, D.; Cramp, M. C.; Blaney, P. M.;
Williams, K.; Griffon, Y.; Harrison, T. K.; Crackett, P. PCT Int. Appl. WO
2006136859 A2, 2006.
Compound 7123 was further evaluated and characterized as a
potential drug candidate. The EC50 was determined to 2.27 lM
and the maximum functional efficacy to 98% in the ex-vivo assay.
13. Srikrishna, A.; Satyanarayana, G.; Prasad, M. R. Synth. Commun. 2005, 35, 1687.
14. For compound 9 see Li, J.-H.; Wang, D.-P.; Xie, Y.-X. Synthesis 2005, 13, 2193.
15. Gray, M.; Andrews, I. P.; Hook, D. F.; Kitteringham, J.; Voyle, M. 2000, 41, 6237.
16. McKillop, A.; Madjdabadi, F. A.; Long, D. A. Tetrahedron Lett. 1983, 24, 1933.
17. Ladd, D. L.; Weinstock, J. J. Org. Chem 1981, 46, 203.
18. Adejare, A.; Gusovsky, F.; Padgett, W.; Creveling, C. R.; Daly, J. W.; Kirk, K. L. J.
Med. Chem. 1988, 31, 1972.
19. Perchonock, C. D.; Lantos, I.; Finkelstein, J. A.; Holden, K. G. J. Org. Chem. 1980,
45, 1950.
Further pharmacological studies using isolated human small air-
ways revealed that 10 lM 71 gave 93%, 97% and 82% relaxation
of acetylcholine, histamine and a combination, ‘‘cocktail”, of
LTD4, acetylcholine and histamine induced contractions, respec-
tively. This demonstrates that 71 act as a fully functional antago-
nist against contractile agents.
Compound 71 has moderate aqueous solubility (18 lM) with a
20. (a) Monte, A. P.; Marona-Lewicka, D.; Parker, M. A.; Wainscott, D. B.; Nelson, D.
L.; Nichols, D. E. J. Med. Chem. 1996, 39, 2953; (b) Parham, W. E.; Jones, L. D.;
Sayed, Y. A. J. Org. Chem. 1976, 41, 1184.
measured log D7.4 of 3.5. The compound is stable in plasma but
rapidly metabolized through phase II mechanisms in human hepa-
tocytes in the presence of co-factors (in vitro). Half-life in vivo was
estimated to 0.02 h. Metabolites arising from glucuronidation and
sulfatation were identified as the main metabolites and 71 showed
very similar in vitro metabolic profiles in both rat and dog.
In vivo pharmacokinetic studies in rats following intratracheal
administration showed that 71 was detectable in the lung up to
24 h post dosing but not in plasma after 2 h. At all time points
higher levels of 71 were measured in the lung compared to plasma
21. Han, J.; Deming, R. L.; Tao, F.-M. J. Phys. Chem. A 2004, 108, 7736.
22. Bourassa-Bataille, H.; Sauvageau, P.; Sandorfy, C. Can. J. Chem. 1963, 41, 2240.
23. 1H NMR (CD3OD) rotameric mixture d 8.92 (maj) (d, J = 2.0 Hz, 1H) 8.88 (min) (d,
J = 1.6 Hz, 1H) 8.21 (maj) (dd, J = 2.0, 8.4 Hz, 1H) 8.17 (min) (dd, J = 2.0, 8.4 Hz,
1H) 7.84 (d, J = 8.4 Hz, 1H) 6.72 (maj) (br s, 1H) 6.70 (min) (br s, 1H) 4.72 (maj) (s,
2H) 4.66 (min) (s, 2H) 3.91 (min) (t, J = 6.0 Hz, 2H) 3.82 (maj) (t, J = 6.0 Hz, 2H)
2.87–2.82 (m, 2H) 2.29 (maj) (d, J = 1.2 Hz, 3H) 2.19 (min) (d, J = 1.0 Hz, 3H). 13
C
NMR (DMSO-d6) d 164.2, 149.9, 146.3 (q), 141.9, 141.6, 136.9, 136.7, 136.6, 134.3,
123.6, 123.0, 122.9, 120.8, 119, 6, 117.7, 48.6, 42.6, 42.2, 27.4. HRMS (ESI) calc. for
C19H16Cl2F3N2O3 [M+H] 447.0490, found 447.0374.