Development of orally active nonpeptidic inhibitors of human neutrophil elastase

Article abstract of DOI:10.1021/jm000410y

5-Amino-2-phenylpyrimidin-6-ones, some of their desamino derivatives, and miscellaneous derivatives were synthesized and biologically evaluated on both in vitro activity and oral activity in an acute hemorrhagic assay. These compounds contained an α-keto-1,3,4-oxadiazole moiety to bind covalently to the Ser-195 hydroxy group of human neutrophil elastase (HNE). Among those tested, compounds 11a-c,e,i-l(F), 11d,e,k(H), 21d,e,k(F), and 21d,e(H) showed a good oral profile. RS-Mixture 3(H) was selected for clinical evaluation based on its oral potency, duration of action, enzyme selectivity, safety profile, and ease of synthesis. Structure -activity relationships (SARs) are discussed.

Full text of DOI:10.1021/jm000410y

1268
J . Med. Chem. 2001, 44, 1268-1285
Develop m en t of Or a lly Active Non p ep tid ic In h ibitor s of Hu m a n Neu tr op h il
Ela sta se
Kazuyuki Ohmoto,† Tetsuya Yamamoto,† Motohiro Okuma,† Toshihide Horiuchi,† Hirotoshi Imanishi,§
Yoshihiko Odagaki,† Kazuhito Kawabata,† Tomohiko Sekioka,† Yasushi Hirota,‡ Shozo Matsuoka,§
Hisao Nakai,*,† and Masaaki Toda†
Minase Research Institute, Ono Pharmaceutical Company, Ltd., Shimamoto, Mishima, Osaka 618-8585, J apan
J ohn C. Cheronis, Lyle W. Spruce, Albert Gyorkos, and Maciej Wieczorek
Cortech, Inc., 6850 North Broadway, Denver, Colorado 80221
Received September 20, 2000
5-Amino-2-phenylpyrimidin-6-ones, some of their desamino derivatives, and miscellaneous
derivatives were synthesized and biologically evaluated on both in vitro activity and oral activity
in an acute hemorrhagic assay. These compounds contained an R-keto-1,3,4-oxadiazole moiety
to bind covalently to the Ser-195 hydroxy group of human neutrophil elastase (HNE). Among
those tested, compounds 11a -c,e,i-l(F ), 11d ,e,k (H), 21d ,e,k (F ), and 21d ,e(H) showed a good
oral profile. RS-Mixture 3(H) was selected for clinical evaluation based on its oral potency,
duration of action, enzyme selectivity, safety profile, and ease of synthesis. Structure-activity
relationships (SARs) are discussed.
In tr od u ction
Human neutrophil elastase (HNE) is a serine protease
which is released from neutrophils in response to
inflammatory stimuli.1 HNE has a broad substrate
specificity with the ability to degrade a variety of diverse
structural proteins. Under normal conditions, the body
protects itself from the potential damaging effects of
extracellular HNE with the endogenous R1-proteinase
inhibitor (R1-PI). If the balance between protease and
antiprotease is in favor of protease due to a decrease in
the level of R1-PI, the excess HNE activity may lead to
tissue damage and the development of a disease such
as emphysema2 due to chronic inflammation. The excess
F igu r e 1. Covalent, hydrogen-bonding, and π-π interactions
between ONO-6818 and the catalytic site of PPE found in the
HNE produced by this imbalance hydrolyzes elastin, the
structural protein which gives the lungs their elasticity,
and is believed to initiate and/or contribute to the
development of diseases such as pulmonary emphy-
sema,2 chronic bronchitis,3 adult respiratory distress
syndrome,4 rheumatoid arthritis,5 atherosclerosis,6 cys-
tic fibrosis,7 chronic bowel disease,8 and other inflam-
matory disorders.9 It has been hypothesized that an
appropriate, small-molecular-weight inhibitor of HNE
could restore the imbalance between HNE and R1-PI
and would be therapeutically useful in the treatment
of such diseases.10 While a large number of synthetic
HNE inhibitors have been developed,11 only peptidyl
trifluoromethyl ketones have emerged as leading can-
didates to demonstrate the clinical utility of low-
molecular-weight synthetic proteinase inhibitors.12
Our research efforts have focused on the development
of mechanism-based13 inhibitors of elastase, in particu-
lar electrophilic ketones. A number of functional groups
crystal structure.18
which activate the carbonyl of peptidyl ketones for
nucleophilic addition by the active-site Ser-195 hydroxyl
group of HNE have been identified. Among the reported
functional groups,14 we focused our attention on R-ke-
toheterocycles such as R-keto-1,2,4-oxadiazole15 and
R-keto-1,3,4-oxadiazole. A predictable advantage of
R-ketooxadiazole over other electrophilic ketones was
that the better hydrophilic and/or electron-attracting
properties of the oxadiazoles than the reported hetero-
cycles16 and other electron-attracting moieties would
allow more subtle modulation of the physicochemical
properties of the inhibitor by introducing lipophilic
residues on their rings. As such, both the in vivo activity
and the in vitro potency could be finely tuned.
We were also interested in the possibility that incor-
poration of an appropriately positioned nitrogen atom
within the heterocyclic ring might further stabilize the
covalent complex by participating in a hydrogen-bonding
interaction with protonated active-site His-57 (Figure
1). This is analogous to the mechanism of inhibition
observed in an R-ketobenzoxazole inhibitor complexed
to PPE.17 A hydrogen-bonding interaction between the
* To whom correspondence should be addressed. Tel: +81-75-961-
1151. Fax: +81-75-962-9314. E-mail: hi.nakai@ono.co.jp.
† Minase Research Institute.
‡ Fukui Research Institute.
§ Development Headquarters.
10.1021/jm000410y CCC: $20.00 © 2001 American Chemical Society
Published on Web 03/10/2001

Orally Active Nonpeptidic Inhibitors of HNE
J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 8 1269
Sch em e 1. Synthesis of Aminopyrimidinone Derivatives 11a -m a
a
Reagents: (a) hydrazine hydrate; (b) HC(OMe)3 or HC(OEt)3, TsOH‚H2O; (c) (1) n-BuLi, MgBr2‚OEt2, THF, (2) 12, THF; (d) 4 N
HCl-dioxane; (e) 13(H) or 13(F ), EDC‚HCl, HOBt‚H2O, NMM, DMF; (f) Dess-Martin periodinane or Swern oxidation; (g) AlCl3, anisole,
CH3NO2, CH2Cl2; (h) 35% HBr/AcOH; (i) TMSCl, MeOH; (j) NaH, MeI, THF.
R-ketoheterocyclic inhibitors and His-57 was speculated
to be beneficial for the fast and effective binding of the
inhibitor to the enzyme in the covalent bond formation
with Ser-195.
tively. Compounds 11k (H) and 11k -m (F )21 were syth-
esized from 4k -m which were prepared from 14k -m ,
respectively.
Synthesis of desaminopyrimidinone derivatives 21d,e-
(H) and 21d ,e,k (F ) is described in Scheme 2. Com-
pounds 17(H) and 17(F ) were synthesized from the
corresponding amidines 16(H) and 16(F ), respectively,
which were obtained from their corresponding imidates
15(H) and 15(F ), respectively. Deprotection of their
dimethyl acetals 17(H) and 17(F ) afforded 18(H) and
18(F ). These aldehydes were converted to the carboxylic
acids 19(H) and 19(F ) under oxidation conditions.
Condensation of these carboxylic acids with 8d ,e,k
afforded 20d ,e(H) and 20d ,e,k (F ), respectively. R-Ke-
tooxadiazoles 21d ,e(H) and 21d ,e,k (F ) were obtained
from their corresponding alcohols by Dess-Martin or
Swern oxidation.
We report herein the synthesis and activities of a
novel class of HNE inhibitors: the nonpeptidyl R-keto-
1,3,4-oxadiazoles. A number of the compounds from this
series are orally active inhibitors of HNE with potent
Ki values in the nanomolar to subnanomolar range. The
crystal structure of the inhibitor 3(H) supports the
hypothesis that binding interactions with both the
enzyme active-site serine hydroxyl group and histidine
imidazole ring (Figure 1) are important for optimal in
vitro activity.18
Ch em istr y
Compound 1a can be structurally divided into two
parts, a left half and a right half. Modifications were
carried out on each part separately. Aminopyrimidinone
derivatives 11a -m , in which the right half was chemi-
cally modified, were prepared as outlined in Scheme 1.
Oxadiazoles 6a -j were synthesized from acyl hy-
drazides 5a -j. Compounds 5a ,f,h were commercially
available. Compounds 5b-e,g,i,j were prepard from
their corresponding esters 4b-e,g,i,j, respectively. Meth-
yl 2,2-dimethyphenylacetates 4k -m were prepared by
the gem-dialkylation of 14k -m . Compounds 4b-e,g,i,j
and 14k -m were commercially available. Addition of
anions prepared from 6a -j in the presence of n-BuLi/
MgBr2‚OEt2 with 1219 afforded 7a -j. Acidic deprotec-
tion of 7a -j provided amino alcohols 8a -j. Amide
formation of 8a -j with 13(H)20 or 13(F )20 gave 9d ,e-
(H ) or 9a -j(F ), respectively. Dess-Martin or Swern
oxidation of 9d ,e(H) and 9a -j(F ) afforded 10d ,e(H)
and 10a -j(F ), respectively. Deprotection of 10d ,e(H)
and 10a -j(F ) afforded 11d ,e(H) and 11a -j(F ) respec-
Modification of the left half of 1a was carried out as
described in Schemes 3-5. Synthesis of 24a -c,e-g is
described in Scheme 3. Compounds 24a -c,e-g were
synthesized from 23a -c,e-g, respectively, which were
prepared by the condensation of 22a -c,e-g with 8e in
the presence of EDC. Compounds 22a -c were prepared
from the urea 26a -c which were obtained from their
corresponding amino esters 25a -c by a reaction with
ethyl isocyanatoacetate. Compound 22e was prepared
by the deprotection of 39 which was prepared by
N-methanesulfonylation of 38. The carboxylic acid 22g
was obtained by alkaline hydrolysis of 41 which was
prepared by O-alkylation of the pyridone 40 with ethyl
bromoacetate.
Synthesis of tetrahydroisoquinoline and of indoline
derivatives 24h -m is described in Scheme 4. Conden-
sation of 27a ,b and the amino alcohol 8e afforded 28a ,b.
Acidic deprotection provided 29a ,b which were acylated
again with isopropoxycarbonyl chloride to give 30a ,b.

1270 J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 8
Ohmoto et al.
Sch em e 2. Synthesis of Desaminopyrimidinone Derivatives 21d ,e,k a
a
Reagents: (a) aminoacetaldehyde dimethyl acetal, MeOH; (b) 3-ethoxyacrylic acid ethyl ester; (c) 1 N HCl(aq), THF; (d) NaClO2,
NaH2PO4, 2-methyl-2-butene, t-BuOH, H2O; (e) 8d , 8e, or 8k , EDC‚HCl, HOBt‚H2O, NMM, DMF; (f) Dess-Martin periodinane or Swern
oxidation.
Sch em e 3. Synthesis of Miscellaneous Derivatives 24a -c,e-ga
a
Reagents: (a) EDC‚HCl, HOBt‚H2O, NMM, DMF; (b) Dess-Martin periodinane or Swern oxidation; (c) ethyl isocyanatoacetate,
triethylamine, EtOAc; (d) concd HCl; (e) methanesulfonyl chloride, NMM, CH2Cl2; (f) 90% TFA/H2O; (g) ethyl bromoacetate, K2CO3,
DMF; (h) 1 N LiOH(aq), DME.
Oxidation of 30a ,b afforded 24h ,i. Acylation of 29a ,b
with 32, which was prepared by the tritylation of 31,
in the presence of EDC afforded 33a ,b. Oxidation of
33a ,b gave R-ketooxadiazoles 34a ,b which were con-
verted to 24j,k , respectively, by acidic deprotection.
N-Acylation of 29a ,b with Boc-L-valine afforded 35a ,b
whose acidic deprotection provided 36a ,b. N-Acylation
of 36a ,b with nicotinic acid gave 37a ,b. Oxidation of
37a ,b afforded 24l,m , respectively.
pyrimidin-6-one derivative,20 was converted to 28 by a
condensation reaction with 8e in the presence of EDC.
Oxidation of 28 afforded 29 which was converted to 24d
by deprotection with aluminum chloride.
Synthesis of 3(H) (ONO-6818) was carried out as
described in Scheme 6. Oxidation of optically active
9e(H) followed by its epimerization under basic condi-
tions afforded RS-mixture 42 which was converted to
3(H) by deprotection with aluminum chloride.
The 2-(pyridin-3-yl)pyrimidinone derivative 24d was
synthesized from 27 as outlined in Scheme 5. Compound
27, which was prepared from 3-cyanopyridine by the
same procedure used in the preparation of 2-phenyl-
Resu lts a n d Discu ssion
Two kinds of heterocycles were investigated for their
ability to activate the carbonyl group of peptidyl ketone

Orally Active Nonpeptidic Inhibitors of HNE
J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 8 1271
Sch em e 4. Synthesis of Tetrahydroisoquinoline and Indoline Derivatives 24h -m a
a
Reagents: (a) 8e, EDC‚HCl, HOBt‚H2O, NMM, DMF; (b) 4 N HCl in EtOAc or dioxane; (c) isopropyl chloroformate, NMM, CH2Cl2;
(d) Dess-Martin periodinane, CH2Cl2; (e) Ph3CCl, pyridine, DMF; (f) 32, EDC‚HCl (HOBt‚H2O), NMM, DMF; (g) Dess-Martin periodinane,
CH2Cl2; (h) (1) 95% TFA/H2O, (2) 4 N HCl in EtOAc or dioxane; (i) BocValCOF, 2,6-di-tert-butylpyridine, DMAP, CH2Cl2; (j) Boc-L-valine,
EDC‚HCl, HOBt‚H2O, NMM, DMF; (k) 4 N HCl in EtOAc; (l) nicotinic acid, EDC‚HCl, NMM, CH2Cl2; (m) Dess-Martin periodinane,
CH2Cl2.
Sch em e 5. Synthesis of Pyrimidinone Derivative 24d a
tidic, orally active inhibitor of HNE as a new clinical
candidate, a variety of nonpeptidic portions for the
tripeptide backbone Cbz-Val-Pro-Val were investigated
for their ability to make the synthesized inhibitors orally
active. Among the compounds tested, 5-amino-2-phen-
ylpyrimidinones and corresponding desamino deriva-
tives demonstrated good oral profiles as shown in Tables
1 and 2, respectively. The binding constants were
derived from the inhibiton of the HNE-catalyzed hy-
drolysis of MeO-Suc-Ala-Ala-Pro-Val-pNa.22 All of the
inhibitors studied were competitive, reversible inhibitors
of HNE and displayed fast-binding inhibition. The
heterocyclic derivatives 1a ,b afforded extremely potent
inhibitors of HNE (Chart 1). The 1,3,4-oxadiazole de-
rivative 1a , with a Ki of 0.025 nM, is the most potent of
the series. Thus, the 1,3,4-oxadiazole is one of the most
potent groups so far reported for activating peptidyl
ketones.20,23
a
Reagents: (a) 8e, EDC‚HCl, HOBt‚H2O, NMM, DMF; (b)
Dess-Martin periodinane; (c) AlCl3, anisole, CH3NO2, CH2Cl2.
Sch em e 6. Synthesis of 3(H) (ONO-6818)a
We focused our attention on the screening of a
nonpeptidic substitute possessing a good oral profile for
the tripeptide backbone Cbz-Val-Pro-Val. Structural
hybridization of 1 and 2 reported by Zeneca23 as an
orally active elastase inhibitor afforded potent inhibitors
of HNE (Table 1). All of the inhibitors 11a -m described
in Table 1 exhibited more potent in vivo activity than
2. And 5-benzyl-1,3,4-oxadiazoles 11i-m showed more
potent in vitro activity than 5-alkyl-1,3,4-oxadiazoles
11a -e. Introduction of a m-methyl group into the benzyl
moiety of 11i(F ) afforded 11j(F ) with an increased
inhibitory constant. gem-Dimethylation of the benzylic
position of 11i,j(F ) afforded 11k ,l(F ) with nearly the
same and a slightly more potent Ki value, respectively.
Substitution of the m- and p-positions of the benzylic
phenyl portion with a methylenedioxy group produced
11m (F ) with slightly lower inhibitory activity than 11k -
(F ). Replacement of the p-fluorine atom on the 5-amino-
2-phenylpyrimidin-6-one of 11k (F ) with hydrogen pro-
a
Reagents: (a) oxalyl chloride, DMSO, CH2Cl2, -78 °C; (b)
triethylamine, rt, 40 h; (c) AlCl3, anisole, CH3NO2, CH2Cl2.
for nucleophilic addition by the hydroxyl group of Ser-
195 of HNE. Among those tested, 1,3,4-oxadiazoles
always exhibited more potent Ki values than the cor-
responding 1,2,4-oxadiazoles,15 both of which showed
very potent Ki values when the tripeptidyl backbone
Cbz-Val-Pro-Val was used as a ketone scaffold. Since
the final goal of this project was to identify a nonpep-

1272 J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 8
Ohmoto et al.
Ta ble 1. Biological Data of Aminopyrimidinone Derivatives
11a -m
Ta ble 2. Biological Data of Desaminopyrimidinone Derivatives
21d ,e(H), 21d ,e(F ), and 21k (F )
a
Inhibition of HNE-catalyzed hydrolysis of the synthetic sub-
strate MeO-Suc-Ala-Ala-Pro-Val-pNa. b Inhibition of HNE-induced
lung hemorrhage in hamsters (n ) 6-10). Test compounds were
administered orally 1 h before intratracheal instillation of HNE
(10 U/lung).
(Scheme 1) includes an anion formation at position-2 of
the 5-substituted oxadiazole. It is easily predictable that
selective anion formation at position-2 of the 5-substi-
tuted oxadiazoles causes a problem if the carbon atom
attached to position-5 is not a tertiary one. Compound
11d (F ) was prepared for the same reason as described
above and retained a potent Ki of 15.3 nM. Removal of
the fluorine atom of 11d ,e(F ) afforded 11d ,e(H), re-
spectively, with slightly higher inhibitory activity.
In an attempt to understand the factors responsible
for oral potency in this set of compounds, we have
divided these inhibitors into three groups on the basis
of their structural features. The first group (11a -e)
contains inhibitors with the oxadiazoles substituted
with an aliphatic alkyl group such as a methyl, isoprop-
yl, n-butyl, or tert-butyl. The second group (11f-h )
contains inhibitors which have an aromatic group
directly attached to the oxadiazole ring; these com-
pounds exhibited relatively low Ki values compared with
the members of the first group. The third group
(11i-m ) contains inhibitors possessing oxadiazoles
substituted with benzyl groups, which exhibited the
most potent in vitro activities of all. With respect to oral
profiles, inhibitors of the first group demonstrated a
relatively higher potency than those of the third group
(11i-m ) despite their lower Ki values. The inconsistency
between oral potency and Ki values is presumed to
result from the better solubility of the first group
relative to that of the third group. According to our own
investigation, solubility data of 11e,k (H) under the
same conditions (Table 6) clearly showed that inhibitors
possessing alkyl substituents on their oxadiazoles such
as 11e(H) demonstrated better solubility than inhibitors
possessing benzyl substituents on their oxadiazoles such
as 11k (H). Inhibitors of the second group (11f-h ) did
not exhibit oral activity despite their potent Ki values.
We speculate that a presumed lower solubility based
on the longer conjugated system of the phenyloxadi-
azoles could be one of the reasons for their oral inactiv-
a
Inhibition of HNE-catalyzed hydrolysis of the synthetic sub-
strate MeO-Suc-Ala-Ala-Pro-Val-pNa. b Inhibition of HNE-induced
lung hemorrhage in hamsters (n ) 6-10). Test compounds were
administered orally 1 h before intratracheal instillation of HNE
(10 U/lung). c See ref 15. NS, not significant.
d
vided 11k (H) with a decreased Ki value. Conversion of
the benzylic moiety into a phenyl or p-methoxyphenyl
moiety of 11i(F ) afforded 11f(F ) or 11g(F ) with signifi-
cant loss of inhibitory activity. Replacement of the
phenyl moiety on the oxadiazole of 11f(F ) with a
pyridin-3-yl group gave 11h (F ) also with much lower
inhibitory activity compared to 11i(F ). Replacement of
the benzylic portion of 11i-m with an aliphatic moiety
afforded 11a -e. 5-Methyl-1,3,4-oxadiazole 11a (F ) ex-
hibited a Ki of 14.0 nM. Introduction of an isopropyl and
an n-butyl group instead of the methyl group into the
oxadiazole gave 11b,c(F ), respectively, with slightly
more potent inhibitory activity. tert-Butyloxadiazole
11e(F ) which showed nearly the same Ki value as 11c-
(F ) was also investigated. Our scheme for its synthesis

Orally Active Nonpeptidic Inhibitors of HNE
J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 8 1273
Ch a r t 1. Structural Hybridization of 1 and 2
Ta ble 3. Biological Data of Miscellaneous Derivatives 24a -g
Ta ble 4. Biological Data of Tetrahydroisoquinoline and
Indoline Derivatives 24h -m
a
Inhibition of HNE-catalyzed hydrolysis of the synthetic sub-
strate MeO-Suc-Ala-Ala-Pro-Val-pNa. b Inhibition of HNE-induced
lung hemorrhage in hamsters (n ) 6-10). Test compounds were
administered orally 1 h before intratracheal instillation of HNE
(10 U/lung). c NT, not tested. Dose dependency was not observed.
d
e NS, not significant.
ity. As described in a previous paper, RS-mixture 3(H),
S-isomer 11e(H), and its R-isomer 11n (H)24 exhibited
nearly the same oral potency. This was ascribed to the
presumed epimerization of the two enantiomers in the
living body because of their easily enolizable structures.
Supportive evidence is shown in Figure 2. Gradual
racemization of both of the enantiomers 11e,n (H)24 was
observed following their incubation in the whole blood
of hamster. The evidence described above was also
obtained in the whole blood of rat and human. On the
basis of both of the oral profiles and reasons of synthesis,
RS-mixture 3(H) was selected as a clinical candidate
(ONO-6818). The final ED50 value following oral dosing
of 3(H) (ONO-6818) was 1.4 mg/kg.25
a
Inhibition of HNE-catalyzed hydrolysis of the synthetic sub-
strate MeO-Suc-Ala-Ala-Pro-Val-pNa. b Inhibition of HNE-induced
lung hemorrhage in hamsters (n ) 6-10). Test compounds were
administered orally 1 h before intratracheal instillation of HNE
(10 U/lung). c NS, not significant.

1274 J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 8
Ta ble 5. Pharmacokinetic Parametersa in Rat for 3(H) (ONO-6818)b
Ohmoto et al.
a
b
Data are shown as mean ( SD (n ) 4). Compound was administered orally as a suspension in 0.5% CMC or intravenously as a
solution in 35% HP-â-CD. c Pharmacokinetic half-life time was determined in the period 6-24 h after dosing. Maximum concentration
d
of unchanged drug in plasma recorded in the period 0-24 h after dosing. e Time of maximum concentration. f Integrated area under the
g
h
concentration versus time curve. Oral bioavailability was measured by the ratio of intravenous to oral AUC. n ) 3.
Ta ble 6. Solubility of 11e,k (H)
a
b
First fluid (J P13th) (pH ) ca. 1.2). 1/14 M phosphate citrate
buffer (pH ) ca. 4.0). c Physiological saline (pH ) ca. 5.5). 1/14
d
M phosphate buffer (pH ) ca. 7.4). e NT, not tested.
Compound 3(H) (ONO-6818) exhibited highly potent
oral activity, and sustained activity was observed for
more than 8 h following oral dosing. Oral bioavailability
was excellent in three species (rat, 51%; dog, 31%;
monkey, 18%). As a representative example, oral pro-
files of 3(H) are shown in Table 5. Compound 3(H) was
ineffective against a variety of proteases such as pan-
creatic elastase, proteinase 3, trypsin, murine macro-
phage elastase, Pseudomonas aeruginosa elastase,
cathepsin G, plasmin, thrombin, and type I collagenase
at a concentration 100 times that which inhibited HNE.
Biological data of several desaminopyrimidinone de-
rivatives, 21d ,e(H) and 21d ,e,k (F ), were investigated.
As shown in Table 2, all of the compounds exhibited
lower Ki values than their corresponding aminopyrimi-
dinone derivatives. Also in this case, compounds 21d ,e-
(H) and 21d ,e(F ) possessing the oxadiazoles substituted
with an aliphatic alkyl group demonstrated more potent
oral activity (ED50) than 21k (F ) possessing a 5-benzyl-
oxadiazole, while they had much lower Ki values relative
to that for 21k (F ).
F igu r e 2. Racemization of 11n (H) in hamster whole blood:
To a solution of test compound in EtOH (1 µg/10 µL) was added
200 µL of blood (n ) 3). The mixture, mixed well, was
incubated for 60 min at 37 °C. After incubation for 0, 5, 15,
30, and 60 min, the reaction was quenched with water (0.5
mL)-benzene (2.5 mL). After centrifugation at ca. 1500g for
5 min, the organic layer was evaporated. A solution of the
residue in the mobile phase [0.02 M KH2PO4 (pH 3)/EtOH
(90/10)] was analyzed by HPLC [column: ULTRON ES-OVM,
4.6 × 150 mm (Shinwa Chemical Industries, Ltd.); detection:
UV at 312 nm].
alkoxypyridine derivative 24g was not orally active as
predicted from its weak Ki value.
Biological data of the tetrahydroisoquinoline and
indoline derivatives 24h -m are shown in Table 4.
N-Isopropoxycarbonylindoline derivative 24h and N-
isopropoxycarbonyltetrahydroisoquinoline derivative 24i
exhibited moderate and weak in vitro activity, respec-
tively. N-Imidazolyl derivatives 24j,k showed quite
potent and moderate in vitro activity, respectively. The
compound 24j demonstrated 81% inhibition at a dose
of 30 mg/kg (po), while it did not show dose-dependent
efficacy. Nicotinoyl derivatives 24l,m showed the most
potent in vitro activity among the tested compounds of
Tables 3 and 4, but neither of them showed significant
oral efficacy.
Many other peptidomimetics as a surrogate for Cbz-
Val-Pro-Val were investigated (Tables 3, 4). Hydantoin
derivatives 24a -c demonstrated no activity in animal
models as expected from their relatively weak in vitro
activity. 5-Amino-2-(3-pyridyl)pyrimidinone 24d , N-
methanesulfonyl-Val-Pro derivative 24e, and benzodi-
azepine derivative 24f did not exhibit oral activity, while
they showed quite potent in vitro activity. 6-Phenyl-2-

Orally Active Nonpeptidic Inhibitors of HNE
J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 8 1275
mmol) was added. The reaction mixture was allowed to warm
to -45 °C. The resulting white slurry was stirred at -45 °C
for another 1.5 h, and treated with N-[(1S)-1-(methylethyl)-
2-oxoethyl](tert-butoxy)carboxamide (12)19 (90.0 g, 448 mmol)
in THF (60 mL). The reaction temperature was raised to -20
°C. After being stirred for 3.5 h, the reaction mixture was
quenched with saturated NH4Cl, and extracted with EtOAc.
The organic layer was washed with water (×3) and then brine,
dried over anhydrous Na2SO4, and concentrated in vacuo. The
crude product was purified by column chromatography on
silica gel [Merck 7734, EtOAc/n-hexane (1/20 f 1/1)] to give
the Boc alcohol 7e (76.8 g, 53%) as a white amorphous solid:
TLC Rf ) 0.42, n-hexane/EtOAc (1/1); 1H NMR (200 MHz,
CDCl3) δ 5.18-4.90 (m, 2H), 4.51 and 4.12 (m × 2, 1H), 3.91
and 3.66 (m × 2, 1H), 1.95 (m, 1H), 1.42, 1.41 and 1.34 (s × 3,
18H), 1.15-0.90 (m, 6H).
Further experimental evidence for the proposed bind-
ing mechanism of this series was obtained from the
X-ray crystal structure of an R-ketooxadiazole bound to
PPE.18 In this complex, one of the oxadiazole nitrogen
atoms was observed to possess the appropriate geometry
and distance (2.80 Å) from the nitrogen atom of His-57
to participate in a strong hydrogen-bonding interaction.
Su m m a r y
We have discovered a new series of nonpeptidic orally
active HNE inhibitors which contain a 1,3,4-oxadiazole.
A number of the 3-aminopyrimidinone R-keto-1,3,4-
oxadiazoles, most notably 3(H), 3(F ), 11d ,e,j(H), and
11d ,e,k (F ), were extremely potent inhibitors of HNE.
The data from this study combined with the crystal
structure study18 confirmed the importance of the
hydrogen bond between the heterocyclic ring of the
inhibitor and the imidazole ring of His-57 in the covalent
enzyme-inhibitor complex. This is a report of the first
clinical candidate for a nonpeptidic orally active HNE
inhibitor.
(2S)-2-Am in o-1-(5-ter t-bu tyl-1,3,4-oxa d ia zol-2-yl)-3-m e-
th ylbu ta n -1-ol Hyd r och lor id e (8e). A mixture of the Boc
alcohol 7e (76.3 g, 233 mmol) and 4 N HCl in dioxane (1 L)
diluted with dioxane (200 mL) was vigorously stirred at room
temperature for 2 h. Concentration of the reaction mixture and
then solidification with ether followed by azeotropic removal
of water with benzene gave the amino alcohol 8e (66.1 g)
quantitatively. The formed product was used for the next
reaction without further purification: TLC Rf ) 0.30 and 0.26,
1
CHCl3/MeOH (10/1); H NMR (200 MHz, CDCl3) δ 8.34 and
Exp er im en ta l Section
8.24 (m × 2, 2H), 5.60 (m, 1H), 3.97-3.60 (m, 2H), 2.08 (m,
Gen er a l Dir ection s. Analytical samples were homoge-
1H), 1.42 and 1.41 (s × 2, 9H), 1.25-0.95 (m, 6H).
neous on TLC and afforded spectroscopic results consistent
N -[(1S )-2-(5-t er t -B u t y l-1,3,4-o x a d ia zo l-2-y l)-2-h y -
dr oxy-1-(m eth yleth yl)eth yl]-2-{6-oxo-2-ph en yl-5-[(ph en yl-
m eth oxy)ca r bon yla m in o]h yd r op yr im id in yl}a ceta m id e
(9e(H)). To a stirred mixture of 2-{6-oxo-2-phenyl-5-[(phenyl-
methoxy)carbonylamino]hydropyrimidinyl}acetic acid (13(H))
(30.0 g, 79.2 mmol), prepared according to Zeneca’s proce-
dure,20 the amino alcohol 8e (23.0 g, 87.1 mmol) and HOBt‚
H2O (13.3 g, 87.1 mmol) in DMF (263 mL) were added EDC‚
HCl (16.7 g, 87.1 mmol) and then N-methylmorpholine (9.60
mL, 87.1 mmol) under Ar at 0 °C. The reaction mixture was
stirred at room temperature for 3.5 h, and then evaporated.
The residue was dissolved in EtOAc and washed with water.
The organic layer was washed successively with saturated
NH4Cl, saturated NaHCO3, water and brine, and dried over
anhydrous Na2SO4. Concentration of the organic layer afforded
the alcohol 9e(H) (50.1 g, quant) as a beige amorphous powder.
The product was used for the next reaction without further
purification: TLC Rf ) 0.53 and 0.38, EtOAc; MS (APCI, pos.
40 V) m/z ) 589 (M + H)+; 1H NMR (200 MHz, CDCl3) δ 8.81
and 8.71 (m × 2, 1H), 7.66-7.26 (m, 11H), 7.11 and 6.70 (d
and m, J ) 10.0 Hz, 1H), 5.20 (s, 2H), 5.15-5.00 (m, 1H), 4.70-
4.22 and 4.15-3.60 (m × 2, 4H), 2.10-1.60 (m, 1H), 1.39 and
1.35 (s × 2, 9H), 1.12-0.87 (m, 6H).
1
with assigned structures. All H NMR spectra were obtained
using a Varian GEMINI-200, VXR-200s, or MERCURY300
spectrometer. Mass spectra were obtained on a HITACHI
M1200H or J EOL J MS-DX303HF spectrometer. IR spectra
were measured on a Perkin-Elmer FT-IR 1760X or J ASCO FT/
IR-430 spectrometer. Elemental analyses for carbon, hydrogen,
and nitrogen were carried out by the Analytical Section of Ono
Pharmaceutical Co., Ltd. on a Perkin-Elmer PE2400 SeriesII
CHNS/O analyzer and are within (0.4% of theory for the
formulas given. Optical rotations were measured by J ASCO
DIP-1000 polarimeter. Column chromatography was carried
out on silica gel [Merck silica gel 60 (0.063-0.200 mm) or Fuji
Silysia FL60D]. Thin-layer chromatography was performed on
silica gel (Merck TLC or HPTLC plates, silica gel 60 F254). The
following abbreviations are used: THF, tetrahydrofuran; DMF,
N,N-dimethylformamide; DME, ethylene glycol dimethyl ether;
DMSO, dimethyl sulfoxide; EDC‚HCl, 1-[3-(dimethylamino)-
propyl]-3-ethylcarbodiimide hydrochloride; HOBt‚H2O, N-hy-
droxybenzotriazole hydrate.
P iva lic Acid Hyd r a zid e (5e). A mixture of methyl pivalate
(4e) (11.5 mL, 86.4 mmol) and hydrazine hydrate (6.30 mL,
130 mmol) was refluxed for 28 h. After being cooled to room
temperature, the reaction mixture was evaporated under
reduced pressure, then dried by azeotropic removal of the
solvent with toluene. The residue was dissolved in CHCl3 and
washed with brine. The aqueous layer was further extracted
with CHCl3 three times. The combined organic layers were
dried over anhydrous Na2SO4, and concentrated to afford 5e
(6.03 g, 60%) as a white waxy solid: TLC Rf ) 0.50, CHCl3/
N-[(1S)-2-(5-ter t-Bu tyl-1,3,4-oxa d ia zol-2-yl)-1-(m eth yl-
eth yl)-2-oxoeth yl]-2-{6-oxo-2-p h en yl-5-[(p h en ylm eth oxy)-
ca r ba m id o]h yd r op yr im id in yl}a ceta m id e (10e(H)). To a
stirred solution of oxalyl chloride (0.790 mL, 9.08 mmol) in
CH2Cl2 (20 mL) was added dropwise a solution of DMSO (1.29
mL, 18.2 mmol) in CH2Cl2 (2 mL) under Ar at -70 to -60 °C.
A solution of the alcohol 9e(H) (2.62 g, ca. 4.17 mmol) in CH2-
Cl2 (20 mL) was added. After being stirred at -70 °C for 2 h,
the reaction mixture was treated with N-methylmorpholine
(3.99 mL, 36.3 mmol), then stirred at -20 °C for 30 min. The
resulting mixture was acidified with 1 N HCl, and stirred
vigorously at room temperature for a while, then extracted
with EtOAc. The organic layer was washed successively with
1 N HCl, water and brine, dried over anhydrous Na2SO4, and
concentrated in vacuo. Purification of the residue by silica gel
column chromatography [FL60D, EtOAc/n-hexane (1/4)] gave
the Cbz ketone 10e(H) (2.13 g, 87% in 2 steps) as a white
amorphous solid: TLC Rf ) 0.40, EtOAc/n-hexane (1/1); 1H
NMR (200 MHz, CDCl3) δ 8.78 (br s, 1H), 7.60-7.33 (m, 11H),
6.71 (d, J ) 8.4 Hz, 1H), 5.44 (dd, J ) 8.4, 4.8 Hz, 1H), 5.23
(s, 2H), 4.64 and 4.60 (d × 2, J ) 15.0 Hz, 1H × 2), 2.50 (m,
1H), 1.47 (s, 9H), 1.06 and 0.87 (d × 2, J ) 6.6 Hz, 3H × 2);
1
MeOH (9/1); MS (APCI, pos. 40 V) m/z ) 117 (M + H)+; H
NMR (200 MHz, CDCl3) δ 7.09 (br s, 1H), 3.86 (br s, 2H), 1.19
(s, 9H).
2-ter t-Bu tyl-1,3,4-oxa d ia zole (6e). In a round-bottomed
flask equipped with a standard distillation apparatus, a
mixture of the hydrazide 5e (8.80 g, 76.0 mmol), trimethyl
orthoformate (12.5 mL, 114 mmol) and p-toluenesulfonic acid
monohydrate (217 mg, 1.14 mmol) was heated at 80-120 °C
removing MeOH by distillation. Distillation in vacuo of the
residue afforded the oxadiazole 6e (6.58 g, 69%) as a pale
1
yellow liquid: TLC Rf ) 0.68, CHCl3/MeOH (10/1); H NMR
(200 MHz, CDCl3) δ 8.31 (s, 1H), 1.43 (s, 9H).
ter t-Bu tyl N-[(1S)-2-(5-ter t-Bu tyl-1,3,4-oxa d ia zol-2-yl)-
2-h yd r oxy-1-(m et h ylet h yl)et h yl]ca r b a m a t e (7e). To a
stirred solution of the oxadiazole 6e (62.1 g, 493 mmol) in THF
(1.65 L) was added dropwise n-BuLi (493 mmol) in n-hexane
under Ar at -70 °C. After 40 min, MgBr2‚OEt2 (127 g, 493
optical rotation [R]26 -21.9 (c 0.7, MeCN).
D

1276 J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 8
Ohmoto et al.
N-[(1S)-2-(5-ter t-Bu tyl-1,3,4-oxa d ia zol-2-yl)-1-(m eth yl-
eth yl)-2-oxoeth yl]-2-(5-a m in o-6-oxo-2-p h en ylh yd r op yr i-
m id in yl)a ceta m id e (11e(H)). To a stirred solution of the Cbz
ketone 10e(H) (2.10 g, 3.58 mmol) and anisole (2.34 mL, 21.5
mmol) in CH2Cl2 (58 mL) was added dropwise a solution of
aluminum chloride (2.87 g, 21.5 mmol) in CH3NO2 (28 mL)
under Ar at 0 °C. The reaction mixture was stirred at room
temperature for 2 h, then quenched with crushed ice, and
extracted with EtOAc. The organic layer was washed with
water and then brine, dried over anhydrous Na2SO4 and
concentrated in vacuo. Purification of the residue by silica gel
column chromatography [FL60D, MeOH/CHCl3 (1/25 f 1/20)]
gave the ketone 11e(H) (1.42 g, 88%) as an off-white powder:
TLC Rf ) 0.49, MeOH/CHCl3 (1/10); MS (APCI, pos. 40 V) m/z
) 453 (M + H)+; IR (KBr) 3457, 2975, 1661, 1614, 1542, 1441,
1304, 1205, 977, 706, 615 cm-1; 1H NMR (200 MHz, CDCl3) δ
7.58-7.38 (m, 6H), 6.88 (br d, J ) 8.4 Hz, 1H), 5.45 (dd, J )
8.4, 5.0 Hz, 1H), 4.66 and 4.60 (d × 2, J ) 15.4 Hz, 1H × 2),
4.06 (m, 2H), 2.52 (m, 1H), 1.48 (s, 9H), 1.07 and 0.88 (d × 2,
1030, 819, 774, 705 cm-1; 1H NMR (200 MHz, CDCl3) δ 7.60-
7.34 (m, 6H), 6.87 (d, J ) 8.2 Hz, 1H), 5.41 (dd, J ) 8.2, 4.8
Hz, 1H), 4.66 (d, J ) 15.4 Hz, 1H), 4.57 (d, J ) 15.4 Hz, 1H),
4.33-3.72 (m, 2H), 2.62-2.37 (m, 1H), 1.61 (s, 3H), 1.51-1.39
(m, 2H), 1.14-0.99 (m, 5H), 0.87 (d, J ) 6.8 Hz, 3H); optical
rotation [R]26 -26.9 (c 0.5, CH3CN). Anal. (C23H26N6O4‚
D
0.2H2O) C, H, N.
N-{(1S)-2-[5-(1-Met h ylcyclop r op yl)-1,3,4-oxa d ia zol-2-
yl]-1-(m et h ylet h yl)-2-oxoet h yl}-2-[5-a m in o-2-(4-flu or o-
p h en yl)-6-oxoh yd r op yr im id in yl]a ceta m id e (11d (F )). De-
rived from 13(F ) and 8d which was prepared from 4d : pale
yellow powder; TLC Rf ) 0.41, EtOAc; MS (APCI, pos. 40 V)
m/z ) 469 (M + H)+; IR (KBr) 3455, 3339, 3055, 2969, 2936,
2877, 1664, 1610, 1548, 1510, 1470, 1437, 1409, 1386, 1314,
1227, 1203, 1161, 1098, 1019, 981, 954, 928, 900, 846, 818,
788, 749, 734, 701, 638, 531 cm-1; 1H NMR (200 MHz, CDCl3)
δ 7.54 (m, 2H), 7.49 (s, 1H), 7.12 (t, J ) 8.4 Hz, 2H), 6.92 (d,
J ) 8.0 Hz, 1H), 5.39 (dd, J ) 8.0, 5.0 Hz, 1H), 4.60 (s, 2H),
4.07 (br s, 2H), 2.48 (m, 1H), 1.62 (s, 3H), 1.45 (m, 2H), 1.08
J ) 6.8 Hz, 3H × 2); optical rotation [R]26 -9.0 (c 0.6, THF),
(m, 5H), 0.88 (d, J ) 6.6 Hz, 3H); optical rotation [R]28 -28.2
D
D
-24.9 (c 0.5, MeCN). Anal. (C23H28N6O4‚0.2H2O) C, H, N.
(c 1.0, CH3CN). Anal. (C23H25FN6O4) C, H, N.
P r ep a r a tion of 11d (H) a n d 11a -j(F ). Using essentially
the same procedures as described for the preparation of 11e-
(H), the following compounds were prepared.
N-[(1S)-2-(5-ter t-Bu tyl-1,3,4-oxa d ia zol-2-yl)-1-(m eth yl-
et h yl)-2-oxoet h yl]-2-[5-a m in o-2-(4-flu or op h en yl)-6-oxo-
h yd r op yr im id in yl]a ceta m id e (11e(F )). Derived from 13(F )
and 8e which was prepared from 4e: off-white amorphous
solid; TLC Rf ) 0.29, EtOAc; MS (APCI, pos. 40 V) m/z ) 471
(M + H)+, 377; IR (KBr) 3461, 3314, 3076, 2976, 2937, 2878,
1714, 1695, 1641, 1609, 1543, 1508, 1463, 1435, 1408, 1393,
1370, 1302, 1222, 1205, 1162, 1111, 1098, 1048, 1017, 984, 969,
937, 895, 846, 825, 791, 761, 733, 695, 644, 606, 548, 534, 487,
N-[(1S)-1-(Meth yleth yl)-2-(5-m eth yl-1,3,4-oxa d ia zol-2-
yl)-2-oxoet h yl]-2-[5-a m in o-2-(4-flu or op h en yl)-6-oxoh y-
d r op yr im id in yl]a ceta m id e (11a (F )). Derived from 13(F )
and 8a which was prepared from 5a : pale yellow powder; TLC
Rf ) 0.29, EtOAc; MS (FAB, pos. glycerol + m-NBA) m/z )
429 (M + H)+, 246, 218, 206; IR (KBr) 3462, 3365, 3284, 3078,
2968, 2878, 1716, 1670, 1614, 1559, 1510, 1437, 1405, 1285,
1231, 1201, 1162, 1054, 1041, 979, 964, 899, 844, 816, 786,
423 cm-1 1H NMR (200 MHz, CDCl3) δ 7.60-7.48 (m, 2H),
;
7.49 (s, 1H), 7.19-7.06 (m, 2H), 6.90 (d, J ) 8.6 Hz, 1H), 5.44
(dd, J ) 8.2, 5.0 Hz, 1H), 4.60 (s, 2H), 4.07 (br s, 2H), 2.53 (m,
1H), 1.49 (s, 9H), 1.08 and 0.90 (d × 2, J ) 6.9 Hz, 3H × 2);
1
758, 573, 531 cm-1; H NMR (200 MHz, CDCl3) δ 7.63-7.43
(m, 3H), 7.22-7.03 (m, 2H), 6.97 (d, J ) 7.6 Hz, 1H), 5.40 (dd,
J ) 8.2, 5.2 Hz, 1H), 4.61 (s, 2H), 4.07 (br s, 2H), 2.67 (m,
3H), 2.64-2.38 (m, 1H), 1.07 (d, J ) 6.6 Hz, 3H), 0.90 (d, J )
6.6 Hz, 3H); optical rotation [R]25D -19.7 (c 0.5, CH3CN). Anal.
(C20H21FN6O4‚0.5H2O) C, H, N.
optical rotation [R]30 -23.4 (c 0.4, CH3CN). Anal. (C23H27
-
D
FN6O4) C, H, N.
N-[(1S)-1-(Meth yleth yl)-2-oxo-2-(5-p h en yl-1,3,4-oxa d ia -
zol-2-yl)eth yl]-2-[5-a m in o-2-(4-flu or op h en yl)-6-oxoh yd r o-
p yr im id in yl]a ceta m id e (11f(F )). Derived from 13(F ) and
8f which was prepared from 5f: yellow amorphous powder;
TLC Rf ) 0.29, EtOAc; MS (APCI, pos. 40 V) m/z ) 491 (M +
H)+; IR (KBr) 3346, 3062, 2967, 1664, 1610, 1543, 1510, 1481,
1451, 1397, 1303, 1228, 1204, 1161, 1097, 1028, 982, 902, 845,
818, 787, 715, 691, 531, 492, 423, 406 cm-1; 1H NMR (200 MHz,
CDCl3) δ 8.18 (dd, J ) 7.9, 1.7 Hz, 2H), 7.73 (d, J ) 7.6 Hz,
1H), 7.66-7.48 (m, 5H), 7.47 (s, 1H), 7.11 (t, J ) 8.5 Hz, 2H),
5.47 (dd, J ) 7.8, 5.6 Hz, 1H), 4.64 (s, 2H), 4.14 (br s, 2H),
2.54 (m, 1H), 1.10 and 0.96 (d × 2, J ) 6.7 Hz, 3H × 2); optical
rotation [R]30D -64.1 (c 0.3, CH3CN). Anal. (C25H23FN6O4‚0.3CH3-
CO2C2H5) C, H, N.
N-{(1S)-1-(Met h ylet h yl)-2-[5-(m et h ylet h yl)-1,3,4-oxa -
d ia zol-2-yl]-2-oxoeth yl}-2-[5-a m in o-2-(4-flu or op h en yl)-6-
oxoh yd r op yr im id in yl]a ceta m id e (11b(F )). Derived from
13(F ) and 8b which was prepared from 4b: yellow amorphous
solid; TLC Rf ) 0.16, EtOAc; MS (APCI, pos. 40 V) m/z ) 457
(M + H)+, 377; IR (KBr) 3461, 3336, 2974, 2939, 2879, 1718,
1664, 1610, 1543, 1510, 1468, 1438, 1408, 1374, 1310, 1227,
1203, 1161, 1098, 1038, 1017, 981, 929, 900, 846, 818, 788,
1
753, 704, 532 cm-1; H NMR (200 MHz, CDCl3) δ 7.60-7.48
(m, 2H), 7.49 (s, 1H), 7.19-7.06 (m, 2H), 6.90 (br d, J ) 8.0
Hz, 1H), 5.42 (dd, J ) 8.0, 5.0 Hz, 1H), 4.59 (s, 2H), 4.06 (br
s, 2H), 3.29 (septet, J ) 7.2 Hz, 1H), 2.52 (m, 1H), 1.45 (d, J
) 7.2 Hz, 6H), 1.08 and 0.89 (d × 2, J ) 7.0 Hz, 3H × 2);
N-{(1S)-2-[5-(4-Meth oxyp h en yl)-1,3,4-oxa d ia zol-2-yl]-1-
(m eth yleth yl)-2-oxoeth yl}-2-[5-a m in o-2-(4-flu or op h en yl)-
6-oxoh yd r op yr im id in yl]a ceta m id e (11g(F )). Derived from
13(F ) and 8g which was prepared from 4g: pale yellow
powder; TLC Rf ) 0.49, EtOAc; MS (APCI, pos. 40 V) m/z )
521 (M + H)+, 246, 218, 206; IR (KBr) 3463, 3369, 3071, 2968,
1713, 1667, 1612, 1510, 1490, 1428, 1310, 1264, 1230, 1176,
optical rotation [R]30 -20.0 (c 0.3, CH3CN). Anal. (C22H25
-
D
FN6O4‚0.2H2O) C, H, N.
N-[(1S)-2-(5-Bu t yl-1,3,4-oxa d ia zol-2-yl)-1-(m et h ylet h -
yl)-2-oxoeth yl]-2-[5-am in o-2-(4-flu or oph en yl)-6-oxoh ydr o-
p yr im id in yl]a ceta m id e (11c(F )). Derived from 13(F ) and
8c which was prepared from 4c: yellow amorphous solid; TLC
Rf ) 0.41, EtOAc; MS (APCI, pos. 40 V) m/z ) 471 (M + H)+;
IR (KBr) 3338, 2965, 2876, 1720, 1664, 1610, 1548, 1510, 1468,
1437, 1407, 1302, 1227, 1161, 1098, 1024, 981, 901, 846, 818,
1
1099, 1026, 842, 787, 750, 707, 621, 533 cm-1; H NMR (200
MHz, CDCl3) δ 8.12 (m, 2H), 7.65-7.42 (m, 3H), 7.20-6.90
(m, 5H), 5.47 (dd, J ) 8.4, 5.2 Hz, 1H), 4.62 (s, 2H), 4.06 (br s,
2H), 3.91 (s, 3H), 2.71-2.41 (m, 1H), 1.10 (d, J ) 6.7 Hz, 3H),
1
789, 733, 533 cm-1; H NMR (200 MHz, CDCl3) δ 7.59-7.46
(m, 2H), 7.48 (s, 1H), 7.18-7.04 (m, 2H), 6.93 (br d, J ) 8.0
Hz, 1H, NH), 5.42 (dd, J ) 8.0, 5.2 Hz, 1H), 4.60 (s, 2H), 4.06
(br s, 2H), 2.95 (t, J ) 7.7 Hz, 2H), 2.51 (m, 1H), 1.83 (m, 2H),
1.44 (m, 2H), 1.07 and 0.89 (d × 2, J ) 7.0 Hz, 3H × 2), 0.96
0.92 (d, J ) 6.7 Hz, 3H); optical rotation [R]25 -63.9 (c 0.5,
D
CH3CN). Anal. (C26H25FN6O5) C, H, N.
N -{(1S)-1-(Me t h yle t h yl)-2-oxo-2-[5-(3-p yr id yl)-1,3,4-
oxa d ia zol-2-yl]et h yl}-2-[5-a m in o-2-(4-flu or op h en yl)-6-
oxoh yd r op yr im id in yl]a ceta m id e (11h (F )). Derived from
13(F ) and 8h which was prepared from 5h : yellow amorphous
powder; TLC Rf ) 0.37, CHCl3/MeOH (10/1); MS (APCI, pos.
40 V) m/z ) 492 (M + H)+, 377, 148; IR (KBr) 3450, 3346,
3060, 2963, 2927, 1719, 1663, 1640, 1608, 1538, 1509, 1482,
1465, 1439, 1416, 1379, 1306, 1227, 1203, 1161, 1107, 1026,
982, 928, 901, 842, 817, 790, 753, 734, 704, 632, 574, 531, 424
(t, J ) 7.1 Hz, 3H); optical rotation [R]29 -20.0 (c 0.8, CH3-
D
CN). Anal. (C23H27FN6O4‚0.2H2O) C, H, N.
N-{(1S)-2-[5-(1-Met h ylcyclop r op yl)-1,3,4-oxa d ia zol-2-
y l]-1-(m e t h y le t h y l)-2-o x o e t h y l}-2-(5-a m in o -6-o x o -2-
ph en ylh ydr opyr im idin yl)acetam ide (11d(H)). Derived from
13(H) and 8d which was prepared from 4d : yellow amorphous
solid; TLC Rf ) 0.37, EtOAc; MS (APCI, neg. 40 V) m/z ) 449
(M - H)-, 357, 313, 186, 123; IR (KBr) 3455, 3336, 2968, 2935,
1715, 1664, 1612, 1548, 1438, 1412, 1386, 1315, 1258, 1204,
1
cm-1; H NMR (200 MHz, CDCl3) δ 9.41 (dd, J ) 2.3, 0.7 Hz,
1H), 8.86 (dd, J ) 4.9, 1.7 Hz, 1H), 8.46 (dt, 1H, J ) 8.0, 2.0

Orally Active Nonpeptidic Inhibitors of HNE
J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 8 1277
Hz, 1H), 7.62-7.48 (m, 3H), 7.49 (s, 1H), 7.13 (t, J ) 8.6 Hz,
2H), 6.99 (d, J ) 7.6 Hz, 1H), 5.47 (dd, J ) 7.8, 5.0 Hz, 1H),
4.62 (s, 2H), 4.06 (br s, 2H), 2.56 (m, 1H), 1.12 and 0.95 (d ×
toluene to give 6k (10.06 g, 65%) as a slightly brown liquid:
TLC Rf ) 0.58, CHCl3/MeOH (10/1); MS (APCI, pos. 40 V) m/z
1
) 189 (M + H)+; H NMR (200 MHz, CDCl3) δ 8.30 (s, 1H),
2, J ) 6.9 Hz, 3H × 2); optical rotation [R]30 -34.6 (c 0.3,
7.40-7.19 (m, 5H), 1.85 (s, 6H).
D
CH3CN). Anal. (C24H22FN7O4‚0.2CH3CO2C2H5) C, H, N.
ter t-Bu t yl N-{(1S)-2-Hyd r oxy-1-(m et h ylet h yl)-2-[5-(1-
m e t h yl-1-p h e n yle t h yl)-1,3,4-oxa d ia zol-2-yl]e t h yl}ca r -
ba m a te (7k ). To a stirred solution of the oxadiazole 6k (1.69
g, 9.00 mmol) in THF (40 mL) was added dropwise n-BuLi
(9.00 mmol) in n-hexane under Ar at -70 °C. After 1.5 h,
MgBr2‚OEt2 (2.56 g, 9.90 mmol) was added, and then the
reaction mixture was allowed to warm to -45 °C over 30 min.
The resulting white slurry was stirred at -45 °C for 1 h, and
treated with tert-butyl N-[(1S)-1-(methylethyl)-2-oxoethyl]car-
bamate (Boc-L-valinal) (12)19 (603 mg, 3.00 mmol) in THF (13
mL). The reaction temperature was allowed to rise to -20 °C.
The reaction mixture was stirred for another 1.5 h, then
quenched with saturated NH4Cl, and extracted with EtOAc.
The organic layer was washed with water (×2) and then brine,
dried over anhydrous Na2SO4, and concentrated in vacuo. The
crude product was purified twice by silica gel column chro-
matography [FL60D, EtOAc/n-hexane (1/10)] to give the Boc
alcohol 7k (922 mg, 2.37 mmol, ca. 79%) as a pale yellow
amorphous solid: TLC (HPTLC) Rf ) 0.58 and 0.55, EtOAc/
n-hexane (1/1); MS (APCI, pos. 40 V) m/z ) 390 (M + H)+,
334, 189; 1H NMR (200 MHz, CDCl3) δ 7.40-7.18 (m, 5H),
5.05-4.78 (m, 2H), 4.08-3.75 and 3.63-3.47 (m × 2, 2H),
2.05-1.68 (m, 7H), 1.41 and 1.35 (s × 2, 9H), 1.06-0.85 (m,
6H).
(2S)-2-Am in o-3-m eth yl-1-[5-(1-m eth yl-1-p h en yleth yl)-
1,3,4-oxadiazol-2-yl]bu tan -1-ol Hydr och lor ide (8k). A mix-
ture of the Boc alcohol 7k (393 mg, 1.01 mmol) and 4 N HCl
in dioxane (30 mL) was stirred at room temperature for 1.5 h.
The reaction mixture was concentrated in vacuo. The residue
was dried by azeotropic removal of water with toluene to afford
8k quantitatively. The product was used for the next reaction
without further purification: TLC Rf ) 0.23, MeOH/CHCl3
(1/10); MS (APCI, pos. 40 V) m/z ) 290 (M + H)+, 219, 189; 1H
NMR (200 MHz, CDCl3) δ 8.50-8.00 (m, 2H), 7.35-6.80 (m,
7H), 5.42-5.30 (m, 1H), 3.85-3.60 (m, 2H), 2.00-1.50 (m, 7H),
1.13-0.80 (m, 6H).
N-{(1S)-2-H yd r oxy-1-(m et h ylet h yl)-2-[5-(1-m et h yl-1-
p h en ylet h yl)-1,3,4-oxa d ia zol-2-yl]et h yl}-2-{2-(4-flu or o-
p h e n yl)-6-oxo-5-[(p h e n ylm e t h oxy)ca r b a m id o]h yd r o-
p yr im id in yl}a ceta m id e (9k (F )). To a stirred mixture of the
carboxylic acid 13(F ) (333 mg, 0.84 mmol), the amino alcohol
8k (ca. 1.01 mmol) and HOBt‚H2O (155 mg, 1.01 mmol) in
DMF (2.5 mL), were added EDC‚HCl (194 mg, 1.01 mmol) and
then N-methylmorpholine (0.11 mL, 1.01 mmol) under Ar at
0 °C. After 15 min, the reaction mixture was stirred at room
temperature for 12 h, and poured into saturated NaHCO3 and
extracted with EtOAc. The organic layer was washed with
water, and dried over anhydrous MgSO4. Evaporation followed
by purification by silica gel column chromatography [FL60D,
MeOH/CHCl3 (0/100 f 1/10)] afforded Cbz alcohol 9k (F ) (551
mg, 98%) as a pale yellow amorphous solid: TLC Rf ) 0.46
and 0.42, MeOH/CHCl3 (1/10); MS (APCI, pos. 40 V) m/z )
669 (M + H)+; 1H NMR (200 MHz, CDCl3) δ 8.78 and 8.71 (m
× 2, 1H), 7.70-6.70 (m, 16H), 5.20 and 5.18 (s × 2, 2H), 5.05
and 4.98 (m × 2, 1H), 4.60-3.87 (m, 4H), 2.00-1.53 (m, 7H),
1.08-0.80 (m, 6H).
N-{(1S)-1-(Meth yleth yl)-2-[5-(1-m eth yl-1-p h en yleth yl)-
1,3,4-oxa d ia zol-2-yl]-2-oxoeth yl}-2-{2-(4-flu or op h en yl)-6-
oxo-5-[(p h en ylm eth oxy)ca r ba m id o]h yd r op yr im id in yl}-
a cet a m id e (10k (F )). To a suspension of Dess-Martin
periodinane (ca. 77%, 491 mg, 0.89 mmol) in CH2Cl2 (5 mL)
was added dropwise a solution of Cbz alcohol 9k (F ) (542 mg,
0.81 mmol) in CH2Cl2 (8 mL) under Ar at room temperature.
After 2 h, the reaction mixture was poured into water and
extracted with EtOAc. The organic layer was washed with
water and then brine, dried over anhydrous Na2SO4, and
concentrated in vacuo. Purification of the residue by silica gel
column chromatography [FL60D, EtOAc/n-hexane, (1/4 f 1/1)]
gave Cbz ketone 10k (F ) (490 mg, 91%) as a pale yellow
amorphous solid: TLC Rf ) 0.57, EtOAc/n-hexane (1/1); MS
N-[(1S)-1-(Meth yleth yl)-2-oxo-2-(5-ben zyl-1,3,4-oxa d ia -
zol-2-yl)eth yl]-2-[5-a m in o-2-(4-flu or op h en yl)-6-oxoh yd r o-
p yr im id in yl]a ceta m id e (11i(F )). Derived from 13(F ) and
8i which was prepared from 4i: lemon yellow solid; TLC Rf )
0.50, etc; MS (APCI, pos. 40 V) m/z ) 505 (M + H)+, 377, 161;
IR (KBr) 3465, 3367, 3075, 2969, 1716, 1670, 1611, 1544, 1510,
1457, 1436, 1405, 1312, 1280, 1229, 1202, 1161, 1097, 1024,
981, 899, 845, 817, 787, 731, 697, 534, 472 cm-1; 1H NMR (200
MHz, CDCl3) δ 7.56-7.48 (m, 2H), 7.48 (s, 1H), 7.40-7.30 (m,
5H), 7.10 (t, J ) 8.5 Hz, 2H), 6.94 (br d, J ) 8.6 Hz, 1H), 5.39
(dd, J ) 8.6, 5.2 Hz, 1H), 4.58 (s, 2H), 4.29 (s, 2H), 4.05 (br s,
2H), 2.49 (m, 1H), 1.06 and 0.87 (d × 2, J ) 6.8 Hz, 3H × 2);
optical rotation [R]27 -25.6 (c 0.6, CH3CN). Anal. (C26H25
-
D
FN6O4) C, H, N.
N-{(1S)-1-(Met h ylet h yl)-2-[5-((3-m et h ylp h en yl)m et h -
yl)-1,3,4-oxadiazol-2-yl]-2-oxoeth yl}-2-[5-am in o-2-(4-flu or o-
p h en yl)-6-oxoh yd r op yr im id in yl]a ceta m id e (11j(F )). De-
rived from 13(F ) and 8j which was prepared from 4j: white
powder; TLC Rf ) 0.42, EtOAc; MS (APCI, pos. 40 V) m/z )
519 (M + H)+, 246, 218, 206; IR (KBr) 3459, 3365, 3286, 2967,
1707, 1665, 1611, 1538, 1510, 1438, 1309, 1226, 1204, 1162,
1097, 1037, 980, 891, 846, 817, 787, 755, 695, 532 cm-1 1H
;
NMR (200 MHz, DMSO-d6) δ 8.69 (d, J ) 7.0 Hz, 1H,), 7.49-
7.34 (m, 2H), 7.34-7.06 (m, 7H), 5.15 (br s, 2H), 5.11-4.99
(m, 1H), 4.52 (s, 2H), 4.36 (s, 2H), 2.35-2.11 (m, 1H), 2.29 (s,
3H), 0.89 (d, J ) 6.8 Hz, 3H), 0.82 (d, J ) 6.8 Hz, 3H); optical
rotation [R]26 -23.7 (c 1.0, CH3CN). Anal. (C27H27FN6O4) C,
D
H, N.
Meth yl 2-Meth yl-2-p h en ylp r op ion a te (4k ). To a stirred
solution of phenylacetic acid (14k ) (15.0 g, 0.110 mol) in
methanol (280 mL) was added dropwise chlorotrimethylsilane
(31.0 mL, 0.24 mol). The resulting solution was stirred at room
temperature for 5 h, and the solvent was removed by evapora-
tion. The residue was dried by azeotropic removal of water
with benzene and diluted with THF (100 mL). The solution
was added dropwise to a stirred suspension of sodium hydride
(60% in oil, 13.0 g, 0.33 mol) in THF (400 mL) under Ar. The
resulting suspension was stirred for 30 min, and methyl iodide
(16.5 mL, 0.26 mol) was added dropwise. The reaction mixture
was stirred at room temperature overnight. To the reaction
mixture was added Florisil (12 g), and the solid was removed
by filtration through a pad of Celite. The filtrate was concen-
trated under reduced pressure, and the residue was partitioned
between EtOAc and water. The aqueous layer was extracted
twice with EtOAc, and the combined organic layers were
washed with brine. After drying over anhydrous MgSO4, the
solvent was removed by evaporation. The residue was purified
by silica gel column chromatography [Merck 7734, n-hexane/
EtOAc (10/1)] to give 4k (14.9 g, 76%) as a yellowish liquid:
TLC Rf ) 0.33, n-hexane/EtOAc (10/1); 1H NMR (200 MHz,
CDCl3) δ 7.38-7.18 (m, 5H), 3.65 (s, 3H), 1.58 (s, 6H).
2-Meth yl-2-p h en ylp r op ion e Hyd r a zid e (5k ). A mixture
of the ester 4k (14.9 g, 83.6 mmol) and hydrazine hydrate (41
mL, 0.85 mol) was heated under reflux with stirring for 6.5 h.
The reaction mixture was cooled to room temperature, and
concentrated. The hydrazine was removed by azeotropic distil-
lation with toluene. The residue was purified by column
chromatography [Merck 7734, CHCl3/MeOH (10/1)] to give 5k
(14.7 g, 99%) as a yellowish gum: TLC Rf ) 0.50, CHCl3/MeOH
1
(10/1); H NMR (200 MHz, CDCl3) δ 7.41-7.22 (m, 5H), 3.92
(br s, 3H), 1.59 (s, 6H).
2-(1-Meth yl-1-ph en yleth yl)-1,3,4-oxadiazole (6k). A mix-
ture of the hydrazide 5k (14.7 g, 82.5 mmol) and ethyl
orthoformate (90 mL, 0.54 mol) was heated under reflux with
stirring for 10 h. The reaction mixture was cooled to room
temperature, and concentrated. The ethyl orthoformate was
removed by azeotropic distillation with toluene. The residue
was purified by silica gel column chromatography (Merck 7734,
n-hexane/EtOAc), followed by azeotropic removal of water with

1278 J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 8
Ohmoto et al.
(APCI, pos. 40 V) m/z 667 (M + H)+, 344, 173, 127; IR (KBr)
3386, 2973, 1723, 1663, 1608, 1526, 1504, 1398, 1368, 1301,
1216, 1191, 1162, 1093, 1016, 924, 847, 747, 699 cm-1; 1H NMR
(200 MHz, CDCl3) δ 8.75 (br s, 1H), 7.62-7.47 (m, 3H), 7.43-
7.20 (m, 10H), 7.11 (t, J ) 8.5 Hz, 2H), 6.75 (d, J ) 8.0 Hz,
1H), 5.43 (dd, J ) 8.0, 5.0 Hz, 1H), 5.22 (s, 2H), 4.58 (s, 2H),
2.49 (m, 1H), 1.88 (s, 6H), 1.04 and 0.84 (d × 2, J ) 7.0 Hz,
gel column chromatography [FL60D, n-hexane/EtOAc (1/1 f
1/2 f 0/1)] to give a yellow oil which was triturated with ether
to afford 11m (F ). The mother liquor was purified by silica gel
column chromatography [FL60D, CHCl3/MeOH (1/0 f 100/
1)] to give an additional 11m (F ) as a pale yellow amorphous
solid; total 40 mg (0.070 mmol, 75%): TLC Rf ) 0.39, AcOEt;
MS (EI, pos.) m/z ) 576 (M+)+; IR (KBr) 3346, 2973, 1664,
1610, 1533, 1509, 1436, 1243, 1161, 1112, 1039, 931, 897, 846,
3H × 2); optical rotation [R]24 -20.3, (c 1.0, MeCN).
D
1
817, 788, 532 cm-1; H NMR (200 MHz, CDCl3) δ 7.58-7.46
N-{(1S)-1-(Met h ylet h yl)-2-[5-(1-m et h yl-1-p h en ylet h -
yl)-1,3,4-oxadiazol-2-yl]-2-oxoeth yl}-2-[5-am in o-2-(4-flu or o-
p h en yl)-6-oxoh yd r op yr im id in yl]a ceta m id e (11k (F )). To
a stirred solution of 10k (F ) (200 mg, 0.30 mmol) and anisole
(0.20 mL, 1.80 mmol) in CH2Cl2 (6 mL) was added dropwise a
solution of aluminum chloride (240 mg, 1.80 mmol) in CH3-
NO2 (3 mL) under Ar at 0 °C. The reaction mixture was stirred
at room temperature for 1.5 h, then quenched with crushed
ice, and poured into water and extracted with EtOAc. The
organic layer was washed with water and then brine, dried
over anhydrous MgSO4, and concentrated in vacuo. Purifica-
tion of the residue by silica gel column chromatography
[FL60D, EtOAc/n-hexane (2/1)] gave 11k (F ) (153 mg, 97%) as
a pale yellow amorphous powder: TLC Rf ) 0.49, EtOAc; MS
(FAB, pos.) m/z ) 533 (M + H)+, 246, 218, 206, 119; IR (KBr)
3448, 3348, 2972, 1719, 1664, 1610, 1533, 1510, 1438, 1227,
(m, 2H), 7.48 (s, 1H), 7.11 (t, J ) 8.6 Hz, 2H), 6.87 (br d, J )
8.4 Hz, 1H), 6.81 (d, J ) 1.0 Hz, 1H), 6.76 (d, J ) 1.2 Hz, 2H),
5.95 (s, 2H), 5.43 (dd, J ) 8.3, 4.7 Hz, 1H), 4.62 and 4.53 (d ×
2, J ) 15.0 Hz, 1H × 2), 4.05 (br s, 2H), 2.51 (m, 1H), 1.84 (s,
6H), 1.07 and 0.87 (d × 2, J ) 6.8 Hz, 3H × 2); optical rotation
[R]30 -21.3 (c 0.3, CH3CN). Anal. (C29H29FN6O6‚0.5H2O) C,
D
H, N.
N-(2,2-Dim eth oxyeth yl)ben zam idin e (16(H)). To a stirred
solution of methyl benzimidate hydrochloride (15(H)) (20.0 g,
116.6 mmol) in MeOH (100 mL) was added dropwise aminoac-
etaldehyde dimethylacetal (13.96 mL, 128.3 mmol) under Ar
at 0 °C. The reaction mixture was stirred at 4 °C for 22 h,
then concentrated in vacuo. The resulting white solid was
treated with 1 N NaOH, and extracted with CH2Cl2. The
organic layer was washed with 1 N NaOH (×6), dried over
anhydrous MgSO4, concentrated in vacuo, and dried by azeo-
tropic removal of water with toluene. The resulting pale yellow
syrup (amidine 16(H): 23.5 g, ca. 113.0 mmol) was used for
the next reaction without further purification: TLC Rf ) 0.22,
MeOH/CHCl3 (1/10); MS (APCI, pos. 40 V) m/z ) 209 (M +
H)+; 1H NMR (200 MHz, CDCl3) δ 7.59-7.38 (m, 5H), 4.62 (t,
J ) 5.6 Hz, 1H), 3.54 (d, J ) 5.6 Hz, 2H), 3.44 (s, 6H).
1161, 1033, 1017, 846, 700, 532 cm-1 1H NMR (200 MHz,
;
CDCl3) δ 7.62-7.42 (m, 3H), 7.42-7.18 (m, 5H), 7.18-7.03 (m,
2H), 7.00 (d, J ) 8.3 Hz, 1H), 5.43 (dd, J ) 8.3 and 5.0 Hz,
1H), 4.60 (s, 2H), 4.07 (br s, 2H), 2.63-2.35 (m, 1H), 1.88 (s,
6H), 1.05 (d, J ) 6.8 Hz, 3H), 0.85 (d, J ) 6.8 Hz, 3H); optical
rotation [R]25D -25.2, (c 0.5, MeCN). Anal. (C28H29FN6O4‚H2O)
C, H, N.
P r ep a r a tion of 11k (H) a n d 11l,m (F ). The following
compounds were prepared, using essentially the same proce-
dures as described for the preparation of 11k (F ).
3-(2,2-Dim eth oxyeth yl)-2-p h en yl-3-h yd r op yr im id in -4-
on e (17(H)). A mixture of the crude amidine 16(H) (15.5 g,
ca. 74.4 mmol) and ethyl 3-ethoxyacrylate (11.3 mL, 78.1
mmol) was heated at 110-120 °C for 42 h, then cooled to room
temperature. The reaction mixture was poured into saturated
NH4Cl and extracted with EtOAc. The organic layer was
washed with water and then brine, dried over anhydrous Na2-
SO4, and concentrated in vacuo. Purification of the crude
product by silica gel column chromatography [Merck 7734,
EtOAc/n-hexane (1/1)] gave the acetal 17(H) (11.7 g, 58% in 2
steps) as a pale yellow solid: TLC Rf ) 0.30, EtOAc/n-hexane
N-{(1S)-1-(Met h ylet h yl)-2-[5-(1-m et h yl-1-p h en ylet h -
yl)-1,3,4-oxa d ia zol-2-yl]-2-oxoeth yl}-2-(5-a m in o-6-oxo-2-
ph en ylh ydr opyr im idin yl)acetam ide (11k(H)). Derived from
13(H) and 8k which was prepared from 14k : white powder;
TLC Rf ) 0.51, EtOAc; MS (FAB, pos. glycerol + m-NBA) m/z
) 515 (M + H)+, 228, 200, 188, 119, 91; IR (KBr) 3463, 3319,
3060, 2977, 1695, 1664, 1610, 1531, 1438, 1371, 1301, 1247,
1204, 1032, 977, 897, 774, 700 cm-1 1H NMR (200 MHz,
;
1
(2/1); H NMR (200 MHz, CDCl3) δ 7.96 (d, J ) 6.6 Hz, 1H),
CDCl3) δ 7.58-7.18 (m, 11H), 6.79 (d, J ) 8.4 Hz, 1H), 5.44
(dd, J ) 8.4, 5.0 Hz, 1H), 4.65 (d, J ) 15.4 Hz, 1H), 4.55 (d, J
) 15.4 Hz, 1H), 4.03 (br s, 2H), 2.62-2.36 (m, 1H), 1.89 (s,
6H), 1.06 (d, J ) 6.8 Hz, 3H), 0.85 (d, J ) 7.0 Hz, 3H); optical
rotation [R]25D -27.2 (c 0.4, CH3CN). Anal. (C28H30N6O4) C, H,
N.
7.63-7.40 (m, 5H), 6.45 (d, J ) 6.6 Hz, 1H), 4.78 (t, J ) 5.4
Hz, 1H), 4.11 (d, J ) 5.4 Hz, 2H), 3.29 (s, 6H).
2-(6-Oxo-2-p h en ylh yd r op yr im id in yl)eth a n a l (18(H)). A
mixture of the acetal 17(H) (5.00 g, 19.2 mmol) in THF (35
mL) and 1 N HCl (21.7 mL) was refluxed overnight. The
reaction mixture was neutralized with NaHCO3 (solid), and
extracted with EtOAc. The organic layer was washed with
water and with brine, dried over anhydrous MgSO4, and
concentrated in vacuo. The resulting brown oil (aldehyde 18-
(H): ca. 19.2 mmol) was used for the next reaction without
further purification: TLC Rf ) 0.42, EtOAc; MS (APCI, pos.
40 V) m/z ) 215 (M + H)+, 200, 168; 1H NMR (200 MHz,
CDCl3) δ 9.61 (s, 1H), 8.02 (d, J ) 6.6 Hz, 1H), 9.63-7.34 (m,
5H), 6.52 (d, J ) 6.6 Hz, 1H), 4.75 (s, 2H).
N -{(1S )-1-(Me t h yle t h yl)-2-[5-(1-m e t h yl-1-(3-m e t h yl-
phenyl)ethyl)-1,3,4-oxadiazol-2-yl]-2-oxoethyl}-2-[5-amino-2-
(4-flu or op h en yl)-6-oxoh yd r op yr im id in yl]a ceta m id e (11l-
(F )). Derived from 13(F ) and 8l which was prepared from
14l: pale yellow amorphous powder: TLC Rf ) 0.51, AcOEt;
MS (FAB, pos. glycerol + m-NBA) m/z ) 547 (M + H)+, 533,
246, 218, 206; IR (KBr) 3456, 3335, 2970, 2933, 1933, 1718,
1664, 1610, 1532, 1510, 1438, 1227, 1201, 1161, 1040, 1016,
1
845, 788, 103, 530 cm-1; H NMR (200 MHz, CDCl3) δ 7.62-
7.39 (m, 3H), 7.31-6.92 (m, 7H), 5.44 (d, J ) 8.6, 5.0 Hz, 1H),
4.60 (s, 2H), 4.07 (br s, 2H), 2.65-2.32 (m, 1H), 2.33 (s, 3H),
1.86 (s, 6H), 1.04 (d, J ) 6.8 Hz, 3H), 0.84 (d, J ) 6.8 Hz, 3H);
2-(6-Oxo-2-p h en ylh yd r op yr im id in yl)a cetic Acid (19-
(H)). To a stirred solution of the aldehyde 18(H) (ca. 19.2
mmol.) in tert-butyl alcohol (31 mL) and water (7.8 mL) was
added successively 2-methyl-2-butene (9.17 mL, 86.5 mmol),
a solution of NaH2PO4 (2.77 g, 23.1 mmol) in water (7.8 mL)
and a solution of NaClO2 (80%, 7.61 g, 67.3 mmol) in water
(17.8 mL) at 0 °C. After being stirred at room temperature for
4 h, the reaction mixture was evaporated under reduced
pressure, and the resulting aqueous layer was washed with
CH2Cl2 (×5), then acidified with 1 N HCl (pH 3). The resulting
white precipitates were collected by filtration, and washed with
ether. Drying under reduced pressure gave the carboxylic acid
19(H) (2.57 g, 58% in 2 steps) as a white powder: TLC Rf )
0.18, CHCl3/MeOH/AcOH (18/1/1); MS (APCI, pos. 40 V) m/z
) 231 (M + H)+, 202, 185, 168, 138, 122; 1H NMR (200 MHz,
DMSO-d6) δ 8.03 (d, J ) 6.6 Hz, 1H), 7.56-7.40 (m, 5H), 6.49
(d, J ) 6.6 Hz, 1H), 4.46 (s, 2H).
optical rotation [R]25 -19.3 (c 0.5, CH3CN). Anal. (C29H31
-
D
FN6O4‚0.4H2O) C, H, N.
N -{2-[5-(1-(2H -Be n zo[3,4-d ]1,3-d ioxola n -5-yl)m e t h -
yleth yl)-1,3,4-oxa d ia zol-2-yl]-(1S)-1-(m eth yleth yl)-2-oxo-
eth yl}-2-[5-a m in o-2-(4-flu or op h en yl)-6-oxoh yd r op yr im i-
d in yl]a ceta m id e (11m (F )). With respect to the final step for
the synthesis of 11m (F ), deprotection was carried out accord-
ing to the procedure described as follows: A solution of 10m -
(F ) (66.0 mg, 0.093 mmol) in 30% HBr/AcOH (2.5 mL) was
stirred at room temperature for 45 min. The reaction was
quenched with water, and extracted three times with EtOAc.
The combined organic layers were washed with water (×2) and
then brine, and dried over anhydrous MgSO4. The organic
solution was diluted with n-hexane, and then purified by silica

Orally Active Nonpeptidic Inhibitors of HNE
J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 8 1279
N -[(1S )-2-(5-t er t -B u t y l-1,3,4-o x a d ia zo l-2-y l)-2-h y -
d r oxy-1-(m e t h yle t h yl)e t h yl]-2-(6-oxo-2-p h e n ylh yd r o-
p yr im id in yl)a ceta m id e (20e(H)). To a stirred solution of the
carboxylic acid 19(H) (262 mg, 1.14 mmol), the amino alcohol
8e (364 mg, 1.38 mmol) and HOBt‚H2O (228 mg, 1.49 mmol)
in DMF (15 mL) were added EDC‚HCl (241 mg, 1.26 mmol)
and then N-methylmorpholine (0.15 mL, 1.38 mmol) under Ar
at 0 °C. The reaction mixture was stirred at room temperature
for 3.5 h, then poured into water and extracted with EtOAc.
The organic layer was washed with saturated NH4Cl, satu-
rated NaHCO3, water and brine, dried over anhydrous MgSO4,
and concentrated in vacuo. The crude product was purified by
silica gel column chromatography [FL60D, MeOH/CHCl3 (0/
100 f 1/9)] to give the alcohol 20e(H) (less polar isomer: 64
mg, more polar isomer: 242 mg; total: 306 mg, 61%) as a pale
yellow amorphous solid. Less polar isomer: TLC (HPTLC) Rf
) 0.34, CHCl3/MeOH (9/1); MS (APCI, pos. 40 V) m/z ) 440
(M + H)+, 314, 176, 127; 1H NMR (200 MHz, CDCl3) δ 8.05 (d,
J ) 6.6 Hz, 1H), 7.76-7.61 (m, 2H), 7.59-7.42 (m, 3H), 7.07
(d, J ) 10.4 Hz, 1H), 6.47 (d, J ) 6.6 Hz, 1H), 5.10-4.94 (m,
1H), 4.61 and 4.45 (d × 2, J ) 15.0 Hz, 1H × 2), 4.32 (dt, J )
4.0, 9.4 Hz, 1H), 4.22-4.00 (m, 1H), 1.89-1.60 (m, 1H), 1.43
(s, 9H), 0.95 and 0.93 (d × 2, J ) 6.6 Hz, 3H × 2). More polar
isomer: TLC (HPTLC) Rf ) 0.27, CHCl3/MeOH (9/1); MS
(APCI, pos. 40 V) m/z ) 440 (M + H)+, 314, 176, 127; 1H NMR
(200 MHz, CDCl3) δ 7.98 (d, J ) 6.6 Hz, 1H), 7.62-7.41 (m,
5H), 6.63 (d, J ) 9.2 Hz, 1H), 6.43 (d, J ) 6.6 Hz, 1H), 5.17-
5.06 (m, 1H), 4.48 and 4.37 (d × 2, J ) 15.4 Hz, 1H × 2), 4.37-
4.23 (m, 1H), 4.05 (dt, J ) 2.2, 8.6 Hz, 1H), 2.10-1.91 (m, 1H),
1.39 (s, 9H), 1.09 and 1.01 (d × 2, J ) 6.6 Hz, 3H × 2).
TLC Rf ) 0.38, EtOAc; MS (APCI, pos. 40 V) m/z ) 454 (M +
H)+, 362, 125; IR (KBr) 3465, 3267, 3072, 2971, 1716, 1673,
1606, 1550, 1505, 1423, 1388, 1230, 1193, 1163, 1101, 1048,
978, 841, 805, 778, 738, 570, 459 cm-1 1H NMR (200 MHz,
;
CDCl3) δ 8.00 (d, J ) 6.6 Hz, 1H), 7.61 (dd, J ) 8.8, 5.2 Hz,
2H), 7.15 (t, J ) 8.8 Hz, 2H), 6.90 (br d, J ) 8.2 Hz, 1H), 6.51
(d, J ) 6.6 Hz, 1H), 5.39 (dd, J ) 8.2, 5.1 Hz, 1H), 4.58 (s,
2H), 2.49 (m, 1H), 1.61 (s, 3H), 1.50-1.41 (m, 2H), 1.13-1.04
(m, 2H), 1.07 and 0.89 (d × 2, J ) 6.8 Hz, 3H × 2).; optical
rotation [R]24 -34.4 (c 0.7, CH3CN). Anal. (C23H24FN5O4) C,
D
H, N.
N-[(1S)-2-(5-ter t-Bu t yl-1,3,4-oxa d ia zol-2-yl)-1-(m et h -
ylet h yl)-2-oxoet h yl]-2-[2-(4-flu or op h en yl)-6-oxoh yd r o-
p yr im id in yl]a ceta m id e (21e(F )). Derived from 8e and 19-
(F ) which was prepared from 15(F ): ivory amorphous solid;
TLC Rf ) 0.42, EtOAc; MS (APCI, pos. 40 V) m/z ) 456 (M +
H)+, 362; IR (KBr) 3444, 3063, 2974, 2937, 2877, 1685, 1606,
1531, 1505, 1466, 1426, 1408, 1371, 1228, 1192, 1163, 1100,
1
1048, 1017, 978, 902, 847, 807, 779, 761, 569 cm-1; H NMR
(200 MHz, CDCl3) δ 8.00 (d, J ) 6.6 Hz, 1H), 7.64 (dd, J )
8.4, 5.1 Hz, 2H), 7.16 (t, J ) 8.4 Hz, 2H), 6.92 (br d, J ) 8.4
Hz, 1H), 6.51 (d, J ) 6.6 Hz, 1H), 5.43 (dd, J ) 8.4, 4.9 Hz,
1H), 4.64 and 4.55 (d × 2, J ) 15.2 Hz, 1H × 2), 2.53 (m, 1H),
1.48 (s, 9H), 1.08 and 0.90 (d × 2, J ) 6.7 Hz, 3H × 2); optical
rotation [R]28 -14.8 (c 1.0, CH3CN). Anal. (C23H26FN5O4‚
D
0.7H2O) C, H, N.
N-{(1S)-1-(Meth yleth yl)-2-[5-(1-m eth yl-1-p h en yleth yl)-
1,3,4-oxa d ia zol-2-yl]-2-oxoeth yl}-2-[2-(4-flu or op h en yl)-6-
oxoh yd r op yr im id in yl]a ceta m id e (21k (F )). Derived from
8k and 19(F ) which was prepared from 15(F ): ivory amor-
phous solid; TLC Rf ) 0.50, EtOAc; MS (APCI, neg. 40 V) m/z
) 516 (M - H)-, 360, 189; IR (KBr) 3311, 3061, 2973, 2936,
2877, 1685, 1606, 1531, 1505, 1426, 1395, 1230, 1192, 1163,
N-[(1S)-2-(5-ter t-Bu tyl-1,3,4-oxa d ia zol-2-yl)-1-(m eth yl-
eth yl)-2-oxoeth yl]-2-(6-oxo-2-p h en ylh yd r op yr im id in yl)-
a ceta m id e (21e(H)). To a stirred suspension of Dess-Martin
periodinane (ca. 77%, 515 mg, 0.93 mmol) in CH2Cl2 (10 mL)
was added a suspension of the alcohol 20e(H) (a mixture of
two isomers: 282 mg, 0.64 mmol) in CH2Cl2 (5 mL) under Ar
at room temperature. After 1 h, the reaction mixture was
poured into water and extracted with EtOAc. The organic layer
was washed with water, and then brine, dried over anhydrous
MgSO4, and concentrated in vacuo. Purification by silica gel
column chromatography [FL60D, EtOAc/n-hexane (1/1 f 1/0)]
and washing with CHCl3 gave 21e(H) (242 mg, 86%) as a
white amorphous powder: mp 79-85 °C; TLC Rf ) 0.44,
EtOAc; MS (APCI, neg. 40 V) m/z ) 436 (M - H)-, 342, 298,
171, 125; IR (KBr) 3299, 3061, 2974, 1936, 1876, 1685, 1525,
1493, 1465, 1447, 1424, 1406, 1390, 1371, 1252, 1193, 1048,
1047, 1032, 1017, 978, 847, 700 cm-1 1H NMR (200 MHz,
;
CDCl3) δ 8.00 (d, J ) 6.4 Hz, 1H), 7.72-7.51 (m, 2H), 7.46-
7.04 (m, 7H), 6.88 (d, J ) 8.4 Hz, 1H), 6.50 (d, J ) 6.4 Hz,
1H), 5.38 (dd, J ) 8.4, 5.0 Hz, 1H), 4.61 (d, J ) 15.4 Hz, 1H),
4.53 (d, J ) 15.4 Hz, 1H), 2.65-2.38 (m, 1H), 1.89 (s, 6H),
1.06 (d, J ) 7.0 Hz, 3H), 0.87 (d, J ) 7.0 Hz, 3H); optical
rotation [R]26 -29.4 (c 0.5, CH3CN). Anal. (C28H28FN5O4‚
D
0.5H2O) C, H, N.
Meth yl (2R)-2-(3-Eth oxyca r bon ylm eth ylu r eid o)-3-m e-
th ylbu ta n oa te (26a ). To a stirred suspension of methyl (2R)-
2-amino-3-methylbutanoate hydrochloride (25a ) (2.59 g, 15.5
mmol) in EtOAc (85 mL) were added dropwise triethylamine
(2.16 mL, 15.5 mmol) and then ethyl isocyanatoacetate (2.00
g, 15.5 mmol) at 0 °C. The reaction mixture was stirred at
room temperature for 4.5 h, and poured into water and
extracted with EtOAc. The organic layer was washed with 5%
KHSO4, water and then brine, dried over anhydrous MgSO4,
and concentrated in vacuo. The residue was purified by silica
gel column chromatography [FL60D, MeOH/CHCl3 (0/100 f
1/50)] to afford the urea 26a (3.84 g, 95%) as a colorless
liquid: TLC Rf ) 0.69, CHCl3/MeOH (9/1); MS (APCI, pos. 40
1
1017, 977, 834, 764, 704 cm-1; H NMR (200 MHz, CDCl3) δ
8.02 (d, J ) 6.6 Hz, 1H), 7.65-7.40 (m, 5H), 6.84 (d, J ) 8.4
Hz, 1H), 6.51 (d, J ) 6.6 Hz, 1H), 5.44 (dd, J ) 8.4, 4.8 Hz,
1H), 4.66 (d, J ) 15.2 Hz, 1H), 4.55 (d, J ) 15.2 Hz, 1H), 2.65-
2.39 (m, 1H), 1.48 (s, 9H), 1.08 (d, J ) 6.8 Hz, 3H), 0.89 (d, J
) 7.0 Hz, 3H); optical rotation [R]25 -12.40 (c 0.49, MeCN).
D
Anal. (C23H27N5O4‚0.3H2O) C, H, N.
P r ep a r a tion of 21d ,e(H) a n d 21d ,e,k (F ). Using es-
sentially the same procedures as described for the preparation
of 21e(H), the following compounds were prepared.
1
V) m/z ) 261 (M + H)+, 229, 215, 201, 183, 155, 132, 104; H
NMR (300 MHz, CDCl3) δ 5.26 (d, J ) 8.4 Hz, 1H), 5.19 (m,
1H), 4.42 (dd, J ) 8.4, 4.8 Hz, 1H), 4.21 (q, J ) 7.2 Hz, 2H),
4.06 and 3.94 (d × 2, J ) 18.5 Hz, 1H × 2), 3.74 (s, 3H), 2.20-
2.04 (m, 1H), 1.28 (t, J ) 7.2 Hz, 3H), 0.96 (d, J ) 6.6 Hz,
N-{(1S)-2-[5-(1-Met h ylcyclop r op yl)-1,3,4-oxa d ia zol-2-
yl]-1-(m eth yleth yl)-2-oxoeth yl}-2-(6-oxo-2-p h en ylh yd r o-
p yr im id in yl)a ceta m id e (21d (H)). Derived from 8d and
19(H) which was prepared from 15(H): yellowish amorphous
solid; TLC Rf ) 0.60, MeOH/CHCl3 (1/10); MS (APCI, pos. 40
V) m/z ) 436 (M + H)+, 344, 125; IR (KBr) 3462, 3065, 2969,
2936, 1683, 1549, 1525, 1494, 1448, 1426, 1390, 1255, 1193,
3H), 0.89 (d, J ) 6.9 Hz, 3H); optical rotation [R]25 +2.5 (c
D
1.9, MeCN).
2-[(4R)-4-(Met h ylet h yl)-2,5-d ioxoim id a zolid in yl]a ce-
tic Acid (22a ). A solution of the urea 26a (3.24 g, 12.5 mmol)
in concentrated HCl (70 mL) was refluxed for 18 h. After
cooling to room temperature, the reaction mixture was diluted
with water, and extracted with EtOAc. The organic layer was
dried over anhydrous MgSO4, and concentrated in vacuo. The
residual solid was dried by azeotropic removal of water with
toluene, and then washed with ether to afford the hydantoin
22a (2.04 g, quant.) as a white powder: TLC Rf ) 0.16, CHCl3/
MeOH/AcOH (18/1/1); MS (APCI, neg. 40 V) m/z ) 199 (M -
H)-, 155; 1H NMR (200 MHz, CDCl3) δ 6.62 (m, 0.3H), 4.23 (s,
2H), 4.05 (d, J ) 3.8 Hz, 1H), 2.38-2.16 (m, 1H), 1.06 and
1027, 977, 931, 903, 831, 787, 767, 705, 553 cm-1 1H NMR
;
(200 MHz, CDCl3) δ 8.01 (d, J ) 6.6 Hz, 1H), 7.61-7.40 (m,
5H), 6.84 (br d, J ) 8.4 Hz, 1H), 6.51 (d, J ) 6.6 Hz, 1H), 5.41
(dd, J ) 8.4, 5.0 Hz, 1H), 4.62 and 4.57 (d × 2, J ) 15.0 Hz,
1H × 2), 2.48 (m, 1H), 1.61 (s, 3H), 1.44 (m, 2H), 1.08 (m, 5H),
0.87 (d, J ) 6.6 Hz, 3H); optical rotation [R]27 -32.2 (c 0.7,
D
CH3CN). Anal. (C23H25N5O4‚0.2H2O) C, H, N.
N-{(1S)-2-[5-(1-Met h ylcyclop r op yl)-1,3,4-oxa d ia zol-2-
yl]-1-(m et h ylet h yl)-2-oxoet h yl}-2-[2-(4-flu or op h en yl)-6-
oxoh yd r op yr im id in yl]a ceta m id e (21d (F )). Derived from
8d and 19(F ) which was prepared from 15(F ): ivory powder;

1280 J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 8
Ohmoto et al.
0.96 (d × 2, J ) 7.0 Hz, 3H × 2); optical rotation [R]25 +2.5
et h yl)-2-oxoet h yl]-2-[5-a m in o-6-oxo-2-(3-p yr id yl)h yd r o-
p yr im id in yl]a ceta m id e (24d ). Derived from 8e and 27
which was prepared by Zeneca’s method:20 brown yellow solid;
TLC Rf ) 0.12, EtOAc; MS (APCI, pos. 40 V) m/z ) 454 (M +
H)+; IR (KBr) 3336, 3045, 2974, 2937, 2877, 1718, 1668, 1610,
1542, 1464, 1439, 1413, 1371, 1299, 1253, 1204, 1043, 1028,
979, 926, 900, 821, 787, 740, 716, 637, 479 cm-1; 1H NMR (200
MHz, CDCl3) δ 8.79 (d, J ) 1.8 Hz, 1H), 8.69 (dd, J ) 4.8, 1.8
Hz, 1H), 7.94 (dt, J ) 8.4, 1.8 Hz, 1H), 7.51 (s, 1H), 7.38 (dd,
J ) 8.4, 4.8 Hz, 1H), 7.07 (d, J ) 8.5 Hz, 1H), 5.44 (dd, J )
8.5, 4.8 Hz, 1H), 4.63 (s, 2H), 4.16 (br s, 2H), 2.52 (m, 1H),
1.48 (s, 9H), 1.06 and 0.89 (d × 2, J ) 6.8 Hz, 3H × 2); optical
D
(c 0.5, MeCN).
N -{(1S )-2-(5-t er t -B u t y l-1,3,4-o x a d ia zo l-2-y l)-2-h y -
dr oxy-1-(m eth yleth yl)eth yl}-2-[(4R)-4-(m eth yleth yl)-2,5-di-
oxoim id a zolid in yl]a ceta m id e (23a ). To a stirred mixture
of the hydantoin 22a (218 mg, 1.09 mmol), amino alcohol 8e
(317 mg, 1.20 mmol) and HOBt‚H2O (184 mg, 1.20 mmol) in
DMF (3.5 mL), were added EDC‚HCl (230 mg, 1.20 mmol) and
then N-methylmorpholine (0.132 mL, 1.20 mmol) under Ar at
0 °C. After 15 min, the reaction mixture was stirred at room
temperature for another 14 h, and poured into water and
extracted with EtOAc. The organic layer was washed with 10%
citric acid, saturated NaHCO3, water and then brine, dried
over anhydrous Na2SO4 and concentrated in vacuo to give the
alcohol 23a (ca. 1.09 mmol) as a pale yellow amorphous solid.
The product was used for the next reaction without further
purification: TLC Rf ) 0.20, AcOH/i-PrOH/CHCl3 (1/1/18); MS
rotation [R]29 -22.9 (c 1.1, CH3CN). Anal. (C22H27N7O4‚
D
0.1H2O) C, H, N.
ter t-Bu t yl (2S)-1-[(2S)-3-Met h yl-2-(m et h ylsu lfon a m i-
d o)bu ta n oyl]p yr r olid in e-2-ca r boxyla te (39). To a stirred
ice-cooled solution of tert-butyl (2S)-1-((2S)-2-amino-3-meth-
ylbutanoyl)pyrrolidine-2-carboxylate hydrochloride (38) (1.00
g, 3.26 mmol) in CH2Cl2 (4 mL) were added dropwise with
stirring methanesulfonyl chloride (0.28 mL, 3.6 mmol) and
then N-methylmorpholine (0.79 mL, 7.2 mmol). The resulting
solution was stirred for 1 h and then at room temperature for
3 h. The reaction mixture was cooled again with an ice bath,
and additional methanesulfonyl chloride (0.125 mL, 1.6 mmol)
and N-methylmorpholine (0.20 mL, 1.8 mmol) were added. The
reaction mixture was stirred for another 1 h, and then at room
temperature for 45 min. The reaction mixture was quenched
with saturated NH4Cl, and the product was extracted three
times with EtOAc. The combined organic layers were washed
with saturated NaHCO3, brine, dried over anhydrous Na2SO4,
and concentrated in vacuo. The residue was purified by silica
gel column chromatography [FL60D, CHCl3/MeOH (1/0 f 100/
1)] to afford the tert-butyl ester 39 (639 mg, 56%): TLC Rf )
0.77, CHCl3/MeOH (8/1); MS (APCI, pos. 20 V) m/z ) 371 (M
1
(APCI, pos. 40 V) m/z ) 410 (M + H)+; H NMR (200 MHz,
CDCl3) δ 7.13-6.89 (m, 1H), 6.73. 6.30, 6.20 and 6.10 (br s ×
4, 1H), 5.14 and 5.01 (m × 2, 1H), 4.39-4.00 (m, 5H), 2.24 (m,
1H), 1.80 (m, 1H), 1.41 and 1.38 (s × 2, 9H), 1.16-0.80 (m,
12H).
N-{(1S)-2-(5-ter t-Bu tyl-1,3,4-oxa d ia zol-2-yl)-1-(m eth yl-
eth yl)-2-oxoeth yl}-2-[(4R)-4-(m eth yleth yl)-2,5-d ioxoim i-
d a zolid in yl]a ceta m id e (24a ). To a stirred suspension of
Dess-Martin periodinane (ca. 77%, 474 mg, 0.86 mmol) in
CH2Cl2 (5.5 mL) was added a solution of the alcohol 23a (ca.
0.78 mmol) in CH2Cl2 (10 mL) under Ar at room temperature.
After 1 h, the reaction mixture was poured into water and
extracted with EtOAc. The organic layer was washed with
water and with brine, dried over anhydrous Na2SO4, and
concentrated in vacuo. Purification of the residue by silica gel
column chromatography [FL60D, MeOH/CHCl3 (0/100 f
1/100)] gave the ketone 24a (309 mg, 70% in 2 steps) as a white
amorphous solid: TLC Rf ) 0.41, MeOH/CHCl3 (1/10); MS
(APCI, pos. 40 V) m/z ) 408 (M + H)+; IR (KBr) 3318, 2971,
2937, 2877, 1776, 1718, 1543, 1452, 1393, 1371, 1356, 1321,
1297, 1257, 1155, 1018, 918, 829, 753, 624 cm-1; 1H NMR (200
MHz, DMSO-d6) δ 8.65 (d, J ) 7.4 Hz, 1H), 8.23 (br s, 1H),
5.09 (m, 1H), 4.04 (br s, 2H), 3.92 (br d, J ) 3.8 Hz, 1H), 2.34
(m, 1H), 2.00 (m, 1H), 1.38 (s, 9H), 1.00-0.73 (m, 12H); optical
rotation [R]26D -3.5 (c 1.1, MeCN). Anal. (C19H29N5O5‚0.2CH3-
CO2C2H5) C, H, N.
1
+ Na)+, 349 (M + H)+, 293 (M - C4H9 + 2H)+; H NMR (200
MHz, CDCl3) δ 5.28 and 5.21 (br d × 2, J ) 9.8 Hz, 1H), 4.42
(dd, J ) 8.4, 5.0 Hz, 0.7H), 4.30 (dd, J ) 8.0, 2.6 Hz, 0.3H),
3.99 (dd, J ) 9.8, 4.9 Hz, 1H), 3.80-3.40 (m, 2H), 2.93 and
2.86 (s × 2, 3H), 2.40-1.80 (m, 5H), 1.49 and 1.45 (s × 2, 9H),
1.10 and 0.94 (d × 2, J ) 7.0 Hz, 2.1H × 2), 1.07 and 0.85 (d
× 2, J ) 6.6 Hz, 0.9H × 2).
(2S)-1-[(2S)-3-Meth yl-2-(m eth ylsu lfon a m id o)bu ta n oyl]-
p yr r olid in e-2-ca r boxylic Acid (22e). To a stirred tert-butyl
ester 39 (453 mg, 1.30 mmol) was added ice-cooled 90%
trifluoroacetic acid/water (5.4 mL) at 0 °C. The resulting
solution was stirred at this temperature for 1.5 h, and
concentrated. The residue was dried by azeotropic removal of
water with toluene to give the carboxylic acid 22e (423 mg,
quant.). The crude product was used for the next step without
further purification: TLC Rf ) 0.41, CHCl3/MeOH (9/1); MS
(APCI, pos. 40 V) m/z ) 293 (M + H)+, 222; 1H NMR (200 MHz,
CDCl3) δ 5.65 and 5.52 (br d × 2, J ) 9.7 Hz, 1H), 4.59 (dd, J
) 7.5, 5.3 Hz, 0.8H), 4.49 (dd, J ) 8.1, 2.3 Hz, 0.2H), 4.00 (dd,
J ) 10.0, 5.8 Hz, 0.8 H), 3.88 (dd, J ) 9.2, 4.2 Hz, 0.2 H),
3.82-3.42 (m, 2H), 2.96 and 2.91 (s × 2, 3H), 2.40-1.80 (m,
5H), 1.07, 0.96, and 0.89 (d × 3, J ) 6.6 Hz, 6H).
P r ep a r a tion of 24b,c. Using essentially the same proce-
dures as described for the preparation of 24a , the following
compounds were prepared.
N-[(1S)-2-(5-ter t-Bu tyl-1,3,4-oxa d ia zol-2-yl)-1-(m eth yl-
e t h yl)-2-oxoe t h yl]-2-[(4S )-4-(2-m e t h ylp r op yl)-2,5-d i-
oxoim id a zolid in yl]a ceta m id e (24b). Derived from 8e and
22b which was prepared from 25b: white amorphous solid;
TLC (HPTLC) Rf ) 0.62 MeOH/CHCl3 (1/10); MS (APCI, pos.
40 V) m/z ) 422 (M + H)+; IR (KBr) 3318, 2968, 2875, 1780,
1718, 1543, 1455, 1390, 1370, 1336, 1254, 1206, 1157, 1047,
1017, 955, 924, 884, 826, 763, 624, 547 cm-1 1H NMR (200
;
MHz, CDCl3) δ 8.67 (br d, J ) 6.8 Hz, 1H), 8.32 (br s, 1H),
5.08 (m, 1H), 4.03 (m, 3H), 2.32 (m, 1H), 1.75 (m, 1H), 1.60-
1.25 (m, 11H), 0.87 (m, 12H); optical rotation [R]26 -6.8 (c
D
{(2S)-1-[(2S)-3-Meth yl-2-(m eth ylsu lfon am ido)bu tan oyl]-
p yr r olid in -2-yl}-N-{(1S)-2-(5-ter t-bu tyl-1,3,4-oxa d ia zol-2-
yl)-2-h yd r oxy-1-(m eth yleth yl)eth yl}ca r boxa m id e (23e).
To a stirred mixture of the carboxylic acid 22e (267 mg, 0.91
mmol), the amino alcohol 8e (321 mg, 1.09 mmol) and HOBt‚
H2O (181 mg, 1.18 mmol) in DMF (10 mL), were added EDC‚
HCl (192 mg, 1.00 mmol) and then N-methylmorpholine (0.120
mL, 1.09 mmol) under Ar at 0 °C. The reaction mixture was
stirred at room temperature for 2 h, then poured into water
and extracted with EtOAc. The organic layer was washed with
saturated NH4Cl, saturated NaHCO3, water, and brine, dried
over anhydrous MgSO4 and concentrated in vacuo. The residue
was purified by silica gel column chromatography [FL60D,
CHCl3/MeOH (50/1 f 20/1)] to afford the alcohol 23e (310 mg,
68%) as a white amorphous solid. The product was used for
the next reaction without further purification: TLC (HPTLC)
Rf ) 0.13, CHCl3/MeOH (19/1); MS (APCI, pos. 40 V) m/z )
502 (M + H)+, 376, 127; 1H NMR (200 MHz, CDCl3) δ 7.43
0.8, CH3CN). Anal. (C20H31N5O5‚0.3H2O) C, H, N.
N-[(1S)-2-(5-ter t-Bu tyl-1,3,4-oxa d ia zol-2-yl)-1-(m eth yl-
e t h yl)-2-oxoe t h yl]-2-[(4R )-4-(in d ol-3-ylm e t h yl)-2,5-d i-
oxoim id a zolid in yl]a ceta m id e (24c). Derived from 8e and
22c which was prepared from 25c: yellow amorphous powder;
TLC Rf ) 0.46, EtOAc; MS (APCI, pos. 40 V) m/z ) 495 (M +
H)+; IR (KBr) 3420, 2974, 2936, 1776, 1718, 1542, 1457, 1343,
1232, 1154, 1100, 1015, 924, 745, 624, 545, 424 cm-1; 1H NMR
(200 MHz, CDCl3) δ 10.90 (br s, 1H), 8.66 (d, J ) 7.0 Hz, 1H),
8.23 (br s, 1H), 7.51 (br d, J ) 7.3 Hz, 1H), 7.33 (br d, J ) 7.3
Hz, 1H), 7.16 (d, J ) 1.8 Hz, 1H), 7.06 (dt, J ) 1.2, 7.3 Hz,
1H), 6.97 (dt, J ) 1.2, 7.3 Hz, 1H), 5.10 (m, 1H), 4.38 (m, 1H),
3.93 (s, 2H), 3.16 (dd, J ) 14.8, 4.8 Hz, 1H), 2.98 (dd, J )
14.8, 6.8 Hz, 1H), 2.34 (m, 1H), 1.41 and 1.40 (s × 2, 9H), 0.95
and 0.89 (d × 2, J ) 6.6 Hz, 3H × 2); optical rotation [R]28
D
-3.0 (c 0.7, CH3CN). Anal. (C25H30N6O5‚0.3C6H14) C, H, N.
N-[(1S)-2-(5-ter t-Bu tyl-1,3,4-oxa d ia zol-2-yl)-1-(m eth yl-

Orally Active Nonpeptidic Inhibitors of HNE
J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 8 1281
and 7.10 (d × 2, J ) 10.0 and 9.4 Hz, 1H), 6.73-6.56 and 5.97-
5.78 (m × 2, 1H), 5.21-5.07 (m, 1H), 4.61-4.53 and 4.53-
4.44 (m × 2, 1H), 4.29-4.18 and 4.05-3.92 (m × 2, 2H), 3.79-
3.51 (m, 2H), 3.02 and 2.92 (s × 2, 3H), 2.30-1.67 (m, 6H),
1.42 and 1.38 (s × 2, 9H), 1.18-0.79 (m, 12H).
pholine (0.13 mL, 1.20 mmol) under Ar at 0 °C. After 15 min,
the reaction mixture was stirred at room temperature for 14
h, then poured into water and extracted with EtOAc. The
organic layer was washed with 10% citric acid, saturated
NaHCO3, water, and finally brine, dried over anhydrous Na2-
SO4, and concentrated in vacuo. The resulting white amor-
phous solid (alcohol 23g: ca. 1.09 mmol) was used for the next
reaction without further purification: TLC Rf ) 0.71 and 0.67,
MeOH/CHCl3 (1/10); MS (APCI, pos. 20 V) m/z ) 439 (M +
H)+; 1H NMR (200 MHz, CDCl3) δ 7.96 (m, 2H), 7.70 (m, 1H),
7.42 (m, 4H), 7.00 (m, 1H), 6.84 and 6.78 (d × 2, J ) 8.0 Hz,
1H), 5.18-4.75 (m, 3H), 4.35-3.93 (m, 2H), 2.18-1.75 (m, 1H),
1.38 and 1.37 (s × 2, 9H), 1.02, 0.89, 0.84 and 0.81 (d × 4, J
) 7.0 Hz, 6H).
{(2S)-1-[(2S)-3-Meth yl-2-(m eth ylsu lfon am ido)bu tan oyl]-
p yr r olid in -2-yl}-N-{(1S)-2-(5-ter t-bu tyl-1,3,4-oxa d ia zol-2-
yl)-1-(m eth yleth yl)-2-oxoeth yl}ca r boxa m id e (24e). To a
suspension of Dess-Martin periodinane (ca. 77%, 353 mg, 0.64
mmol) in CH2Cl2 (9 mL) was added a solution of the alcohol
23e (292 mg, 0.58 mmol) in CH2Cl2 (12 mL) under Ar at room
temperature. After 1 h, the reaction mixture was poured into
water and extracted with EtOAc. The organic layer was
washed with brine, dried over anhydrous Na2SO4, and con-
centrated in vacuo. Purification of the residue by silica gel
column chromatography [FL60D, EtOAc/n-hexane (1/2)] gave
the ketone 24e (260 mg, 90% in 2 steps) as a white amorphous
solid: TLC Rf ) 0.59, EtOAc; MS (APCI, neg. 40 V) m/z ) 498
(M - H)-, 404; IR (KBr) 3347, 2973, 2937, 2878, 1719, 1685,
1636, 1543, 1466, 1407, 1371, 1323, 1157, 1140, 1046, 1017,
983, 761, 521 cm-1; 1H NMR (200 MHz, CDCl3) δ 7.37 (d, J )
7.5 Hz, 1H), 5.58 (d, J ) 9.8 Hz, 1H), 5.37 (dd, J ) 7.5, 4.8 Hz,
1H), 4.69 (dd, J ) 8.1, 2.9 Hz, 1H), 3.99 (dd, J ) 9.8, 5.8 Hz,
1H), 3.86-3.43 (m, 2H), 2.92 (s, 3H), 2.63-1.80 (m, 6H), 1.47
(s, 9H), 1.06, 1.05, 0.97 and 0.93 (d × 4, J ) 6.6, 6.6, 6.6 and
6.8 Hz, 3H × 4); optical rotation [R]24D -56.5, (c 0.515, MeCN).
Anal. (C22H37N5O6S‚0.1H2O) C, H, N, S.
N-{(1S)-2-(5-ter t-Bu tyl-1,3,4-oxa d ia zol-2-yl)-1-(m eth yl-
et h yl)-2-oxoet h yl}-2-(6-p h en yl-2-p yr id yloxy)a cet a m id e
(24g). To a stirred suspension of Dess-Martin periodinane
(ca. 77%, 660 mg, 1.20 mmol) in CH2Cl2 (8 mL) was added a
suspension of the alcohol 23g (ca. 1.09 mmol) in CH2Cl2 (16
mL) under Ar at room temperature. After 2 h, the reaction
mixture was poured into water and extracted with EtOAc. The
organic layer was washed with water and then brine, dried
over anhydrous Na2SO4, and concentrated in vacuo. Purifica-
tion of the crude product by silica gel column chromatography
[FL60D, EtOAc/n-hexane (1/4)] gave the ketone 24g (413 mg,
87% in 2 steps) as a white amorphous solid: TLC Rf ) 0.64,
EtOAc/n-hexane (1/1); MS (APCI, pos. 40 V) m/z ) 437 (M +
H)+; IR (KBr) 3428, 2974, 1718, 1685, 1596, 1575, 1542, 1447,
1370, 1324, 1246, 1156, 1084, 1045, 880, 809, 766, 695, 623,
425, 408 cm-1; 1H NMR (200 MHz, CDCl3) δ 7.99 (m, 2H), 7.74
(t, J ) 8.2 Hz, 1H), 7.50-7.35 (m, 4H), 7.16 (br d, J ) 9.0 Hz,
1H), 6.87 (d, J ) 8.2 Hz, 1H), 5.49 (dd, J ) 9 0.0, 5.2 Hz, 1H),
5.12 and 4.93 (d × 2, J ) 15.6 Hz, 1H × 2), 2.47 (m, 1H), 1.45
(s, 9H), 0.97 and 0.79 (d × 2, J ) 6.8 Hz, 3H × 2); optical
N-[(1S)-2-(5-ter t-Bu tyl-1,3,4-oxa d ia zol-2-yl)-1-(m eth yl-
et h yl)-2-oxoet h yl]-2-[5-(4-ch lor op h en yl)-1,2-d ih yd r o-2-
oxo-3H-1,4-ben zo[f]d ia zep in yl]a ceta m id e (24f). Derived
from 8e and 22f which was prepared according to a patented
method:26 white amorphous powder; TLC Rf ) 0.28, EtOAc/
n-hexane (1/1); MS (APCI, neg. 40 V) m/z ) 534 (M - H)-; IR
(KBr) 3322, 2974, 2876, 1685, 1609, 1542, 1488, 1450, 1371,
rotation [R]25 +11.3 (c 1.03, MeCN). Anal. (C24H28N4O4‚
1324, 1271, 1195, 1161, 1091, 1016, 934, 839, 762, 666 cm-1
;
D
1H NMR (200 MHz, DMSO-d6) δ 7.66-7.50 (m, 4H), 7.44-
7.16 (m, 4.4H), 6.93 (d, J ) 8.0 Hz, 0.6H), 5.42 and 5.31 (dd ×
2, J ) 8.0, 4.8 Hz, 1H), 4.89 and 4.86 (d × 2, J ) 10.6 Hz, 1H),
4.83 and 4.73 (d × 2, J ) 15.3 Hz, 1H), 4.22 and 4.10 (d × 2,
J ) 15.3 Hz, 1H), 3.94 and 3.88 (d × 2, J ) 10.6 Hz, 1H),
2.66-2.34 (m, 1H), 1.48 and 1.44 (s × 2, 9H), 1.05 and 1.04 (d
× 2, J ) 7.0 Hz, 3H), 0.89 and 0.83 (d × 2, J ) 7.0 Hz, 3H);
0.1H2O) C, H, N.
ter t-Bu tyl (2S)-2-{N-[(1S)-2-(5-ter t-Bu tyl-1,3,4-oxa d ia -
zol-2-yl)-2-h yd r oxy-1-(m et h ylet h yl)et h yl]ca r b a m oyl}-
in d olin eca r boxyla te (28a ). To a stirred mixture of the (2S)-
1-(tert-butoxycarbonyl)indoline-2-carboxylic acid (27a ) (6.58 g,
25.0 mmol), the amino alcohol 8e (7.25 g, 27.5 mmol) and
HOBt‚H2O (4.21 g, 27.5 mmol) in DMF (77 mL), were added
EDC‚HCl (5.27 g, 27.5 mmol) and then N-methylmorpholine
(3.02 mL, 27.5 mmol) under Ar at 0 °C. After 10 min, the
reaction mixture was stirred at room temperature for 20 h,
and poured into water and extracted with EtOAc. The organic
layer was washed with 10% citric acid, saturated NaHCO3,
water, and then brine, dried over anhydrous Na2SO4, and
concentrated in vacuo. Purification of the residual beige solid
by silica gel column chromatography [FL60D, EtOAc/n-hexane,
(1/9 f 2/1)] gave the Boc alcohol 28a (11.3 g, 96%) as a pale
yellow amorphous powder: TLC Rf ) 0.52 and 0.48, MeOH/
optical rotation [R]25 -4.0 (c 0.5, CH3CN). Anal. (C28H30
-
D
ClN5O4‚0.1C6H14) C, H, N.
Eth yl 2-(6-P h en yl-2-p yr id yloxy)a ceta te (41). A mixture
of 6-phenyl-2-pyridone 40 (1.00 g, 5.85 mmol), ethyl bromo-
acetate (1.46 g, 8.77 mmol), K2CO3 (2.43 g, 17.55 mmol) and
DMF (12 mL) was stirred at room temperature for 16 h, and
then poured into water and extracted with EtOAc. The organic
layer was washed with 1 N HCl, water and then brine, dried
over anhydrous Na2SO4, and concentrated in vacuo. The
residual yellow oil was purified by silica gel column chroma-
tography [Merck 7734, EtOAc/n-hexane (1/9)] to give the ester
41 (1.47 g, 98%) as a clear syrup: TLC Rf ) 0.80, EtOAc/n-
1
CHCl3 (1/10); MS (APCI, pos. 20 V) m/z ) 473 (M + H)+; H
NMR (200 MHz, CDCl3) δ 7.57 and 6.73 (m × 2, 1H), 7.27-
6.90 (m, 4H), 5.11-4.75 (m, 2H), 4.35-3.92 (m, 2H), 3.65-
3.00 (m, 2H), 2.00 and 1.70 (m × 2, 1H), 1.56, 1.46, 1.41 and
1.34 (s × 4, 18H), 1.05-0.80 (m, 6H).
1
hexane (1/2); MS (APCI, pos. 40 V) m/z ) 258 (M + H)+; H
NMR (200 MHz, CDCl3) δ 7.97 (m, 2H), 7.68 (dd, J ) 8.0, 7.4
Hz, 1H), 7.50-7.38 (m, 4H), 6.83 (d, J ) 8.0 Hz, 1H), 4.96 (s,
2H), 4.24 (q, J ) 7.4 Hz, 2H), 1.26 (t, J ) 7.4 Hz, 3H).
(2S)-In d olin -2-yl-N-[(1S)-2-(5-ter t-bu tyl-1,3,4-oxa d ia zol-
2-yl)-2-h yd r oxy-1-(m eth yleth yl)eth yl]ca r boxa m id e Hy-
d r och lor id e (29a ). A mixture of the Boc alcohol 28a (10.3 g,
21.8 mmol) and 4 N HCl in dioxane (40 mL) was stirred at
room temperature for 1 h. Concentration of the reaction
mixture gave the amino alcohol 29a (9.5 g) as a white powder
quantitatively. The product was used for the next reaction
without further purification: TLC Rf ) 0.49 and 0.46, CHCl3/
MeOH (9/1); LC MS (APCI, pos. 40 V) m/z ) 373 (M + H)+; 1H
NMR (200 MHz, DMSO-d6) δ 8.43 and 8.24 (d × 2, J ) 10.0
Hz, 1H), 7.36-7.08 (m, 5H), 5.10-5.00, 4.75-4.58 and 3.95-
3.83 (m × 3, 3H), 3.60-3.28, 3.00-2.85 and 2.65-2.57 (m ×
2, 2H), 2.35-2.10 and 1.97-1.75 (m × 2, 1H), 1.18 and 1.11 (s
× 2, 9H), 1.07-0.83 (m, 6H).
2-(6-P h en yl-2-p yr id yloxy)a cetic Acid (22g). To a stirred
solution of the ester 41 (1.46 g, 5.68 mmol) in DME (34 mL)
was added 1 N LiOH (17 mL) at 0 °C. After stirring for 1.5 h,
the reaction mixture was acidified with 1 N HCl (34 mL), and
extracted with EtOAc. The organic layer was washed with
water and with brine, dried over anhydrous MgSO4, and
concentrated in vacuo to afford the carboxylic acid 22g (1.29
g, 99%): TLC Rf ) 0.68, AcOH/i-PrOH/CHCl3 (1/1/18); 1H NMR
(200 MHz, CDCl3) δ 7.93 (m, 2H), 7.70 (t, J ) 8.2 Hz, 1H),
7.45-7.30 (m, 4H), 6.83 (d, J ) 8.2 Hz, 1H), 5.01 (s, 2H).
N-{(1S)-2-(5-ter t-Bu tyl-1,3,4-oxa d ia zol-2-yl)-2-h yd r oxy-
1-(m et h ylet h yl)et h yl}-2-(6-p h en yl-2-p yr id yloxy)a cet a -
m id e (23g). To a stirred solution of the carboxylic acid 22g
(250 mg, 1.09 mmol), the amino alcohol 8e (316 mg, 1.20 mmol)
and HOBt‚H2O (184 mg, 1.20 mmol) in DMF (3.5 mL) were
added EDC‚HCl (230 mg, 1.20 mmol) and then N-methylmor-
Met h ylet h yl (2S)-2-{N-[(1S)-2-(5-ter t-Bu t yl-1,3,4-oxa -
d ia zol-2-yl)-2-h yd r oxy-1-(m eth yleth yl)eth yl]ca r ba m oyl}-
in d olin eca r boxyla te (30a ). To a stirred solution of the amino

1282 J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 8
Ohmoto et al.
alcohol 29a (1.51 g, 3.69 mmol) in CH2Cl2 (20 mL) were added
dropwise 1.0 M isopropyl chloroformate in toluene (4.06 mL,
4.06 mmol) and N-methylmorpholine (0.900 mL, 8.18 mmol)
under Ar at 0 °C. After 1 h, the reaction mixture was stirred
at room temperature for 3.5 h. Additional 1.0 M isopropyl
chloroformate in toluene (1.22 mL, 1.22 mmol) and N-meth-
ylmorpholine (0.300 mL, 2.73 mmol) were added twice at 0 °C
and the reaction mixture was stirred at room temperature.
Then the reaction mixture was poured into ice-cooled 10% citric
acid and extracted with EtOAc. The organic layer was washed
with saturated NaHCO3, and then brine, and dried over
anhydrous Na2SO4. Concentration followed by purification by
silica gel column chromatography [Merck 7734, n-hexane/
EtOAc (1/1 f 1/2)] gave the alcohol 30a (1.16 g, 69%) as a
pale yellow amorphous powder: TLC Rf ) 0.55 and 0.46,
EtOAc/n-hexane (2/1); MS (APCI, pos. 20 V) m/z ) 459 (M +
H)+; 1H NMR (200 MHz, DMSO-d6) δ 8.06-7.62 (m, 1H), 7.20-
6.83 (m, 4H), 6.29 and 6.19 (d × 2, J ) 6.2 Hz and J ) 5.4 Hz,
1H), 5.06-4.60 (m, 3H), 4.30-4.10 and 3.97-3.80 (m × 2, 1H),
3.50-3.10 (m, 1H), 2.67-2.45, 2.37-2.01 and 1.95-1.67 (m ×
3, 2H), 1.40-1.05 (m, 15H), 1.05-0.75 (m, 6H).
and 7.03-6.94 (m × 3, 20H), 6.40-6.24 (m, 1H), 4.98 (t, J )
6.3 Hz, 1H), 3.70-3.55 and 3.08-2.97 (m × 2, 2H), 2.35-2.20
(m, 1H), 1.37 (s, 9H), 0.84 and 0.83 (d × 2, J ) 6.6 Hz, 3H ×
2).
(2S)-1-(Im id a zol-4-ylca r bon yl)in d olin -2-yl-N-[(1S)-2-(5-
-ter t-b u t yl-1,3,4-oxa d ia zol-2-yl)-1-(m et h ylet h yl)-2-oxo-
eth yl]ca r boxa m id e Hyd r och lor id e (24j). A solution of the
ketone 34a (1.26 g, 1.79 mmol) in trifluoroacetic acid/water
(19/1; 10 mL) was stirred at room temperature for 1 h. The
reaction mixture was evaporated to remove the solvent and
then treated with 4 N HCl in EtOAc followed by concentration
in vacuo. The resulting solid was washed successively with
ether, EtOAc and then n-hexane to afford the ketone 24j (796
mg, 89%) as a white powder: TLC Rf ) 0.46, CHCl3/MeOH
(9/1); MS (APCI, pos. 20 V) m/z ) 465 (M + H)+; IR (KBr)
3144, 2973, 2935, 2876, 2588, 1717, 1656, 1600, 1843, 1484,
1462, 1403, 1371, 1330, 1264, 1212, 1172, 1124, 1015, 849, 758
cm-1; 1H NMR (300 MHz, CD3OD) δ 9.08 (d, J ) 1.0 Hz, 1H),
8.00 (d, J ) 1.0 Hz, 1H), 7.30-7.07 (m, 4H), 5.63-5.53 (m,
1H), 5.12 (d, J ) 5.4 Hz, 1H), 3.87-3.73 and 3.35-3.22 (m ×
2, 2H), 2.55-2.37 (m, 1H), 1.43 (s, 9H), 1.01-0.94 (m, 6H);
optical rotation [R]25 -103.7 (c 1.0, DMF). Anal. (C24H29
-
D
Met h ylet h yl (2S)-2-{N-[(1S)-2-(5-ter t-Bu t yl-1,3,4-oxa -
d ia zol-2-yl)-1-(m et h ylet h yl)-2-oxoet h yl]ca r b a m oyl}in -
d olin eca r boxyla te (24h ). To a stirred suspension of Dess-
Martin periodinane (ca. 70%; 1.32 g, 2.40 mmol) in CH2Cl2 (14
mL) was added a solution of the alcohol 30a (1.09 g, 2.38 mmol)
in CH2Cl2 (26 mL) under Ar at room temperature. After 1 h,
the reaction mixture was poured into ice-cooled brine and
extracted with EtOAc. The organic layer was concentrated in
vacuo. Purification of the residue by silica gel column chro-
matography [FL60D, EtOAc/n-hexane (2/1)] gave the ketone
24h (952 mg, 88%) as a white powder: TLC Rf ) 0.22, EtOAc/
n-hexane (1/3); MS (APCI, pos. 20 V) m/z ) 457 (M + H)+; IR
(KBr) 3288, 2978, 1713, 1673, 1603, 1544, 1487, 1402, 1317,
1269, 1182, 1112, 1019, 907, 819, 751, 680 cm-1; 1H NMR (200
MHz, DMSO-d6) δ 7.69 (m, 1H), 7.30-7.12 and 7.06-6.95 (m
× 2, 4H), 5.37 (dd, J ) 8.0, 4.8 Hz, 1H), 5.22-4.92 (m, 2H),
3.60-3.25 (m, 2H), 2.58-2.33 (m, 1H), 1.47 (s, 9H), 1.45-1.28
(m, 6H), 1.03-0.92 and 0.87-0.73 (m × 2, 3H); optical rotation
ClN6O4‚0.5H2O) C, H, N.
(2S)-1-[(2S)-2-(ter t-Bu t oxyca r b on yla m in o)-3-m et h yl-
bu ta n oyl]in d olin -2-yl-N-[(1S)-2-(5-ter t-bu tyl-1,3,4-oxa d ia -
zol-2-yl)-2-h yd r oxy-1-(m et h ylet h yl)et h yl]ca r b oxa m id e
(35a ). To a stirred solution of Boc-L-valine (1.30 g, 6.00 mmol)
in CH2Cl2 (15 mL) were added dropwise pyridine (0.486 mL,
6.00 mmol) and then cyanuric fluoride (2.70 mL, 30.0 mmol)
under Ar at -20 °C. After 2 h, the reaction was quenched with
ice-water, and extracted with CH2Cl2. The organic layer was
washed with water, dried over anhydrous MgSO4, and con-
centrated in vacuo to afford the (2S)-2-(tert-butoxycarbony-
lamino)-3-methylbutanoyl fluoride (1.20 g, 92%) as colorless
needles: 1H NMR (200 MHz, CDCl3) δ 5.16-4.85 (m, 1H),
4.47-4.24 (m, 1H), 2.36-2.10 (m, 1H), 1.47 (s, 9H), 1.05 and
1.00 (d × 2, J ) 7.0 Hz, 3H × 2).
To a stirred solution of the amino alcohol 29a (1.65 g, 4.03
mmol) and 2,6-di-tert-butylpyridine (1.80 mL, 8.02 mmol) was
added dropwise a solution of (2S)-2-(tert-butoxycarbonylamino)-
3-methylbutanoyl fluoride (1.20 g, 5.50 mmol) in CH2Cl2 (5 mL)
at -25 °C. After 1 h, the reaction mixture was treated with
4-(dimethylamino)pyridine (489 mg, 4.00 mmol), stirred at 0
°C for 48 h, then quenched with 10% citric acid and extracted
with EtOAc. The organic layer was washed with saturated
NaHCO3 and then brine, dried over anhydrous Na2SO4, and
concentrated in vacuo. The residue was purified by silica gel
column chromatography [FL60D, CHCl3/MeOH (200/1 f 100/
1)] to afford the Boc alcohol 35a (721 mg, 31%) as an off-white
amorphous powder: TLC Rf ) 0.53, CHCl3/MeOH (1/9); MS
[R]25 -75.7 (c 1.0, MeCN). Anal. (C24H32N4O5‚0.5H2O) C, H,
D
N.
(2S)-1-{[1-(Tr ip h en ylm eth yl)im id a zol-4-yl]ca r bon yl}-
in d olin -2-yl-N-[(1S)-2-(5-ter t-bu tyl-1,3,4-oxa d ia zol-2-yl)-
2-h yd r oxy-1-(m eth yleth yl)eth yl]ca r boxa m id e (33a ). To a
stirred mixture of the carboxylic acid 32 (1.71 g, 4.84 mmol)
and the amino alcohol 29a (1.52 g, 3.72 mmol) in DMF (20
mL) were added EDC‚HCl (928 mg, 4.85 mmol) and then
N-methylmorpholine (0.532 mL, 4.84 mmol) under Ar at 0 °C.
The reaction mixture was stirred at room temperature for 60
h, and poured into 10% citric acid and extracted with EtOAc.
The organic layer was washed with saturated NaHCO3, and
then brine, dried over anhydrous Na2SO4, and concentrated
in vacuo. Purification of the residual solid by silica gel column
chromatography [Merck 7734, EtOAc/n-hexane (1/1 f 2/1)]
gave the alcohol 33a (1.91 g, 73%) as a white amorphous
powder: TLC Rf ) 0.41 and 0.31, EtOAc/n-hexane (2/1); 1H
NMR (200 MHz, CDCl3) δ 8.05-7.94 (m, 1H), 7.67-7.44 (m,
2H), 7.42-7.19, 7.18-7.00 and 6.80-6.71 (m × 3, 19H), 5.75-
4.82 (m, 3H), 4.40-4.04 (m, 1H), 3.72-3.22 (m, 2H), 1.70-
1.50 (m, 1H), 1.36 and 1.35 (s × 2, 9H), 0.87-0.50 (m, 6H).
1
(APCI, pos. 20 V) m/z ) 572 (M + H)+; H NMR (200 MHz,
CDCl3) δ 8.23 and 8.08 (d × 2, J ) 8.6 Hz, 1H), 7.35-7.01 and
6.94-6.88 (m × 2, 5H), 5.35-4.74, 4.37-4.15 and 4.07-3.90
(m × 3, 5H), 3.73-3.30 (m, 2H), 2.23-1.65 (m, 2H), 1.55-0.42
(m, 30H).
(2S)-1-((2S)-2-Am in o-3-m eth ylbu ta n oyl)in d olin -2-yl-N-
[(1S)-2-(5-ter t-bu tyl-1,3,4-oxadiazol-2-yl)-2-h ydr oxy-1-(m e-
th yleth yl)eth yl]ca r boxa m id e Hyd r och lor id e (36a ). A so-
lution of the Boc alcohol 35a (700 mg, 1.23 mmol) in EtOAc (1
mL) was treated with 4 N HCl in dioxane (4 mL), and stirred
at room temperature for 1 h, then concentrated in vacuo. The
residue was dried by azeotropic removal of water with toluene
to afford the amino alcohol 36a (577 mg) as a yellowish
amorphous powder quantitatively. The product was used for
the next reaction without further purification: TLC Rf ) 0.43
and 0.34, CHCl3/MeOH (9/1); MS (APCI, pos. 20 V) m/z ) 472
(M + H)+; 1H NMR (200 MHz, DMSO-d6) δ 8.60-8.25 and
8.15-8.04 (m × 2, 4H), 7.32-6.99 (m, 4H), 6.65-6.15 (m, 1H),
5.26-4.95 and 4.76-4.64 (m × 2, 2H), 4.23-4.15 and 3.96-
3.80 (m × 2, 1H), 3.72-3.13 (m, 2H), 2.88-2.70, 2.45-2.10
and 2.10-1.70 (m × 3, 3H), 1.30-0.90 (m, 21H).
(2S)-1-{[1-(Tr ip h en ylm eth yl)im id a zol-4-yl]ca r bon yl}-
in d olin -2-yl-N-[(1S)-2-(5-ter t-bu tyl-1,3,4-oxa d ia zol-2-yl)-
1-(m eth yleth yl)-2-oxoeth yl]car boxam ide (34a). To a stirred
suspension of Dess-Martin periodinane (ca. 70%; 1.41 g, 2.55
mmol) in CH2Cl2 (16 mL) was added a solution of the alcohol
33a (1.81 g, 2.55 mmol) in CH2Cl2 (33 mL) under Ar at room
temperature. After 4.5 h, the reaction mixture was poured into
ice-cooled brine and extracted with EtOAc. The organic layer
was concentrated in vacuo. Purification of the residue by silica
gel column chromatography [FL60D, EtOAc/n-hexane (1/2)]
gave the ketone 34a (1.36 g, 75%) as a pale yellow amorphous
powder: TLC Rf ) 0.26, EtOAc/n-hexane (1/2); MS (APCI, neg.
(2S)-1-[(2S)-3-Meth yl-2-(3-pyr idin ecar bam ido)bu tan oyl]-
in d olin -2-yl-N-[(1S)-2-(5-ter t-bu tyl-1,3,4-oxa d ia zol-2-yl)-
2-h yd r oxy-1-(m eth yleth yl)eth yl]ca r boxa m id e (37a ). To a
1
20 V) m/z ) 705 (M - H)-; H NMR (200 MHz, DMSO-d6) δ
8.64 (d, J ) 7.2 Hz, 1H), 8.11 (m, 1H), 7.56-7.34, 7.24-7.06

Orally Active Nonpeptidic Inhibitors of HNE
J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 8 1283
stirred solution of the amino alcohol 36a (258 mg, 0.51 mmol)
and nicotinic acid (69 mg, 0.56 mmol) in DMF (2 mL) were
added EDC‚HCl (108 mg, 0.57 mmol) and then N-methylmor-
pholine (0.062 mL, 0.56 mmol) under Ar at 0 °C. After 10 min,
the reaction mixture was stirred at room temperature over-
night. Additional nicotinic acid (13 mg, 0.10 mmol) and EDC‚
HCl (20 mg, 0.10 mmol) were added. After stirring at room
temperature for another 3 h, the reaction mixture was poured
into 10% citric acid and extracted with EtOAc. The organic
layer was washed with saturated NaHCO3 and then brine,
dried over anhydrous Na2SO4 and concentrated in vacuo. The
residual solid was purified by silica gel column chromatogra-
phy [FL60D, CHCl3/MeOH, (100/1 f 20/1)] to afford the
alcohol 37a (260 mg, 89%) as a pale yellow amorphous
powder: TLC Rf ) 0.47 and 0.44, CHCl3/MeOH/AcOH (18/1/
d6) δ 10.12-9.89 and 9.42-9.14 (m × 2, 2H), 8.63 and 8.39 (d
× 2, J ) 10.0 Hz, 1H), 7.33-7.20 and 7.20-7.01 (m × 2, 4H),
5.05 and 4.73 (d × 2, J ) 3.9 Hz and J ) 10.2 Hz, 1H), 4.60-
3.94 (m, 4H), 3.26-3.12, 2.90-2.66 and 2.60-2.36 (m × 3, 2H),
2.34-2.18 and 1.90-1.72 (m × 2, 1H), 1.35 and 1.34 (s × 2,
9H), 1.03-0.93 (m, 6H).
Met h ylet h yl (3S)-3-{N-[(1S)-2-(5-ter t-Bu t yl-1,3,4-oxa -
d ia zol-2-yl)-2-h yd r oxy-1-(m eth yleth yl)eth yl]ca r ba m oyl}-
1,2,3,4-tetr a h yd r oisoqu in olin e-2-ca r boxyla te (30b). To a
stirred solution of the amino alcohol 29b (999 mg, 2.37 mmol)
in CH2Cl2 (20 mL) were added dropwise 1.0 M isopropyl
chloroformate in toluene (2.37 mL, 2.37 mmol) and N-meth-
ylmorpholine (0.520 mL, 4.73 mmol) at 0 °C. After 1 h, the
reaction mixture was stirred at room temperature for 3.5 h.
Additional 1.0 M isopropyl chloroformate in toluene (2.37 mL,
2.37 mmol) and N-methylmorpholine (0.520 mL, 4.73 mmol)
were added at 0 °C. The reaction mixture was stirred at room
temperature for another 3 h, then poured into ice-cooled 10%
citric acid and extracted with EtOAc. The organic layer was
washed with brine, with saturated NaHCO3, and again brine,
and dried over anhydrous Na2SO4. Concentration gave the
alcohol 30b (1.13 g) as a white amorphous powder quantita-
tively. The product was used for the next reaction without
further purification: TLC Rf ) 0.42 and 0.40, CHCl3/MeOH
1
1); MS (APCI, pos. 20 V) m/z ) 577 (M + H)+; H NMR (200
MHz, CDCl3) δ 9.10 and 8.96 (br s × 2, 1H), 8.84-8.65 (m,
1H), 8.28-7.94 (m, 2H), 7.50-6.97 (m, 6H), 5.64-5.38, 5.30-
4.76 and 4.60-3.94 (m × 3, 5H), 3.76-3.34 (m, 2H), 2.40-
1.60 (m, 2H), 1.38 and 1.18 (s × 2, 9H), 1.45-0.84, 0.70-0.63,
0.55-0.46 and 0.42-0.36 (m × 4, 12H).
(2S)-1-[(2S)-3-Meth yl-2-(3-pyr idin ecar bam ido)bu tan oyl]-
in d olin -2-yl-N-[(1S)-2-(5-ter t-bu tyl-1,3,4-oxa d ia zol-2-yl)-
1-(m eth yleth yl)-2-oxoeth yl]car boxam ide (24l). To a stirred
suspension of Dess-Martin periodinane (ca. 70%; 316 mg, 0.57
mmol) in CH2Cl2 (3 mL) was added a solution of the alcohol
37a (235 mg, 0.41 mmol) in CH2Cl2 (7 mL) under Ar at room
temperature. After 1 h, the reaction mixture was poured into
ice-cooled brine and extracted with EtOAc. The organic layer
was concentrated in vacuo. Purification by silica gel column
chromatography [FL60D, EtOAc/n-hexane (1/1 f 2/1)] afforded
the ketone 24l (200 mg, 85%) as a white amorphous powder:
TLC Rf ) 0.43, CHCl3/MeOH (9/1); MS (APCI, pos. 20 V) m/z
) 575 (M + H)+; IR (KBr) 3322, 2971, 2936, 2876, 1718, 1646,
1594, 1542, 1482, 1465, 1408, 1371, 1320, 1271, 1162, 1028,
1
(19/1); MS (APCI, pos. 40 V) m/z ) 473 (M + H)+; H NMR
(300 MHz, DMSO-d6) δ 7.66-7.47 (m, 1H), 7.26-6.98 (m, 4H),
6.23-6.05 (m, 1H), 4.95-4.05 and 3.90-3.60 (m × 2, 6H),
3.10-2.56 (m, 2H), 2.23-2.05 and 1.75-1.60 (m × 2, 1H),
1.37-1.05 (m, 15H), 0.95-0.60 (m, 6H).
Met h ylet h yl (3S)-3-{N-[(1S)-2-(5-ter t-Bu t yl-1,3,4-oxa -
diazol-2-yl)-1-(m eth yleth yl)-2-oxoeth yl]car bam oyl}-1,2,3,4-
tetr a h yd r oisoqu in olin e-2-ca r boxyla te (24i). To a stirred
suspension of Dess-Martin periodinane (ca. 70%; 1.16 g, 2.12
mmol) in CH2Cl2 (14 mL) was added a solution of the alcohol
30b (998 mg, 2.12 mmol) in CH2Cl2 (26 mL) under Ar at room
temperature. After 4 h, the reaction mixture was poured into
ice-cooled brine and extracted with EtOAc. The organic layer
was concentrated in vacuo. Purification of the residue by silica
gel column chromatography [Merck 7734, acetone/n-hexane
(1/9)] gave the ketone 24i (544 mg, 55% in 3 steps) as a
yellowish amorphous powder: TLC Rf ) 0.33, EtOAc/n-hexane
(1/2); MS (APCI, pos. 40 V) m/z ) 471 (M + H)+; IR (KBr)
3331, 2977, 2936, 2876, 1703, 1543, 1525, 1462, 1387, 1373,
949, 827, 707 cm-1 1H NMR (300 MHz, CDCl3) δ 9.06 and
;
8.96 (s × 2, 1H), 8.80-8.67 (m, 1H), 8.28-8.01 (m, 2H), 7.44-
7.02 and 6.86-6.77 (m × 2, 6H), 5.63-5.54, 5.44-5.29, 5.34-
5.04 and 4.76-4.66 (m × 4, 3H), 3.73-3.25 (m, 2H), 2.56-
2.14 (m, 2H), 1.47 and 1.36 (s × 2, 9H), 1.31-0.78 and 0.64-
0.54 (m × 2, 12H); optical rotation [R]25D -41.2 (c 0.4, MeCN).
Anal. (C31H38N6O5‚0.9H2O) C, H, N.
ter t-Bu tyl (3S)-3-{N-[(1S)-2-(5-ter t-Bu tyl-1,3,4-oxa d ia -
zol-2-yl)-2-h yd r oxy-1-(m et h ylet h yl)et h yl]ca r b a m oyl}-
1,2,3,4-tetr a h yd r oisoqu in olin e-2-ca r boxyla te (28b). To a
stirred mixture of (3S)-2-(tert-butoxycarbonyl)-1,2,3,4-tetra-
hydroisoquinoline-3-carboxylic acid (27b) (4.97 g, 1.79 mmol),
the amino alcohol 8e (5.67 g, 21.5 mmol) and HOBt‚H2O (3.29
g, 21.5 mmol) in DMF (55 mL), were added EDC‚HCl (4.12 g,
21.5 mmol) and then N-methylmorpholine (2.36 mL, 21.5
mmol) under Ar at 0 °C. After 15 min, the reaction mixture
was stirred at room temperature for 18 h, and poured into
water and extracted with EtOAc. The organic layer was
washed with 10% citric acid, saturated NaHCO3, water, and
then brine, dried over anhydrous Na2SO4, and concentrated
in vacuo. Purification of the residual pale yellow solid by silica
gel column chromatography [Merck 7734, EtOAc/n-hexane,
(1/1 f 4/1)] gave the Boc alcohol 28b (8.00 g, 92%) as a white
amorphous solid: TLC Rf ) 0.58 and 0.51, EtOAc/n-hexane
(4/1); MS (APCI, pos. 40 V) m/z ) 487 (M + H)+, 413, 387; 1H
NMR (200 MHz, CDCl3 + DMSO-d6) δ 7.17 (m, 4H), 6.95-
6.60 (m, 1H), 5.02-3.80 (m, 6H), 3.28-2.96 (m, 2H), 1.73 (m,
1H), 1.51, 1.43, 1.41 and 1.38 (s × 4, 18H), 0.95-0.40 (m, 6H).
1
1342, 1317, 1222, 1181, 1112, 1042, 1017, 915, 749 cm-1; H
NMR (300 MHz, DMSO-d6) δ 8.48-8.32 (m, 1H), 7.24-7.05
(m, 4H), 4.96-4.34 (m, 5H), 3.18-2.87 (m, 2H), 2.38-2.23 (m,
1H), 1.39 (s, 9H), 1.32-0.98 and 0.92-0.74 (m × 2, 12H);
optical rotation [R]24D -20.1 (c 1.0, MeCN). Anal. (C25H34N4O5‚
0.5H2O) C, H, N.
1-(Tr ip h en ylm eth yl)im id a zole-4-ca r boxylic Acid (32).
A mixture of imidazole-4-carboxylic acid (31) (2.24 g, 20.0
mmol) and triphenylmethyl chloride (6.13 g, 22.0 mmol) in
pyridine (30 mL) and DMF (60 mL) was stirred at room
temperature overnight, then quenched with water, and ex-
tracted with EtOAc. The organic layer was washed with water,
10% citric acid, and then brine, dried over anhydrous Na2SO4,
and concentrated in vacuo. The resulting solid was washed
with EtOAc to afford the carboxylic acid 32 (4.91 g, 70%) as a
1
white powder: TLC Rf ) 0.33, CHCl3/MeOH (9/1); H NMR
(200 MHz, CDCl3) δ 7.68-7.04 (m, 18H).
(3S)-2-[1-(Tr ip h en ylm eth yl)im id a zol-4-yl]ca r bon yl-3-
(1,2,3,4-t et r a h yd r oisoq u in olyl)-N-[(1S)-2-(5-ter t-b u t yl-
1,3,4-oxa d ia zol-2-yl)-2-h yd r oxy-1-(m eth yleth yl)eth yl]ca r -
boxa m id e (33b). To a stirred mixture of the carboxylic acid
32 (1.69 g, 4.77 mmol), the amino alcohol 29b (1.00 g, 2.37
mmol) and HOBt‚H2O (726 mg, 4.73 mmol) in DMF (20 mL),
were added EDC‚HCl (908 mg, 4.74 mmol) and then N-
methylmorpholine (0.522 mL, 4.74 mmol) under Ar at 0 °C.
The reaction mixture was stirred at room temperature for 24
h, and poured into saturated NaHCO3 and extracted with
EtOAc. The organic layer was washed with 10% citric acid,
and then brine, dried over anhydrous Na2SO4, and concen-
trated in vacuo. Purification of the residual pale yellow solid
by silica gel column chromatography (Merck 7734, EtOAc/CH2-
[(3S)-3-(1,2,3,4-Tet r a h yd r oisoq u in olyl)]-N-[(1S)-2-(5-
ter t-bu tyl-1,3,4-oxa d ia zol-2-yl)-2-h yd r oxy-1-(m eth yleth -
yl)eth yl]ca r boxa m id e Hyd r och lor id e (29b). A mixture of
the Boc alcohol 28b (6.00 g, 12.3 mmol) and 4 N HCl in dioxane
(40 mL) was stirred at room temperature for 1 h. The reaction
mixture was concentrated in vacuo. The residue was dried by
azeotropic removal of water with toluene to give the amino
alcohol 29b (5.35 g) as a white powder quantitatively. The
product was used for the next reaction without further
purification: TLC Rf ) 0.47, MeOH/CHCl3 (1/9); MS (APCI,
1
pos. 40 V) m/z ) 387 (M + H)+; H NMR (300 MHz, DMSO-

1284 J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 8
Ohmoto et al.
Cl2 (1/9 f 1/1) gave the alcohol 33b (1.04 g, 61%) as a white
amorphous powder: TLC Rf ) 0.48 and 0.42, CHCl3/MeOH
(9/1); 1H NMR (300 MHz, DMSO-d6) δ 7.81-7.00 (m, 22H),
6.22-5.85 (m, 2H), 5.02-3.75 (m, 4H), 3.20-2.77 (m, 2H),
2.30-1.95 and 1.80-1.40 (m, totally 1H), 1.33-1.13 (m, 9H),
0.92-0.40 (m, 6H).
reaction mixture followed by drying by azeotropic removal of
water with toluene gave the amino alcohol 36b (2.44 mmol)
quantitatively. The product was used for the next reaction
without further purification: MS (APCI, pos. 20 V) m/z ) 485
1
(M + H)+; H NMR (200 MHz, CDCl3) δ 8.50 (m, 3H), 7.60-
7.00 (m, 5H), 5.40-1.70 (m, 11H), 1.45-0.05 (m, 21H).
(3S)-2-{[1-(Tr ip h en ylm eth yl)im id a zol-4-yl]ca r bon yl}-
3-(1,2,3,4-tetr a h yd r oisoqu in olyl)-N-[(1S)-2-(5-ter t-bu tyl-
1,3,4-oxa d ia zol-2-yl)-1-(m eth yleth yl)-2-oxoeth yl]ca r box-
a m id e (34b ). To a stirred suspension of Dess-Martin
periodinane (ca. 70%; 751 mg, 1.36 mmol) in CH2Cl2 (9 mL)
was added a solution of the alcohol 33b (982 mg, 1.36 mmol)
in CH2Cl2 (18 mL) under Ar at room temperature. After 2 h,
the reaction mixture was poured into ice-cooled brine and
extracted with EtOAc. The organic layer was concentrated in
vacuo. Purification of the residue by silica gel column chro-
matography [FL60D, EtOAc/n-hexane (1/2)] gave the ketone
34b (485 mg, 50%) as a white amorphous powder: TLC Rf )
0.61, CHCl3/MeOH (19/1); 1H NMR (300 MHz, DMSO-d6) δ
8.56-8.45 (m, 1H), 7.63-7.31 and 7.31-7.04 (m × 2, 21H),
6.22-5.94 (m, 1H), 5.25-4.75 and 4.50-4.38 (m × 2, 3H),
3.50-2.90 (m, 2H), 2.40-2.18 (m, 1H), 1.45-1.30 (m, 9H),
1.00-0.60 (m, 6H).
(3S)-2-[(2S)-3-Meth yl-2-(3-pyr idin ecar bam ido)bu tan oyl]-
3-(1,2,3,4-tetr a h yd r oisoqu in olyl)-N-[(1S)-2-(5-ter t-bu tyl-
1,3,4-oxa d ia zol-2-yl)-2-h yd r oxy-1-(m eth yleth yl)eth yl]ca r -
boxa m id e (37b). To a stirred solution of the amino alcohol
36b (500 mg, 0.96 mmol), nicotinic acid (142 mg, 1.15 mmol),
and HOBt‚H2O (176 mg, 1.15 mmol) in DMF (3 mL), were
added EDC‚HCl (220 mg, 1.15 mmol) and then N-methylmor-
pholine (0.13 mL, 1.15 mmol) under Ar at 0 °C. After 10 min,
the reaction mixture was stirred at room temperature for 2.5
h, and quenched with N,N-dimethylpropylendiamine (0.03
mL). After 1 min, the resulting mixture was poured into water
and extracted with EtOAc. The organic layer was washed with
saturated NH4Cl, water, saturated NaHCO3, water, and then
brine, dried over anhydrous Na2SO4, and concentrated in
vacuo. The residual white amorphous solid was washed with
EtOAc/ether/n-hexane (1/4/36) under sonication, and collected
by filtration to give the alcohol 37b (498 mg, 88%) as a white
powder: TLC Rf ) 0.36, MeOH/CHCl3 (1/10); MS (APCI, pos.
40 V) m/z ) 591 (M + H)+; 1H NMR (200 MHz, CDCl3) δ 9.17-
8.90 (m, 1H), 8.71 (m, 1H), 8.20-7.91 (m, 1H), 7.70-7.00 (m,
7H), 5.47-2.88 (m, 9H), 2.36-1.80 (m, 2H), 1.47-0.19 (m,
21H).
(3S)-2-(Im id a zol-4-ylca r bon yl)-3-(1,2,3,4-tetr a h yd r oiso-
q u in olyl)-N-[(1S)-2-(5-ter t-b u t yl-1,3,4-oxa d ia zol-2-yl)-1-
(m eth yleth yl)-2-oxoeth yl]ca r boxa m id e Hyd r och lor id e
(24k ). A solution of the ketone 34b (433 mg, 0.602 mmol) in
trifluoroacetic acid/water (19/1; 4 mL) was stirred at room
temperature for 1 h. The reaction mixture was evaporated to
remove the solvent, then treated with 4 N HCl in EtOAc,
followed by concentration in vacuo. The resulting solid was
washed with ether and then EtOAc to afford the ketone 24k
(176 mg, 57%) as a white powder: TLC Rf ) 0.48, CHCl3/
MeOH (9/1); MS (APCI, pos. 20 V) m/z ) 479 (M + H)+; IR
(KBr) 3423, 3113, 2975, 2934, 2874, 1718, 1622, 1542, 1481,
1425, 1369, 1307, 1282, 1227, 1188, 1166, 1114, 1042, 1016,
(3S)-2-[(2S)-3-Meth yl-2-(3-pyr idin ecar bam ido)bu tan oyl]-
3-(1,2,3,4-tetr a h yd r oisoqu in olyl)-N-[(1S)-2-(5-ter t-bu tyl-
1,3,4-oxa d ia zol-2-yl)-1-(m eth yleth yl)-2-oxoeth yl]ca r box-
a m id e (24m ). To a stirred suspension of Dess-Martin
periodinane (ca. 77%; 492 mg, 0.89 mmol) in CH2Cl2 (6 mL)
was added a solution of the alcohol 37b (479 mg, 0.81 mmol)
in CH2Cl2 (12 mL) under Ar at room temperature. After 2.5
h, the reaction mixture was poured into water and extracted
with EtOAc. The organic layer was washed with water and
then brine, dried over anhydrous Na2SO4, and concentrated
in vacuo. Purification of the residual white paste by silica gel
column chromatography [FL60D, EtOAc/n-hexane (1/1 f 4/1)]
gave the ketone 24m (316 mg, 66%) as a white amorphous
powder: TLC (HPTLC) Rf ) 0.30, EtOAc; MS (APCI, pos. 20
V) m/z ) 589 (M + H)+; IR (KBr) 3427, 2971, 1716, 1638, 1592,
1001, 972, 952, 928, 822, 753, 693, 626 cm-1 1H NMR (200
;
MHz, CD3OD) δ 9.08 (br s, 1H), 8.31 (br s, 1H), 7.24 (m, 4H),
5.15-4.92 (m, 4H), 3.35-3.23 (m, 2H), 2.47-2.22 (m, 1H), 1.45
(s, 9H), 1.02-0.67 (m, 6H); optical rotation [R]25D -18.1 (c 0.4,
DMF). Anal. (C25H31ClN6O4‚0.8H2O) C, H, N.
(3S)-2-{(2S)-2-[(ter t-Bu t oxy)ca r b on yla m in o]-3-m et h -
ylbu ta n oyl}-3-(1,2,3,4-tetr a h yd r oisoqu in olyl)-N-[(1S)-2-
(5-ter t-b u t yl-1,3,4-oxa d ia zol-2-yl)-2-h yd r oxy-1-(m et h yl-
eth yl)eth yl]ca r boxa m id e (35b). To a stirred mixture of Boc-
L-valine (1.54 g, 7.10 mmol), the amino alcohol 29b (2.00 g,
4.73 mmol), and HOBt‚H2O (1.09 g, 7.10 mmol) in DMF (20
mL) were added EDC‚HCl (1.36 g, 7.10 mmol) and then
N-methylmorpholine (0.52 mL, 4.73 mmol) under Ar at 0 °C.
After 10 min, the reaction mixture was stirred at room
temperature for 24 h. Additional Boc-L-valine (1.54 g, 7.10
mmol), HOBt‚H2O (1.09 g, 7.10 mmol) and EDC‚HCl (1.36 g,
7.10 mmol) were added at 0 °C. After stirring at room
temperature for 24 h, Boc-L-valine (3.08 g, 14.2 mmol), HOBt‚
H2O (2.18 g, 14.2 mmol) and EDC‚HCl (2.72 g, 14.2 mmol) were
added again at 0 °C. After stirring at room temperature for
32 h, the reaction was quenched with N,N-dimethylpropylene-
diamine (3.00 mL, 24.0 mmol) at 0 °C. The reaction mixture
was poured into water and extracted with EtOAc. The organic
layer was washed with 5% KHSO4, water, and then brine,
dried over anhydrous MgSO4, and concentrated in vacuo.
Purification of the residual pale yellow solid by silica gel
column chromatography [FL60D, EtOAc/n-hexane, (1/9 f 2/1)]
gave the Boc alcohol 35b (1.52 g, 55%) as a white amorphous
solid: TLC Rf ) 0.39, MeOH/CHCl3 (1/10); MS (APCI, neg. 20
V) m/z ) 584 (M - H)-, 510; 1H NMR (200 MHz, CDCl3) δ
7.45-6.90 (m, 5H), 5.29-2.80 (m, 10H), 2.10-1.70 (m, 2H),
1.50-0.30 (m, 30H).
1541, 1419, 1369, 1221, 1158, 1027, 827, 745, 707 cm-1 1H
;
NMR (200 MHz, CDCl3) δ 9.09 and 8.99 (m × 2, 1H), 8.73 (m,
1H), 8.20-8.00 (m, 1H), 7.65 and 7.45-6.87 (m × 2, 7H), 5.40
(dd, J ) 8.2, 4.6 Hz, 1H), 5.27 (m, 1H), 5.16-4.96 and 4.86-
4.53 (m × 2, 3H), 3.65-3.00 (m, 2H), 2.54-2.11 (m, 2H), 1.47
and 1.37 (s × 2, 9H), 1.25-0.60 (m, 12H); optical rotation [R]25
D
-6.7 (c 1.0, MeCN). Anal. (C32H40N6O5‚0.4H2O) C, N, H.
N-[2-(5-ter t-Bu tyl-1,3,4-oxa d ia zol-2-yl)-1-(m eth yleth yl)-
2-o x o e t h y l]-2-{6-o x o -2-p h e n y l-5-[(p h e n y lm e t h o x y )-
car bam ido]h ydr opyr im idin yl}acetam ide (42). To a stirred
solution of oxalyl chloride (13.8 mL, 158 mmol) in CH2Cl2 (290
mL) was added dropwise a solution of DMSO (22.5 mL, 316
mmol) in CH2Cl2 (60 mL) under Ar at -70 to -60 °C. After
being stirred for 1 h, a solution of the alcohol 9e(H) (50.1 g,
ca. 79.2 mmol) in DMSO (30 mL) and CH2Cl2 (230 mL) was
added dropwise. After stirring at -70 °C for 2 h, the reaction
mixture was treated with triethylamine (221 mL, 1.60 mol),
then stirred at room temperature for 40 h. The reaction
mixture was acidified with 2 N HCl (600 mL) at 0 °C. The
organic layer was removed, and concentrated in vacuo. The
residue was dissolved in EtOAc. The organic layer was washed
with 1 N HCl, water, and then brine, dried over anhydrous
MgSO4, and concentrated in vacuo to afford the Cbz ketone
42 (47.6 g, quant). The product was used for the next reaction
without further purification: TLC Rf ) 0.36, n-hexane/EtOAc
(1/1); MS (APCI, pos. 40 V) m/z ) 587 (M + H)+; 1H NMR (200
MHz, CDCl3) δ 8.78 (br s, 1H), 7.67-7.24 (m, 11H), 6.74 (d, J
) 8.4 Hz, 1H), 5.44 (dd, J ) 8.4, 5.0 Hz, 1H), 5.23 (s, 2H), 4.68
and 4.58 (d × 2, J ) 15.4 Hz, 1H × 2), 2.63-2.39 (m, 1H),
1.47 (s, 9H), 1.06 and 0.87 (d × 2, J ) 6.8 Hz, 3H × 2).
(3S)-2-((2S)-2-Am in o-3-m eth ylbu ta n oyl)-3-(1,2,3,4-tet-
r a h yd r oisoqu in olyl)-N-[(1S)-2-(5-ter t-bu tyl-1,3,4-oxa d ia -
zol-2-yl)-2-h ydr oxy-1-(m eth yleth yl)eth yl]car boxam ide Hy-
d r och lor id e (36b). A mixture of the Boc alcohol 35b (1.42 g,
2.44 mmol), 4 N HCl in EtOAc (25 mL) and EtOAc (2 mL)
was stirred at room temperature for 1 h. Concentration of the
2-(5-Am in o-6-oxo-2-p h en ylh yd r op yr im id in yl)-N-[2-(5-

Orally Active Nonpeptidic Inhibitors of HNE
J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 8 1285
therein. (b) Skiles, J . W.; J eng, A. Y. Therapeutic promises of
leukocyte elastase and macrophage metalloelastase inhibitors
for the treatment of pulmonary emphysema. Exp. Opin. Ther.
Patents 1999, 9, 869-895 and the literature cited therein.
(12) Veale, C. A.; Bernstein, P. R.; Bohnert, C. M.; Brown, F. J .;
Bryant, C.; Damewood, J r., J . R.; Early, R.; Feeney, S. W.;
Edwards, P. D.; Gomes, B.; Hulsizer, J . M.; Kosmider, B. J .;
Krell, R. D.; Moore, G.; Salcedo, T. W.; Shaw, A.; Silberstein, D.
S.; Steelman, G. B.; Stein, M.; Strimpler, A.; Thomas, R. M.;
Vacek, E. P.; Williams, J . C.; Wolanin, D. J .; Woolson, S. Orally
Active Trifluoromethyl Ketone Inhibitors of Human Leukocyte
Elastase. J . Med. Chem. 1997, 40, 3173-3181.
-ter t-b u t yl-1,3,4-oxa d ia zol-2-yl)-1-(m et h ylet h yl)-2-oxo-
eth yl]a ceta m id e (3(H), ONO-6818). To a stirred solution of
the ketone 42 (47.6 g, ca. 79.2 mmol) and anisole (51.6 mL,
475 mmol) in CH2Cl2 (1.25 L) was added dropwise a solution
of aluminum chloride (63.0 g, 475 mmol) in CH3NO2 (630 mL)
under Ar at 0 °C. The reaction mixture was stirred at room
temperature for 2.5 h, then quenched with crushed ice, and
extracted with CH2Cl2. The organic layer was washed with
water and with brine, dried over anhydrous Na2SO4, and
concentrated in vacuo. Purification of the residue by silica gel
column chromatography [Merck 7734, MeOH/CHCl3 (0/100 f
1/19)] followed by washing with CH2Cl2 gave the ketone 3(H)
(ONO-6818) (26.0 g, 73% in 3 steps) as an off-white powder:
TLC Rf ) 0.49, CHCl3/MeOH (10/1); MS (APCI, pos. 40 V) m/z
) 453 (M + H)+; IR (KBr) 3466, 2976, 1695, 1641, 1611, 1543,
(13) See ref 14 of the following literature: Edwards, P. D.; Meyer,
E. F., J r.; Vijayalakshmi, J .; Tuthill, P. A.; Andisik, D. A.; Gomes,
B.; Strimpler, A. Design, Synthesis, and Kinetic Evaluation of
a Unique Class of Elastase Inhibitors, the Peptidyl R-Keto-
benzoxazoles, and the X-ray Crystal Structure of the Covalent
Complex between Porcine Pancreatic Elastase and Ac-Ala-Pro-
Val-2-Benzoxazole. J . Am. Chem. Soc. 1992, 114, 1854-1863.
(14) Edwards, P. D.; Wolanin, D. J .; Andisik, D. W.; Davis, M. W.
Peptidyl R-Ketoheterocyclic Inhibitors of Human Neutrophil
Elastase. 2. Effect of Varying the Heterocyclic Ring on in Vitro
Potency. J . Med. Chem. 1995, 38, 76-85.
1439, 1303, 1205, 979, 703, 546 cm-1 1H NMR (200 MHz,
;
CDCl3) δ 7.58-7.38 (m, 6H), 6.88 (br d, J ) 8.4 Hz, 1H), 5.45
(dd, 1H, J ) 8.4, 5.0 Hz), 4.66 and 4.60 (d × 2, J ) 15.4 Hz,
1H × 2), 4.06 (m, 2H), 2.52 (m, 1H), 1.48 (s, 9H), 1.07 and
0.88 (d × 2, J ) 6.8 Hz, 3H × 2). Anal. (C23H28N6O4) C, H, N.
(15) Gyorkos, A.; Spruce, L. W. Serine Protease Inhibitors. WO 98/
24806.
Su p p or tin g In for m a tion Ava ila ble: Elemental analyti-
cal data. This material is available free of charge via the
Internet at http://pubs.acs.org.
(16) Most of the synthetic inhibitors of HNE reported to date consist
of lipophilic building blocks because of their good affinity to the
lipophilic active site of HNE, while too much lipophilicity has
been one of the reasons for the difficulty in developing an orally
active synthetic inhibitor. Hydrophilic heteroaromatics such as
1,2,4-oxadiazoles and 1,3,4-oxadiazoles were predicted to im-
prove the physicochemical properties of the inhibitors because
of their presumed hydrophilic properties and the potent in vitro
activity of 1a ,b.
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(18) More data is being submitted to Bioorg. Med. Chem. for
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Williams, J . C.; Wolanin, D. J .; Woolson, S. Nonpeptidic Inhibi-
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(21) Deprotection was conducted with 35% HBr/AcOH with respect
to 10m (F ).
(22) Nakao, A.; Partis, R. A..; J ung, G. P..; Mueller, R. A. SC-39026,
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Ceccarelli, C.; Damewood, J r. J . R.; Edwards, P. D.; Earley, R.
A.; Feeney, S.; Green, R. C.; Gomes, B.; Kosmider, B. J .; Krell,
R. D.; Shaw, A.; Steelman, G. B.; Thomas, R. M.; Vacek, E. P.;
Veale, C. A.; Tuthill, P. A.; Warner, P.; Williams, J . C.; Wolanin,
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(24) R-Isomer 11n (H) was prepared from Boc-D-valinal by the same
procedure as described for the preparation of 11e(H).
(25) Oral dosing of 3(H) was carried out using CMC as a vehicle.
(26) Marsters, J . C., J r.; Brown, M. S.; Crowley, C. W.; Goldstein, J .
L.; J ames, G. L.; McDowell, R. S.; Oare, D.; Rawson, T. E.;
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U.S. Patent 5,843,941.
inflammatory bowel disease:
a marker of disease activity?
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(10) (a) Edwards, P. D.; Bernstein, P. R. Synthetic Inhibitors of
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Leukocyte Elastase. Prog. Med. Chem. 1994, 31, 59-120.
(11) For a comprehensive review of synthetic HNE inhibitors, see:
(a) Metz, W. A.; Peet, N. P. Inhibitors of human neutrophil
elastase as a potential treatment for inflammatory diseases. Exp.
Opin. Ther. Patents 1999, 9, 851-868 and the literature cited
J M000410Y