Dual metalloprotease inhibitors: Mercaptoacetyl-based fused heterocyclic dipeptide mimetics as inhibitors of angiotensin-converting enzyme and neutral endopeptidase

Article abstract of DOI:10.1021/jm970041e

A series of 7,6- and 7,5-fused bicyclic thiazepinones and oxazepinones were generated and incorporated as conformationally restricted dipeptide surrogates in mercaptoacyl dipeptides. These compounds are potent inhibitors of angiotensin-converting enzyme (

Full text of DOI:10.1021/jm970041e

1570
J . Med. Chem. 1997, 40, 1570-1577
Du a l Meta llop r otea se In h ibitor s: Mer ca p toa cetyl-Ba sed F u sed Heter ocyclic
Dip ep tid e Mim etics a s In h ibitor s of An gioten sin -Con ver tin g En zym e a n d
Neu tr a l En d op ep tid a se
J effrey A. Robl,* Chong-Qing Sun, J ay Stevenson, Denis E. Ryono, Ligaya M. Simpkins, Maria P. Cimarusti,
Tamara Dejneka, William A. Slusarchyk, Sam Chao, Leslie Stratton, Raj N. Misra, Mark S. Bednarz,
Magdi M. Asaad, Hong Son Cheung, Benoni E. Abboa-Offei, Patricia L. Smith, Parker D. Mathers, Maxine Fox,
Thomas R. Schaeffer, Andrea A. Seymour, and Nick C. Trippodo
The Bristol-Myers Squibb Pharmaceutical Research Institute, P.O. Box 4000, Princeton, New J ersey 08543-4000
Received J anuary 12, 1997X
A series of 7,6- and 7,5-fused bicyclic thiazepinones and oxazepinones were generated and
incorporated as conformationally restricted dipeptide surrogates in mercaptoacyl dipeptides.
These compounds are potent inhibitors of angiotensin-converting enzyme (ACE) and neutral
endopeptidase (NEP) both in vitro and in vivo. Compound 1a , a 7,6-fused bicyclic thiazepinone,
demonstrated excellent blood pressure lowering in a variety of animal models characterized
by various levels of plasma renin activity and significantly potentiated urinary sodium, ANP,
and cGMP excretion in a cynomolgus monkey assay. On the basis of its potency and duration
of action, compound 1a (BMS-186716) was advanced into clinical development for the treatment
of hypertension and congestive heart failure.
In tr od u ction
Angiotensin-converting enzyme (ACE), a zinc-con-
taining carboxydipeptidase, catalyzes the conversion of
the decapeptide angiotensin I (AI) to the octapeptide
angiotensin II (AII). AII is a potent vasoconstrictor
which also triggers the release of aldosterone, a sodium-
retaining steroid. Thus ACE raises blood pressure by
increasing both vascular resistance and fluid volume.
Effective inhibitors of ACE have found widespread use
not only in the treatment of hypertension but in the
clinical management of congestive heart failure.1 Neu-
tral endopeptidase (NEP), like ACE, is a zinc metallo-
protease and is found in high concentration in the brush
border of the renal proximal tubule. NEP is highly
efficient in degrading atrial natriuretic peptide (ANP),
F igu r e 1.
a 28-amino acid peptide secreted by the heart in
acids in the dipeptide fragment or by incorporating
response to atrial distention. ANP has opposing hor-
conformationally restricted dipeptide mimetics for the
monal actions to those of AII. By interaction with its
dipeptide.6 BMS-182657 was an early prototype of this
receptor, ANP promotes the generation of cGMP via
latter class and has been shown to potently inhibit both
guanylate cyclase activation, thus resulting in vasodi-
ACE and NEP in vitro and in vivo.7 Despite its
encouraging activity, this compound was not developed
primarily based on its relatively moderate duration of
latation, natriuresis, diuresis, and inhibition of aldos-
terone.2
The renin angiotensin system and the natriuretic
peptide system have opposing actions on vascular
resistance, sodium and water excretion, and aldosterone
production. Therefore simultaneous potentiation of
ANP via NEP inhibition and attenuation of AII via ACE
inhibition should lead to complimentary effects in the
management of hypertension and congestive heart
failure.3 Moreover, combining ACE inhibition with NEP
inhibition would likely negate the complication of AII
potentiation encountered with selective NEP inhibition.4
On the basis of this rationale, our efforts have concen-
trated on the utilization of mercaptoacyl dipeptides
related to the early lead SQ-26332 (Figure 1) as dual
inhibitors of ACE and NEP.5 We and others have
demonstrated that potent dual inhibitors can be gener-
ated either by incorporation of nonendogenous amino
activity in animal models of hypertension. Further
extension of this work has led to a series of bicyclic
lactams characterized generically by structure 1. In this
report we describe the synthesis of a novel 7,6-fused
bicyclic thiazepinone 1a (BMS-186716) and its phar-
macological evaluation both in vitro and in vivo.
Ch em istr y
The retrosynthesis of 1a is depicted in Scheme 1.
Bicyclic thiazepinones of the type 2 were previously
unknown, and we envisioned that construction of the
bicyclic ring system was possible via intramolecular
N-acyliminium ion cyclization of intermediate 3. Indeed
we and others have demonstrated that formation of
related 7,6(5)-fused ring systems can occur when the
attacking nucleophile is an alcohol,8 olefin,9 phenyl,6d
or heterocyclic10 moiety. Iminium ion 3, generated in
situ via acid-catalyzed cyclization of dipeptide 4, would
X Abstract published in Advance ACS Abstracts, May 1, 1997.
S0022-2623(97)00041-1 CCC: $14.00 © 1997 American Chemical Society

Dual Metalloprotease Inhibitor
J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 11 1571
Sch em e 1
Sch em e 2a
a
Reagents: (a) Cbz-OSu, NaHCO3, H2O, acetone, 97%; (b) KOH, H2O, then excess Ac2O, 85%; (c) resolve via (S)-R-methylbenzylamine,
41% of theory; (d) Br(CH2)4OAc, NaH, DMF, 98%; (e) (i) NaOH, H2O, (ii) H3O+, ∆, (iii) porcine kidney acylase, 66% of theory overall; (f)
HCl, MeOH; (g) WSC, HOBT, 4-methylmorpholine, DMF, CH2Cl2, 88% (two steps); (h) Swern oxidation, 86%; (i) NaOMe, MeOH, rt, 10
min; (j) cat. TFA, CH2Cl2, ∆, 72% (two steps); (k) TMSI, CH2Cl2, 92%; (l) (S)-AcSCH(CH2Ph)CO2H, BOP reagent, TEA, CH2Cl2, 69%; (m)
NaOH, H2O, MeOH, then H3O+, 83%.
be derived from the protected L-homocysteine and
L-hydroxynorleucine fragments 5 and 6, respectively.
and subsequent TFA-induced cyclization afforded bicy-
clic lactam 15 in good yield and high (>99%) diastere-
omeric purity.13 The stereoconfiguration was confirmed
by NOE and ultimately single-crystal X-ray analysis of
1a . Removal of the Cbz protecting group afforded the
amine 16 which was coupled to (S)-2-(acetylthio)-3-
benzenepropanoic acid14 and deprotected to give 1a . A
variant of this methodology was also used to prepare
the corresponding 7,5- and 6,6-fused bicyclics in both
the oxygen and sulfur series.15
Commercially available racemic homocysteine thio-
lactone (7) was protected to give 8 (Scheme 2) and
subsequently saponified and acetylated in situ to give
racemic 9 (as the free acid) in high yield.11 Resolution
of the acid via the (S)-R-methylbenzylamine salt crystal-
lized from MeOH/EtOAc afforded 9 in >98% ee and 41%
of theoretical yield. Literature methods12 for the gen-
eration of the requisite L-hydroxynorleucine (11) were
inefficient, lengthy, and problematic to run on a large
scale and thus necessitated development of an alternate
route to this nonendogenous amino acid. Sodium hy-
dride-induced alkylation of diethyl acetamidomalonate
with 4-bromobutyl acetate afforded 10. In a subsequent
one-pot transformation, the adduct was saponified,
decarboxylated, and enzymatically resolved to give
L-hydroxynorleucine 11. Coupling of the methyl ester
12 with the free acid of 9 provided dipeptide 13. Swern
oxidation to give 14, followed by deprotection of the thiol
Discu ssion
Table 1 lists in vitro data and AI pressor responses
(intravenous administration in rats) for compounds 1a -
g. In vitro, all of the fused bicyclic mimetic-based
inhibitors demonstrated superior activity against both
ACE and NEP as compared to their parent Ala-Pro-
based counterpart SQ-263325 (ACE I50 ) 30 nM, NEP
I50 ) 400 nM), validating the concept of conformational
restriction in this series. Essentially all of the com-

1572 J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 11
Robl et al.
Ta ble 1. Inhibition of ACE and NEP in Vitro and AI Pressor Responses for Compounds 1a -g
% inhibition of AI pressor response at
various time points (min) after 0.5 µmol/kg
I50 (nM)
NEPb ACEc
iv administration
d
AI pressor ED50
(µmol/kg, iv)
no.
X
n
m
fusion
formulaa
C19H24N2O4S2
max.e
30
60
120
1a
1b
1c
1d
1e
S
S
S
1
1
0
1
1
1
1
1
0
1
1
0
1
0
7,6
7,5
6,6
7,6
7,5
7,6
7,5
8
4
42
9
26
25
18
5
4
5
8
7
0.07
0.03
0.23
0.05
0.06
0.12
0.06
76 ( 4
82 ( 6
78 ( 3
83 ( 4
79 ( 6
71 ( 4
75 ( 4
66 ( 9
76 ( 7
3 ( 5
60 ( 16
60 ( 5
ndg
58 ( 12
25 ( 6
nd
nd
nd
f
C
C
C
C
18H22N2O4S2
18H22N2O4S2‚0.12EtOAc
19H24N2O5S‚0.12EtOAc
18H22N2O5S‚0.85H2O
O
O
3 ( 3
nd
63 ( 5
65 ( 5
34 ( 4
3 ( 2
35 ( 6
3 ( 10
1f CH2
1g CH2
C20H26N2O4S‚0.45H2Oh
11
5
11 ( 5
nd
C19H24N2O4S
a
All spectral data were consistent with the assigned structures. All compounds were analyzed for C, H, N, and S for the formula
b
shown. Compounds were assayed against purified rat kidney neutral endopeptidase using a fluorometric assay with dansyl-Gly-Phe-
Arg as the substrate. c Compounds were assayed against angiotensin-converting enzyme isolated from rabbit lung extract using hippuryl-
d
L-histidyl-L-leucine (HHL) as the substrate. Represents dose required for 50% inhibition of the AI pressor response in normotensive
rats. e Maximal response in assay usually 2 min after administration of compound. f Anal. (C18H22N2O4S2) C, H, N; S: calcd, 16.25; found,
g
h
15.80. Not determined at this time point. Anal. (C20H26N2O4S‚0.45H2O) C, H, S; N: calcd, 7.03; found, 6.57.
F igu r e 2. Inhibition of the MAP response to angiotensin I (AI, iv administration) in conscious rats (A) and cynomolgus monkeys
(B) after oral (po) administration of fosinopril or compound 1a was determined according to procedures previously described.7
Conscious animals (n ) 4 per group), instrumented with implanted arterial and venous catheters at least 2 weeks prior to study,
were prepared for direct recording of aterial blood pressure using a pressure transducer. Changes in MAP in response to iv
injections of AI (310 ng/kg) were obtained before (control) and at intervals after the administration of vehicle, fosinopril, or compound
1a . The percent change (mean ( SE) from the control response (% inhibition) was determined for each response after drug or
vehicle administration.
pounds potently inhibited ACE in vitro and robustly
inhibited the acute pressor responses to AI in the rat,
although there were some variations with respect to
potency against NEP in vitro. The 6,6-fused thiazine
1c was substantially less potent versus NEP in vitro
and ACE in vivo than its 7,6- or 7,5-fused analogs,
suggesting that incorporation of a seven-membered
azepinone ring in the mimetic is critical for optimal
activity. A similar observation was made when com-
paring azepinone-based inhibitors with their corre-
sponding eight-membered azocinone derivatives.16 Dif-
ferentiation among compounds was also made by
comparing duration of activity in the AI pressor assay
at a comparative dose of 0.5 µmol/kg, iv. Despite their
high maximal responses in this assay, compounds 1c,
1d , 1e, and 1g were short-acting, failing to display
significant activity 60 min postdosing. The duration of
activity was especially short with 1c and 1d , in which
response levels returned to baseline within 30 min. In
contrast, the 7,6(5)-fused thiazepinones 1a and 1b
effected significant changes in the pressor response 120
min posttreatment at this dose. Upon oral administra-
tion to rats and monkeys in the AI pressor assay (Figure
2), 1a effected a response comparable both in magnitude
and duration of activity to that of the clinically effica-
cious, once-a-day, selective ACE inhibitor fosinopril.17
On the basis of its excellent potency against NEP and
ACE in vitro and its superior duration of activity in the
AI pressor assay, compound 1a was selected for exten-
sive evaluation in vivo.
ACE inhibitors have historically demonstrated de-
pressor effects in the sodium-deplete spontaneously
hypertensive rat (sd-SHR) whereas selective NEP in-
hibitors have generally been shown to be ineffective in
this assay.18 At a single oral dose (30 µmol/kg, ∼12 mg/
kg), 1a decreased mean arterial pressure (MAP) ap-
proximately 40 mmHg below baseline from 10 to 24 h,
whereas fosinopril averaged a 20 mmHg decrease dur-

Dual Metalloprotease Inhibitor
J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 11 1573
F igu r e 4. Effect on blood pressure upon oral administration
(qd) of vehicle (5% NaHCO3, n ) 5), fosinopril (n ) 9), or
compound 1a (n ) 9) in the 1K-DOCA salt rat assay. At day
0, systolic blood pressure was measured indirectly by the tail-
cuff method after conditioning rats to the procedure for three
consecutive days prior. Dosing was initiated on day 1. At days
1, 2, and 3, systolic blood pressure was measured indirectly 4
h after each dose. At day 4, mean arterial pressure was
measured directly from indwelling catheters 24 h after the last
dose. *p < 0.05 vs vehicle.
F igu r e 3. Changes in MAP in conscious sodium-depleted
spontaneously hypertensive rats (sd-SHR) after oral admin-
istration of vehicle (5% NaHCO3, n ) 10), fosinopril (n ) 7),
or compound 1a (n ) 7). Mean arterial pressures before
administration of agents were (mean ( SE): 146 ( 3, 150 (
7, and 148 (5 mmHg in the vehicle, fosinopril, and compound
1a groups, respectively. For fosinopril, p < 0.05 vs vehicle for
hours 2-24. For compound 1a , p < 0.05 vs vehicle for hours
1-24. For compound 1a , p < 0.05 vs fosinopril (*).
Conformationally restricted mercaptoacyl dipeptide
1a has been demonstrated to be a potent inhibitor of
both ACE and NEP in vitro and was shown to be an
effective antihypertensive agent in models characterized
by various levels of plasma renin activity. Additional
antihypertensive, hemodynamic, and renal pharmacol-
ogy studies on 1a will be presented in future reports as
well as animal studies demonstrating the potential of
this compound in the treatment of congestive heart
failure. Based in part on these studies, compound 1a
(BMS-186716) was selected for further clinical develop-
ment. The compound is currently in phase II clinical
trials for the treatment of hypertension and congestive
heart failure.
ing this same period (Figure 3). Thus, as an ACE
inhibitor, 1a was at least as effective as fosinopril at
30 µmol/kg, po, with regard to magnitude and duration
of lowering MAP in this model of high renin hyperten-
sion. In vivo inhibition of NEP for 1a was demonstrated
in the 1-kidney DOCA salt rat hypertension assay.
Selective NEP inhibitors have been shown to lower MAP
in this low renin model of hypertension, whereas selec-
tive ACE inhibitors (i.e. fosinopril) are usually ineffec-
tive. Oral administration of 1a at 100 µmol/kg once
daily resulted in a 38 mmHg decrease in systolic blood
pressure at day three as compared to vehicle (Figure
4). No significant difference versus vehicle was ob-
served with fosinopril. Again, the duration of the
observed antihypertensive effect with 1a was robust; at
day four MAP, as measured directly from indwelling
catheters, was 36 mmHg lower than that in the vehicle
group 24 h postdosing.
Exp er im en ta l Section
All reactions were carried out under a static atmosphere of
argon and stirred magnetically unless otherwise noted. All
reagents used were of commercial quality and were obtained
from Aldrich Chemical Co. or Sigma Chemical Co. Melting
points were obtained on a Hoover Uni-melt melting point
apparatus and are uncorrected. Infrared spectra were re-
corded on a Mattson Sirius 100-FTIR spectrophotometer. 1H
(400 Mz) and 13C (100 Mz) NMR spectra were recorded on a
J EOL GSX400 spectrometer using Me4Si as an internal
standard. Optical rotations were measured in a 1-dm cell on
a Perkin-Elmer 241 polarimeter, and c is expressed in g/100
mL. All flash chromatographic separations were performed
using E. Merck silica gel (60, particle size, 0.040-0.063 mm).
Reactions were monitored by TLC using 0.25 mm E. Merck
silica gel plates (60 F254) and were visualized with UV light or
5% phosphomolybdic acid in 95% EtOH.
N-(Ca r boben zyloxy)-D,L-h om ocystein e th iola cton e (8).
To a 4 L flask equipped with a large magnetic stirring bar
was added 750 mL of H2O followed by DL-homocysteine
thiolactone hydrochloride (7) (362.07 g, 2.36 mol). After most
of the salt had dissolved, complete dissolution was achieved
by the addition of 750 mL of acetone. To the resulting solution
was added N-((benzyloxycarbonyl)oxy)succinimide (Cbz-OSu,
587.38 g, 2.36 mol) as a solid. The resulting heterogenous
mixture was carefully treated with solid NaHCO3 (201.93 g,
2.40 mol) added portionwise over a period of 5 min, loosely
covered, and stirred at ambient temperature for 20 h. The
reaction mixture was then diluted with H2O to a volume of 4
L, and the precipitate was collected by filtration and rinsed
three times with 1 L of H2O. Drying in vacuo at 35 °C for 16
h afforded compound 8 (578.6 g, 97%) as a white solid: TLC
The potent response in both the AI pressor assay and
the sd-SHR indicated that compound 1a is an effective
ACE inhibitor with good duration of action. In order
to better assess the NEP inhibitory component on renal
parameters, 1a was administered to cynomolgus mon-
keys infused with saline and 30 ng/min of AII and
subsequently challenged with a bolus dose of human-
ANP. The constant infusion of AII masked the effect
of ACE inhibition by suppressing renin release and
replacing angiotensin II so that a clearer measure of in
vivo inhibition of NEP would be obtained.19 As antici-
pated, 0.1-3 µmol/kg doses of 1a potentiated urinary
sodium, urinary ANP, and urinary cGMP excretion
(Figure 5). The responses were dose related except for
ANP since the time course of the experiment did not
allow ANP levels to return to baseline and thus the full
ANP response to the drug was not obtained. In a
subsequent study in cynomolgus monkeys (manuscript
in preparation), daily oral administration of 1a at 50
µmol/kg for four days potentiated the urinary ANP
response to exogenous human-ANP. The results are
consistent with the oral activity of 1a in the DOCA-salt
hypertensive rats.

1574 J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 11
Robl et al.
F igu r e 5. Natriuretic, cGMP, and ANP excretory responses to 0.3 nmol/kg ANP in conscious, sodium-loaded monkeys infused
with 30 ng/min angiotensin II and treated with compound 1a or vehicle (0.84% NaHCO3) by iv administration. The dose-response
relationships on the peak change in urinary sodium excretion (A), cumulative changes in urinary cGMP excretions (B), and
cumulative changes in urinary ANP excretions (C) following ANP challenge.
Rf 0.55 (6:4 EtOAc:hexane); mp 109-111 °C; 1H NMR (CDCl3)
δ 1.97 (m, 1H), 2.71 (m, 1H), 3.14 (m, 1H), 3.21 (m, 1H), 4.30
(m, 1H), 5.08 (s, 2H), 5.58 (s, 1H), 7.31 (m, 5H); 13C NMR
(CDCl3) δ 204.86, 156.03, 135.88, 128.32, 128.00, 127.86, 66.93,
60.45, 31.27, 26.88. Anal. Calcd for C12H13NO3S: C, 57.35;
H, 5.21; N, 5.57; S, 12.76. Found: C, 57.41; H, 5.10; N, 5.51;
S, 12.67.
enantiomeric purity of 82.3% by chiral HPLC analysis. A
portion of this salt (23 g) was suspended in a mixture of EtOAc:
MeOH (3:1, 120 mL) and stirred for 3 h. The solid was
collected by filtration, washed with cold EtOAc (25 mL), and
dried in vacuo to give 9 (13 g) with an enantiomeric purity of
98.7% by chiral HPLC analysis. Repeating the above proce-
dure with EtOAc:MeOH (3:1, 60 mL) afforded the salt (11 g)
with an enantiomeric purity of 99.5%: [R]D +2.6° (c 1.0, EtOH);
S -Ace t yl-N -[(p h e n ylm e t h oxy)ca r b on yl]-L-h om ocys-
tein e, S-(-)-r-Meth ylben zyla m in e Sa lt (9). A solution of
compound 8 (750 g, 3.02 mol) in THF (3.75 L) and H2O (1.2 L)
was degassed three times (vacuum/nitrogen purges). A solu-
tion of KOH (88%, 577 g, 9.05 moles) in H2O (1.5 L), degassed
as above, was added to the thiolactone solution. After the
solution was stirred at room temperature for 1.5 h, acetic
anhydride (1623 g, 15.9 mol) was then added over 1.75 h with
continued cooling (ice bath), maintaining a temperature of <27
°C. After an additional 30 min at room temperature, the
reaction was acidified with 1 L of 6 N aqueous HCl (final pH
) 4.32) and then concentrated in vacuo, collecting ∼3.5 L of
distillate. The concentrate was acidified further with ad-
ditional 6 N aqueous HCl (400 mL) to a pH of 2.6. The product
was extracted with EtOAc (2 × 2.5 L). The combined organic
extracts were washed three times with saturated brine, dried
(Na2SO4), filtered, and concentrated under vacuum to afford
a tacky white solid. The residue was azeotroped three times
with toluene (2 L portions) to remove residual acetic acid. The
solid slurry was collected by filtration using ∼500 mL hexane/
EtOAc to transfer and dried under vacuum at 40 °C for 16 h
to afford racemic 9 (free acid form, 799 g, 85%) as a white
solid: TLC Rf 0.48 (2:98 HOAc:EtOAc).
1
mp 117-119 °C dec; H NMR (CD3OD) δ 1.59 (d, J ) 7 Hz,
3H), 1.88 (m, 1H), 2.05 (m, 1H), 2.26 (s, 3H), 2.89 (m, 2H),
4.06 (m, 1H), 4.42 (q, J ) 7 Hz, 1H), 5.06 (dd, 2H), 7.26-7.46
(m, 10H); 13C NMR (CD3OD) δ 197.22, 178.25, 158.08, 140.03,
138.25, 130.13, 129.89, 129.40, 128.88, 128.72, 127.62, 67.39,
56.95, 52.15, 34.24, 30.48, 26.63, 20.93. Anal. Calcd for
C22H28N2O5S: C, 60.84; H, 6.54; N, 6.45; S, 7.38. Found: C,
60.82; H, 6.39; N, 6.25; S, 7.37. Partitioning the salt between
EtOAc and 10% aqueous KHSO4 afforded the free acid of 9 in
quantitative yield as an oil which solidified on standing: [R]D
1
) -1.3° (c 1.0, 95% EtOH); mp 73-74 °C; H NMR (CD3OD)
δ 1.94 (m, 1H), 2.08 (m, 1H), 2.28 (s, 3H), 2.86-3.00 (m, 2H),
4.25 (m, 1H), 5.08 (s, 2H), 7.27-7.36 (m, 5H); 13C NMR (CD3-
OD) δ 197.07, 175.11, 158.57, 138.07, 129.41, 128.94, 128.73,
67.64, 54.23, 32.69, 30.47, 26.43. Anal. Calcd for C14H17
-
NO5S: C, 54.01; H, 5.50; N, 4.50; S, 10.30. Found: C, 53.97;
H, 5.45; N, 4.36; S, 10.40.
2-(Acet yla m in o)-2-[4-(a cet yloxy)b u t yl]p r op a n ed ioic
Acid , Dieth yl Ester (10). A stirred suspension of 95% sodium
hydride (60.8 g, 2.532 mol) in anhydrous DMF (500 mL) under
an atmosphere of argon was cooled to 0 °C (ice bath).
A
solution of diethyl acetamidomalonate (500 g, 2.302 mol) in
anhydrous DMF (1.2 L) was added over a period of 45 min
while keeping the reaction temperature below 18 °C. After
the addition was complete, the turbid solution was gradually
warmed to room temperature. After 1 h of stirring at room
temperature, 4-bromobutyl acetate (471.5 g, 2.417 mol) was
added. The mixture was then stirred at 59-60 °C for 18 h.
The resulting slurry was cooled to room temperature, quenched
with absolute EtOH (40 mL) and glacial acetic acid (4 mL),
stirred for about 15 min, poured into a 10% LiCl solution, and
To a solution of racemic free acid of 9 (1243 g, 3.99 mol) in
EtOAc (5.0 L) was added (S)-(-)-R-methylbenzylamine (459.7
g, 3.8 mol, Lancaster Synthesis) dropwise maintaining a
temperature e26 °C with cooling (ice bath) over 1.5 h. The
mixture was seeded with 98% enantiomerically pure 9 and
stirred at room temperature for 4 h. The precipitate was
collected by filtration and dried for 24 h at room temperature
to give enantiomerically enriched 9 (595 g, 72.5% of theory,
36.3% from racemic free acid) as a white solid with an

Dual Metalloprotease Inhibitor
J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 11 1575
extracted with EtOAc (2 × 3 L). The combined EtOAc extracts
were washed with 10% LiCl (3 × 3 L), dried (Na2SO4), and
evaporated in vacuo to give compound 10 (750 g, 98%) as an
oil: TLC Rf 0.19 (1:1 EtOAc:hexane); 1H NMR (CDCl3) δ 1.95
(m, 2H), 2.05 (t, J ) 7.1 Hz, 6H), 1.63 (tt, J ) 7.0 and 7.0 Hz,
2H), 2.03 (s, 3H), 2.04 (s, 3H), 2.38 (m, 2H), 4.03 (t, J ) 6.5
Hz, 2H), 4.25 (q, J ) 7.0 Hz, 4H), 6.83 (s, 1H); 13C NMR
(CDCl3) δ 170.86, 168.89, 167.87, 66.25, 63.89, 62.36, 31.63,
28.09, 22.86, 20.76, 20.08, 13.81; IR (film) 2926, 1740, 1680,
at 0 °C for 30 min and then a solution of 12 in DMF (50 mL)
was added, followed by dropwise addition of 4-methylmorpho-
line (6.05 mL, 0.055 mol). The resulting suspension was
stirred at room temperature for 20 h. The reaction mixture
was partitioned between EtOAc (500 mL) and 5% aqueous
KHSO4 (100 mL). The separated organic layer was washed
with 5% aqueous KHSO4 (100 mL), saturated aqueous NaH-
CO3 (2 × 100 mL), H2O (2 × 200 mL), and brine (200 mL),
dried over Na2SO4, and filtered. The filtrate was concentrated
in vacuo, and the residue was flash chromatographed on a
short silica gel column (4:1 EtOAc:hexanes as eluent) to afford
dipeptide 13 (18.56 g, 88%) as a colorless oil which solidified
on standing: [R]D -6.5° (c 1.0, CH2Cl2); mp 87-88 °C; TLC Rf
0.25 (4:1 EtOAC:hexane); 1H NMR (CDCl3) δ 1.42 (m, 2H), 1.55
(m, 2H), 1.73 (m, 1H), 1.91 (m, 2H), 2.10 (m, 2H), 2.34 (s, 3H),
2.87 (m, 1H), 3.06 (m, 1H), 3.60 (m, 2H), 3.73 (s, 3H), 4.22 (m,
1H), 4.56 (m, 1H), 5.10 (s, 2H), 5.71 (d, J ) 7.7 Hz, 1H), 7.16
(d, J ) 7.2 Hz, 1H), 7.34 (m, 5H); 13C NMR (CDCl3) δ 196.61,
172.57, 171.16, 156.24, 136.16, 128.51, 128.16, 128.00, 67.08,
62.00, 53.77, 52.40, 52.35, 33.04, 31.86, 31.51, 30.58, 25.25,
21.60; IR (KBr) 3518, 3296, 2934, 1740, 1695, 1647, 1531, 1263,
1064, 633 cm-1; MS (ESI) (M + H)+ 455. Anal. Calcd for
C21H30N2O7S: C, 55.49; H, 6.65; N, 6.16; S, 7.05. Found: C,
55.22; H, 6.54; N, 5.97; S, 6.98.
1507, 1370, 1248, 1198 cm-1
.
(S)-2-Am in o-6-h yd r oxyh exa n oic Acid (11). To a solution
of compound 10 (730 g, 2.2 mol) in a 5 L 3-neck flask (equipped
with a thermometer, magnetic stirrer, and air-cooled con-
denser) in absolute EtOH (300 mL) was added aqueous 6 N
sodium hydroxide (1.6 L, 9.6 mol). The reaction mixture was
heated at 68-70 °C for 5 h to afford a homogeneous solution.
The reaction was cooled to room temperature, and 6 N HCl
(1.32 L) was added slowly to adjust the pH to 1.3. The flask
was equipped with a short path distillation head, and the
EtOH was distilled off as the temperature was slowly in-
creased to 87-90 °C and maintained at this temperature for
8.5 h. Slow carbon dioxide evolution was observed. The total
volume of distillate was 600 mL. The reaction mixture was
stripped and then concentrated from toluene (2 × 500 mL) to
give a semisolid mass. The solid was triturated with absolute
EtOH (1 L), filtered, and rinsed with additional absolute EtOH
(500 mL). The filtrate was concentrated in vacuo to yield 509
g of the crude intermediate (82% purity) which contained
EtOH and toluene.
[S-(R*,R*)]-2-[[4-(Acetylth io)-1-oxo-2-[[(ph en ylm eth oxy)-
car bon yl]am in o]bu tyl]am in o]-6-oxoh exan oic Acid, Meth -
yl Ester (14). To a solution of oxalyl chloride (4.17 mL, 0.048
mol) in CH2Cl2 (75 mL) cooled at -78 °C was added dropwise
anhydrous methyl sulfoxide (DMSO, 6.78 mL, 0.096 mol). The
mixture was stirred for 20 min and then treated with a
solution of 13 (15.50 g, 0.034 mol) in CH2Cl2 (50 mL) via
cannula. The resulting white suspension was stirred at -78
°C for 1 h, and then triethylamine (21 mL, 0.15 mol) was
added. After being stirred at -78 °C for 15 min, the reaction
mixture was slowly warmed to room temperature and then
partitioned between EtOAc (500 mL) and 5% aqueous KHSO4
(100 mL). The organic layer was washed with 5% aqueous
KHSO4 (100 mL), saturated aqueous NaHCO3 (100 mL), H2O
(2 × 200 mL), and brine (200 mL), then dried over MgSO4,
and filtered. The filtrate was concentrated in vacuo, and the
residue was flash chromatographed (40-60% EtOAc:hexanes
as eluent) to afford aldehyde 14 (13.18 g, 86%) as a white
solid: [R]D -6.8° (c 1.2, CH2Cl2); mp 74-75 °C; TLC Rf 0.49
(4:1 EtOAC:hexane); 1H NMR (CDCl3) δ 1.67 (m, 3H), 1.90 (m,
2H), 2.11 (m, 1H), 2.35 (s, 3H), 2.47 (t, J ) 6.4 Hz, 2H), 2.85
(m, 1H), 3.10 (m, 1H), 3.75 (s, 3H), 4.20 (m, 1H), 4.57 (m, 1H),
5.12 (s, 2H), 5.58 (d, J ) 7.7 Hz, 1H), 7.08 (d, J ) 7.7 Hz, 1H),
7.34 (m, 5H), 9.73 (s, 1H); 13C NMR (CDCl3) δ 201.57, 196.35,
172.12, 170.91, 155.98, 136.10, 128.39, 128.03, 127.88, 66.92,
53.60, 52.36, 51.88, 42.85, 32.94, 31.17, 30.44, 25.10, 17.69;
IR (KBr) 3302, 2928, 1751, 1696, 1649, 1539, 1262, 1215, 1128
cm-1; MS (ESI) (M + H)+ 453. Anal. Calcd for C21H28N2O7S:
C, 55.74; H, 6.24; N, 6.19; S, 7.08. Found: C, 55.66; H, 6.11;
N, 6.08; S, 7.12.
The residue product (443 g of crude product) was dissolved
in H2O (3.3 L), and 1 N lithium hydroxide was added until
the pH was 7.5 (1.53 L required). The mixture was heated to
35 °C, porcine kidney acylase I (0.4 g, Sigma) was added, and
the reaction mixture was stirred for 24 h. The pH was
readjusted to 7.5 with 1 N lithium hydroxide (about 2 mL),
additional acylase (0.4 g) was added, and the reaction mixture
was stirred for an additional 17 h. The pH of the solution was
adjusted to 5.9 with acetic acid. Celite (20 g) and charcoal
(20 g) were added, and the reaction mixture was heated to 92
°C and maintained at this temperature for 5 min. The reaction
was filtered through a pad of Celite and concentrated in vacuo
to a paste (441 g) which was triturated with 900 mL of 1:5:10
H2O:EtOH:DMF. The slurry was refrigerated overnight,
filtered, and washed with 200 mL of the above solvent mixture
to yield 214 g of crude product. This material was suspended
in MeOH (500 mL), warmed on a steam bath, allowed to stand
for 2 h, and filtered. Repeat treatment of the solid afforded
after drying compound 11 (108 g, 33% chemical yield, 66%
theoretical) as a white powder: TLC Rf 0.62 (MeOH:H2O:
1
HOAc, 10:1:1); [R]D ) +22° (c 1.44, 6 N HCl); H NMR (D2O)
δ 1.27 (m, 2H), 1.43 (tt, J ) 7.0 and 7.0 Hz, 2H), 1.72 (m, 2H),
3.45 (t, J ) 6.3 Hz, 2H), 3.58 (t, J ) 6.0 Hz, 1H); 13C NMR
(D2O) δ 175.85, 62.24, 55.74, 31.92, 31.20, 21.85; IR (KBr) 3418,
2945, 1605, 1582, 1518, 1408, 1354 cm-1; MS (CI) 148 (M +
H)+. Anal. Calcd for C6H13NO3: C, 48.25; H, 8.94; N, 9.38.
Found: C, 48.66; H, 8.77; N, 9.43.
[4S-(4r,7r,10a â)]-Octa h yd r o-4-[[(p h en ylm eth oxy)ca r -
b on yl]a m in o]-5-oxo-7H -p yr id o[2,1-b][1,3]t h ia zep in e-7-
ca r boxylic Acid , Meth yl Ester (15). A solution of 14 (11.845
g, 0.026 mol) in MeOH (110 mL) cooled to 0 °C (ice bath) was
purged with argon for 20 min. Sodium methoxide (25% wt/
wt in MeOH, 6.00 mL, 0.026 mol) was added rapidly with
continual argon purging, and the reaction mixture was stirred
for an additional 10 min and then quenched with saturated
aqueous ammonium chloride (160 mL). The resulting suspen-
sion was partitioned between EtOAc (200 mL) and H2O (100
mL). The layers were separated, and the aqueous layer was
extracted with EtOAc (3 × 100 mL). The combined EtOAc
extracts were washed with saturated aqueous ammonium
chloride (100 mL), H2O, and brine, then dried over MgSO4,
and filtered. The filtrate was concentrated in vacuo, and the
oily residue was azeotroped twice with toluene/CH2Cl2, dried
in vacuo, and used immediately in the next reaction without
further purification: 1H NMR (CDCl3) δ 1.60 (m, 3H), 1.80-
2.15 (m, 4H), 2.45 (m, 2H), 2.60 (m, 2H), 3.74 (s, 3H), 4.47 (m,
1H), 4.56 (m, 1H), 5.10 (s, 2H), 5.67 (d, J ) 7.9 Hz, 1H), 6.88
(d, J ) 7.2 Hz, 1H), 7.32 (m, 5H), 9.71 (s, 1H).
[S-(R*,R*)]-2-[[4-(Acetylth io)-1-oxo-2-[[(ph en ylm eth oxy)-
ca r bon yl]a m in o]bu tyl]a m in o]-6-h yd r oxyh exa n oic Acid ,
Meth yl Ester (13). A stream of hydrogen chloride gas was
bubbled into a suspension of 11 (7.35 g, 0.05 mol) in MeOH
(150 mL) cooled at 0 °C (ice bath) for 15 min. The resulting
solution was refluxed for 3.5 h. After being cooled to room
temperature, the reaction mixture was concentrated in vacuo,
and the obtained oily residue was azeotroped with toluene (3
× 50 mL) and dried in vacuo to give ester 12 (HCl salt) (10 g,
100%) as a colorless syrup, which was used in the following
reaction without further purification: TLC Rf 0.33 (2:1:1:1
EtOAc:n-BuOH:AcOH:H2O); 1H NMR (DMSO-d6) δ 1.25-1.50
(m, 4H), 1.80 (m, 2H), 3.38 (t, J ) 6.0 Hz, 2H), 3.75 (s, 3H),
3.98 (m, 1H), 4.63 (br s, 1H), 8.65 (br s, 3H); MS (ESI) (M +
H)+ 162.
To a solution of the free acid of 9 (14.40 g, 0.046 mol) in
CH2Cl2 (100 mL) at 0 °C (ice bath) was added 1-hydroxyben-
zotrizole hydrate (HOBt, 6.756 g, 0.05 mol), followed by 1-[3-
(dimethylamino)propyl]-3-ethylcarbodiimide hydrochloride
(WSC, 8.90 g, 0.046 mol). The resulting suspension was stirred

1576 J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 11
Robl et al.
To a solution of the above thiol in CH2Cl2 (200 mL) was
added dropwise trifluoroacetic acid (2.0 mL, 0.026 mol), and
the mixture was refluxed under argon for 16 h. The resulting
slightly turbid solution was concentrated in vacuo, diluted with
EtOAc (300 mL), and washed successively with saturated
aqueous NaHCO3, H2O, and brine, then dried over MgSO4, and
filtered. The filtrate was concentrated in vacuo, and the
resulting light brown oil was flash chromatographed (25-30%
EtOAc:hexanes as eluent) to give diastereomerically pure
bicyclic thiazepinone 15 (7.38 g, 72%) as a white foam: [R]D
10aâ]]-octahydro-4-[[2-(acetylthio)-1-oxo-3-phenylpropyl]amino]-
5-oxo-7H-pyrido[2,1-b][1,3]thiazepine-7-carboxylic acid, methyl
ester (123.57 g, 69%) as an oil: TLC Rf 0.37 (1:1 EtOAc:
hexanes); 1H NMR (CDCl3) δ 1.59-1.72 (m, 3H), 1.85-2.04
(m, 3H), 2.21 (m, 1H), 2.33 (s, 3H), 2.42 (m, 1H), 2.89 (m, 1H),
3.00 (dd, 1H), 3.24-3.33 (m, 2H), 3.71 (s, 3H), 4.3 (t, 1H, J )
7.7 Hz), 4.95 (m, 1H), 5.18 (m, 1H), 5.28 (m, 1H), 7.20-7.29
(m, 5H), 7.49 (d, 1H, J ) 6.5 Hz); 13C NMR (CDCl3) δ 195.00,
173.18, 169.73, 138.14, 129.82, 129.07, 127.51, 59.55, 52.87,
52.06, 51.63, 48.81, 37.44, 32.92, 31.82, 31.73, 31.04, 25.43,
17.71.
1
-93.1° (c 1.0, CH2Cl2); TLC Rf 0.40 (1:1 EtOAC:hexanes); H
NMR (CDCl3) δ 1.67 (m, 3H), 2.03 (m, 3H), 2.33 (m, 1H), 2.44
(m, 1H), 2.95 (m, 1H), 3.26 (m, 1H), 3.72 (s, 3H), 4.86 (m, 1H),
5.11 (m, 2H), 5.21 (d, J ) 4.8 Hz, 1H), 5.30 (m, 1H), 6.22 (d, J
) 6.5 Hz, 1H), 7.32 (m, 5H); 13C NMR (CDCl3) δ 172.80, 171.29,
155.38, 136.34, 128.42, 128.01, 127.85, 66.68, 58.86, 52.67,
52.13, 50.89, 33.08, 31.07, 24.69, 16.96; IR (CH2Cl2) 3403, 3327,
To a 12 L three-necked flask, fitted with an additional
funnel and mechanical stirrer, was added a solution of the
ester (96.0 g, 0.207 mol) in MeOH (1.1 L). The solution was
purged with argon for 30 min and then cooled in an ice bath
until the internal temperature was 7 °C. A 1 N NaOH solution
(1.45 L, previously sparged with argon for 30 min) was added
over 1 h. The reaction mixture was continuously purged with
argon during the addition. The reaction temperature rose to
12 °C and was maintained during the addition. After stirring
for an additional 30 min, the mixture was warmed to room
temperature, and stirred for 2.5 h. Approximately 250 mL of
6 N HCl was added dropwise over a 15-20 min period to adjust
the pH to 2. A gummy precipitate formed during acidification.
After the mixture was continually stirred for an additional 2
h, the precipitate changed to a fine white solid with some
larger chunks of solid product present. The product was
collected by filtration and washed with 1 L of H2O followed by
2 L of anhydrous Et2O and dried in vacuo to afford 1a (70.3 g,
83%) as a fine white solid: TLC Rf 0.48 (5:95 AcOH:(1:1 EtOAc:
hexanes)); [R]D -78.9° (c 0.46, DMF); mp 218-220 °C dec; 1H
NMR (DMSO-d6) δ 1.45-1.63 (m, 3H), 1.80- 2.00 (m, 3H), 2.10
(m, 1H), 2.40 (m, 1H), 2.74 (d, J ) 9.0 Hz, 1H), 2.80 (dd, 1H),
2.94 (m, 1H), 3.10 (m, 1H), 3.19 (dd, 1H), 3.82 (q, 1H), 4.90
(m, 1H), 5.05 (m, 1H), 5.64 (m, 1H), 7.17-7.29 (m, 5H), 8.30
(d, J ) 6.8 Hz, 1H), 12.55 (brs, 1H); 13C NMR (DMSO-d6) δ
172.1, 170.8, 138.6, 129.0, 128.0, 126.2, 57.1, 50.6, 50.4, 42.1,
40.8, 31.5, 30.6, 29.3, 24.7, 16.6; IR (KBr) 3437, 2942, 2562,
1744, 1653, 1630, 1516, 1416, 1186, 1140, 750, 702 cm-1. Anal.
Calcd for C19H24N2O4S2: C, 55.86; H, 5.92; N, 6.86; S, 15.70.
Found: C, 55.87; H, 5.90; N, 6.94; S, 15.80.
2949, 1724, 1657, 1497, 1433, 1414, 1209, 1053, 1001 cm-1
MS (ESI) (M
H)+ 393 Anal. Calcd for C19H24N2-
;
+
O5S.0.15H2O: C, 57.75; H, 6.20; N, 7.09; S, 8.11. Found: C,
57.76; H, 6.39; N, 7.04; S, 8.26.
[4S-(4r,7r,10a â)]-Octa h yd r o-4-a m in o-5-oxo-7H-p yr id o-
[2,1-b][1,3]t h ia zep in e-7-ca r b oxylic Acid , Met h yl E st er
(16). Iodotrimethylsilane (76.6 mL, 0.538 mol) was added to
a solution of compound 15 (162.43 g, 0.414 mol) in CH2Cl2 (1.5
L) at room temperature. After 1.5 h of stirring, the reaction
mixture was concentrated in vacuo and the residue was
partitioned between 1 L of EtOAc and 700 mL of 1 N HCl.
The EtOAc layer was separated and extracted with 300 mL
of 1 N HCl. The combined acidic aqueous extracts were
washed with additional EtOAc (1 L), then cooled to 0 °C, and
basified with 4 N sodium hydroxide (about 275 mL) to pH 10.
The aqueous layer was saturated with solid NaCl and then
extracted with five 1 L portions of CH2Cl2. The combined
organic extracts were dried (Na2SO4), filtered, and concen-
trated in vacuo. The residue was redissolved in 1 L of CH2-
Cl2, washed with 0.5 L of brine, dried (Na2SO4), filtered, and
concentrated to give pure amine 16 (98.8 g, 92%) as a yellow
1
oil: TLC Rf 0.31 (10:90 MeOH: CH2Cl2); H NMR (CDCl3) δ
1.59-1.72 (m, 3H), 1.83 (br s, 2H), 1.89-2.01 (m, 3H), 2.20-
2.25 (m, 1H), 2.35-2.46 (m, 1H), 3.00-3.06 (m, 2H), 3.72 (s,
3H), 4.05 (dd, 1H), 5.20 (m, 1H), 5.34 (m, 1H); 13C NMR
(CDCl3) δ 176.92, 172.74, 57.68, 52.84, 52.09, 51.05, 35.07,
30.78, 30.55, 24.99, 16.93.
Ack n ow led gm en t. We gratefully acknowledge Dr.
Donald S. Karanewsky, Dr. Edward W. Petrillo, and Dr.
J ames Powell for their contributions to this project. We
are also grateful for the contributions of J erry Baumann
and Richard Knappenberger to this work.
[4S-[4r(R*),7r,10a â]]-Octa h yd r o-4-[(2-m er ca p to-1-oxo-
3-p h e n y lp r o p y l)a m in o ]-5-o x o -7H -p y r id o [2,1-b ][1,3]-
th ia zep in e-7-ca r boxylic Acid (1a ). (S)-2-(Acetylthio)ben-
zenepropanoic acid, dicyclohexylamine salt14,15 (173.1 g, 0.427
mol) was partitioned between EtOAc (1 L) and 10% potassium
bisulfate (800 mL). The organic layer was separated, washed
with 5% potassium bisulfate (1 L), 50% brine (1 L), and brine
(1 L), dried (Na2SO4), filtered, and concentrated in vacuo. The
residue was azeotroped several times with CH2Cl2 and then
dried overnight in vacuo to yield 97.3 g of crude (S)-2-
(acetylthio)benzenepropanoic acid.
The acid (0.427 mol) in CH2Cl2 (900 mL) was chilled (ice
bath) and treated sequentially with a solution of amine 16
(100.28 g, 0.388 mol) in CH2Cl2 (600 mL), neat triethylamine
(154.1 mL, 0.388 mol), and solid (benzotriazol-1-yloxy)tris-
(dimethylamino)phosphonium hexafluorophosphate (BOP re-
agent, 188.9 g, 0.427 mol). After 1 h at 0 °C and 2 h at room
temperature, the reaction mixture was concentrated in vacuo
and dissolved in 2 L of EtOAc. The solution was again
concentrated in vacuo and dissolved in 2 L of EtOAc. The
EtOAc solution was washed successively with brine (0.5 L),
0.5 N aqueous HCl (1 L), H2O (1 L), saturated NaHCO3 (2 L),
H2O (1 L), and brine (1 L), dried (Na2SO4), filtered, and
concentrated. Those aqueous rinses which contained product
(TLC indication) were reextracted with EtOAc. These extracts
were worked up in the usual manner, and all EtOAc extracts
were combined and stripped to give a yellow oily residue. The
oil was applied to a 15 × 15 cm silica gel pad prepared in 1:1
EtOAc:hexanes and eluted with 7 L of 1:1 EtOAc:hexanes
followed by 4 L of 6:4 EtOAc:hexanes and finally 2 L of 7:3
EtOAc:hexanes. The filtrates containing the desired product
were concentrated to give the coupling product [4S-[4R(R*),7R,-
Refer en ces
(1) (a) Lawton, G.; Paciorek, P. M.; Waterfall, J . F. The design and
biological properties of ACE inhibitors. Advances in Drug
Research; Academic Press Limited: New York, 1992; Vol. 23,
pp 161-221. (b) Salvetti, A. Newer ACE inhibitors: A look at
the future. Drugs 1990, 40, 800-828.
(2) (a) Roques, B. P.; Noble, F.; Dauge, V.; Fournie-Zaluski, M-C.;
Beaumont, A. Neutral endopeptidase 24.11: Structure, inhibi-
tion, and experimental and clinical pharmacology. Pharmacol.
Rev. 1993, 45, 87-146. (b) Wilkins, M. R.; Unwin, R. J .; Kenny,
A. J . Endopeptidae-24.11 and its inhibitors: Potential thera-
peutic agents for edematous disorders and hypertension. Kidney
Int. 1993, 43, 273-285. (c) Lang, C. C.; Choy, A-M. J .; Struthers,
A. D. Atrial and brain natriuretic peptides: A dual natriuretic
peptide system potentially involved in circulatory homeostasis.
Clin. Sci. 1992, 83, 519-527. (d) Lang, R. E.; Unger, T.; Ganten,
D. Atrial natriuretic peptide: A new factor in blood pressure
control. J . Hyperten. 1987, 5, 255-271.
(3) (a) Margulies, K. B.; Perrella, M. A.; McKinley, L. J .; Burnett,
J . Angiotensin inhibition potentiates the renal response to
neutral endopeptidase inhibition in dogs with congestive heart
failure. J . Clin. Invest. 1991, 88, 1636-1642. (b) Seymour, A.
A.; Swerdel, J . N.; Abboa-Offei, B. Antihypertensive activity
during inhibition of neutral endopeptidase and angiotensin
converting enzyme. J . Cardiovasc. Pharm. 1991, 17, 456-465.
(c) Seymour, A. A.; Swerdel, J . N.; Abboa-Offei, B. E. Antihy-
pertensive activity during inhibition of neutral endopeptidase
and angiotensin converting enzyme. J . Cardiovasc. Pharmacol.
1991, 17, 456-465. (d) Seymour, A. A.; Asaad, M. M.; Lanoce,
V. M.; Langenbacher, K. M.; Fennell, S. A.; Rogers, W. L.
Systemic hemodynamics, renal function and hormonal levels
during inhibition of neutral endopeptidase 3.4.24.11 and angio-

Dual Metalloprotease Inhibitor
J ournal of Medicinal Chemistry, 1997, Vol. 40, No. 11 1577
tensin-converting enzyme in conscious dogs with pacing-induced
heart failure. J . Pharmacol. Exp. Ther. 1993, 266, 872-883. (e)
Trippodo, N. C.; Fox, M.; Natarajan, V.; Panchal, B. C.; Dorso,
C. R.; Asaad, M. M. Combined inhibition of neutral endopepti-
dase and angiotensin converting enzyme in cardiomyopathic
hamsters with compensated heart failure. J . Pharmacol. Exp.
Ther. 1993, 267, 108-116. (f) Pham, I.; Gonzalez, W.; El Amrani,
A.-I. K.; Fournie-Zaluski, M.-C.; Philippe, M.; Laboulandine, I.;
Roques, B. P.; Michel, J .-B. Effects of converting enzyme
inhibitor and neutral endopeptidase inhibitor on blood pressure
and renal function in experimental hypertension. J . Pharmacol.
Exp. Ther. 1993, 265, 1339-1347. (g) Seymour, A. A.; Asaad,
M. M.; Smith, P. L.; Abboa-Offei, B. E.; Rogers, W. L.; Dorso, C.
R. Effects of fosinoprilat or an angiotensin II (A II) antagonist
on a neutral endopeptidase (NEP) inhibition in conscious renal
hypertensive dogs. FASEB J . 1994, 8, A551. (h) Trippodo, N.
C.; Panchal, B. C.; Fox, M. Repression of angiotensin II and
potentiation of bradykinin contribute to the synergistic effects
of dual metalloprotease inhibition in heart failure. J . Pharmacol.
Exper. Ther. 1995, 272, 1-9.
Marshall, G. R. Electrochemical cyclization of dipeptides toward
novel bicyclic, reverse-turn peptidomimetics. 1. Synthesis and
conformational analysis of 7,5-bicyclic systems. J . Am. Chem.
Soc. 1995, 117, 909-917. (c) Reference 15.
(9) Robl, J . R. Peptidomimetic synthesis: Utilization of N-acylimin-
ium ion cyclization chemistry in the generation of 7,6- and 7,5-
fused bicyclic lactams. Tetrahedron Lett. 1994, 35, 393-396.
(10) Robl, J . A. Compounds containing a fused multiple ring lactam.
European patent application EP657453A.
(11) Saponification of homochiral N-Cbz-L-homocysteine thiolactone
under various conditions resulted in the formation of racemic 9
due to rapid epimerization of the chiral center. Thus the more
readily available and less costly racemic homocysteine thiolac-
tone was utilized in this procedure.
(12) (a) Belyaev, A. A. A novel synthetic route to enantiomers of
ꢀ-hydroxynorleucine and ꢀ-chloronorleucine from L and D,L-
lysine. Tetrahedron Lett. 1995, 36, 439-440. (b) Baldwin, J . E.;
Killin, S. J .; Adlington, R. M.; Spiegel, U. Synthesis of N-ben-
zyloxycarbonyl-L-R-aminoadipic acid, R-benzyl ester. Tetrahe-
dron 1988, 44, 2633-2636. (c) Maurer, P. J .; Miller, M. J .
Microbial iron chelators: Total synthesis of areobactin and its
constituent amino acid, N6-acetyl-N6-hydroxylysine. J . Am.
Chem. Soc. 1982, 104, 3096.
(13) We have also demonstrated that the corresponding dimethyl
acetal of aldehyde 14, dipeptide 18, undergoes conversion to 15
in similar yield and diastereoselectivity (see scheme below).
Compound 18 was prepared by coupling acetal 17 with the free
acid of 9. Full experimental details may be found in the patent
cited in ref 15.
(4) (a) Richards, A. M.; Wittert, G. A.; Espiner, E. A.; Yandle, T.
G.; Ikram, H.; Frampton, C. Effect of inhibition of endopeptidase
24.11 on responses to angiotensin II in human volunteers. Circ.
Res. 1992, 71, 1501-1507. (b) O’Connell, J . E.; J ardine, A. G.;
Davies, D. L.; McQueen, J .; Connell, J . M. C. Renal and
hormonal effects of chronic inhibition of neutral endopeptidase
(EC 3.4.24.11) in normal man. Clin. Sci. 1993, 85, 19-26. (c)
Richards, A. M.; Wittert, G. A.; Crozier, I. G.; Espiner, E. A.;
Yandle, T. G.; Ikram, H.; Frampton, C. Chronic inhibition of
endopeptidase 24.11 in essential hypertension: evidence for
enhanced atrial natriuretic peptide and angiotensin II. J .
Hypertension 1993, 11, 407-416.
(5) Robl, J . A.; Simpkins, L. M.; Stevenson, J .; Sun, C. Q.; Murug-
esan, N.; Barrish, J . C.; Asaad, M. M.; Bird, J . E.; Schaeffer, T.
R.; Trippodo, N. R.; Petrillo, E. W.; Karanewsky, D. S. Dual
metalloprotease inhibitors. I. Constrained peptidomimetics of
mercaptoacyl dipeptides. BioorgMed. Chem. Lett. 1994, 4, 1789-
1794.
(6) For a representative set of leading references on mercaptoacyl
dipeptides and dipeptide mimetics, see: (a) Robl, J . A.; Cima-
rusti, M. P.; Simpkins, L. M.; Brown, B. B.; Ryono, D. E.; Bird,
J . E.; Asaad, M. M.; Schaeffer, T. R.; Trippodo, N. C. Dual
metalloprotease inhibitors 6. Incorporation of bicyclic and
substituted monocyclic azepinones as dipeptide surrogates in
angiotensin-converting enzyme/neutral endopeptidase inhibitors.
J . Med. Chem. 1996, 39, 494-502 and references therin. (b)
Fink, C. A.; Carlson, J . E.; McTaggart, P. A.; Qiao, Y.; Webb,
R.; Chatelain, R.; J eng, A. Y.; Trapani, A. J . Mercaptoacyl
dipeptides as orally active dual inhibitors of angiotensin-
converting enzyme and neutral endopeptidase. J . Med. Chem.
1996, 39, 3158-3168 and references therin. (c) Fournie-Zaluski,
M.-C.; Coric, P.; Thery, V.; Gonzalez, W.; Meudal, H.; Turcaud,
S.; Michel, J .-B.; Roques, B. P. Design of orally active dual
inhibitors of neutral endopeptidase and angiotensin-converting
enzyme with long duration of action. J . Med. Chem. 1996, 39,
2594-2608 and references therein. (d) Flynn, G. A.; Beight, D.
W.; Mehdi, S.; Koehl, J . R.; Giroux, E. L.; French, J . F.; Hake,
P. W.; Dage, R. C. Application of a conformationally restricted
Phe-Leu dipeptide mimetic to the design of a combined inhibitor
of angiotensin I-converting enzyme and neutral endopeptidase
24.11. J . Med. Chem. 1993, 36, 2420-2423.
(7) Trippodo, N. C.; Robl, J . A.; Asaad, M. M.; Bird, J . E.; Panchal,
B. C.; Schaeffer, T. R.; Fox, M.; Giancarli, M. R.; Cheung, H. S.
Cardiovascular effects of the novel dual inhibitor of neutral
endopeptidase and angiotensin converting enzyme BMS-182657
in experimental hypertension and heart failure. J . Pharmacol.
Exp. Ther. 1995, 275, 745-752.
(8) (a) Baldwin, J . E.; Hulme, C.; Schofield, J .; Edwards, A. J .
Synthesis of potential â-turn bicyclic dipeptide mimetics. J .
Chem. Soc., Chem. Commun. 1993, 935-936. (b) Cornille, F.;
Slomczynska, U.; Smythe, M. L.; Beusen, D. D.; Moeller, K. D.;
(14) Strijtveen, B.; Kellogg, R. M. Synthesis of (racemization prone)
optically active thiols by SN2 substitution using cesium thiocar-
boxylates. J . Org. Chem. 1986, 51, 3664-3671.
(15) Experimental details outlining the synthesis of compounds 1a -e
have been reported: Robl, J . R. US Patent 5,508,272, April 16,
1996. Compounds 1f and 1g were previously disclosed in an
earlier report (ref 6a).
(16) Krapcho, J .; Turk, C.; Cushman, D. W.; Powell, J . R.; DeForrest,
J . M.; Spitzmiller, E. R.; Karanewsky, D. S.; Duggan, M.;
Rovnyak, G.; Schwartz, J .; Natarajan, S.; Godfrey, J . D.; Ryono,
D. E.; Neubeck, R.; Atwal, K. S.; Petrillo, E. W. Angiotensin-
converting enzyme inhibitors. Mercaptan, carboxyalkyl dipep-
tide, and phosphinic acid inhibitors incorporating 4-substituted
prolines. J . Med. Chem. 1988, 31, 1148-1160.
(17) Robl, J . A.; Simpkins, L. M.; Sulsky, R.; Sieber-McMaster, E.;
Stevenson, J .; Kelly, Y. F.; Sun, C. Q.; Misra, R. N.; Ryono, D.;
Asaad, M. M.; Bird, J . E.; Trippodo, N. C.; Karanewsky, D. S.
Dual metalloprotease inhibitors. II. Effect of substitution and
stereochemistry on benzazepinone based mercaptoacetyls. Bioorg.
Med. Chem. Lett. 1994, 4, 1795-1800.
(18) A full description of the in vitro assays and the AI pressor, the
1K-DOCA salt rat, and sd-SHR assays can be found in ref 7.
(19) Seymour, A. A.; Asaad, M. M.; Abboa-Offei, B. E.; Smith, P. L.;
Mathers, P. D.; Rogers, W. L.; Dorso, C. R. Renal and depressor
activities of inhibitors of neutral endopeptidase and angiotensin
converting enzyme in monkeys infused with angiotensin II. J .
Cardiovasc. Pharmacol. 1996, 28, 397-401.
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