AMP deaminase inhibitors. 5. Design, synthesis, and SAR of a highly potent inhibitor series

Article abstract of DOI:10.1021/jm000355t

A highly potent AMP deaminase (AMPDA) inhibitor series was discovered by replacing the N3 substitutents of the two lead AMPDA inhibitor series with a conformationally restricted group. The most potent compound, 3-[2-(3-carboxy-4-bromo-5,6,7,8-tetrahydrona

Full text of DOI:10.1021/jm000355t

J . Med. Chem. 2001, 44, 613-618
613
AMP Dea m in a se In h ibitor s. 5. Design , Syn th esis, a n d SAR of a High ly P oten t
In h ibitor Ser ies
Srinivas Rao Kasibhatla,* Brett C. Bookser, Wei Xiao, and Mark D. Erion
Metabasis Therapeutics Inc., 9390 Towne Centre Drive, San Diego, California 92121
Received August 16, 2000
A highly potent AMP deaminase (AMPDA) inhibitor series was discovered by replacing the
N3 substitutents of the two lead AMPDA inhibitor series with a conformationally restricted
group. The most potent compound, 3-[2-(3-carboxy-4-bromo-5,6,7,8-tetrahydronaphthyl)ethyl]-
3,6,7,8-tetrahydroimidazo[4,5-d][1,3]diazepin-8-ol (24b), represents a 10- to 250-fold enhance-
ment in AMPDA inhibitory potency without loss in the enzyme specificity. The potency of the
inhibitor 24b (AMPDA Ki ) 0.002 µM) is 105-fold lower than the Km for the substrate AMP. It
represents the most potent nonnucleotide AMPDA inhibitor known.
In tr od u ction
Adenosine protects organs from ischemic injury. Ad-
enosine levels increase during periods of ischemia or
stress, and as a result cellular injury is minimized. The
cellular protection is mediated through the activation
of the P1 purine receptors.1 It is anticipated that under
conditions of net ATP breakdown, inhibition of AMPDA
will further elevate adenosine levels, as the ATP break-
down product AMP is consumed through deamination
to IMP.2 A recent study by Holmes et al. which analyzed
the association of partial AMPDA deficiency with im-
proved prognosis in heart failure patients further sup-
ports AMPDA as a potential drug target.3
In our previous reports,4-7 we described the design
and characterization of the first potent and selective
AMPDA inhibitors. Our strategy involved substitution
of aliphatic and alkylaryl groups with carboxylic acids
at the N3 position of the aglycon of the adenosine
F igu r e 1. Inhibitor design.
potency of the aliphatic carboxylic acid series was
enhanced by R substituents. For example, a benzyl
group improved potency 10-fold possibly because of
increased hydrophobic interactions.5
deaminase transition state inhibitor, coformycin 1a 8
(AMPDA Ki ) 3.0 µM). Herein, we report the design,
rationale, and the detailed SAR study of this series of
compounds, optimized through utilization of groups with
significantly less conformational freedom.
In parallel with this observation, we also noticed this
hydrophobic pocket in the phenethyl series by introduc-
ing substituents at the starred (*) positions of compound
2.6 To further optimize the binding affinity to this
hydrophobic pocket, we examined the N3 substituents
that encompass the features of the two surrogates but
have significantly less conformational freedom. Con-
necting the starred (*) positions as depicted by structure
4, we arrived at the naphthyl derivative 23a , as an
example in which to assess the effectiveness of this
strategy.
Ch em istr y
The N3-substituted coformycin aglycon analogues
(Table 1) were prepared from the heterocycle, 6,7-di-
hydroimidazo[4,5-d][1,3]diazepin-8(3H)-one 59 using the
general three-step procedure described previously
(Scheme 1).5
The naphthyl electrophiles 9a -c were prepared from
the corresponding precursors 7a -c10 using a three-step
procedure. The vinyl derivatives 8a -c were prepared
via the palladium-catalyzed vinylation of the bromide
Design Ra tion a le
This potent AMPDA inhibitor series evolved from the
two structural leads, 3-[2-(3-carboxyphenyl)ethyl]cofor-
mycin aglycon 2 (AMPDA Ki ) 0.5 µM) and 3-[(5-
carboxy-5-benzyl)pentyl]coformycin aglycon 3 (AMPDA
Ki ) 0.41 µM) (Figure 1). We reported earlier that
* To whom correspondence should be addressed. Phone: 858-622-
5514. Fax: 858-622-5573. E-mail: rao@mbasis.com.
10.1021/jm000355t CCC: $20.00 © 2001 American Chemical Society
Published on Web 01/17/2001

614 J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 4
Ta ble 1. Physical Data of AMPDA Inhibitors
Kasibhatla et al.
Sch em e 3a
cmpd
mp (°C)
formulaa
23a
23b
23c
24a
24b
24c
24d
24e
24f
24g
25a
25b
25c
26a
26b
26c
26d
26e
26f
26g
26h
26i
220-235b
ndc
C19H18N4O3‚1.3H2O‚0.1AcOH
C20H16N4O3F3Nad
ndc
C19H16N4O3 BrNad
220-235b
200-220b
220-230b
220-230b
220-230b
>210b
C19H22N4O3‚0.5H2O‚0.3AcOH
C19H21N4O3Br‚2.5H2O‚1.2AcOH
C19H20N4O3Cl2‚1.4H2O
C26H28N4O4‚0.3H2O‚0.33AcOH
C22H28N4O4‚3H2O‚0.6AcOH
C20H24N4O4‚1.25H2O‚0.3AcOH
C20H24N4O4‚0.5H2O‚1.0AcOH
C20H20N4O3
C22H21N4O3F3
C21H21N4O3Br‚1H2O
C21H26N4O3
>230b
237-239
202-203
238-240b
160-165
147-150
100-102
132-135
159-162
143-145
170-172
112-115
108-110
C26H28N4O3‚0.25H2O
C
C
C
C
C
21H25N4O3Br‚1.2H2O‚0.1Et3N
21H24N4O3Cl2‚0.5H2O
28H32N4O4‚1.3H2O
a
Reagents: (a) Pd(OH)2/C, H2, MeOH; (b) Br2, AcOH; (c) i.
(CF3SO2)2O, Py, ii. vinyltributyltin, (PPh3)2PdCl2, LiCl, DMF; (d)
9-BBN, THF, 30% H2O2, 3 N NaOH; (e) CBr4, PPh3, CH2Cl2; (f) 1
N NaOH, dioxane; (g) Cs2CO3, BnBr, DMF; (h) S02Cl2, CH2Cl2; (i)
HBr, hexane, benzoyl peroxide.
24H32N4O4‚0.25H2O
22H28N4O4‚0.2H2O
C22H28N4O4‚0.8H2O
C
26H26N4O3Cl2‚0.6H2O
a
Analyses for C, H, and N were within 0.4% of the theoretical
values, unless otherwise stated. Decomposed. c Not determined,
b
Sch em e 4a
d
very deliquescent compound. Confirmed by LRMS.
Sch em e 1a
a
Reagents: (a) NaH, DMF, NaI; (b) NaBH4, MeOH, CH2Cl2;
(c) 1 N NaOH, dioxane or 10% Pd/C, H2, MeOH (R ) Bn).
Sch em e 2a
a
Reagents: (a) i. Pd(OH)2/C, H2, MeOH, ii. Br2, AcOH; (b)
K2CO3, DMSO and BnBr or i-PrI or MeI; (c) i. vinyltributyltin,
Pd(PPh3)4, DMF, ii. 9-BBN, THF, 30% H2O2, 3 N NaOH, iii. CBr4,
PPh3, CH2Cl2.
The electrophile 14 was prepared from 11a in the
following six-step procedure. Saponification of 11a fol-
lowed by alkylation with benzyl bromide and chlorina-
tion with SO2Cl2 gave the dichloro analogue 13. Palla-
dium-catalyzed vinylation of 13, followed by HBr addition
to the olefin bond in the presence of benzoyl peroxide,
gave the electrophile 14 (Scheme 3).12 In this latter case,
the usual two-step method (hydroboration/oxidation and
bromination) to prepare the electrophile 14 failed and
led only to decomposition byproducts.
a
Reagents: (a) vinyltributyltin, Pd(PPh3)4, DMF (R1 ) Br); (b)
i. (CF3S02)2O, Py, ii. vinyltributyltin, (PPh3)2PdCl2, LiCl, DMF (R1
) OH); (c) i. 9-BBN; 30% H2O2, 3 N NaOH, ii. CBr4, PPh3, CH2Cl2.
or the triflate. Hydroboration of 8a -c with 9-BBN
followed by oxidation gave the primary alcohols, which
were converted to the electrophiles 9a -c with CBr4 in
the presence of PPh3 (Scheme 2).
Similarly, compound 16 was prepared from 15 by
partial hydrogenation followed by electrophilic bromi-
nation (Scheme 4). Electrophiles 18a -c were prepared
by alkylation of the tetrahydronaphthol 16 followed by
the three-step procedure of vinylation, hydroboration/
oxidation, and bromination (Scheme 4). Finally, these
methods were also used to prepare compound 20 from
19.
Tetrahydronaphthyl derivatives were prepared by two
different routes (Schemes 3-5). The first route required
partial hydrogenation of the naphthyl derivatives as
shown in Schemes 3 and 4. Thus, intermediate 11a was
prepared from the naphthyl derivative 1011 by partial
hydrogenation in the presence of Pd(OH)2/C in MeOH
at 1 atm H2 pressure. Vinylation of 11a followed by
hydroboration/oxidation and bromination gave the elec-
trophile 12a . Preparation of compound 12b required
electrophilic substitution of 11a with bromine in acetic
acid to deliver a single regioisomer 11b (structure
determined by nOe experiments) which then was sub-
jected to the three-step procedure of palladium-catalyzed
vinylation, hydroboration/oxidation, and bromination.

AMP Deaminase Inhibitors
J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 4 615
Sch em e 5a
Ta ble 3. SAR of the Naphthylethyl and
5,6,7,8-Tetrahydro-3-carboxynaphthylethyl Ester Series
AMPDA
ADA
compd
R1
R2
R
Ki (µM)
Ki (µM)
a
Reagents: (a) dihydrofuran, toulene, sealed tube, 160 °C; (b)
25a
25b
25c
26a
26b
26c
26d
26e
26f
26g
26h
26i
H
H
Br
H
H
H
Cl
H
H
H
H
CF3
H
H
H
Br
Cl
OBn
Oi-Pr
OMe
H
Me
Et
Et
Et
Bn
Et
Et
Et
Et
Et
Et
Bn
1.8
35
14
>7.5
2.7
4.4
BBr3, CH2Cl2; EtOH; (c) vinylene carbonate, toluene, sealed tube.
Ta ble 2. SAR of the Naphthylethyl and
5,6,7,8-Tetrahydro-3-carboxy Naphthylethyl Series
1.3
5.0
1.0
0.5
0.3
3.8
2.3
2.4
0.3
3.4
0.72
0.53
>7.5
>7.5
>7.5
3.7
OMe
Cl
>7.5
>7.5
Cl
The targeted naphthyl derivative with a two-carbon
tether at the 1-position and a carboxylate in the 3-posi-
tion, 23a , exhibited a 20-fold improvement in the
inhibition potency (AMPDA Ki ) 0.02 µM) relative to
the two lead compounds 2 and 3. The compound also
retained the high selectivity for AMPDA (ADA Ki >1000
µM). In general, all of the final carboxylic acids in this
series exhibited good selectivity over ADA (Table 2).
Substitution of the B-ring of the naphthyl system of 23a
revealed that the binding affinity is very sensitive to
small variations. For example, a trifluoromethyl sub-
stituent at C5 (23b) or a bromine at C7 (23c) of the
naphthyl ring resulted in a 10-50-fold loss in affinity.
In contrast, saturation of the B-ring of the naphthyl to
the tetrahydronaphthyl system (i.e., 24a , AMPDA Ki )
0.015 µM) retained the potency. On the basis of the
above results and to avoid introducing chirality in the
N3 substituent, the SAR developed for 24a was focused
on substitutions at C2 (R1) and C4 (R2) of the A-ring. A
methoxy group at C2 or C4 (24g or 24f) or dichloro at
the C2- and C4 (24c) caused a 3-3.5-fold decrease in
potency, compared to the parent compound 24a . In-
creasing the size of the alkoxy substituent to isopropyl-
oxy (24e) at C4 resulted in substantial loss of activity
(6-fold). In contrast, the benzyloxy (24d ) showed a 2-fold
improvement in potency. Finally, introduction of a
bromine at the C4 resulted in a 7.5-fold enhancement
in potency and provided the most potent AMPDA
inhibitor, compound 24b (AMPDA Ki ) 0.002 µM).
In accord with our earlier observations,5-7 the corre-
sponding esters showed much less inhibitory potency
and selectivity (Table 3). The benzyloxy substituent
(26e) and the benzyl ester (26i) are the most potent
analogues among the esters, each with AMPDA Ki )
0.3 µM.
AMPDA
Ki (µM)
ADA
Ki (µM)
compd
R1
R2
23a
23b
23c
24a
24b
24c
24d
24e
24f
24g
H
H
Br
H
H
Cl
H
H
H
OMe
H
0.02
0.22
0.96
0.015
0.002
0.05
0.009
0.09
0.03
0.04
>1000
>7.5
>7.5
>7.5
>7.5
>7.5
>7.5
>7.5
>7.5
>7.5
CF3
H
H
Br
Cl
OBn
Oi-Pr
OMe
H
Alternatively, compounds 12a and 11a were prepared
using the short sequence presented in Scheme 5. With
some modifications (t-BuO-K+ in THF) of the procedure
reported by Boger and co-workers,13 the key intermedi-
ate 21 was prepared from cyclohexanone in one step in
82% yield. The rapid assembly of the tetrahydronaph-
thyl ring system, 12a , with all the requisite substitu-
tions on the aromatic ring was accomplished by a two-
step procedure.4 A Diels-Alder reaction of diene 21 with
dihydrofuran in a sealed tube furnished the tricyclic
intermediate 22 in good yield and high regioselectivity.
Treatment of this intermediate with BBr3 followed by
addition of EtOH provided the electrophile 12a in 54%
yield. Last, intermediate 11a was prepared in one step
from 21 following the reported procedure.13
Resu lts
The compounds reported in Table 1 were evaluated
as inhibitors of recombinant human E-type AMPDA and
calf intestinal adenosine deaminase (ADA).4 Inhibitor
potencies are reported in Tables 2 and 3. The inhibitor
screening concentrations used in the AMPDA and ADA
inhibition were 125 µM and 7.5 µM, respectively. In
select examples, ADA inhibition was evaluated at higher
concentrations in order to evaluate the full extent of the
selectivity of the enzyme inhibition.
Discu ssion
Our previous structure-activity relationships estab-
lished that coformycin aglycon analogues having an N3-
phenethyl side chain with a carboxylic acid group at the

616 J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 4
Kasibhatla et al.
meta-position (e.g., 2) are potent AMPDA inhibitors.6
The previous study also showed that hydrophobic sub-
stituents at the C5- and C6-positions of the phenyl ring
(*-positions in 2) increased potency. This report high-
lights the design of a new inhibitor series with enhanced
potency derived from conformational restriction of the
N3 substituent and optimization of the hydrophobic
interactions. Restricting conformational freedom, by
connecting the *-carbons of 3 (Figure 1), led to a very
potent series of AMPDA inhibitors (Table 2) that had
the additional benefit of increasing the hydrophobic
density at the *-carbons of 2 and eliminating the chiral
center of 3. Similar results where conformational re-
straint assisted to improve the binding affinity (5- to
10-fold) have been reported earlier.14a-c Subsequent
analogues revealed the spacial limitations around the
B-ring of the naphthyl (e.g., 23b and 23c).
Additionally, when the naphthyl ring was reduced to
a tetrahydronaphthyl ring, no loss in binding affinity
was observed. The electron-donating groups such as
methoxy or propyloxy (e.g., 24e, 24f, and 24g) on the
A-ring decreased the potency 1.5- to 4.5-fold, similar to
the result that was observed in the phenethyl series6
with a methoxy group. However, a benzyloxy substitu-
tion resulted in a 2-fold increase in potency compared
to the parent compound 24a . This enhancement in
activity with a benzyloxy substituent is reminiscent of
observations made with other AMPDA inhibitors having
benzyl substituents near the carboxylic acid group,5,7
which suggests that there may be some favorable
interactions between the π-electron density of the
aromatic ring and the region near the phosphate bind-
ing site. Thus, it is apparent that a relatively large
hydrophobic binding region exists close to the phosphate
binding site of AMPDA. Introduction of a bromine at
the C4 resulted in the most potent inhibitor, 24b,
AMPDA Ki ) 0.002 µM. This represents a remarkably
potent inhibitor considering that AMP has a Km of ca.
1 mM and is thus approximately 105-fold lower in
AMPDA affinity. This large improvement over AMP
suggests that 24b may bind in a manner that mimics
the transition state of deamination. In contrast, the
dichloro analogue, 24c, was 2.5-fold less potent than the
parent compound 24a , analogous to that which was
observed with the chloro substituent in the phenethyl
series.6
tion in a cellular model of net ATP depletion (e.g., 24a ).4
Thus, they may represent potential drugs to treat
ischemic tissue damage resulting from a stroke or a
heart attack.
Exp er im en ta l Section
Gen er a l Meth od s. Glassware for moisture sensitive reac-
tions was flame dried and cooled to room temperature in a
desiccator, and all reactions were carried out under an
atmosphere of nitrogen. Anhydrous solvents were purchased
from Aldrich and stored over 4 Å molecular sieves. THF was
freshly distilled from Na/benzophenone ketyl under nitrogen.
Flash chromatography was performed on 230-400 mesh EM
Science silica gel 60. Melting points were recorded on a Thomas
Hoover capillary melting point apparatus and are uncorrected.
1H spectra were obtained on a Varian Gemini-200 operating
at 200 MHz and recorded in units δ with tetramethylsilane (δ
0.00) as a reference line internal standard. Microanalyses were
performed by Robertson Microlit Laboratories, Inc., Madison,
NJ . Low resolution mass spectra were obtained from Mass
Consortium Corp., San Diego, CA.
En zym e Assa ys. The AMPDA and ADA Ki determinations
were performed as previously described.4
Meth yl 1-Vin yl-3-n a p h th oa te (8a ). To a solution of meth-
yl 1-bromo-3-naphthoate 7a (2.0 g, 7.54 mmol) in 60 mL of
dry DMF under nitrogen were added tetrakis(triphenylphos-
phine) palladium (0.44 g, 0.37 mmol) and vinyltributyltin (2.6
mL, 9.0 mmol). The mixture was degassed with N2 for 5 min.
The resulting mixture was heated at 80 °C for 3 h. NMR
analysis indicated complete reaction. After cooling, it was
partitioned between ether and brine. The organic phase was
stirred over 10% aqueous NaF solution for 4 h. The ether layer
was separated, washed with water and brine, and dried
(MgSO4). The solvent was removed, and the residue was
purified by chromatography (5% EtOAc in hexane) to give 1.6
g (85%) of 8a as an oil: 1H NMR (CDCl3) δ 3.91 (s, 3H), 5.55
(d, 1H, J ) 10.9 Hz), 5.9 (d, 1H, J ) 17.3 Hz), 7.3-7.8 (m,
3H), 7.8-8.2 (m, 2H), 8.21 (s, 1H), 8.54 (s, 1H).
Meth yl 1-(2-Br om oeth yl)-3-n a p h th oa te (9a ). To a solu-
tion of 9-BBN dimer (3.6 g, 15.0 mmol) in 40 mL of THF was
added a solution of 8a (1.6 g, 7.5 mmol) in 10 mL of THF, and
the resulting solution was stirred for 16 h. The solution was
cooled to -30 °C, and 30% H2O2 (3.4 mL, 30.0 mmol) was
added slowly, followed by 3 N NaOH (5.5 mmol, 16.5 mmol).
The reaction was allowed to warm to 5 °C and stirred for 4 h
at which time the heterogeneous solution was diluted with
water (150 mL) and extracted with ether (3 × 80 mL). The
combined ether layers were washed with water and brine and
dried (MgSO4). The solvent was removed, and the residue was
purified by chromatography (30% EtOAc in hexane) to give
1.1 g (63%) of methyl 1-(2-hydroxyethyl)-3-naphthoate as an
oil: 1H NMR (DMSO-d6) δ 3.26 (t, 2H, J ) 7.0 Hz), 3.76 (q,
2H, J ) 7.0 Hz), 3.89 (s, 3H), 4.8 (t, 1H, J ) 5.6 Hz,
exchangeable with D2O), 7.5-7.8 (m, 2H), 7.88 (s, 1H), 8.0-
8.3 (m, 2H), 8.5 (s, 1H).
Su m m a r y
We have demonstrated that attaching hydrophobic
substituents to compound 2 or restraining the confor-
mational freedom of the N3 substitution of compound
3 can boost the AMPDA inhibitory potency 160-fold. The
most potent compound identified, 24b (AMPDA Ki )
0.002 µM), bears little structural resemblance to the
substrate AMP and yet exhibits a remarkable improve-
ment (>105-fold) in binding affinity relative to AMP. The
tetrahydronaphthyl ring system with a 3-carboxylic acid
has the necessary negative charge and hydrophobic
composition to interact optimally with the ribose 5′-
monophosphate binding region of the enzyme. Moreover,
the N3 substitution may induce the correct orientation
of the diazepine base in a fashion analogous to the
transition state.4 Some of these AMPDA inhibitors have
demonstrated site- and event-specific adenosine regula-
To a solution of methyl 1-(2-hydroxyethyl)-3-naphthoate (1.1
g, 4.78 mmol) in 50 mL of dry CH2Cl2 under N2 was added
triphenylphosphine (1.88 g, 7.2 mmol), followed by carbon
tetrabromide (2.37 g, 7.2 mmol) slowly at 0 °C. The resulting
mixture was stirred for 30 min. The solvent was removed and
the residue purified by chromatography (5% EtOAc in hexane)
to give 1.1 g (80%) of 9a as an oil: 1H NMR (DMSO-d6) δ 3.14
(t, 2H, J ) 7.0 Hz), 3.68 (t, 2H, J ) 7.0 Hz), 3.9 (s, 3H), 7.4-
7.8 (m, 2H), 7.9 (s, 1H), 8.1-8.3 (m, 2H), 8.46 (s, 1H).
Eth yl 1-Vin yl-5-tr iflu or om eth yl-3-n a p h th oa te (8b). A
solution of ethyl 1-hydroxy-5-trifluoromethyl-3-naphthoate
7b12 (8.7 g, 30.6 mmol) in 100 mL of pyridine was cooled to 0
°C and slowly treated with trifluoromethanesulfonic anhydride
(6.0 mL, 35.7 mmol). After warming to room temperature, the
mixture was stirred for 3 h and the solvent evaporated. The
residue was diluted with 200 mL of water and extracted with
ether. The combined extracts were dried (MgSO4) and evapo-
rated to afford 9.5 g of dark syrup.

AMP Deaminase Inhibitors
J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 4 617
The crude triflate was dissolved in 120 mL of DMF and
combined with (PPh3)2Pd(Cl)2 (3.23 g, 4.6 mmol), PPh3 (3.23
g, 12.3 mmol), LiCl(10.38 g, 245.0 mmol), and vinyltributyl
tin (10.8 mL, 37.0 mmol). The resultant mixture was heated
at 90 °C for 5 h. Solvent was evaporated, and the residue was
diluted with ether (300 mL), washed with water (2 × 50 mL)
and aqueous NaF (2 × 50 mL), and dried (MgSO4). The solvent
was removed, and the residue was purified by chromatography
(5% EtOAc in hexane) to give 7.2 g (85%) of 8b as white solid:
mp 67 °C; 1H NMR (CDCl3) δ 0.92 (t, 3H, J ) 7.1 Hz), 4.48(q,
2H, J ) 7.1 Hz), 5.61 (d, 1H, J ) 11 Hz), 5.89 (d, 1H, J ) 17.2
Hz), 7.4 (dd, 1H, J 1 ) 11 Hz, J 2 ) 7.2 Hz), 7.6 (t, 1H, J ) 7.7
Hz), 7.95 (d, 1H, J ) 7.2 Hz), 8.28 (s, 1H), 8.35 (d, 1H, J ) 7.2
Hz), 8.9 (s, 1H). Similarly, compound 8c was prepared from
7c.
Ben zyl 1-(2-Br om oeth yl)-2,4-d ich lor o-5,6,7,8-tetr a h y-
d r o-3-n a p h th ylca r boxyla te (14). Into a mixture of 13 (8.3
g, 23.0 mmol) and benzoyl peroxide (0.24 g, 1.0 mmol) in 200
mL of hexane was bubbled HBr gas at 0 °C for 25 min. After
the mixture was stirred for 2 h at room temperature, it was
diluted with 200 mL of ether and washed with water (3 × 40
mL), dried (MgSO4), and concentrated. The crude product was
purified by chromatography (2% EtOAc in hexane) to give 5.0
g (50%) of 14: 1H NMR (DMSO-d6) δ 1.74 (m, 4H), 2.69 (m,
2H), 2.84 (m, 2H), 3.29 (t, 2H, J ) 5.4 Hz), 3.60 (t, 2H, J ) 5.4
Hz), 5.4 (s, 2H), 7.4 (m, 5H).
Eth yl 1-Hyd r oxy-4-br om o-5,6,7,8-tetr a h yd r o-2-n a p h -
th ylca r boxyla te (16). Compound 16 was prepared in two
steps from compound 15. Step 1 was performed using the
procedure described for the preparation of compound 10 from
11a .
Step 2. To a solution of ethyl 1-hydroxy-5,6,7,8-tetrahydro-
2-naphthylcarboxylate (6.4 g, 29.0 mmol) in 50 mL of acetic
acid was added a solution of bromine (1.5 mL, 29.0 mmol) in
50 mL of acetic acid over 2.0 h. After an additional 1 h, the
solvent was evaporated, the residue was diluted with ice-
water, and the compound was extracted with ether and dried
(MgSO4). The product was purified by chromatography (3%
EtOAc in hexane) to give 3.5 g (40% after two steps) of 16: 1H
NMR (DMSO-d6) δ 1.36 (t, 3H, J ) 7.1 Hz), 1.6-1.9 (m, 4H),
2.5-2.7 (m, 4H), 4.38 (q, 2H, J ) 7.1 Hz), 7.7 (s, 1H).
Eth yl 1-Br om o-4-isop r op yloxy-5,6,7,8-tetr a h yd r on a p h -
th yl-3-ca r boxyla te (17b). To a solution of 16 (8.0 g, 26.7
mmol) in 120 mL of DMSO was added K2CO3 (11.0 g, 80.1
mmol) followed by 2-iodopropane (3.9 mL, 40.0 mmol). After
2.0 h at 60 °C, the mixture was diluted with water (200 mL)
and extracted with ether (3 × 100 mL). The combined organic
layers were washed with water and dried (MgSO4). The solvent
was removed to give 8.3 g of 17b as oil and was used as is for
the next step: 1H NMR (DMSO-d6) δ 1.19 (d, 6H, J ) 6.1 Hz),
1.3 (t, 3H, J ) 7.0 Hz), 1.5-1.8 (m, 2H), 2.6-2.8 (m, 2H), 4.0-
4.4 (m, 3H), 7.69 (s, 1H). Similarly, compounds 17a and 17c
were made from 16.
Eth yl 1-(2-Br om oeth yl)-5-tr iflu or om eth yl-3-n aph th oate
(9b). Compound 9b was prepared from compound 8b (75%)
as an oil by using the procedures described for the preparation
of compound 9a from 8a : 1H NMR (DMSO-d6) δ 1.39 (t, 3H, J
) 7.0 Hz), 3.6-4.0 (m, 4H), 4.43 (q, 2H, J ) 7.0 Hz), 7.87 (t,
1H, J ) 8.1 Hz), 8.11 (s, 1H), 8.14 (d, 1H, J ) 9.5 Hz), 8.54 (d,
1H, J ) 8.4 Hz), 8.69 (s, 1H). Similarly, compound 9c was
made from 8c.
Eth yl 1-Hyd r oxy-5,6,7,8-tetr a h yd r o-3-n a p h th ylca r box-
yla te (11a ). A mixture of ethyl 1-hydroxy-3-naphthylcarbox-
ylate 1012 (3.0 g, 13.8 mmol) and 20% Pd(OH)2/C (1.0 g, wet)
in 200 mL of methanol was stirred under a 1 atm of H2 for 48
h. The catalyst was filtered through Celite, and the filtrate
evaporated to give 3.0 g (98%) of 11a as solid: 1H NMR (CDCl3)
δ 1.38 (t, 3H, J ) 7.2 Hz), 1.7-2.0 (m, 4H), 2.68 (t, 2H, J )
6.8 Hz), 2.78 (t, 2H, J ) 6.8 Hz), 4.35 (q, 2H, J ) 7.2 Hz), 5.48
(s, 1H, D20 exchangeable), 7.35 (s, 1H), 7.36 (br s, 1H).
E t h yl 1-(2-Br om oet h yl)-5,6,7,8-t et r a h yd r o-3-n a p h t h -
ylca r boxyla te (12a ). Compounds 12a and 12b were prepared
from compound 11a and 11b, respectively, by using the
procedures described earlier.4 This paper also describes an
alternative method for the preparation of compound 12a from
21.
Eth yl 1-(2-Br om oeth yl)-4-isop r op yloxy-5,6,7,8-tetr a h y-
d r on a p h th yl-3-ca r boxyla te (18b). Compound 18b was pre-
pared from compound 17b by using the procedures described
for the preparation of compound 9a from 7a (69%) as an oil:
1H NMR (DMSO-d6) δ 1.18 (d, 6H, J ) 6.1 Hz), 1.3 (t, 3H, J )
7.0 Hz), 1.5-1.8 (m, 2H), 2.6-2.8 (m, 2H), 3.1 (t, 1H, J ) 7.4
Hz), 3.68 (t, 1H, J ) 7.4 Hz), 4.1 (h, 1H, J ) 6.8 Hz), 4.27 (q,
2H, J ) 7.0 Hz), 7.37 (s, 1H). Similarly, compounds 18a and
18c were made from 17a and 17c, respectively.
Eth yl 1-(2-Br om oeth yl)-2-m eth oxy-5,6,7,8-tetr a h yd r o-
n a p h th yl-3-ca r boxyla te (20). Compound 20 was prepared
from compound 19 by using the procedures described for the
preparation of compound 18b from 15: 1H NMR (DMSO-d6)
δ 1.31 (t, 3H, J ) 7.0 Hz), 1.6-1.8 (m, 2H), 2.6-2.8 (m, 2H),
3.1 (t, 1H, J ) 7.2 Hz), 3.53 (t, 1H, J ) 7.2 Hz), 3.7 (s, 1H),
4.27 (q, 2H, J ) 7.0 Hz), 7.37 (s, 1H).
Ben zyl 1-H yd r oxy-2,4-d ich lor o-5,6,7,8-t et r a h yd r o-3-
n a p h th ylca r boxyla te (13). A solution of 11a (12.38 g, 56.2
mmol) in 100 mL of dioxane and a solution of 1 N NaOH (112.5
mL, 112.5 mmol) was heated at 70 °C for 36 h. After cooling
to room temperature, the solvents were removed under
vacuum. The residue was dissolved in 100 mL of water, and
the solution was adjusted to pH 3.5 with 3 N HCl, upon which
the product precipitated out. The solid was recovered by
filtration, washed with water and dried over P2O5 under
vacuum to give 9.44 g (86%) of 5,6,7,8-tetrahydro-1-hydroxy-
3-naphthoic acid.
To a mixture of 5,6,7,8-tetrahydro-1-hydroxy-3-naphthoic
acid (9.44 g, 49.0 mmol) and Cs2CO3 (19.1 g, 58.8 mmol) in
150 mL of DMF was added benzyl bromide (5.8 mL, 49.0 mmol)
dropwise, at -20 °C. The reaction mixture was slowly allowed
to come to 0 °C. After it was stirred for 18 h, the solvent was
removed under reduced pressure, and the residue was dis-
solved in 200 mL of ether. The ethereal solution was washed
with 0.5 N HCl and water and dried (MgSO4). The solvent was
removed, and the residue was purified by chromatography
(25% EtOAc in hexane) to give 12.6 g (96%) of benzyl 5,6,7,8-
tetrahydro-1-hydroxy-3-naphthylcarboxylate: 1H NMR (DMSO-
d6) δ 1.68 (m, 4H), 2.55 (m, 2H), 2.69 (m, 2H), 5.28 (s, 2H),
7.18 (s, 2H), 7.21 (s, 1H), 7.4 (m, 5H), 9.65 (s, 1H).
3-[2-(3-Ca r boxy-2,4-d ich lor o-5,6,7,8-tetr a h yd r on a p h th -
yl)eth yl]-3,6,7,8- tetr a h yd r oim id a zo[4,5-d ][1,3]d ia zep in -
8-ol (24c). A mixture of 3-[2-(3-carbobenzyloxy-2,4-dichloro-
5,6,7,8-tetrahydronaphthyl)ethyl]-3,6,7,8-tetrahydroimidazo[4,5-
d][1,3]diazepin-8-ol 26i (298 mg, 0.58 mmol) and 35 mg of 10%
Pd/C in 20 mL of MeOH was stirred under H2 at 1 atm
(balloon) for 30 h and then filtered over Celite. The filtrate
was evaporated, and the residue was taken into 1 mL of 0.1
N NaOH, mixed with 2.0 g of DOWEX-1 × 8-400 acetate ion-
exchange resin for 45 min, and then filtered. The resin was
washed with water (100 mL) followed by a mixture of 10:1 of
0.1 N AcOH and MeOH (500 mL). The AcOH/MeOH filtrate
was lyophilized to provide 104 mg (46%) of 24c as white
To a solution of benzyl 5,6,7,8-tetrahydro-1-hydroxy-3-
naphthylcarboxylate (9.0 g, 31.5 mmol) in 100 mL of CH2Cl2
was added a solution of SO2Cl2 (79 mL, 79.0 mmol) at 0 °C.
After it was stirred for 30 min, the mixture was neutralized
with saturated NaHCO3, diluted with cold water (100 mL),
and extracted with CH2Cl2 (3 × 200 mL). The combined organic
layers were washed with water (2 × 20 mL), dried (MgSO4),
and concentrated. The crude product was purified by column
chromatography (10% EtOAc in hexane) to give 8.3 g (74%) of
13: 1H NMR (DMSO-d6) δ 1.71 (m, 4H), 2.63 (m, 4H), 5.39 (s,
2H), 7.4 (m, 5H), 9.7 (br peak, 1H).
1
powder: mp 220-230 °C (decomposes); H NMR (DMSO-d6)
δ 1.68 (m, 4H), 2.65 (m, 4H), 3.12 (m, 2H), 3.18 (br s, 2H), 4.0
(m, 2H), 4.8 (br s, 1H), 7.0 (d, 1H, J ) 4.0 Hz), 7.25 (s, 1H),
7.55 (m, 1H). Anal. (C19H20N4O3Cl2‚1.4H2O) C, H, N.
The following is the general three-step procedure for prepa-
ration of compound 24b from 6,7-dihydroimidazo[4,5-d][1,3]-
diazepin-8(3H)-one 5.9

618 J ournal of Medicinal Chemistry, 2001, Vol. 44, No. 4
Kasibhatla et al.
Circulation 1999, 99, 1422-1425. Also see most recent related
report: Anderson, J . L.; Habashi, J .; Carlquist, J . F.; Muhlestein,
J . B.; Home, B. D.; Bair, T. L.; Pearson, R. R.; Hart, N. A
Common Variant of the AMPD1 Gene Predicts Improved Car-
diovascular Survival in Patients With Coronary Artery Disease.
J . Am. Coll. Cardiol. 2000, 36(4), 1248-1252.
3-[2-(3-Ca r boxy-4-br om o-5,6,7,8-tetr a h yd r on a p h th yl)-
et h yl]-3,6,7,8-t et r a h yd r oim id a zo[4,5-d ][1,3]d ia zep in -8-
ol (24b). Step 1. Alk yla tion . According to the procedure
previously described,5 compound 6,7-dihydroimidazo[4,5-d]-
[1,3]diazepin-8(3H)-one 59 was alkylated with ethyl 1-(2-
bromoethyl)-4-bromo-5,6,7,8-tetrahydronaphthyl-3-carboxy-
late 12b in the presence of NaH. Chromatography on SiO2 with
a CH2Cl2/MeOH gradient of 20:1, 18:1, and 15:1 provided 3-[2-
(3-carboethoxy-4-bromo-5,6,7,8-tetrahydronaphthyl)ethyl]-6,7-
dihydroimidazo-[4,5-d][1,3]diazepin-8(3H)-one: 1H NMR (DM-
SO-d6) δ 1.3 (t, 3H, J ) 7.0 Hz), 1.74 (m, 4H), 2.74 (m, 4H),
3.0 (t, 2H, J ) 7.4 Hz), 3.72 (d, 2H, J ) 4.1 Hz), 4.17 (t, 2H, J
) 7.4 Hz), 4.25 (q, 2H, J ) 7.0 Hz), 7.19 (s, 1H), 7.43 (d, 1H,
J ) 4.6 Hz), 7.57 (s, 1H), 8.4 (m, 1H).
Step 2. Red u ction . According to the procedure previously
described,4 3-[2-(3-carboethoxy-5,6,7,8-tetrahydronaphthyl)-
ethyl]-6,7-dihydroimidazo-[4,5-d][1,3]diazepin-8(3H)-one was
reduced with NaBH4. Chromatography on SiO2 with a CH2-
Cl2/MeOH gradient of 15:1 and 10:1 with 0.3% Et3N provided
3-[2-(3-carboethoxy-4-bromo-5,6,7,8-tetrahydronaphthyl)ethyl]-
3,6,7,8-tetrahydroimidazo [4,5-d][1,3]diazepin-8-ol 26c: mp
100-102 °C; 1H NMR (DMSO-d6) δ 1.3 (t, 3H, J ) 7.0 Hz),
1.71 (m, 4H), 2.7 (m, 4H), 2.97 (t, 2H, J ) 7.4 Hz), 3.1 (br s,
2H), 3.94.1 (m, 2H), 4.26 (q, 2H, J ) 7.0 Hz), 4.78 (m, 1H), 4.9
(br s, 1H), 7.1 (d, 1H, J ) 4.4 Hz), 7.2 (s, 1H), 7.7 (s, 1H), 7.8
(m, 1H). Anal. (C21H25N4O3Br‚1.2H2O‚0.1Et3N) C, H, N.
Step 3. Hyd r olysis. According to the procedure previously
described,4 3-[2-(3-carboethoxy-4-bromo-5,6,7,8-tetrahydronaph-
thyl)ethyl]-3,6,7,8-tetrahydroimidazo [4,5-d][1,3]diazepin-8-ol
26c was hydrolyzed with 0.1 N NaOH in dioxane. The product
was isolated with DOWEX-1 × 8-400 acetate ion-exchange
resin to provide 24b as a white powder: mp 200-220 °C
(decomposes); 1H NMR (DMSO-d6) δ 1.69 (m, 4H), 2.65 (m,
4H), 2.85 (t, 2H, J ) 7.4 Hz), 3.18 (br s, 2H), 4.0 (t, 2H, J )
7.4 Hz), 4.8 (br s, 1H), 4.95 (br s, 1H), 6.86 (s, 1H), 7.0 (d, 1H,
J ) 4.0 Hz), 7.27 (s, 1H), 7.5 (br s, 1H). Anal. (C19H21N4O3Br‚
3.0H2O‚1.0CH3CO2H) C, H, N.
(4) Erion, M. D.; Kasibhatla, S. R.; Bookser, B. C.; van Poelje, P.
D.; Reddy, M. R.; Gruber, H. E.; Appleman, J . R. Discovery of
AMP Mimetics that Exhibit High Inhibitory Potency and
Specificity for AMP Deaminase. J . Am. Chem. Soc. 1999, 121,
308-319.
(5) Bookser, B. C.; Kasibhatla, S. R.; Appleman, J . R.; Erion, M. D.
AMP Deaminase Inhibitors. 2. Initial Discovery of a Non-
Nucleotide Transition State Inhibitor Series. J . Med. Chem.
2000, 43, 1495-1507.
(6) Kasibhatla, S. R.; Bookser, B. C.; Probst, G.; Appleman, J . R.;
Erion, M. D. AMP Deaminase Inhibitors. 3. SAR of 3-(Car-
boxyarylalkyl)Coformycin Aglycon Analogues. J . Med. Chem.
2000, 43, 1508-1518.
(7) Bookser, B. C.; Kasibhatla, S. R.; Erion, M. D. AMP Deaminase
Inhibitors. 4. Alkyl-Malonates as Ribose 5′-Monophosphate
Mimetics. J . Med. Chem. 2000, 43, 1519-1524.
(8) (a) Isolation and identification: Ohno, M.; Yagisawa, N.; Shiba-
hara, S.; Kondo, S.; Maeda, K.; Umezawa, H. Structure of
Coformycin, an Unusual Nucleoside of Microbial origin. J . Am.
Chem. Soc. 1974, 96, 4327-4328.
(9) Chan, E.; Putt, S. R.; Showalter, H. D.; Baker, D. C. Total
Synthesis of (8R)-3- (2-Deoxy-b-D-erythro-pentofuranosyl)-3,6,7,8-
tetrahydroimidazolo[4,5-d][1,3]diazepine-8-ol (Pentostatin), the
Potent Inhibitor of Adenosine Deaminase. J . Org. Chem. 1982,
47, 3457-3464.
(10) Compound 7a was prepared in two steps from 3-amino-2-
naphthoic acid as described earlier in the literature.11 The
precursors 7b and 7c were synthesized from the 2-(trifluoro-
methyl)benzaldehyde and 4-bromobenzaldehyde, respectively,
using known procedures: Baddar, F. G.; El-Assal, L. S.; Baghos,
V. B. 1-Phenylnaphthalenes. Part II. The Cyclization of Ethyl
Hydrogen γγ-di-o-methoxyphenyl and γγ-di-p-methoxyphenyl-
itaconate to the corresponding 1-phenylnaphthalenes. J . Chem.
Soc. 1955, 1714-1718.
(11) Adcock, W.; Wells, P. R. Substituent Effects in Naphthalene; The
Synthesis of 4,5,6,7 and 8-substituted 2-Naphthoic Acids. Aust.
J . Chem. 1965, 18, 1351-1364.
Ack n ow led gm en t. We thank Dr. J ames R. Apple-
man for his scientific contribution.
(12) The benzyl ester was chosen for compound 14, since hydrolysis
of the hindered ethyl ester 26d to give the final carboxylic acid
24c required harsh conditions and led to some decomposition of
the product. To avoid this difficulty, and to simplify purification
at the final stage, the benzyl ester 26i was prepared. This
modification allows final stage ester hydrogenolysis to give the
final product 24c without any detectable dehalogenation.
(13) Boger, D. L.; Mullican, M. D. Preparation of Inverse Electron
Demand Diels-Alder Reaction of an Electron-Deficient Diene:
Methyl 2-Oxo-5,6,7,8-Tetrahydro-2H-1-Benzopyran-3-Carboxy-
late. Org. Synth. 1987, 65, 98-107 and references therein.
(14) (a) von Geldern, T. W.; Kester, J . A.; Bal, R.; Wu-Wong, J . R.;
Chiou, W.; Dixon, D. B.; Opgennorth, T. J . Azole Endothelin
Antagonists. 2. Structure-Activity Studies. J . Med. Chem. 1996,
39, 968-981. (b) Brown, F. J .; Yee, Y. K.; Cronk, L. A.; Hebbel,
K. C.; Krell, R. D.; Snyder, D. W. Evolution of a series of
Peptidoleukotriene Antagonists: Synthesis and Structure-
Activity Relationships of 1.6-Disubstituted Indoles and Inda-
zoles. J . Med. Chem. 1990, 33, 1771-1781. (c) von Wijngaarden,
I.; Kruse, C. G.; van der Heyden, J . A.; Tulp, M. T. 2-Phenylpyr-
roles as Conformationally Restricted Benzamide Analogues. A
New Class of Potential Antipsychotics. 1. J . Med. Chem. 1987,
30, 2099-2104.
Su p p or tin g In for m a tion Ava ila ble: Elemental analysis
data for the compounds in Table 1. This material is available
free of charge via the Internet at http://pubs.acs.org.
Refer en ces
(1) (a) J acobson, K. A.; van Galen, P. J .; Williams, M. Adenosine
Receptors: Pharmacology, Structure-Activity Relationships,
and Therapeutic Potential. J . Med. Chem. 1992, 35, 407-422.
(b) Erion, M. D. Adenosine Receptors as Pharmacological
Targets. Annu. Rep. Med. Chem. 1993, 28, 295-304.
(2) (a) Chen, W.; Hoerter, J .; Gueron, M. Comparison of AMP
Degradation in the Perfused Rat Heart during 2-deoxy-D-glucose
perfusion and Anoxia. Part I: The Release of Adenosine and
Inosine. J . Mol. Cell. Cardiol. 1996, 28, 2163-2174. (b) Chen,
W.; Gueron, M. AMP Degradation in the Perfused Rat Heart
during 2-deoxy-D-glucose perfusion and Anoxia. Part II: The
Determination of the Degradation Pathways Using an Adenosine
Deaminase Inhibitor. J . Mol. Cell. Cardiol. 1996, 28, 2175-2182.
(3) Loh, E.; Rebbeck, T. R.; Mahoney, P. D.; DeNofrio, D.; Swain, J .
L.; Holmes, E. W. Common Variant in AMPD1 Gene Predicts
Improved Clinical Outcome in Patients With Heart Failure.
J M000355T