Pyridazinoquinolinetriones as NMDA glycine-site antagonists with oral antinociceptive activity in a model of neuropathic pain

J. Med. Chem. 2007, 50, 3113-3131

3113

Pyridazinoquinolinetriones as NMDA Glycine-Site Antagonists with Oral Antinociceptive

Activity in a Model of Neuropathic Pain

Thomas M. Bare,⁺Dean G. Brown,* Carey L. Horchler,* Megan Murphy,* Rebecca A. Urbanek,*^,†Vernon Alford,

Christine Barlaam, Martin C. Dyroff, James B. Empfield, Janet M. Forst, Keith J. Herzog, Richard A. Keith, Alan S. Kirschner,

Chi-Ming C. Lee, Joseph Lewis, Frances M. McLaren, Kathy L. Neilson, Gary B. Steelman, Shephali Trivedi,

Edward P. Vacek, and Wenhua Xiao^#

AstraZeneca Pharmaceuticals LP, 1800 Concord Pike, Wilmington, Delaware 19803

ReceiVed February 23, 2006

A series of 7-chloro-2,3-dihydro-2-[1-(pyridinyl)alkyl]-pyridazino[4,5-b]quinoline-1,4,10(5H)-triones were

synthesized and found to have potent activity at the glycine site of the NMDA receptor. In some cases,

these compounds possessed poor aqueous solubility that may have contributed to poor rat oral bioavailability.

Subsequently, compounds have been identified with improved aqueous solubility and oral bioavailability.

Several of these compounds were examined in a rat chronic constrictive injury (CCI) model of neuropathic

pain and found to have potent activity when dosed orally.

Introduction

N-Methyl-D-aspartate (NMDA) receptors are ligand-gated ion

channels that are activated by the excitatory amino acid

L-glutamate. These receptors also require the coagonist glycine

for activation of the receptor.¹The fully functional NMDA

receptor is a heteromultimeric complex composed of at least

one NR1 subunit and one NR2 subunit.²The NR1 subunit comes

from a single gene, but can exist as eight different isoforms.³

The NR2 subunit can arise from four different genes and is

divided into the subtypes NR2A, NR2B, NR2C, and NR2D.^4,5

An NR3 subunit is also known and possibly has implications

in regulation during development.⁶The various sites of ligand

interaction are well characterized as it pertains to receptor

subtype. The glycine binding site is associated with the NR1

subunit, whereas the glutamate site is associated with the NR2

subunit.^7-9Polyamine-site antagonists such as ifenprodil are

thought to bind at the NR2B subunit.¹⁰A high-affinity Zn²⁺

binding site is located on the NR2A subunit and shares some

similarities to the ifenprodil site found on the NR2B subunit.¹¹

Painful peripheral neuropathy is the result of changes in both

the peripheral and central nervous systems following nerve

damage due to trauma, disease, and certain toxins.^12-14Central

sensitization, an abnormal hyperexcitable state of spinal cord

dorsal horn neurons evoked by activity at glutamatergic NMDA

synapses, has been implicated as one of the key central

changes.¹⁵“Wind-up”, a hyperexcitable condition in dorsal horn

neurons evoked in normal animals by repetitive input from

C-fiber nociceptors, is also believed to be mediated via NMDA

synapses.¹⁶Central sensitization is also implicated in the

abnormal pain syndromes that follow injury to the spinal cord.¹⁷

Central sensitization is believed to be at least partly responsible

for the hyperalgesia (supernormal pain caused by a normally

painful stimulus) and allodynia (pain caused by a stimulus that

would ordinarily be painless) that are seen in patients with

painful peripheral neuropathies.¹⁸

Figure 1. The 7-chloro-2,3-dihydro-2-[1-(pyridinyl)alkyl]-pyridazino-

[4,5-b]quinoline-1,4,10(5H)-trione (PQT) class of compounds.

NMDA receptors are known to play a role in central

sensitization in the dorsal horn of spinal cord.^19-21It is reported

that NMDA antagonists block and reverse this phenomena.¹⁹

The condition of “wind-up” has also been linked to NMDA

receptors.^22-23It has been reported that ketamine,²⁴memantine,²⁵

and MK-801²⁵inhibit wind-up on dorsal horn neurons. It has

been established that compounds which block activation of the

NMDA receptor also demonstrate activity in models of neuro-

pathic pain.²⁶However, antagonists blocking the glutamate site

or the ion channel give rise to unacceptable motor side effects.²⁷

There is evidence that indicates that antagonists may attenuate

pain in neuropathic pain models via interacting with the glycine

site of the NMDA receptor.^28,29

We had previously identified the 7-chloro-2,3-dihydro-2-[1-

(pyridinyl)alkyl]-pyridazino[4,5-b]quinoline-1,4,10(5H)-tri-

ones (PQTs), such as ZD9379, 1, as potent glycine-site

antagonists targeted for the prevention of stroke when admin-

istered intravenously.³⁰We sought to re-examine this class of

compounds, specifically those related to substructure 2, as

possible compounds for use in the oral treatment of neuropathic

pain. In doing so, part of our strategy was to optimize binding

affinity and aqueous solubility, anticipating that this would result

in compounds with good oral bioavailability and activity in

neuropathic pain models.

* Corresponding authors.

^†To whom correspondence should be addressed: Tel: 302-886-4818.

Fax: 302-886-5382. E-mail: rebecca.urbanek@astrazeneca.com.

⁺Present Address: Villanova Univ., Dept. of Chemistry, Mendel 214B,

800 Lancaster Ave., Villanova, PA 19085-1699.

^#Present Address: McGill Univ. Anesthesia Research Unit. McIntyre

Med Bldg, Rm. 1202. 3655 Promenade Sir William Osler. Montreal H3G

1Y6. Canada.

Published on Web 06/02/2007

3114 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 13

Bare et al.

Scheme 1. General Synthesis of

Scheme 3. Alternative Synthesis of Acetylenic

7-Chloro-2,3-dihydro-2-[1-(pyridinyl)alkyl]-

Pyridazinoquinolinetriones^a

pyridazino[4,5-b]quinoline-1,4,10(5H)-triones^a

^aReagents and conditions: (a) Ar/HetArX, cat. Pd(PPh₃)₂Cl₂, cat. CuI,

Et₃N, BHT, CH₂Cl₂; (b) CH₃SO₃H, THF.

While the general synthetic route of the pyridazinoquinolin-

etriones is outlined in Scheme 1, a few of the intermediates 8

were further diversified en route to 9; see Schemes 2 and 3.

For example, in Scheme 2, aromatic nitro groups present on

intermediate 8 were reduced and the subsequent anilines

converted to ureas using standard protocols. These urea products

were cyclized under the standard conditions to afford the final

PQT’s 9ad-ag. The acetylenic PQTs, Scheme 3, were accessed

via palladium-catalyzed coupling of 8ah with the appropriate

aryl or heteroaryl halides under Sonogashira conditions.³¹These

intermediates were then cyclized to afford the final PQTs 9ah-

ak. Diversification at the penultimate step was required as

attempts to introduce substituents directly to the cyclized

acetylenic compound 9 were hindered by the general insolubility

of the final products. Thus, while the aryl or heteroaryl halides

could be effectively coupled to the cyclized acetylenic PQT 9ag,

purification was not feasible.

Commercially available and synthesized hydrazines were

employed in the construction of intermediates 8. Many of the

hydrazines were synthesized using standard protocols, either

beginning with the appropriate ketone or aldehyde and proceed-

ing via the hydrazone intermediate, or synthesized from tert-

butyl carbazate and the appropriate halide. The synthesis of

propargyl hydrazines was performed by coupling propargyl

alcohol with aryl bromides or iodides using Sonogashira

conditions³¹to give the aryl propargylic alcohols. These alcohols

were then converted to the corresponding halides, which were

then treated with tert-butyl carbazate to afford the tert-butyl

^aReagents and conditions: (a) KO^tBu, DMAD, ^tBuOH, reflux; (b)

NaOH, H₂O, 60 °C; (c) pyrrolidine, DCC, THF; (d) KOH, H₂O, 60 °C; (e)

R₁R₂NHNH^tBoc, CMC or EDCI, THF or CH₂Cl₂, cat. DMAP; (f)

CH₃SO₃H, THF.

Chemistry

The general synthetic route to the core pyridazinoquinolin-

etrione scaffold can be seen in Scheme 1. Reaction of the

anthrinilate ester 3 and dimethyl acetylenedicarboxylate provided

the intermediate diester 4. Selective hydrolysis of the ester in

the 2-position and subsequent amide formation afforded the

pyrrolidine amide 6. The remaining ester was then hydrolyzed

to give the acid-amide intermediate 7, which served as a useful

diversification point for construction of the pyridazinoquino-

linetriones. The intermediate 7 was coupled with tert-butyl

carbamate-protected hydrazines. The intermediate 8 was then

cyclized using methanesulfonic acid to give the desired PQTs

9a-ac.

Scheme 2. Synthesis of a Subset of Pyridazinoquinolinetriones^a

^aReagents and conditions: (a) Dioctadecyl-4,4′-bipyridinium dibromide, sodium dithionate, K₂CO₃, CH₂Cl_2-H₂O; (b) phenyl isocyanate or N,N-

dimethylcarbamoyl chloride, Et₃N, cat. DMAP, CH₂Cl₂; (c) MeSO₃H, THF; (d) dimethylcarbamoyl chloride or tert-butyl isocyanate, Et₃N, CH₂Cl₂.

AntinociceptiVe NMDA Glycine-Site Antagonists

Journal of Medicinal Chemistry, 2007, Vol. 50, No. 13 3115

Table 1. In Vitro Activity of R-Pyridyl Analogues

Scheme 4. Enantioselective Synthesis of Hydrazine

Intermediates^a

t

^aReagents and conditions: (a) MsCl, Et₃N, CH₂Cl₂; (d) BocNHNH₂,

iPr₂NEt, DMF, 90 °C, 6 h.

Figure 2. Three pyridazinoquinolinetrione starting points.

carbamate-protected hydrazines. Synthetic details for the syn-

thesized hydrazines can be found in the Experimental Section.

Chiral hydrazines were synthesized according to Scheme 4.

Preparation of (R)-1-pyridin-2-yl-ethanol was performed using

the procedure previously described.³²The alcohol was converted

to the secondary mesylate, and then displacement occurred

with inversion of the stereocenter using the Boc-protected

hydrazine. The reaction proceeded with good enantioselectivity

(>95% ee), but with relatively poor yield (18%). Alternatively,

the chiral hydrazines used for preparation of compounds 9d and

9e could be separated from the racemic hydrazine using chiral

preparatory chromatography, details are given in the Experi-

mental Section.

Discussion

^aK_ifor [³H] MDL105519 binding. The average ( standard deviation of

at least two experiments is reported. ^bSolubilities were measured in the

presence of NaCl, see Experimental Section. ^cRecorded at pH 7.4, see

Experimental Section. ^dThe methanesulfonate salt was tested.

The NMDA glycine-site antagonist project for the treatment

of neuropathic pain employed a pool of ∼3800 compounds

previously synthesized for a glycine-site NMDA antagonist

program targeting intravenous treatment of stroke.³⁰

Those compounds that had a reasonable binding affinity ([³H]-

glycine IC₅₀e 1 µM)³⁰for the glycine site of the NMDA

receptor were then screened in a high throughput blood level

assay (HTBLA) to determine oral PK parameters.³³Binding

affinity, oral PK data, and structural diversity were considered

to allow prioritization of compounds for assessment in the

chronic constrictive injury (CCI) model of neuropathic pain.³⁴

Three chemical subseries that were chosen for further

optimization are shown in Figure 2. Additional analogues of

these in ViVo active compounds were synthesized with the goal

of achieving improved oral bioavailability. Here we describe

our strategies for achieving good oral activity by optimizing

the binding affinity and aqueous solubility within the three

subseries.

tion of alkyl substitution R to the pyridazinoquinolinetrione core

might distort the planarity of these compounds, affording

improved aqueous solubility. Substitution of this type at the R

position, in general, led to a very slight decrease in binding

affinity as evidenced by the comparison of 9a with 9f and 9b

with 9d. This introduction of branching did result in improved

aqueous solubility in the 4-pyridyl compounds as shown by the

comparison of 9a with 9f. Because of the solubility method

that was used, it is not possible to determine whether solubility

was enhanced with R position substitution in the 2- or 3-pyridyl

series, but solubility was not limiting in those series as it was

in the 4-pyridyl series. Substitution of an ethyl group as in 9g

led to a sharp decrease in binding affinity (K_i) 1.9 µM), as

did any groups larger than methyl.³⁵The two enantiomers of

the R-methyl-2-pyridyl-substituted PQT were tested, and inter-

estingly there was a clear binding preference for the (S)-

stereoisomer 9d (K_i) 207 nM) over the (R)-stereoisomer 9e

(K_i) 8.2 µM). The pyrazine 9h did not show improvements

over the initial lead with respect to binding affinity but had

improved aqueous solubility.

r-Alkylheteroaryl Series. The lead in the R-alkyl heteroaryl

subseries was the 4-pyridyl analogue 9a (K_i) 115 nM, Table

1). The two positional isomers of this compound (9b and 9c)

did not show improvements in binding affinity, but did possess

enhanced aqueous solubility. It was hypothesized that incorpora-

3116 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 13

Bare et al.

Table 2. In Vitro Activity of Five-membered Ring Heterocycles and

Table 3. In Vitro Activity of Ester Subseries Analogues

Benzofused Analogues

^aK_ifor [³H] MDL105519 binding. The average ( standard deviation

of at least two experiments is reported. ^bSolubilities were measured

in the presence of NaCl, see Experimental Section. ^cSolubilities were

measured in the absence in NaCl, see Experimental Section. ^dRecorded at

pH 7.4, see Experimental Section. ^eMeasured only once. ^fND ) Not

determined.

In ViVo data on these compounds are reported in Table 5.

The initial lead 9a was active in the CCI model of neuropathic

pain at an oral dose of 3 mg/kg but was found to have a limited

rat oral bioavailability of only 5%. The corresponding pyridyl

isomers, 9b and 9c, were also tested in the CCI model. 9c was

found to be active at 15 mg/kg but 9b was inactive when

tested at 30 mg/kg. The lack of in ViVo activity of 9b cannot be

explained by binding affinity since it is nearly equipotent

with the other pyridyl isomers. Poor oral bioavailability could

be the cause; however, it was not assessed (see footnote c in

Table 5). Interestingly, the R-methyl analogues of 9b (9d and

9e) were both active in the CCI model, even though 9e

possessed weak binding affinity (K_i) 8.2 µM). This can be

explained by the fact that they possessed oral bioavailability

^aK_ifor [³H] MDL105519 binding. The average ( standard deviation of

at least two experiments is reported. ^bSolubilities were measured in the

absence of NaCl, see Experimental Section. ^cRecorded at pH 7.4, see

Experimental Section. ^dThe methanesulfonate salt was tested.

AntinociceptiVe NMDA Glycine-Site Antagonists

Journal of Medicinal Chemistry, 2007, Vol. 50, No. 13 3117

Table 4. In Vitro Activity of Acetylenic Aromatic and Heterocyclic

Analogues

the three furans (9i and 9j) tested and the isoxazole 9s and

thiazole 9t were active in the CCI assay when tested at 15 mg/

kg tid (5 mg/kg for 9j). The CCI-inactive thiophene 9r is one

of the most potent binders in this group (K_i) 13 nM), with a

rat oral bioavailability of 28%, although its aqueous solubility

is rather low. The less potent binder 9j (K_i) 44 nM) has

essentially the same aqueous solubility and oral bioavailability

yet is active at 5 mg/kg tid in the CCI model. The most

encouraging compound of this group, the isoxazole 9s, possesses

a K_iof 39 nM, aqueous solubility of 0.22 mg/mL, activity in

the CCI model at 15 mg/kg and 40% rat oral bioavailability;

this puts it on par with the best of the R-pyridyl compounds

outlined in Table 1.

Ester Subseries. The methyl ester 9u was one of the lead

compounds for further optimization efforts. While it possessed

fairly potent binding affinity (K_i) 45 nM, Table 3), it had very

poor aqueous solubility (0.0089 mg/mL) and underwent rapid

ester hydrolysis in ViVo (data not shown). Even though the

compound is active when dosed orally in the CCI model at 30

mg/kg tid, the rat oral biovailability is merely 7% (Table 5).

This poor oral bioavailability is attributable to both the poor

aqueous solubility and hydrolytic instability. The R-methyl

analogue 9v was prepared to improve solubility, as was

successful in the pyridyl series. In this case, more than a 5-fold

drop off in binding affinity was observed (K_i) 45 nM

compared with K_i) 268 nM) with a 4-fold increase in aqueous

solubility (0.0089 mg/mL compared with 0.04 mg/mL). The

carboxylic acid 9w and the tetrazole analogue (not shown) were

equipotent with the parent methyl ester in the binding

assay. These compounds were not tested in ViVo because of

anticipated poor brain penetration, but they provided evidence

that polarity would be tolerated in the 4-position of the phenyl

ring. The methyl ester at the 3-position, 9x, was prepared for

binding affinity determination to assess whether changes to the

3-position of the phenyl ring would be tolerated, as they were

in the 4-position. It was found to be nearly equipotent in binding

with the parent ester at the 4-position 9u. The compounds, not

surprisingly, possessed very similar physicochemical properties.

This compound was not assessed in ViVo because of the

assumption that the methyl ester would be hydrolytically

unstable, as it was in 9u. A variety of analogues at the 3- and

4-positions were prepared to maintain or improve the binding

affinity of this class of phenyl compounds with a corresponding

improvement in physical properties, particularly aqueous solu-

bility and hydrolytic stability. In general, the ureas and amides

prepared showed a tolerance for a variety of alkyl and alkyl-

ether substituents when measured in the in Vitro binding assay,

as they lost only ca. 2-5 fold in binding affinity. Carbamates

(data not shown) had similar profiles. A few examples of the

prepared compounds are presented in Table 3. In many cases,

the solubilities are close to or above 0.1 mg/mL, a significant

improvement over the methyl ester at 0.0089 mg/mL. In short,

analogues of the methyl esters 9u and 9x were synthesized that

were much more soluble than the parent ester, hydrolytically

more stable, and in some cases possessed robust activity in the

CCI model when tested at 15 mg/kg, such as the amide 9y and

the urea 9ab (Table 5).

^aK_ifor [³H] MDL105519 binding. The average ( standard deviation

of at least two experiments is reported. ^bSolubilities were measured in

the presence of NaCl, see Experimental Section. ^cSolubilities were

measured in the absence of NaCl, see Experimental Section. ^dRecorded

at pH 7.4, see Experimental Section. ^eThe methanesulfonate salt was

tested.

of >40%, and lends support to the hypothesis that low

oral bioavailability of 9b may have led to its inactivity in

the CCI model when dosed orally. Introduction of an R-methyl

group led to increases in oral bioavailability as evidenced by

the comparison of 9a (5% bioavailable) with 9f (30% bioavail-

able).

A logical extension of the work around the pyridyl lead was

to prepare five-membered ring heterocycles in place of the

pyridine ring. Hopefully, this would allow us to maintain and

potentially improve potency. A number of five-membered ring

heterocycles were prepared and tested (Table 2). In general,

these compounds showed improved in Vitro potency over the

R-pyridyl series (Table 1) but with lower aqueous solubilities.

Not surprisingly, the benzofused compounds 9j, 9k, and 9o had

higher log Ds and were much less soluble than their monocyclic

counterparts. The incorporation of an R-methyl substituent to

distort planarity and potentially improve solubility was also

attempted in this series. Interestingly, in the benzofuran case

(9j versus 9k) this did not lead to an increase in aqueous

solubility and had no impact on binding affinity (9j, K_i) 44

nM, 9k, K_i) 64 nM). In the 3-thiophene case (9p versus 9q)

introduction of the R-methyl was detrimental to the binding

affinity (43 nM compared with 135 nM).

Acetylenic Subseries. In the acetylenic series, the lead

phenyl-substituted compound, 9ae, demonstrated in ViVo activity

at 30 mg/kg in the CCI model (Table 5). This initial compound

possessed very good binding affinity (K_i) 21 nM, Table 4)

but very poor aqueous solubility (0.0012 mg/mL). In a strategy

similar to that used in the previous subseries, we attempted to

improve aqueous solubility by the incorporation of an R-methyl

One intriguing observation in this group of compounds

concerns in ViVo activity in the CCI model, Table 5. Interest-

ingly, all three thiophenes tested (9n, 9p, and 9r) were inactive

at the doses surveyed (15 or 30 mg/kg tid). In contrast, two of

3118 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 13

Table 5. In ViVo Data

Bare et al.

^aDosing frequency tid. ^bDosing frequency qid. ^cBased on the HTBLA data, the AUC for 9b was 4.3, compared to 12.1 for 9a. Because of the poor oral

exposure in this model, detailed oral bioavailabilty experiments were not done. Nonetheless, the compound was tested in the CCI model at the top dose and

found to be inactive. ^dReported data are statistically significant compared to vehicle control. Gabapentin was used every 2 months as a positive control.

^eData shown for one experiment. NA ) Not active. ND ) Not determined.

group. Direct comparison of the R-methyl phenyl acetylene 9af

with 9ae led to a solubility improvement of 2 orders of

magnitude at the expense of a slight decrease in binding potency

(Table 4). Surprisingly, the R-methylated 9af was void of

activity in the CCI model when tested at 15 mg/kg. The terminal

acetylene compound 9ag demonstrated that the phenyl substitu-

AntinociceptiVe NMDA Glycine-Site Antagonists

Journal of Medicinal Chemistry, 2007, Vol. 50, No. 13 3119

another 2.5 h, the reaction mixture was allowed to cool to rt and

potassium tert-butoxide (1.56 g, 13.9 mmol) was added in one

portion. A precipitate formed and the resulting mixture was refluxed

for 1.5 h. The mixture was cooled to rt and filtered to separate the

solids, which were washed with tert-butanol and Et₂O. The solids

were dissolved in water and acidified with 1 N H₂SO₄to form a

precipitate. The resulting mixture was extracted with CH₂Cl₂, and

the combined extracts were washed with brine and water, dried

over MgSO₄, filtered, and concentrated to give a green solid.

Recrystallization of this material from MeOH provided 4 (1.15 g,

47%) as an off-white solid, mp 232-233 °C. Anal. (C₁₃H₁₀-

ClNO₅): C, H, N.

3-Carbomethoxy-7-chloro-4-hydroxyquinoline-2-carboxylic

Acid (5). To a stirred suspension of dimethyl 7-chloro-4-hydrox-

yquinoline-2,3-dicarboxylate (1.0 g, 3.38 mmol) in H₂O (20 mL)

was added an aqueous solution of NaOH (0.27 g, 6.75 mmol). Upon

addition, the suspension dissolved. The reaction mixture was

warmed to 60 °C for 1 h. After this time the reaction was cooled

to rt and acidified with concentrated HCl. The product was then

extracted into Et₂O and EtOAc. The organic extracts were dried

over MgSO₄, filtered, and concentrated in Vacuo to provide the

title compound as a solid (900 mg). This material was purified by

recrystallization employing an EtOAc/hexane cosolvent system to

provide the title compound (571 mg, 60%) as a white solid; mp

296 °C (dec). Anal. (C₁₂H₈NO₅Cl‚ 0.45 CH₃CO₂CH₂CH₃‚0.10

H₂O): C, H, N.¹H NMR (300 MHz, DMSO-d₆): δ 3.90 (s, 3H);

7.28 (dd, J ) 8.7, 1.8 Hz, 1H); 7.92 (d, J ) 1.8 Hz, 1H); 8.22 (d,

J ) 8.7 Hz, 1H).

3-Carbomethoxy-2-pyrrolidinocarbamide-7-chloro-4-hydrox-

yquinoline (6). To a suspension of 3-carbomethoxy-7-chloro-4-

hydroxyquinoline-2-carboxylic acid 5 (2.25 g, 8.0 mmol) in THF

(20 mL) at ambient temperature under a N₂atmosphere were added

DCC (1.65 g, 8.0 mmol) and pyrrolidine (0.596 g, 8.4 mmol). The

reaction was stirred at rt for 15 h after which time the byproduct

urea was removed via filtration. The desired product was purified

via flash column chromatography on silica gel employing 5%

MeOH in CHCl₃to provide the title compound (2.52 g, 94.3%) as

a tan solid, mp ) 215 °C. ¹H NMR (300 MHz, DMSO-d₆): δ 1.80-

1.96 (m, 4H); 3.27-3.33 (m, 2H); 3.40-3.49 (m, 2H); 3.69 (s,

3H); 7.47 (dd, 1H, J ) 8.8, 2.0 Hz); 7.60 (d, 1H, J ) 1.8 Hz);

8.12 (d, J ) 8.7 Hz, 1H).

7-Chloro-4-oxo-2-(pyrrolidinylcarbonyl)hydroquinoline-3-

carboxylic Acid (7). To a suspension of 3-carbomethoxy-2-

pyrrolidinocarbamide-7-chloro-4-hydroxyquinoline 6 (2.52 g, 7.5

mmol) in deionized H₂O (40 mL) was added dropwise a solution

(20 mL) of aqueous KOH (882 mg, 15.75 mmol). Upon complete

addition, the reaction was warmed to 60 °C. After 3 h, the reaction

was filtered to remove a small amount of insoluble material. The

filtrate was then acidified to pH ) 1 which yielded a white

precipitate. The solid was isolated by vacuum filtration, washed

with H₂O, and dried at 30 °C in Vacuo for 16 h. This provided the

title compound (1.5 g, 64%) as a white solid, mp 225-228 °C. ¹H

NMR (30 MHz, DMSO-d₆): δ 1.83-1.98 (m, 4H).; 3.17-3.19

(m, 2H); 3.52-3.57 (m, 2H); 7.64 (d, 1H, J ) 8.7); 7.77 (s, 1H);

8.28 (d, J ) 8.8 Hz, 1H).

ent in 9ae was important, as deletion of this phenyl moiety led

to an approximately 10-fold reduction in binding affinity and a

loss of oral activity. However, this modification led to an

increase in aqueous solubility and reduction of lipophilicity.

Acetylenic heteroaryl analogues were also prepared. Potencies

and aqueous solubilities were analogous to the phenyl-

substituted compounds with the 2- and 3-thiophene derivatives

exhibiting single-digit nanomolar binding affinities.

Conclusion

The strategy to optimize binding potency and aqueous

solubility in the pyridazinoquinolinetriones has led to NMDA

glycine-site antagonists with oral activity in the CCI model of

neuropathic pain. Within all subseries, compounds were found

with improved aqueous solubility over the starting point without

substantial loss in binding affinity. Our strategy to enhance

aqueous solubility was aimed at enhancement of oral bioavail-

ability, which would afford oral activity in the CCI model.

However, metabolic stability, which would drastically affect the

oral bioavailability of these compounds, was not assessed. In

general, compounds with good solubility, potency and oral

bioavailability proved to be active in the CCI model (e.g., 9d,

9h, 9s, 9j). However, there are some compounds that did not

fit this hypothesis. For example, compound 9ab has relatively

poor oral bioavailability, but is active in the CCI model. Another

example is 9e, a compound with good oral bioavailability, but

poor in Vitro activity. Although it would be expected that this

compound would not be active, it is active at the highest dose

tested. A possible explanation for compounds that show these

disconnects would be the generation of an active metabolite

with a different potency or PK profile. For example, in the case

of 9e, racemization, even a small amount, could contribute to

some CCI activity. Although interesting from a scientific

perspective, we chose not to follow-up with these exceptions,

but to put our efforts in profiling the best compounds that met

our criteria. From the three starting points, several promising

compounds were identified. Four compounds (9d, 9h, 9s, 9j)

within the R-alkylheteroaryl subseries were found to have

improved oral exposures over 9a while maintaining activity in

the CCI model. Two compounds (9y and 9ab) were identified

from the ester subseries having CCI activity and improved

aqueous solubility over the parent compound 9u. The most

efficacious compound in the ester subseries, 9ab, was found to

have poor oral bioavailability. In the acetylenic subseries,

although compounds with potent binding affinities were identi-

fied, none were found to be active in the CCI model apart from

the starting compound 9ae.

Experimental Section

1

Chemistry. H NMR spectra were obtained at 300 MHz using

a Bruker DPX300 spectrometer and were referenced to TMS.

Elemental analyses (C, H, N) were performed on an Exeter

Analytical CE-440 elemental analyzer, and all compounds are

within 0.4% of theory unless otherwise indicated; the data can be

found in the Supporting Information. For compounds that do not

have elemental analysis data, the results of HPLC-MS in two diverse

chromatographic conditions can be found in the Supporting

Information. Unless otherwise noted, all materials were obtained

commercially and used without further purification.

Compound 7 (7-Chloro-4-oxo-2-(pyrrolidinylcarbonyl)hyd-

roquinoline-3-carboxylic Acid). Dimethyl 7-Chloro-4-hydrox-

yquinoline-2,3-dicarboxylate (4). A stirred mixture of methyl

2-amino-4-chlorobenzoate (2.50 g, 13.5 mmol) and dimethyl

acetylenedicarboxylate (2.05 g, 14.4 mmol) in tert-butanol (22 mL)

was refluxed for 7 h under a N₂atmosphere. After adding additional

dimethyl acetylenedicarboxylate (1.16 g, 8.13 mmol) and refluxing

General Procedures. Coupling of Compound 7 to Hydrazines.

Method A. To a stirred mixture of 7-chloro-4-oxo-2-(pyrrolidi-

nylcarbonyl)hydroquinoline-3-carboxylic acid (7, 1 equiv) and dry

THF (15 mL/mmol) under N₂was added 1-cyclohexy1-3-(2-

morpholinoethyl)carbodiimide metho-p-toluenesulfonate (CMC,

1.5-1.6 equiv) in portions over 10 min. After the bright yellow

reaction mixture was stirred for an additional 20-60 min, a solution

of the BOC-protected hydrazine (1.3 equiv) in THF (5.9 mL/mmol)

was rapidly added and the mixture was stirred overnight. The

reaction mixture was filtered, and the filter cake was washed with

CH₂Cl₂(or THF). The filtrate and washings were combined, washed

with H₂O, dried over Na₂SO₄, filtered, and concentrated under

reduced pressure to give the product typically as a solid or foam.

The solid was triturated with Et₂O and then filtered. The filter cake

was dried at 45 °C in Vacuo to give the desired product as a solid.

3120 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 13

Bare et al.

When required, the product was further purified by chromatography

on silica gel using 1:1 hexanes:EtOAc or 95:5 CH₂Cl₂:MeOH as

eluent.

Et₂O or MeOH, suspended in MeOH, sonicated for 30 min, and

then filtered. The collected solids were sonicated two more times

and then air-dried or dried in Vacuo at 30-45 °C to provide the

desired final product 9 as a solid.

Method B. To a stirred mixture of 7-chloro-4-oxo-2-(pyrrolidi-

nylcarbonyl)hydroquinoline-3-carboxylic acid (7, 1 equiv) in THF

(13 mL/mmol)) was added 1-cyclohexy1-3-(2-morpholinoethyl)-

carbodiimide metho-p-toluenesulfonate (CMC, 1.2 equiv), and the

reaction was stirred for 5 min. To this mixture was added dropwise

a solution of the BOC-protected hydrazine (1.0-1.3 equiv) and

DMAP (0.17 equiv) in THF (2.6 mL/mmol). The mixture was

stirred at rt for 45 min and then refluxed for 3 to 18 h. The cooled

solution was filtered, and the collected insolubles were washed with

CH₂Cl₂(2×). The combined filtrate and washes were concentrated

in Vacuo to dryness. The resultant yellow foam was subjected to

chromatography on silica gel using CHCl₃:MeOH or CH₂Cl₂:MeOH

(usually 95:5 or 90:10) as eluent to give the desired product as a

solid or a foam.

Coupling of Aryl Halides to Compound 8. Method C. A

solution of the appropriate aryl iodide or bromide (1.9 equiv), bis-

(triphenylphosphine)palladium(II) chloride (10 mol %), copper(I)

iodide (0.18-0.20 equiv), and 2,6-di-tert-butyl-4-methylphenol

(0.20-0.25 equiv) in CH₂Cl₂(15 mL/mmol) was treated sequen-

tially with triethylamine (2.4 equiv) and N′-[7-chloro-4-oxo-2-

(pyrrolidine-1-carbonyl)-1,4-dihydroquinoline-3-carbonyl]-N′-(1-

methyl-prop-2-ynyl)-hydrazinecarboxylic acid tert-butyl ester (1

equiv) or N-[(tert-butoxy)carbonylamino][7-chloro-4-oxo-2-(pyr-

rolidinylcarbonyl)(3-hydroquinolyl)]-N-prop-2-ynylcarboxamide (1

equiv). The reaction was stirred at rt under N₂overnight. The

reaction mixture was concentrated to a thick brown oil and purified

by flash chromotography on silica gel using a gradient of 100:0 to

90:10 CH₂Cl₂:MeOH. The desired product was generally obtained

as a solid or foam.

Preparation of Noncommercially Available Hydrazines. Prepa-

ration from the Corresponding Halide. Method H. To a stirred

solution of tert-butyl carbazate (4.9-5.6 equiv) in dry DMF (1.2-

1.6 mL/mmol)) under N₂was added Et₃N (2.8-3.2 equiv) followed

by the appropriate chloride or bromide (1 equiv; note: both the

free bases and the hydrochloride salts were employed). The reaction

mixture was stirred at rt for 1 h, heated at 75 °C for 5 h, and allowed

to cool to rt. The reaction mixture was diluted with H₂O and the

resulting mixture extracted with EtOAc (4×). The combined EtOAc

extracts were concentrated under reduced pressure, and the residue

was dissolved in Et₂O. The resulting solution was washed succes-

sively with H₂O (3×) and brine (1×). The aqueous layer was

checked for product using TLC and if necessary extracted with

EtOAc until it no longer contained product. The combined organic

layers were washed with brine and then dried over Na₂SO₄. The

Na₂SO₄was removed by filtration, and the filtrate was concentrated

under reduced pressure to give the crude BOC-protected hydrazine.

This product was typically purified by flash chromatography on

silica gel eluting with 1:1 hexane:EtOAc to give the desired product

generally as a foam or solid. In some cases, the product was

successfully purified by trituration in 1:1 hexanes:Et₂O.

Preparation of the Hydrazones from the Corresponding

Aldehyde or Ketone. Method I. To a stirred solution of tert-butyl

carbazate (1 equiv) in THF (2.4 mL/mmol) was added the

appropriate aldehyde or ketone (1 equiv), followed by 3-10 drops

of concentrated HCl. After 1-6 h, the reaction turned cloudy, and

the solvent was removed in Vacuo. The resultant solid was triturated

with hexanes and filtered to give the hydrazone as a solid.

Preparation of the Hydrazines from the Corresponding

Hydrazone. Method J. The hydrazone (1 equiv) was dissolved in

MeOH (9.4 mL/mmol) and placed in a Parr shaker bottle. To this

was added 10% Pd/C (100 mg/mmol) and the reaction was

hydrogenated at 40 psi for 24 h. The mixture was filtered through

diatomaceous earth and washed with MeOH (3×). The combined

filtrate and washes were concentrated in Vacuo. The resultant BOC-

protected hydrazines were typically triturated in 90:10 hexanes:

CH₂Cl₂and isolated by filtration or were used in the subsequent

reaction without further purification.

Cyclization of Compounds 8 to Final Products 9. Method D.

To a stirred mixture of compound 8 (1.0 equiv) and dry THF (20

mL/mmol) under N₂was added methanesulfonic acid (35-40 equiv)

in one portion. The mixture was stirred overnight and then filtered

to separate the solids. The collected solids were successively washed

with THF (2×), MeOH (2×), and Et₂O (1×). The filter cake was

then suspended in MeOH and the resulting mixture sonicated for

20 min. The solids were collected by filtration and washed with

MeOH (2 times) and Et₂O (1 time) and then dried at 45 °C in Vacuo

to give the desired final product 9 as a solid.

Preparation of the Hydrazines from the Hydrazinecarboxylic

Acid tert-Butyl Ester. Method K. The required hydrazinecarboxy-

lic acid tert-butyl ester (1 equiv) in MeOH (5 mL/mmol) was added

NaCNBH₃(5 equiv) followed by enough acetic acid to adjust to

pH 3. This solution was heated to 65 °C. At 1 and 3 h, more

NaCNBH₃was added (ca. 180 mg/mmol each time). After a reaction

time of 4 h, the reaction was then cooled to rt and diluted with

H₂O, and the MeOH was removed under reduced pressure. The

remaining material was diluted with EtOAc and washed with

saturated aqueous NaHCO₃, H₂O, and brine and then dried over

Na₂SO₄. The mixture was filtered and concentrated to give the title

compound as an oil or a solid. When required, the material was

purified by silica gel chromatography using 4:1 hexanes:EtOAc as

the eluent.

Method E. To a stirred mixture of compound 8 (1.0 equiv) and

dry THF (20 mL/mmol) under N₂was added methanesulfonic acid

(35-40 equiv) in one portion. The mixture was stirred overnight,

the volatiles were removed in Vacuo, and the resultant oil was

poured onto crushed ice. A fine precipitate formed which was then

isolated by filtration. The material was washed with water and Et₂O,

suspended in 1:1 Et₂O:MeOH, sonicated for 15 min, and then

filtered. The collected solids were again suspended in 1:1 Et₂O:

MeOH, sonicated for 15 min, filtered, and then washed with the

same solvent system or Et₂O. The material was dried at 55 °C in

Vacuo to give the desired final product 9 as a solid.

Method F. To a stirred mixture of compound 8 (1.0 equiv) and

dry THF (20 mL/mmol) under N₂was added methanesulfonic acid

(35-40 equiv) in one portion. The mixture was stirred overnight.

The volatiles were removed in Vacuo, and to the resultant oil was

added Et₂O. The mixture was stirred vigorously for 10 min and

then allowed to stand until two layers formed. The top layer was

decanted away to leave an oil. To this oil was added water, and

the mixture was stirred until a fine precipitate formed. This

precipitate was filtered to give a solid. This material was washed

with Et₂O, sonicated twice in 7:1 Et₂O:MeOH for 15 min, and

filtered. The insoluble materials were collected, washed with the

same solvent system and dried at 55 °C in Vacuo to give the desired

final product 9 as a solid.

Specific Examples. Compound 9a. 7-Chloro-4-hydroxy-2-(4-

pyridylmethyl)-1,2,5,10-tetrahydropyridazino[4,5-b]quinoline-1,10-

dione methanesulfonate.

(tert-Butoxy)-N-[(4-pyridylmethyl)amino]carboxamide. The

title compound was prepared from tert-butyl carbazate (174 g, 1.36

mol) and 4-picolyl chloride hydrochloride (40.0 g, 0.243 mol)

1

according to Method G as an off-white foam (24.46 g, 45%). H

NMR (300 MHz, DMSO-d₆): δ 1.36 (s, 9H); 3, 90 (d, 2H, J )

4.0 Hz); 5, 04 (d, 1H, J ) 4.0 Hz); 7.34 (d, 1H, J ) 4.5 Hz); 8.48

(d, 1H, J ) 4.5 Hz).

Method G. To a stirred mixture of compound 8 (1.0 equiv) and

dry THF (20 mL/mmol) under N₂was added methanesulfonic acid

(35-40 equiv) in one portion. The mixture was stirred overnight

and then poured into ice-water. The resulting mixture was filtered,

and the collected solids were successively rinsed with water and

N-[(tert-butoxy)carbonylamino][7-chloro-4-oxo-2-(pyrrolidi-

nylcarbonyl)(3-hydroquinolyl)]-N-(4-pyridylmethyl)carboxam-

ide. The title compound was prepared from 7-chloro-4-oxo-2-

(pyrrolidinylcarbonyl)hydroquinoline-3-carboxylic acid (7) (24.29

g, 75.73 mmol) and (tert-butoxy)-N-[(4-pyridylmethyl)amino]-

AntinociceptiVe NMDA Glycine-Site Antagonists

Journal of Medicinal Chemistry, 2007, Vol. 50, No. 13 3121

carboxamide (22.0 g, 98.5 mmol) according to Method A as a

yellow powder (24.3 g, 61%).

Compound 9d. (-)-7-Chloro-4-hydroxy-2-(2-pyridylethyl)-

1,2,5,10-tetrahydropyridazino[4,5-b]quinoline-1,10-dione Meth-

anesulfonate. N-((1Z)-1-Aza-2-(2-pyridyl)prop-1-enyl)(tert-butoxy)-

carboxamide. The title compound was prepared from tert-butyl

carbazate (2.18 g, 16.5 mmol) and 2-acetylpyridine (2.00 g, 16.5

7-Chloro-4-hydroxy-2-(4-pyridylmethyl)-1,2,5,10-tetrahydro-

pyridazino[4,5-b]quinoline-1,10-dione Methanesulfonate 9a. The

title compound was prepared from N-[(tert-butoxy)carbonylamino]-

[7-chloro-4-oxo-2-(pyrrolidinylcarbonyl)(3-hydroquinolyl)]-N-(4-

pyridylmethyl)carboxamide (24.0 g, 45.62 mmol) according to

Method D. The desired product was obtained as a yellow powder

1

mmol) according to Method I as a white solid (3.12 g, 80%). H

NMR (300 MHz, DMSO-d₆): δ 1.49 (s, 9H); 7.38 (dd, 1H, J )

4.8, 6.7 Hz); 7.94 (m, 1H); 7.99 (d, 1H, J ) 7.5 Hz); 8.58 (d, 1H,

J ) 4.2 Hz); 10.04 (s, 1H).

1

(12.1 g, 59%); mp >250 °C. H NMR (300 MHz, DMSO-d₆): δ

(()-(tert-Butoxy)-N-[(2-pyridylethyl)amino]carboxamide. The

title compound was prepared from N-((1Z)-1-aza-2-(2-pyridyl)prop-

1-enyl)(tert-butoxy)carboxamide (2.0 g, 8.5 mmol) according to

Method J. The compound formed an oil (ca. 1.8 g) and was used

in the following reaction without further purification. ¹H NMR (300

MHz, DMSO-d₆): δ 1.19 (d, 3H, J ) 6.6 Hz); 1.33 (s, 9H); 4.11

(m, 1H); 4.79 (m, 1H); 7.22 (m, 1H); 7.49 (d, 1H, J ) 7.8 Hz);

8.22 (m, 1H, J ) 1.5, 2.4 Hz); 8.49 (d, 1H, J ) 4.2 Hz).

(-)-(tert-Butoxy)-N-[(2-pyridylethyl)amino]carboxamide. The

racemic mixture was subjected to chiral HPLC preparatory chro-

matography using CHIRALPAK-AD column (5 cm × 50 cm).

Approximately 10 g was resolved giving 4.5 g of peak 1 (>99%

ee) and 4.7 g of peak 2 (98.6% ee) using acetonitrile as solvent.

Peak 1 (t_R) 5.07 min) had a (-) rotation and was identified as

the title compound. The other enantiomer was obtained as peak 2

(t_R) 6.15 min) with a (+) rotation. Characterization of Peak 1:

¹H NMR (300 MHz, DMSO-d₆): δ 1.19 (d, 3H, J ) 6.6 Hz); 1.33

(s, 9H); 4.11 (m, 1H); 4.79 (m, 1H); 7.22 (m, 1H); 7.49 (d, 1H, J

) 7.8 Hz); 8.22 (m, 1H, J ) 1.5, 2.4 Hz); 8.49 (d, 1H, J ) 4.2

2.32 (s, 3H), 5.36 (s, 2H); 7.49 (dd, 1H, J ) 8.1 Hz, J ) 2.1 Hz);

7.86 (d, 1H, J ) 6.6 Hz); 8.06 (d, 1H, J ) 2.1 Hz); 8.12 (d, 1H,

J ) 8.1 Hz); 8.82 (d, 1H, J ) 6.6 Hz); 12.6 (br s, 1H); 12.84 (br

s, 1H). Anal. (C₁₇H₁₁ClN₄O₃‚CH₃SO₃H‚0.8H₂O): C, H, N.

Compound 9b. 7-Chloro-4-hydroxy-2-(2-pyridylmethyl)-

1,2,5,10-tetrahydropyridazino[4,5-b]quinoline-1,10-dione Meth-

anesulfonate. (tert-Butoxy)-N-[(2-pyridylmethyl)amino]carbox-

amide. The title compound was prepared from tert-butyl carbazate

(174 g, 1.53 mol) and 2-picolyl chloride hydrochloride (54.0 g,

0.33 mol) according to Method H as an off-white solid (33.4 g,

45% yield). ¹H NMR (300 MHz, DMSO-d₆): δ 1.38 (s, 9H); 3.96

(d, 2H, J ) 4.0 Hz); 4.98 (d, 1H, J ) 4.0 Hz); 7.24 (dd, 1H, J )

7.8 Hz, J ) 7.8 Hz); 7.48 (d, 1H); 7.74 (dd,1H, J ) 7.5 Hz, J )

7.8 Hz); 8.32 (s, br, 1H); 8.47 (d, 1H, J ) 4.8 Hz).

N-[(tert-butoxy)carbonylamino][7-chloro-4-oxo-2-(pyrrolidi-

nylcarbonyl)(3-hydroquinolyl)]-N-(2-pyridylmethyl)carboxam-

ide. The title compound was prepared from 7-chloro-4-oxo-2-

(pyrrolidinylcarbonyl)hydroquinoline-3-carboxylic acid (7) (17.5 g,

54.7 mmol) and (tert-butoxy)-N-[(2-pyridylmethyl)amino]carboxa-

mide (16.5 g, 73.9 mmol) according to Method A as a light tan

powder (24.3 g, 61% yield).

20

Hz). [R]_D) -128.78, (c ) 0.49).

The (R)-configuration was assigned to (-)-(tert-butoxy)-N-[(2-

pyridylethyl)amino]carboxamide based on comparison to the chiral

HPLC of a chemical synthesized sample that started from an alcohol

of known configuration. The synthesis of this standard is described

below and is represented in Scheme 4.

7-Chloro-4-hydroxy-2-(2-pyridylmethyl)-1,2,5,10-tetrahydro-

pyridazino[4,5-b]quinoline-1,10-dione Methanesulfonate 9b. The

title compound was prepared from N-[(tert-butoxy)carbonylamino]-

[7-chloro-4-oxo-2-(pyrrolidinylcarbonyl)(3-hydroquinolyl)]-N-(2-

pyridylmethyl)carboxamide (24.0 g, 0.045 mol) according to

Method D. The desired product was obtained as an orange powder

A stirred solution of (R)-1-pyridin-2-yl-ethanol (3.53 g, 28.7

mmol)³²in CH₂Cl₂was cooled to 0 °C, and to this was added

methanesulfonyl chloride (3.37 mL, 4.99 g, 43.69 mmol) followed

by Et₃N (6.09 mL, 4.41 g, 43.6 mmol). The reaction was stirred at

0 °C for 1.5 h and then quenched with cold NaHCO₃. (It should be

noted that if the reaction is allowed to stir at rt for more than 2 h,

displacement of the mesylate can occur from the chloride ion which

results in a reduction of enantionselectivity). The organic layers

were separated and washed with NaCl (sat.) and then dried over

Na₂SO₄. The material was then used directly in the displacement

reaction. Crude mesylate (5.78 g, 28.7 mmol) was dissolved in DMF

(80 mL), and to this were added Hunigs base (7.51 mL, 5.51 g,

43.11 mmol) and tert-butyl carbazate (18.95 g, 143.7 mmol). The

reaction was heated at 90 °C for 6 h and then poured into ethyl

acetate (200 mL). The organic layers were washed with H₂O (150

mL) and NaCl (sat.). The material was concentrated and then

dissolved in 1/1 ether/hexanes (30 mL). The material was then

placed in a freezer overnight, and the resultant crystals were

collected. The recrystallization was repeated to give pure material

than matched in all respects the data for the (-) enantiomer

described above as Peak 1 (1.23 g, 18%).

1

(12.1 g, 59%), mp >300 °C. H NMR (300 MHz, DMSO-d₆): δ

2.33 (s, 3H), 5.35 (s, 2H); 7.46 (d, 1H, J ) 8.7 Hz); 7.64 (d, 1H,

J ) 7.8 Hz); 7.68 (dd, 1H, J ) 4.8 Hz, J ) 6.6 Hz); 8.02 (s, 1H);

8.14 (d, 1H, J ) 8.7 Hz); 8.19 (dd, 1H, J ) 6.6 Hz, J ) 7.8 Hz);

8.73 (d, 1H, J ) 4.8 Hz); 10.06 (s, br, 1H); 12.84 (s, br, 1H). Anal.

(C₁₇H₁₁ClN₄O₃‚CH₃SO₃H): C, H; N: calcd, 12.43; found, 12.01.

Compound 9c. 7-Chloro-4-hydroxy-2-(3-pyridylmethyl)-1,2,5,-

10-tetrahydropyridazino[4,5-b]quinoline-1,10-dione Methane-

sulfonate. (tert-Butoxy)-N-[3-pyridylmethyl)amino]carboxamide.

The title compound was prepared from tert-butyl carbazate (203.6

g, 1.54 mol) and 3-picolyl chloride hydrochloride (50.0 g, 0.30 mol)

1

according to Method H as an off-white solid (23.3 g, 34%). H

NMR (300 MHz, DMSO-d₆): d 1.36 (s, 9H); 3.88 (d, 2H, J ) 4.0

Hz); 4.96 (d, 1H, J ) 4.0 Hz); 7.33 (dd, 1H, J ) 7.7 Hz, J ) 4.8

Hz); 7.71 (d, 1H, J ) 7.7 Hz); 7.44 (d, 1H, J ) 4.7 Hz); 8.49 (s,

1H).

N-[(tert-butoxy)carbonylamino][7-chloro-4-oxo-2-(pyrrolidi-

nylcarbonyl)(3-hydroquinolyl)]-N-(3-pyridylmethyl)carboxam-

ide. The title compound was prepared from 7-chloro-4-oxo-2-

(pyrrolidinylcarbonyl)hydroquinoline-3-carboxylic acid (7) (20 g,

62.4 mmol) and (tert-butoxy)-N-[(3-pyridylmethyl)amino]carboxa-

mide (20.9 g, 93.6 mmol) according to Method A as an off-white

powder (32.8 g, 100%).

(-)-N-[(tert-Butoxy)carbonylamino][7-chloro-4-oxo-2-(pyrro-

lidinylcarbonyl)(3-hydroquinolyl]-N-(2-pyridylethyl)carboxam-

ide. The title compound was prepared from 7-chloro-4-oxo-2-

(pyrrolidinylcarbonyl)hydroquinoline-3-carboxylic acid (7) (2.82 g,

8.79 mmol) and (-)-(tert-butoxy)-N-[(2-pyridylethyl)amino]car-

boxamide (2.25 g, 9.49 mmol) according to Method B as a yellow

7-Chloro-4-hydroxy-2-(3-pyridylmethyl)-1,2,5,10-tetrahydro-

pyridazino[4,5-b]quinoline-1,10-dione Methanesulfonate 9c. The

title compound was prepared from N-[(tert-butoxy)carbonylamino]-

[7-chloro-4-oxo-2-(pyrrolidinylcarbonyl)(3-hydroquinolyl)]-N-(3-

pyridylmethyl)carboxamide (32.8 g, 62 mmol) according to Method

D. The desired product was obtained as a white solid (19.4 g, 66%);

20

foam (4.6 g, 97%). [R]_D) -30.61, (c ) 0.49, MeOH).

(-)-7-Chloro-4-hydroxy-2-(2-pyridylethyl)-1,2,5,10-tetrahy-

dropyridazino[4,5-b]quinoline-1,10-dione Methanesulfonate 9d.

The title compound was prepared from (-)-N-[(tert-butoxy)-

carbonylamino][7-chloro-4-oxo-2-(pyrrolidinylcarbonyl)(3-hydro-

quinolyl]-N-(2-pyridylethyl)carboxamide (4.62 g, 8.55 mmol) ac-

1

mp >300 °C. H NMR (300 MHz, DMSO-d₆): d 2.33 (s, 3H);

1

5.29 (s, 2H)); 7.46 (dd, 1H, J ) 9.0 Hz, J ) 2.1 Hz); 7.94 (dd, 1H,

J ) 9.0 Hz, J ) 5.6 Hz); 8.04 (d, 1H, J ) 1.8 Hz); 8.16 (d, 1H J

) 8.7 Hz); 8.37 (d, 1H, J ) 8.1 Hz); 8.82 (d, 1H J ) 4.8 Hz); 8.89

(s, 1H). Anal. (C₁₇H₁₁ClN₄O₃‚CH₃SO₃H‚H₂O): C, H, N.

cording to Method F as an off-white powder (1.70 g, 56%); H

NMR (300 MHz, DMSO-d₆): δ 1.77 (d, 3H, J ) 6.9 Hz); 2.34 (s,

3H, CH₃SO₃H); 6.41 (q, 1H, J ) 6.9 Hz); 7.44 (d, 1H, J ) 8.7

Hz); 7.80 (s, 1H); 7.87 (m, 2H); 7.96 (m, 1H); 8.02 (d, 1H, J )

3122 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 13

Bare et al.

8.7 Hz); 8.43 (app t, 1H, J ) 7.5 Hz); 8.86 (d, 1H, J ) 5.1 Hz);

11.98 (s, 1H); 12.80 (s, 1H). [R]_D²⁰) -175.28, (c ) 0.49, MeOH).

The enantiomeric excess was determined to be >95% by use of a

chiral shift reagent (N-methylephedrine or d₁₁-(S-(+)-2,2,2-trifluoro-

1-(9-anthryl)ethanol)). Anal. (C₁₈H₁₃ClN₄O₃‚CH₃SO₃H‚H₂O): C,

H, N.

mixture was filtered and material worked up and purified as usual

to afford the title compound as a yellow foam (2.04 g, 73%).

(()-7-Chloro-4-hydroxy-2-(4-pyridylethyl)-1,2,5,10-tetrahy-

dropyridazino[4,5-b]quinoline-1,10-dione Methanesulfonate 9f.

The title compound was prepared from (()-N-[(tert-butoxy)-

carbonylamino][7-chloro-4-oxo-2-(pyrrolidinylcarbonyl)(3-hydro-

quinolyl]-N-(4-pyridylethyl)carboxamide (2.04 g, 3.8 mmol) ac-

cording to Method E as an off-white powder (0.715 g, 40%); mp

245-248 °C; ¹H NMR (300 MHz, DMSO-d₆): δ 1.74 (d, 3H, J )

6.9 Hz); 2.31 (s, 3H, CH₃SO₃H); 6.24 (q, 1H, J ) 6.9 Hz); 7.45

(dd, 1H, J ) 1.8, 8.7 Hz); 7.86 (m, 2H); 8.05 (d, 1H, J ) 1.8 Hz);

8.14 (d, 1H, J ) 8.7 Hz); 8.82 (m, 2H); 12.03 (s, 1H); 12.71 (s,

1H). Anal. (C₁₈H₁₃ClN₄O₃‚CH₃SO₃H‚0.8 H₂O): C, H, N.

Compound 9g. (()-7-Chloro-4-hydroxy-2-(4-pyridylpropyl)-

1,2,5,10-tetrahydropyridazino[4,5-b]quinoline-1,10-dione So-

dium Methanesulfonate. (()-(tert-Butoxy)-N-[(4-pyridylpropyl)-

amino]carboxamide. To a stirred solution of N-1-aza-2-(4-

pyridyl)vinyl)(tert-butoxy)carboxamide (2.0 g, 9.40 mmol) in THF

at 0 °C was slowly added EtMgBr (18.0 mL, 18.8 mmol, 2 M

solution in THF). This solution was stirred 4 h during which time

it was warmed to rt. The volatiles were removed, and the reaction

was carefully quenched with saturated NH₄Cl solution (30 mL).

The aqueous layer was extracted with EtOAc (300 mL), and then

the organic layers washed with brine. The organic layer was then

dried over MgSO₄and the solution concentrated in Vacuo. The

material was chromatographed (SiO₂, EtOAc as eluent) to give the

title compound as a yellow oil (400 mg, 18%). ¹H NMR (300 MHz,

DMSO-d₆): δ 0.73 (t, 3H, J ) 7.5 Hz); 1.44 (m, 2H); 3.92 (br s,

1H); 4.78 (m, 1H); 7.31 (m, 2H); 8.48 (m, 2H).

Compound 9e. (+)-7-Chloro-4-hydroxy-2-(2-pyridylethyl)-

1,2,5,10-tetrahydropyridazino[4,5-b]quinoline-1,10-dione Meth-

anesulfonate. (+)-(tert-Butoxy)-N-[(2-pyridylethyl)amino]car-

boxamide. HPLC preparatory chromatography using CHIRALPAK-

AD was described above for isolation of both the (+) and (-)

enantiomers. Peak 2 was also isolated (t_R) 6.15 min) with a (+)

rotation. Characterization of Peak 2: ¹H NMR (300 MHz, DMSO-

d₆): δ 1.19 (d, 3H, J ) 6.6 Hz); 1.33 (s, 9H); 4.11 (m, 1H); 4.79

(m, 1H); 7.22 (m, 1H); 7.49 (d, 1H, J ) 7.8 Hz); 8.22 (m, 1H, J

) 1.5, 2.4 Hz); 8.49 (d, 1H, J ) 4.2 Hz). [R]_D²⁰) +134.45, (c )

0.49, MeOH). Similar to the (-) enantiomer, a synthetic sample

was prepared from (S)-1-pyridin-2-yl-ethanol (3.53 g, 28.7 mmol)³²

to give a compound matching in all respects Peak 2. This was

assigned the (R)-configuration based on the known chirality of the

(S)-alcohol and the inversion that took place in the S_N2 displacement

reaction.

(+)-N-[(tert-Butoxy)carbonylamino][7-chloro-4-oxo-2-(pyrro-

lidinylcarbonyl)(3-hydroquinolyl]-N-(2-pyridylethyl)carboxam-

ide. The title compound was prepared from 7-chloro-4-oxo-2-

(pyrrolidinylcarbonyl)hydroquinoline-3-carboxylic acid (7) (2.57 g,

8.03 mmol) and (+)-(tert-butoxy)-N-[(2-pyridylethyl)amino]car-

boxamide (2.0 g, 8.43 mmol) according to Method B as a yellow

20

foam (4.0 g, 94%). [R]_D) +54.27, (c ) 0.51, MeOH).

(+)-7-Chloro-4-hydroxy-2-(2-pyridylethyl)-1,2,5,10-tetrahy-

dropyridazino[4,5-b]quinoline-1,10-dione Methanesulfonate 9e.

The title compound was prepared from (+)-N-[(tert-butoxy)-

carbonylamino][7-chloro-4-oxo-2-(pyrrolidinylcarbonyl)(3-hydro-

quinolyl]-N-(2-pyridylethyl)carboxamide (4.0 g, 7.40 mmol) ac-

cording to Method F except that 12:1 Et₂O:MeOH was used as the

solvent system. The title compound was obtained as an off-white

(()-N-[(tert-Butoxy)carbonylamino][7-chloro-4-oxo-2-(pyrro-

lidinylcarbonyl)(3-hydroquinolyl]-N-(4-pyridylpropyl)carboxa-

mide. The title compound was prepared from 7-chloro-4-oxo-2-

(pyrrolidinylcarbonyl)hydroquinoline-3-carboxylic acid (7) (1.22 g,

3.82 mmol) and (()-(tert-butoxy)-N-[(4-pyridylpropyl)amino]car-

boxamide (0.96 g, 3.82 mmol) according to Method B. An

additional portion of CMC (0.300 g) was added after 1 h, and the

mixture was refluxed overnight. The usual workup and purification

provided the desired material as a yellow foam (1.72 g, 81%).

1

powder (1.31 g, 48%); H NMR (300 MHz, DMSO-d₆): δ 1.77

(d, 3H, J ) 6.9 Hz); 2.34 (s, 3H, CH₃SO₃H); 6.41 (q, 1H, J ) 6.9

Hz); 7.44 (d, 1H, J ) 8.7 Hz); 7.82 (m, 2H); 7.91 (d, 1H, J ) 7.8

Hz); 8.02 (d, 1H, J ) 8.7 Hz); 8.39 (app t, 1H, J ) 7.5 Hz); 8.84

(d, 1H, J ) 5.1 Hz); 11.98 (s, 1H); 12.80 (s, 1H). [R]_D²⁰) +173.86,

(c ) 0.49, MeOH). The enantiomeric excess was determined to be

>95% by chiral shift reagent (N-methylephedrine or d₁₁-(S-(+)-

2,2,2-trifluoro-1-(9-anthryl)ethanol)). Anal. (C₁₈H₁₃ClN₄O₃‚CH₃-

SO₃H‚0.9H₂O): H, N; C: calcd 47.43; found 47.84.

(()-7-Chloro-4-hydroxy-2-(4-pyridylpropyl)-1,2,5,10-tetrahy-

dropyridazino[4,5-b]quinoline-1,10-dione Sodium Methane-

sulfonate 9g. To a stirred solution of (()-N-[(tert-butoxy)-

carbonylamino][7-chloro-4-oxo-2-(pyrrolidinylcarbonyl)(3-

hydroquinolyl]-N-(4-pyridylpropyl)carboxamide (1.72 g, 1.5 mmol)

in THF (60 mL) was added methanesulfonic acid (9 mL), and the

reaction was stirred overnight. The volatiles were removed in Vacuo,

and the resultant oil was poured onto crushed ice. To this mixture

was carefully added 10 N NaOH until a solid precipitate formed.

The solution was filtered to give an orange solid. This material

was washed with Et₂O and then sonicated in 40 mL of 3:1 Et₂O:

MeOH for 15 min. The material was washed with Et₂O to give the

title compound (0.557 g, 28%) as an off-white powder; mp >265

Compound 9f. (()-7-Chloro-4-hydroxy-2-(4-pyridylethyl)-

1,2,5,10-tetrahydropyridazino[4,5-b]quinoline-1,10-dione Meth-

anesulfonate. N-((1Z)-1-aza-2-(4-pyridyl)prop-1-enyl)(tert-butoxy)-

carboxamide. The title compound was prepared from tert-butyl

carbazate (2.18 g, 16.5 mmol) and 4-acetylpyridine according to

1

Method I as a white solid (3.88 g, 100%); H NMR (300 MHz,

1

DMSO-d₆): δ 1.47 (s, 9H); 7.55 (dd, 2H, J ) 1.5, 4.5 Hz); 7.97

(s, 1H); 7.99 (d, 2H, J ) 4.5 Hz); 11.22 (s, 1H).

°C. H NMR (300 MHz, DMSO-d₆): δ 0.88 (t, 3H, J ) 7.2 Hz);

2.16 (m, 2H); 2.31 (s, 3H, CH₃SO₃H); 5.98 (dd, 1H, J ) 5.7, 9.46

Hz); 7.44 (m, 3H); 8.05 (d, 1H, J ) 1.5 Hz); 8.15 (d, 1H, J ) 8.7

Hz); 8.58 (m, 2H); 12.04 (s, 1H); 12.69 (s, 1H). Anal. (C₁₈H₁₃-

ClN₄O₃‚2CH₃SO₃Na‚H₂O): C, H, N.

(()-(tert-Butoxy)-N-[(4-pyridylethyl)amino]carboxamide. The

title compound was prepared from N-((1Z)-1-aza-2-(4-pyridyl)prop-

1-enyl)(tert-butoxy)carboxamide (2.0 g, 8.51 mmol) according to

1

Method J as a white solid (1.34 g, 66%). H NMR (300 MHz,

Compound 9h. 7-Chloro-4-hydroxy-2-(pyrazin-2-ylmethyl)-

1,2,5,10-tetrahydropyridazino[4,5-b]quinoline-1,10-dione Meth-

anesulfonate. 2-Chloromethylpyrazine. A solution of 2-meth-

ylpyrazine (1.0 mL, 22 mmol) in CCl₄(80 mL) was treated with

N-chlorosuccinimide (4.27 g, 31.5 mmol) and benzoyl peroxide

(0.26 g, 1.1 mmol). The mixture was heated to reflux for 7 h and

then cooled to rt. The solids were filtered through diatomaceous

earth and washed with CH₂Cl₂. The filtrate was washed with

aqueous sodium thiosulfate (sat., 1×), aqueous NaHCO₃(sat., 1×),

water (1×), and aqueous NaCl (sat., 1×). The organic layer was

dried over Na₂SO₄, filtered, concentrated under reduced pressure,

and used directly in the following reaction. (Contains 5-10% of

DMSO-d₆): δ 1.19 (d, 3H, J ) 6.6 Hz); 1.34 (s, 9H); 4.09 (m,

1H); 4.86 (m, 1H); 7.35 (d, 2H, J ) 5.7 Hz); 8.21 (s, 1H); 8.47 (d,

2H, J ) 5.7 Hz).

(()-N-[(tert-Butoxy)carbonylamino][7-chloro-4-oxo-2-(pyrro-

lidinylcarbonyl)(3-hydroquinolyl]-N-(4-pyridylethyl)carboxam-

ide. The title compound was prepared from 7-chloro-4-oxo-2-

(pyrrolidinylcarbonyl)hydroquinoline-3-carboxylic acid (7) (1.66 g,

5.17 mmol) and (()-(tert-butoxy)-N-[(4-pyridylethyl)amino]car-

boxamide (1.3 g, 5.69 mmol) according to Method B. After stirring

the reaction mixture at rt for 2 h, an additional portion of CMC

(0.500 g) was added and the mixture was refluxed overnight. The

solution was cooled to 50 °C, another portion of CMC was added

(0.50 g), and the mixture was refluxed for 3 h. The cooled reaction

1

the R,R-dichlorinated material). H NMR (300 MHz, DMSO-d₆):

δ 4.88 (s, 2H), 8.65-8.68 (m, 2H); 8.85 (s, 1H).

AntinociceptiVe NMDA Glycine-Site Antagonists

Journal of Medicinal Chemistry, 2007, Vol. 50, No. 13 3123

(tert-Butoxy)-N-[(pyrazin-2-ylmethyl)amino]carboxamide. The

title compound was prepared from 2-chloromethylpyrazine (1.2 g,

93 mmol) and tert-butyl carbazate (6.3 g, 48 mmol) according to

Method E except that the extraction was carried out with Et₂O (5×)

and the flash chromatography employed a 2-5% gradient of MeOH

in CH₂Cl₂as the eluent to give the title compound as a waxy brown

solid (1.64 g, 79%). ¹H NMR (300 MHz, DMSO-d₆, TFA shake):

δ 1.44 (s, 9H); 4.53 (s, 2H); 8.71-8.78 (m, 2H); 8.81 (s, 1H).

N-[(tert-Butoxy)carbonylamino][7-chloro-4-oxo-2-(pyrrolidi-

nylcarbonyl)(3-hydroquinolyl)]-N-(pyrazin-2-ylmethyl)carboxa-

mide. The title compound was prepared from 7-chloro-4-oxo-2-

(pyrrolidinylcarbonyl)hydroquinoline-3-carboxylic acid (7) (2.3 g,

7.2 mmol) and (tert-butoxy)-N-[(pyrazin-2-ylmethyl)amino]car-

boxamide (1.6 g, 7.1 mmol) according to Method B to afford the

crude product as a brown foam (4.9 g) which was subjected to

flash chromatography (silica gel, 2% MeOH in CH₂Cl₂) to give

the pure compound (3.1 g, 82%).

7-Chloro-4-hydroxy-2-(pyrazin-2-ylmethyl)-1,2,5,10-tetrahy-

dropyridazino[4,5-b]quinoline-1,10-dione Methanesulfonate 9h.

The title compound was prepared from N-[(tert-butoxy)carbony-

lamino][7-chloro-4-oxo-2-(pyrrolidinylcarbonyl)(3-hydroquinolyl)]-

N-(pyrazin-2-ylmethyl)carboxamide (3.1 g, 5.9 mmol) according

to Method D as a white powder (2.0 g, 80%); mp 235-245 °C. ¹H

NMR (300 MHz, DMSO-d₆): δ 2.38 (CH₃SO₃H, s, 3H), 5.27 (s,

2H); 7.44 (dd, 1H, J ) 1.8, 8.7 Hz); 8.04 (d, 1H, J ) 1.8 Hz);

8.14 (d, 1H, J ) 8.7 Hz); 8.58 (dd, 2H, J ) 2.4, 7.5 Hz); 8.63 (s,

1 H). Anal. (C₁₆H₁₀ClN₅O₃‚CH₃SO₃H‚H₂O): C, H, N.

N-[(Benzo[d]furan-2-ylmethyl)amino](tert-butoxy)carboxam-

ide. The title compound was prepared from N-(1-aza-2-benzo[d]-

furan-2-ylvinyl)(tert-butoxy)carboxamide (4.0 g, 15 mmol) as a

1

white solid according to Method K (3.4 g, 85%); H NMR (300

MHz, DMSO-d₆): δ 1.37 (s, 9H); 4.00 (s, 2H); 5.01 (br s, 1H);

6.74 (s, 1H); 7.22 (m, 2H); 7.51 (d, J ) 7.7 Hz, 1H); 7.57 (d, J )

7.0 Hz, 1H); 8.36 (s, 1H).

N-{N-(Benzo[d]furan-2-ylmethyl)[7-chloro-4-oxo-2-(pyrrolidi-

nylcarbonyl)(3-hydroquinolyl)]carbonylamino}(tert-butoxy)car-

boxamide. The title compound was prepared from 7-chloro-4-oxo-

2-(pyrrolidinylcarbonyl)hydroquinoline-3-carboxylic acid 7 (4.1 g,

13 mmol) and N-[(benzo[d]furan-2-ylmethyl)amino](tert-butoxy)-

carboxamide (3.3 g, 13 mmol) as described in Method B. The

desired product was obtained as a pale yellow solid and was used

in the following step without characterization.

7-Chloro-4-hydroxy-2-benzo[d]furan-2-ylmethyl-1,2,5,10-tet-

rahydropyridazino[4,5-b]quinoline-1,10-dione 9j. The title com-

pound was prepared from N-{N-(benzo[d]furan-2-ylmethyl)[7-

chloro-4-oxo-2-(pyrrolidinyl-carbonyl)(3-hydroquinolyl)]-

carbonylamino}(tert-butoxy)carboxamide (6.2 g, 11 mmol) according

1

to Method G as an off-white solid (3.4 g, 78%); H NMR (300

MHz, DMSO-d₆): δ 5.27 (s, 2H); 6.84 (s, 1H); 7.25 (m, 2H); 7.44

(dd, J ) 2.0, 8.9 Hz, 1H); 7.53 (d, J ) 8.1 Hz, 1H); 7.59 (d, J )

7.7 Hz, 1H); 8.04 (d, J ) 1.6 Hz, 1H); 8.15 (d, J ) 8.8 Hz, 1H);

11.96 (br s, 1H); 12.74 (br s, 1H). Anal. (C₂₀H₁₂N₃O₄Cl-0.1H₂O-

0.3CH₃SO₃H): C, H, N.

Compound 9k. (()-7-Chloro-4-hydroxy-2-(1-(benzo[b]furan-

2-yl)ethyl)-1,2,5,10-tetrahydropyridazino[4,5-b]quinoline-1,10-

dione. N′-(1-Benzofuran-2-yl-ethylidene)-hydrazinecarboxylic

Acid tert-Butyl Ester. The title compound was prepared from

benzofuran-2-yl methyl ketone (5.0 g, 31 mmol) as a white solid

according to Method I (8.2 g, 30 mmol, 96%); ¹H NMR (300 MHz,

DMSO-d₆): δ 1.50 (s, 9H); 2.17 (s, 3H); 7.26 (m, 1H); 7.26 (s,

1H); 7.35 (dd, J ) 7.2, 7.2 Hz, 1H); 7.60 (d, J ) 8.1 Hz, 1H);

7.65 (d, J ) 7.8 Hz, 1H); 10.03 (s, 1H).

Compound 9i. 7-Chloro-4-hydroxy-2-(furan-3-ylmethyl)-

1,2,5,10-tetrahydropyridazino[4,5-b]quinoline-1,10-dione. N-1-

Aza-2-(3-furyl)vinyl)(tert-butoxy)carboxamide. The title com-

pound was prepared as a peach-colored solid from furan-3-

carboxaldehyde (2.0 g, 21 mmol) as described in Method I (4.2 g,

1

97%); H NMR (300 MHz, DMSO-d₆): δ 10.77 (br s, 1H); 8.02

(s, 1H); 7.94 (s, 1H); 7.71 (dd, J ) 1.5, 1.5 Hz, 1H); 6.77 (d, J )

1.5 Hz, 1H); 1.45 (s, 9H).

(tert-Butoxy)-N-[(3-furylmethyl)amino]carboxamide. The title

compound was prepared from N-1-aza-2-(3-furyl)vinyl)(tert-bu-

toxy)carboxamide (2.0 g, 9.5 mmol) as a clear oil according to

N′-(1-Benzofuran-2-yl-ethyl)-hydrazinecarboxylic Acid tert-

Butyl Ester. The title compound was prepared from N′-(1-

benzofuran-2-yl-ethylidene)-hydrazinecarboxylic acid tert-butyl

ester (3.0 g, 11 mmol) as a white solid according to Method K

(3.1 g, 100%). This material was used without further purification.

N′-(1-Benzofuran-3-yl-ethyl)-N′-[7-chloro-4-oxo-2-(pyrrolidine-

1-carbonyl)-1,4-dihydroquinoline-3-carbonyl]-hydrazinecarbox-

ylic Acid tert-Butyl Ester. The title compound was prepared from

7-chloro-4-oxo-2-(pyrrolidinylcarbonyl)hydroquinoline-3-carboxy-

lic acid 7 (1.77 g, 5.51 mmol) and N′-(1-benzofuran-2-yl-ethyl)-

hydrazinecarboxylic acid tert-butyl ester (1.5 g, 5.51 mmol)

according to Method B as a pale yellow solid. The material was

used in the following reaction without further purification.

7-Chloro-4-hydroxy-2-(1-(benzo[b]furan-2-yl)ethyl)-1,2,5,10-

tetrahydropyridazino[4,5-b]quinoline-1,10-dione 9k. To a 0 °C

solution of N′-(1-benzofuran-3-yl-ethyl)-N′-[7-chloro-4-oxo-2-(pyr-

rolidine-1-carbonyl)-1,4-dihydroquinoline-3-carbonyl]-hydrazinecar-

boxylic acid tert-butyl ester (1.0 g, 1.74 mmol) in MeOH (20 mL)

was added dropwise a rt solution of methanesulfonic acid (3.4 mL,

52.3 mmol) in MeOH (10 mL). This mixture was allowed to warm

to rt and stirred for 24 h, at which time H₂O (ca. 100 mL) was

added and the precipitate collected. This solid was sonicated (50

mL of 10% MeOH/Et₂O) for 20 min and the solid collected. This

sonication step was repeated, and ultimately a tan solid was

collected. This material was dried at 30 °C at 500 mTorr for 1.5 h

to afford the title compound (260 mg, 36%). ¹H NMR (300 MHz,

DMSO-d₆): δ 1.71 (d, J ) 6.9 Hz, 3H).; 6.41 (q, J ) 7.2 Hz, 1H);

6.88 (s, 1H); 7.25 (m, 2H); 7.44 (d, J ) 7.2 Hz, 1H); 7.50 (d, J )

7.5 Hz, 1H); 7.60 (dd, J ) 1.5, 5.7 Hz, 1H); 8.02 (d, J ) 1.8 Hz,

1H); 8.16 (d, J ) 8.7 Hz, 1H); 11.93 (s, 1H); 12.56 (s, 1H). Anal.

(C₂₁H₁₄ClN₃O₄‚0.2 H₂O): C, H, N.

1

Method K (930 mg, 46%). H NMR (300 MHz, DMSO-d₆): δ

1.39 (s, 9H); 3.69 (s, 2H); 4.64 (br s, 1H); 6.42 (d, J ) 1.2 Hz,

1H); 7.53 (s, 1H); 7.58 (dd, J ) 1.5, 1.5 Hz, 1H); 8.26 (br s, 1H).

(tert-Butoxy)-N-{[7-chloro-4-oxo-2-(pyrrolidinylcarbonyl)(3-

hydroquinolyl)]-N-3-(furylmethyl)carbonylamino}-

carboxamide. The title compound was prepared from 7-chloro-4-

oxo-2-(pyrrolidinylcarbonyl)hydroquinoline-3-carboxylic acid 7 (1.4

g, 4.4 mmol) and (tert-butoxy)-N-[(3-furylmethyl)amino]carboxa-

mide (930 mg, 4.4 mmol) as described in Method B as a pale yellow

solid (2.1 g, 4.1 mmol, 93%). This material was used in the

subsequent reaction without further characterization.

7-Chloro-4-hydroxy-2-(furan-3-ylmethyl)-1,2,5,10-tetrahydro-

pyridazino[4,5-b]quinoline-1,10-dione 9i. The title compound was

prepared from (tert-butoxy)-N-{[7-chloro-4-oxo-2-(pyrrolidinyl-

carbonyl)(3-hydroquinolyl)]-N-3-(furylmethyl)carbonylamino}-

carboxamide (1.4 g, 2.8 mmol) according to Method G except that

the collected solid was sonicated for 15 min in 50 mL of a 10%

MeOH in Et₂O solution. The resultant yellow solid was collected,

rinsed with Et₂O, and dried at 30 °C and 50 mTorr for 3 h to afford

the title compound as a pale yellow solid (750 mg, 75%); ¹H NMR

(300 MHz, DMSO-d₆): δ 4.92 (s, 2H); 6.46 (s, 1H); 7.43 (dd, J )

1.8, 8.7 Hz, 1H); 7.61 (d, J ) 1.5 Hz, 1H); 7.65 (s, 1H); 8.02 (d,

J ) 1.5 Hz, 1H); 8.13 (d, J ) 8.7 Hz, 1H); 11.91 (s, 1H); 12.63

(br s, 1H). Anal. (C₁₆H₁₀N₃O₄Cl·0.1H₂O): C, H, N.

Compound 9j. 7-Chloro-4-hydroxy-2-benzo[d]furan-2-ylm-

ethyl-1,2,5,10-tetrahydropyridazino[4, 5-b]quinoline-1,10-dione.

N-(1-aza-2-benzo[d]furan-2-ylvinyl)(tert-butoxy)carboxamide. The

title compound was prepared as a white solid from benzofuran-2-

carboxaldehyde (5.0 g, 34 mmol) according to Method I (9 g,

Compound 9l. 7-Chloro-2-(4,5-dimethyl-furan-2-ylmethyl)-

2,3-dihydro-5H-pyridazino[4,5-b]quinoline-1,4,10-trione. The title

compound was prepared as a yellow solid using 4,5-dimethyl-2-

furaldehyde as the starting material and methods I, K, A, and D,

1

100%); H NMR (300 MHz, DMSO-d₆): δ 1.48 (s, 9H); 7.21 (s,

1H); 7.27 (dd, J ) 7.6, 7.6 Hz, 1H); 7.37 (dd, J ) 7.6, 7.6 Hz,

1H); 7.62 (d, J ) 8.5 Hz, 1H); 7.67 (d, J ) 7.6 Hz, 1H); 8.02 (s,

1H); 11.12 (br s, 1H).

1

except that the cyclization was performed at 0 °C. H NMR (300

3124 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 13

Bare et al.

MHz, DMSO-d₆): δ 1.85 (s, 3H); 2.12 (s, 3H); 4.97 (s, 2H); 6.12

(s, 1H); 7.42 (dd, J ) 8.4, 1.5 Hz, 1H); 8.02 (d, J ) 1.8 Hz, 1H);

8.14 (d, J ) 8.7 Hz, 1H); 11.87 (s, 1H); 12.60 (s, 1H). Anal.

(C₁₈H₁₄ClN₃O₄‚1.5 H₂O): C, H, N.

Compound 9m. 7-Chloro-4-hydroxy-2-[(5-methyl(furan-2-

yl))methyl]-1,2,5,10-tetrahydropyridazin o[4,5-b]quinoline-1,10-

dione. The title compound was prepared as an off-white solid via

Methods I, K, B, and G using 5-methylfurfural as the starting

material. ¹H NMR (300 MHz, DMSO-d₆): δ 2.21 (s, 3H); 5.02 (s,

2H); 6.01 (d, J ) 2.1 Hz, 1H); 6.22 (d, J ) 3.0 Hz, 1H); 7.43 (d,

J ) 8.7 Hz, 1H); 8.02 (d, J ) 1.5 Hz, 1H); 8.43 (d, J ) 8.7 Hz,

1H); 11.92 (s, 1H); 12.69 (br s, 1H). Anal. (C₁₇H₁₂O₄N₃Cl‚1.1

H₂O): C, H, N.

Compound 9n. 7-Chloro-4-hydroxy-2-(thien-2-ylmethyl)-

1,2,5,10-tetrahydropyridazino[4,5-b]quinoline-1,10-dione. The

title compound was prepared as a pale yellow solid via Methods I,

K, B. and G using thiophene-2-carboxaldehyde as the starting

material; this afforded 1.1 g (93%) of a solid starting from 1.0 g of

7. ¹H NMR (300 MHz, DMSO-d₆): δ 5.23 (s, 2H); 6.98 (dd, J )

3.6, 5.1 Hz, 1 H); 7.10 (d, J ) 3.0 Hz, 1 H); 7.42-7.45 (m, 2H);

8.02 (s, 1H); 8.14 (d, J ) 8.7 Hz, 1H); 11.91 (s, 1H); 12.71 (br s,

1H).

Compound 9o. 7-Chloro-4-hydroxy-2-(benzo[b]thien-2-ylm-

ethyl)-1,2,5,10-tetrahydropyridazino[4,5-b]quinoline-1,10-di-

one. Benzo[b]thiophene-2-carbaldehyde. To a solution of benzo-

[b]thiophene (10 g, 74.5 mmol) in dry THF (12 mL) at -78 °C

was added 65 mL of 1.6 M nBuLi in hexanes. Ten minutes later

DMF (23 mL, 298 mmol) was added. The reaction was warmed to

rt and then refluxed for 3 h. The THF was evaporated, and the

residue was poured into 1 N HCl and ice. The acidic solution was

extracted with Et₂O (2×). The combined Et₂O extract was washed

with 1 N HCl (3x), saturated NaHCO₃(1×), brine (1×), and then

dried over MgSO₄. The MgSO₄was filtered off and the filtrate

concentrated to an oil which was treated with NaHSO₃. The solid

that formed was collected, treated with aqueous NaHCO₃, and then

extracted with CH₂Cl₂. The CH₂Cl₂solution was dried over MgSO₄

and evaporated to give the title compound as a yellow oil (3.2 g,

26%); ¹H NMR (300 MHz, CDCl₃): δ 7.44 (dd, 1H, J ) 6.9, 7.2

Hz); 7.51 (dd, 1H, J ) 6.9, 8.1 Hz); 7.91 (d, 1H, J ) 8.1 Hz); 7.95

(d, 1H, J ) 7.8 Hz); 8.04 (s, 1H); 10.12 (s, 1H).

7.82 (d, 1H, 7.2 Hz); 8.06 (s, 1H); 8.15 (d, 1H, J ) 8.7 Hz). Anal.

(C₂₀H₁₂ClN₃O₃S): C, H, N.

Compound 9p. 7-Chloro-4-hydroxy-2-(thien-3-ylmethyl)-

1,2,5,10-tetrahydropyridazino[4,5-b]quinoline-1,10-dione. The

title compound was prepared as a pale yellow solid via Methods I,

K, B, and G using thiophene-3-carboxaldehyde as the starting

material (870 mg, 81%). ¹H NMR (300 MHz, DMSO-d₆): δ 5.08

(s, 2 H); 7.08 (d, J ) 4.5 Hz, 1 H); 7.37 (s, 1 H); 7.43 (dd, J )

1.2, 8.7, 1 H); 7.48-7.54 (m, 1 H); 8.02 (d, J ) 1.5 Hz, 1 H); 8.14

(d, J ) 8.7, 1 H); 11.92 (br s, 1 H); 12.64 (br s, 1 H).

Compound 9q. 7-Chloro-4-hydroxy-2-(1-(thien-3-yl)ethyl)-

1,2,5,10-tetrahydropyridazino[4,5-b]quinoline-1,10-dione. The

title compound was prepared as a pale yellow solid via Methods I,

K, B, and G using 2-acetylthiophene as the starting material (224

mg, 65%). ¹H NMR (300 MHz, DMSO-d₆): δ 1.65 (s, 3 H); 6.26

(q, J ) 6.9 Hz, 1 H); 7.02 (d, J ) 5.1 Hz, 1 H); 7.34 (s, 1H); 7.44

(d, J ) 8.7 Hz, 1 H); 7.46-7.49 (m, 1 H); 8.02 (d, J ) 1.2 Hz, 1

H); 8.15 (d, J ) 8.7 Hz, 1 H); 11.90 (br s, 1 H); 12.25 (br s, 1H).

Compound 9r. 7-Chloro-4-hydroxy-2-[2-(3-methyl)thienyl-

methyl]-1,2,5,10-tetrahydropyridazino[4,5-b]quinoline-1,10-di-

one. (tert-Butoxy)-N-[1-aza-2-(3-methyl(2-thienyl)vinyl]carbox-

amide. The title compound was prepared starting with 3-methyl-

thiophene-2-carboxaldehyde (5.03 g, 39.86 mmol) as starting

material via Method I. This afforded the desired compound as an

off-white powder (6.92 g, 80%); ¹H NMR (300 MHz, DMSO-d₆):

δ 1.45 (s, 9H); 2.24 (s, 3H); 6.91 (d, 1H, J ) 5.1 Hz); 7.46 (d, 1H,

J ) 5.1 Hz); 8.25 (s, 1H); 10.70 (s, 1H).

(tert-Butoxy)-N-{[(3-methyl(2-thienyl))methyl]amino}-

carboxamide. The title compound was prepared from (tert-butoxy)-

N-[1-aza-2-(3-methyl(2-thienyl)vinyl]carboxamide (2.60 g, 10.82

mmol) via Method K with the exception that p-toluenesulfonic acid

(1.5 equiv) was used in place of acetic acid with THF as the solvent.

After purification by flash chromatography on silica gel eluting

with 3:1 hexane:EtOAc, the desired compound was obtained as a

1

colorless oil (2.44 g, 92%); H NMR (300 MHz, DMSO-d₆): δ

1.39 (s, 9H); 2.14 (s, 3H); 3.95 (d, 2H, J ) 4.5 Hz); 4.69 (d, 1H,

J ) 3.9 Hz); 6.82 (d, 1H, J ) 5.1 Hz); 7.29 (d, 1H, J ) 5.1 Hz);

8.26 (s, 1H).

(tert-Butoxy)-N-{[7-chloro-4-hydroxy-2-(pyrrolidinylcarbonyl)-

(3-quinolyl)]-N-[(3-methyl(2-thienyl))methyl]carbonylamino}-

carboxamide. The title compound was prepared from 7-chloro-4-

oxo-2-(pyrrolidinylcarbonyl)hydroquinoline-3-carboxylic acid 7

(3.56 g, 11.10 mmol) and (tert-butoxy)-N-{[(3-methyl(2-thienyl))-

methyl]amino}carboxamide (2.44 g, 10.07 mmol) according to

Method A except that the reaction was refluxed overnight and THF

was used for the washings during filtration, and no aqueous workup

was performed. The resultant yellow solid (6.72 g) was purified

by flash chromatography on silica gel eluting with 95:5 CH₂Cl₂:

MeOH to give the desired compound as a yellow powder (3.22 g,

59%).

7-Chloro-10-hydroxy-2-[(3-methyl(2-thienyl))methyl]-2,3-di-

hydropyridazino[4,5-b]quinoline-1,4-dione 9r. The title com-

pound was prepared from (tert-butoxy)-N-{[7-chloro-4-hydroxy-

2-(pyrrolidinylcarbonyl)(3-quinolyl)]-N-[(3-methyl(2-

thienyl))methyl]carbonylamino}carboxamide (3.68 g, 6.77 mmol)

according to Method E except that the collected solids were

successively washed with water (30 mL), MeOH (20 mL), and Et₂O

(150 mL) and then dried at 50 °C in Vacuo to give the desired

compound as an off-white powder (1.98 g, 78%); mp >250 °C;

¹H NMR (300 MHz, DMSO-d₆): δ 2.32 (s, 3H), 5.17 (s, 2H); 6.84

(d, 1H, J ) 5.1 Hz); 7.32 (d, 1H, J ) 5.1 Hz); 7.43 (d, 1H, J ) 8.7

Hz); 8.02 (s, 1H); 8.14 (d, 1H, J ) 8.7 Hz); 11.92 (br s, 1H); 12.62

(br s, 1H). Anal. (C₁₇H₁₂ClN₃O₃S‚0.05 CH₃SO₃H‚0.05 H₂O): H,

N; C: calcd 54.62; found, 53.96.

(tert-Butoxy)-N-(1-aza-2-benzo[b]thien-2-ylvinyl)carboxam-

ide. The title compound was prepared from benzo[b]thiophene-2-

carbaldehyde (3.2 g, 19.7 mmol) according to Method I (3.8 g,

1

70%); H NMR (300 MHz, CDCl₃): δ 1.54 (s, 9H); 7.30-7.36

(m, 2H); 7.40 (s, 1H); 7.71-7.74 (m, 1H); 7.78-7.81 (m, 1H);

7.89 (s, 1H); 8.31 (br s,1H).

(tert-Butoxy)-N-[(benzo[b]thien-2-ylmethyl)amino]carboxam-

ide. The title compound was prepared from (tert-butoxy)-N-(1-aza-

2-benzo[b]thien-2-ylvinyl)carboxamide (1.8 g, 6.5 mmol) using

Method K with the exception that p-toluene sulfonic acid (1.5 equiv)

was used in place of acetic acid with THF as the solvent. This

afforded the title compound as a white solid (1.7 g, 76%); ¹H NMR

(300 MHz, CDCl₃): δ 1.44 (s, 9H); 4.68 (s, 2H); 7.36-7.45 (m,

2H); 7.45 (s, 1H); 7.78-7.86 (m, 2H).

N′-Benzo[b]thien-2-ylmethyl-N′-[7-chloro-4-oxo-2-(pyrrolidine-

1-carbonyl)-1,4-dihydroquinoline-3-carbonyl]hydrazinecarboxy-

lic Acid tert-Butyl Ester. The title compound was prepared from

7-chloro-4-oxo-2-(pyrrolidinylcarbonyl)hydroquinoline-3-carboxy-

lic acid 7 (1.59 g, 5.0 mmol) and (tert-butoxy)-N-[(benzo[b]thien-

2-ylmethyl)amino]carboxamide (1.37 g, 5.0 mmol) as a yellow solid

according to Method B (771 mg, 24% yield).

7-Chloro-4-hydroxy-2-(benzo[b]thien-2-ylmethyl)-1,2,5,10-tet-

rahydropyridazino[4,5-b]quinoline-1,10-dione 9o. The title com-

pound was prepared from N′-benzo[b]thien-2-ylmethyl-N′-[7-chloro-

4-oxo-2-(pyrrolidine-1-carbonyl)-1,4-dihydroquinoline-3-

carbonyl]hydrazinecarboxylic acid tert-butyl ester (760 mg, 1.3

mmol) according to Method E except that the resulting precipitate

was sonicated in MeOH and dried in Vacuo to give the desired

Compound 9s. 7-Chloro-4-hydroxy-2-(5-isoxazolino)methyl-

1,2,5,10-tetrahydropyridazino[4,5-b]quinoline-1,10-dione. N′-

Isoxazol-5-ylmethyl-hydrazinecarboxylic Acid tert-Butyl Ester.

The title compound was prepared from 5-bromomethyl-isoxazole

(1.62 g, 10 mmol) according to Method H except that Na₂CO₃was

used as the base, and the residual DMF and excess tert-butyl

carbazate were removed by vacuum distillation (50 mTorr, 80 °C).

1

product as an off-white solid (470 mg, 88%); mp >300 °C; H

NMR (300 MHz, DMSO-d₆): δ 5.38 (s, 2H); 7.30-7.38 (m, 2H,);

7.40 (s, 1H); 7.44 (d, 1H, J ) 8.7 Hz); 7.90 (d, 1H, J ) 7.2 Hz);

AntinociceptiVe NMDA Glycine-Site Antagonists

Journal of Medicinal Chemistry, 2007, Vol. 50, No. 13 3125

Silica gel chromatography (hexanes:EtOAc, 1:1 as eluent) afforded

the desired compound as a white solid (1.01 g, 49%); H NMR

(300 MHz, DMSO-d₆): δ 1.38 (s, 9H); 4.01 (s, 2H); 5.13 (bs, 1H);

6.38 (s, 1H); 8.38 (s, 1H); 8.48 (s, 1H).

N′-[7-Chloro-4-hydroxy-2-(pyrrolidine-1-carbonyl)-quinoline-

3-carboxyl]-N′-is oxazol-5-ylmethyl-hydrazinecarboxylic Acid

tert-Butyl Ester. The title compound was prepared from 7-chloro-

4-oxo-2-(pyrrolidinylcarbonyl)hydroquinoline-3-carboxylic acid 7

(1.51 g, 4.7 mmol) and N′-isoxazol-5-ylmethyl-hydrazinecarboxylic

acid tert-butyl ester (1.0 g, 4.7 mmol) according to Method B except

that the reaction mixture was heated to reflux for 1.5 h then stirred

at rt for 16 h. The desired product was obtained as an off-white

foam (2.09 g, 86%).

(300 MHz, DMSO-d₆): δ 1.38 (s, 9H); 3, 84 (s, 3H,); 3.92 (d, 2H,

J ) 4.2 Hz); 4.95 (d, 1H, J ) 4.2 Hz); 7.47(d, 2H, J ) 8.4 Hz);

7.90 (d, 2H, J ) 8.1 Hz); 8.29 (s, 1H).

1

N-[(tert-Butoxy)carbonylamino][7-chloro-4-oxo-2-(pyrrolidi-

nylcarbonyl)(3-hydroquinolyl)]-N-(4-carbomethoxybenzyl)car-

boxamide. The title compound was prepared from 7-chloro-4-oxo-

2-(pyrrolidinylcarbonyl)hydroquinoline-3-carboxylic acid (7) (18.38

g, 57 mmol) and methyl 4-({[(tert-butoxy)carbonylamino]amino}-

methyl)benzoate (24.1 g, 86 mmol) according to Method A except

that the crude material was preabsorbed onto silica gel using MeOH

and was eluted using 5:95 MeOH:CHCl₃as eluent to provide the

title compound as a tan solid (33.43 g, 100%) contaminated with

dicyclohexylurea. This material was used directly in the subsequent

reaction.

Methyl 4-[(7-Chloro-4-hydroxy-1,10-dioxo-2,5-dihydropy-

ridazino[4,5-b]quinolin-2-yl)methyl]benzoate 9u. The title com-

pound was prepared from N-[(tert-butoxy)carbonylamino][7-chloro-

4-oxo-2-(pyrrolidinylcarbonyl)(3-hydroquinolyl)]-N-(4-

carbomethoxybenzyl)carboxamide (33.6 g, 57.3 mmol) according

to Method G as a white solid (13.38 g, 40% yield); mp >290 °C;

¹H NMR (300 MHz, DMSO-d₆): δ 3.83 (s, 3H), 5.18 (s, 2H); 7.43

(m, 3H,); 7.92 (d, 2H, J ) 8.1 Hz); 8.02 (S, 1H); 8.14 (d, 1H, J )

8.4 Hz). Anal. (C₂₀H₁₄ClN₃O₅): C, H, N.

Compound 9v. 7-Chloro-4-hydroxy-2-[4-(carbomethoxy)phe-

nyl-2-ethyl)-1,2,5,10-tetrahydropyridazino[4,5-b]quinoline-1,10-

dione. 4-[1-(tert-Butoxycarbonyl-hydrazino)-ethyl]-benzoic Acid

Methyl Ester. The title compound was prepared from methyl

4-acetylbenzoate (5.20 g, 29.2 mmol) and tert-butyl carbazate (3.85

g, 29.2 mmol) according to Method I. After drying in Vacuo (500

mTorr, 30 °C) for 30 min, the title compound was obtained as an

off-white solid (8.36 g, 98%). ¹H NMR (300 MHz, DMSO-d₆): δ

1.49 (s, 9H); 2.22 (s, 3H); 3.34(s, 1H); 3.86 (s, 3H); 7.87 (d, 2H,

J_o)8.4 Hz); 7.97 (d, 2H, J_o)8.4 Hz); 9.97 (s, 1H).

4-[1-(tert-Butoxycarbonyl-hydrazino)-ethyl]-benzoic Acid Meth-

yl Ester. The title compound was prepared from 4-[1-(tert-

butoxycarbonyl-hydrazino)-ethyl]benzoic acid methyl ester (8.35

g, 28.6 mmol) according to Method J except that the crude material

was purified by flash chromatography on silica gel using a gradient

of 10:90 to 20:80 EtOAc:CH₂Cl₂. The desired compound was

obtained as a white solid (6.41 g, 76%). ¹H NMR (300 MHz,

DMSO-d₆): δ 1.18 (d, 3H, J ) 6.6 Hz); 1.35 (s, 9H); 3.84 (s, 3H);

4.16 (m, 1H); 4.71 (m, 1H); 7.48 (d, 2H, J_o) 8.3 Hz); 7.89 (d,

2H, J_o) 8.3 Hz); 8.15 (s, 1H).

7-Chloro-4-hydroxy-2-(5-isoxazolino)methyl-1,2,5,10-tetrahy-

dropyridazino[4,5-b]quinoline-1,10-dione 9s. The title compound

was prepared from N′-[7-chloro-4-hydroxy-2-(pyrrolidine-1-carbo-

nyl)-quinoline-3-carboxyl]-N′-isoxazol-5-ylmethyl-hydrazinecar-

boxylic acid tert-butyl ester (1.0 g, 1.94 mmol) according to Method

E except that 9:1 Et₂O: MeOH was used for the sonication followed

by filtration and washing of the solids with Et₂O. After drying in

Vacuo (500 mTorr, 30 °C) for 18 h, the desired compound was

1

obtained as a yellow solid (0.54 g, 81%); H NMR (300 MHz,

DMSO-d₆): δ 5.27 (s, 2H); 6.44 (s, 1H); 7.45 (dd, 1H, J_o) 8.7

Hz, J_m) 1.8 Hz); 8.03 (d, 1H, J_m) 1.8 Hz); 8.15 (d, 1H, J_o) 8.7

Hz); 8.53 (s, 1H, J_m) 1.8 Hz); 11.99 (s, 1H); 12.82 (s, 1H); Anal.

(C₁₅H₉ClN₄O₄‚0.4 H₂O): C, H, N.

Compound 9t. 7-Chloro-4-hydroxy-2-(1,3-thiazo-2-ylmethyl)-

1,2,5,10-tetrahydropyridazino[4,5-b]quinoline-1,10-dione Meth-

anesulfonate. (tert-Butoxy)-N-[(1,3-thiazol-2-ylmethyl)amino]-

carboxamide. To a stirred solution of thiazole-2-carbaldehyde (0.95

g, 8.42 mmol) and tert-butyl carbazate (1.17 g, 8.87 mmol) in EtOH

(15 mL) was added 1.10 mL of glacial AcOH, followed by

NaCNBH₃(2.18 g, 34.7 mmol). The reaction mixture was heated

at 50 °C and stirred for 72 h. The reaction was quenched with 2 N

NaOH (30 mL), and the resulting solution was extracted with EtOAc

(3 × 30 mL). The combined organic layers were washed with brine

(40 mL) and then dried over Na₂SO₄. The Na₂SO₄was filtered

off, and the filtrate was purified bychromatography on silica gel

using 1:3 EtOAc:CH₂Cl₂as eluent to give the title compound as

an off-white solid (0.62 g, 32%); ¹H NMR (300 MHz, DMSO-d₆):

δ 1.38 (s, 9H); 4.15 (d, 2H, J ) 3.9 Hz); 5.34 (d, 1H, J ) 3.9 Hz);

7.63 (d, 1H, J ) 3.3 Hz); 7.70 (d, 1H, J ) 3.3 Hz); 8.42 (br s,

1H).

N-[(tert-Butoxy)carbonylamino][7-chloro-4-oxo-2-(pyrrolidi-

nylcarbonyl)(3-hydroquinolyl)]-N-(1,3-thiazol-2-ylmethyl)car-

boxamide. The title compound was prepared from 7-chloro-4-oxo-

2-(pyrrolidinylcarbonyl)hydroquinoline-3-carboxylic acid 7 (0.90

g, 2.80 mmol) and (tert-butoxy)-N-[(1,3-thiazol-2-ylmethyl)amino]-

carboxamide (0.5 g, 2.20 mmol) according to Method B. The

desired product was obtained as a yellow solid (0.97 g, 83%).

7-Chloro-4-hydroxy-2-(1,3-thiazo-2-ylmethyl)-1,2,5,10-tet-

rahydropyridazino[4, 5-b]quinoline-1,10-dione 9t. The title com-

pound was prepared from N-[(tert-butoxy)carbonylamino][7-chloro-

4-oxo-2-(pyrrolidinylcarbonyl)(3-hydroquinolyl)]-N-(1,3-thiazol-2-

ylmethyl)carboxamide (760 mg, 1.3 mmol) according to Method

E except that the solids were sonicated in MeOH. The desired

product was obtained as an off-white solid (648 mg, 78%); mp

>300 °C; ¹H NMR (300 MHz, DMSO-d₆): δ 2.38 (CH₃SO₃H, s,

3H), 5.38 (s, 2H); 7.45 (d, 1H, J ) 8.7 Hz); 7.70 (d, 1H, J ) 3.3);

7.76 (d, 1H, J ) 3.3 Hz); 8.04 (s, 1H); 8.15 (d, 1H, 8.7 Hz). Anal.

(C₁₅H₁₀ClN₄O₃S‚H₂O‚H₃CSO₃H): C, H; N: calcd 11.77; found,

11.39.

4-(1-{N′-tert-Butoxycarbonyl-N-[7-chloro-4-hydroxy-2-(pyr-

rolidine-1-carbonyl)-quinoline-3-carboxyl]-hydrazino}-ethyl)-

benzoic Acid Methyl Ester. The title compound was prepared from

7-chloro-4-oxo-2-(pyrrolidinylcarbonyl)hydroquinoline-3-carboxy-

lic acid (4) (2.15 g, 6.7 mmol) and 4-[1-(tert-butoxycarbonyl-

hydrazino)-ethyl]-benzoic acid methyl ester (1.97 g, 6.7 mmol)

according to Method B as an off-white solid (3.53 g, 71%).

7-Chloro-4-hydroxy-2-[4-(carbomethoxy)phenyl-2-ethyl)-1,2,5,-

10-tetrahydropyridazino[4,5-b]quinoline-1,10-dione 9v. The title

compound was prepared from 4-(1-{N′-tert-butoxycarbonyl-N-[7-

chloro-4-hydroxy-2-(pyrrolidine-1-carbonyl)-quinoline-3-carboxyl]-

hydrazino}-ethyl)-benzoic acid methyl ester (3.45 g, 5.78 mmol)

in THF (50 mL) according to Method E. After drying in Vacuo

(500 mTorr, 30 °C) for 18 h, the resulting yellow solid (2.05 g,

83%) was found to be of insufficient purity by ¹H NMR. A portion

of this material (1.73 g) was suspended in CH₃CN (10 mL) and

H₂O (10 mL) to which was added 20% choline hydroxide in water

dropwise until all the solids dissolved, then purified by preparative

HPLC (41.4 mm × 25 cm C-18 Dynamax 60A column using a

gradient 10-35% of CH₃CN in H₂O with 0.1% TFA over 50 min

with a flow rate of 20 mL/min, monitoring 210 nM). Product was

precipitated from the fractions containing title material by addition

of 6M HCl to pH 3. The solid was collected by vacuum filtration,

washed with water (2 × 50 mL) then Et₂O (2 × 50 mL), and dried

in Vacuo (500 mTorr, 30 °C) for 18 h to give the title compound

Compound 9u. Methyl 4-[(7-chloro-4-hydroxy-1,10-dioxo-2,5-

dihydropyridazino[4,5-b]quinolin-2-yl)methyl]benzoate. Methyl

4-({[(tert-Butoxy)carbonylamino]amino}methyl)benzoate. The

title compound was prepared from methyl 4-bromomethylbenzoate

(25.0 g, 0.11 mol) and tert-butyl carbazate (68.65 g, 0.52 mol)

according to Method H except that the extraction was carried out

with CH₂Cl₂(4 × 350 mL), and the combined organic layers were

dried over MgSO₄. The usual purification afforded the pure

1

as a yellow solid (1.23 g, 59%). H NMR (300 MHz, DMSO-d₆):

δ 1.69 (d, 3H, J ) 6.9 Hz); 3.84 (s, 3H); 6.26 (q, 1H, J ) 7.2 Hz);

7.38-7.50 (m, 3H,); 7.92 (d, 2H, J_o) 8.4 Hz); 8.03 (d, 1H, J_m)

1

compound as a clear colorless oil (26.50 g, 87% yield). H NMR

3126 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 13

Bare et al.

1.8 Hz); 8.15 (d, 1H, J_o) 8.7 Hz); 11.94 (s, 1H); 12.57 (s, 1H).

Anal. (C₂₁H₁₆ClN₃O₅‚0.2 H₂O): C, H, N.

The organic phase was dried over MgSO₄, filtered, and reduced

by rotary evaporation to an oily brown solid. The residual DMF

and tert-butyl carbazate were removed by Kugelrohr distillation at

90 °C and 50 mTorr. The residual brown solid was purified by

chromatography on silica gel eluting with 10% EtOAc in CH₂Cl₂

to give the title compound as a yellow solid (15 g, 79%).

(tert-Butoxy)-N-{[7-chloro-4-oxo-2-(pyrrolidinylcarbonyl)(3-

hydroquinolyl)][(4-nitrophenyl)methyl]amino}carboxamide. The

title compound was prepared from 7-chloro-4-oxo-2-(pyrrolidinyl-

carbonyl)hydroquinoline-3-carboxylic acid 7 (12 g, 38 mmol) and

(tert-butoxy)-N-{[(4-nitrophenyl)methyl]amino}carboxamide (10 g,

38 mmol) according to Method B except that a mechanical stirrer

was employed and the mixture was heated for 5 min prior to the

addition of the hydrazine. The desired compound was obtained as

a yellow solid (14.5 g, 68%).

N-{[4-Aminophenyl)methyl][7-chloro-4-oxo-2-(pyrrolinylcar-

bonyl)(3-hydroquinolyl)]amino}(tert-butoxy)carboxamide. The

(tert-butoxy)-N-{[7-chloro-4-oxo-2-(pyrrolidinylcarbonyl)(3-hydro-

quinolyl)][(4-nitrophenyl)methyl]amino}carboxamide (6.9 g, 12

mmol) was dissolved in CH₂Cl₂(1 L). 1,1′-Dioctadecyl-4,4′-

bipyridinium dibromide (500 mg, 600 µmol) was added, followed

by H₂O (10 mL). This mixture was heated to 35 °C under N₂, at

which time a solution of sodium dithionate (25.3 g, 145 mmol)

and K₂CO₃(8.4 g, 60.5 mmol) in H₂O (150 mL) was added. After

4 h, a second batch of sodium dithionate (25.4 g) and K₂CO₃(60.5

g) in H₂O (150 mL) was added. The reaction was stirred an

additional 18 h and then cooled to rt. The organic phase was

separated, the aqueous was extracted with CHCl₃(100 mL), and

the combined organic phases were washed with brine (50 mL), dried

over anhydrous MgSO₄, and concentrated by rotary evaporation.

This material was chromatographed on silica gel with 5% MeOH

in CHCl₃to afford the title compound as a yellow solid (4.5 g,

69%).

(Dimethylamino)-N-[4-({[tert-butoxy)carbonylamino][7-chloro-

4-oxo-2-(pyrrolidinylcarbonyl)(3-hydroquinolyl)]amino}methyl)-

phenyl]carboxamide. The N-{[4-aminophenyl)methyl][7-chloro-

4-oxo-2-(pyrrolinylcarbonyl)(3-hydroquinolyl)]amino}(tert-

butoxy)carboxamide (1.0 g, 1.9 mmol) was dissolved in CH₂Cl₂

(50 mL), and Et₃N (350 µL, 2.5 mmol) was added, followed by

DMAP (10 mg, 100 µmol) and dimethylcarbamoyl chloride (200

µL, 2 mmol). The reaction was stirred for 50 h. Four 0.2 mL

portions of additional dimethylcarbamoyl chloride were added

during this time. The reaction mixture was washed with H₂O and

brine, dried over MgSO₄, and chromatographed on silica gel with

5% MeOH in CH₂Cl₂to afford the title compound as a yellow

solid (690 mg, 61%).

Compound 9w. 4-[(7-Chloro-4-hydroxy-1,10-dioxo-2,5-dihy-

dropyridazino[4,5-b]quinolin-2-yl)methyl]benzoic Acid. To a

stirred suspension of methyl 4-[(7-chloro-4-hydroxy-1,10-dioxo-

2,5-dihydropyridazino[4,5-b]quinolin-2-yl)methyl]benzoate (0.279

g, 0.68 mol) in H₂O (35 mL) was added NaOH (0.08 g, 2.03 mmol).

The mixture was heated to 50 °C for 2 h and acidified to pH ) 1,

and the solid was collected by filtration. The material was dried in

Vacuo to give the title compound as a tan solid (0.133 g, 48%). ¹H

NMR (300 MHz, DMSO-d₆): δ 5.11 (s, 2H); 7.38-7.46 (m, 2H,

J ) 7.8 Hz); 7.90 (d, 2H, J ) 7.8 Hz); 8.03 (s, 1H); 8.15 (d, 2H,

J ) 7.8 Hz. Anal. (C₁₉H₁₂ClN₃O₅‚0.5 H₂O): C, H, N.

Compound 9x. Methyl 3-[(7-Chloro-4-hydroxy-1,10-dioxo-

2,5-dihydropyridazino[4,5-b]quinolin-2-yl)methyl]benzoate. The

title compound was made from methyl 3-bromomethylbenzoate as

described for 9u. After air drying, the title compound was obtained

as a white solid (0.327 g, 100%); ¹H NMR (300 MHz, DMSO-d₆)

δ 3.84 (s, 3H); 5.17 (s, 2H); 7.44 (dd, J ) 2.1, 8.7 Hz, 1H); 7.50

(t, J ) 7.8 Hz, 1H); 7.62 (d, J ) 7.8 Hz, 1H); 7.87 (d, J ) 7.8 Hz,

1H); 7.93 (s, 1H); 8.03 (d, J ) 1.8 Hz, 1H); 8.15 (d, J ) 8.7 Hz,

1H); 12.62 (br s, 1H).

Compound 9y. 3-(7-Chloro-1,4,10-trioxo-3,4,5,10-tetrahydro-

1H-pyridazino[4,5-b]quinolin-2-ylmethyl)-N-methoxy-N-methyl-

benzamide. 4-(tert-Butoxycarbonyl-hydrazonomethyl)-benzoic acid

was prepared from 3-formylbenzoic acid largely according to

Method I. This compound was coupled with N-methoxy-N-

methylamine using EDCI as the coupling reagent. N′-[4-(Methoxy-

methyl-carbamoyl)-benzylidene]-hydrazinecarboxylic acid tert-butyl

ester was hydrogenated according to Method J to afford N′-[3-

(methoxy-methyl-carbamoyl)-benzyl]-hydrazinecarboxylic acid tert-

butyl ester. The coupling of 7-chloro-4-oxo-2-(pyrrolidinylcarbonyl)-

hydroquinoline-3-carboxylic acid (7) and N′-[3-(methoxy-methyl-

carbamoyl)-benzyl]-hydrazinecarboxylic acid tert-butyl ester was

performed largely in accordance to Method B except that CH₂Cl₂

was used as the solvent.

The cyclization to the title compound was performed largely

according to Method F to give the title compound as an off-white

1

powder (0.08 g, 50% yield); H NMR (300 MHz, DMSO-d₆): δ

3.22 (s, 3H); 3.52 (s, 3H); 3.67 (m, 2H); 5.15 (s, 2H); 7.42 (m,

3H); 7.50 (m, 1H); 8.02 (s, 1H); 8.15 (d, 1H, J ) 8.7 Hz); 11.94

(br s); 12.67 (br s, 1H).

Compound 9z. {3-[(7-Chloro-4-hydroxy-1,10-dioxo-(2,5-di-

hydropyridazino[4,5-b]quinolin-2-yl))methyl]phenyl}-N-2-meth-

oxyethyl)carboxamide. This compound was synthesized in an

analogous fashion to 9y to afford, after cyclization, the title

1

compound (0.120 g, 21% yield) as off-white solid. H NMR (300

7-Chloro-4-hydroxy-2-(4-dimethylaminocarboxamide)phe-

nylmethyl-1,2,5,10-tetrahydropyridazino[4,5-b]quinoline-1,10-

dione 9ab. The title compound was prepared from

(dimethylamino)-N-[4-({[tert-butoxy)carbonylamino][7-chloro-4-

oxo-2-(pyrrolidinylcarbonyl)(3-hydroquinolyl)]amino}methyl)phenyl]-

carboxamide (690 mg, 1.13 mmol) according to Method E except

that 1:3 MeOH:Et₂O was used for the sonications. The desired

compound was obtained as a yellow solid (430 mg, 86%); ¹H NMR

(300 MHz, DMSO-d₆): δ 2.90 (s, 6H); 5.02 (s, 2H); 7.17 (d, J )

8.4 Hz, 2H); 7.44-7.37 (m, 3H); 8.02 (s, 1H); 8.15 (d, J ) 8.7

Hz, 1H); 8.27 (s, 1H); 11.91 (s, 1H); 12.61 (s, 1H). Anal. (C₂₁H₁₈-

ClN₅O₄‚0.15 H₂O‚0.15 CH₃SO₃H): C, H, N.

MHz, DMSO-d₆): δ 3.24 (s, 3H); 3.40 (m, 4H); 5.15 (s, 2H); 7.42

(m, 3H); 7.71 (d, 1H, J ) 6.9 Hz); 7.78 (s, 1H); 8.02 (s, 1H); 8.15

(d, 1H, J ) 8.7 Hz); 8.53 (m, 1H, J ) 4.2 Hz); 11.94 (br s); 12.69

(br s, 1H).

Compound 9aa. 7-Chloro-4-hydroxy-2-(4-phenylaminocar-

boxamide)phenylmethyl-1,2,5,10-tetrahydropyridazino[4,5-b]-

quinoline-1,10-dione. The title compound was prepared by the

method described for 9ab (below) from N-{[4-aminophenyl)methyl]-

[7-chloro-4-oxo-2-(pyrrolinylcarbonyl)(3-hydroquinolyl)]amino}-

(tert-butoxy)carboxamide and phenyl isocyanate as a yellow solid

1

(0.55 g, 79% for the final cyclization step). H NMR (300 MHz,

DMSO-d₆): δ 5.04 (s. 2H); 6.95 (t, J ) 7.2 Hz, 1H); 7.20-7.30

(m, 4H); 7.30-7.50 (m, 5H); 8.02 (s, 1H); 8.15 (d, J ) 8.7 Hz,

1H); 8.65 (d, J ) 12.3 Hz, 2H); 11.92 (s,1H); 12.63 (s, 1H). Anal.

(C₂₅H₁₈ClN₅O₄): C, H, N.

Compound 9ab. 7-Chloro-4-hydroxy-2-(4-dimethylaminocar-

boxamide)phenylmethyl-1,2,5,10-tetrahydropyridazino[4,5-b]-

quinoline-1,10-dione·0.15 Methanesulfonate. (tert-Butoxy)-N-

{[(4-nitrophenyl)methyl]amino}carboxamide. To a solution of

4-nitrobenzyl bromide (15 g, 69 mmol) in DMF (100 mL) were

added tert-butyl carbazate (70 g, 529 mmol) and K₂CO₃(10 g, 75

mmol). The mixture was stirred and heated to 90 °C for 2 h under

N₂. At that time, the mixture was cooled, diluted with Et₂O (400

mL), and washed with H₂O (5 × 200 mL) and brine (100 mL).

Compound 9ac. 7-Chloro-4-hydroxy-2-(3-dimethylaminocar-

boxamide)phenylmethyl-1,2,5,10-tetrahydropyridazino[4,5-b]-

quinoline-1,10-dione‚0.35 Methanesulfonate. The title compound

was prepared by the method described for 9ad (below) from N-{-

[3-aminophenyl)methyl][7-chloro-4-oxo-2-(pyrrolinylcarbonyl)(3-

hydroquinolyl)]amino}(tert-butoxy)carboxamide and dimethylcar-

bamoyl chloride to afford 0.41 g (76% for the final cyclization) of

1

the title compound; H NMR (300 MHz, DMSO-d₆): δ 2.89 (s,

6H); 5.05 (s, 2H); 6.87 (d, J ) 7.5 Hz, 1H); 7.17 (t, J ) 7.8 Hz,

1H); 7.30-7.50 (m, 3H); 8.02 (s, 1H); 8.15 (d, J ) 8.7 Hz, 1H);

8.28 (s, 1H); 11.96 (s, 1H); 12.68 (s, 1H). Anal. (C₂₁H₁₈ClN₅O₄‚

0.10 H₂O‚0.35 CH₃SO₃H): C, H, N.

AntinociceptiVe NMDA Glycine-Site Antagonists

Journal of Medicinal Chemistry, 2007, Vol. 50, No. 13 3127

Compound 9ad. 7-Chloro-4-hydroxy-2-(4-(tert-butyl)ami-

nocarboxamide)phenylmethyl-1,2,5,10-tetrahydropyridazino-

[4,5-b]quinoline-1,10-dione. 2. N-[(tert-Butoxy)carbonylamino]-

N-[(3-{[(tert-butyl)amino]carbonylamino}-phenyl)methyl][7-

chloro-4-oxo-2-(pyrrolidinylcarbonyl)(3-hydroquinolyl)]-

carboxamide. To a mixture of N-(N-[(3-aminophenyl)methyl]

[7-chloro-4-oxo-2-(pyrrolidinylcarbonyl)-(3-hydroquinolyl)]carbo-

nylamino)(tert-butoxy)carboxamide (450 mg, 830 µmol) prepared

in an analogous fashion to N-{[4-aminophenyl)methyl][7-chloro-

4-oxo-2-(pyrrolinylcarbonyl)(3-hydroquinolyl)]amino}(tert-butoxy)-

carboxamide, as prepared for 9ab in CH₂Cl₂(10 mL), were added

tert-butyl isocyanate (120 µL, 1.1 mmol) and Et₃N (300 µL, 2.1

mmol). The mixture was stirred for 20 h, at which time additional

tert-butyl isocyanate (100 µL) was added. This solution was then

stirred overnight, and the reaction was diluted with EtOAc, washed

with saturated aqueous NH₄Cl, water, and brine, and then dried

over Na₂SO₄. This material was used in the following step without

purification.

[(tert-Butyl)amino]-N-{3-[(7-chloro-4-hydroxy-1,10-dioxo-

(1,2,5,10-tetrahydropyridazino[4,5-b]quinolin-2-yl))methyl]phe-

nyl)carboxamide 9ad. The title compound was prepared from

N-[(tert-butoxy)carbonylamino]-N-[(3-{[(tert-butyl)amino]carbonyl-

amino}phenyl)methyl][7-chloro-4-oxo-2-(pyrrolidinylcarbonyl)(3-

hydro-quinolyl)]-carboxamide (theoretically 830 µmol) according

to Method G except that the solids were sonicated in 15 mL of a

10% MeOH in Et₂O solution, and the remaining solid was collected

and dried at 30 °C and 50 mTorr for 3 h to afford the desired

compound as a tan solid (230 mg, 490 µmol, 59% for two steps);

¹H NMR (300 MHz, DMSO-d₆): δ 1.26 (s, 9H); 5.04 (s, 2H); 5.91

(s, 1H); 6.81 (d, J ) 7.5 Hz, 1H); 7.15 (dd, J ) 7.8, 7.8 Hz, 1H);

7.22 (s, 1H); 7.30 (d, J ) 8.1 Hz, 1H); 7.44 (d, J ) 8.4 Hz, 1H);

8.03 (s, 1H); 8.14 (d, J ) 8.7 Hz, 1H); 8.24 (s, 1H); 11.94 (br s,

1H); 12.69 (br s, 1H).

Compound 9ae. 7-Chloro-4-hydroxy-2-(3-phenylprop-2-ynyl)-

2,5-dihydropyridazino[4,5-b]quinoline-1,10-dione. tert-Butoxy-

N-[(3-phenylprop-2-ynyl)amino]carboxamide. To a stirred so-

lution of 3-phenylprop-2-yn-1-ol (3.52 g, 26.6 mmol), trifluroacetic

anhydride (5.0 mL, 29.7 mmol), and dry CH₂Cl₂(60 mL) at -75

°C under N₂was added 2,6-lutidine (3.6 mL, 30.9 mmol) in small

portions, maintaining the temperature between -69 °C and -75

°C. The reaction mixture was stirred at -75 °C for 5 min and then

added to a stirred solution of tert-butyl carbazate (15.52 g, 117

mmol) in dry CH₂Cl₂(60 mL) at -7.5 °C. The reaction mixture

was stirred at -7.5 °C for 2 h and then poured into H₂O (100 mL).

The resulting mixture was extracted with CH₂Cl₂(2 × 400 mL).

The combined CH₂Cl₂extracts were successively washed with H₂O

(2 × 100 mL) and brine (1 × 50 mL) and dried over MgSO₄. The

MgSO₄was filtered off, and the filtrate was concentrated in Vacuo

to afford the crude product as an oil. This crude product was purified

by flash chromatography on silica gel, eluting with 1:1 hexane:

Et₂O to give the title compound as a clear oil (3.5 g, 50%).

N-[(tert-Butoxy)carbonylamino][7-chloro-4-oxo-2-(pyrrolidi-

nylcarbonyl)(3-hydroquinolinolyl)]-N-(3-phenylprop-2-ynyl)car-

boxamide. The title compound was prepared from 7-chloro-4-oxo-

2-(pyrrolidinylcarbonyl)hydroquinoline-3-carboxylic acid 7 (1.80

g, 5.61 mmol) and tert-butoxy-N-[(3-phenylprop-2-ynyl)amino]-

carboxamide (1.84 g, 7.47 mmol) according to Method A (2.84 g,

92%).

compound was prepared as a white solid from 7-chloro-4-oxo-2-

(pyrrolidinylcarbonyl)hydroquinoline-3-carboxylic acid (7) and N′-

(1-methyl-3-phenyl-prop-2-ynyl)-hydrazinecarboxylic acid tert-butyl

ester according to coupling Method A and cyclization Method D.

Yields for the coupling and cyclization were 44 and 34%,

1

respectively, mp 225-226 °C; H NMR (300 MHz, DMSO-d₆):

δ 1.61 (d, 3H, J ) 6.9 Hz); 6.17 (q, 1H, J ) 6.9 Hz); 7.34-7.45

(m, 6H); 8.04 (d, 1H, J ) 1.5 Hz); 8.15 (d, 1H, J ) 8.7 Hz); 11.98

(s, 1H); 12.83 (s, 1H). Anal. (C₂₁H₁₄ClN₃O₃‚0.6H₂O): C, H, N.

Compound 9ag. 7-Chloro-4,10-dihydroxy-2-(1-methyl-prop-

2-ynyl)-2H-pyridazino[4,5-b]quinolin-1-one. N-(1-Methyl-prop-

2-ynyl)-hydrazinecarboxylic Acid tert-Butyl Ester. To 3-butyn-

2-ol (10 mL, 127.55 mmol) in dry CH₂Cl₂(100 mL) under N₂was

added anhydrous Et₃N (28 mL, 193.7 mmol). The stirred mixture

was cooled to 0 °C. Dropwise addition of methanesulfonyl chloride

(11 mL, 142.1 mmol) in CH₂Cl₂(100 mL) resulted in formation

of a white precipitate. The mixture was stirred at 0 °C for 30 min.

The clear supernatant was then transferred to a solution of tert-

butyl carbazate (60 g, 453.99 mol) in anhydrous MeOH (200 mL)

via cannula at 0 °C over 15 min. The solids from the first flask

were washed with CH₂Cl₂, and the solution was also transferred to

the second reaction mixture. The initially clear reaction solution

became yellow and was stirred at 0 °C under N₂for 4 h. The

reaction mixture was allowed to warm to rt and after 3 d was

concentrated to a white solid. The solid was partitioned between

saturated aqueous NaCl (250 mL) and EtOAc. The aqueous layer

was extracted with EtOAc (2 × 200 mL), and the combined organic

layers were dried over Na₂SO₄and concentrated in Vacuo to give

a white solid (14.09 g, 60%). The crude material was diluted in

Et₂O/hexanes (100 mL:200 mL) and washed with H₂O (6 × 100

mL). The organic solution was dried over Na₂SO₄and concentrated

in Vacuo to give a white solid. This was crystallized from hexanes

to give the product as a white solid (12.29 g, 53%). ¹H NMR (300

MHz, DMSO-d₆): δ 1.15 (d, 3H, J ) 6.6 Hz), 1.39 (s, 9H), 3.07

(d, 1H, J ) 2.1 Hz), 3.73 (d, 1H, J ) 6.0 Hz), 4.58 (bs, 1H), 8.27

(bs, 1H).

N′-[7-Chloro-4-oxo-2-(pyrrolidine-1-carbonyl)-1,4-dihydro-

quinoline-3-carbonyl]-N′-(1-methyl-prop-2-ynyl)-hydrazinecar-

boxylic Acid tert-Butyl Ester. The title compound was prepared

from 7-chloro-4-oxo-2-(pyrrolidinylcarbonyl)hydro-quinoline-3-car-

boxylic acid (7) (5.31 g, 16.55 mmol) and N-(1-methyl-prop-2-

ynyl)-hydrazinecarboxylic acid tert-butyl ester (2.76 g, 15.0 mmol)

according to Method B. The crude yellow solid was chromato-

graphed over silica gel using a gradient of 99.5:0.5 to 97.5:2.5 CH₂-

Cl₂:MeOH. The pure product was obtained as a pale yellow solid

(7.08 g, 97%); ¹H NMR (300 MHz, DMSO-d₆): δ 1.28-1.03 (m,

9H), 1.35 (d, 3H, J ) 6.9 Hz), 1.87 (m, 4H), 3.47-3.31 (m, 6H),

7.51 (d, 1H, J ) 7.5 Hz), 7.64 (s, 1H), 8.18 (d, 1H, J ) 7.4 Hz),

9.02 (bs, 1H), 12.87 (bs, 1H).

7-Chloro-4,10-dihydroxy-2-(1-methyl-prop-2-ynyl)-2H-py-

ridazino[4,5-b]quinolin-1-one 9ag. The title compound was pre-

pared from N′-[7-chloro-4-oxo-2-(pyrrolidine-1-carbonyl)-1,4-

dihydroquinoline-3-carbonyl]-N′-(1-methyl-prop-2-ynyl)-

hydrazinecarboxylic acid tert-butyl ester (0.5222 g, 1.07 mmol) in

THF (30 mL) according to Method G. After drying under high

vacuum, the final product was obtained as an off-white solid (315.2

1

mg, 93%); H NMR (300 MHz, DMSO-d₆): δ 1.50 (d, 3H, J )

6.9 Hz), 3.31 (d, 1H, J ) 2.1 Hz), 4.83 (dq, 1H, J ) 6.9 Hz, J )

2.1 Hz), 7.44 (d, 1H, J ) 8.4 Hz), 8.03 (s, 1H), 8.14 (d, 1H, J )

8.7 Hz), 11.97 (bs, 1 H), 12.83 (bs, 1H).

7-Chloro-4-hydroxy-2-(3-phenylprop-2-ynyl)-2,5-dihydropy-

ridazino[4,5-b]quinoline-1,10-dione 9ah. The title compound was

prepared from N-[(tert-butoxy)carbonylamino][7-chloro-4-oxo-2-

(pyrrolidinylcarbonyl)(3-hydroquinolinolyl)]-N-(3-phenylprop-2-

ynyl)carboxamide (2.84 g, 5.17 mmol) according to Method E

except that the solids were sonicated in MeOH. The collected solids

were dried at 40 °C in Vacuo to give the title compound as a yellow

Compound 9ah. 7-Chloro-4-hydroxy-2-(3-(4-pyridyl)prop-2-

ynyl)-1,2,5,10-tetrahydropyridazino[4,5-b]quinoline-1,10-dione‚

1.3 Methanesulfonate. (tert-Butoxy)-N-(prop-2-ynylamino)-

carboxamide. A 5 L, three-neck flask equipped with mechanical

stirrer, thermometer, and 500 mL dropping funnel with N₂inlet

was charged with powdered K₂CO₃(124.03 g, 0.8975 mol), tert-

butyl carbazate (355.4 g, 2.692 mol), and 2.7 L of 9:1 THF:DMF.

To this stirred slurry was added a solution of propargyl bromide

(100 mL, 0.898 mol, 80% in toluene), which was dissolved in 300

mL of 9:1 THF:DMF, over 1.5 h. The reaction was stirred at

ambient temperature for 44 h. The mixture was then concentrated.

1

solid (1.55 g, 79%); mp >250 °C; H NMR (300 MHz, DMSO-

d₆): δ 4.97 (s, 2H); 7.4 (m, 6H); 8.02 (d, 1H, J ) 1.8 Hz); 8.14 (d,

1H, J ) 8.67 Hz); 11.97 (s, 1H); 12.85 (s, 1H). Anal. (C₂₀H₁₂-

ClN₃O₃): C, H, N.

Compound 9af. 7-Chloro-4,10-dihydroxy-2-(1-methyl-3-phen-

yl-prop-2-ynyl)-2H-pyridazino[4,5-b]quinolin-1-one. The title

3128 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 13

Bare et al.

The residue was partitioned between 1.5 L of CH₂Cl₂and 2 L of

H₂O. The aqueous layer was extracted with CH₂Cl₂(2 × 500 mL),

and the combined organics were washed with 1000 mL water, 200

mL brine (1×), and then 400 mL water:100 mL brine several times.

The organic layer was dried over Na₂SO₄and concentrated to give

a yellow oil. The crude product (365.4 g) was dissolved in 3 L of

Et₂O and was treated with 1.5 L of 1 N ethereal HCl over 3 h. The

thick white solids that formed were filtered and washed with Et₂O,

and the filtrates were concentrated to give the desired product as a

yellow oil (136.0 g). The oil was applied to a column containing

2.4 L of silica wet-packed in hexane. Elution was as follows:

hexane (2 L), 90:10 hexane:Et₂O (2 L), 80:20 hexane:Et₂O (2 L),

70:30 hexane:Et₂O (6 L). The pure product was obtained as a white

washed with H₂O and EtOAc. The combined filtrate and washes

were acidified to pH 2-3 using a 2 N HCl solution, and the organic

layer was removed in Vacuo. The remaining aqueous phase was

first extracted with toluene (3 × 50 mL), and then its pH was

adjusted to 7 by addition of K₂CO₃; the neutral aqueous solution

was further extracted with EtOAc (3 × 500 mL). The EtOAc

extracts were washed with H₂O, dried over MgSO₄, and concen-

trated in Vacuo. The residue gave the title compound as a yellow-

1

brown solid (10.07 g, 73% yield); H NMR (300 MHz, DMSO-

d₆); δ 4.34 (d, 2H, J ) 6 Hz); 5.44 (t, 1H, J ) 6 Hz); 7.41 (dd,

1H, J ) 8 Hz, J ) 5 Hz); 7.86 (dt, 1H, J ) 8 Hz, J ) 2. Hz); 8.56

(d, 1H, J ) 5. Hz), 8.63 (s, 1H).

3-(3-Bromoprop-1-ynyl)pyridine Hydrobromide. To a cold

(-10 °C), stirred solution of 3-(3-pyridyl)prop-2-yn-1-ol (6.67 g,

50 mmol), in alcohol-free CHCl₃(100 mL) under N₂, was added

PBr₃(3 mL, 8.55 g, 31.6 mmol). The reaction mixture was stirred

at -10 °C to 0 °C for 1.5 h and allowed to warm to rt. The upper,

clear yellow solution was transferred via a cannula to a new flask,

and the remaining brown reaction residue was washed with

additional CHCl₃(50 mL) which was then combined with the first

CHCl₃wash. Concentration of the combined CHCl₃washes gave

the title compound as a pale yellow solid. On vigorous stirring of

the residue in CHCl₃(100 mL) which did not dissolve in the CHCl₃

washes, a white precipitate formed which was collected by filtration,

washed with CHCl₃, and air-dried to provide the title compound

1

solid (83.6 g, 54%); H NMR (300 MHz, DMSO-d₆) δ 1.39 (s,

9H), 3.06 (s, 1H), 3.43 (s, 2H), 4.68 (s, 1H), 8.29 (bs, 1H).

N-[(tert-Butoxycarbonylamino][7-chloro-4-oxo-2-(pyrrolidi-

nylcarbonyl)(3-hydroquinolyl)]-N-prop-2-ynylcarboxamide. To

a stirred suspension of 7-chloro-4-oxo-2-(pyrrolidinylcarbonyl)-

hydroquinoline-3-carboxylic acid 7 (37.86 g, 0.118 mol) in THF

(600 mL) was added 1-cyclohexyl-3-(2-morpholinoethyl)carbodi-

imide metho-p-toluenesulfonate (100.0 g, 0.236 mol). The white

suspension became bright yellow immediately. To this stirred

suspension was added over 30 min a solution of (tert-butoxy)-N-

(prop-2-ynylamino)carboxamide (20.93 g, 0.123 mol) in THF (250

mL), and the reaction was stirred at ambient temperature for 24 h.

The reaction mixture was filtered, and the collected solids were

washed with THF. The filtrates and washes were combined and

concentrated. The residue was partitioned between 1.5 L of CH₂-

Cl₂and 1.5 L of water, and the aqueous layer was extracted once

with CH₂Cl₂. The combined organic layers were washed once with

brine, dried over MgSO₄, and concentrated. The residue was

chromatographed over silica gel using the following eluents: CH₂-

Cl₂(500 mL), 98:2 CH₂Cl₂/MeOH (2 L), 95:5 CH₂Cl₂/MeOH (4

L). The product was initially obtained as a foam which was then

triturated with 220 mL of 1:1 hexane:Et₂O to give the title

compound as a white powder (46.57 g, 83%); ¹H NMR (300 MHz,

DMSO-d₆) δ 1.42-1.18 (m, 9H), 1.86 (m, 4H), 3.44-3.36 (m,

6H), 4.20 (s, 1H), 7.50 (d, 1H, J ) 8.7 Hz), 7.64 (s, 1H), 8.18 (d,

1H, J ) 8,7 Hz), 8.73 (br s, 1H), 12.90 (br s, 1H).

1

as a pale yellow solid (total 9.90 g, 70%); H NMR (300 MHz,

DMSO-d₆); δ 4.61 (s, 2H); 7.86 (dd, 1H, J ) 8 Hz, J ) 5 Hz);

8.39 (dt, 1H, J ) 8 Hz, J ) 2 Hz); 8.83 (d, 1H, J ) 5. Hz), 8.99

(s,1H).

(tert-Butoxy)-N-[(3-(3-pyridyl)prop-2-ynyl)amino]carboxam-

ide. To a stirred mixture of tert-butyl carbazate (20.07 g, 151.9

mmol) and K₂CO₃(6.25 g, 45.2 mmol) in dry DMF (50 mL) was

added under N₂a solution of 3-(3-bromoprop-1-ynyl)pyridine

hydrobromide (4.50 g, 16.25 mmol) dissolved in DMF (100 mL).

The reaction mixture was stirred for 5 h at rt and was filtered

through diatomaceous earth to give a clear orange solution. The

pad was washed with EtOAc (100 mL) and MeOH (2 × 100 mL).

The organic filtrate and washes were combined, poured into water

(200 mL), and extracted with Et₂O (3 × 150 mL) followed by

EtOAc (2 × 200 mL). The organic extracts were combined, dried

over MgSO₄, filtered, and concentrated in Vacuo to give a mixture

of the desired product and a large excess of remaining tert-butyl

carbazate. This crude solid (∼43 g) was dissolved in a 1:3 Et₂O:

hexanes solution (400 mL) which was washed with saturated

aqueous NaHCO₃solution (6 × 200 mL). The organic material

was then dried over MgSO₄, filtered, and concentrated to give the

desired pure product as a yellow oil (2.11 g, 52% yield); ¹H NMR

(300 MHz, DMSO-d₆); δ 1.39 (s, 9H); 3.73 (d, 2H, J ) 4 Hz);

4.89 (b, NH) 7.42 (dd, 1H, J ) 8 Hz, J ) 5 Hz); 7.84 (d, 1H, J )

8 Hz); 8.42 (b, NH); 8.55 (d, 1H, J ) 3. Hz), 8.62 (d, 1H, J ) 4

Hz).

(tert-Butoxy)-N-{[7-chloro-4-oxo-2-(pyrrolidinylcarbonyl)(3-

hydroquinolyl)]-N-(3-(3-pyridyl)prop-2-ynyl)carbonylamino}-

carboxamide. The title compound was prepared from 7-chloro-4-

oxo-2-(pyrrolidinylcarbonyl)hydroquinoline-3-carboxylic acid 7

(4.53 g, 14.12 mmol) and (tert-butoxy)-N-[(3-(3-pyridyl)prop-2-

ynyl)amino]carboxamide (3.49 g, 14.11 mmol) as described in

Method B except that the reaction was not heated (complete after

14 h at rt). The desired compound was obtained as a yellow solid

(1.83 g, 24%).

N-[(tert-Butoxy)carbonylamino][7-chloro-4-oxo-2-(pyrrolidi-

nylcarbonyl)(3-hydroquinolyl)]-N-(3-(4-pyridyl)prop-2-ynyl)car-

boxamide. The title compound was prepared from N-[(tert-

butoxy)carbonylamino][7-chloro-4-oxo-2-(pyrrolidinylcarbonyl)(3-

hydroquinolyl)]-N-prop-2-ynylcarboxamide (0.832 g, 1.76 mmol)

and 4-iodopyridine (0.327 g, 1.59 mmol) according to Method C

as a slightly impure oil after the initial column chromatography

(0.93 g, 106%). The material was cyclized without further purifica-

tion.

7-Chloro-4-hydroxy-2-(3-(4-pyridyl)prop-2-ynyl)1,2,5,10-tet-

rahydropyridazino[4,5-b]quinoline-1,10-dione‚1.3 Methane-

sulfonate 9ah. The title compound was prepared from N-[(tert-

butoxy)carbonylamino][7-chloro-4-oxo-2-(pyrrolidinylcarbonyl)(3-

hydroquinolyl)]-N-(3-(4-pyridyl)prop-2-ynyl)carboxamide (0.87 g,

1.59 mmol) according to Method D. The final material was obtained

1

as a light tan solid (396.2 mg, 66%), mp 238-241 °C; H NMR

(300 MHz, DMSO-d₆) δ 2.32 (s, 4Η), 5.06 (s, 2H), 7.45 (d, 1H, J

) 8.4 Hz), 7.66 (d, 2H, J ) 4.5 Hz), 8.04 (s, 1H), 8.15 (d, 1H, J

) 8.4 Hz), 8.71 (s, 2H), 12.0 (br s, 1 H, exchangeable), 12.9 (br s,

1 H, exchangeable). Anal. (C₁₉H₁₁ClN₄O₃‚1.3CH₃SO₃H): C, H,

N.

Compound 9ai. 7-Chloro-4-hydroxy-2-(3-(3-pyridyl)prop-2-

ynyl)-1,2,5,10-tetrahydropyridazino[4,5-b]quinoline-1,10-di-

one Methanesulfonate. 3-(3-Pyridyl)prop-2-yn-1-ol. To a stirred

solution of 1:1 1,2-dimethoxyethane:water (250 mL), under N₂,

were added K₂CO₃(29.5 g, 213 mmol), 3-bromopyridine (10 mL,

103.8 mmol), PPh₃(3.24 g, 12.4 mmol), copper(I) iodide (1.96 g,

10.30 mmol), and 10% Pd/C (3.22 g, 3.02 mmol Pd). The reaction

mixture was stirred for 20 min at rt, and then propargyl alcohol

(15 mL, 257.7 mmol) was added. The reaction mixture was heated

at 80 °C for 14 h and allowed to cool to rt. The reaction mixture

was filtered through diatomaceous earth, and the solids were then

7-Chloro-4-hydroxy-2-(3-(3-pyridyl)prop-2-ynyl)-1,2,5,10-tet-

rahydropyridazino[4,5-b]quinoline-1,10-dione Methanesulfonate

9ai. The title compound was prepared from (tert-butoxy)-N-{[7-

chloro-4-oxo-2-(pyrrolidinylcarbonyl)(3-hydroquinolyl)]-N-(3 -(3-

pyridyl)prop-2ynyl)carbonylamino}carboxamide (1.83 g, 3.33 mmol)

as described in Method G except that the solids were washed with

H₂O, MeOH, and Et₂O and then air-dried. The filtrate was dried

overnight at 45 °C in Vacuo to give the title compound (0.645 g,

1

40%) as a yellow solid, mp 227-229 °C; H NMR (300 MHz,

DMSO-d₆): δ 5.01 (s, 2H); 7.42-7.49 (m, 2H); 7.92 (d, 1H, J )

7 Hz); 8.04 (s, 1H); 8.15 (d, 1H, J ) 9 Hz); 8.59 (d, 1H, J ) 4

AntinociceptiVe NMDA Glycine-Site Antagonists

Journal of Medicinal Chemistry, 2007, Vol. 50, No. 13 3129

Hz); 8.67 (s, 1H); 11.94 (br s, 1H, exchangeable); 12.81 (br s, 1H,

exchangeable). Anal. (C₁₉H₁₁ClN₄O₃‚1.2 H₂O‚1.0 CH₃SO₃H): C,

H, N.

(s, 2H); 7.15 (dd, 1H, J ) 5.1 Hz, J ) 1.2 Hz); 7.44 (dd, 1H, J )

8.7 Hz, J ) 1.8 Hz); 7.59 (m, 1H); 7.7 g (m, 1H); 8.03 (d, 1H, J

) 1.5 Hz); 8.15 (d, 1H, J ) 1.5 Hz); 11.98 (s, 1H); 12.85 (s, 1H).

Anal. (C₁₈H₁₀ClN₃O₃S.0.75 H₂O): C, H, N.

Compound 9aj. 7-Chloro-4-hydroxy-2-(3-(3-thienyl)prop-2-

ynyl)-2,5-dihydropyridazino[4,5-b]quinoline-1,10-dione. 3-(3-

Thienyl)prop-2-yn-1-ol. To a stirred solution of 1:1 1,2-dimethox-

yethane:H₂O (100 mL) were added 3-bromothiophene (4.89 g, 30

mmol), K₂CO₃(10.3 g, 75 mmol), CuI (0.23 g, 1.2 mmol), PPh₃

(0.64 g, 2.4 mmol), and 10% Pd/C (0.630 g, 0.6 mmol Pd). The

reaction mixture was stirred for 20 min at rt, and then propargyl

alcohol (7.3 mL, 75 mmol) was added. The reaction mixture was

heated at 80 °C for 16 h and allowed to cool to rt. The reaction

mixture was filtered through diatomaceous earth, and the filtrate

was extracted with EtOAc (350 mL). The EtOAc solution was

washed with H₂O (250 mL) and dried over Na₂SO₄. The filtrate

was filtered and concentrated in Vacuo to give an amber oil (4.86

g). This crude product was purified by flash chromatography on

silica gel, eluting with 3:2 hexane:EtOAc to give the title compound

Compound 9ak. 7-Chloro-4-hydroxy-2-(3-(2-thienyl)prop-2-

ynyl)-2,5-dihydropyridazino[4,5-b]quinoline-1,10-dione. 3-(2-

Thienyl)prop-2-yn-1-ol. The title compound was prepared from

2-iodothiophene (6.30 g, 30 mmol) and propargyl alcohol (7.3 mL,

75 mmol) as described for 3-(3-thienyl)prop-2-yn-1-ol except that

the diatomaceous earth was washed with DME (3 × 20 mL), and

the crude residue was purified by flash chromatography on silica

gel using a gradient of 75:25 to 50:50 hexanes:Et₂O as the eluent.

The desired compound was obtained as a light beige oil (2.90 g,

70%); ¹H NMR (300 MHz, DMSO-d₆); δ 4.32 (d, 2H, J ) 6 Hz);

5.38 (t, 1H, J ) 6 Hz); 7.07 (m, 1H); 7.30 (d, 1H, J ) 2.7 Hz);

7.58 (dd, 1H, J ) 5.1 Hz; J ) 1.2 Hz).

2-(3-Chloroprop-1-ynyl)thiophene. The title compound was

prepared from 3-(2-thienyl)prop-2-yn-1-ol (2.9 g, 21 mmol) as

described for 3-(3-thienyl)prop-2-yn-1-ol except that the reaction

mixture was cooled and concentrated under reduced pressure to

give a brown oil which was purified directly by flash chromatog-

raphy on silica gel, eluting with CH₂Cl₂:MeOH (1:1) to give the

title compound as an amber oil (3.2 g, 98%).

(tert-Butoxy)-N-[(3-(2-thienyl)prop-2-ynyl)amino]carboxam-

ide. The title compound was prepared from 2-(3-chloroprop-1-ynyl)-

thiophene (3.20 g, 20.4 mmol) and tert-butyl carbazate (27.075 g,

204.8 mmol) as described for (tert-butoxy)-N-[(3-(3-thienyl)prop-

2-ynyl)amino]carboxamide except that the reaction mixture was

extracted with EtOAc (2 × 100 mL) and the combined organic

extracts were washed with H₂O (2 × 100 mL). After removal of

the solvent in Vacuo, the residue (3.4 g) was purified by flash

chromatography on silica gel using 1:1 hexane:Et₂O as the eluent

to give the desired product as a light amber oil (1.6 g, 32%).

(tert-Butoxy)-N-{[7-chloro-4-oxo-2-(pyrrolidinylcarbonyl)(3-

hydroquinolyl)]-N-(3-(2-thienyl)prop-2-ynyl)carbonylamino}-

carboxamide. The title compound was prepared from 7-chloro-4-

oxo-2-(pyrrolidinylcarbonyl)hydroquinoline-3-carboxylic acid 7

(2.03 g, 6.34 mmol) and (tert-butoxy)-N-[(3-(2-thienyl)prop-2-ynyl)-

amino]carboxamide (1.60 g, 6.34 mmol) according to Method B

except that the collected solids were washed with THF (20 mL).

The desired product was obtained as a yellow foam (1.24 g, 35%).

7-Chloro-4-hydroxy-2-(3-(2-thienyl)prop-2-ynyl)-2,5-dihydro-

pyridazino[4,5-b]quinoline-1,10-dione 9ak. The title compound

was prepared from (tert-butoxy)-N-{[7-chloro-4-oxo-2-(pyrrolidi-

nylcarbonyl)(3-hydroquinolyl)]-N-(3-(2-thienyl)prop-2ynyl)-

carbonylamino}carboxamide (1.24 g, 2.20 mmol) as described in

Method G except that following isolation by filtration the solids

were slurried and filtered twice from CH₂Cl₂(2 × 25 mL) and

then dried overnight at 50 °C in Vacuo to give title compound as

a beige powder (0.287 g, 34% yield); mp ) 235-237 °C; ¹H NMR

(300 MHz, DMSO-d₆): δ 4.99 (s, 2H); 7.06 (t, 1H, J ) 4.4 Hz);

7.33 (d, 1H, J ) 3.3 Hz); 7.44 (d, 1H, J ) 8.4 Hz); 7.61 (d, 1H,

J ) 4.8 Hz); 8.03 (s, 1H); 8.15 (d, 1H, J ) 8.7 Hz); 11.98 (s, 1H);

12.86 (s, 1H); Anal. (C₁₈H₁₀ClN₃O₃S‚1.0 H₂O): C, H, N

1

as a light amber oil (2.57 g, 62%); H NMR (300 MHz, DMSO-

d₆); δ 4.26 (d, 2H, J ) 6 Hz); 5.32 (t, 1H, J ) 6 Hz); 7.15 (dd,

1H, J ) 5.1 Hz, J ) 0.9 Hz); 7.57 (m, 1H); 7.75 (m, 1H).

3-(3-Chloroprop-1-ynyl)thiophene. To a stirred solution of 3-(3-

thienyl)prop-2-yn-1-ol (2.5 g, 1.8 mmol), Et₂O (25 mL), and Et₃N

(5.4 g, 54 mmol) was added thionyl chloride (6.46 g, 54 mmol) at

0 °C. The reaction mixture was allowed to warm to rt and was

then heated at reflux for 1 h. The reaction mixture was cooled, and

Et₂O (50 mL) was added. The resulting mixture was washed with

H₂O (2 × 25 mL) and dried over Na₂SO₄. The Na₂SO₄was filtered

off, and the filtrate was concentrated under reduced pressure to

give a brown oil (3.14 g). This crude product was purified by flash

chromatography on silica gel, eluting with 1:1 Et₂O:hexanes to give

1

the title compound as an amber oil (1.26 g, 47%); H NMR (300

MHz, DMSO-d₆); δ 4.69 (s, 2H); 7.20 (dd, 1H, J ) 5.1 Hz; J )

1.2 Hz); 7.64 (m, 1H); 7.88 (m, 1H).

(tert-Butoxy)-N-[(3-(3-thienyl)prop-2-ynyl)amino]carboxam-

ide. To a stirred mixture of tert-butyl carbazate (10.66 g, 80 mmol),

K₂CO₃(3.3 g, 24 mmol) and dry DMF (30 mL) under N₂was added

3-(3-chloroprop-1-ynyl)thiophene (1.26 g, 8 mmol). The reaction

mixture was stirred overnight (18 h) at rt. The reaction mixture

was diluted with H₂O (150 mL), and the resulting mixture extracted

with Et₂O (2 × 50 mL). The combined Et₂O extracts were

concentrated under reduced pressure, and the residue was dissolved

in 1:1 hexanes:Et₂O (100 mL). The resulting solution was washed

with H₂O (4 × 50 mL) and dried over Na₂SO₄. The Na₂SO₄was

filtered off, and the filtrate was concentrated under reduced pressure

to give an amber oil (2.12 g). This crude product was purified by

flash chromatography on silica gel eluting with 1:1 Et₂O:hexanes

to give the title compound as an amber oil (1.57 g, 78%); ¹H NMR

(300 MHz, DMSO-d₆): δ 1.39 (m, 9H); 3.68 (s, 2H); 4.8 (bs, 1H);

7.12 (dd, 1H, J ) 5.1 Hz, J ) 0.6 Hz); 7.61 (m, 1H); 7.71 (m,

1H); 8.37 (bs, 1H).

(tert-Butoxy)-N-{[7-chloro-4-oxo-2-(pyrrolidinylcarbonyl)(3-

hydroquinolyl)]-N-(3-(3-thienyl)prop-2-ynyl)carbonylamino}-

carboxamide. The title compound was prepared from 7-chloro-4-

oxo-2-(pyrrolidinylcarbonyl)hydroquinoline-3-carboxylic acid 7 (2.0

g, 6.23 mmol) and (tert-butoxy)-N-[(3-(3-thienyl)prop-2-ynyl)-

amino]carboxamide (1.57 g, 6.23 mmol) as described in Method

B except that the reaction was stirred at rt for 0.5 h heated at 50

°C for 10 min and then allowed to cool to rt, the reaction mixture

was filtered, and the filter cake was washed with THF (2 × 20

mL). After purification, the desired title compound was obtained

as a yellow foam (2.26 g, 64%).

Biological/Physical Properties Assays. [³H]-MDL105,519 Bind-

ing Assay. Fresh rat brain tissue including cortex and hippocampus

was homogenized in 0.32 M sucrose and centrifuged at low speed

to separate cell membrane from the rest of cell parts. The

membranes were washed three times using deionized water,

followed by treatment with 0.04% Triton X-100. Membranes were

then washed six times in 50 mM Tris-acetate, pH 7.4, and frozen.

The rat brain membranes were stored at -80 °C. The day of the

experiment brain membranes were thawed and suspended in Tris-

acetate buffer (50 mM Tris-acetate, pH 7.4). For competition,

binding membranes (85 mg/mL) were incubated with 1.2 nM [³H]-

MDL105,519 (72Ci/mmol) for 30 min at rt in a total volume of

250 µL. Then, 100 µM of unlabeled MDL105,519 was used to

define nonspecific binding. Compounds were dissolved as 10 or 1

mM stock solutions in water or dimethyl sulfoxide (DMSO). DMSO

concentration was kept below 1%. Unbound [³H]-MDL105,519 was

7-Chloro-4-hydroxy-2-(3-(3-thienyl)prop-2-ynyl)-2,5-dihydro-

pyridazino[4,5-b]quinoline-1,10-dione 9aj. The title compound

was prepared from (tert-butoxy)-N-{[7-chloro-4-oxo-2-(pyrrolidi-

nylcarbonyl)(3-hydroquinolyl)]-N-(3-(3-thienyl)prop-2ynyl)-

carbonylamino}carboxamide (1.26 g, 2.2 mmol) as described in

Method G except that the collected solids were successively washed

with H₂O (2 × 25 mL) and MeOH (2 × 25 mL) and then dried at

50 °C in Vacuo to give title compound as a beige powder (502 mg,

1

59%); mp 248-250 °C; HNMR (300 MHz, DMSO-d₆): δ 4.92

3130 Journal of Medicinal Chemistry, 2007, Vol. 50, No. 13

Bare et al.

separated from bound by filtration on to GF/B Uniplates using

Packard harvester. Filters were washed 3-5 times with ice cold

binding buffer. The plates were left to dry overnight. A 35 µL

amount of the microscint O was added to each well, and bound

radioactivity was counted on a Packard Top Count.

Measurement of Aqueous Solubility. A known amount of test

compound was incubated in 0.1 M pH 7.4 sodium phosphate buffer

with or without 0.26 N NaCl for 24 h at 25 °C in a 1.5 mL

centrifuge tube. After centrifugation at 12000 rpm for 30 min, the

supernatant was transferred to a new vial and analyzed by HPLC-

UV. A standard solution of the test compound dissolved in DMSO

was used as the calibration standard for quantitation.

Garlapati for in Vitro screening; JoAnne Smolka, Chris Tyler,

and Sheree Logue for in ViVo pharmacology studies; Mary Jo

Bock for bioanalysis; Yun Alelyunas, James A. Osborn, and

Bill George for physical property determinations; David Gurley

for molecular pharmacology studies; Jim Hall for NMR as-

sistance; Tim Blake for HPLC-MS determinations; Bill Michne

for scientific discussions. We also acknowledge the efforts of

the custom synthesis laboratory at AstraZeneca-Wilmington and

the AstraZeneca process chemistry group at Macclesfield in the

UK for providing large-scale synthetic intermediates for use in

this program.

Measurement of log D. The octanol-water partition coefficient

(log D) of test compound was determined based on the shake-flask

principle using volume ratio of 10 mL 0.01 M octanol saturated

sodium phosphate buffer at pH 7.4 and 100 µL of buffer saturated

octanol. The aqueous buffer layer was sampled both before and

after partitioning and quantified by HPLC-UV. Log D was

calculated by the following equation log D ) log(100 ([before -

after]/[after])).

Supporting Information Available: Elemental analysis and

HPLC data. This material is available free of charge via the Internet

at http://pubs.acs.org.

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JM060212S

Article Doi

Pyridazinoquinolinetriones as NMDA glycine-site antagonists with oral antinociceptive activity in a model of neuropathic pain

DOI: 10.1021/jm060212s

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Full text of DOI:10.1021/jm060212s

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