Discovery and synthesis of hydronaphthoquinones as novel proteasome inhibitors

Article

pubs.acs.org/jmc

Discovery and Synthesis of Hydronaphthoquinones as Novel

Proteasome Inhibitors

Yiyu Ge,^†,‡,⊥Aslamuzzaman Kazi,^†,⊥Frank Marsilio,^‡Yunting Luo,^‡Sanjula Jain,^†Wesley Brooks,^‡

Kenyon G. Daniel,^‡Wayne C. Guida,^{†,‡,∥,§}Saïd M. Sebti,^†,§and Harshani R. Lawrence*^,†,‡

^†Drug Discovery Department, Moffitt Cancer Center, 12902 Magnolia Drive, Tampa, Florida 33612, United States

^‡Chemical Biology Core, Moffitt Cancer Center, 12902 Magnolia Drive, Tampa, Florida 33612, United States

^§Department of Oncologic Sciences, University of South Florida, Tampa, Florida 33620, United States

^∥Department of Chemistry, University of South Florida, Tampa, Florida 33620, United States

S

* Supporting Information

ABSTRACT: Screening efforts led to the identification of PI-

8182 (1), an inhibitor of the chymotrypsin-like (CT-L) activity

of the proteasome. Compound 1 contains a hydronaphtho-

quinone pharmacophore with a thioglycolic acid side chain at

position 2 and thiophene sulfonamide at position 4. An

efficient synthetic route to the hydronaphthoquinone

sulfonamide scaffold was developed, and compound 1 was

synthesized in-house to confirm the structure and activity

(IC₅₀= 3.0 1.6 μM [n = 25]). Novel hydronaphthoquinone

derivatives of 1 were designed, synthesized, and evaluated as

proteasome inhibitors. The structure−activity relationship (SAR) guided synthesis of more than 170 derivatives revealed that the

thioglycolic acid side chain is required and the carboxylic acid group of this side chain is critical to the CT-L inhibitory activity of

compound 1. Furthermore, replacement of the carboxylic acid with carboxylic acid isosteres such as tetrazole or triazole greatly

improves potency. Compounds with a thio-tetrazole or thio-triazole side chain in position 2, where the thiophene was replaced

by hydrophobic aryl moieties, were the most active compounds with up to 20-fold greater CT-L inhibition than compound 1

(compounds 15e, 15f, 15h, 15j, IC₅₀values around 200 nM, and compound 29, IC₅₀= 150 nM). The synthetic iterations

described here not only led to improving potency in vitro but also resulted in the identification of compounds that are more

active such as 39 (IC₅₀= 0.44 to 1.01 μM) than 1 (IC₅₀= 3.54 to 7.22 μM) at inhibiting the proteasome CT-L activity in intact

breast cancer cells. Treatment with 39 also resulted in the accumulation of ubiquitinated cellular proteins and inhibition of tumor

cell proliferation of breast cancer cells. The hit 1 and its analogue 39 inhibited proteasome CT-L activity irreversibly.

for cancer therapy.¹⁰In addition, several studies have shown

that proteasome inhibition is also important for inflammatory

INTRODUCTION

Regulated protein degradation is an essential aspect of cell

■

and autoimmune diseases.^11,12Most natural and synthetic

proteasome inhibitors reported to date including Bortezomib

contain a reactive moiety in the pharmacophore that forms an

irreversible and/or slowly reversible covalent bond with the

nucleophilic N-terminal Thr in the β5 subunit of the

proteasome.^13,14Proteasome inhibitors reported to date fall

into five classes:¹⁵peptide boronates, peptide aldehydes,

peptide vinyl sulfones, peptide epoxyketones, and β-lactones.

Peptide aldehydes and vinyl sulfones also inhibit other

proteases (cathepsin A, tripeptidyl peptidase II) in addition

to the proteasome.¹⁶The β-lactone salinosporamide A^17,18and

tetrapeptide epoxyketone Carfilzomib¹⁹(Figure 1) represent

two classes of irreversible and/or slowly reversible proteasome

inhibitors that are in clinical trials.²⁰The proteolytic activity of

the chymotrypsin-like (CT-L) active site (β5 subunit) of the

signaling.¹In 2004, Ciechanover,²Hershko,³and Rose⁴were

awarded the Nobel Prize for chemistry in elucidating the

importance of proteolytic degradation inside cells and the role

of ubiquitin in proteolytic pathways. Proteasomes are highly

conserved compartmentalized protease complexes belonging to

the family of N-terminal nucleophilic hydrolases.⁵The

proteasome degrades ubiquitinated proteins into small

peptides,⁶and the ubiquitin proteasome system (UPS) is

responsible for the degradation of cellular proteins (e.g.,

potentially toxic, oxidized, misfolded proteins, and cell cycle

regulatory proteins). In cancer cells, the UPS is essential to the

mechanisms underlying tumorigenesis, metastasis, angiogenesis,

and apoptosis.⁷⁻⁹Therefore, targeting the regulation of protein

production and degradation that mediates proliferation and

other hallmarks characteristics of malignancy has been a major

focus of cancer research. Since the approval of Bortezomib

(Velcade) for multiple myeloma in 2003 by the FDA (Figure

1), the proteasome has been validated as an important target

Received: August 19, 2011

Published: January 5, 2012

1978

dx.doi.org/10.1021/jm201118h | J. Med. Chem. 2012, 55, 1978−1998

Journal of Medicinal Chemistry

Article

Figure 1. Structures of representative proteasome inhibitors: Bortezomib (clinically approved), Carfilzomib (in clinical trials), and the proteasome

activity profile of the “hit” 1.

proteasome cleaves peptides that contain amino acid residues

with large hydrophobic side chains.¹³The trypsin-like (T-L, β2

subunit) and postglutamylpeptidase hydrolysis (PGPH, β1

subunit) proteolytic sites of the proteasome cleave peptides

after acidic and basic amino acid residues, respectively.¹³

Therefore, the selectivity of proteasome inhibition using

peptide based compounds would be hard to achieve just by

simply manipulating the peptide backbone. Examples of

nonpeptidic, small drug-like synthetic molecules which act as

proteasome inhibitors are rare, and these molecules would have

potential advantages over the existing inhibitors for therapeutic

interventions. Recently, we disclosed identification of PI-083

(NSC-45382), a small synthetic molecule with a naphthoqui-

none pharmacophore as a reversible proteasome inhibitor that

selectively targets cancer cells over nontransformed cells in

vitro as well as in vivo.^21,22In the course of our search for new

classes of inhibitors of the 20S proteasome, compound 1

(Figure 1) was recently identified and characterized as a “hit”

for proteasome inhibition with CT-L inhibitory activity from

our in-house ChemDiv library. The synthesis of compound 1 is

not reported in the literature. Herein we describe an efficient

synthetic route to 1 and detailed in vitro structure−activity

relationship (SAR) studies of 1 via focused library synthesis as a

part of our ongoing efforts in the development of proteasome

inhibitors.

Figure 2. A. Proposed synthetic modifications around compound 1

(hit); B. side chain at 1-position to probe interactions.

aminonaphthol hydrochloride salt (2) and thiophene-2-sulfonyl

chloride in good yields (Scheme 1). The intermediate 3 was

easily obtained with high yields (Scheme 1, condition a, this

reaction is reported with NaHCO₃as a base with moderate

yields²³) and reacted with hydrogen peroxide and 4 M HCl in

dioxane solution, similar to a literature reported protocol²⁴to

obtain the compound 4a. Compounds 4b and 4c were also

synthesized in a similar manner in the presence of bromine and

iodine respectively with triethylamine in DMF (Scheme 1)

according to a reported method²⁵(see ¹H NMR and HRMS of

4a, 4b, and 4c in the Experimental Section). Our strategy was

to oxidize the hydronaphthoquinone 4a to obtain the oxidized

2-chloronaphthoquinone (structure shown for oxidized 4a in

Scheme 1) that would facilitate the synthesis of the final

compound 1. Our attempts to oxidize compound 4a (using

H₂O₂, Pb(OAc)₄) were not successful. Furthermore, attempts

to directly introduce the thioether carboxylic ester side chain in

compound 1 via the intermediate 5 (Scheme 1), similar to a

reported protocol with hydrazides²⁶and thiols,²⁷were not

successful. Syntheses of derivatives of intermediate 5 are

reported from derivatives of compound 3 using lead (IV)

tetraacetate²²in acetic acid, hydrogen peroxide,²³or MnO₂²⁸in

methanol. In spite of repeated attempts, we were unable to

obtain the required oxidized intermediate 5 from the

hydroxynaphthalene sulfonamide intermediate 3 using these

reported protocols. Our reactions produced unidentified

CHEMISTRY

■

Compound 1 was recently identified in our program as a “hit”

from our in-house ChemDiv 20000 compound library that

showed CT-L proteasome inhibitory activity with an IC₅₀value

of 3.0

1.6 (n = 25, >95% pure by HPLC). This result

prompted us to further investigate 1 as a proteasome inhibitor

and establish structure and activity relationship studies (SAR)

via synthetic modifications around the hydronaphthoquinone

pharmacophore. The hydronaphthoquinone pharmacophore in

compound 1 exhibits desirable structural diversity that was

exploited for focused library synthesis and medicinal chemistry.

Synthetic modifications were primarily focused on the side

chain at the 2-position of the hydronaphthoquinone

pharmacophore (Figure 2), and the sulfonamide moiety of 1

to understand the structural moieties responsible for

proteasome inhibition. Proposed synthetic modifications to

probe binding interactions in the β5 subunit of the proteasome

are described in Figure 2.

1

impurities by H NMR and TLC. Hence, this route to obtain

compound 1 was abandoned.

To combine the hydronaphthoquinone ring and the

thioether side chain in structure 1 as required, we then

A synthetic route to compound 1 is not reported to the best

of our knowledge. Initially, halogenated hydronaphthoquinones

4a−c were synthesized starting from commercially available 4-

1979

dx.doi.org/10.1021/jm201118h | J. Med. Chem. 2012, 55, 1978−1998

Journal of Medicinal Chemistry

Article

a

Scheme 1. Synthesis of Hydronaphthoquinone Sulfonamide Scaffold

a

Reagents and conditions: (a) thiophene-2-sulfonyl chloride, Et₃N, dichloromethane, rt, 14 h, 90%; (b) for 4a, (i) H₂O₂(35%), CH₃OH, rt, 2 h, (ii)

4 M HCl/dioxane, rt, 2 h, 22%; for 4b, Br₂, Et₃N, DMF, 0 °C to rt, 12−14 h, 36%, and for 4c, I₂, Et₃N, DMF, 0 °C to rt, 12 h, 100%.

a

Scheme 2. Synthetic Route to Compound 1 (Hit) and Derivatives of the Hit

a

Reagents and conditions: (a) HS(CH₂)_nCOOR¹(R¹= ethyl, n = 1 for 8a, 89% and R¹= methyl, n = 2 for 8b, 94%), ethanol (2.5 mL/mmol), rt 0.5

h; (b) BrCH₂COO^tBu, Ag₂O, CHCl₃, cat. KI, reflux under Ar, 36 h, 33%; (c) R²SO₂NH₂, TiCl₄·2THF, Et₃N, DCM, microwave, 60 °C, 5−20 min,

26−62%; (d) Na₂S₂O₄, THF, 1 h, rt or EtOAc, H₂O, rt 10 min, 59−93%; (e) oxone, H₂O, acetone, rt, 12−14 h, 100%; (f) conc HCl/dioxane (1:1,

16 mL/mol), rt 3−36 h or microwave, 100 °C, 10 min, 54−97%.

validated the synthetic protocols shown in Schemes 2 and 3.

Commercially available 1,4-naphthoquinone (6) (Scheme 2), 2-

hydroxy-1,4-naphthoquinone (7) (Scheme 2), or 2-chloro-1,4-

naphthoquinone (12) (Scheme 3) were used as starting

materials. First, naphthoquinone intermediates 8a and 8b

were obtained in good yield using ethyl 2-mercaptoacetate (one

carbon side chain) or methyl 3-mercaptopropionate (2-carbon

side chain), respectively, with 2 equiv of 1,4-naphthoquinone

(6) using EtOH as the solvent. (Scheme 2, condition a). The

intermediate 8c was obtained via alkylation of 2-hydroxy-1,4-

naphthoquinone (7) with tert-butyl bromoacetate using

silver(I) oxide as a base using a reported protocol (Scheme

2, condition b).²⁹The sulfonamide building blocks that were not

commercially available were synthesized according to a

reported protocol.³⁰The sulfonamide building blocks either

commercially available or in-house synthesized were then

regioselectively coupled to naphthoquinone intermediates 8a−

c according to a procedure that has been widely used in the

formation of sulfonimide building blocks³¹using titanium(IV)

chloride and triethylamine with conventional heating. We

modified the conditions of this reaction (i.e., synthesis of

intermediate 9 in Scheme 2, condition c) using microwave

assisted heating (60 °C, 5−20 min, 26−62% yield) to

accommodate parallel synthesis. This reaction was a key

reaction in building the sulfonimide naphthoquinone scaffold 9

in our synthetic route to final compounds and microwave

assisted heating was convenient for library synthesis. Coupling

intermediates 8 with various sulfonamides proceeded regiose-

lectively at the 4-carbonyl of the naphthoquinone ring. We

observed the change of the chemical shift of hydrogen at 3-

position of 8a from 6.7 to 7.9 ppm in 9a (see NMR spectra in

Supporting Information). However, the coupling reactions of 3-

methyl substituted naphthoquinone (i.e., 8 with a methyl group

at 3-position, Scheme 2) with arylsulfonamides were not

1980

dx.doi.org/10.1021/jm201118h | J. Med. Chem. 2012, 55, 1978−1998

Journal of Medicinal Chemistry

Article

a

Scheme 3. Optimized Synthetic Route to Hit and Final Compounds

a

Reagents and conditions: (a) R¹SO₂NH₂, TiCl₄·2THF, or 1 M TiCL₄in DCM, Et₃N, THF, microwave, 60 °C, 15−30 min, 30−86%; (b)

EtOH:DCM (1:1) for tetrazole-5-thiol, rt, 2 h, THF for 1-methyl-tetrazole-5-thiol or 3-mercapto-1,2,4-triazole, rt, 2 h, THF, 1 equiv pyridine for

thioglycolic acid, rt, 10−30 min; (c) Na₂S₂O₄, EtOAc, and H₂O (mixing in a separating funnel), 54−100%; (d) NaN₃, water, reflux 2 h, 67%; (e)

TFA/anisole (5:1, 2 mL/mmol), microwave 100 °C, 2 h, 93%.

successful using this protocol, possibly due to the steric

hindrance of the adjacent methyl group.

intermediates 9 laborious and inconvenient for library syn-

thesis. Therefore, further optimization of the synthetic route

was carried out with commercially available 2-chloro-1,4-

naphthoquinone (12) as shown in the Scheme 3.

In the coupling reactions with intermediate 8, formation of

several impurities were observed by TLC, and one of the major

byproduct formed was shown to be the reduced structure

hydronaphthoquinone (i.e., compound 10). We were able to

isolate this impurity using SiO₂chromatography and confirmed

it to be, by NMR and LCMS, the hydronaphthoquinone

derivative 10. The key intermediates 9 were reduced in situ

using sodium hydrosulfite³²to hydronaphthoquinone carbox-

ylic esters 10 (Scheme 2, condition d). Hydrolysis of 10 in a 1:1

mixture of concentrated HCl and dioxane gave the final

hydronaphthoquinone acid library 11 in moderate yield

(Scheme 2, condition f). Compound 1 (Figure 1) was

synthesized via this route to confirm the structure and CT-L

proteasome inhibitory activity. The sulfone moiety in

compound 11e was formed by oxidation of compound 10a

with oxone,³³followed by acid hydrolysis (Scheme 2, conditions

e and f). The byproduct formation in the sulfonamide coupling

reaction (i.e., step c in Scheme 2) made the isolation of

The hydronaphthoquinone focused library 15 (Scheme 3)

was synthesized via coupling various sulfonamides to

commercially available 2-chloro-1,4-naphthoquinone (12)

using the same synthetic protocol validated for naphthoquinone

intermediate 9 (Scheme 2, condition c). The yield of this

reaction was significantly improved from 56% to 83% by

replacing DCM with THF (Scheme 3, condition a). The key

intermediates 13 (Scheme 3) were then easily purified by either

recrystallization or triturating from appropriate solvents (see

Experimental Section), which was more convenient for library

synthesis. Substitution of the 2-chlorine intermediates 13 with

various nucleophiles was carried out in the presence of pyridine

when thioglycolic acid was used and without a base when

tetrazole-5-thiol (Scheme 3, condition b), 1-methyl-tetrazole-5-

thiol or 3-mercapto-1,2,4-triazole (commercially available

building blocks) was used to generate the library 14 with the

1981

dx.doi.org/10.1021/jm201118h | J. Med. Chem. 2012, 55, 1978−1998

Journal of Medicinal Chemistry

Article

a

Scheme 4. Synthesis of the Thioglycolic Acid Side Chain at 1-Position

a

Reagents and conditions: (a) 15 equiv Br(CH₂)_nCOOR, 2 equiv DBU, DMF, microwave, 90 °C, 50−60 min, 51%; (b) conc HCl/dioxane (1:1, 20

mL/mmol), rt, 1−12 h, 50−80%; (c) Me₂NCSCl, K₂CO₃, NMP, 50 °C, 2 h, 90%; (d) NMP, microwave, 180 °C, 20 min, 72%; (e) (i) 4 equiv KOH,

CH₃OH, inert conditions, rt, 12 h, (ii) BrCH₂COOC(CH₃)_3,rt, 12 h, 86%; (f) H-Cube, H₂(40 bar, 25 °C), Pd/C (10%), CH₃OH, flow rate 1 mL/

min, 100%; (g) (i) pyridine, THF/H₂O (4:1), 0 °C, (ii) thiophene-2-sulfonyl chloride, 0 °C → rt, 4 h, 58%.

appropriate thioether moieties.³⁴Synthesis of the tetrazole-5-

thiol building block (Scheme 3, condition d) was carried out

from para-methoxybenzylisothiocyanate and sodium azide.

Deprotection of the para-methylbenzyltetrazole intermediate

was achieved with trifluoroacetic acid to synthesize the final

tetrazole-5-thiol building block (Caution!!! This reaction can be

explosive, isolation and drying large quantities of the thiotetrazole

building block should be avoided. Once prepared, the thio-tetrazole

building block should be stored in a solvent until further use). The

final step in the Scheme 3 involved in situ reduction of the

library 14 with thioether side chains (XR²= thioglycolic acid,

thiolactic acid, thiotetrazoles, thiotriazoles, thiomethyltetra-

zoles, thioaromatic groups, thioalkyl and thioamide side chains

[not reported here]) with high yields to afford the required

final library 15 with >95% purity by NMR and LCMS. The

purity of the most potent biologically active thioether analogues

was >95% as determined by HPLC (see Experimental Section).

Few of the intermediates of the library 14 leading to library 15

were characterized and confirmed by NMR, LCMS, and

formula guided mass spectroscopy. The library members 15

with thioether side chains appeared more stable at room

temperature compared to the compound bearing ether moiety

(i.e., 11b). The synthesis of the final library 15 with thioether

side chains via 14 using the key naphthoquinone intermediate

13 proved to be more convenient (3 steps), and we used this

optimized synthetic route to generate >170 compounds

(varying the sulfonamide moiety and the side chain) including

the original hit 1.

bromobutyrate were required to push the reactions. Acidic

hydrolysis of the intermediate esters 16a and 16b gave 17a and

17b, respectively, in good yields. The synthesis of the

intermediates 16a and 16b and the final compounds 17a

(one carbon side chain) and 17b (3-carbon side chain) were

confirmed by NMR, LCMS, and formula guided mass

spectroscopy.

Reaction of commercially available 4-nitronaphthol with

N,N-dimethylthiocarbamoyl chloride (Me₂NCSCl) produced

thiocarbamate 19 in good yield. A Newman−Kwart rearrange-

ment was employed to build the thioether scaffold

(intermediate 20 in Scheme 4, condition d) in the 1-position

of the naphthalene ring. Hydrolysis of N,N-dimethylthioamide

20 in KOH solution (1 M, 4 equiv) under inert conditions,

followed by alkylation with tert-butyl 2-bromoacetate, directly

gave the acid intermediate 21. Hydrogenation of the 4-nitro

group using an H-cube reactor (Scheme 4, condition f) gave

intermediate 22 in quantitative yield. The intermediate 22 was

used in the final step that involved sulfonamide formation with

thiophene-2-sulfonyl chloride and pyridine in an aqueous

solution to afford the desired compound thioether carboxylic

acid 23 in good yield. Formation of compound 23 was

confirmed by NMR, LCMS, and formula guided mass

spectroscopy and the purity of 23 was shown to be >95% as

determined by HPLC.

RESULTS AND DISCUSSION

■

The in-house synthesis (via both Schemes 2 and 3) of

compound 1 confirmed the structure and CT-L proteasome

inhibitory activity (IC₅₀= 3.0 1.6 μM [n = 25]), which in

turn allowed us to develop novel compounds with improved

activity and selectivity. In an effort to determine the important

moieties of the pharmacophore that are critical to its CT-L

inhibitory activity and to improve its in vitro and whole cell

activities, we have synthesized over 170 derivatives and

performed SAR studies using a fluorogenic assay as previously

described.^21,22In the initial screen, the % of CT-L inhibitory

activity was determined, and on the basis of these results a

dose−response (IC₅₀values) was obtained for compounds that

Moving the carboxylic acid side chain from the 2-position to

1-position of the naphthalene ring in compound 1 (Figure 1) is

outlined in the Scheme 4. Our aim was to synthesize a small

number of derivatives of the hit with O-substituted and S-

substituted carboxylic acid side chains at 1-position of the

naphthoquinone ring to probe interactions in the CT-L subunit

of the proteasome. First, compounds 16a and 16b were

obtained by directly alkylating the compound 3 (synthesis of 3

is shown in Scheme 1) with 2-bromoacetate or 4-

bromobutyrate using DBU (Scheme 4, condition a). Compound

3 was less reactive, and 15 equiv of 2-bromoacetate or 4-

1982

dx.doi.org/10.1021/jm201118h | J. Med. Chem. 2012, 55, 1978−1998

Journal of Medicinal Chemistry

Article

Table 1. SAR around the Side Chain S-R², Sulfonamide Moiety R¹of Compound 1

1983

dx.doi.org/10.1021/jm201118h | J. Med. Chem. 2012, 55, 1978−1998

Journal of Medicinal Chemistry

Article

Table 1. continued

1984

dx.doi.org/10.1021/jm201118h | J. Med. Chem. 2012, 55, 1978−1998

Journal of Medicinal Chemistry

Article

Table 1. continued

a

Each IC₅₀is at least the mean of 3 determinations. ND: IC₅₀not determined, these compounds showed less than 70% T-L inhibition at 10 μM.

displayed >70% inhibition at 10 μM. The compounds that

displayed potent CT-L inhibitory activity were also tested for in

vitro trypsin-like (T-L) inhibitory activity (Table 1).^21,22

In the hit-to-lead optimization chemistry, we first inves-

tigated in detail the importance of the thioglycolic acid side

chain while maintaining the thiophene sulfonamide moiety in

structure 1 (Figure 2A). Removal of the side chain from 1 as in

the 2-unsubstituted counterpart 3 (Scheme 1, IC₅₀> 30 μM)

was not tolerated, indicating that the thioglycolic acid side chain

is required for CT-L inhibitory activity. Hydronaphthoquinone

analogues bearing halogens Cl, Br, and I at the 2-position 4a,

4b, and 4c, respectively (Scheme 1), resulted in loss of CT-L

inhibitory activity (IC₅₀> 30 μM), further confirming the

importance of the thioglycolic acid side chain. Furthermore,

direct replacement of “sulfur” by “oxygen” (ether side chain,

11b in Scheme 2) or “sulfone” (11e in Scheme 2) was also

detrimental to CT-L inhibitory activity (IC₅₀> 100 μM),

indicating that the thio-ether moiety in compound 1 is

important. The replacement of the thioglycolic acid with

groups, such as S-ethyl, O-ethyl, S-ethanol, thio-N,N-

dimethylpropionamide (S(CH₂)₂CO-N-Me₂), and thio-N-

methylpropionamide (S(CH₂)₂CO-NH-CH₃), showed weaker

CT-L proteasome activity (IC₅₀> 5 μM, compounds not

reported here), suggesting that the carboxylic acid moiety was

essential for proteasome activity. The compound 10a (Scheme

2) with ethyl ester was shown to be less potent (IC₅₀> 10 μM)

than the corresponding acid, further confirming the importance

of the H-bond donor/acceptor features of the carboxylic group

for CT-L activity. The length of the side chain is also important,

as demonstrated by the 2-fold decreased potency in the

extended thioether carboxylic acid side chain as in 11d

(Scheme 2, IC₅₀= 5.7 μM). The position of the thioglycolic

acid side chain is critical, as demonstrated by the loss of CT-L

inhibitory activity (IC₅₀>100 uM) in compound 23 (Scheme

4), where the thioglycolic acid side chain was moved from the 2

to the 1-position. Our attempts to substitute the thioglycolic

acid chain of 1 with amines (not reported here) were not

successful due to oxidized impurities formed in the final

products. Finally, the naphthoquinone analogues of library 14

(Scheme 3) showed 2−3-fold weaker activity compared to the

corresponding active analogues of hydronaphthoquinone

library 15, indicating that the H-bond donor properties of the

hydronaphthoquinone may be important for binding inter-

actions with the β5 subunit of the protein. The SAR studies

described above demonstrate that the thioglycolic acid side

chain is required for the CT-L inhibitory activity of compound

1 and that the carboxylic acid moiety in this side chain is

critical. Subsequently, our chemistry efforts for side chain

modifications were focused on substituting the carboxylic acid

moiety with carboxylic acid isosteres such as tetrazoles or

triazoles with a thioether moiety. By incorporating the tetrazole

or triazole moieties, we were aiming to improve the potency,

solubility, and cell permeability of this class of compounds.

Replacement of the carboxylic acid moiety with tetrazole is

well-known and has increasingly been used with success in drug

discovery.³⁵Comparison of carboxylic acid and tetrazole groups

at physiological pH reveals that tetrazole group is almost 10

times more lipophilic while having similar acidity, pK_a= 4.9, to

that observed for carboxylic acids (pK_a= 4.2−4.4).³⁶

The replacement of the thioglycoloic acid side chain in

structure 1 (Figure 1) with thio-tetrazole (compound 15d in

Scheme 3) showed improved CT-L inhibitory activity (IC₅₀

=

1985

dx.doi.org/10.1021/jm201118h | J. Med. Chem. 2012, 55, 1978−1998

Journal of Medicinal Chemistry

0.51 0.12 μM, Table 1). Furthermore, replacement of the

Article

thioglycoloic acid side chain with thio-methyltetrazole (15b,

Scheme 3), thio-triazole (15c, Scheme 3), and thiobenzoic acid

(24, Table 1) resulted in retention of the CT-L proteasome

activity (IC₅₀= 4.2, 4.2, and 4, respectively, Table 1). We were

encouraged by these results, and our next generation of

compounds (Scheme 3) were synthesized with thio-tetrazole,

-triazole, or -methyl tetrazole to mimic the H-bond donor/

acceptor features of the carboxylic acid moiety in our original

hit. The compound 24 (Table 1) with thiobenzoic acid side

chain was not further pursued for library synthesis due to poor

solubility. In the next generation of analogues, we varied the

sulfonamide moiety while keeping the thio-tetrazole, -triazole,

or -methyltetrazole moieties as side chains at the 2-position of

the hydronaphthoquinone pharmacophore. Compounds with

thio-tetrazole and thio-triazole side chains containing biaryl

sulfonamide moieties (Table 1) displayed the best CT-L

activities. For example, compounds 15e, 15f, 15h, 15j, 15k, 27,

and 29 (Table 1) displayed up to 20-fold (IC₅₀values around

150−250 nM) improved CT-L inhibitory activity. These results

indicate that aromatic hydrophobic sulfonamide groups are

tolerated in the binding region. Interestingly, compounds

bearing 5-methyl-thio-tetrazole side chain with biaryl sulfona-

mide moieties (analogues of 15b in Table 1, not reported here)

failed to improve the CT-L activity indicating that the tetrazole

anion is contributing to potency (tetrazole is deprotonated at

pH 7 similar to a carboxylic acid group). Overall, compounds

with methyl-thiotetrazole side chain did not improve the CT-L

proteasome activity.

The stability of some of the potent hydronaphthoquinone

analogues (15f and 25, Table 1) with thioether side chain

(thioglycolic acid, thio-tetrazole, thio-triazole) including the

“hit” were examined by ¹H NMR in deuterated DMSO up to 3

weeks at room temperature. The HPLC and LCMS were also

determined under the assay conditions (in tris buffer at room

temperature). Our data concluded the hydronaphthoquinone

class of compounds showed >95% purity by LCMS, HPLC, and

¹H NMR and were stable at room temperature for up to two

weeks. Approximately 3−5% impurities (oxidized material)

were shown after 2 weeks. Further analysis of stability of the

compounds 1, 15k, and 39 was carried out using the two

biological media we used for our in vivo studies (Dulbecco’s

Modified Eagle Medium [DMEM] and Roswell Park Memorial

Institute-1640 [RPMI1640]) without serum. Stock solutions of

compounds 1, 15k, and 39 (1 mM solutions) were prepared

using DMSO, and 10 μL aliquot of the each of the stock

solution was diluted to 1 mL using the biological medium. The

final concentration of each of the samples was 10 μM with 1%

DMSO. These samples were left in an incubator at 37 °C and

analyzed by HPLC to determine the amount of respective

compound present in each sample vial at 1, 3, 5, and 7 day time

intervals. The HPLC results, peak area against time were

plotted as shown in the Figure 3, which shows the peak area of

each of the compounds in either DMEM or RPMI, did not

significantly change or deviate with the time. From these data

we concluded compounds 1, 15k, and 39 were stable up to 7

days at 37 °C in the biological media we used.

Figure 3. Stability assessment of compounds 1, 15k, and 39 in

biological medium (DMEM and RPMI-1640) up to 7 days.

of the proteasome. The most potent and selective CT-L activity

(28-fold, in vitro) was displayed by compound 29 (Table 1).

Interestingly, compounds 35 and 36 were equipotent against

CT-L and T-L activities while compound 15d was more

selective for T-L over CT-L.

Our initial goal was to identify compounds that were more

potent in the primary in vitro assay as well as the cell culture

assay. Our in vitro study showed several tetrazole containing

analogues to be more potent than the initial hit (Table 1). We,

therefore, determined whether some of these compounds were

cell permeable and could inhibit the CT-L activity of the

proteasome in intact cells. Treatment of the human breast

cancer cell lines MDA-MB-468 and MDA-MB-231 with various

doses of 1 for 48 h resulted in inhibition of the CT-L activity in

these cells with an IC₅₀value of 7.22 and 3.54 μM, respectively.

Out of several compounds tested for intact cell CT-L inhibitory

activity in MDA-MB-468 and MDA-MB-231 cells, we identified

39 that potently inhibited CT-L activity with IC₅₀values of 1.01

and 0.44 μM, respectively. To determine if the most potent

compound 39 could inhibit CT-L activity at earlier time points,

and if this results in the accumulation of ubiquitinated cellular

proteins, we treated MDA-MB-468 cells with various

concentrations of 39 for 11 h and processed the cells for

CT-L assays and Western blotting as described in Experimental

Section. After 11 h of treatment, 39 inhibited CT-L activity in

MDA-MB-468 cells with an IC₅₀value of 15.6 μM (Figure 4A).

Figure 4B shows that treatment of MDA-MB-468 cells with 39

resulted in a concentration-dependent increase in ubiquitina-

tion. Finally, to determine the effects of 39 on MDA-MB-468

tumor cell proliferation, we treated the cells as described above

and analyzed cell proliferation by MTT assay after 11 h. Figure

4C shows that 39 inhibited tumor cell proliferation with an IC₅₀

value of 17.0 μM.

To investigate whether compound 1- and 39-mediated

proteasome inhibition is reversible or irreversible; we

performed a dialysis experiment with compounds 1, 39, and

Bortezomib, a covalent slowly reversible proteasome inhibitor

that was used as an internal control. Figure 5 shows that in the

absence of dialysis, 1, 39, and Bortezomib were able to inhibit

the CT-L activity of the 20S proteasome by 68%, 73%, and

87%, respectively. During dialysis, the CT-L activity did not

show any recovery in the compounds 1 and 39 treated samples.

By contrast, in the Bortezomib treated samples, CT-L activity

recovery started within 4 h. These results suggest that both

compounds 1 and 39 behave differently than Bortezomib. It is

likely that both 1 and 39 behave as irreversible CT-L

proteasome inhibitors.

One of the important aims in this study was to obtain a

compound highly selective for CT-L activity. Therefore, we

next determined if those compounds that are potent

proteasome inhibitors are selective for CT-L over the T-L

activity of the proteasome. Table 1 shows that most

compounds were more selective for CT-L over T-L activity

1986

dx.doi.org/10.1021/jm201118h | J. Med. Chem. 2012, 55, 1978−1998

Journal of Medicinal Chemistry

Article

Figure 4. Effects of compound 39 on proteasomal CT-L activity, ubiquitination, and tumor cell viability in human breast cancer MDA-MB-468 cells.

Exponentially growing human breast cancer cells were treated with different concentrations of compound 39 for 11 h, followed by measurement of

CT-L activity in whole cell extracts (A), determination of ubiquitination by Western blot analysis (B), and cell viability as measured by MTT assay

(C).

1

uncorrected. H NMR spectra were recorded on a Varian Mercury

400 MHz spectrometer with CD₂Cl₂, CDCl₃, CD₃CN, or DMSO-d₆as

the solvent. ¹³C NMR spectra are recorded at 100 MHz. All coupling

constants are measured in hertz (Hz), and the chemical shifts (δ_Hand

δ_C) are quoted in parts per million (ppm) relative to TMS (δ 0),

which was used as the internal standard. The definition apparent is

used as app to describe ¹H NMR signals. Liquid chromatography mass

spectroscopy (LCMS) and high resolution mass spectroscopy

(HRMS) were carried out on an Agilent 6210 LC/MS (ESI-TOF).

For LCMS and HRMS, the compounds were eluted between 2 and 5

min using Rapid Resolution Cartridge (2.1 mm × 30 mm, particle size

3.5 μm) from Agilent Technologies. LCMS was used to detect ions of

mass 100−1000 Da, and single peak was observed in the chromato-

gram after purification. HPLC was carried out using Jasco UV-2075

Figure 5. Recovery of CT-L activity upon dialysis of the 20S

plus UV−vis detector (column: ultra C18, 5 μm, 150 mm × 4.6 mm).

H-Cube (ThalesNano) continuous-flow hydrogenation reactor was

used for hydrogenation reactions. Microwave reactions were

performed in CEM Discover 908005 model and Biotage initiator 8

machines. Thin layer chromatography was performed using silica gel

60 F254 plates (Fisher), with observation under UV when necessary.

Anhydrous solvents were used as purchased: dichloromethane (DCM)

(anhydrous, 99.8% contains 50−150 ppm hydrocarbon as stabilizer

from Aldrich), dimethyl formamide (DMF) (anhydrous, 99.9% from

Aldrich), tetrahydrofuran (THF) (anhydrous, 99.9%, inhibitor free,

Aldrich), acetonitrile (anhydrous, 99.8%, Aldrich), toluene (anhy-

drous, 99.8%, Aldrich), methanol (MeOH) (anhydrous, 99.8%,

Aldrich), and ethanol (EtOH) (absolute, 99.5%, Aldrich). N-Methyl-

2-pyrolidinone was purchased from Acros (99%) and used as a solvent.

All biologically characterized compounds were >95% pure as

determined by HPLC and LCMS except 4b, 10a, 10c, 11b, 11c,

15b, 15c, 15e, 15i, 24, and 37 that showed purity between 89 and 94%

by HPLC. All biologically characterized compounds were analyzed by

¹H NMR, ¹³C NMR, and HRMS (formula guided mass spectroscopy).

proteasome−compound complexes after preincubation with Bortezo-

■

▲

●

mib ( ), compound 39 ( ), and compound 1 ( ).

CONCLUSIONS

■

In this report, we describe the design and synthesis of novel

class of compounds as proteasome inhibitors. The hit 1 was

identified from screening of an in-house ChemDiv 20000

compound library. The synthetic route to 1-hydroxy-4-

thiophenesulfonamido naphthalene-2-thioacetic acid (1) class

of compounds was established, and analogues of 1 were shown

to be potent inhibitors of CT-L activity of protesome both in

vitro and in vivo. The SAR-guided lead optimization showed

that incorporation of the tetrazole moiety, a carboxylic acid

isostere and triazole at the 2-position of the hydronaphthoqui-

none moieties was crucial to achieving improved potency. The

most potent compounds 25, 27, 29, 15e, 15f, 15h, 15j, and 15k

(Table 1) with IC₅₀values 150−300 nM were obtained with

hydrophobic sulfonamide moieties. Compounds 1 and 39 (that

showed improved whole cell activity) were further tested to

understand the binding mode with the proteasome. It was

concluded that compounds that contain 1-hydroxy-4-thiophe-

nesulfonamidonaphthalene scaffold with 2-thoacetic acid or

thio-tetrazole moieties as side chains are irreversible protea-

some inhibitors. Furthermore, compound 39 was much more

potent than 1 at inhibiting CT-L activity in intact human breast

cancer cells. Compound 39 also induced the accumulation of

ubiquitinated cellular proteins and inhibited breast tumor cell

proliferation.

Most of the intermediates of the library 14 were not isolated because

the reaction produced a mixture of naphthoquinone sulfonimides (14)

and hydronathoquinone sulfonamides (15). This mixture was treated

with Na₂S₂O₄to get the final library 15 with high purity. However, the

14a, 14b, and 14c were isolated and reported here.

Analysis of Stability of Compounds 1, 15, and 39 Using

HPLC. Using fresh powder, 1 mM stock solutions were made (in

DMSO) for each compound 1, 15k, and 39. Then a 10 μL aliquot

from each stock solution was taken and diluted to 1 mL with biological

media (DMEM and RMPI). We prepared five replicates per sample

per media, and the final concentration of each solution was 10 μM

with 1% DMSO. These sample solutions were incubated at 37 °C for

1, 3, 5, and 7 days, respectively. The vials containing the sample

solution were taken out from the incubator at day-1, day-3, day-5, and

day-7 and cooled to 0 °C in an ice bath. The sample solutions were

analyzed immediately with HPLC. Peak areas were plotted against

time (day). HPLC conditions: Agilent Eclipse XDB-C18, 5 μm, 4.6

mm × 150 mm, 35% CH₃CN, 65% H₂O (with 0.1% TFA), 1 mL/min,

EXPERIMENTAL SECTION

All reagents were purchased from commercial suppliers and used

without further purification. Melting points were determined using a

Barnstead international melting point apparatus and remain

■

1987

dx.doi.org/10.1021/jm201118h | J. Med. Chem. 2012, 55, 1978−1998

Journal of Medicinal Chemistry

Article

30 min for compound 1; 50% CH₃CN, 50% H₂O (with 0.1% TFA), 1

mL/min, 30 min for compounds 15k and 39.

MeOH (10 mL), hydrogen peroxide added (35% in water, 3 mL), and

stirred at rt for 2 h. Additional hydrogen peroxide (3 mL) was added,

followed by HCl (4 M in dioxane, 1 mL) and continued stirring at rt

for another 2 h. The organic phase was evaporated, and the residue

was dissolved in ethyl acetate (100 mL) and washed with water (20

mL × 3) and brine (20 mL × 2). The organic phase was dried

(Mg₂SO₄), filtered, and concentrated to obtain a crude solid. The

crude solid was purified using SiO₂chromatography (hexane/EtOAc

gradient elution) to obtain pure compound 4a (244 mg, 22.2%) as a

brown solid. R_f= 0.46 (TLC, EtOAc/hexane [1:2]); mp 113−115 °C.

HPLC 98% (R_t= 6.79 min, 60% CH₃CN in 0.1% TFA water, 20 min).

¹H NMR (400 MHz, CDCl₃) δ 7.79 (d, J = 8.4 Hz, 1H), 7.69 (d, J =

8.4 Hz, 1H), 7.64 (dd, J = 4.8, 1.1 Hz, 1H), 7.60 (dd, J = 4.0, 1.2 Hz,

1H), 7.44−7.35 (m, 2H), 7.19 (s, 1H), 7.02 (dd, J = 5.2, 4.0, Hz, 1H),

4.46 (br s, 2H). ¹³C NMR (100 MHz, CDCl₃) δ 138.07, 137.40,

135.81, 134.98, 134.78, 127.84, 126.96, 126.92, 126.82, 123.74, 122.44,

121.08, 120.54, 111.99. LC-MS (ESI+) 339.98 (M + H)⁺. HRMS (ESI

+) m/z calculated for C₁₄H₁₁ClO₃S₂(M + H)⁺339.9863, found

339.9856.

N-(3-Bromo-4-hydroxynaphthalen-1-yl)thiophene-2-sulfona-

mide (4b). The compound 3 (306 mg, 1 mmol) was dissolved in DMF

(1 mL) at 0 °C, and Br₂(320 mg in 1 mL of DCM solution, 2 mmol)

was added and stirred at rt for 1 h. Triethylamine (0.558 mL, 4 mmol)

was added at 0 °C and continued stirring at rt overnight (12−14 h).

The reaction mixture was diluted with ethyl acetate (50 mL), washed

with water (10 mL) and brine (10 mL), dried (Na₂SO4), and

concentrated to obtain a brown crude solid. The crude product was

purified using SiO₂chromatography (hexane/EtOAc gradient elution)

to obtain 4b (140 mg, 36.4%) as an orange−red solid. R_f= 0.38 (TLC,

EtOAc/hexane [1:2]); mp 128−130 °C. HPLC 88% (R_t= 7.33 min,

60% CH₃CN in 0.1% TFA water 20 min). ¹H NMR (400 MHz,

CDCl₃) δ 7.80 (d, J = 7.6 Hz, 1H), 7.70 (d, J = 7.6 Hz, 1H), 7.66

(appdd, J = 4.8, 1.2 Hz, 1H), 7.61 (appdd, J = 4.0, 1.2 Hz, 1H), 7.47−

7.39 (m, 2H), 7.32 (s, 1H), 7.04 (dd, J = 4.8, 3.6 Hz, 1H), 4.75 (br s,

2H). LC-MS (ESI+) 383.93 (M + H)⁺. HRMS (ESI+) m/z calculated

for C₁₄H₁₁BrO₃S₂(M + H)⁺383.9358, found 383.9348.

N-(3-Iodo-4-hydroxynaphthalen-1-yl)thiophene-2-sulfonamide

(4c). This compound was prepared using the procedure described for

compound 4b, except using I₂(152 mg, 0.6 mmol). The pure product

4c (129.4 mg, 100%) was obtained as a brown solid. R_f= 0.45 (TLC,

EtOAc/hexane [1:2]); mp 134−136 °C. HPLC 97% (R_t= 8.19 min,

60% CH₃CN in 0.1% TFA water 20 min). ¹H NMR (400 MHz,

CDCl₃) δ 7.83−7.81 (m, 1H), 7.75−7.72 (m, 1H), 7.68 (dd, J = 4.8,

1.2 Hz, 1H), 7.62 (dd, J = 4.0, 1.2 Hz, 1H), 7.46−7.41 (m, 3H), 7.06

(dd, J = 5.0, 3.8 Hz, 1H), 4.7 (br s, 1H). ¹³C NMR (100 MHz, CDCl₃)

δ 142.59, 137.62, 135.83, 134.95, 134.82, 128.37, 127.89, 127.83,

127.28, 126.82, 122.64, 122.62, 121.56, 75.24. LC-MS (ESI+) 431.92

(M + H)⁺. HRMS (ESI+) m/z calculated for C₁₄H₁₁IO₃S₂(M + H)⁺

431.9220, found 431.9216.

Ethyl 2-(1,4-Dioxo-1,4-dihydronaphthalen-2-ylthio)acetate (8a).

The 1,4-naphthoquinone (791 mg, 5 mmol) was added portionwise to

EtOH (10 mL) containing ethyl mercaptoacetate (0.27 mL, 25 mmol)

at room temperature. The reaction mixture was stirred at room

temperature for 30 min. The yellow solid obtained was filtered, washed

with ethanol, and dried under vacuum to obtain naphthoquinone

intermediate 8a (491 mg, 88.9%) as a yellow solid. R_f= 0.60 (TLC,

EtOAc/hexane = 1:2); mp 150−152 °C. ¹H NMR (400 MHz, CDCl₃)

δ 8.11−8.07 (m, J = 7.4 Hz, 2H), 7.78−7.69 (m, 2H), 6.70 (s, 1H),

4.24 (q, J = 7.1 Hz, 2H), 3.66 (s, 2H), 1.31 (t, J = 7.1 Hz, 3H). ¹³C

NMR (100 MHz, CDCl₃) δ 182.15, 181.73, 167.68, 153.42, 134.69,

133.67, 132.27, 131.88, 128.12, 127.08, 126.84, 62.60, 33.14, 14.33.

LC-MS (ESI+) 299.01 (M + Na)⁺. HRMS (ESI+) m/z calculated for

C₁₄H₁₃O₄S (M + H)⁺277.0529, found 277.0529.

Methyl 3-(1,4-Dioxo-1,4-dihydronaphthalen-2-ylthio)-

propanoate (8b). This compound was prepared using the procedure

described for compound 8a except using methyl 3-mercaptopropio-

nate (1.582 g, 0.01 mol). The pure product 8b (1.298 g, 93.9%) was

obtained as a yellow solid. R_f= 0.40 (TLC, EtOAc/hexane [1:2]); mp

108−110 °C. ¹H NMR (400 MHz, CDCl₃) δ 8.09 (t, J = 7.6 Hz, 2H),

7.76 (td, J = 7.6, 1.6 Hz, 1H), 7.71 (td, J = 7.6, 1.2 Hz, 1H), 6.64 (s,

Cell Culture and Cell Lysate Preparation and Determination

of Proteolytic Activity in Cell Lysates. Human MDA-MB-468

breast cancer cells were cultured in DMEM medium containing 10%

fetal calf serum (FCS) and 100 units/mL of penicillin and 100 μg/mL

of streptomycin. Cells were maintained at 37 °C in a humidified

incubator in an atmosphere of 5% CO₂. Cells were treated with

different concentrations of compounds 1, 39, or vehicle control

(DMSO) for 48 or 11 h. Cells were then harvested, washed with PBS

twice, and homogenized in lysis buffer (50 mM Tris-HCl, pH = 8.0, 5

mM EDTA, 150 mM NaCl, 0.5% NP-40) for 30 min at 4 °C. Cell

lysates were centrifuged at 12000g for 15 min, and the supernatants

were collected as cell lysates. To determine the proteasome CT-L

activity in whole cell extracts from cultured cells, we used the same

method^21,22described for in vitro CT-L activity assay, except instead

of using 20S rabbit proteasome, we used 5 μg of cell lysates.

Western Blot Analysis. Cell lysates (30 μg) were separated by

SDS-PAGE and transferred to a nitrocellulose membrane, probed with

ubiquitin antibody (Santa Cruz Biotechnnology Inc. (Santa Cruz, CA),

and signals were visualized by enhanced chemoluminescence (ECL,

Amersham, Piscataway, NJ) according to the manufacturer’s protocol.

MTT (3-(4,5-Dimethythiazol-2-yl)-2,5-diphenyltetrazolium

bromide) Metabolism Assay. Cells were plated in 96-well plates

in 100 μL medium and allowed to attach overnight. Cells were then

incubated for 11 h with varying concentrations of compound 39 and

appropriate control. Media was aspirated and replaced with 100 μL of

complete media containing 1 mg/mL MTT and incubated for 3 h at

37 °C in 5% CO₂humidified incubator. Media was then aspirated, and

DMSO was added. Cells were incubated for 10 min at room

temperature while shaking, and the absorbance was determined at 540

nm using a μQuant spectrophotometric plate reader (Bio-TEK,

Winooski, VT).

Dialysis Using Purified Rabbit 20S Proteasome. To measure

the effect of dialysis on CT-L activity, compounds 1, 39, Bortezomib

(10 μM), or vehicle (0.1% DMSO) were added to rabbit 20S

proteasome at a final concentration of 1.5 nM in proteasome assay

buffer (50 mM Tris-HCl, pH = 7.6) and incubated at room

temperature for 30 min. After 30 min of incubation, proteasome−

compound mixtures were added to 3500 MWCO Thermo Scientific

Slide-A-Lyzer MINI Dialysis Unit (Rockford, IL) and dialyzed against

proteasome assay buffer. Immediately (t = 0) and 0.5 h, 1 h, 4 h, 8 h,

and 18 h of dialysis at 4 °C, samples were removed from the dialysis

unit and the CT-L 20S proteasome activity was determined as

described previously.^21,22Proteasome activity was normalized against

proteasome activity of DMSO control.

N-(4-Hydroxynaphthalen-1-yl)thiophene-2-sulfonamide (3). The

4-aminonaphthol hydrochloride salt (2) (1.957 g, 0.01 mol) was

suspended in DCM (80 mL) and added triethylamine (3.0 mL, 22

mmol) at 0 °C (the suspension became a dark brown solution).

Thiophene-2-sulfonyl chloride (1.827 g, 0.01 mol) was added, and the

reaction mixture was stirred at rt overnight (14 h). The reaction

mixture was diluted with DCM (200 mL) washed with aqueous HCl

(1 N, 30 mL × 3), water (30 mL × 3), and brine (30 mL). The

organic layer was separated, dried (MgSO₄), and concentrated to

obtain a dark-brown solid. The crude solid was suspended in

methanol/water (1:1, ∼50 mL), filtered, and washed with

methanol/H₂O (1:1, ∼15 mL × 2) to obtain pure compound 3 (2.7

g, 90%) as a brown solid; R_f= 0.23 (TLC, EtOAc/hexane [1:2]); mp

146−148 °C. HPLC 96% (R_t= 3.51 min, 60% CH₃CN in 0.1% TFA

1

water, 20 min). H NMR (400 MHz, CD₂Cl₂) δ 7.83−1.78 (m, 2H),

7.70 (dd, J = 5.8, 1.2 Hz, 1H), 7.60 (dd, J = 3.6, 1.2 Hz, 1H), 7.49−

7.42 (m, 2H), 7.07 (d, J = 8.0 Hz, 1H), 7.06 (dd, J = 5.2, 4.0 Hz 1H),

6.66 (d, J = 8.4 Hz, 1H), 4.30 (br s, 2H, disappeared on D₂O shake).

¹³C NMR (100 MHz, CDCl₃) δ 141.83, 138.30, 135.52, 135.19,

134.61, 128.06, 127.69, 126.93, 125.81, 124.11, 122.19, 121.18, 119.63,

108.26. LC-MS (ESI+) 306.03 (M + H)⁺. HRMS (ESI+) m/z

calculated for C₁₄H₁₂NO₃S₂(M + H)⁺306.0253, found 306.0266.

N-(3-Chloro-4-hydroxynaphthalen-1-yl)thiophene-2-sulfona-

mide (4a). The compound 3 (987 mg, 3.2 mmol) was suspended in

1988

dx.doi.org/10.1021/jm201118h | J. Med. Chem. 2012, 55, 1978−1998

Journal of Medicinal Chemistry

Article

1H), 3.74 (s, 3H), 3.13 (t, J = 7.4 Hz, 2H), 2.78 (t, J = 7.3 Hz, 2H).

¹³C NMR (100 MHz, CDCl₃) δ 182.16, 181.66, 171.43, 154.29,

134.63, 133.59, 132.31, 132.02, 127.36, 127.10, 126.81, 52.42, 32.29,

25.46. LC-MS (ESI+) 299.04 (M + Na)⁺, 277.05 (M + H)⁺. HRMS

(ESI+) m/z calculated for C₁₄H₁₃O₄S (M + H)⁺277.0529, found

277.0539.

Hz, 3H). ¹³C NMR (100 MHz, CDCl₃) δ 180.89, 167.41, 160.31,

152.98, 141.25, 134.32, 133.74, 133.45, 133.37, 131.78, 129.26, 127.49,

127.46, 127.09, 121.29, 62.94, 33.56, 14.30. LC-MS (ESI+) 416.06 (M

+ H)⁺. HRMS (ESI+) m/z calculated for C₂₀H₁₈NO₅S₂(M + H)⁺

416.0621, found 416.0621.

Methyl 3-(1-Oxo-4-(thiophen-2-ylsulfonylimino)-1,4-dihydro-

naphthalen-2-ylthio) propanoate (9d). This compound was

prepared according to the procedure described for compound 9a

except using 8b (276 mg, 1 mmol). The title compound 9d (110 mg,

26.1%) was obtained as an orange color solid. R_f= 0.50 (TLC, EtOAc/

hexane [1:2]); mp 140−142 °C. HPLC 99% (R_t= 4.47 min, 70%

tert-Butyl 2-(1,4-Dioxo-1,4-dihydronaphthalen-2-yloxy)acetate

(8c). A mixture of 2-hydroxynaphthalene-1,4-dione 6 (174.2 mg, 1.0

mmol), tert-butyl 2-bromoacetate (0.2 mL, 1.33 mmol), silver oxide

(308 mg, 1.33 mmol), and potassium iodide (16.6 mg, 0.1 mmol) in

chloroform (5 mL) was refluxed under argon atmosphere for 12 h.

Additional tert-butyl 2-bromoacetate (1.5 mL, 10 mmol) was added,

and the reaction was continued under reflux for further 24 h. The

reaction mixture was filtered through a pad of Celite, washed with

DCM (3 × 10 mL), and the filtrate was concentrated to obtain a

gray−yellow solid. The crude product was purified using SiO₂

chromatography (5 g silica gel, EtOAc/hexane gradient elution) to

give pure compound 8c (93.2 mg, 32%) as a light-yellow solid. R_f=

1

CH₃CN in 0.1% TFA water 20 min). H NMR (400 MHz, CDCl₃) δ

8.24−8.22 (m, 1H), 8.15−8.13 (m, 1H), 7.91 (s, 1H), 7.83−7.82 (m,

1H), 7.71−7.68 (m, 3H), 7.16−7.14 (m, 1H), 3.75 (s, 3H), 3.26 (t, J =

6.9 Hz, 2H), 2.85 (t, J = 6.9 Hz, 2H). ¹³C NMR (100 MHz, CDCl₃) δ

180.79, 171.35, 160.09, 154.37, 142.10, 134.39, 133.63, 133.53, 133.23,

132.95, 131.99, 127.59, 127.57, 127.23, 120.19, 52.46, 32.07, 25.88.

LC-MS (ESI+) 422.03 (M + H)⁺. HRMS (ESI+) m/z calculated for

C₁₈H₁₆NO₅S₃(M + H)⁺422.0185, found 422.0181.

1

0.50 (TLC, EtOAc/hexane [1:2]); mp 120−122 °C. H NMR (400

Ethyl 2-(1-Hydroxy-4-(thiophene-2-sulfonamido)naphthalen-2-

ylthio)acetate (10a). The (E)-ethyl 2-(1-oxo-4-(thiophen-2-ylsulfo-

nylimino)-1,4-dihydronaphthalen-2-ylthio)acetate (9a) (52 mg, 0.123

mmol) was dissolved in THF (2 mL), and Na₂S₂O₄(107 mg, 0.62

mmol in 2 mL of water) was added. The biphasic mixture obtained

was stirred at rt for 1 h until it turned pale yellow. The mixture was

diluted with ethyl acetate (∼30 mL) and washed with water (∼10 mL)

and brine (∼10 mL). The organic phase was dried (Na₂SO₄) and

filtered, and the filtrate was concentrated. The crude product obtained

was purified (SiO₂chromatography, EtOAc/hexane gradient elution)

to obtain pure 10a (0.025 g, 58.7%) as an off-white solid. R_f= 0.25

(TLC, EtOAc/hexane [1:2]); mp 116−118 °C. HPLC 93% (R_t= 4.72

MHz, CDCl₃) δ 8.15 (m, 1H), 8.08 (m, 1H), 7.77−7.71 (m, 2H), 6.04

(s, 1H), 4,61 (s, 2H), 1.41 (s, 9H). LC-MS (ESI+) 233.03 (M +

H-^tBu)⁺, 289.10 (M + H)⁺. HRMS (ESI+) m/z calculated for

C₁₆H₁₇O₅(M + H)⁺289.1071, found 289.1090.

Ethyl 2-(1-Oxo-4-(thiophen-2-ylsulfonylimino)-1,4-dihydronaph-

thalen-2-ylthio)acetate (9a). To a mixture of 8a (63 mg, 0.228

mmol) and thiophene-2-sulfonamide (37 mg, 0.228 mmol) in DCM

(2.5 mL) at 0 °C was added TiCl₄·2THF complex (76 mg, 0.228

mmol) followed by triethylamine (70 μL, 0.5 mmol). The mixture was

heated at 60 °C using the microwave reactor for 20 min. The reaction

mixture was diluted with DCM (60 mL) and washed with water (∼15

mL) and brine (∼15 mL). The organic phase was separated, dried

(Na₂SO₄), and concentrated to obtain a brown crude semisolid. The

crude mixture was purified using SiO₂chromatography (EtOAc/

hexane gradient elution) to obtain the required pure compound 9a (58

mg, 60%) as an orange oil which solidified on standing at room

temperature. R_f= 0.30 (TLC, EtOAc/hexane [1:2]); mp 110−112 °C.

HPLC 95% (R_t= 4.63 min, 70% CH₃CN in 0.1% TFA water, 20 min).

¹H NMR (400 MHz, CDCl₃) δ 8.22 (dd, J = 6.0, 3.2 Hz, 1H), 8.15

(dd, J = 5.6, 3.2 Hz, 1H), 7.96 (s, 1H), 7.83 (dd, J = 4.0, 1.6 Hz, 1H),

7.71−7.68 (m, 3H), 7.15 (dd, J = 5.0, 4.0 Hz, 1H), 4.31 (q, J = 7.2 Hz,

2H), 3.80 (s, 2H), 1.35 (t, J = 7.2 Hz, 3H). ¹³C NMR (100 MHz,

CDCl₃) δ 180.80, 167.34, 160.01, 153.40, 142.08, 134.42, 133.61,

133.59, 133.27, 133.00, 131.81, 127.56, 127.23, 120.91, 62.95, 33.56,

14.29. LC-MS (ESI+) 422.03 (M + H)⁺. HRMS (ESI+) m/z

calculated for C₁₈H₁₆NO₅S₃(M + H)⁺422.0185, found 422.0192.

tert-Butyl-2-(1-oxo-4-(thiophen-2-ylsulfonylimino)-1,4-dihydro-

naphthalen-2-yloxy)acetate (9b). Triethylamine (0.12 mL, 0.88

mmol) was added to a mixture of tert-butyl 2-(1,4-dioxo-1,4-

dihydronaphthalen-2-yloxy)acetate 8c (115 mg, 0.4 mmol) and

thiophene-2-sulfonamide (78 mg, 0.48 mmol) in anhydrous DCM

(4 mL). TiCl₄·2THF (134 mg, 0.4 mmol) was added to the reaction

mixture and heated at 60 °C using the microwave reactor for 20 min.

The crude mixture was poured into EtOAC (20 mL), filtered using a

Celite pad, and the filtrate was concentrated and purified (SiO₂

chromatography, EtOAc/hexane gradient elution) to give pure

compound 9b (0.068 g, 39%) as a yellow solid; mp 153−155 °C.

HPLC 94% (R_t= 4.86 min, 70% CH₃CN in 0.1% TFA water 20 min).

¹H NMR (400 MHz, CDCl₃) δ 8.08−8.06 (m, 1H), 8.02−8.00 (m,

1

min, 60% CH₃CN in 0.1% TFA water 20 min). H NMR (400 MHz,

CDCl₃) δ 8.42 (s, 1H), 8.29 (dd, J = 6.3, 3.2 Hz, 1H), 7.80 (dd, J =

6.3, 3.1 Hz, 1H), 7.52 (d, J = 4.0 Hz, 1H), 7.48 (dd, J = 6.4, 3.2 Hz,

2H), 7.38 (d, J = 2.4 Hz, 1H), 7.34 (s, 1H), 6.95 (t, J = 4.8 Hz, 1H),

6.7 (br s, 1H), 4.18 (q, J = 7.1 Hz, 2H), 3.48 (s, 2H), 1.21 (t, J = 7.1

Hz, 3H). ¹³C NMR (100 MHz, CDCl₃) δ 171.46, 155.83, 139.71,

133.32, 132.69, 131.87, 128.70, 127.59, 126.46, 124.78, 124.05, 123.41,

122.18, 110.19, 62.75, 39.73, 14.24. LC-MS (ESI+) 441.05 (M +

NH₄)⁺. HRMS (ESI+) m/z calculated for C₁₈H₁₈NO₅S₃(M + H)⁺

424.0342, found 424.0335.

tert-Butyl-2-(1-hydroxy-4-(thiophene-2-sulfonamido)-

naphthalen-2-yloxy)acetate (10b). The tert-butyl-2-(1-oxo-4-(thio-

phen-2-ylsulfonylimino)-1,4-dihydronaphthalen-2-yloxy)acetate 9b

(70 mg, 0.16 mmol) was dissolved in THF (3 mL) and stirred at rt

for 5 min. The Na₂S₂O₄(139 mg, 0.8 mmol) and water (1 mL) was

added to the mixture and stirred vigorously until Na₂S₂O₄was

completely dissolved. The reaction mixture was further stirred at rt for

10 min. The color changed from orange to light yellow. EtOAc (40

mL) was added into the mixture and washed with water (40 mL)

followed by brine. The organic phase was dried (MgSO₄) and filtered,

and the filtrate was concentrated. The required product 10b was

obtained by crystallization with EtOAc/hexane as a light-yellow solid

(50 mg, 71%); mp = 155−157 °C. HPLC 96% (R_t= 3.39 min, 70%

1

CH₃CN in 0.1% TFA water 20 min). H NMR (400 MHz, CDCl₃) δ

8.52 (br s, 1H, disappeared on D₂O shake), 8.24 (d, J = 8.4 Hz, 1H),

7.54 (d, J = 8.0 Hz, 1H), 7.46 (dd, J = 4.8, 1.3 Hz, 1H), 7.44−7.40 (m,

1H), 7.35−7.29 (m, 2H), 7.23 (s, 1H), 6.90 (dd, J = 5.2, 4.0 Hz, 1H),

6.68 (s, 1H, disappeared on D₂O shake), 4.53 (s, 2H), 1.50 (s, 9H).

¹³C NMR (100 MHz, CDCl₃) δ 171.34, 143.83, 140.29, 139.79,

133.09, 132.62, 127.98, 127.54, 126.44, 125.97, 125.64, 123.13, 122.78,

121.04, 119.32, 84.20, 71.12, 28.29. LC-MS (ESI−) 434.07 (M − H)⁻.

HRMS (ESI−) m/z calculated for C₂₀H₂₀NO₆S₂(M − H)⁻434.0738,

found 434.0755.

Ethyl 2-(1-Hydroxy-4-(phenylsulfonamido)naphthalen-2-ylthio)-

acetate (10c). This compound was prepared using the procedure

described for 10a except using the starting material 9c (83 mg, 0.2

mmol). The title compound 10c was obtained as a pale-yellow solid

(68 mg, 81.5%). R_f= 0.22 (TLC, EtOAc/hexane [1:2]); mp 118−120

°C. HPLC 92% (R_t= 5.04 min, 60% CH₃CN in 0.1% TFA water 20

1H), 7.64 (appdd, J = 3.7, 1.2 Hz, 1H), 7.55−7.53 (m, 3H), 7.10 (s,

1H), 6.98 (t, J = 4.0 Hz, 1H), 4.58 (s, 2H), 1.39 (s, 9H). LC-MS (ESI

+) 334.02 (M + H)⁺.

Ethyl 2-(1-Oxo-4-(phenylsulfonylimino)-1,4-dihydronaphthalen-

2-ylthio)acetate (9c). This compound was prepared using the

procedure described for compound 9a except using phenylsulfonamide

(157 mg, 1 mmol) to give pure product 9c (132 mg, 31.7%) as a

yellow solid. R_f= 0.50 (TLC, EtOAc/hexane [1:2]); mp 93−95 °C.

HPLC 95% (R_t= 5.11 min, 70% CH₃CN in 0.1% TFA water 20 min).

¹H NMR (400 MHz, CDCl₃) δ 8.11 (appdd, J = 7.2, 2.4 Hz, 2H), 8.07

(appd, J = 7.2 Hz, 2H), 7.99 (s, 1H), 7.65−7.62 (m, 3H), 7.58 (appt, J

= 8.0 Hz, 2H), 4.32 (q, J = 7.2 Hz, 2H), 3.81 (s, 2H), 1.34 (t, J = 7.2

1989

dx.doi.org/10.1021/jm201118h | J. Med. Chem. 2012, 55, 1978−1998

Journal of Medicinal Chemistry

Article

1

min). H NMR (400 MHz, CD₂Cl₂) δ 8.51 (s, 1H), 8.27−8.24 (m,

NMR (400 MHz, DMSO-d₆) δ 10.08 (s, 1H, disappeared on D₂O

shake), 9.68 (br s, 1H, disappeared on D₂O shake), 8.04 (d, J = 8.8 Hz,

1H), 7.82 (d, J = 4.0 Hz, 1H), 7.67 (d, J = 8.0 Hz, 1H), 7.38 (t, J = 7.2

Hz, 1H), 7.33 (appd, J = 2.4 Hz, 1H), 7.27 (t, J = 7.2 Hz, 1H), 7.03

(appt, J = 4.0 Hz, 1H), 6.89 (s, 1H), 4.55 (s, 2H). ¹³C NMR (100

MHz, DMSO-d₆) δ 171.66, 141.36, 140.97, 140.60, 133.76, 132.95,

128.26, 127.96, 125.98, 125.94, 125.26, 123.74, 123.56, 122.26, 117.23,

68.16. LC-MS (ESI−) 378.01 (M − H)⁻. HRMS (ESI−) m/z

calculated for C₁₆H₁₂NO₆S₂(M − H)⁻378.0112, found 378.0117.

2-(1-Hydroxy-4-(phenylsulfonamido)naphthalen-2-ylthio)acetic

Acid (11c). This compound was prepared using the procedure

described for 11a except using 10c (40 mg, 0.096 mmol) at rt

overnight (12−14 h). The title compound was obtained as an off-

white solid (20 mg, 53.6%); mp 100−102 °C. HPLC 94% (R_t= 9.3

min, 40% CH₃CN in 0.1% TFA water, 40 min). ¹H NMR (400 MHz,

DMSO-d₆) δ 12.75 (br s, 1H), 9.91 (s, 1H), 9.80 (br s, 1H), 8.10 (d, J

= 8.1 Hz, 1H), 7.83 (d, J = 8.3 Hz, 1H), 7.60 (d, J = 7.7 Hz, 2H), 7.56

(d, J = 7.3 Hz, 1H), 7.46 (t, J = 7.6 Hz, 2H), 7.39−7.36 (m, 2H), 6.96

(s, 1H), 3.47 (s, 2H). ¹³C NMR (100 MHz, DMSO-d₆) δ 171.74,

152.82, 140.39, 133.31, 131.82, 129.79, 129.72, 127.51, 127.33, 126.45,

125.71, 124.82, 124.02, 123.02, 113.60, 37.40. LC-MS (ESI−) 388.03

(M − H)⁻. HRMS (ESI−) m/z calculated for C₁₈H₁₄NO₅S₂(M −

H)⁻388.0319, found 388.0330.

1H), 7.87−7.85 (m, 1H), 7.69 (d, J = 7.4 Hz, 2H), 7.56 (t, J = 7.2 Hz,

1H), 7.51−7.47 (m, 2H), 7.43 (t, J = 7.9 Hz, 2H), 7.17 (s, 1H), 6.59

(br s, 1H), 4.17 (q, J = 7.1 Hz, 2H), 3.43 (s, 2H), 1.21 (t, J = 7.2 Hz,

3H). LC-MS (ESI+) 440.07 (M + Na)⁺. HRMS (ESI+) m/z calculated

for C₂₀H₁₉NNaO₅S₂(M + Na)⁺440.0597, found 440.0596.

Methyl 3-(1-Hydroxy-4-(thiophene-2-sulfonamido)naphthalen-

2-ylthio)propanoate (10d). This compound was prepared using the

procedure described for 10a except using starting material 9d (30 mg,

0.071 mmol). The title compound 10d was obtained without any

purification as a pale-yellow solid (28 mg, 93%). R_f= 0.20 (TLC,

EtOAc/hexane [1:2]); mp 117−119 °C. HPLC 97% (R_t= 4.09 min,

60% CH₃CN in 0.1% TFA water 20 min). ¹H NMR (400 MHz,

DMSO-d₆) δ 8.25 (dd, J = 6.4, 3.2 Hz, 1H), 7.87 (dd, J = 6.4, 3.2 Hz,

1H), 7.60 (br s, 1H), 7.52−7.48 (m, 3H), 7.41 (dd, J = 3.6 1.2 Hz,

1H), 7.32 (s, 1H), 6.95 (dd, J = 4.8, 3.6 Hz, 1H), 6.91 (br s, 1H), 3.70

(s, 3H), 2.93 (t, J = 7.1 Hz, 2H), 2.51 (t, J = 7.0 Hz, 2H). ¹³C NMR

(100 MHz, CDCl₃) δ 172.41, 154.89, 139.74, 133.29, 132.77, 132.48,

131.35, 128.54, 127.60, 126.54, 124.24, 123.76, 123.51, 122.35, 109.96,

52.31, 34.09, 31.79. LC-MS (ESI+) 446.01 (M + Na)⁺. HRMS (ESI+)

m/z calculated for C₁₈H₁₇NNaO₅S₃(M + Na)⁺446.0161, found

446.0157.

Ethyl 2-(1-Hydroxy-4-(thiophene-2-sulfonamido)naphthalen-2-

ylsulfonyl)acetate (10e). Ethyl 2-(1-hydroxy-4-(thiophene-2-

sulfonamido)naphthalen-2-ylthio)acetate (10a) (42.4 mg, 0.1 mmol)

was dissolved in acetone (2 mL), to which was added oxone (307.4 mg

in 2 mL of aqueous solution). The resulting mixture was stirred at rt

overnight (12−14 h). The organic solvent was evaporated, and the

aqueous phase was extracted with ethyl acetate. The combined organic

extracts were washed with water and brine and dried over Na₂SO₄.

The organic phase was filtered, and the filtrate was concentrated to

obtain 10e (47 mg, 100%) as a pale-yellow solid; mp 154−156 °C. ¹H

NMR (400 MHz, CDCl₃), δ 10.02 (s, 1H), 8.43 (d, J = 8.4 Hz, 1H),

7.98 (d, J = 8.4 Hz, 1H), 7.70 (t, J = 8.0 Hz, 1H), 7.62 (td, J = 8.0, 0.8

Hz, 1H), 7.58 (appdd, J = 5.0, 1.2 Hz, 1H), 7.43 (appdd, J = 4.0, 1.6

Hz, 1H), 7.29 (s, 1H), 7.00 (dd, J = 4.8, 3.6 Hz, 1H), 6.58 (s, 1H),

4.16 (q, J = 7.2 Hz, 2H), 4.12 (s, 2H), 1.15 (t, J = 7.2 Hz, 3H). ¹³C

NMR (100 MHz, CD₂Cl₂) δ 162.16, 155.75, 139.23, 134.91, 133.62,

133.21, 131.25, 127.86, 127.66, 125.75, 124.53, 124.26, 122.85, 122.26,

112.67, 63.05, 61.22, 13.77. LC-MS (ESI−) 454.01 (M − H)⁻. HRMS

(ESI−) m/z calculated for C₁₈H₁₇NO₇S₃(M − H)⁻454.0094, found

454.0112.

3-(1-Hydroxy-4-(thiophene-2-sulfonamido)naphthalen-2-ylthio)-

propanoic Acid (11d). This compound was prepared using the

procedure described for 11a except using 10d (43 mg, 0.1 mmol) at rt

overnight (12−14 h). The title compound was obtained as a white

solid (38 mg, 90.4%); mp 185 °C (dec.). HPLC 96% (R_t= 8.8 min,

1

40% CH₃CN in 0.1% TFA water, 40 min). H NMR (400 MHz,

DMSO-d₆) δ 12.35 (s, 1H), 10.07 (s, 1H), 9.70 (br s, 1H), 8.13 (d, J =

7.6 Hz, 1H), 7.91 (d, J = 7.8 Hz, 1H), 7.85 (td, J = 4.8, 0.5 Hz, 1H),

7.49−7.42 (m, 2H), 7.34 (td, J = 4.0, 1.6 Hz, 1H), 7.07−7.05 (m, 1H),

6.96 (s, 1H), 2.84 (t, J = 7.6 Hz, 2H), 2.37 (t, J = 6.8 Hz, 2H). ¹³C

NMR (100 MHz, DMSO-d₆) δ 173.40, 153.02, 140.76, 133.87, 133.07,

131.86, 129.69, 128.30, 127.31, 126.49, 125.77, 124.67, 124.06, 123.05,

113.58, 34.61, 29.92. LC-MS (ESI−) 408.00 (M − H)⁻. HRMS

(ESI−) m/z calculated for C₁₇H₁₄NO₅S₃(M − H)⁻408.0040, found

408.0054.

2-(1-Hydroxy-4-(thiophene-2-sulfonamido)naphthalen-2-

ylsulfonyl)acetic Acid (11e). Ethyl 2-(1-hydroxy-4-(thiophene-2-

sulfonamido)naphthalen-2-ylsulfonyl)-acetate (10e) (20 mg, 0.044

mmol) was dissolved in dioxane (2 mL) and conc HCl (2 mL) added.

The mixture was stirred at rt for 36 h. The solvent was removed using

the rotary evaporator, and the solid obtained was washed with

dichloromethane affording title compound 11e (18.3 mg, 97.3%) as an

off-white solid, mp 210−212 °C. HPLC 97% (R_t= 7.45 min, 35%

2-(1-Hydroxy-4-(thiophene-2-sulfonamido)naphthalen-2-ylthio)-

acetic Acid 11a (Compound 1). The ethyl 2-(1-hydroxy-4-

(thiophene-2-sulfonamido)naphthalen-2-ylthio)acetate (10a) (8 mg,

0.019 mmol) was dissolved in dioxane, (0.5 mL) and HCl (0.5 mL, 4

N) added. The reaction mixture was heated at 100 °C using the

microwave reactor for 10 min and diluted with ethyl acetate (20 mL)

and washed with water and brine. The organic phase was dried

(Na₂SO₄) and filtered, and the filtrate was concentrated to afford the

title compound as a pale-yellow solid (6 mg, 80%). R_f= 0.25 (TLC,

CH₃OH/DCM [1:10]); mp 175−177 °C. HPLC 97% (R_t= 15.6 min,

1

CH₃CN in 0.1% TFA water, 20 min). H NMR (400 MHz, DMSO-

d₆) δ 11.62 (br s, 1H), 10.24 (s, 1H), 8.37 (d, J = 7.6 Hz, 1H), 7.97 (d,

J = 7.6 Hz, 1H), 7.86 (dd, J = 5.2, 0.8 Hz, 1H), 7.64−7.58 (m, 2H),

7.35 (s, 1H), 7.33 (dd, J = 4.0, 0.8 Hz, 1H), 7.05 (dd, J = 4.9, 3.9 Hz,

1H), 4.52 (s, 2H). ¹³C NMR (100 MHz, CD₃OD) δ 164.35, 154.42,

139.92, 135.05, 132.84, 132.62, 129.98, 127.39, 126.83, 125.81, 124.99,

123.52, 123.48, 122.58, 115.59, 59.78. LC-MS (ESI−) 426.00 (M −

H)⁻. HRMS (ESI−) m/z calculated for C₁₆H₁₃NO₇S₃(M − H)⁻

425.9781, found 425.9788.

N-(3-Chloro-4-oxonaphthalen-1(4H)-ylidene)thiophene-2-sulfo-

namide (13a). The 2-chloro-1,4-naphthoquinone 12 (385 mg, 2

mmol) was added to thiophene-2-sulfonamide (326 mg, 2 mmol) in

DCM (15 mL) at 0 °C, followed by TiCl₄(2 mL, 1 M solution in

DCM) and TEA (0.613 mL, 4.4 mmol). The mixture was heated at 60

°C using the microwave reactor for 15 min, and the black mixture

obtained was poured into ethyl acetate (100 mL). The insoluble

particles were removed by filtering through a pad of Celite. The filtrate

was concentrated, and the residue obtained was suspended in DCM

(100 mL). The brown insoluble particles were removed by filtration,

and the filtrate was again concentrated to dryness. The residue was

suspended in ethyl acetate/hexane (1:1−20 mL), and the yellow solid

obtained was filtered. The solid was washed with ethyl acetate/hexane

(1:1, 5 mL × 2) and dried under vacuum to afford the title compound

as a yellow solid (378 mg, 55.9%). When TiCl₄·2THF (668 mg, 2

1

35% CH₃CN in 0.1% TFA water, 30 min). H NMR (400 MHz,

DMSO-d₆) δ 10.08 (s, 1H, disappeared on D₂O shake), 9.87 (br s, 1H,

disappeared on D₂O shake), 8.13 (d, J = 8.0 Hz, 1H), 7.85−7.83 (m,

1H, 2H), 7.48−7.39 (m, 2H), 7.33 (dd, J = 4.0, 1.6 Hz, 1H), 7.06−

7.03 (m, 2H), 3.52 (s, 2H). ¹³C NMR (100 MHz, DMSO-d₆) δ

171.11, 152.44, 140.21, 133.13, 132.38, 131.31, 129.38, 127.61, 126.78,

125.82, 125.05, 123.95, 123.21, 122.41, 112.95, 36.83. LC-MS (ESI−)

393.99 (M − H)⁻. HRMS (ESI−) m/z calculated for C₁₆H₁₂NO₅S₃

(M − H)⁻393.9883, found 393.9885.

2-(1-Hydroxy-4-(thiophene-2-sulfonamido)naphthalen-2-yloxy)-

acetic Acid (11b). The tert-butyl-2-(1-hydroxy-4-(thiophene-2-

sulfonamido)naphthalen-2-yloxy)acetate (10b) (0.025 g, 0.057

mmol) was dissolved in dioxane and concentrated hydrochloric acid

(dioxane/ HCl, 1:1, 4 mL) and stirred at rt for 3 h (the solution

changed from clear to white cloudy). The solvent was evaporated, and

the solid obtained was washed with DCM and hexane separately to get

pure product as a gray solid (0.021 g, 97%); mp = 155−157 °C. HPLC

1

90% (R_t= 6.48 min, 40% CH₃CN in 0.1% TFA water 20 min). H

1990

dx.doi.org/10.1021/jm201118h | J. Med. Chem. 2012, 55, 1978−1998

Journal of Medicinal Chemistry

Article

mol), TEA (0.615 mL, 4.4 mmol), and THF (15 mL) were used

instead of TiCl₄in DCM, the reaction afforded the title compound

with better yields also as a yellow solid (522 mg 77.3%). R_f= 0.53

N-(3-Chloro-4-oxonaphthalen-1(4H)-ylidene)-4′-fluorobiphenyl-

4-sulfonamide (13f). This compound was prepared using the

procedure described for 13a except using 4′-fluorobiphenyl-4-

sulfonamide (251 mg, 1 mmol), TiCl₄(1 mL,1 M solution in

DCM), TEA (308 mL, 2.2 mmol), and THF (10 mL) as the solvent.

The title compound was obtained as a yellow solid (348 mg, 81.6%);

1

(TLC, EtOAc/hexane [1:2]); mp 167−169 °C. H NMR (400 MHz,

CDCl₃) δ 8.62 (s, 1H), 8.24−8.20 (m, 2H), 7.86 (dd, J = 3.6, 1.2 Hz,

1H), 7.78−7.70 (m, 3H), 7.18 (dd, J = 4.8, 3.6 Hz, 1H). ¹³C NMR

(100 MHz, CDCl₃) δ 177.11, 160.88, 145.59, 141.08, 134.45, 134.28,

134.04, 133.81, 132.98, 131.61, 129.60, 128.16, 127.73, 127.24. LC-MS

(ESI+) 355.00 (M + NH₄)⁺. HRMS (ESI+) m/z calculated for

C₁₄H₉ClNO₃S₂(M + H)⁺337.9707, found 337.9708.

1

mp 172.1−172.8 °C. H NMR (400 MHz, CDCl₃) δ 8.68 (s, 1H),

8.20 (dd, J = 7.6, 1.2 Hz, 1H), 8.17 (dd, J = 8.0, 1.2 Hz, 1H), 8.13 (d, J

= 8.4 Hz, 2H), 7.77−7.75 (m, 2H), 7.72−7.66 (m, 2H), 7.60 (dd, J =

8.8, 5.2 Hz, 2H), 7.19 (t, J = 8.8 Hz, 2H). ¹⁹F NMR (376 MHz,

CDCl₃) δ −113.53 (m). ¹³C NMR (100 MHz, CDCl₃) δ 177.17,

163.46, (d, J = 245 Hz), 161.20, 145.74, 145.38, 139.04, 135.53 (d, J =

3.5 Hz), 134.36, 134.16, 133.09, 131.59, 129.35 (d, J = 8 Hz), 129.31,

128.33, 128.12, 127.87, 127.10, 116.36 (d, J = 21.5 Hz). LC-MS (ESI

+) 426 (M + H)⁺, 443.05 (M + NH₄)⁺. HRMS (ESI+) m/z calculated

for C₂₂H₁₄ClFNO₃S (M + H)⁺426.0362, found 426.0356.

N-(3-Chloro-4-oxonaphthalen-1(4H)-ylidene)biphenyl-4-sulfona-

mide (13b). This compound was prepared using the procedure

described for 13a except using 4-biphenylsulfonamide (233 mg, 1

mmol). The title compound 13b was obtained as a yellow solid (154

mg, 37.8%). When TiCl₄·2THF (668 mg, 2 mmol), TEA (0.615 mL,

4.4 mmol), and THF (15 mL) were used in the reaction, the title

compound 13b was obtained also as a yellow solid with improved yield

(586.7 mg, 71.9%). R_f= 0.60 (TLC, EtOAc/hexane [1:2]); mp 190−

N-(3-Chloro-4-oxonaphthalen-1(4H)-ylidene)-5-(pyridin-2-yl)-

thiophene-2-sulfonamide (13g). This compound was prepared using

the procedure described for 13a except using 5-(pyridin-2-yl)-

thiophene-2-sulfonamide (481 mg, 2 mmol), TiCl₄(2 mL, 1 M

solution in DCM), TEA (0.615 mL, 4.4 mmol), and THF (15 mL) as

the solvent. The title compound was obtained as an orange solid (511

mg, 61.5%); mp 155.3 °C (dec.). ¹H NMR (400 MHz, CDCl₃) δ 8.66

(d, J = 5.2 Hz, 1H), 8.60 (s, 1H), 8.28−8.26 (m, 1H), 8.21−8.18 (m,

1H), 7.87 (td, J = 7.8, 1.5 Hz, 1H), 7.84 (d, J = 4.0 Hz, 1H), 7.79 (s,

1H), 7.77 (s, 1H), 7.75−7.71 (m, 2H), 7.37 (dd, J = 6.7, 5.1 Hz, 1H).

¹³C NMR (100 MHz, DMSO-d₆) δ 176.99, 162.05, 153.71, 150.64,

1

192 °C. H NMR (400 MHz, CDCl₃) δ 8.71 (s, 1H), 8.24 (appt, J =

8.8 Hz, 2H), 8.14 (d, J = 8.6 Hz, 2H), 7.81 (d, J = 8.6 Hz, 2H), 7.74

(td, J = 7.2, 1.6 Hz, 1H), 7.69 (td, J = 8.0, 2.0 Hz, 1H), 7.64 (d, J = 8.0

Hz, 2H), 7.51 (t, J = 6.8 Hz, 2H), 7.46−7.43 (m, 1H). ¹³C NMR (100

MHz, CDCl₃) δ 177.21, 161.14, 146.82, 145.33, 139.40, 138.95,

134.37, 134.14, 133.12, 131.59, 129.91, 129.35, 128.93, 128.26, 128.11,

128.04, 127.64, 127.14. LC-MS (ESI+) 425.06 (M + NH₄)⁺. HRMS

(ESI+) m/z calculated for C₂₂H₁₅ClNO₃S (M + H)⁺408.0456, found

408.0460.

N-(3-Chloro-4-oxonaphthalen-1(4H)-ylidene)-5-phenylthio-

phene-2-sulfonamide (13c). This compound was prepared using the

procedure described for 13a except using 5-phenylthiophene-2-

sulfonamide (477 mg, 2 mmol), TiCl₄(2 mL, 1 M solution in

DCM), TEA (0.615 mL, 4.4 mol), and THF (15 mL) as the solvent.

The title compound was obtained as an orange solid (520 mg, 63.0%);

150.45, 145.71, 138.40, 135.74, 135.18, 135.13, 132.96, 132.22, 128.59,

128.00, 127.09, 125.94, 125.01, 120.42, 104.99. LC-MS (ESI+) 414.99

(M + H)⁺. HRMS (ESI+) m/z calculated for C₁₉H₁₂ClN₂O₃S₂(M +

H)⁺414.9972, found 414.9969.

N-(3-Chloro-4-oxonaphthalen-1(4H)-ylidene)-4-cyclohexylbenze-

nesulfonamide (13h). This compound was prepared using the

procedure described for 13a except using 4-cyclohexylphenylsulfona-

mide (290 mg, 1.2 mmol), TiCl₄(1.2 mL, 1 M solution in DCM),

TEA (0.372 mL, 2.7 mmol), and THF (10 mL) as the solvent. The

1

mp 112.4 °C (dec.). H NMR (400 MHz, CDCl₃) δ 8.65 (s, 1H),

8.27−8.25 (m, 1H), 8.22−8.19 (m, 1H), 7.81 (d, J = 4.0 Hz, 1H),

7.77−7.70 (m, 2H), 7.65 (dd, J = 8.4, 1.6 Hz, 2H), 7.47−7.41 (m,

3H), 7.32 (d, J = 3.6 Hz, 1H). ¹³C NMR (100 MHz, CDCl₃) δ 177.14,

160.72, 153.69, 145.55, 138.88, 134.73, 134.45, 134.25, 133.03, 132.73,

131.62, 129.73, 129.54, 129.52, 128.15, 127.28, 126.65, 123.29. LC-MS

(ESI+) 414.00 (M + H)⁺. HRMS (ESI+) m/z calculated for

C₂₀H₁₃ClNO₃S₂(M + H)⁺414.0020, found 414.0018.

N-(3-Chloro-4-oxonaphthalen-1(4H)-ylidene)-4-phenoxybenze-

nesulfonamide (13d). This compound was prepared using the

procedure described for 13a except using 4-phenoxyphenylesulfona-

mide (434 mg, 2 mmol), TiCl₄(2 mL, 1 M solution in DCM), TEA

(0.615 mL, 4.4 mmol), and THF (15 mL) as the solvent. The title

compound was obtained as a yellow solid, (526 mg, 67.2%) mp 124.8

°C (dec.). ¹H NMR (400 MHz, CDCl₃) δ 8.67 (s, 1H), 8.19 (appdd, J

= 7.6, 1.6 Hz, 1H), 8.16 (appdd, J = 7.6, 1.6 Hz, 1H), 8.00 (d, J = 9.2

Hz, 2H), 7.73 (td, J = 7.6, 1.6 Hz, 1H), 7.67 (td, J = 7.6, 1.6 Hz, 1H),

7.44−7.40 (m, 2H), 7.26−7.22 (m, 1H), 7.15−7.08 (m, 4H). ¹³C

NMR (100 MHz, CDCl₃) δ 177.22, 162.67, 160.78, 155.11, 145.21,

134.33, 134.08, 133.81, 133.15, 131.58, 130.48, 130.09, 129.78, 128.08,

127.07, 125.42, 120.69, 117.76. LC-MS (ESI+) 424.03 (M + H)⁺.

HRMS (ESI+) m/z calculated for C₂₂H₁₅ClNO₄S (M + H)⁺424.0405,

found 424.0403.

N-(3-Chloro-4-oxonaphthalen-1(4H)-ylidene)naphthalene-2-sul-

fonamide (13e). This compound was prepared using the procedure

described for 13a except using naphthalene-2-sulfonamide (415 mg, 2

mmol), TiCl₄·2THF (668 mg, 2 mmol), TEA (0.615 mL, 4.4 mmol),

and THF (15 mL) as the solvent. The title compound was obtained as

a yellow solid (0. 595 g, 77.9%). R_f= 0.55 (TLC, EtOAc/hexane

[1:2]); mp 200−202 °C. ¹H NMR (400 MHz, CDCl₃) δ 8.73 (s, 1H),

8.64 (s, 1H), 8.20 (appd, 7.6 Hz, 1H), 8.14 (appd, J = 8.0 Hz, 1H),

8.05−8.03 (m, 3H), 7.96 (d, 8.4 Hz, 1H), 7.72 (appq, J = 7.4 Hz, 2H),

7.66 (appt, J = 7.1 Hz, 2H). ¹³C NMR (100 MHz, CDCl₃) δ 177.05,

160.98, 145.15, 137.09, 135.34, 134.38, 134.14, 132.92, 132.11, 131.42,

129.77, 129.64, 129.57, 129.00, 128.15, 127.95, 127.04, 122.61. LC-MS

(ESI+) 382.03 (M + H)⁺. HRMS (ESI+) m/z calculated for

C₂₀H₁₃ClNO₃S (M + H)⁺382.0299, found 382.0301.

1

title compound was obtained as a yellow solid (213 mg, 42.4%). H

NMR (400 MHz, CDCl₃) δ 8.68 (s, 1H), 8.19−8.15 (m, 2H), 7.97 (d,

J = 8.4 Hz, 2H), 7.72 (td, J = 7.5, 1.5 Hz, 1H), 7.67 (td, J = 7.6, 1.6 Hz,

1H), 7.42 (d, J = 8.4 Hz, 2H), 2.64−2.58 (m, 1H), 1.91−1.85 (m,

4H), 1.79−1.75 (m, 1H), 1.50−1.34 (m, 4H), 1.31−1.23 (m, 1H). ¹³C

NMR (100 MHz, CDCl₃) δ 177.24, 160.85, 154.67, 145.12, 137.66,

134.32, 134.03, 133.18, 131.56, 129.85, 128.03, 127.90, 127.83, 127.12,

44.93, 34.32, 26.87, 26.17. LC-MS (ESI+) 414.09 (M + H)⁺. HRMS

(ESI+) m/z calculated for C₂₂H₂₁ClNO₃S (M + H)⁺414.0925, found

414.0924.

N-(3-Chloro-4-oxonaphthalen-1(4H)-ylidene)-4′-methoxybi-

phenyl-4-sulfonamide (13i). This compound was prepared using the

procedure described for 13a except using 4′-methoxybiphenyl-4-

sulfonamide (527 mg, 2 mmol), TiCl₄(2 mL, 1 M solution in DCM),

TEA (0.615 mL, 4.4 mmol), and THF (15 mL) as solvent. The title

compound was obtained as a yellow solid (650 mg, 74.2%); mp 168.1

°C (dec.). ¹H NMR (400 MHz, CDCl₃) δ 8.70 (s, 1H), 8.19 (apptd, J

= 8.8, 1.6 Hz, 2H), 8.10 (d, J = 8.6 Hz, 2H), 7.76 (d, J = 8.6 Hz, 2H,

partially overlapped with the adjacent multiplet), 7.76−7.71 (m, 1H,

partially overlapped with the adjacent doublet), 7.68 (td, J = 7.6, 1.6

Hz, 1H), 7.59 (d, J = 8.8 Hz, 2H), 7.02 (d, J = 8.8 Hz, 2H), 3.88 (s,

3H). ¹³C NMR (100 MHz, CDCl₃) δ 177.21, 160.99, 160.48, 146.39,

145.26, 138.18, 134.34, 134.08, 133.15, 131.70, 131.58, 129.87, 128.77,

128.27, 128.07, 127.38, 127.12, 114.79, 55.65. LC-MS (ESI+) 438.04

(M + H)⁺. HRMS (ESI+) m/z calculated for C₂₃H₁₇ClNO₄S (M +

H)⁺438.0561, found 438.0562.

N-(3-Chloro-4-oxonaphthalen-1(4H)-ylidene)-4-pentylbenzene-

sulfonamide (13j). This compound was prepared using the procedure

described for 13a except using 4-pentylphenylsulfonamide (455 mg, 2

mmoL), TiCl₄(2 mL, 1 M solution in DCM), TEA (0.615 mL, 4.4

mmol), and THF (15 mL) as solvent, and the product was purified

using SiO₂chromatography (hexane/EtOAc gradient elution) to

afford the title compound as a yellow solid (452 mg, 56.2%); mp

1

111.7−112.8 °C. H NMR (400 MHz, CDCl₃) δ 8.69 (s, 1H), 8.20

1991

dx.doi.org/10.1021/jm201118h | J. Med. Chem. 2012, 55, 1978−1998

Journal of Medicinal Chemistry

Article

(dd, J = 7.6, 1.2 Hz, 1H), 8.16 (dd, J = 7.2, 1.6 Hz, 1H), 7.97 (d, J =

8.4 Hz, 2H), 7.73 (td, J = 7.5, 1.5 Hz, 1H), 7.68 (td, J = 7.6, 1.6 Hz,

1H), 7.40 (d, J = 8.4 Hz, 2H), 2.72 (t, J = 7.7 Hz, 2H), 1.66 (q, J = 7.5

Hz, 2H), 1.42−1.30 (m, 4H), 0.90 (t, J = 7.0 Hz, 3H). ¹³C NMR (100

MHz, CDCl₃) δ 177.24, 160.86, 149.79, 145.15, 137.64, 134.30,

134.02, 133.19, 131.57, 129.86, 129.39, 128.04, 127.77, 127.10, 36.19,

31.62, 30.99, 22.70, 14.22. LC-MS (ESI+) 402 (M + H)⁺, 419.11 (M +

NH₄)⁺. HRMS (ESI+) m/z calculated for C₂₁H₂₁ClNO₃S (M + H)⁺

402.0925, found 402.0926.

5-Chloro-N-(3-chloro-4-oxonaphthalen-1(4H)-ylidene)-

thiophene-2-sulfonamide (13k). This compound was prepared using

the procedure described for 13a except using 5-chlorothiophene-2-

sulfonamide (395 mg, 2 mmol), TiCl₄(2 mL, 1 M solution in DCM),

TEA (0.615 mL, 4.4 mol), and DCM (15 mL) as solvent. The title

compound was obtained as a yellow solid (320 mg, 43.0%). R_f= 0.50

(TLC, EtOAc/hexane [1:2]); mp 149−151 °C. ¹H NMR, (400 MHz,

CDCl₃) δ 8.55 (s, 1H), 8.23−8.20 (m, 2H), 7.79−7.72 (m, 2H), 7.64

(d, J = 4.1 Hz, 1H), 7.01 (d, J = 4.1 Hz, 1H). ¹³C NMR (100 MHz,

CDCl₃) δ 176.99, 161.21, 145.85, 139.77, 134.53, 134.47, 133.10,

132.78, 131.60, 129.58, 128.25, 127.24, 127.00, 104.99. LC-MS (ESI+)

761.89 (2M + NH₄)⁺. HRMS (ESI+) m/z calculated for

C₁₄H₈Cl₂NO₃S₂(M + H)⁺371.9317, found 371.9324.

N-(3-Chloro-4-oxonaphthalen-1(4H)-ylidene)-4′-trifluoromethyl-

biphenyl-4-sulfonamide (13l). This compound was prepared using

the procedure described for 13a except using 4′-trifluoromethylbi-

phenyl-4-sulfonamide (603 mg, 2 mmol), TiCl₄(2 mL, 1 M solution

in DCM), TEA (0.615 mL, 4.4 mmol), and THF (15 mL) as the

solvent. The title compound was obtained as a yellow solid (794 mg,

83.4%); mp 190.4−191.3 °C. ¹H NMR (400 MHz, CDCl₃) δ 8.67 (s,

1H), 8.21 (dd, J = 7.6, 1.2 Hz, 1H), 8.18−8.16 (m, 2H), 8.17 (d, J =

8.6 Hz, 1H), 7.81 (d, J = 8.6 Hz, 2H), 7.78−7.72 (m, 5H), 7.68 (td, J =

7.6, 1.2 Hz, 1H). ¹³C NMR (100 MHz, CDCl₃) δ 177.12, 161.41,

145.50, 145.20, 142.93, 140.04, 134.36, 134.22, 133.05, 131.61, 130.95

(q, J = 32.5 Hz), 129.92, 128.42, 128.26, 128.16, 128.01, 127.09,

126.30 (q, J = 3.7 Hz), 124.23 (d, J = 270.7 Hz). ¹⁹F NMR (376 MHz,

CDCl₃) δ −63.01 (s). LC-MS (ESI+) 493.05 (M + NH₄)⁺. HRMS

(ESI+) m/z calculated for C₂₃H₁₄ClF₃NO₃S (M + H)⁺476.0330,

found 476.0325.

N-(3-Chloro-4-oxonaphthalen-1(4H)-ylidene)-5-(phenylsulfonyl)-

thiophene-2-sulfonamide (13m). This compound was prepared using

the procedure described for 13a except using 5-(phenylsulfonyl)-

thiophene-2-sulfonamide (341 mg, 1.2 mmol), TiCl₄(1.1 mL, 1 M

solution in DCM), TEA (0.345 mL, 2.5 mmol), and THF (10 mL) as

the solvent. The title compound was obtained as a yellow solid (272

mg, 50.7%); mp 165.3 °C (dec.). ¹H NMR (400 MHz, CDCl₃) δ 8.43

(s, 1H), 8.22−8.19 (m, 2H), 8.06−8.01(m, 2H), 7.79−7.76 (m, 2H),

7.73 (d, J = 4.0 Hz, 1H), 7.68−7.64 (m, 2H), 7.60−7.56 (m, 2H). ¹³C

NMR (100 MHz, CDCl₃) δ 162.41, 150.49, 148.23, 146.44, 140.75,

134.85, 134.73, 134.52, 132.52, 132.46, 132.34, 131.59, 129.98, 129.70,

128.40, 128.00, 127.40, 104.99. Elemental analysis for 13m:

Calculated: C, 50.26; H, 2.53; N, 2.93. Found: C, 50.53; H, 2.85; N,

2.68.

M solution in DCM), TEA (0.615 mL, 4.4 mmol), and THF (15 mL)

as the solvent. The title compound was obtained as an orange−red

solid (0.653 mg, 85.5%) R_f= 0.67 (TLC, EtOAc/hexane [1:2]); mp

1

185.6 °C (dec.). H NMR (400 MHz, CDCl₃) δ 8.75 (s, 1H), 8.67

(dd, J = 8.8, 0.8 Hz, 1H), 8.44 (dd, J = 7.4, 1.6 Hz, 1H), 8.21−8.17 (m,

2H), 8.00 (appdt, J = 7.9, 1.9 Hz, 2H), 7.72−7.62 (m, 4H), 7.59 (td, J

= 8.0, 1.6 Hz, 1H). ¹³C NMR (100 MHz, CDCl₃) δ 177.20, 161.53,

145.34, 135.61, 135.51, 134.47, 134.41, 134.08, 133.21, 131.61, 130.28,

129.32, 129.22, 128.78, 128.64, 128.08, 127.29, 127.14, 125.41, 124.44.

LC-MS (ESI+) 382 (M + H)⁺, 399.06 (M + NH₄)⁺. HRMS (ESI+)

m/z calculated for C₂₀H₁₃ClNO₃S (M + H)⁺382.0299, found

382.0300.

4-Chloro-N-(3-chloro-4-oxonaphthalen-1(4H)-ylidene)-

benzenesulfonamide (13p). This compound was prepared using the

procedure described for 13a except using 4-chlorobenzenesulfonamide

(383 mg, 2 mmol), TiCl₄(2 mL, 1 M solution in DCM), TEA (0.615

mL, 4.4 mmol), and THF (15 mL) as the solvent. The title compound

was obtained as a yellow solid (399 mg, 54.5%). R_f= 0.60 (TLC,

EtOAc/hexane [1:2]); mp 138−140 °C. ¹H NMR (400 MHz, CDCl₃)

δ 8.62 (s, 1H), 8.21 (dd, J = 7.6, 1.6 Hz, 1H), 8.12 (dd, J = 7.6, 1.2 Hz,

1H), 8.01 (d, J = 8.7 Hz, 2H), 7.75 (td, J = 8.8,1.2, Hz, 1H), 7.68 (td, J

= 7.6, 1.6 Hz, 1H), 7.58 (d, J = 8.4 Hz, 2H). ¹³C NMR (100 MHz,

CDCl₃) δ 177.07, 161.51, 145.59, 140.47, 138.99, 134.41, 134.30,

132.93, 131.58, 129.88, 129.72, 129.17, 128.18, 127.07. LC-MS (ESI+)

383.00 (M + NH₄)⁺. HRMS (ESI+) m/z calculated for

C₁₆H₁₀Cl₂NO₃S (M + H)⁺365.9753, found 365.9763.

3,4-Dichloro-N-(3-chloro-4-oxonaphthalen-1(4H)-ylidene)-

benzenesulfonamide (13q). This compound was prepared using the

procedure described for 13a except using 3,4-dichlorobenzenesulfo-

namide (452 mg, 2 mmol), TiCl₄(2 mL, 1 M solution in DCM), TEA

(0.615 mL, 4.4 mmol), and THF (15 mL) as the solvent. The title

compound was obtained as a yellow solid (622 mg, 77.6%). R_f= 0.41

1

(TLC, EtOAc/hexane [1:2]); mp 140.2−141.7 °C. H NMR (400

MHz, CDCl₃) δ 8.57 (s, 1H), 8.22 (dd, J = 7.7, 1.4 Hz, 1H), 8.16 (d, J

= 2.2 Hz, 1H), 8.12 (dd, J = 8.0, 1.6 Hz, 1H), 7.90 (dd, J = 8.4, 2.2 Hz,

1H), 7.77 (td, J = 7.2, 1.2 Hz, 1H), 7.72−7.68 (m, 2H). ¹³C NMR

(100 MHz, CDCl₃) δ 176.97, 162.00, 145.89, 140.15, 138.81, 134.49,

134.10, 132.75, 131.57, 131.47, 129.90, 129.68, 128.27, 127.14, 126.73.

LC-MS (ESI+) 817.90 (2M + NH₄)⁺. HRMS (ESI+) m/z calculated

for C₁₆H₉Cl₃NO₃S (M + H)⁺399.9363, found 399.9375.

N - ( 3 - C h l o r o - 4 - o x o n a p h t h a l e n - 1 ( 4 H ) - y l i d e n e ) -

benzenesulfonamide (13r). This compound was prepared using the

procedure described for 13a except using phenylsulfonamide (314 mg,

2 mmol), TiCl₄(2 mL, 1 M solution in DCM), TEA (0.615 mL, 4.4

mmol), and THF (15 mL) as the solvent. The title compound was

obtained as a yellow solid (508 mg, 76.6%). R_f= 0.31 (TLC, EtOAc/

1

hexane [1:4]); mp 184.8−186.4 °C. H NMR (400 MHz, CDCl₃) δ

8.67 (s, 1H), 8.20 (dd, J = 7.6, 1.2 Hz, 1H), 8.15 (d, J = 7.6 Hz, 1H),

8.09 (d, J = 7.2 Hz, 2H), 7.74 (td, J = 7.2, 1.2 Hz, 1H), 7.71−7.66 (m,

2H), 7.62 (t, J = 8.0 Hz, 2H). ¹³C NMR (100 MHz, CDCl₃) δ 177.18,

161.22, 145.33, 140.49, 134.36, 134.14, 133.81, 133.08, 131.57, 129.93,

129.40, 128.09, 127.68, 127.09. LC-MS (ESI+) 349.03 (M + NH₄)⁺.

HRMS (ESI+) m/z calculated for C₁₆H₁₁ClNO₃S (M + H)⁺332.0143,

found 332.0145.

N-(3-Chloro-4-oxonaphthalen-1(4H)-ylidene)-1-(phenylsulfonyl)-

1H-pyrrole-3-sulfonamide (13n). This compound was prepared using

the procedure described for 13a except using 1-(phenylsulfonyl)-1H-

pyrrole-3-sulfonamide (390 mg, 1.4 mmol), TiCl₄(1.4 mL, 1 M

solution in DCM), TEA (0.42 mL, 3 mmol), and THF (10 mL) as the

solvent. The title compound was obtained as a yellow solid (444 mg,

70.7%); mp 127.5−131.3 °C. ¹H NMR (400 MHz, CDCl₃) δ 8.55 (s,

1H), 8.20−8.16 (m, 2H), 7.97−7.95 (m, 2H), 7.85 (dd, J = 2.4, 1.6

Hz, 1H), 7.76−7.68 (m, 3H), 7.60 (t, J = 7.6 Hz, 2H), 7.27 (dd, J =

3.4, 2.4 Hz, 1H), 6.74 (dd, J = 3.4, 1.7 Hz, 1H). ¹³C NMR (100 MHz,

CDCl₃) δ 177.11, 161.01, 145.34, 137.75, 135.29, 134.41, 134.21,

132.97, 131.58, 130.18, 129.76, 128.88, 128.13, 127.71, 127.11, 124.19,

122.43, 111.92. LC-MS (ESI+) 461.00 (M + H)⁺. HRMS (ESI+) m/z

calculated for C₂₀H₁₄ClN₂O₅S₂(M + H)⁺461.0027, found 461.0024.

N-(3-Chloro-4-oxonaphthalen-1(4H)-ylidene)naphthalene-1-sul-

fonamide (13o, intermediate for compound compound 34). This

compound was prepared using the procedure described for 13a except

using naphthalene-1-sulfonamide (415 mg, 2 mmol), TiCl₄(2 mL, 1

2-(1-Oxo-4-(thiophen-2-ylsulfonylimino)-1,4-dihydronaphtha-

len-2-ylthio)acetic Acid (14a). The 13a (188 mg, 0.56 mmol) was

dissolved in THF (5 mL), and THF solution containing pyridine (0.56

mL, 0.5 M)was added, followed by THF solution containing 2-

mercaptoglycolic acid (0.56 mL, 0.5 M). Additional pyridine (0.56 mL,

0.5 M in THF) and 2-mercaptoglycolic acid (0.56 mL, 0.5 M in THF)

were added to the mixture. The mixture was stirred at room

temperature for 30 min, and 2,3-dichloro-5,6-dicyanobenzoquinone

(114 mg, 0.5 mmol) was added and stirred at room temperature

overnight (12 h). The insoluble solid obtained was filtered, and the

filtrate was concentrated. The crude residue was first purified via

preparative TLC (2.5% CH₃OH in DCM) and then using SiO₂

column chromatography (CH₃OH/CH₃COOH/DCM

[1.5:0.5:100]) to afford a yellow solid as the desired pure product

14a (20 mg, 9.2%) and a mixture of desired product and reduced

product (80.9 mg, 36.9%). R_f= 0.33 (TLC, CH₃OH/DCM [1:20]);

1992

dx.doi.org/10.1021/jm201118h | J. Med. Chem. 2012, 55, 1978−1998

Journal of Medicinal Chemistry

Article

1

mp 131.7 °C (dec.). H NMR (400 MHz, CD₃CN) δ 8.21−8.19 (m,

1.2 Hz, 1H), 7.61 (dd, J = 6.5, 3.4 Hz, 2H), 7.38 (dd, J = 4.0, 1.2 Hz,

1H), 7.16 (s, 1H), 6.99 (dd, J = 4.8, 3.6 Hz, 1H), 4.00 (s, 3H). ¹³C

NMR (100 MHz, DMSO-d₆) δ 154.04, 152.73, 140.64, 133.86, 133.07,

132.82, 129.49, 128.42, 128.23, 127.00, 126.30, 125.42, 124.16, 123.42,

107.44, 34.73. LC-MS (ESI+) 420.02 (M + H)⁺, 442.00 (M + Na)⁺.

HRMS (ESI+) m/z calculated for C₁₆H₁₄N₅O₃S₃(M + H)⁺420.0253,

found 420.0240.

1H), 8.12−8.10 (m, 1H), 7.92−7.90 (m, 2H), 7.87 (dd, J = 3.8, 1.3

Hz, 1H), 7.80−7.78 (m, 2H), 7.24 (dd, J = 4.8, 3.6 Hz, 1H), 3.88 (s,

2H). ¹³C NMR (100 MHz, CDCl₃) δ 180.77, 168.99, 160.11, 153.94,

141.97, 134.37, 133.54, 133.34, 133.22 132.94, 131.78, 127.59, 127.43,

127.17, 120.53, 33.90. LC-MS (ESI−) 391.97 (M − H)⁻. HRMS

(ESI−) m/z calculated for C₁₆H₁₀NO₅S₃(M − H)⁻391.9727, found

391.9729.

N-(3-(1H-1,2,4-Triazol-5-ylthio)-4-hydroxynaphthalen-1-yl)-

thiophene-2-sulfonamide (15c). This compound was prepared using

the procedure described for 15b using 14c (20 mg, 0.05 mmol) and

sodium hydrosulfite (43 mg, 0.25 mmol) to afford the title compound

as a white solid (20 mg, 100%). R_f= 0.40 (TLC, EtOAc/hexane

[1:1]); mp 180 °C (dec.). HPLC 92% (R_t= 5.4 min, 40% CH₃CN in

0.1% TFA water 40 min). ¹H NMR (400 MHz, DMSO-d₆) δ 10.19 (br

s, 1H), 10.05 (s, 1H), 8.61 (br s, 1H), 8.16 (d, J = 7.6 Hz, 1H), 7.89

(d, J = 7.4 Hz, 1H), 7.81 (d, J = 4.2 Hz, 1H), 7.48 (brt, J = 7.2 Hz,

2H), 7.28 (d, J = 2.5 Hz, 1H), 6.99 (brt, J = 4.2 Hz, 1H), 6.90 (br s,

1H). ¹³C NMR (100 MHz, DMSO-d₆) δ 140.86, 133.68, 133.00,

132.93, 129.47, 128.16, 126.66, 126.60, 126.28, 124.90, 124.04, 123.14,

104.99. LC-MS (ESI−) 403.00 (M − H)⁻. HRMS (ESI−) m/z

calculated for C₁₆H₁₁N₄O₃S₃(M − H)⁻402.9999, found 402.9989.

N-(3-(1H-Tetrazol-5-ylthio)-4-hydroxynaphthalen-1-yl)-

thiophene-2-sulfonamide (15d). 13a (34 mg, 0.1 mmol) and 1H-

tetrazole-5-thiol (10 mg, 0.1 mmol) were dissolved in EtOH/DCM (2

mL, 1:1) and stirred at rt for 2 h. The reaction mixture was diluted

with EtOAc (20 mL), and Na₂S₂O₄(0.5 mmol in 5 mL of water) was

added. The mixture was shaken in a separation funnel until the color of

the organic phase turned colorless (from bright yellow). The organic

phase was separated and washed with water (5 mL) and brine (5 mL)

and dried (Na₂SO₄). The organic phase was filtered and concentrated,

and the residue was slurred in DCM (5 mL). The solid obtained was

washed with DCM (1 mL × 2) and dried to afford the title compound

15d (28 mg, 69.9%, via 2 steps) as an off-white solid; mp 186.6 °C

(dec.). HPLC 99% (R_t= 9.5 min, 35% CH₃CN in 0.1% TFA water 30

N-(3-(1-Methyl-1H-tetrazol-5-ylthio)-4-oxonaphthalen-1(4H)-

ylidene)thiophene-2-sulfonamide (14b). The 13a (36 mg, 0.1 mmol)

was dissolved in THF (3 mL), and 1-methyl-tetrazole-5-thiol (11.7

mg, 0.1 mol) was added. The reaction mixture was stirred at rt for 2 h

and concentrated. The residue was dissolved in DCM and triturated

with hexane. The precipitate obtained was filtered and washed with

DCM/hexane (1:1, 2 mL × 3) to afford the title compound as an

orange−red solid (29 mg, 68.9%). R_f= 0.80 (TLC, EtOAc/hexane

1

[7:3]); mp 172 °C (dec.). H NMR (400 MHz, CDCl₃) δ 8.26−8.24

(m, 1H), 8.17−8.15 (m, 1H), 8.01 (s, 1H), 7.78 (d, J = 3.8 Hz, 1H),

7.76−7.72 (m, 3H), 7.15 (dd, J = 5.2, 4.4 Hz, 1H), 4.21 (s, 3H). ¹³C

NMR (100 MHz, DMSO-d₆) δ 180.28, 160.98, 149.29, 147.61, 140.87,

136.15, 135.46, 134.90, 134.26, 133.33, 132.00, 128.82, 127.64, 127.15,

122.73, 35.38. LC-MS (ESI+) 418.01 (M + H)⁺. HRMS (ESI+) m/z

calculated for C₁₆H₁₂N₅O₃S₃(M + H)⁺418.0097, found 418.0099.

N-(3-(1H-1,2,4-Triazol-5-ylthio)-4-oxonaphthalen-1(4H)-ylidene)-

thiophene-2-sulfonamide (14c). This compound was prepared using

the procedure described for 14b except using 3-mercapto-1,2,4-triazole

(10 mg, 0.1 mmol). The title compound 14c was obtained as an

orange−red solid (39 mg, 96.5%). R_f= 0.33 (TLC, EtOAc/hexane

[1:1]); mp 197 °C (dec.). HPLC 95% (R_t= 4.08 min, 55% CH₃CN in

1

0.1% TFA water 20 min). H NMR (400 MHz, CD₃CN), δ 8.63 (s,

1H), 8.19−8.17 (m, 1H), 8.15−8.14 (m, 1H), 7.90−7.88 (m, 1H),

7.81−7.79 (m, 3H), 7.75−7.74 (m, 1H), 7.22−7.19 (m,1H). ¹³C

NMR (100 MHz, DMSO-d₆) δ 179.55, 160.03, 152.17, 150.60, 146.29,

134.58, 134.15, 133.49, 132.73, 132.23, 130.92, 127.58, 126.46, 125.92,

120.99, 117.56. LC-MS (ESI+) 402.99 (M + H)⁺. HRMS (ESI+) m/z

calculated for C₁₆H₁₁N₄O₃S₃(M + H)⁺402.9988, found 402.9989.

2-(1-Hydroxy-4-(thiophene-2-sulfonamido)naphthalen-2-ylthio)-

acetic Acid (15a). The (E)-N-(3-chloro-4-oxonaphthalen-1(4H)-

ylidene)thiophene-2-sulfonamide (13 a) (34 mg, 0.1 mmol) was

dissolved in THF (2 mL) and a THF solution was added containing

thioglycolic acid (0.1 mL, 1 M in THF) followed by pyridine (1 equiv,

0.2 mL, 0.5 M in THF). The mixture was stirred at rt for 10 min, and

the solvent was removed using a rotary evaporator. The orange−red

residue obtained was redissolved in ethyl acetate (50 mL). The

mixture was transferred to a separation funnel and washed with

NaHSO₄(0.5 M solution, 10 mL × 2) to remove pyridine. The

sodium hydrosulfite solid (5 equiv, 87 mg, 0.5 mmol) was added

followed by water (10 mL). The mixture was shaken until the organic

phase turned colorless. The organic phase was separated and washed

with water (10 mL × 2) and brine (10 mL), dried (Na₂SO₄), and

filtered. The filtrate was concentrated. The solid obtained was

suspended in DCM/hexane (1:1, ∼5 mL), filtered, and the product

was washed with DCM (1 mL × 3) to afford title compound as an off-

white solid (25 mg, 63.6%). The analytical data obtained for

compound 15a are identical to that obtained for 11a.

1

min). H NMR (400 MHz, DMSO-d₆) δ 10.63 (br s, 1H), 10.14 (s,

1H), 8.25−8.23 (m, 1H), 7.96−7.94 (m, 1H), 7.82 (d, J = 4.8 Hz,

1H), 7.56−7.54 (m, 2H), 7.32 (d, J = 3.6 Hz, 1H), 6.97 (t, J = 4.0 Hz,

1H), 6.92 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆) δ 154.80, 140.56,

133.81, 133.17, 133.13, 130.21, 128.41, 128.13, 126.87, 126.47, 125.29,

124.16, 123.57. LC-MS (ESI+) 406.01 (M + H)⁺. HRMS (ESI+) m/z

calculated for C₁₅H₁₂N₅O₃S₃(M + H)⁺406.0097, found 406.0075.

N-(3-(1H-Tetrazol-5-ylthio)-4-hydroxynaphthalen-1-yl)biphenyl-

4-sulfonamide (15e). This compound was prepared using the

procedure described for 15d except using 13b (41 mg, 0.1 mmol)

to afford the title compound 15e (32 mg, 67.4%, via 2 steps) as a white

solid; mp 158.8 °C (dec.). HPLC 94% (R_t= 7.8 min, 50% CH₃CN in

0.1% TFA water 30 min). ¹H NMR (400 MHz, DMSO-d₆) δ 10.00 (s,

1H), 8.24−8.22 (m, 1H), 8.02−8.00 (m, 1H), 7.72−7.63 (m, 6H),

7.55−7.53 (m, 2H), 7.51−7.47 (m, 2H), 7.45−7.40 (m, 1H), 6.87 (s,

1H). ¹³C NMR (100 MHz, DMSO-d₆) δ 154.63, 144.81, 139.08,

138.97, 133.08, 129.95, 129.77, 129.20, 128.34, 128.20, 127.78, 127.70,

126.86, 126.51, 125.58, 124.39, 123.55. LC-MS (ESI+) 476.09 (M +

H)⁺. HRMS (ESI+) m/z calculated for C₂₃H₁₈N₅O₃S₂(M + H)⁺

476.0846, found 476.0842.

N-(3-(1H-Tetrazol-5-ylthio)-4-hydroxynaphthalen-1-yl)-5-phenyl-

thiophene-2-sulfonamide (15f). This compound was prepared using

the procedure described for 15d except using 13c (41 mg, 0.1 mmol),

to afford the title compound 15f (34 mg, 70.1%, via 2 steps) as an off-

white solid; mp 167.9 °C (dec.). HPLC 98% (R_t= 7.7 min, 50%

N-(4-Hydroxy-3-(1-methyl-1H-tetrazol-5-ylthio)naphthalen-1-yl)-

thiophene-2-sulfonamide (15b). 14b (13 mg, 0.031 mmol) was

dissolved in ethyl acetate (50 mL), and sodium hydrosulfite (27 mg,

0.156 mmol) was added followed by water (10 mL). The mixture was

shaken in a separating funnel until the yellow organic phase turned

colorless. The organic phase was washed with water (10 mL × 3) and

brine (10 mL), dried (Na₂SO₄), and concentrated. The residue

obtained was dissolved in DCM (3 mL) and triturated with hexane (3

mL). The precipitate was washed with DCM/hexane (1:1, 1 mL × 3)

and dried under vacuum to afford the title compound 15b as a white

solid (13 mg, 99%). R_f= 0.44 (TLC, EtOAc/hexane [1:1]); mp 130

°C (dec.). HPLC 93% (R_t= 8.1 min, 40% CH₃CN in 0.1% TFA water

1

CH₃CN in 0.1% TFA water, 30 min). H NMR (400 MHz, DMSO-

d₆) δ 10.65 (br s, 1H), 10.23 (s, 1H), 8.26−8.24 (m, 1H), 8.02−7.90

(m, 1H), 7.60 (dd, J = 8.1, 2.4 Hz, 2H), 7.56−7.54 (m, 2H), 7.46−

7.39 (m, 3H), 7.33 (d, J = 3.9 Hz, 1H), 7.29 (d, J = 3.9 Hz, 1H), 7.04

(s, 1H). ¹³C NMR (100 MHz, DMSO-d₆) δ 154.95, 150.37, 139.01,

134.22, 133.17, 132.73, 130.38, 130.01, 129.84, 128.47, 126.90, 126.59,

126.49, 125.21, 124.41, 124.17, 123.61. LC-MS (ESI+) 482.04 (M +

H)⁺. HRMS (ESI+) m/z calculated for C₂₁H₁₆N₅O₃S₃(M + H)⁺

482.0410, found 482.0415

1

40 min). H NMR (400 MHz, CD₃CN) δ 8.28 (dd, J = 6.4, 2.8 Hz,

1H), 8.14 (br s, 1H, disappeared on D₂O shake), 7.98 (dd, J = 6.8, 3.5

Hz, 1H), 7.94 (br s, 1H, disappeared on D₂O shake), 7.65 (dd, J = 4.8,

N-(3-(1H-Tetrazol-5-ylthio)-4-hydroxynaphthalen-1-yl)-5-(pyri-

din-2-yl)thiophene-2-sulfonamide (15g). This compound was

1993

dx.doi.org/10.1021/jm201118h | J. Med. Chem. 2012, 55, 1978−1998

Journal of Medicinal Chemistry

Article

prepared using the procedure described for 15d except using 13g (42

mg, 0.1 mmol), to afford the title compound 15g (40 mg, 84.8%, via 2

steps) as an off-white solid; mp 163.2 °C (dec.). HPLC 96% (R_t= 7.9

min, 40% CH₃CN in 0.1% TFA water, 30 min). ¹H NMR (400 MHz,

DMSO-d₆) δ 10.63 (br s, 1H), 10.29 (s, 1H), 8.53 (app. d, J = 4.6 Hz,

1H), 8.23 (dd, J = 6.8, 3.6 Hz, 1H), 7.98 (dd, J = 6.5, 3.2 Hz, 1H), 7.94

(d, J = 8.0 Hz, 1H), 7.87 (td, J = 7.8, 1.6 Hz, 1H), 7.60 (d, J = 4.0 Hz,

1H), 7.54−7.50 (m, 2H), 7.37−7.34 (m, 1H), 7.28 (d, J = 4.0 Hz,

1H), 7.05 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆) δ 154.87, 151.23,

150.88, 150.31, 141.44, 138.20, 134.06, 133.03, 130.29, 128.48, 126.90,

126.47, 125.26, 125.17, 124.51, 124.09, 123.62, 120.02, 106.90. LC-MS

(ESI+) 483.04 (M + H)⁺. HRMS (ESI+) m/z calculated for

C₂₀H₁₅N₆O₃S₃(M + H)⁺483.0362, found 483.0348.

N-(3-(1H-Tetrazol-5-ylthio)-4-hydroxynaphthalen-1-yl)-

naphthalene-2-sulfonamide (15l). This compound was prepared

using the procedure described for 15d except 13e (38 mg, 0.1 mmol)

to afford the title compound 15l (29 mg, 64.9%, via 2 steps) as a gray

solid; mp 173.6 °C (dec.). HPLC 98% (R_t= 5.4 min, 50% CH₃CN in

0.1% TFA water 30 min). ¹H NMR (400 MHz, DMSO-d₆) δ 10.54 (br

s, 1H), 10.06 (s, 1H), 8.19−8.16 (m, 2H), 7.99−7.93 (m, 4H), 7.70

(dd, J = 8.6, 1.5 Hz, 1H), 7.63 (t, J = 7.2 Hz, 1H), 7.55 (t, J = 7.5 Hz,

1H), 7.49−7.43 (m, 2H), 6.88 (s, 1H). LC-MS (ESI+) 450.07 (M +

H)⁺. ¹³C NMR (100 MHz, DMSO-d₆) δ 154.69, 137.30, 134.78,

133.03, 132.10, 130.08, 129.79, 129.77, 129.46, 128.54, 128.43, 128.32,

128.16, 126.82, 126.44, 125.49, 124.29, 123.55, 123.10, 104.99. LC-MS

(ESI+) 450.07 (M + H)⁺. HRMS (ESI+) m/z calculated for

C₂₁H₁₆N₅O₃S₂(M + H)⁺450.0689, found 450.0702.

N-(3-(1H-Tetrazol-5-ylthio)-4-hydroxynaphthalen-1-yl)-4-pentyl-

benzenesulfonamide (15m). This compound was prepared using the

procedure described for 15d except using 13j (40 mg, 0.1 mmol) to

afford the title compound 15m (39 mg, 83.6%, via 2 steps) as a gray

solid; mp 155.6 °C (dec.). HPLC 99% (R_t= 15.3 min, 50% CH₃CN in

0.1% TFA water 40 min). ¹H NMR (400 MHz, DMSO-d₆) δ 10.53 (br

s, 1H), 9.80 (s, 1H), 8.21−8.19 (m, 1H), 7.96−7.94 (m, 1H), 7.56−

7.49 (m, 2H), 7.48 (d, J = 8.3 Hz, 2H), 7.16 (d, J = 8.3 Hz, 2H), 6.76

(s, 1H), 2.54 (t, J = 7.5 Hz, 2H), 1.50 (p, J = 7.5 Hz, 2H), 1.30−1.23

(m, 2H), 1.18−1.11 (m, 2H), 0.83 (t, J = 7.2 Hz, 3H). ¹³C NMR (100

MHz, DMSO-d₆) δ 154.75, 148.33, 137.34, 133.23, 130.26, 129.40,

128.27, 127.62, 126.76, 126.47, 125.63, 124.42, 123.53, 106.51, 35.43,

31.24, 30.77, 22.55, 14.56. LC-MS (ESI+) 470.13 (M + H)⁺. HRMS

(ESI+) m/z calculated for C₂₂H₂₄N₅O₃S₂(M + H)⁺470.1315, found

470.1310.

2-(4-(5-Chlorothiophene-2-sulfonamido)-1-hydroxynaphthalen-

2-ylthio)acetic Acid (15n). This compound was prepared using the

procedure described for 15a using 13k (52 mg, 0.14 mmol) and a

solution of thioglycolic acid (0.14 mL, 1 M solution in THF). The title

compound 15n (32 mg, 54%) was obtained as a white solid; mp 143−

145 °C. HPLC 95% (R_t= 17.1 min, 40% CH₃CN in 0.1% TFA water,

40 min). ¹H NMR (400 MHz, DMSO-d₆) δ 12.77 (br s, 1H), 10.30 (s,

1H), 9.96 (br s, 1H), 8.14 (d, J = 7.7 Hz, 1H), 7.85 (d, J = 8.8 Hz,

1H), 7.50−7.43 (m, 2H), 7.22 (d, J = 4.1 Hz, 1H), 7.12−7.11 (m,

2H), 3.55 (s, 2H). ¹³C NMR (100 MHz, DMSO-d₆) δ 171.78, 153.29,

139.27, 135.68, 132.92, 131.87, 130.16, 128.59, 127.59, 126.59, 125.76,

124.15, 123.69, 123.18, 113.74, 37.42. LC-MS (ESI−) 427.94 (M −

H)⁻. HRMS (ESI+) m/z calculated for C₁₆H₁₂ClNO₅S₃Na (M + Na)⁺

451.9458, found 451.9468.

N-(3-(1H-Tetrazol-5-ylthio)-4-hydroxynaphthalen-1-yl)-4-cyclo-

hexylbenzenesulfonamide (15h). This compound was prepared using

the procedure described for 15d except using 13h (41 mg, 0.1 mmol)

to afford the title compound 15h (22 mg, 46.3%, via 2 steps) as an off-

white solid; mp 169.2 °C (dec.). HPLC 99% (R_t= 14.5 min, 50%

1

CH₃CN in 0.1% TFA water, 40 min). H NMR (400 MHz, DMSO-

d₆) δ 10.64 (br s, 1H), 9.79 (s, 1H), 8.20 (d, J = 8.4 Hz, 1H), 7.93 (d, J

= 8.4 Hz, 1H), 7.54−7.49 (m, 2H), 7.46 (d, J = 8.3 Hz, 2H), 7.20 (d, J

= 8.0 Hz, 2H), 6.71 (s, 1H), 1.76−1.64 (m, 5H), 1.34−1.17 (m, 5H).

¹³C NMR (100 MHz, DMSO-d₆) δ 154.83, 153.32, 137.35, 133.29,

130.33, 128.27, 127.80, 127.72, 126.77, 126.46, 125.63, 124.42, 123.53,

44.19, 34.12, 26.82, 26.11. LC-MS (ESI−) 480.11 (M −H)⁻. HRMS

(ESI+) m/z calculated for C₂₃H₂₄N₅O₃S₂(M + H)⁺482.1315, found

482.1318

N-(3-(1H-Tetrazol-5-ylthio)-4-hydroxynaphthalen-1-yl)-4′-me-

thoxybiphenyl-4-sulfonamide (15i). This compound was prepared

using the procedure described for 15d except using 13i (44 mg, 0.1

mmol) to afford the title compound 15i (42 mg, 82.0%, via 2 steps) as

a white solid; mp 156.8 °C (dec.). HPLC 93% (R_t= 12.0 min, 45%

1

CH₃CN in 0.1% TFA water, 40 min). H NMR (400 MHz, DMSO-

d₆) δ 10.61 (br s, 1H), 9.95 (s, 1H), 8.24−8.21 (m, 1H), 8.02−7.99

(m, 1H), 7.68−7.59 (m, 4H), 7.55−7.52 (m, 2H), 7.03 (d, J = 9.2 Hz,

2H), 6.87 (s, 1H), 3.79 (s, 3H). ¹³C NMR (100 MHz, DMSO-d₆) δ

160.39, 154.61, 144.43, 138.15, 133.08, 131.26, 129.91, 128.90, 128.34,

128.18, 127.04, 126.86, 126.50, 125.64, 124.40, 123.55, 115.20, 106.77,

55.95. LC-MS (ESI+) 506.10 (M + H)⁺. HRMS (ESI+) m/z

calculated for C₂₄H₂₀N₅O₄S₂(M + H)⁺506.0951, found 506.0936.

N-(3-(1H-Tetrazol-5-ylthio)-4-hydroxynaphthalen-1-yl)-4′-fluoro-

biphenyl-4-sulfonamide (15j). This compound was prepared using

the procedure described for 15d except using 13f (43 mg, 0.1 mmol)

to afford the title compound 15j (40 mg, 81.8%, via 2 steps) as a white

solid; mp 168.1 °C (dec.). HPLC 95% (R_t= 13.7 min, 45% CH₃CN in

0.1% TFA water 30 min). ¹H NMR (400 MHz, DMSO-d₆) δ 10.56 (br

s, 1H), 9.99 (s, 1H), 8.24−8.22 (m, 1H), 8.02−8.00 (m, 1H), 7.71−

7.64 (m, 6H), 7.55−7.52 (m, 2H), 7.32 (t, J = 8.9 Hz, 2H), 6.85(s,

1H). ¹⁹F NMR (376 MHz, DMSO-d₆) δ −114.25 (m). ¹³C NMR (100

MHz, DMSO-d₆) δ 163.13 (d, J = 245 Hz), 154.57, 143.72, 138.96,

135.57, 133.05, 129.85, 129.84 (d, J = 8 Hz), 128.35, 128.21, 127.74,

126.88, 126.51, 125.57, 124.39, 123.54, 116.63 (d, J = 21 Hz), 106.90.

LC-MS (ESI+) 494.07 (M + H)⁺. HRMS (ESI+) m/z calculated for

C₂₃H₁₇FN₅O₃S₂(M + H)⁺494.0751, found 494.0739.

N-(3-(1H-Tetrazol-5-ylthio)-4-hydroxynaphthalen-1-yl)-4-phe-

noxybenzenesulfonamide (15k). This compound was prepared using

the procedure described for 15d except using 13d (42 mg, 0.1 mmol)

to afford the title compound 15k (22 mg, 45.1%, via 2 steps) as a

white solid; mp 172.5 °C (dec.). HPLC 99% (R_t= 8.2 min, 50%

CH₃CN in 0.1% TFA water 30 min). ¹H NMR (400 MHz, DMSO-d₆)

δ 10.58 (br s, 1H, disappeared on D₂O shake), 9.88 (s, 1H,

disappeared on D₂O shake), 8.22−8.20 (m, 1H), 7.94−7.92 (m, 1H),

7.53 (d, J = 8.8 Hz, 4H), 7.41 (t, J = 7.6 Hz, 2H), 7.21 (t, J = 7.2 Hz,

1H), 6.98 (d, J = 7.6 Hz, 2H), 6.92 (d, J = 8.8 Hz, 2H), 6.83 (s, 1H).

¹³C NMR (100 MHz, DMSO-d₆) δ 161.03, 155.79, 154.58, 134.15,

2-(4-(Biphenyl-4-ylsulfonamido)-1-hydroxynaphthalen-2-ylthio)-

acetic Acid (15o). This compound was prepared using the procedure

described for 15a using 13b (50 mg, 0.12 mmol) and a solution of

thioglycolic acid (0.12 mL, 1 M solution in THF). The title compound

15o (19 mg, 40%) was obtained as a gray solid; mp 170 °C (dec.).

HPLC 97% (R_t= 10.44 min, 50% CH₃CN in 0.1% TFA water 20

1

min). H NMR (400 MHz, DMSO-d₆) δ 12.78 (br s, 1H), 9.95 (s,

1H), 8.11 (d, J = 8.0 Hz, 1H), 7.85 (d, J = 7.6 Hz, 1H), 7.76 (d, J = 8.4

Hz, 2H), 7.68−7.65 (m, 4H), 7.548−7.39 (m, 5H), 7.00 (s, 1H), 5.73

(br s, 1H), 3.46 (s, 2H). ¹³C NMR (100 MHz, DMSO-d₆) δ 171.73,

152.91, 144.78, 139.23, 139.14, 131.89, 129.77, 129.17, 128.25, 127.87,

127.71, 127.28, 126.41, 125.79, 124.79, 124.13, 123.09, 113.72, 37.44.

LC-MS (ESI+) 464.07 (M + H)⁺. HRMS (ESI−) m/z calculated for

C₂₄H₁₈NO₅S₂(M − H)⁻464.0632, found 464.0638.

tert-Butyl 2-(4-(thiophene-2-sulfonamido)naphthalen-1-yloxy)-

acetate (16a). The compound 3 (61 mg, 0.2 mmol) was dissolved

in DMF (1 mL) and added tert-butyl bromoacetate (0.060 mL, 0.4

mmol), followed by DBU (0.4 mL, 1 M solution in NMP) and

catalytic amount of KI. The reaction mixture was heated using a

microwave reactor at 90 °C for 20 min. The TLC analysis (EtOAc/

hexane [1:2]) showed the presence of starting material. To drive the

reaction to completion, additional tert-butyl bromoacetate (13.5 equiv,

0.4 mL, 2.7 mmol) was added, and the reaction was continued at 90

°C for further 30 min. The resulting mixture was diluted with ethyl

acetate (40 mL) and washed with NaHSO₄(10 mL × 2, 0.5 M), water

(10 mL × 6) and brine (10 mL). The organic phase was dried

(Na₂SO₄) and concentrated. The solid obtained was purified via SiO₂

133.06, 130.99, 130.21, 130.09, 128.30, 126.81, 126.48, 125.57, 125.36,

124.35, 123.54, 120.31, 118.45, 106.87. LC-MS (ESI+) 492.07 (M +

H)⁺. HRMS (ESI+) m/z calculated for C₂₃H₁₈N₅O₄S₂(M + H)⁺

492.0795, found 492.0805

1994

dx.doi.org/10.1021/jm201118h | J. Med. Chem. 2012, 55, 1978−1998

Journal of Medicinal Chemistry

Article

chromatography (hexane/EtOAc, gradient elution) to afford 16a (43

mg, 51.3%) as a gray solid. R_f= 0.27 (TLC, EtOAc/hexane [1:2]); mp

128.6 °C (dec.). H NMR (400 MHz, CDCl₃) δ 7.85 (d, J = 7.6 Hz,

(m, 1H), 7.66−7.62 (m, 1H), 7.30 (d, J = 8.4 Hz, 1H), 3.53 (s, 6H).

¹³C NMR (100 MHz, CDCl₃) δ 186.71, 154.44, 144.13, 130.11,

128.49, 127.95, 126.84, 124.77, 123.93, 122.62, 118.66, 43.77, 39.35.

LC-MS (ESI+) 277.07 (M + H)⁺. HRMS (ESI+) m/z calculated for

C₁₃H₁₃N₂O₃S (M + H)⁺277.0641, found 277.0637.

1

1H), 7.80 (dd, J = 7.6, 1.2 Hz, 1H), 7.61 (dd, J = 4.8, 1.2 Hz, 1H), 7.56

(dd, J = 3.6, 1.2 Hz, 1H), 7.46−7.36 (m, 2H), 7.16 (d, J = 8.4 Hz, 1H),

6.99 (dd, J = 5.0, 3.8 Hz, 1H), 6.31 (d, J = 8.4 Hz, 1H), 3.92 (s, 2H),

1.52 (s, 9H). LC-MS (ESI+) 420.09 (M + H)⁺. HRMS (ESI+) m/z

calculated for C₂₀H₂₂NO₅S₂(M + H)⁺420.0934, found 420.0932.

Methyl 4-(4-(Thiophene-2-sulfonamido)naphthalen-1-yloxy)-

butanoate (16b). This compound was synthesized according to the

procedure described for 16a except using 15 equiv of ethyl

bromobutanoate (0.44 mL, 3 mmol), and the reaction mixture was

heated using a microwave reactor at 90 °C for 30 min. The TLC

analysis indicated presence of starting material, and additional 30 min

at 90 °C was required to complete the reaction. The crude solid 16b

was purified (SiO₂chromatography, hexane/EtOAc gradient elution)

to afford 16b (43 mg, 51.3%) as a brown oil. The baseline impurities

were still observed after SiO₂purification. This product was used in

the next step without further purification. R_f= 0.36 (TLC, EtOAc/

S-4-Nitronaphthalen-1-yl Dimethylcarbamothioate (20). The

intermediate 19 (276 mg, 1 mmol) was dissolved in NMP (2 mL),

and the solution was heated to 180 °C in a microwave reactor for 20

min. The reaction mixture was diluted with ethyl acetate (50 mL) and

washed with water and brine. The organic phase was dried (Na₂SO₄),

concentrated, and the crude product obtained was purified using

chromatography (10 g silica gel, hexane/EtOAc gradient elution) to

afford compound 20 as a brown solid (198 mg, 71.5%). R_f= 0.38

(TLC, EtOAc/hexane [1:2]); mp 91.2 °C (dec.). ¹H NMR (400 MHz,

CDCl₃) δ 8.50−8.46 (m, 2H), 8.13 (d, J = 7.9 Hz, 1H), 7.87 (d, J = 7.9

Hz, 2H), 7.77−7.64 (m, 1H), 3.24 (s, 3H), 3.03 (s, 3H). ¹³C NMR

(100 MHz, CDCl₃) δ 165.00, 148.27, 136.12, 134.33, 134.22, 129.61,

128.46, 126.75, 125.69, 123.66, 122.83, 37.41. LC-MS (ESI+) 277.07

(M + H)⁺. HRMS (ESI+) m/z calculated for C₁₃H₁₃N₂O₃S (M + H)⁺

277.0641, found 277.0642.

1

hexane = 1:2). H NMR (400 MHz, CDCl₃) δ 7.82−7.80 (m, 1H),

7.78−7.75 (m, 1H), 7.62 (dd, J = 5.2, 1.6 Hz, 1H), 7.58 (dd, J = 4.0,

1.2 Hz, 1H), 7.42−7.36 (m, 2H), 7.13 (d, J = 8.4 Hz, 1H), 7.00 (dd, J

= 4.8, 4.0 Hz, 1H), 6.44 (d, J = 8.4 Hz, 1H), 4.15 (q, J = 7.1 Hz, 2H),

3.31 (t, J = 6.7 Hz, 2H), 2.52 (t, J = 6.8 Hz, 2H), 2.11 (p, J = 6.7 Hz,

2H), 1.25 (t, J = 7.1 Hz, 3H).

2-(4-Nitronaphthalen-1-ylthio)acetic Acid (21). The intermediate

20 (97 mg, 0.35 mmol) was suspended in methanol (1 mL) under

argon atmosphere and added KOH (1.4 mL, 1 M solution in

CH₃OH). The reaction mixture was stirred at room temperature for

12 h, affording a homogeneous solution. The tert-butyl bromoacetate

(0.103 mL, 0.7 mmol) was added, and stirring was continued for 12 h.

The reaction mixture was concentrated, and the residue was dissolved

in water and acidified (pH = 1−2) using solid NaHSO₄. The yellow

precipitate obtained was filtered, washed with water, and air-dried to

obtain a yellow solid, (79 mg, 85.6%, via 2 steps). R_f= 0.18 (TLC,

CH₃OH/DCM/HOAc [1:20:0.1]); mp 144.9 °C (dec.). ¹H NMR

(400 MHz, CDCl₃) δ 8.57 (d, J = 8.8 Hz, 1H), 8.40 (d, J = 8.8 Hz,

1H), 8.18 (d, J = 8.1 Hz, 1H), 7.77−7.73 (m, 1H), 7.69−7.65 (m,

1H), 7.52 (d, J = 8.4 Hz, 1H), 3.91 (s, 2H). ¹³C NMR (100 MHz,

CDCl₃) δ 170.63, 144.42, 143.51, 131.71, 129.92, 127.67, 125.31,

124.74, 124.16, 124.00, 121.35, 35.19. LC-MS (ESI−) 218.03 (M −

H−CO₂)⁻. HRMS (ESI−) m/z calculated for C₁₂H₈NO₄S (M − H)⁻

262.0179, found 262.0179.

2-(4-(Thiophene-2-sulfonamido)naphthalen-1-yloxy)acetic Acid

(17a). The 16a was dissolved in dioxane (1 mL) and added conc

HCl (1 mL, 32%). The mixture was stirred at room temperature for 1

h (TLC analysis EtOAc/hexane [1:2] indicated completion of the

reaction) and concentrated. The residue was suspended in DCM/

hexane (1:1, 2 mL) and left in a refrigerator (overnight). The

precipitate was collected by filtration and washed with DCM/hexane

(1:1, 3 mL), affording 17a (21.4 mg, 82.3%) as a gray solid. R_f= 0.33

(TLC, CH₃OH/DCM [1:20]); mp 148.9 °C (dec.). HPLC 98% (R_t=

1

6.19 min, 50% CH₃CN in 0.1% TFA water 20 min). H NMR (400

MHz, DMSO-d₆) δ 12.64 (br s, 1H), 8.14−8.13 (m, 1H), 8.11 (dd, J =

5.2, 1.4 Hz, 1H), 7.78 (dd, J = 3.8, 1.4 Hz, 1H), 7.66−7.63 (m, 1H),

7.46−7.43 (m, 2H), 7.19 (dd, J = 4.8, 3.6 Hz, 1H), 7.01 (d, J = 8.5 Hz,

1H), 6.80 (br s, 1H), 6.23 (d, J = 8.4 Hz, 1H), 3.96 (s, 2H). ¹³C NMR

(100 MHz, DMSO-d₆) δ 172.94, 143.97, 137.63, 136.87, 135.95,

134.32, 129.07, 127.88, 127.43, 125.75, 123.72, 122.55, 121.54, 120.25,

101.97, 45.39. LC-MS (ESI−) 362.01 (M − H)⁻.; HRMS (ESI− ) m/

z calculated for C₁₆H₁₂NO₅S₂(M − H)⁻362.0162, found 362.0174.

4-(4-(Thiophene-2-sulfonamido)naphthalen-1-yloxy)butanoic

Acid (17b). This compound was synthesized using the procedure

described for 17a except using 16b (43 mg, 0.1 mmol), dioxane (2

mL), and conc HCl (4 mL, 32%). The required product 17b (23 mg,

56.6%) was obtained as a brown greasy solid. R_f= 0.09 (TLC,

CH₃OH/DCM [1:20]). HPLC 97% (R_t= 7.43 min, 50% CH₃CN in

0.1% TFA water 20 min). ¹H NMR (400 MHz, DMSO-d₆) δ 12.11 (br

s, 1H), 8.18−8.15 (m, 1H), 8.10 (dd, J = 4.8, 1.2 Hz, 1H), 7.77 (dd, J

= 2.8, 0.8 Hz, 1H), 7.64−7.62 (m, 1H), 7.42−7.40 (m, 2H), 7.18 (t, J

= 4.0 Hz, 1H), 6.99 (d, J = 8.4 Hz, 1H), 6.42−6.39 (m, 2H), 3.20−

3.17 (m, 2H), 2.36 (t, J = 7.2 Hz, 2H), 1.92−1.85 (m, 2H). ¹³C NMR

(100 MHz, DMSO-d₆) δ 175.19, 144.40, 137.55, 136.84, 135.46,

134.32, 129.02, 127.94, 127.30, 125.42, 123.75, 122.75, 121.45, 120.37,

101.52, 43.20, 32.04, 24.05. LC-MS (ESI−) 390.05 (M − H)⁻. HRMS

(ESI−) m/z calculated for C₁₈H₁₆NO₅S₂(M − H)⁻390.0475, found

390.0476.

2-(4-Aminonaphthalen-1-ylthio)acetic Acid (22). The intermedi-

ate 21 (70 mg, 0.27 mmol) was dissolved in methanol (50 mL) and

the solution was passed through the H-cube hydrogenator (10% Pd−

C cat. cartridge, 1.0 mL/min., 25 °C, 40 bar) to obtain a slightly brown

color solution. The solution was concentrated to dryness to afford the

required product 22 (70 mg, 100%) as a gray solid. R_f= 0.40 (TLC,

1

CH₃OH/DCM [1:10]); mp 138.9 °C (dec.). H NMR (400 MHz,

CD₃OD) δ 8.48 (d, J = 8.4 Hz, 1H), 8.01 (d, J = 8.5 Hz, 1H), 7.59 (d,

J = 8.0, 1H), 7.55−7.51 (m, 1H), 7.46−7.42 (m, 1H), 6.71 (d, J = 7.6

Hz, 1H), 3.42 (s, 2H). ¹³C NMR (100 MHz, CD₃OD) δ 172.73,

146.04, 135.53, 135.20, 126.58, 125.77, 124.47, 124.40, 122.33, 117.42,

108.43, 38.58. LC-MS (ESI−) 188.05 (M − H−CO₂)⁻. HRMS

(ESI−) m/z calculated for C₁₂H₁₀NO₂S (M − H)⁻232.0438, found

232.0435.

2-(4-(Thiophene-2-sulfonamido)naphthalen-1-ylthio)acetic Acid

(23). The compound 22 (33 mg, 0.14 mmol) was dissolved in THF (1

mL), and pyridine (0.28 mL, 0.5 M solution in THF) was added at 0

°C, followed by water (0.5 mL). Thiophene-2-sulfonyl chloride (26

mg in 1 mL THF) was added dropwise, followed by additional

pyridine (0.28 mL 0.5 M solution in THF). The resulting solution was

stirred vigorously at 0 °C and slowly warmed to room temperature.

After 4 h, the organic phase was removed and the aqueous portion was

diluted with water (10 mL) and acidified (pH = 2−3) at 0 °C using

NaHSO₄solution (0.5 M). The mixture was extracted with ethyl

acetate. The organic phase was washed with water and brine, dried

(Na₂SO₄), and concentrated. The crude product obtained was purified

using chromatography (SiO₂, DCM/CH₃OH [20:1]) to afford 23 (31

mg, 58.4%) as a gray solid. R_f= 0.17 (TLC, CH₃OH/DCM/HOAc

[1:20:0.1]); mp 159.8 °C (dec.). HPLC 99% (R_t= 4.43 min, 50%

CH₃CN in 0.1% TFA water 20 min). ¹H NMR (400 MHz, CD₃CN) δ

8.36 (d, J = 8.4 Hz, 1H), 7.99 (d, J = 8.4 Hz, 1H), 7.68 (dd, J = 4.8, 1.3

Hz, 1H), 7.64−7.60 (m, 1H), 7.57−7.51 (m, 2H), 7.43 (dd, J = 3.6,

O-4-Nitronaphthalen-1-yl Dimethylcarbamothioate (19). The 4-

nitro-1-naphthol (378 mg, 2 mmol) was dissolved in NMP (2 mL)

and added K₂CO₃(276 mg, 2 mmol). The mixture was heated to 50

°C and a solution of N,N-dimethylthiocarbamoyl chloride (260 mg,

2.1 mmol) was added in NMP (1 mL) dropwise over 5 min. The

resulting solution was stirred at 50 °C for 2 h and quenched with water

(30 mL) at 50 °C. The brown precipitate obtained was filtered and

washed with water and dried to obtain intermediate 19 (496 mg,

89.8%) as a dark-brown solid. R_f= 0.40 (TLC, EtOAc/hexane [1:2]);

1

mp 110.4 °C (dec.). H NMR (400 MHz, CDCl₃) δ 8.67 (d, J = 8.8

Hz, 1H), 8.33 (d, J = 8.4 Hz, 1H), 7.96 (d, J = 8.0 Hz, 1H), 7.77−7.72

1995

dx.doi.org/10.1021/jm201118h | J. Med. Chem. 2012, 55, 1978−1998

Journal of Medicinal Chemistry

Article

1.2 Hz, 1H), 7.28 (d, J = 7.6 Hz, 1H), 7.04 (dd, J = 5.2, 4.0 Hz, 1H),

3.78 (s, 2H). LC-MS (ESI−) 378.00 (M − H)⁻. HRMS (ESI−) m/z

calculated for C₁₆H₁₂NO₄S₃(M − H)⁻377.9934, found 377.9937.

2-(1-Hydroxy-4-(thiophene-2-sulfonamido)naphthalen-2-ylthio)-

benzoic Acid (24). This compound was prepared using the procedure

described for 15a except using thiosalicylic acid (15 mg, 0.1 mmol).

The title compound 24 (19 mg, 99%) was obtained as a white solid;

mp 215 °C (dec.). HPLC 91% (R_t= 18.9 min, 40% CH₃CN in 0.1%

127.57, 127.48, 126.48, 126.25, 125.23, 124.13, 123.16, 44.22, 34.18,

26.83, 26.12. LC-MS (ESI+) 481.15 (M + H)⁺. HRMS (ESI+) m/z

calculated for C₂₄H₂₅N₄O₃S₂(M + H)⁺481.1363, found 481.1371.

N-(3-(1H-1,2,4-Triazol-3-ylthio)-4-hydroxynaphthalen-1-yl)-4-

phenoxybenzenesulfonamide (29). This compound was prepared

using the procedure described for 15d except using 13d (78 mg, 0.2

mmol) and 1H-1,2,4-triazole-3-thiol (20 mg, 0.2 mmol). The title

compound 29 (36 mg, 56.5%, via 2 steps) was obtained as an off-white

solid; mp 176.1 °C (dec.). HPLC 99% (R_t= 23.2 min, 40% CH₃CN in

1

TFA water, 40 min). H NMR (400 MHz, DMSO-d₆) δ 13.15 (br s,

1

1H), 10.09 (s, 1H), 8.19 (d, J = 8.0 Hz, 1H), 8.01 (d, J = 7.6 Hz, 1H),

7.92 (d, J = 8.0 Hz, 1H), 7.76 (d, J = 4.8 Hz, 1H), 7.58−7.50 (m, 2H),

7.34−7.31 (m, 2H), 7.17 (t, 7.2 Hz, 1H), 6.91 (s, 2H), 6.47 (d, J = 8.8

Hz, 1H). ¹³C NMR (100 MHz, DMSO-d₆) δ 168.15, 156.08, 141.87,

140.39, 133.88, 133.34, 133.21, 133.17, 132.65, 131.78, 128.38, 128.17,

126.70, 126.58, 126.18, 125.15, 125.06, 124.21, 123.69, 109.66, 104.98.

LC-MS (ESI+) 475.05 (M + NH₄)⁺. HRMS (ESI+) m/z calculated for

C₂₁H₁₅NO₅S₃Na (M + Na)⁺480.0005, found 479.9992.

0.1% TFA water, 40 min). H NMR (400 MHz, DMSO-d₆) δ 10.12

(br s, 1H, disappeared on D₂O shake), 9.78 (s, 1H, disappeared on

D₂O shake), 8.53 (br s, 1H), 8.10 (d, J = 8.0 Hz, 1H), 7.83 (d, J = 8.1

Hz, 1H), 7.49 (d, J = 8.8 Hz, 2H), 7.46−7.35 (m, 4H), 7.18−7.14 (m,

1H), 6.95 (appd, J = 7.7 Hz, 2H), 6.90 (d, J = 8.8 Hz, 2H), 6.82 (br s,

1H). ¹³C NMR (100 MHz, DMSO-d₆) δ 160.92, 155.92, 152.67,

134.42, 132.11, 130.99, 130.01, 129.74, 127.56, 126.53, 126.29, 125.28,

125.13, 124.15, 123.18, 120.23, 118.60, 104.99. LC-MS (ESI+) 491.09

(M + H)⁺. HRMS (ESI+) m/z calculated for C₂₄H₁₉N₄O₄S₂(M + H)⁺

491.0842, found 491.0847.

N-(3-(1H-1,2,4-Triazol-3-ylthio)-4-hydroxynaphthalen-1-yl)-3,4-

dichlorobenzenesulfonamide (25). This compound was prepared

using the procedure described for 15d except using 13b (82 mg, 0.2

mmol) and 1H-1,2,4-triazole-3-thiol (24 mg, 0.24 mmol). The title

compound 25 (23 mg, 91.3%, via 2 steps) was obtained as a white

solid. HPLC 98% (R_t= 21.0 min, 40% CH₃CN in 0.1% TFA water, 40

N-(3-(1H-1,2,4-Triazol-3-ylthio)-4-hydroxynaphthalen-1-yl)-4′-

(trifluoromethyl)biphenyl-4-sulfonamide (30). This compound was

prepared using the procedure described for 15d except using 13l (95

mg, 0.2 mmol) and 1H-1,2,4-triazole-3-thiol (20 mg, 0.2 mmol). The

title compound 30 (31 mg, 79.2%, via 2 steps) was obtained as an off-

white solid; mp 193.8 °C (dec.). HPLC 95% (R_t= 13.7 min, 50%

1

min); mp 154.8 °C (dec.). H NMR (400 MHz, DMSO-d₆) δ 10.17

(br s, 1H), 9.95 (s, 1H), 8.55 (br s, 1H), 8.145 (d, J = 7.6 Hz, 1H),

7.91 (d, J = 7.6 Hz, 1H), 7.71 (d, J = 8.4 Hz, 2H), 7.68−7.58 (m, 4H),

7.50−7.39 (m, 5H), 6.94 (br s, 1H). ¹³C NMR (100 MHz, DMSO-d₆)

δ 152.68, 144.69, 139.25, 139.08, 132.05, 129.79, 129.39, 129.18,

128.11, 127.77, 127.70, 127.59, 126.58, 126.30, 125.15, 124.15, 123.19.

LC-MS (ESI+) 475.09 (M + H)⁺. HRMS (ESI+) m/z calculated for

C₂₄H₁₉N₄O₃S₂(M + H)⁺475.0893, found 475.0898.

1

CH₃CN in 0.1% TFA water, 40 min). H NMR (400 MHz, DMSO-

d₆) δ 10.18 (br s, 1H), 9.97 (s, 1H), 8.48 (br s, 1H), 8.12 (d, J = 7.9

Hz, 1H), 7.90−7.79 (m, 5H), 7.76 (d, J = 8.4 Hz, 2H), 7.64 (d, J = 8

Hz, 2H), 7.44−7.41 (m 2H), 6.86 (s, 1H). ¹⁹F NMR (376 MHz,

DMSO-d₆) δ −61.44 (s). LC-MS (ESI+) 543.08 (M + H)⁺. HRMS

(ESI + ve) m/z calculated for C₂₅H₁₈F₃N₄O₃S₂(M + H)⁺543.0767,

found 543.0781.

N-(3-(1H-1,2,4-Triazol-3-ylthio)-4-hydroxynaphthalen-1-yl)-5-

phenylthiophene-2-sulfonamide (26). This compound was prepared

using the procedure described for 15d except using 13c (83 mg, 0.2

mmol) and 1H-1,2,4-triazole-3-thiol (20 mg, 0.2 mmol). The title

compound 26 (12 mg, 43.0%, via 2 steps) was obtained as a gray solid;

mp 172.9 °C (dec.). HPLC 95% (R_t= 20.1 min, 40% CH₃CN in 0.1%

N-(3-(1H-1,2,4-Triazol-3-ylthio)-4-hydroxynaphthalen-1-yl)-5-

(phenylsulfonyl)thiophene-2-sulfonamide (31). This compound was

prepared using the procedure described for 15d except using N-(3-

chloro-4-oxonaphthalen-1(4H)-ylidene)-5-(phenylsulfonyl)thiophene-

2-sulfonamide (13m) (96 mg, 0.2 mmol) and 1H-1,2,4-triazole-3-thiol

(20 mg, 0.2 mmol). The title compound 31 (36 mg, 68.9%, via 2

steps) was obtained as an off-white solid; mp 153.3 °C (dec.). HPLC

1

TFA water, 40 min). H NMR (400 MHz, DMSO-d₆) δ 10.17 (br s,

2H), 8.52 (br s, 1H), 8.17 (d, J = 8.8 Hz, 1H), 7.94 (d, J = 8.8 Hz,

1H), 7.62 (appd, J = 7.2 Hz, 2H), 7.50−7.39 (m, 6H), 7.29 (d, J = 4.0

Hz, 1H), 7.04 (br s, 1H). ¹³C NMR (100 MHz, DMSO-d₆) δ 152.94,

150.22, 139.29, 134.02, 132.78, 132.25, 130.04, 129.82, 129.73, 127.73,

126.66, 126.58, 126.31, 124.83, 124.48, 124.03, 123.23, 111.15. LC-MS

(ESI+) 481.05 (M + H)⁺. HRMS (ESI+) m/z calculated for

C₂₂H₁₇N₄O₃S₃(M + H)⁺481.0457, found 481.0456.

N-(3-(1H-1,2,4-Triazol-3-ylthio)-4-hydroxynaphthalen-1-yl)-4′-

fluorobiphenyl-4-sulfonamide (27). This compound was prepared

using the procedure described for 15d except using 13f (85 mg, 0.2

mmol) and 1H-1,2,4-triazole-3-thiol (20 mg, 0.2 mmol). The title

compound 27 (29 mg, 38.1%, via 2 steps) was obtained as an off-white

solid; mp 194.1 °C (dec.). HPLC 97% (R_t= 24.2 min, 40% CH₃CN in

0.1% TFA water, 40 min). ¹H NMR (400 MHz, DMSO-d₆) δ 9.92 (s,

1H), 8.51 (br s, 1H), 8.13 (d, J = 7.6 Hz, 1H), 7.90 (d, J = 8.0 Hz,

1H), 7.70−7.67 (m, 4H), 7.61 (d, J = 8.6 Hz, 2H), 7.45−7.42 (m,

2H), 7.30 (t, J = 8.8 Hz, 2H), 6.88 (br s, 1H). ¹³C NMR (100 MHz,

DMSO-d₆) δ 163.12 (d, J = 244.3 Hz), 145.75, 143.61, 139.26, 135.56,

129.84 (d, J = 8.3 Hz), 128.12, 127.72, 127.54, 126.56, 126.29, 125.04,

124.14, 123.18, 116.64 (d, J = 21.4 Hz). ¹⁹F NMR (376 MHz, CDCl₃)

δ −114.28 (m). LC-MS (ESI+) 493.09 (M + H)⁺.

N-(3-(1H-1,2,4-Triazol-3-ylthio)-4-hydroxynaphthalen-1-yl)-4-cy-

clohexylbenzenesulfonamide (28). This compound was prepared

using the procedure described for 15d except using 13h (83 mg, 0.2

mmol) and 1H-1,2,4-triazole-3-thiol (20 mg, 0.2 mmol). The title

compound 28 (40 mg, 68.0%, via 2 steps) was obtained as an off-white

solid; mp 154.7 °C (dec.). HPLC 95% (R_t= 14.6 min, 50% CH₃CN in

0.1% TFA water 40 min). ¹H NMR (400 MHz, DMSO-d₆) δ 10.18 (br

s, 1H), 9.77 (s, 1H), 8.59 (br s, 1H), 8.14 (d, J = 8.4 Hz, 1H), 7.84 (d,

J = 8.4 Hz, 1H), 7.48−7.39 (m, 4H), 7.24 (d, J = 8.4, 2H), 6.84 (br s,

1H), 1.76−1.67 (m, 5H), 1.35−1.30 (m, 5H), 1.25−1.20 (m, 1H). ¹³C

NMR (100 MHz, DMSO-d₆) δ 153.21, 137.76, 132.17, 129.70, 127.86,

1

98% (R_t= 11.5 min, 40% CH₃CN in 0.1% TFA water 40 min). H

NMR (400 MHz, DMSO-d₆) δ 10.52 (s, 1H), 10.33 (br s, 1H), 8.46

(br s, 1H), 8.12 (d, J = 8.4 Hz, 1H), 7.89 (d, J = 7.6 Hz, 2H), 7.74 (d, J

= 7.6 Hz, 1H), 7.69 (d, J = 4.0 Hz, 1H), 7.64 (t, J = 7.6 Hz, 3H), 7.40

(t, J = 7.2 Hz, 1H), 7.29 (d, J = 4.4 Hz, 1H), 7.17 (t, J = 7.6 Hz, 1H),

6.99 (s, 1H), approximately 5% baseline impurity was observed. ¹³C

NMR (100 MHz, DMSO-d₆) δ 153.26, 148.25, 147.60, 145.27, 140.93,

140.66, 135.23, 134.43, 133.19, 131.81, 130.76, 130.38, 127.87, 127.70,

126.71, 126.21, 123.81, 123.32, 123.24. LC-MS (ESI+) 545.00 (M +

H)⁺. HRMS (ESI+) m/z calculated for C₂₂H₁₇N₄O₅S₄(M + H)⁺

545.0076, found 545.0096.

N-(3-(1H-1,2,4-Triazol-3-ylthio)-4-hydroxynaphthalen-1-yl)-1-

(phenylsulfonyl)-1H-pyrrole-3-sulfonamide (32). This compound

was prepared using the procedure described for 15d except using N-

(3-chloro-4-oxonaphthalen-1(4H)-ylidene)-1-(phenylsulfonyl)-1H-

pyrrole-3-sulfonamide (13n) (92 mg, 0.2 mmol) and 1H-1,2,4-

triazole-3-thiol (20 mg, 0.2 mmol). The title compound 32 (34 mg,

75.2%, via 2 steps) was obtained as an off-white solid; mp 157.1 °C

(dec.). HPLC 99.8% (R_t= 9.8 min, 50% CH₃CN in 0.1% TFA water

40 min). ¹H NMR (400 MHz, DMSO-d₆) δ 10.19 (br s, 1H), 9.81 (s,

1H), 8.47 (br s, 1H), 8.11 (d, J = 8.3 Hz, 1H), 7.92 (d, J = 7.5 Hz,

2H), 7.81 (d, J = 8.5 Hz, 1H), 7.75 (t, J = 7.5 Hz, 1H), 7.59 (t, J = 7.9

Hz, 2H), 7.53−7.52 (m, 1H), 7.44−7.36 (m, 3H), 7.30 (t, J = 7.3 Hz,

1H), 6.79 (s, 1H), 6.36 (dd, J = 3.3, 1.6 Hz, 1H), approximately 5%

baseline impurity was observed. ¹³C NMR (100 MHz, DMSO-d₆) δ

171.01, 152.65, 137.54, 136.00, 131.87, 130.77, 129.37, 128.83, 127.84,

127.80, 127.44, 126.53, 126.21, 124.98, 123.99, 123.43, 123.21, 123.17,

112.26. LC-MS (ESI+) 528.05 (M + H)⁺. HRMS (ESI+) m/z

calculated for C₂₂H₁₈N₅O₅S₃(M + H)⁺528.0465, found 528.0476.

N-(3-(1H-1,2,4-Triazol-3-ylthio)-4-hydroxynaphthalen-1-yl)-3,4-

dichlorobenzenesulfonamide (33). This compound was prepared

1996

dx.doi.org/10.1021/jm201118h | J. Med. Chem. 2012, 55, 1978−1998

Journal of Medicinal Chemistry

Article

using the procedure described for 15d except using 13e (76 mg, 0.2

mmol) and 1H-1,2,4-triazole-3-thiol (20 mg, 0.2 mmol). The title

compound 33 (71 mg, 78.9%, 2 steps) was obtained as a white solid;

mp 183.2 °C (dec.). HPLC 99.9% (R_t= 21.9 min, 35% CH₃CN in

0.1% TFA water 40 min). ¹H NMR (400 MHz, DMSO-d₆) δ 10.02 (br

s, 1H), 8.30 (br s, 1H), 8.17 (appd, J = 1.3 Hz, 1H), 8.12 (d, J = 8.0

Hz, 1H), 8.00−7.93 (m, 5H), 7.70−7.63 (m, 2H), 7.59 (appt, J = 7.6

Hz, 1H), 7.45−7.37 (m, 2H), 6.87 (s, 1H). ¹³C NMR (100 MHz,

DMSO-d₆) δ 137.61, 134.79, 132.15, 132.03, 129.85, 129.79, 129.41,

129.23, 128.45, 128.37, 128.15, 127.50, 126.55, 126.28, 125.13, 124.18,

123.12, 123.06. LC-MS (ESI+) 449.08 (M + H)⁺. HRMS (ESI+) m/z

calculated for C₂₂H₁₇N₄O₃S₂(M + H)⁺449.0737, found 449.0746.

N-(3-(1H-1,2,4-Triazol-3-ylthio)-4-hydroxynaphthalen-1-yl)-

naphthalene-1-sulfonamide (34). This compound was prepared

according to the procedure for 15d using N-(3-chloro-4-oxonaph-

thalen-1(4H)-ylidene)naphthalene-1-sulfonamide (13o) (76 mg, 0.2

mmol) and 1H-1,2,4-triazole-3-thiol (20 mg, 0.2 mmol). The title

compound 34 (29 mg, 74.5%, via 2 steps) was obtained as a white

solid; mp 158.1 °C (dec.). HPLC 98% (R_t= 10.6 min, 40% CH₃CN in

0.1% TFA water, 40 min). ¹H NMR (400 MHz, DMSO-d₆) δ 10.24 (s,

1H), 10.10 (br s, 1H), 8.73 (d, J = 8.4 Hz, 1H), 8.50 (br s, 1H), 8.11

(d, J = 8.0 Hz, 1H), 8.07 (d, J = 8.4 Hz, 1H), 8.03 (d, J = 7.6 Hz, 1H),

7.83−7.782 (m, 2H), 7.69−7.61 (m, 2H), 7.44−7.38 (m, 2H), 7.26 (t,

J = 7.2 Hz, 1H), 6.74 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆) δ

152.14, 135.53, 134.70, 134.34, 131.79, 130.06, 129.64, 128.88, 128.49,

128.24, 127.46, 127.27, 126.50, 126.16, 125.33, 124.96, 123.88, 123.04.

LC-MS (ESI+) 449.08 (M + H)⁺. HRMS (ESI+) m/z calculated for

C₂₂H₁₇N₄O₃S₂(M + H)⁺449.0737, found 449.0741.

(ESI+) 400.06 (M + H)⁺. HRMS (ESI+) m/z calculated for

C₁₇H₁₄N₅O₃S₂(M + H)⁺400.0526, found 400.0529.

N-(3-(1H-Tetrazol-5-ylthio)-4-hydroxynaphthalen-1-yl)-5-chloro-

thiophene-2-sulfonamide (38). This compound was prepared using

the procedure described for 15d using 13k (37 mg, 0.1 mmol) and

1H-tetrazole-5-thiol (10 mg, 0.1 mmol). The title compound 38 (36

mg, 81.6%, via 2 steps) was obtained as a gray solid; mp 159.4 °C

(dec.). HPLC 96% (R_t= 6.9 min, 45% CH₃CN in 0.1% TFA water, 40

1

min). H NMR (400 MHz, DMSO-d₆) δ 10.68 (br s, 1H), 10.32 (s,

1H), 8.25−8.23 (m, 1H), 7.95−7.93 (m, 1H), 7.57−7.55 (m, 2H),

7.20 (d, J = 4.0 Hz, 1H), 7.04 (d, J = 4.0 Hz, 1H), 6.98 (s, 1H). ¹³C

NMR (100 MHz, DMSO-d₆) δ 154.92, 138.97, 135.76, 133.03, 133.00,

130.29, 128.54, 128.45, 126.97, 126.50, 124.88, 124.02, 123.65, 107.13.

LC-MS (ESI+) 439.96 (M + H)⁺. HRMS (ESI+) m/z calculated for

C₁₅H₁₁ClN₅O₃S₃(M + H)⁺439.9707, found 439.9707.

N-(3-(1H-Tetrazol-5-ylthio)-4-hydroxynaphthalen-1-yl)-4′-

(trifluoromethyl)biphenyl-4-sulfonamide (39). This compound was

prepared using the procedure described for 15d using 13l (48 mg, 0.1

mmol) and 1H-tetrazole-5-thiol (10 mg, 0.1 mmol). The title

compound 39 (41 mg, 76.1%, via 2 steps) was obtained as a white

solid; mp 168 °C (dec.). HPLC 99% (R_t= 14.6 min, 50% CH₃CN in

0.1% TFA water 30 min). ¹H NMR (400 MHz, DMSO-d₆) δ 10.59 (br

s, 1H), 10.04 (s, 1H), 8.23−8.20 (m, 1H), 8.00−7.97 (m, 1H), 7.88−

7.82 (m, 4H), 7.77 (d, J = 8.6 Hz, 2H), 7.69 (d, J = 8.6 Hz, 2H), 7.54−

7.51 (m, 2H), 6.83 (s, 1H). LC-MS (ESI+) 544.08 (M + H)⁺. HRMS

(ESI+) m/z calculated for C₂₄H₁₇F₃N₅O₃S₂(M + H)⁺544.0719,

found 544.0704.

ASSOCIATED CONTENT

■

N-(3-(1H-Tetrazol-5-ylthio)-4-hydroxynaphthalen-1-yl)-4-chloro-

benzenesulfonamide (35). This compound was prepared using the

procedure described for 15d using 4-chloro-N-(3-chloro-4-oxonaph-

thalen-1(4H)-ylidene)benzenesulfonamide (13p) (37 mg, 0.1 mmol)

and 1H-tetrazole-5-thiol (10 mg, 0.1 mmol). The title compound 35

(35 mg, 81.6%, via 2 steps) was obtained as an off-white solid; mp

180.9 °C (dec.). HPLC 98% (R_t= 11.0 min, 40% CH₃CN in 0.1%

S

* Supporting Information

1

Supporting analytical data; H NMR, ¹³C NMR, LCMS, and

HPLC for key compounds. This material is available free of

charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION

Corresponding Author

*Phone: (813)-745-6076. Fax: (813)-745-6748. E-mail:

Harshani.Lawrence@moffitt.org.

■

1

TFA water, 30 min). H NMR (400 MHz, DMSO-d₆) δ 10.61 (br s,

1H), 10.06 (s, 1H), 8.323−8.20 (m, 1H), 7.94−7.91 (m, 1H), 7.57 (d,

J = 8.8 Hz, 2H), 7.55−7.52 (m, 2H), 7.45 (d, J = 8.8 Hz, 2H), 6.83 (s,

1H). ¹³C NMR (100 MHz, DMSO-d₆) δ 154.72, 138.99, 138.27,

132.96, 130.12, 129.78, 129.44, 128.41, 126.93, 126.50, 125.23, 124.24,

123.60, 106.88. LC-MS (ESI+) 434.01 (M + H)⁺. HRMS (ESI+) m/z

calculated for C₁₇H₁₃ClN₅O₃S₂(M + H)⁺434.0143, found 434.0129.

N-(3-(1H-Tetrazol-5-ylthio)-4-hydroxynaphthalen-1-yl)-3,4-di-

chlorobenzenesulfonamide (36). This compound was prepared using

the procedure for 15d using 3,4-dichloro-N-(3-chloro-4-oxonaphtha-

len-1(4H)-ylidene)benzenesulfonamide (13q) (40 mg, 0.1 mmol) and

1H-tetrazole-5-thiol (10 mg, 0.1 mmol). The title compound 36 (40

mg, 84.8%, via 2 steps) was obtained as a white solid; mp 174.4 °C

(dec.). HPLC 97% (R_t= 10.1 min, 45% CH₃CN in 0.1% TFA water,

40 min). ¹H NMR (400 MHz, DMSO-d₆) δ 10.64 (br s, 1H), 10.18 (s,

1H), 8.24−8.22 (m, 1H), 7.94−7.92 (m, 1H), 7.75 (appd, J = 2.0 Hz,

1H), 7.68 (d, J = 8.4 Hz, 1H), 7.56−7.54 (m, 2H), 7.51 (dd, J = 8.4,

1.6 Hz, 1H), 6.85 (s, 1H). ¹³C NMR (100 MHz, DMSO-d₆) δ 154.80,

140.35, 136.54, 132.95, 132.65, 132.07, 130.17, 129.21, 128.46, 127.63,

127.00, 126.55, 124.86, 124.15, 123.63, 107.07.; LC-MS (ESI+) 467.98

(M + H)⁺. HRMS (ESI+) m/z calculated for C₁₇H₁₂Cl₂N₅O₃S₂(M +

H)⁺467.9753, found 467.9752.

N-(3-(1H-Tetrazol-5-ylthio)-4-hydroxynaphthalen-1-yl)-

benzenesulfonamide (37). This compound was prepared using the

procedure described for 15d using N-(3-chloro-4-oxonaphthalen-

1(4H)-ylidene)benzenesulfonamide (13r) (32 mg, 0.1 mmol) and 1H-

tetrazole-5-thiol (10 mg, 0.1 mmol). The title compound 37 (32 mg,

78.9%, via 2 steps) was obtained as a white solid; mp 154.8 °C (dec.).

HPLC 92% (R_t= 6.5 min, 40% CH₃CN in 0.1% TFA water 30 min).

¹H NMR (400 MHz, DMSO-d₆) δ 10.57 (br s, 1H), 9.94 (s, 1H),

8.21−8.19 (m, 1H), 7.95−7.92 (m, 1H), 7.59−7.56 (m, 2H), 7.54−

7.48 (m, 3H), 7.39 (t, J = 8.0 Hz, 2H), 6.79 (s, 1H). ¹³C NMR (100

MHz, DMSO-d₆) δ 154.57, 140.16, 133.33, 133.03, 129.97, 129.60,

128.31, 127.48, 126.83, 126.47, 125.53, 124.32, 123.52, 106.87. LC-MS

Author Contributions

^⊥These authors contributed equally

ACKNOWLEDGMENTS

■

We acknowledge the NIH for funding (1PO1 CA118210-03),

̈

principal investigator Dr. Said M. Sebti. We also acknowledge

Experimental Lab, Chemical Biology Core, for high throughput

screening.

ABBREVIATIONS USED

■

CT-L, chymotrypsin like; T-L, trypsin like; SAR, structure−

activity relationship; PGPH, postglutamylpeptidase hydrolysis;

DCM, dichloromethane; THF, terahydrofuran; DMF, dime-

thylformamide; DBU, diazabicycloundecene; DMSO, dime-

thylsulfoxide; TFA, trifluoroacetic acid; DMEM, Dulbecco’s

Modified Eagle Medium; RPMI1640, Roswell Park Memorial

Institute-1640

REFERENCES

■

(1) Pickart, C. M. Back to the future with ubiquitin. Cell (Cambridge,

MA, U.S.) 2004, 116, 181−190.

(2) Ciechanover, A. Intracellular protein degradation: from a vague

idea, through the lysosome and the ubiquitin proteasome system, and

onto human diseases and drug targeting (Nobel lecture). Angew.

Chem., Int. Ed. 2005, 44, 5944−5967.

(3) Hershko, A. The ubiquitin system for protein degradation and

some of its roles in the control of the cell-division cycle (Nobel

lecture). Angew. Chem., Int. Ed. Engl. 2005, 44, 5932−5943.

1997

dx.doi.org/10.1021/jm201118h | J. Med. Chem. 2012, 55, 1978−1998

Journal of Medicinal Chemistry

Article

(4) Rose, I. Ubiquitin at fox chase. Prix Nobel 2005, 218−225.

(5) Verdoes, M.; Florea, B. I.; van der Marel, G. A.; Overkleeft, H. S.

Chemical Tools To Study the Proteasome. Eur. J. Org. Chem. 2009,

3301−3313.

(6) Ciechanover, A.; Schwartz, A. L. The ubiquitin−proteasome

pathway: the complexity and myriad functions of proteins death. Proc.

Natl. Acad. Sci. U.S.A. 1998, 95, 2727−2730. Ciechanover, A.;

Schwartz Alan, L. Ubiquitin-mediated degradation of cellular proteins

in health and disease. Hepatology 2002, 35, 3−6.

(7) King, R. W.; Deshaies, R. J.; Peters, J.-M.; Kirschner, M. W. How

proteolysis drives the cell cycle. Science 1996, 274, 1652−1658. Adams,

J. The development of proteasome inhibitors as anticancer drugs.

Cancer Cell 2004, 5, 417−421.

(8) Rajkumar, S. V.; Richardson, P. G.; Hideshima, T.; Anderson, K.

C. Proteasome inhibition as a novel therapeutic target in human

cancer. J. Clin. Oncol. 2005, 23, 630−639.

(9) Chauhan, D.; Hideshima, T.; Anderson, K. C. Proteasome

inhibition in multiple myeloma: therapeutic implication. Annu. Rev.

Pharmacol. Toxicol. 2005, 45, 465−476 2 plates..

(10) Papandreou, C. N.; Daliani, D.; Nix, D.; Yang, H.; Madden, T.;

Wang, X.; Pien, C. S.; Millikan, R. E.; Tu, S.-M.; Pagliaro, L.; Kim, J.;

Adams, J.; Elliott, P.; Esseltine, D.; Petrusich, A.; Dieringer, P.; Perez,

C.; Logothetis, C. J. Phase I trial of the proteasome inhibitor

bortezomib in patients with advanced solid tumors with observations

in androgen-independent prostate cancer. J. Clin. Oncol. 2004, 22,

2108−2121.

(11) Palombella, V. J.; Conner, E. M.; Fuseler, J. W.; Destree, A.;

Davis, J. M.; Laroux, F. S.; Wolf, R. E.; Huang, J.; Brand, S.; Elliott, P.

J.; Lazarus, D.; McCormack, T.; Parent, L.; Stein, R.; Adams, J.;

Grisham, M. B. Role of the proteasome and NF-kB in streptococcal

cell wall-induced polyarthritis. Proc. Natl. Acad. Sci. U.S.A. 1998, 95,

15671−15676.

(12) Wang, J.; Maldonado, M. A. The ubiquitin−proteasome system

and its role in inflammatory and autoimmune diseases. Cell. Mol.

Immunol. 2006, 3, 255−261. Meng, L.; Kwok, B. H.; Sin, N.; Crews, C.

M. Eponemycin exerts its antitumor effect through the inhibition of

proteasome function. Cancer Res. 1999, 59, 2798−2801.

(13) Groll, M.; Kim, K. B.; Kairies, N.; Huber, R.; Crews, C. M.

Crystal structure of epoxomicin:20S proteasome reveals a molecular

basis for selectivity of a′,b′-epoxyketone proteasome inhibitors. J. Am.

Chem. Soc. 2000, 122, 1237−1238.

(14) Groll, M.; McArthur Katherine, A.; Macherla Venkat, R.;

Manam Rama, R.; Potts Barbara, C. Snapshots of the fluorosalinospor-

amide/20S complex offer mechanistic insights for fine tuning

proteasome inhibition. J. Med. Chem. 2009, 52, 5420−5428.

(15) Kisselev, A. F.; Goldberg, A. L. Proteasome inhibitors: from

research tools to drug candidates. Chem. Biol. 2001, 8, 739−758.

(16) Meiners, S.; Ludwig, A.; Stangl, V.; Stangl, K. Proteasome

inhibitors: poisons and remedies. Med. Res. Rev. 2008, 28, 309−327.

(17) Fuchs, O. Proteasome inhibition as a therapeutic strategy in

patients with multiple myeloma. Mult. Myeloma 2009, 101−125.

(18) Lam, K. S.; Lloyd, G. K.; Neuteboom, S. T. C.; Palladino, M. A.;

Sethna, K. M.; Spear, M. A.; Potts, B. C. From natural products to

clinical trials: NPI-0052 (salinosporamide A), a marine actinomycete-

derived anticancer agent. Nat. Prod. Chem. Drug Discovery 2010, 355−

373.

biological evaluation of naphthoquinone analogs as a novel class of

proteasome inhibitors. Bioorg. Med. Chem. 2010, 18, 5576−5592.

(22) Kazi, A.; Lawrence, H.; Guida Wayne, C.; McLaughlin Mark, L.;

Springett Gregory, M.; Berndt, N.; Yip Richard, M. L.; Sebti Said, M.

Discovery of a novel proteasome inhibitor selective for cancer cells

over non-transformed cells. Cell Cycle 2009, 8, 1940−1951.

(23) Avdeenko, A. P.; Velichko, N. V.; Romanenko, E. A.;

Pirozhenko, V. V. Chlorination of N-arylsulfonyl-1,4-aminonaphthols

and N-arylsulfonyl-1,4-naphthoquinone-1,4-imines. Zh. Org. Khim.

1991, 27, 1747−1757.

(24) Altland, H. W.; Briffa, B. F. Jr. 1,4-Addition of triazolium

thiolates to quinones. J. Org. Chem. 1985, 50, 433−437.

(25) Avdeenko, A. P.; Evgrafova, N. I.; Ryazantsev, V. P.;

Luk’yanenko, L. V.; Titov, E. V.; Velichko, N. V. Preparation of N-

arylsulfonyl-2-chloro-1,4-naphthoquinone imines. USSR Patent

1558901, 86−4156772, 1558901, 19861204, , 1990.

(26) Avdeenko, A. P.; Evgrafova, N. I. Reaction of N-(arylsulfonyl)-p-

naphthoquinonimines with acylhydrazines. Zh. Org. Khim. 1987, 23,

1060−1063.

(27) Thiols; Coj, E.; Afanas’eva, G. B.; Chupakhin, O. N.; Sidorov, E.

O. Reactions of benzo analogs of N-phenyl-1,4-benzoquinone

monoimine with thiols. Zh. Org. Khim. 1989, 25, 2409−2416.

(28) Fujita, S.; Sano, K. Reduction of quinones and quinonemono-

sulfonimides with N,N-diethylhydroxylamine. J. Org. Chem. 1979, 44,

2647−2651.

(29) Lien, J.-C.; Huang, L.-J.; Teng, C.-M.; Wang, J.-P.; Kuo, S.-C.

Synthesis of 2-alkoxy 1,4-naphthoquinone derivatives as antiplatelet,

antiinflammatory, and antiallergic agents. Chem. Pharm. Bull. 2002, 50,

672−674.

(30) Obafemi, C. A. Studies in the heterocyclic compounds. II. The

mass spectra of some thiophene-sulfonyl derivatives. Phosphorus Sulfur

1980, 8, 201−204.

(31) Matsubara, R.; Doko, T.; Uetake, R.; Kobayashi, S.

Enesulfonamides as nucleophiles in catalytic asymmetric reactions.

Angew. Chem., Int. Ed. 2007, 46, 3047−3050.

(32) Adams, R.; Whitaker, L. Quinone imides. XXXIX. Adducts of

quinone monoimides and conversion of active methylene adducts to

benzofurans. J. Am. Chem. Soc. 1956, 78, 658−663.

(33) Travis, B. R.; Ciaramitaro, B. P.; Borhan, B. Preparation of

purified KHSO₅·H₂O and nBu₄NHSO₅from oxone by simple and

efficient methods. Eur. J. Org. Chem. 2002, 3429−3434.

(34) Altland, H. W.; Briffa, B. F. Jr. 1,4-Addition of triazolium

thiolates to quinones. J. Org. Chem. 1985, 50, 433−437.

(35) Johnston, C. I. Angiotensin receptor antagonists: focus on

losartan. Lancet 1995, 346, 1403−1407.

(36) Patani, G. A.; LaVoie, E. J. Bioisosterism: A rational approach in

drug design. Chem. Rev. 1996, 96, 3147−3176.

(19) Zhou, H.-J.; Aujay Monette, A.; Bennett Mark, K.; Dajee, M.;

Demo Susan, D.; Fang, Y.; Ho Mark, N.; Jiang, J.; Kirk Christopher, J.;

Laidig Guy, J.; Lewis Evan, R.; Lu, Y.; Muchamuel, T.; Parlati, F.; Ring,

E.; Shenk Kevin, D.; Shields, J.; Shwonek Peter, J.; Stanton, T.; Sun

Congcong, M.; Sylvain, C.; Woo Tina, M.; Yang, J. Design and

synthesis of an orally bioavailable and selective peptide epoxyketone

proteasome inhibitor (PR-047). J. Med. Chem. 2009, 52, 3028−3038.

(20) Sterz, J.; von Metzler, I.; Hahne, J.-C.; Lamottke, B.;

Rademacher, J.; Heider, U.; Terpos, E.; Sezer, O. The potential of

proteasome inhibitors in cancer therapy. Expert Opin. Invest. Drug

2008, 17, 879−895.

(21) Lawrence, H. R.; Kazi, A.; Luo, Y.; Kendig, R.; Ge, Y.; Jain, S.;

Daniel, K.; Santiago, D.; Guida, W. C.; Sebti, S. M. Synthesis and

1998

dx.doi.org/10.1021/jm201118h | J. Med. Chem. 2012, 55, 1978−1998

Article Doi

Discovery and synthesis of hydronaphthoquinones as novel proteasome inhibitors

DOI: 10.1021/jm201118h

Source and publish data:

Authors:

Article abstract of DOI:10.1021/jm201118h

Full text of DOI:10.1021/jm201118h

Products guided by the article

R&D Labs maybe for 1359834-46-0

Relevant to this article

Hot Product