Design, synthesis and structure-affinity relationships of aryloxyanilide derivatives as novel peripheral benzodiazepine receptor ligands

Bioorganic & Medicinal Chemistry 12 (2004) 423–438

Design, synthesis and structure–aﬃnity relationships of

aryloxyanilide derivatives as novel peripheral benzodiazepine

receptor ligands

Taketoshi Okubo,^aRyoko Yoshikawa,^bShigeyuki Chaki,^bShigeru Okuyama^c

and Atsuro Nakazato^a,*

^aMedicinal Chemistry Laboratory, Taisho Pharmaceutical Co., Ltd. 1-403 Yoshino-cho, Kita-ku, Saitama-shi, Saitama 331-9530, Japan

^bMedicinal Pharmacology Laboratory, Medicinal Research Laboratories, Taisho Pharmaceutical Co., Ltd. 1-403 Yoshino-cho, Kita-ku,

Saitama-shi, Saitama 331-9530, Japan

^cEthical Business Strategy Division, Taisho Pharmaceutical Co., Ltd. 1-403 Yoshino-cho, Kita-ku, Saitama-shi, Saitama 331-9530, Japan

Received 28July 2003; accepted 20 October 2003

Abstract—Since the peripheral benzodiazepine receptor (PBR) has been primarily found as a high-aﬃnity binding site for diazepam

in rat kidney, numerous studies of it have been performed. However, the physiological role and functions of PBR have not been

fully elucidated. Currently, we presented the pharmacological proﬁle of two high and selective PBR ligands, N-(2,5-dimethoxy-

benzyl)-N-(4-ﬂuoro-2-phenoxyphenyl)acetamide (7-096, DAA1106) (PBR: IC₅₀=0.28nM) and N-(4-chloro-2-phenoxyphenyl)-N-

(2-isopropoxybenzyl)acetamide (7-099, DAA1097) (PBR: IC₅₀=0.92 nM). The compounds are aryloxyanilide derivatives, and

identiﬁed with known PBR ligands such as benzodiazepine (1, Ro5-4864), isoquinoline (2, PK11195), imidazopyridine (3, Alpidem),

and indole (5, FGIN-1-27) derivatives. The aryloxyanilide derivatives, which have been derived by opening the diazepine ring of 1,

are a novel class as PBR ligands and have exhibited high and selective aﬃnity for peripheral benzodiazepine receptors (PBRs).

These novel derivatives would be useful for exploring the functions of PBR. In this paper, the design, synthesis and structure–

aﬃnity relationships of aryloxyanilide derivatives are described.

1. Introduction

PBR is composed of at least three subunits, an iso-

quinoline binding subunit with a molecular mass of 18

The peripheral benzodiazepine receptor (PBR) has been

found primarily as a high-aﬃnity binding site for

diazepam in rat kidney.¹In contrast to the central ben-

zodiazepine receptor (CBR), which is associated with g-

aminobutyric acid_A(GABA_A)-regulated ion channels²

in the central nervous system,^3,4PBR lacks coupling to

GABA_Areceptors.

kDa, a voltage-dependent anion channel (VDAC) with

a molecular mass of 32 kDa and an adenine nucleotide

carrier with a molecular mass of 30 kDa.¹⁵cDNA

encoding PBR has been cloned from humans,¹⁶

bovines,¹⁷rats¹⁸and mice.¹⁹PBR plays roles in cell

proliferation,²⁰steroidogenesis,²¹calcium ﬂow,²²cel-

lular respiration,²³cellular immunity,²⁴and malig-

nancy.²⁵

PBR has been found in many peripheral tissues,^5ꢀ7in

blood cells^7,8and in glial cells in the brain.^7,9,10Its pri-

mary localization has been reported to be mainly in the

mitochondrial outer membranes in many tissues,^11ꢀ14

although PBR is located on the inner membrane of the

rat lung mitochondria.¹³Furthermore, PBR was also

found on plasma membranes,^7,8which lack mitochon-

dria. Plasma membrane PBR has been described in heart,

liver, adrenal, and testis and on hematopoietic cells.⁷

As endogenous ligands for peripheral benzodiazepine

receptors (PBRs), anthraline, diazepam-binding inhi-

bitor (DBI) and proptoporphyrin IV have been repor-

ted. Anthraline, 16 kDa protein, binds to both PBR and

the dihydropyridine binding sites.²⁶DBI, a 104 amino

acid neuropeptide,²⁷has been found in human brain,

and DBI-like immunoreactivity has been found in the

cerebrospinal ﬂuid of human volunteers.²⁸DBI has also

been found in peripheral tissues rich in PBRs, such as

adrenal gland, testis and kidney.²⁹The major physio-

logical porphyrins, protoporphyrin IX and heme, have

been labeled PBR with nanomolar aﬃnity, and their

* Corresponding author. Tel.: +81-48-663-1111; fax: +81-48-652-

7254; e-mail: atsu.nakazato@po.rd.taisho.co.jp

doi:10.1016/j.bmc.2003.10.050

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T. Okubo et al. / Bioorg. Med. Chem. 12 (2004) 423–438

aﬃnity has been 1000 times higher for PBRs than for

central benzodiazepine receptors (CBRs).³⁰

PBR has exhibited diﬀerent speciﬁcities for ligands.

Compounds 1 (Ro5-4864) and 2 (PK11195) exhibited

high aﬃnity for PBRs but not for CBRs,^9,31,32whereas

compound 3 (clonazepam) exhibited low aﬃnity for

PBRs and high aﬃnity for CBRs.³³Interestingly, in

contrast to the highly species-dependent interaction of

compound 1 with PBRs,^34ꢀ37compound 2 exhibited

high aﬃnity for PBRs from both humans and bovines.³²

As other PBR ligands, compounds 4 (alpidem) and 5

(FGIN-1) have been reported. Compound 4 is an imi-

dazopyridine derivative and binds with high aﬃnity to

both PBRs and CBRs.³⁸Compound 5 is a 2-aryl-3-

indoleacetamide derivative and exhibits high aﬃnity for

PBRs with high selectivity over CBRs (Chart 1).^39,40

The physiological functions of PBR have not been fully

elucidated, due in part to the lack of potent and selec-

tive ligands for PBRs. Our interest was concentrated on

opening the diazepine ring of 1 for discovering new

PBR ligand since 1 has more rigid structure than other

PBR ligands such as 2, 4 and 5. We have presented

potent and selective PBR ligands 7-096 (DAA1106)

(PBR: IC₅₀=0.28nM, CBR: IC ₅₀>1000 nM) and 7-099

(DAA1097) (PBR: IC₅₀=0.92 nM, CBR: IC₅₀>1000

nM),^41ꢀ43compounds which were novel aryloxyanilide

derivatives designed by opening the diazepine ring of 1

(Fig. 1). Compound 7-096 is potent and selective ligand

for PBRs since the binding of [³H]7-096 has not been

aﬀected by several neurotransmitter-related com-

pounds, including adrenoceptor, g-aminobutylic acid,

dopamine, 5-hydroxytrypyamine, acetylcholine, histamine,

glutamate and CBR ligands even at a concentration of

10 mM.⁴²Compounds 7-096 and 7-099 showed potent

anxiolytic-like properties in laboratory animals.⁴¹Fur-

thermore, it has been suggested that (1) 7-096 and 7-099

binding sites on PBR share common domain with that

of PK11195, but also contain motif that do not interact

eﬃciently with PK11195; (2) these additional sites are

par of the PBR molecular, since similar result are found

using cells or recombinant PBR; (3) the binding of 7-099

to PBR induces changes in the receptor similar to that

Figure 1.

triggered by PK11195, allowing steroidogenesis activa-

tion; (4) the fact that 7-096 dose not activate ster-

oidogenesis despite its high aﬃnity for PBR suggests

that its binding on PBR leads to conformational chan-

ges that do not permit or antagonize PBR steroidogenic

function.⁴³Thus, aryloxyanilide derivatives are unique

PBR ligands for studying the structure–function

relationship of PBR.

In this paper, the design, synthesis and structure–aﬃnity

relationships of aryloxyanilide derivatives, which are

novel PBR ligands, are presented.

2. Chemistry

The syntheses of derivatives 6, 7, 8 and 9 are shown in

Schemes 1–8.

General synthetic methods for aryloxyanilide derivative

7 are indicated in Scheme 1.

Noncommercial 2-aryloxyaniline 11 was prepared by

treatment of 2-halonitrobenzene 10 with hydroxyaryl

compounds under basic conditions followed by hydro-

genolysis (Method A) or reduction utilizing powdered

Fe (Method B) (Table 1).

The 2-aryloxyaniline 11 was treated with acyl chloride

under basic conditions followed by arylmethylchloride

in the presence of sodium hydride to aﬀord derivative 7

(Method C). Formyl compound 7-061 was synthesized

by benzylation utilizing 2-methoxybenzylchloride in the

presence of sodium hydride after treatment of com-

pound 11 with formic acid (Method D). Furthermore,

derivative 7 was prepared by reductive alkylation of 2-

aryloxyaniline 11 with the corresponding carbonyl

compound utilizing sodium borohydride followed by

acylation using acyl chloride (Method E) or by reduc-

tive alkylation of 2-aryloxyaniline 11 with the corres-

ponding carbonyl compound utilizing hydrogenation

followed by acylation using acid anhydride (Method F).

Chart 1.

T. Okubo et al. / Bioorg. Med. Chem. 12 (2004) 423–438

425

The methods of synthesis of urea and carbamate com-

pounds are shown in Scheme 1. Urea compounds 7-

078, 7-079, 7-112-7-114 were obtained by reaction of N-

benzylaryloxyaniline 13 with triphosgen followed by

addition of the corresponding amines (Method G).

Urea compound 7-077 was obtained by treatment of N-

benzylaryloxyaniline 13 with KNCO (Method H). Car-

bamate compounds 7-080 and 7-081 were prepared by

treatment of N-benzylaryloxyaniline 13 with triphosgen

followed by the corresponding sodium alkoxides

(Method I).

Acetal compound 7-115, which was synthesized by

Method C, was deprotected under acidic conditions to

yield aldehyde 7-028 (Method J) (Scheme 2).

The method of synthesis of derivative 7 via aldehyde 7-

028 as a key intermidiate is shown in Scheme 2. Alde-

hyde 7-028 was treated with Grignard reagent or Wittig

reagent to yield alcohol 7-030 and 7-31 or vinyl phenyl

compounds 7-027 and 7-116, respectively (Method K or

Method M). In compound 7-113, the 2-propenyl group

was a mixture of E and Z isomers, and its hydrogena-

Scheme 1. Reagents and conditions: (a) Ar²OH, K₂CO₃, DMF; (b) PtO₂, H₂, MeOH; (c) Fe, NH₄Cl, EtOH, H₂O; (d) R¹COCl, Et₃N, CH₂Cl₂; (e)

HCO₂H, toluene; (f) NaH, Ar¹CH₂Cl, DMF; (g) Ar¹CH₂C¼O(R²), NaBH₄, MeOH; (h) Ar¹CH₂C¼O(R²) H₂, PtO₂, MeOH; (i) (R¹CO)₂O, pyri-

dine; (j) triphosgen, CH₂Cl₂and then R³R⁴NH (k) KNCO, H₂O; (l) triphosgen, CH₂Cl₂and then R⁵ONa. Method A: a, b; Method B: a, c; Method

C: d, f; Method D: e,f; Method E: g, d; Method F: h, i; Method G: g, i; Method H: g, k; Method I: g, l.

Scheme 2. Reagents and conditions: (m) TsOH–H₂O, acetone; (n) R⁶MgBr, THF; (o) (COCl)₂, DMSO, Et₃N, CH₂Cl₂; (p) R⁷CH¼PPh₃, THF; (q)

H₂, PtO₂, MeOH. Method J: m; Method K: n; Method L: o; Method M: p; Method N: q.

426

T. Okubo et al. / Bioorg. Med. Chem. 12 (2004) 423–438

tion yielded propyl compound 7-026 (Method N).

Swern oxidation of alcohol 7-030 aﬀorded keto com-

pound 7-29 (Method L).

The synthesis of 8 is described in Scheme 7. Compound

8 was synthesized from N-acetyl-2-phenoxyaniline 12-

001 by Ulmann reaction utilizing CuBr and copper

powder (Method Y).

The 2-nirobenzyl compound 7-036, which was synthe-

sized by Method E, was hydrogenalated on PtO₂to

yield aniline compound 7-037 (Method O). By treat-

ment of 7-037 with 1,4-dibromobutane, pyrrolidine

compound 7-038 was formed (Method P) (Scheme 3).

Scheme 8 shows the method of synthesis of 9, which has

a 2-phenylethyl group on the nitrogen atom. N-acyla-

tion of 2-phenoxyaniline 11-003 with 2-methoxy-

phenylacetylchloride and reduction with LiAlH₄gave

14. Acetylation of 14 with acetylchloride yielded the

desired product 9 (Method Z).

Ester compound 7-032 was hydrolyzed under basic

conditions to yield the acid compound 7-033 (Method

Q), which was amidated with corresponding amines via

acyl chloride (Method R) (Scheme 4).

3. Results and discussion

Introduction of a hydroxy group and amino group at

the terminal end of an acetyl group (R¹=Me) 7-005 was

performed via chloroacetyl compound 7-072 (Scheme

5). N-Chloroacetyl-2-phenoxyanilide 7-072, which was

synthesized by Method B, was converted to 7-073 by

treatment with AcONa in the presence of phase transfer

catalysis (Method S), and then hydrolysis of the term-

inal acetyl group of 7-073 then yielded the hydroxy-

acetyl compound 7-074 (Method T). An azido group

was introduced by treatment of 7-072 with NaN₃to

yield the azido compound 7-075 (Method U). Hydro-

genation of 7-075 gave aminoacetyl compound 7-073

(Method V).

Compounds 1, 2, 5, 6, 7-001–7-114, 7-118, 8 and 9 were

evaluated for PBRs binding aﬃnities in mitochondria

prepared from rat cerebral cortex against radioligand

The hydroxyl phenyl compound 7-022 and hydroxy-

carbonylmethoxy compound 7-020 were synthesized

from compound 7-117, which was synthesized by

Method C, in Scheme 6. Hydrolysis of the acetyl group

of 7-117 yielded 7-022 (Method W). O-Alkylation of 7-

022 with ethyl bromoacetate under basic conditions

followed by hydrolysis of its acetate yielded 7-020

(Method X).

Scheme 5. Reagents and conditions: (v) AcONa, n-Bu₄NBr, PhH; (w)

K₂CO₃, MeOH; (x) NaN₃, DMF; (y) H₂, PtO₂, MeOH; Method S: v;

Method T: w; Method U: x; Method V: y.

Scheme 3. Reagents and conditions: (r) H₂, PtO₂, MeOH; (s) 1,4-

dibromobutane, K₂CO₃, KI, DMF; Method O: r; Method P: s.

Scheme 6. Reagents and conditions: (z) aq KOH, MeOH; (aa)

BrCH₂CO₂Me, NaH, DMF; Method W: z; Method X: aa, z.

Scheme. 4. Reagents and conditions: (t) aq KOH, MeOH; (u) SOCl₂,

HMPA, THF then aq R⁷MeNH; Method Q: t; Method R: u.

Scheme 7. Reagents and conditions: (ab) 2-Methoxyiodobenzene, Cu,

CuBr, K₂CO₃, PhNO₂; Method Y: ab.

T. Okubo et al. / Bioorg. Med. Chem. 12 (2004) 423–438

427

ings suggest the following: (1) the electron density on

the benzene ring of the benzyl group might not aﬀect

interaction between PBR and ligand, and (2) the length

of the substituent on the benzene or the pyridine ring is

more important in yielding high PBR aﬃnity than the

steric bulk of the substituent.

In contrast, the hydroxycarbonylmethoxy compound 7-

033 did not exhibit signiﬁcant aﬃnity for PBRs, and

compounds substituted with an alkyl-containing

hydroxyl group (7-030 and 7-031) exhibited 16- and 19-

fold lower aﬃnities for PBRs, respectively, than keto

compound 2-029. The dimethylaminoethoxy compound

7-021 exhibited moderate aﬃnity for PBRs, its aﬃnity

was much lower than that of isopentyl compound 7-018

but higher than that of acid compound 7-20. Amidation

of the carboxylic acid of 7-033 with monomethylamine

(7-034) or dimethylamine (7-035) increased PBR aﬃnity

compared with 7-033. More interestingly, amino com-

pound 7-037 did not exhibit signiﬁcant PBR aﬃnity but

pylloridino compound 7-038 and nitro compound 7-036

exhibited high aﬃnities for PBRs. In light of the evi-

dence, it is clear that a hydrophilic substituent including

an acidic proton such as carboxylic, phenolic, alcoholic

or amino proton is unsuitable for high PBR aﬃnity. This

phenomenon might be described below: (1) the acidic

proton might hinder the relationship between PBR and

ligand or (2) the acidic proton might change the mole-

cular conformation of the corresponding original ligand.

Scheme 8. Reagents and conditions: (ac) 2-methoxyphenylacetyl-

chloride, Et₃N, CH₂Cl₂; (ad) LiAlH₄, THF; (ae) AcCl, Et₃N, CH₂Cl₂;

Method Z: ac–ae.

[³H]-PK11195,⁴¹and the obtained IC₅₀values are

shown in Table 1. High-PBR-aﬃnity compounds (IC₅₀

<100 nM) among compounds 6, 7-001–7-114, 7-118, 8

and 9 did not exhibit signiﬁcant CBR binding aﬃnity

(IC₅₀>1000 nM) in membranes prepared from rat cer-

ebral cortex against radioligand [³H]ﬂunitrazepam.⁴¹

Compound 6, which was designed by opening the dia-

zepine ring of 1 (Fig. 1), demonstrated high aﬃnity for

PBRs, with an IC₅₀value of 6.7 nM. Furthermore, our

eﬀort at chemical modiﬁcation of N-methyl group of 6

yielded the N-benzyl compound 7-001 as the best com-

pound in points of aﬃnity and selectivity for PBRs over

CBRs (PBR: IC₅₀=2.9 nM, CBR: IC₅₀>1000 nM).

Based on the data, we concentrated our interest on

chemical modiﬁcation of Ar¹, Ar², R¹, X¹and Y.

Among dimethoxybenzyl compounds (7-039–7-043),

2,5-dimethoxy compound 7-041 exhibited the highest

aﬃnity for PBRs (IC₅₀=0.085 nM), with aﬃnity

slightly higher than that of 2-methoxy compound 7-006.

2,3-, 2,4- and 3,5-dimethoxy compounds, 7-039, 7-040

and 7-043, exhibited slightly lower aﬃnity for PBRs

than 2-methoxy compound 7-006, but 2,6-dimethoxy

compound 7-042 did not exhibit signiﬁcant aﬃnity for

PBRs. Furthermore, 2,4,6-trimethoxy compound 7-044

did not exhibit signiﬁcant aﬃnity for PBRs. These ﬁnd-

ings suggest that the methoxy group plays the role of

controller in creating suitable conformation of the ben-

zene ring for interaction with PBR.

3.1. Chemical modiﬁcation of Ar¹

Introduction of a methoxy group or chloro atom onto

the phenyl ring of the N-benzyl group in 7-001 tended to

increase binding aﬃnity (7-006–7-010 versus 7-001).

Among these, 2-mthoxy compound 7-005 and 2-chloro

compound 7-008 exhibited much higher binding aﬃnity

for PBRs, with IC₅₀values of 0.15 and 0.49 nM,

respectively. This tendency was observed for pyridine

compounds 7-002–7-004 and 7-011–7-013 too, as well.

Conversion of the phenyl group of the benzyl group

with a pyridine ring resulted in signiﬁcant decrease in

aﬃnity for PBRs (7-002–7-004 versus 7-001). Introduc-

tion of a methoxy group at the ortho position from the

methylene group of the pyridylmethyl group increased

aﬃnity for PBRs markedly (7-002 versus 7-011, 7-003

versus 7-012 and 7-013). These results suggest that con-

formation of the aromatic ring is important in obtaining

high aﬃnity for PBRs.

3.2. Chemical modiﬁcation of Ar²

Conversion of the phenyl group (Ar²) with a naphthyl

(7-045) or pyridyl (7-046–7-048) group decreased aﬃnity

for PBRs. In particular, pyridyl compounds 7-046–7-

048 did not exhibit signiﬁcant aﬃnity for PBRs

(IC₅₀>100 nM). Next, utilizing methoxy, methyl and

ﬂuoro groups, the relationship between substituted

position on the phenyl group and PBR aﬃnity was

investigated. On the whole, the order of suitable posi-

tion for PBR aﬃnity was 4-position ꢁ3-position ꢁ2-

position. However, the better compounds among them,

7-051 (IC₅₀=0.16 nM), 7-052 (IC₅₀=0.11 nM), 7-054

(IC₅₀=0.12 nM) and 7-057 (IC₅₀=0.29 nM) exhibited

almost the same PBR aﬃnity as non-substituted com-

pound 7-005 (IC₅₀=0.15 nM). Furthermore, methylthio

(7-058: IC₅₀=2.2 nM), chloro (7-059: IC₅₀=8.9 nM)

and bromo (7-060: IC₅₀=13 nM) compounds exhibited

lower aﬃnity for PBRs than the corresponding methoxy

Next, the methoxy group of 7-005 was converted with

various substituents. 2-Fluoro (7-023), 2-bromo (7-024),

2-methyl (7-025) and nitro (7-036) compounds exhibited

high aﬃnity for PBRs, but the aﬃnities were respec-

tively 44-, 23-, 28- and 31-fold lower than that of 7-005.

The size (C_1ꢀ5) of the alkoxy group did not signiﬁcantly

aﬀect aﬃnity for PBRs (7-005 versus 7-014–7-018). 2-

Methylthio compound 7-019 exhibited the same PBR

aﬃnity as the corresponding methoxy compound 7-005.

2-Propyl (7-026), 2-vinyl (7-027), formyl (7-028), acyl (7-

029) and methoxycarbonyl (7-032) compounds had the

same or slightly increased binding aﬃnity for PBRs

compared with methoxy compound 7-005. These ﬁnd-

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T. Okubo et al. / Bioorg. Med. Chem. 12 (2004) 423–438

Table 1. Aryloxyanilide derivatives: physical and binding data

Compd Method^a

Ar¹–Y

Ar²

R¹CO

X¹

Analysis^b

Mp (^ꢂC)^c

IC₅₀(nM)^d,e

1

2

5

6

3.1

1.1

5.5

6.7

Me

Ph–CH₂

2-Py–CH₂

3-Py–CH₂

4-Py–CH₂

Ph

Me–CO

H

C₁₅H₁₅NO₂

C₂₁H₁₉NO₂

C₂₀H₁₈N₂O₂

C₂₂H₂₁NO₃

C₂₁H₁₈ClNO₂

C₂₁H₂₀N₂O₃

C₂₃H₂₃NO₃

C₂₄H₂₅NO₃

C₂₆H₂₉NO₃

C₂₂H₂₁NO₂S

C₂₃H₂₁NO₅

C₂₅H₂₈N₂O₃

C₂₁H₁₉NO₂

C₂₁H₁₈FNO₂

C₂₁H₁₈BrNO₂

C₂₂H₂₁NO₂

C₂₄H₂₅NO₂

C₂₃H₂₁NO₂

C₂₂H₁₉NO₃

C₂₃H₂₁NO₃

C₂₃H₂₃NO₃

C₂₄H₂₅NO₃

C₂₃H₂₁NO₄

C₂₂H₁₉NO₄

C₂₃H₂₂N₂O₃

C₂₄H₂₄N₂O₃

C₂₁H₁₈N₂O₄

C₂₁H₂₀N₂O₂

Oil

80.5–81.0 (Et₂O)

86.5–87.5 (Et₂O)

83.5–80.0 (Et₂O)

114.5–115.0 (Et₂O)

83–84 (acetone-hex)

7-001

7-002

7-003

7-004

7-005

7-006

7-007

7-008

7-009

7-010

7-011

7-012

7-013

7-014

7-015

7-016

7-017

7-018

7-019

7-020

7-021

7-022

7-023

7-024

7-025

7-026

7-027

7-028

7-029

7-030

7-031

7-032

7-033

7-034

7-035

7-036

7-037

7-038

7-039

7-040

7-041

7-042

7-043

7-044

7-045

7-046

7-047

7-048

7-049

7-050

7-051

7-052

7-053

7-054

7-055

7-056

7-057

7-058

7-059

C

E

C

X

E

W

C

E

N

M

J

L

K

F

Q

R

E

O

P

C

F

C

F

C

F

2.9

28

>100

83

2-MeO–Ph–CH₂

3-MeO–Ph–CH₂

4-MeO–Ph–CH₂

2-Cl–Ph–CH₂

3-Cl–Ph–CH₂

4-Cl–Ph–CH₂

3-MeO–2–Py–CH₂

2-MeO–3–Py–CH₂

4-MeO–3–Py–CH₂

2-EtO–Ph–CH₂

0.15

1.4

0.66

0.49

2.0

1.2

1.0

0.50

1.1

Oil

99.5–100.0

Oil

92.0–93.0 (hex–Et₂O)

95.0–96.0 (Standed)

78.5–79.0 (IPE–hex)

90.5-91.0 (IPE–hex)

Oil

0.12

0.098

0.15

0.16

0.18

>100

33

2-n-PrO–Ph–CH₂

2-i-PrO–Ph–CH₂

2-n-PenO–Ph–CH₂

2-i-PenO–Ph–CH₂

2-MeS–Ph–CH₂

2-HO₂CCH₂O–Ph–CH₂

2-Me₂NCH₂CH₂O–Ph–CH₂

2-HO–Ph–CH₂

156.5–157.0 (IPE)

Oil

123.0–124.5 (IPE)

90.0–90.5 (IPE)

84.0–84.5 (IPE)

83.5–84.0 (IPE)

3.2

6.7

3.5

4.2

0.22

0.20

0.38

0.27

4.4

2-F–Ph–CH₂

2-Br–Ph–CH₂

2-Me–Ph–CH₂

2-n–Pr–Ph–CH₂

2-(CH₂=CH)–Ph–CH₂

2-OHC–Ph–CH₂

2-MeCO–Ph–CH₂

2-(MeC(OH)H)–Ph–CH₂

2-(EtC(OH)H)–Ph–CH₂

2-MeO₂C–Ph–CH₂

2-HO₂C–Ph–CH₂

2-MeHNCO–Ph–CH₂

2-Me₂NCO–Ph–CH₂

2-NO₂–Ph–CH₂

2-NH₂–Ph–CH₂

2-Pyrrolidino–Ph–CH₂

2,3-(MeO)₂–Ph–CH₂

2,4-(MeO)₂–Ph–CH₂

2,5-(MeO)₂–Ph–CH₂

2,6-(MeO)₂–Ph–CH₂

3,5-(MeO)₂–Ph–CH₂

2,4,6-(MeO)₃–Ph–CH₂

2-MeO–Ph–CH₂

Oil

114.0–117.0 (Standed)

110.0–110.5 (AcOEt–hex)

Oil

5.2

Ph

76.0–78.0 (IPE)

Oil

0.064

63

2.9

3.7

4.6

Oil

96.0–96.5 (AcOEt–hex)

155.5-156.0 (MeOH)

>100

1.3

.

C₂₅H₂₆N₂O₂HCl 110.0-112.5 (AcOEt–Et₂O)

C₂₃H₂₃NO₄

C₂₄H₂₅NO₅

C₂₆H₂₃NO₃

C₂₁H₂₀N₂O₃

C₂₃H₂₃NO₄

C₂₃H₂₃NO₃

C₂₂H₂₀FNO₃

C₂₃H₂₃NO₃S

C₂₂H₂₀ClNO₃

Oil

0.29

0.72

0.085

>100

0.26

>100

11

>100

0.72

0.34

0.16

0.11

0.29

0.12

39

Oil

Ph

Oil

66.0–68.0 (AcOEt–hex)

81.0–82.0 (Et₂O)

64.0–65.0 (AcOEt–hex)

93.0–94.0 (Et₂O)

Oil

1-Nap

2-Py

3-Py

4-Py

2-MeO–Ph

3-MeO–Ph

4-MeO–Ph

2-Me–Ph

3-Me–Ph

4-Me–Ph

2-F–Ph

3-F–Ph

4-F–Ph

4-MeS–Ph

4-Cl–Ph

Oil

79.0–80.0 (AcOEt–hex)

104.0–105.0 (AcOEt–hex)

54.0–55.0 (AcOEt–hex)

Oil

97.0–98.0 (Et₂O–hex)

62.0–63.0 (Et₂O–hex)

0.41

0.29

2.2

8.90

(continued on next page)

T. Okubo et al. / Bioorg. Med. Chem. 12 (2004) 423–438

429

Table 1 (continued)

Compd Method^a

Ar¹–Y

Ar²

R¹CO

X¹

Analysis^b

Mp (^ꢂC)^c

IC₅₀(nM)^d,e

7-060

7-061

7-062

7-063

7-064

7-065

7-066

7-067

7-068

7-069

7-070

7-071

7-072

7-073

7-074

7-075

7-076

7-077

7-078

7-079

7-080

7-081

7-082

7-083

7-084

7-085

7-086

7-087

7-088

7-089

7-090

7-091

7-092

7-093

7-094

7-095

7-096

7-097

7-098

7-099

7-100

7-101

7-102

7-103

7-104

7-105

7-106

7-107

7-108

7-109

7-110

7-111

7-112

7-113

7-114

7-115

7-116

7-117

7-118

8

F

C

E

S

T

U

V

H

G

I

2-MeO–Ph–CH₂

2,5-(MeO)₂–Ph–CH₂

2-EtO–Ph–CH₂

4-Br–Ph

Ph

Me–CO

H–CO

Et–CO

H

C₂₂H₂₀BrNO₃116.0–117.0 (AcOEt–hex)

13

0.57

0.093

1.3

3.5

1.5

1.8

1.0

5.6

24

4.6

0.34

8.9

3.9

C₂₁H₁₉NO₃

C₂₃H₂₃NO₃

C₂₄H₂₅NO₃

C₂₅H₂₇NO₃

C₂₆H₂₉NO₃

C₂₄H₂₃NO₃

C₂₅H₂₅NO₃

C₂₆H₂₇NO₃

C₂₇H₂₃NO₃

C₂₂H₁₈F₃NO₃

C₂₂H₂₀ClNO₃

C₂₄H₂₃NO₅

C₂₂H₂₁NO₄

C₂₂H₂₀N₄O₃

C₂₂H₂₂N₂O₃

C₂₁H₂₀N₂O₃

C₂₂H₂₂N₂O₃

C₂₃H₂₄N₂O₃

C₂₂H₂₁NO₄

C₂₃H₂₃NO₄

C₂₂H₂₀FNO₃

Oil

n-Pr–CO

i-Pr–CO

n-Bu–CO

n–Pen–CO

c-Pr–CO

c-Bu–CO

c-Pen–CO

Ph–CO

94.5–95.0 (Et₂O)

Oil

73.0–74.0 (Et₂O–hex)

85.0-86.0 (Et₂O–hex)

92.5–93.5 (Et₂O–hex)

125.5–127.0 (AcOEt–hex)

Oil

83.0–83.5 (Standed)

Oil

70.0–71.0 (Standed)

Oil

85.0–86.0 (AcOEt–IPE)

89.5–90.0 (AcOEt)

133.0–134.0 (AcOEt)

94.5–95.0 (standed)

Oil

CF₃–CO

ClCH₂–CO

MeCO₂CH₂–CO

HOCH₂–CO

N₃CH₂–CO

H₂NCH₂–CO

NH₂–CO

Me(H)N–CO

Me₂N–CO

MeO–CO

EtO–CO

Me–CO

11

>100

3.5

4.6

100

0.45

0.87

0.34

0.79

0.50

48

H

I

H

Oil

C

F

G

C

M

E

F

Y

Z

4-F

5-F

6-F

3-Cl

4-Cl

5-Cl

3-Me

4-Me

5-Me

5-CF₃

5-MeO

5-H₂NCO

83.5–84.0 (AcOEt–hex)

91.5–92.0 (AcOEt–hex)

Oil

Me–CO

Et–CO

Me–CO

C₂₂H₂₀ClNO₃105.5–106.5 (AcOEt–hex)

C₂₂H₂₀ClNO₃113.0–114.5 (AcOEt–hex)

C₂₂H₂₀ClNO₃109.0–109.5 (AcOEt–hex)

0.20

2.0

63

0.87

0.34

2.2

C₂₃H₂₃NO₃

84.5–85.5 (AcOEt–hex)

107.5–108.0 (AcOEt–hex)

81.5–82.0 (AcOEt–hex)

C₂₃H₂₀F₃NO₃113.0–113.5 (AcOEt–hex)

C₂₃H₂₃NO₄

C₂₃H₂₂N₂O₄

125.5–126.0 (AcOEt–hex)

250.0–251.0 (Standed)

192.5–193.5 (Standed)

Oil

8.1

Ph

>100

1.3

5-H₂NSO₂C₂₂H₂₂N₂SO₅

4-F

5-F

4-Cl

H

C₂₃H₂₂FNO₄

C₂₃H₂₂ClNO₃

C₂₄H₂₄ClNO₃

C₂₃H₂₂ClNO₄

C₂₃H₂₂ClNO₃

C₂₄H₂₄ClNO₃

C₂₅H₂₆ClNO₃

C₂₄H₂₄ClNO₄

C₂₅H₂₆ClNO₃

C₂₅H₂₆ClNO₄

C₂₄H₂₃ClFNO₃

C₂₄H₂₄ClNO₄

C₂₄H₂₄ClNO₅

92.5–93.5 (IPE)

103.5–104.0 (hex)

95.5–96.0 (hex)

108.0–108.5 (hex)

103.5–105.0 (IPE)

Oil

81.5–83.0 (hex)

87.5–88.0 (hex)

Oil

0.28

0.79

0.68

0.92

0.18

6.6

0.93

1.1

13

6.9

17

11

6.1

3.2

6.7

3.3

2.2

4.3

2.2

NT

2.2

9.8

0.45

2-n-PrO–Ph–CH₂

2-i-PrO–Ph–CH₂

2,5-(MeO)₂–Ph–CH₂

2-MeO–Ph–CH₂

2-EtO–Ph–CH₂

2-n-PrO–Ph–CH₂

2-i-PrO–Ph–CH₂

2,5-(MeO)₂–Ph–CH₂

2-i-PrO–Ph–CH₂

2,5-(MeO)₂–Ph–CH₂

2-(OCH₂CH₂O)CH–Ph–CH₂

2-(MeCH¼CH)–Ph–CH₂

2-CH₃CO₂–Ph–CH₂

2-MeO–Ph–CH(Me)

2-MeO–Ph

Ph

Oil

4-Me–Ph

4-MeO–Ph

4-F–Ph

4-Me–Ph

4-MeO–Ph

4-F–Ph

4-Me–Ph Me(H)N–CO

4-MeO–Ph Me(H)N–CO

4-F–Ph

Ph

95.0–96.0 (Et₂O–hep)

53.0–56.0 (Et₂O–hep)

82.0–83.0 (Et₂O–hep)

109.0–110.0 (Et₂O–hep)

121.0–122.0 (Et₂O–hep)

C₂₃₄H₂₁ClFNO₄102.0–103.0 (Et₂O–hep)

C₂₄H₂₅ClN₂O₄

C₂₄H₂₅ClN₂O₅

C₂₃H₂₂ClFN₂O₄

C₂₄H₂₃NO₄

130.0–131.0 (Et₂O)

153.0–154.0 (Et₂O)

127.0–128.0 (Et₂O)

Oil

Me(H)N–CO

Me–CO

H

Oil

Ph

C₂₃H₂₁NO₄

C₂₃H₂₃NO₃

C₂₁H₁₉NO₃

C₂₃H₂₃NO₃

96.5–97.0 (Standed)

Oil

79.0–80.0 (hex)

9

2-MeO–Ph–(CH₂)₂

H

^aMethods are described in the text.

^bElemental analyses for all compounds were within ꢃ0.4% of the theoretical values for the indicated formula.

^cStand, compounds were allowed to stand at room temperature to crystallize; Hex, hexane; IPE, diisopropylether; Hep, heptane.

^dIC₅₀values represent the means of 1–3 separate experiments obtained from 5–10 concentrations of each compound, run in duplicate. Variation

between experiments was less than 25%. NT, not test.

^eHigh-PBR-aﬃnity compounds (IC₅₀<100 nM) among compounds 6, 7-001–7-114, 7-118, 8 and 9 did not exhibit signiﬁcant CBR binding aﬃnity

(IC₅₀>1000 nM) in membranes prepared from rat cerebral cortex against radioligand [³H]ﬂunitrazepam.

430

T. Okubo et al. / Bioorg. Med. Chem. 12 (2004) 423–438

(7-051: IC₅₀=0.16 nM) and ﬂuoro (7-057: IC₅₀=0.29

nM) compounds. These ﬁndings suggest that introduc-

tion of a substituent onto the benzene ring does not

increase aﬃnity for PBRs.

090) group onto the 4-, 5- or 6-position produced a

comparatively slight decrease in PBR aﬃnity. However,

introduction of a chloro (7-085: IC₅₀=48nM) or methyl

group (7-088: IC₅₀=63 nM) onto the 3-position marked

decreased the aﬃnity of 7-005 for PBRs. These ﬁndings

suggest that the substituent at the 3-position produce

steric hindrance to interaction with PBR or to negatively

aﬀect the conformation of Ar¹for interaction with PBR.

3.3. Chemical modiﬁcation of R¹

In R¹, exchange of the methyl group of the acetyl group

in 7-005 with a proton slightly decreased PBR aﬃnity

(7-005 versus 7-061), but prolongation of methyl to an

ethyl group slightly increased PBR aﬃnity, with an IC₅₀

value of 0.093 nM, (7-005 versus 7-062). Compounds 7-

063–7-069, compounds which had alkyl groups longer

or larger than ethyl group, exhibited lower aﬃnity for

PBRs than methyl (7-005) and ethyl (7-062) com-

pounds, as phenyl (7-070) and triﬂuoromethyl (7-071)

compounds exhibited lower aﬃnity for PBRs than

methyl (7-005) and ethyl (7-062) compounds. More

interestingly, bulky alkyl groups such as isopropyl and

cyclic alkyl compounds yielded lower PBR aﬃnity than

straight-chain alkyl compounds (7-064 versus 7-063, 7-

068 versus 7-065, 7-069 versus 7-066). Furthermore,

cyclic propyl compound 7-067 exhibited higher aﬃnity

for PBRs than isopropyl compound 7-064. These ﬁnd-

ings suggest that R¹exhibits a steric restriction and that

methyl and ethyl groups yield high aﬃnity for PBRs.

Among substituents at the 5-position, the order of PBR

aﬃnity was methyl (7-090: IC₅₀=0.34 nM) ꢁﬂuoro (7-

083: IC₅₀=0.79 nM) ꢁchloro (7-087: IC₅₀=2.0

nM)=5-triﬂuoromethyl (7-091: IC₅₀=2.2 nM) >5-

methoxy (7-092: IC₅₀=8.1 nM)> >carbamoyl (7-093:

IC₅₀>100 nM)=sulfamoyl (7-094: IC₅₀>100 nM) com-

pound. These ﬁndings suggest that the sterically accep-

table space on the benzene ring for interaction with PBR

is very narrow, and in particular that interaction between

PBR and ligand is hindered by hydrophilic substituents.

3.5. Combined chemical modiﬁcation

Compound 7-095 (IC₅₀=1.3 nM), in which a ﬂuorine

atom was introduced onto the 4-position (X¹) of 2,5-

dimethoxybenzyl compound 7-041, exhibited 15-fold

lower aﬃnity for PBRs than 7-041 (IC₅₀=0.085 nM). In

contrast, the corresponding 5-ﬂuoro compound 7-096

(DAA1106) exhibited high aﬃnity for PBRs with an

IC₅₀value of 0.28nM. The reason for this diﬀerence in

PBR aﬃnity is unclear, since 4-ﬂuoro compound 7-082

(IC₅₀=0.34 nM) exhibited slightly higher aﬃnity than

the 5-ﬂuoro compound 7-083 (IC₅₀=0.79 nM), in case

of the 2-methoxy compound (Ar¹), unlike the 2,5-dime-

thoxybenzyl compounds 7-095 and 7-096.

Similarly, compounds substituted with chloro- (7-072),

acetyloxy- (7-073), hydroxyl- (7-074), azido- (7-075) or

amino- (7-076) methyl group for R¹exhibited lower

aﬃnity for PBRs than the original compound 7-005.

Among them, aminomethyl compound 7-076 decreased

aﬃnity for PBRs markedly. It is possible that this

marked decrease depends on the basicity of amino

group, but this is unclear, since other amino compounds

have not been synthesized and evaluated.

Next, Ar¹and R¹of the 4-chloro compound 7-086 were

chemically modiﬁed. Conversion of the 2-methoxy-

benzyl group (Ar¹) in the 4-chloro compound 7-086

with 2-ethoxybenzyl (7-097), 2-propoxybenzyl (7-098),

2-isopropoxybenzyl (7-099, DAA1097) and 2,5-dime-

thoxybenzyl (7-100) groups did not markedly change

PBR aﬃnity, compared with 7-086. The propanoyl

(R¹=Et) compound 7-101 (IC₅₀=6.6 nM) exhibited 33-

fold lower aﬃnity for PBRs than acetyl compound

7-086 (IC₅₀=0.20 nM). Similarly, exchange of the 2-

methoxybenzyl group (Ar¹) in the 4-chloro compound

7-101 with 2-isopropoxybenzyl (7-104, IC₅₀=13 nM)

and 2,5-dimethoxybenzyl (7-105, IC₅₀=6.9 nM) groups

resulted in remarked decrease of PBR aﬃnity compared

with the corresponding acetyl compounds 7-099

(IC₅₀=0.92 nM) and 7-100 (IC₅₀=0.18nM), respec-

tively. However, 2-ethoxybenzyl (7-102, IC₅₀=0.93 nM)

and 2-propoxybenzyl (7-103, IC₅₀=1.1 nM) groups

slightly decreased PBR aﬃnity compared with the cor-

responding acetyl compounds 7-097 (IC₅₀=0.79 nM)

and 7-098 (IC₅₀=0.68nM), respectively. This vari-

ability might depend principally on the deference of

whole molecular conformation organized by substituent

of Ar¹and R¹. Furthermore, this decrease in PBR aﬃ-

nity might be slightly increased in magnitude by steric

hindrance by the chloro substituent, since introduction

of a chlorine atom onto the benzene ring slightly

decreased PBR aﬃnity (7-005 versus 7-086).

Urea compounds 7-077–7-079 exhibited lower aﬃnity

for PBRs than corresponding linear acyl compounds 7-

005, 7-062 and 7-064, respectively. Among them, com-

pounds 7-077 and 7-078 exhibited good aﬃnity for

PBRs, with IC₅₀values of 3.5 and 4.6 nM, respectively.

In contrast, urea compound 7-079 exhibited lower aﬃ-

nity (IC₅₀=100 nM) than 7-078. This low aﬃnity results

from more bulky dimethylamino group of 7-079 than

monomethylamino group of 7-078, as isopropyl com-

pound 7-064 exhibits about 38times lower aﬃnity for

PBRs than ethyl compound 7-062.

Carbamate compounds 7-080 and 7-081 exhibited high

aﬃnity for PBRs (IC₅₀=0.45 and 0.87 nM, respec-

tively), as the corresponding linear acyl compounds 7-

062 and 7-063 exhibited high aﬃnity for PBRs. The

PBR aﬃnity of carbamate compound 2 was higher than

that of the corresponding urea compound 7-078.

3.4. Chemical modiﬁcation of X¹

Introduction of

a

ﬂuoro, chloro, methyl, tri-

ﬂuoromethyl, carbamoyl or sulfamoyl group onto ben-

zene ring decreased PBR aﬃnity compared with the

original compound 7-005. Introduction of a ﬂuoro (7-

082–7-084), chloro (7-086, 7-087) or methyl (7-089, 7-

T. Okubo et al. / Bioorg. Med. Chem. 12 (2004) 423–438

431

Methyl, methoxy and ﬂuoro groups were introduced

5. Experimental

onto the 4-position of phenyl group (Ar²) of compounds

7-099 and 7-100, with the expectation that they would

exhibit the same PBR aﬃnity as the original two com-

pounds, since 4-methylphenyl (7-054, IC₅₀=0.12 nM),

4-methoxyphenyl (7-051, IC₅₀=0.16 nM) and 4-ﬂuoro-

phenyl (7-057, IC₅₀=0.29 nM) compounds exhibited

the same aﬃnity for PBRs as phenyl compound 7-005

(IC₅₀=0.15 nM). However, the PBR aﬃnities of 2-iso-

propoxy compounds 7-106–7-108 and 2,5-dimethoxy

compounds 7-109–7-111 were much lower than those of

the original 2-isopropoxy compound 7-099 and 2,5-

dimethoxy compound 7-100, respectively. Furthermore,

translation from the acetyl group (R¹) of compounds 7-

109–7-111 (IC₅₀=3.2, 6.7 and 3.3 nM, respectively) to a

N-methylcarbamoyl group (7-112–7-114, IC₅₀=2.2, 4.3

and 2.2 nM, respectively) yielded no signiﬁcant change

in PBR aﬃnity in sharp contrast to the diﬀerence in

PBR aﬃnity between acety compound 7-005

(IC₅₀=0.15 nM) and N-methylcarbamoyl 7-078

(IC₅₀=4.6 nM). These ﬁndings suggest that PBR aﬃ-

nity is aﬀected by overall molecular conformation

organized by the substituents of Ar¹and R¹and that

substituents of Ar²and X¹respond to conformations

acceptable for interaction with PBR.

Melting points were determined on a Yanaco MP-500D

melting point apparatus and were uncorrected. Proton

nuclear magnetic resonance (NMR) spectra were

obtained using a Varian Gemini 2000 (200 MHz). Che-

mical shifts are reported in parts per million relative to

tetramethylsilane as an internal standard. Several amide

compounds were a mixture of E and Z isomers caused

by the amide bond on NMR spectra. The ratio of E and

Z isomers is reported as following: 3.63 (3Hꢄ3/4, s),

3.78(3H ꢄ1/4, s). Mass spectra (MS) were obtained on a

Shimadzu Proﬁle (EI and CI), JEOL JMS-SX102 (FAB)

or Micromass Platform LC (IonSpray and ES). Ele-

mental analyses were performed by a Perkin–Elmer

2400 (carbon, hydrogen and nitrogen) or Yokogawa

IC7000P (halogen and sulfur). Analytical thin-layer

chromatography was conducted on precoated silica gel

60 F₂₅₄plates (Merck). Silica gel [C-200, 100–200 mesh

(Wako Pure Chemical)] was used for column chroma-

tography, using the solvent systems (volume ratios)

indicated below.

5.1. Method A: 5-ﬂuoro-2-phenoxyaniline (11-001)

A mixture of 2,5-diﬂuoronitrobenzene (46.4 g, 292

mmol), phenol (28.8 g, 306 mmol) and K₂CO₃(44.3 g,

321 mmol) in DMF (150 mL) was stirred at 75 ^ꢂC for 3

h. The mixture was concentrated in vacuo, and the

residue was partitioned between AcOEt and water. The

separated organic phase was washed with 1 M aqueous

NaOH, 1 M aqueous HCl, saturated aqueous NaHCO₃

and saturated brine, dried over Na₂SO₄, ﬁltered and

concentrated in vacuo. The residue was chromato-

graphed on silica gel (hexane/EtOAc 15:1) to obtain

5-ﬂuoro-2-phenoxynitrobenzene (67.3 g, 99% yield) as

yellow oil: NMR (CDCl₃) d 6.91–7.50 (7H, m), 7.71

(1H, dd, J=3.1, 7.7 Hz); MS (EI) m/z 233 (M⁺), 186

(M⁺ꢀ47, 100%).

3.6. Chemical modiﬁcation of Y

Introduction of a methyl group onto the methylene

group and conversion of methylene length (Y) of 7-005

was studied. Racemic compound 7-118, a compound in

which a methyl group was introduced onto the methyl-

ene group of 7-005, exhibited 15-fold lower aﬃnity than

7-005. This negative ﬁnding might have resulted from

steric hindrance of the introduced methyl group with

interaction with PBR or eﬀects on molecular con-

formation.

Furthermore, the shortened compound 8 and prolonged

compound 9 exhibited lower aﬃnity than the methylene

compound 7-005, with IC₅₀values of 9.8and 0.45 nM,

respectively. These ﬁndings suggest that the non-sub-

stituted methylene group is better than methylmethy-

lene, shortened and prolonged high-aﬃnity ligands for

PBRs.

A mixture of 5-ﬂuoro-2-phenoxynitrobenzene (23.3 g,

99.9 mmol) and PtO₂(200 mg) in MeOH (100 mL) was

stirred at 50 ^ꢂC for 4.5 h under a hydrogen atmosphere.

The mixture was ﬁltered through Celite. The ﬁltrate was

concentrated in vacuo and concentrated to yield 11-001

(19.6 g, 97% yield) as colorless oil: NMR (CDCl₃) d

3.88 (2H, br s), 6.40 (1H, ddd, J=3.1, 8.6, 8.6 Hz), 6.53

(1H, dd, J=3.1, 9.9 Hz), 6.84 (1H, dd, J=5.5, 8.6 Hz),

6.86–7.13 (3H, m), 7.21–7.40 (2H, m); MS (EI) m/z 203

(M⁺, 100%).

4. Conclusions

In this paper, we have reported the synthesis and SARs

of 2-aryloxyanilide derivatives, which were obtained by

ring-opening of Ro5-4864, as PBR ligands. Many 2-

aryloxyanilide derivatives exhibited remarkably high

aﬃnity and selectivity for PBRs over CBRs. This suc-

cessful design will have signiﬁcant eﬀects on the design

of new PBR ligands. Furthermore, 2-aryloxyanilide

derivatives can be used to probe the physiological func-

tional roles of PBR. Interesting results of pharmacolo-

gical studies utilizing typical compounds 7-096

(DAA1106) and 7-099 (DAA1097) have already been

published.^41ꢀ43Therefore, 7-096, 7-099 and other high-

aﬃnity compounds reported herein are useful for

examining the physiological functions of PBR.

This product was used in the next step without further

puriﬁcation.

5.2. Method B: 4-chloro-2-phenoxyaniline (11-002)

In a manner similar to the preparation of 5-ﬂuoro-2-

phenoxynitrobenzene in Method A, 4-chloro-2-phenoxy-

nitrobenzene (3.84 g, 51% yield) was obtained from 2,4-

dichloronitrobenzene (5.76 g, 30.0 mmol), 2-phenol

(2.83 g, 30.1 mmol) and K₂CO₃(4.56 g, 33.0 mol) in

DMF (30 mL) as a light yellow crystal: mp 84.0–84.5 ^ꢂC

(hexane/Et₂O); NMR (CDCl₃) d 6.95 (1H, d, J=2.2

432

T. Okubo et al. / Bioorg. Med. Chem. 12 (2004) 423–438

Hz), 7.02–7.33 (4H, m), 7.34–7.52 (2H, m), 7.94 (1H, d,

J=8.8 Hz); MS CI m/z 252 (M⁺+2), 250 (M⁺, 100%).

organic layer was washed with saturated aqueous

NaHCO₃and saturated brine, dried over Na₂SO₄, ﬁl-

tered and concentrated in vacuo. The residue was chro-

matographed on silica gel (hexane/AcOEt 4:1) to obtain

N-formyl-2-phenoxyaniline 12-002 (9.35 g, 80%) as a

pale brown crystal: mp 98–99 ^ꢂC; NMR (DMDO-d₆) d

6.82-7.50 (8H, m), 8.20–8.62 (2H, m); MS (EI) m/z 213

(M⁺, 100%).

A mixture of 4-chloro-2-phenoxynitrobenzene (3.70 g,

14.8mmol), powdered Fe (2.70 g, 4.83 atom) and

NH₄Cl (340 mg, 6.36 mmol) in a mixture of EtOH (20

mL) and water (8mL) was stirred at 85 ^ꢂC for 1 h. The

mixture was extracted with AcOEt, dried over Na₂SO₄,

ﬁltered and concentrated to yield 11-002 (3.09 g, 95%

yield) as colorless oil: NMR (CDCl₃) d 3.84 (2H, br s),

6.74 (1H, d, J=8.6 Hz), 6.83 (1H, d, J=2.4 Hz), 6.88–

7.46 (6H, m); MS (EI) m/z 221 (M⁺+2), 219 (M⁺,

100%).

To a cooled solution of 12-002 above (753 mg, 3.53

mmol) in dry DMF (13 mL) in an ice bath was added

NaH (60% dispersion in mineral oil, 169 mg, 4.23

mmol), and the mixture was stirred for 10 min. To the

solution was added dropwise 2-methoxybenzylchloride

(663 mg, 4.23 mmol). The mixture was stirred for 40

min at room temperature, poured into ice water and

then extracted with AcOEt three times. The combined

organic layer was washed with 0.5 M aqueous HCl

and saturated brine, dried over Na₂SO₄, ﬁltered and

concentrated in vacuo. The residue was chromato-

graphed on silica gel (hexane/AcOEt 4 : 1) to obtain 7-

061 as a colorless oil (823 mg, 70%): NMR (CDCl₃) d

3.63 (3Hꢄ3/4, s), 3.78(3H ꢄ1/4, s), 4.75 (2Hꢄ1/4, s),

4.99 (2Hꢄ3/4, s), 6.72–7.40 (13H, m), 8.35 (1Hꢄ3/4, s),

8.47 (3Hꢄ1/4, s); MS (CI) m/z 334 (M⁺+1), 121

(M⁺ꢀ212, 100%). Anal. (C₂₁H₁₉NO₃) C, H, N.

This product was used in the next step without further

puriﬁcation.

5.3. Method C: N-acetyl-N-(2-chlorobenzyl)-2-phenoxy-

aniline (7-008)

To a solution of 2-phenoxyaniline 11-003 (28.5 g, 154

mmol) and Et₃N (25.8mL, 185 mmol) in CH ₂Cl₂was

added dropwise AcCl (11.5 mL 162 mmol) under cool-

ing in an ice bath. After stirring at room temperature

for 1.5H, the reaction mixture was concentrated in

vacuo, and the residue was poured into water and

extracted with AcOEt three times. The combined

organic layer was washed with 0.5 M aqueous HCl,

saturated aqueous NaHCO₃and saturated brine, dried

over Na₂SO₄, ﬁltered and concentrated in vacuo. The

residue was chromatographed on silica gel (hexane/

EtOAc 4:1) to obtained N-acetyl-2-phenoxyaniline 12-

001 (33.7 g, 96% yield); mp 86–87 ^ꢂC; ¹H NMR

(CDCl₃) d 2.17 (3H, s), 6.84 (1H, dd, J=1.6, 7.9 Hz),

6.90–7.26 (5H, m), 7.27–7.49 (2H, m), 7.74 (1H, br s),

8.44 (1H, dd, J=1.3, 8.0 Hz); MS (ESI) m/z 250

(M⁺+Na, 100%).

5.5. Method E: N-acetyl-N-(2-isopropoxybenzyl)-2-phe-

noxyaniline (7-016)

A solution of 2-isopropoxybenzaldehyde (1.85 g, 11.3

mmol) and 2-phenoxyaniline 11-003 (1.85 g, 9.99 mmol)

in MeOH (10 mL) was stirred at room temperature for

0.5H, followed by cooling in an ice bath. To the cooled

mixture was added NaBH₄(1.50 g, 39.7 mol) in several

parts. The reaction mixture was stirred for 0.5 h with

cooling in an ice bath followed by stirring at room

temperature for 0.5 h. After adding dropwise 5% aqu-

eous AcOH (32 mL), the mixture was stirred at room

temperature for 10 min followed by extraction with

AcOEt three times. The combined organic layer was

washed with saturated aqueous NaHCO₃and saturated

brine, dried over Na₂SO₄, ﬁltered and concentrated in

vacuo. The residue was chromatographed on silica gel

(hexane/AcOEt 25:1) to obtain N-(2-isopropoxybenzyl)-

2-phenoxyanilne 13-001 (2.65 g, 80% yield) as an oil:

NMR (CDCl₃) d 1.29 (6H, d, J=6.1 Hz), 4.30–4.42

(2H, m), 4.43–4.63 (1H, m), 4.65–4.92 (1H, m), 6.55–

6.70 (1H, m), 6.72–7.39 (12H, m); MS (ESI) m/z (M⁺

+Na, 100%).

To a suspension of NaH (60% dispersion in mineral oil,

400 mg, 10.0 mmol) in dry DMF (30 mL) was added 12-

001 above (2.00 g, 8.80 mmol) and the mixture was

stirred for 0.5 h at room temperature. To the mixture

was added 2-chlorobenzylchloride (1.64 g, 10.2 mmol),

and the reaction mixture was stirred for 0.5 h at room

temperature. The mixture was poured into ice water and

extracted with Et₂O three times. The combined organic

layer was washed with 0.5 M aqueous HCl, saturated

aqueous NaHCO₃and saturated brine, dried over

Na₂SO₄, ﬁltered and concentrated in vacuo. The residue

was chromatographed on silica gel (hexane/AcOEt 4:1)

to obtain 7-008 (2.92 g, 94% yield) as an colorless oil;

NMR (CDCl₃) d 1.97 (3H, s), 4.81 (1H, d, J=15.0 Hz),

5.29 (1H, d, J=15.0 Hz), 6.84–7.53 (13H, m) ; MS (EI)

m/z 353 (M⁺+2), 351 (M⁺), 316 (M⁺ꢀ35, 100%).

Anal. (C₂₁H₁₈ClNO₂) C, H, N.

To a solution of 13-001 above (2.65 g, 7.95 mmol) and

Et₃N (1.5 mL, 10.8mmol) in THF (30 mL) was added

AcCl (0.80 mL, 11.3 mmol). After stirring at room

temperature for 0.5H, the reaction mixture was poured

into water and extracted with AcOEt three times. The

combined organic layer was washed with 0.5 M aqueous

HCl, saturated aqueous NaHCO₃and saturated brine,

dried over Na₂SO₄, ﬁltered and concentrated in vacuo.

The residue was chromatographed on silica gel (hexane/

AcOEt 4:1) to obtain 7-016 (2.65 g, 89% yield) as an oil;

NMR (CDCl₃) d 1.09 (3H, d, J=7.0 Hz), 1.17 (3H, d,

J=7.0 Hz), 1.93 (3H, s), 4.26–4.45 (1H, m), 4.69 (1H, d,

5.4. Method D: N-formyl-N-(2-methoxybenzyl)-2-phen-

oxyaniline (7-061)

A solution of 11-001 (10.1 g, 54.6 mmol) and formic

acid (6.1 mL, 107 mmol) in toluene (30 mL) was heated

at reﬂux for 8h. The reaction mixture was partitioned

between AcOEt and 0.5 M aqueous HCl. The separated

T. Okubo et al. / Bioorg. Med. Chem. 12 (2004) 423–438

433

J=14.5 Hz), 5.17 (1H, d, J=14.5 Hz), 6.71–7.40 (13H,

m) ; MS (EI) m/z 376 (M⁺+1), 149 (M⁺- 226, 100%).

Anal. (C₂₄H₂₅NO₃) C, H, N.

7-078 as a colorless crystal: mp 133.0–134.0 ^ꢂC; NMR

(CDCl₃) d 2.74 (3H, s), 3.60 (3H, s), 4.30 (1H, brs), 4.89

(2H, s), 6.68–7.50 (13H, m); MS (CI) m/z 363 (M⁺+1,

100%). Anal. (C₂₂H₂₂N₂O₃) C, H, N.

5.6. Method F: N-acetyl-N-(2,4-dimethoxybenzyl)-2-phe-

noxyaniline (7-040)

5.8. Method H: N-(aminocarbonyl)-N-(2-methoxy-

benzyl)-2-phenoxyaniline (7-077)

A suspension of 2-phenoxyaniline 11-003 (3.70 g, 20.0

mmol), 2,4-dimethoxybenzaldehyde (3.70 g, 22.3 mmol)

and PtO₂(70 mg) in MeOH (60 mL) was stirred overnight

under a hydrogen atmosphere. The resulting precipitate

was dissolved by addition of CHCl₃(30 mL) and then the

catalyst was removed by ﬁltration through Celite. The

ﬁltrate was concentrated in vacuo. The residual solid was

recrystallized from MeOH to obtain N-(2,4-dimethoxy-

benzyl)-2-phenoxyaniline 13-002 (5.06 g, 76% yield) as a

colorless amorphous: NMR (CDCl₃) d 3.69 (3H, m), 3.78

(3H, m), 4.29 (2H, d, J=6.2 Hz), 4.64 (1H, br t, J=6.2

Hz), 6.35–6.44 (2H, m), 6.56–6.69 (1H, m), 6.73–7.36

(9H, m); MS (ESI) m/z 358(M ⁺+Na, 100%).

To a solution of 13-003 (1.54 g, 5.04 mmol) in HOAc

(20 mL) was added dropwise a solution of KNCO (1.23

g, 15.1 mmol) in water (10 mL), and the mixture was

stirred at room temperature for 2.5 h. The reaction

mixture was poured into water and extracted with

AcOEt three times. The combined organic layer was

washed with saturated aqueous NaHCO₃and saturated

brine, dried over Na₂SO₄, ﬁltered and concentrated in

vacuo. The residue was chromatographed on silica gel

(hexane/AcOEt 3:1) followed by recrystallization from

AcOEt to obtain 7-077 (1.69 g, 96%): mp 89.5–90.0 ^ꢂC;

NMR (CDCl₃) d 3.63 (3H, s), 4.44 (2H, brs), 4.90 (2H,

brs), 6.74–7.42 (13H, m); MS (EI) m/z 348(M ⁺), 121

(M⁺ꢀ227, 100%). Anal. (C₂₁H₂₀N₂O₃) C, H, N.

To a solution of 13-002 above (1.00 g, 2.98mmol) in

pyridine (1.18g, 14.9 mmol) was added acetic anhydride

(0.76 g, 7.44 mmol). After stirring at room temperature

overnight, the reaction mixture was poured into water

and extracted with AcOEt three times. The combined

organic layer was washed with 0.5 M aqueous HCl,

saturated aqueous NaHCO₃and saturated brine, dried

over Na₂SO₄, ﬁltered and concentrated in vacuo. The

residue was chromatographed on silica gel (hexane/

AcOEt 3:1) to obtain 7-040 (1.09 g, 97%) as a colorless

oil: NMR (CDCl₃) d 1.92 (3H, s), 3.52 (3H, s), 3.76 (3H,

s), 4.65 (1H, d, J=14.4 Hz), 5.09 (1H, d, J=14.4 Hz),

6.28(1H, d, J=2.4 Hz), 6.35 (1H, dd, J=2.4, 8.4 Hz),

6.83–7.36 (10H, m); MS (EI) m/z 377 (M⁺), 151

(M⁺ꢀ226, 100%). Anal. (C₂₃H₂₃NO₄) C, H, N.

5.9. Method I: N-(2-methoxybenzyl)-N-methoxy-

carbonyl-2-phenoxyaniline (7-080)

To a solution of triphosgene (775 mg, 2.61 mmol) in

CH₂Cl₂(14 mL) was added dropwise a solution of 13-

003 (2.16 g, 7.07 mmol) and diisopropylethylamine (1.10

g, 8.48 mmol) in CH₂Cl₂(25 mL), and the mixture was

stirred at room temperature for 15 min. The reaction

mixture was concentrated in vacuo, and the residue was

partitioned between AcOEt and 5% aqueous HCl. The

separated organic layer was washed with saturated

aqueous NaHCO₃and saturated brine, dried over

Na₂SO₄, ﬁltered and concentrated in vacuo. The residue

was chromatographed on silica gel (hexane/AcOEt 15:1)

to obtain N-chlorocarbonyl-N-(2-methoxybenzyl)-2-

phenoxyaniline (2.57 g, 99%) as a colorless solid: NMR

(CDCl₃) d 3.63 (3H, s), 4.75 (1H, d, J=14.0 Hz), 5.15

(1H, d, J=14.0 Hz), 6.71–7.46 (13H, m); MS (FAB) m/z

368(M ⁺+1), 121 (M⁺ꢀ246, 100%).

5.7. Method G: N-(methoxybenzyl)-N-(methylamino-

carbonyl)-2-phenoxyaniline (7-078)

In a manner similar to the preparation of 13-001 in

Method E, N-(2-methoxybenzyl)-2-phenoxyanilne 13-

003 (13.4 g, 80% yield) was obtained from 2-metho-

benzaldehyde (7.44 g, 54.7 mmol), 2-phenoxyaniline 11-

003 (10.14 g, 54.7 mmol) and NaBH₄(2.07 g, 54.7 mmol)

as a colorless crystal: mp 48–49 ^ꢂC; NMR (CDCl₃) d 3.74

(3H, s), 4.37 (2H, s), 4.73 (1H, brs), 6.52–7.39 (13H, m);

MS (ESI) m/z 328(M ⁺+Na, 100%).

To a solution of sodium methoxide (215 mg, 3.98mmol)

in THF (5 mL) was added dropwise a solution of

N-chlorocarbonyl-N-(2-methoxybenzyl)-2-phenoxyaniline

(1.22 g, 3.32 mmol) in THF (5 mL) with cooling in an

ice bath, and the mixture was stirred at room temper-

ature for 20 min. The mixture was concentrated in vacuo

and the residue was partitioned between AcOEt and 5%

aqueous HCl. The separated organic layer was washed

with saturated aqueous NaHCO₃and saturated brine,

dried over Na₂SO₄, ﬁltered and concentrated in vacuo.

The residue was chromatographed on silica gel (hexane/

AcOEt 6:1) to obtain 7-080 (1.18g, 98%) as a colorless

oil: NMR (CDCl₃) d 3.58(3H, s), 3.63 (3H, s), 4.82 (2H,

brs), 6.75–7.42 (13H, m); MS (EI) m/z 363 (M⁺), 121

(M⁺ꢀ242, 100%). Anal. (C₂₂H₂₁NO₄) C, H, N.

To a solution of triphosgene (751 mg, 2.53mmol) in

CH₂Cl₂(14 mL) was added dropwise a solution of 13-

003 above (2.03 g, 6.65 mmol) and diisopropylethyl-

amine (1.03 g, 7.98mmol) in CH Cl₂(25 mL), and the

2

mixture was stirred at room temperature for 5 min. Into

the mixture was blown an excess amount of methyl-

amine, and the resulting mixture was stirred at room

temperature for 5 min. After concentration in vacuo,

the reaction mixture was concentrated in vacuo and

partitioned between AcOEt and water. The separated

organic layer was washed with 5% aqueous HCl, satu-

rated aqueous NaHCO₃and saturated brine, dried over

Na₂SO₄, ﬁltered and concentrated in vacuo. The resi-

dual solid was recrystallized from AcOEt to obtain

5.10. Method J: N-acetyl-N-(2-formylbenzyl)-2-phenoxy-

aniline (7-028)

In a manner similar to the preparation of 7-008 in

434

T. Okubo et al. / Bioorg. Med. Chem. 12 (2004) 423–438

Method C, N-acetyl-N-[2-(1,3-dioxolanyl)benzyl]-2-

phenoxyaniline (7-115) (2.94 g, 77%) was obtained from

2-([1,3]dioxolan-2-yl)benzylchloride (1.94 g, 9.77 mmol),

N-acetyl-2-phenoxyaniline (2.20 g, 9.77 mmol) and NaH

(60% dispersion in mineral oil, 430 mg, 10.8mmol) as a

light yellow oil: NMR (CDCl₃) d 1.94 (3H, s), 3.90–4.14

(4H, m), 4.61 (1H, d, J=14.7 Hz), 5.55 (1H, d, J=14.7

Hz), 5.87 (1H, s), 6.91–6.99 (5H, m), 7.08–7.40 (7H, m),

7.50–7.62 (1H, m),; MS (FAB) m/z 390 (M⁺+1), 286

(M⁺ꢀ103, 100%) . Anal. (C₂₄H₂₃NO₄) C, H, N.

was stirred at 0 ^ꢂC for 20 min. After the addition of

saturated aqueous NH₄Cl, the mixture was extracted

with EtOAc three times. The combined organic layer

was washed with saturated brine, dried over Na₂SO₄,

ﬁltered and concentrated in vacuo. The residue was

chromatographed on silica gel (hexane/AcOEt 1:1) and

recrystallized from AcOEt/hexane to obtain 7-029 (911

mg, 68%): mp 110.0–110.50 ^ꢂC; NMR (CDCl₃) d 1.99

(3H, s), 2.35 (3H, s), 5.13 (1H, d, J=15.6 Hz), 5.38(1H, d,

J=15.6 Hz), 6.80–7.75 (13H, m); MS (EI) m/z 359 (M⁺),

316 (M⁺ꢀ43, 100%). Anal. (C₂₃H₂₁NO₃) C, H, N.

A solution of N-acetyl-N-[2-(1,3-dioxolan-2-yl)benzyl]-

2-phenoxyaniline (2.75 g, 7.06 mmol) and p-toluene-

sulfonic acid monohydrate (0.10 g, 0.53 mmol) in

acetone (40 mL) was stirred at room temperature for 6

h. To the mixture was added saturated aqueous

NaHCO₃solution, and the mixture was concentrated in

vacuo to remove acetone. The residual mixture was

extracted with AcOEt three times. The combined

organic layer was washed with water and saturated brine,

dried over Na₂SO₄, ﬁltered and concentrated in vacuo.

The residue was chromatographed on silica gel (hexane/

AcOEt 3:1) to obtain 7-028 (2.12 g, 85%) as a pale yellow

crystal: mp 114.0–117.0 ^ꢂC; NMR (CDCl₃) d 1.99 (3H,

s), 5.31 (1H, d, J=15.6 Hz), 5.45 (1H, d, J=15.6 Hz),

6.73–7.88 (13H, m), 10.12 (1H, s); MS (FAB) m/z 346

(M⁺+1, 100%) . Anal. (C₂₂H₁₉NO₃) C, H, N.

5.13. Method M: N-acetyl-N-(2-vinylbenzyl)-2-phenoxy-

aniline (7-027)

Under a nitrogen atmosphere, to a suspension of

methyltriphenylphosphonium bromide (2.54 g, 7.11

mmol) in dry THF (10 mL) cooled to ꢀ15 ^ꢂC 1.63 M

n-butyllithium in hexane (3.60 mL, 5.93 mmol) was

added dropwise to maintain the reaction temperature at

ꢀ15 to ꢀ10 ^ꢂC. The mixture was warmed to room tem-

perature gradually, and stirred for 20 min. To the mix-

ture was added dropwise a solution of 7-028 (820 mg,

2.37 mmol) in THF (5 mL), and the mixture was stirred

at room temperature for 1 h. To the mixture was

added saturated aqueous NH₄Cl, and the mixture

obtained was extracted with AcOEt three times. The

combined organic layer was washed with brine, dried

over Na₂SO₄, ﬁltered and concentrated in vacuo. The

residue was chromatographed on silica gel (hexane/

AcOEt 4:1) to obtain 7-027 (697 mg, 86%) as a colorless

oil: NMR (CDCl₃) d 1.93 (3H, s), 4.67 (1H, d, J=14.5

Hz), 5.22 (1H, dd, J=1.5, 10.8Hz), 5.35 (1H, d, J=14.5

Hz), 5.51 (1H, dd, J=1.5, 17.4 Hz), 6.80–7.44 (14H, m);

MS (EI) m/z 343 (M⁺), 117 (M⁺ꢀ226, 100%). Anal.

(C₂₃H₂₁NO₂) C, H, N.

5.11. Method K: N-acetyl-N-[2-(1-hydroxyethyl)benzyl]-

2-phenoxyaniline (7-030)

To a 0.26 M solution of methyl magnesium bromide in

THF (20.3 mL) was added a solution of 7-028 (1.20 g,

3.47 mmol) in THF (7.0 mL). After stirring at room

temperature for 1H, saturated aqueous NH₄Cl was

added to the reaction mixture with cooling in an ice

bath, and the mixture was extracted with AcOEt. The

combined organic layer was washed with saturated

brine, dried over Na₂SO₄, ﬁltered and concentrated in

vacuo. The residue was chromatographed on silica gel

(hexane/AcOEt 1:1) to obtain 7-030 (1.19 g, 95%) as an

light yellow oil: NMR (CDCl₃) d 1.34 (3Hꢄ1/2, d,

J=6.2 Hz), 1.40 (3Hꢄ1/2, d, J=6.2 Hz), 1.93 (3Hꢄ1/2,

s), 1.97 (3Hꢄ1/2, s), 4.87 (1Hꢄ1/2, d, J=13.0 Hz),

4.967 (1Hꢄ1/2, d, J=13.0 Hz), 5.10 (1Hꢄ1/2, d,

J=13.0 Hz), 519 (1Hꢄ1/2, d, J=13.0 Hz), 6.60–7.51

(13H, m) ; MS (EI) m/z 361 (M⁺), 117 (M⁺ꢀ244,

100%). Anal. (C₂₃H₂₃₉NO₃) C, H, N.

5.14. Method N: N-acetyl-N-(2-propylbenzyl)-2-phenoxy-

aniline (7-026)

In a manner similar to the preparation of 7-027 in

Method M, N-acetyl-N-(2-(1-prop-1-enyl)benzyl)-2-

phenoxyanilne (7-116) (859 mg, 83%) was obtained by

treatment of 7-028 (1.01 g, 2.92 mmol) with triphenyl-

propylidene-l⁵-phosphane prepared by treatment of

ethyltriphenyl-phosphonium bromide (4.34 g, 11.7

mmol) with 1.63 M n-butyllithium in hexane (6.6 mL,

10.8mmol) as a light yellow oil. This product was a

mixture of geometrical isomers (the ratio 3:2) and was

used in the next step without further puriﬁcation on

silica gel chromatography.

5.12. Method L: N-acetyl-N-(2-acetylbenzyl)-2-phenoxy-

aniline (7-029)

A solution of oxalyl chloride (0.64 mL, 7.3 mmol) in dry

CH₂Cl₂(40 mL) was cooled to-78 ^ꢂC. To the solution

was added dropwise a solution of DMSO (0.78mL, 11.0

mmol) in dry CH₂Cl₂(7.6 mL). The mixture was stirred

at ꢀ78 ^ꢂC for 10 min, and then to the solution was

added dropwise a solution of 7-030 (1.35 g, 3.74mmol)

in dry CH₂Cl₂(13 mL). After stirring at ꢀ78 ^ꢂC for 15

min, the temperature of the reaction mixture was gra-

dually increased to ꢀ45 ^ꢂC, followed by stirring at that

temperature for 1 h. To the mixture was added dropwise

Et₃N (3.9 mL, 28.0 mmol) at ꢀ45 ^ꢂC and the mixture

5.14.1. Crude 7-116. NMR (CDCl₃) d 1.50–1.63 (3Hꢄ3/

5, m), 1.75–1.84 (3Hꢄ2/5, m), 1.90–1.993 (3H, m), 4.57

(1Hꢄ3/5, d, J=14.5 Hz), 4.62 (1Hꢄ2/5, d, J=14.5 Hz),

5.25 (1Hꢄ3/5, d, J=14.5 Hz), 5.33 (1Hꢄ2/5, d, J=14.5

Hz), 5.62–6.05 (1H, m), 6.22–6.38(1H ꢄ3/5, m), 6.47–

6.62 (1Hꢄ2/5, m), 6.73–7.40 (13H, m); MS (ESI) m/z

380 (M⁺+Na, 100%).

A suspension of the above crude mixture of geometrical

isomers (the ratio 3:2) 7-116 (757 mg, 2.12 mmol) and

PtO₂(15 mg, 0.066 mmol) in EtOH (7.0 mL) was stirred

T. Okubo et al. / Bioorg. Med. Chem. 12 (2004) 423–438

435

under a hydrogen atmosphere at room temperature for

3 h. The catalyst was removed by ﬁltration through

Celite, and the ﬁltrate was concentrated in vacuo. The

residue was chromatographed on silica gel (hexane/

AcOEt 4:1) to obtain 7-026 (647 mg, 85%) as a colorless

oil: NMR (CDCl₃) d 0.89 (3H, t, J=7.3 Hz), 1.37–1.55

(2H, m), 1.96 (3H, s), 2.42–2.51 (2H, m), 4.68(1H, d,

J=14.5 Hz), 5.20 (1H, d, J=14.5 Hz), 6.81–7.37 (13H,

m); MS (SI) m/z 360 (M⁺+1, 100%). Anal.

(C₂₄H₂₅NO₂) C, H, N.

Method F, N-acetyl-N-(2-methoxycarbonylbenzyl)-2-

phenoxyaniline (7-032) (2.44 g, 92% yield) was obtained

by acetylation of N-(2-methoxycarbonylbenzyl)-2-phe-

noxyanilne (2.34 g, 7.02 mmol) yielded (3.75 g, 64%

yield) by treatment of 2-methoxycarbonylbenzaldehyde

(2.91 g, 17.7 mmol) and 2-phenoxyaniline 11-003 (3.28

g, 17.7 mmol) on PtO₂(60 mg) under a hydrogen

atmosphere, as a colorless crystal: mp 76.0–78.0 ^ꢂC;

NMR (CDCl₃) d 1.98(3H, s), 3.71 (3H, s), 5.19 (1H, d,

J=15.4 Hz), 5.51 (1H, d, J=15.4 Hz), 6.83–7.43 (11H,

m), 7.64 (1H, dd, J=0.9, 7.7 Hz), 7.79 (1H, dd, J=1.4,

7.7 Hz); MS (EI) m/z 375 (M⁺), (333⁺ꢀ42, 100%).

Anal. (C₂₃H₂₁NO₄) C, H, N.

5.15. Method O: N-acetyl-N-(2-aminobenzyl)-2-phenoxy-

aniline (7-037)

In a manner similar to the preparation of 7-016 in

Method C, N-acetyl-N-(2-nitrobenzyl)-2-phenoxyanilne

(7-036) (9.09 g, 71% yield) was obtained by treatment of

12-001 (8.00 g, 35.2 mmol), which was yielded in

Method E, with 2-nitrobenzylchloride (11.4 g, 52.8

mmol) in the presence of NaH (60% dispersion in

mineral oil, 2.12 g, 53.0 mmol) in dry DMF (80 mL), as

a yellow crystal: mp 96.0–96.5 ^ꢂC; NMR (CDCl₃) d 2.04

(3H, s), 5.18(1H, d, J=16.2 Hz), 5.39 (1H, d, J=16.2

Hz), 6.82–7.56 (11H, m), 7.73–7.96 (2H, m); MS (ESI)

m/z 385(M⁺+23, 100%). Anal. (C₂₁H₁₈N₂O₄) C, H, N.

A mixture of 7-032 (2.26 g, 6.02 mmol) and 2 M aqu-

eous KOH (3.6 mL, 7.2 mmol) in MeOH (23 mL) was

heated at 60 ^ꢂC for 1 h. The reaction mixture was con-

centrated in vacuo, and the residue was chromato-

graphed on silica gel (hexane/AcOEt 1:1) to obtain 7-

033 (2.01 g, 92%) as a colorless oil: NMR (CDCl₃) d

1.99 (3H, s), 4.93 (1H, d, J=15.4 Hz), 5.29 (1H, d,

J=15.4 Hz), 6.92–7.47 (11H, m), 7.56–7.60 (1H, m),

7.82–7.87 (1H, m); MS (FAB) m/z 362 (M⁺+1, 100%).

Anal. (C₂₂H₁₉NO₄) C, H, N.

5.18. Method R: N-acetyl-N-(2-dimethylaminocarbo-

nylbenzyl)-2-phenoxyanilne (7-035)

A suspension of 7-036 (8.00 g, 22.1 mmol) and PtO₂(66

mg, 0.29 mmol) was stirred under a hydrogen atmos-

phere at room temperature overnight. After dissolving

the precipitate by addition of CHCl₃(40 mL), the cata-

lyst was removed by ﬁltration. The ﬁltrate was con-

centrated in vacuo and the residual solid was

recrystallized from MeOH to obtain 7-037 (6.88 g,

94%): mp 155.5–156 ^ꢂC; NMR (CDCl₃) d 1.94 (3H, s),

4.62 (1H, d, J=14.5 Hz), 4.40–4.80 (2H, m), 6.36–7.42

(13H, m); MS (ESI) m/z 355 (M⁺+Na, 100%). Anal.

(C₂₁H₂₀N₂O₂) C, H, N.

To a solution of 7-033 (500 mg, 1.39 mmol) and HMPA

(0.1 mL, 0.57 mmol) in THF (10 mL) was added SOCl₂

(0.2 mL, 2.74 mmol), and the mixture was stirred at

room temperature for 3 h. The reaction mixture was

concentrated in vacuo, and the residue was dissolved in

THF (10.0 mL). To the solution was added dropwise

50% aqueous Me₂NH (2.0 mL, 22.2 mmol), and the

mixture was stirred at room temperature for 1 h. The

reaction mixture was partitioned between AcOEt and

1 M aqueous HCl, and the separated water layer was

extracted with AcOEt twice. The combined organic

layer was washed with saturated brine, dried over

Na₂SO₄, ﬁltered and concentrated in vacuo. The residue

was chromatographed on silica gel (hexane/AcOEt 3:1)

to obtain 7-035 (490 mg, 91%) as an oil: NMR (CDCl₃)

d 1.96 (3H, s), 2.62 (3H, s), 3.01 (3H, s), 4.57 (1H, d,

J=15.0 Hz), 5.26 (1H, d, J=15.0 Hz), 6.79–7.48(13H,

m); MS (EI) m/z 388 (M⁺), 300 (M⁺ꢀ88, 100%). Anal.

(C₂₄H₂₄N₂O₃) C, H, N.

5.16. Method P: N-acetyl-N-(2-pyrrolidinobenzyl)-2-phe-

noxyanilne hydrochloride (7-038)

A mixture of 7-037 (1.00 g, 3.01 mmol), 1,4-dibromo-

butane (680 mg, 3.15 mmol), K₂CO₃(1.03 g, 7.45 mmol)

and KI (50 mg, 0.30 mmol) in DMF (10 mL) was heated

at 70 ^ꢂC for 3 days. The reaction mixture was parti-

tioned between AcOEt and water. The separated

organic layer was washed with water and saturated

brine, dried over Na₂SO₄, ﬁltered and concentrated in

vacuo. The residue was chromatographed on silica gel

(hexane/AcOEt 3:1), and the puriﬁed product was trea-

ted with 4 M HCl in AcOEt (0.9 mL) in Et₂O (5 mL)

followed by recrystallization from AcOEt/Et₂O to

obtain 7-038 (490 mg, 39%): mp 110.0–112.5 ^ꢂC; NMR

(CDCl₃) d 2.30 (3H, m), 2.18–2.52 (4H, m), 3.22–4.32

(4H, m), 5.23 (1H, d, J=15.6 Hz), 5.46 (1H, d, J=15.6

Hz), 6.72–6.90 (3H, m), 7.06–7.61 (9H, m), 7.70–7.83

(1H, m), 12.98(1H, brs); MS (ESI) m/z 409 (M⁺+Na,

5.19. Method S: N-acetoxyacetyl-N-(2-methoxybenzyl)-

2-phenoxyanilne (7-073)

In a manner similar to the preparation of 7-016 in

Method E, N-chloroacetyl-N-(2-methoxybenzyl)-2-phe-

noxyanilne (7-072) (2.96 g, 77% yield) was obtained by

treatment of N-(2-methoxybenzyl)-2-phenoxyanilne 13-

003 (3.05 g, 10.0 mmol) with chloroacetyl chloride (3.42

g, 20 mmol) in pyridine (10 mL, 123 mmol) as a colorless

crystal: mp 83.0–83.5 ^ꢂC; NMR (CDCl₃) d 3.57 (3H, s),

3.97 (2H, s), 4.76 (1H, d, J=14.3 Hz), 5.20 (1H, d,

J=14.3 Hz), 6.66–7.43 (13H, m); MS (EI) m/z 381 (M⁺),

91 (M⁺ꢀ290, 100%). Anal. (C₂₂H₂₀ClNO₃) C, H, N.

.

100%). Anal. (C₂₅H₂₆N₂O₂HCl) C, H, N.

5.17. Method Q: N-acetyl-N-(2-carboxybenzyl)-2-phe-

noxyanilne (7-033)

In a manner similar to the preparation of 7-040 in

A mixture of 7-072 (1.01 g, 2.64 mmol), AcONa (1.30 g,

436

T. Okubo et al. / Bioorg. Med. Chem. 12 (2004) 423–438

15.8mmol) and tetrabutyl ammonium bromide (170

mg, 0.527 mmol) in benzene (10 mL) was heated at

80 ^ꢂC for 5 h. The reaction mixture was partitioned

between AcOEt and water, and the separated organic

layer was washed with water and saturated brine, dried

over Na₂SO₄, ﬁltered and concentrated in vacuo. The

residue was chromatographed on silica gel (hexane/

AcOEt 3:1) to obtain 7-073 (1.03 g, 96%) as a colorless

oil: NMR (CDCl₃) d 2.15 (3H, s), 3.58(3H, s), 4.46 (1H,

d, J=14.8Hz), 4.59 (1H, d, J=14.8Hz), 4.74 (1H, d,

J=14.5 Hz), 5.16 (1H, d, J=14.5 Hz), 6.71–7.38(13H,

m); MS (EI) m/z 405 (M⁺), 121 (M⁺ꢀ284, 100%).

Anal. (C₂₄H₂₃NO₅) C, H, N.

m); MS (FAB) m/z 363 (M⁺+1, 100%). Anal.

(C₂₂H₂₂N₂O₃) C, H, N.

5.23. Method W: N-acetyl-N-(2-hydroxybenzyl)-2-phe-

noxyaniline (7-022)

Unpuriﬁed

N-acetyl-N-(2-acetoxybenzyl)-2-phenoxy-

aniline (7-117), which was obtained by treatment of a

mixture of 2-acetoxybenzaldehyde (1.74 g, 10.6 mmol)

and 2-phenoxyaniline 11-003 (1.85 g, 10.0 mmol) with

NaBH₄(3.00 g, 79.3 mmol) in MeOH (30 mL) followed

by acetylchloride (2.00 mL, 28.1 mmol) in the presence

of Et₃N (4.0 mL, 28.7 mmol) in CH₂Cl₂(50 mL) in a

manner similar to the preparation of 7-016 in Method

C, was treated with 5% aqueous KOH (14 mL) in

MeOH (40 mL) at room temperature for 1 h. The mix-

ture was concentrated in vacuo, poured into water and

extracted with AcOEt three times. The combined

organic layer was washed with 0.5 M aqueous HCl,

saturated aqueous NaHCO₃and saturated brine, dried

over Na₂SO₄, ﬁltered, concentrated in vacuo and crys-

tallized from diisopropylether to obtain 7-022 (1.86 g,

56%) as a light yellow crystal: mp 123.0–124.5 ^ꢂC;

NMR (CDCl₃) d 1.95 (3H, s), 4.50 (1H, d, J=14.5 Hz),

4.98(1H, d, J=14.5 Hz), 6.60–7.42 (13H, m), 9.54 (1H,

s); MS (FAB) m/z 334 (M⁺+1, 100%). Anal.

(C₂₁H₁₉NO₂) C, H, N.

5.20. Method T: N-Hydroxyacethyl-N-(2-methoxy-

benzyl)-2-phenoxyaniline (7-074)

A mixture of 7-073 (525 mg, 1.30 mmol), K₂CO₃(537

mg, 3.89 mmol) in MeOH (6.0 mL) was stirred at 50 ^ꢂC

for 7 h. The reaction mixture was poured into water and

extracted with AcOEt three times. The combined

organic layer was washed with 5% aqueous HCl, satu-

rated aqueous NaHCO₃and saturated brine, dried over

Na₂SO₄, ﬁltered and concentrated in vacuo. The residue

was chromatographed on silica gel (hexane/AcOEt 3:1)

to obtain 7-074 (450 mg, 96%) as a colorless crystal: mp

70.0–71.0 ^ꢂC; NMR (CDCl₃) d 3.41 (1H, t, J=4.8Hz),

3.59 (3H, s), 3.89–3.95 (2H, m), 4.76 (1H, d, J=14.3

Hz), 5.24 (1H, d, J=14.3 Hz), 6.73–7.39 (13H, m); MS

(FAB) m/z 364 (M⁺+1), 121 (M⁺ꢀ243, 100%). Anal.

(C₂₂H₂₁NO₄) C, H, N.

5.24. Method X: N-acetyl-N-(2-carboxymethoxybenzyl)-

2-phenoxyaniline (7-020)

To a solution of 7-022 (666 mg, 2.00 mol) in dry DMF

(10 mL) was added NaH (60% dispersion in mineral oil,

80 mg, 2.00 mmol), and the mixture was stirred at room

temperature for 0.5 h. To the mixture was added methyl

bromoacetate (0.30 mL, 3.20 mmol), and the mixture

was stirred at room temperature for 0.5 h. The reaction

mixture was poured into 0.5 M aqueous HCl solution,

and extracted with AcOEt three times. The combined

organic layer was washed with saturated aqueous

NaHCO₃and saturated brine, dried over Na₂SO₄, ﬁl-

tered and concentrated in vacuo.

5.21. Method U: N-azidoacetyl-N-(2-methoxybenzyl)-2-

phenoxyaniline (7-075)

A mixture of 7-072 (1.51 g, 3.95 mmol) and sodium

azide (770 mg, 11.9 mmol) in DMF (10 mL) was stirred

at room temperature overnight. The reaction mixture

was poured into water and extracted with AcOEt three

times. The combined organic layer was washed with 5%

aqueous HCl, saturated aqueous NaHCO₃and satu-

rated brine, dried over Na₂SO₄, ﬁltered and con-

centrated in vacuo. The residue was chromatographed

on silica gel (hexane/AcOEt 3:1) to obtain 7-075 (1.55 g,

100%) as an colorless oil: NMR (CDCl₃) d 3.56 (3H, s),

3.64 (1H, d, J=15.9 Hz), 3.76 (1H, d, J=15.9 Hz), 4.78

(1H, d, J=14.2 Hz), 5.18(1H, d, J=14.2 Hz), 6.71–7.40

(13H, m); MS (EI) m/z 388 (M⁺), 121 (M⁺ꢀ267,

100%). Anal. (C₂₂H₂₀N₄O₃) C, H, N.

A mixture of the above residue and 5% aqueous KOH

(5.0 mL) in MeOH (10.0 mL) was stirred at room tem-

perature for 1 h. The reaction mixture was acidiﬁed by

addition of 2 M aqueous HCl (pH 2) and extracted with

AcOEt. The combined organic layer was washed

with saturated brine, dried over Na₂SO₄, ﬁltered and

concentrated in vacuo. The residue was crystallized

from diisopropylether to obtain 7-020 (745 mg, 95%):

mp 156.5–157.0 ^ꢂC; NMR (CDCl₃) d 1.96 (3H, s), 4.35

(1H, d, J=14.5 Hz), 4.57 (1H, d, J=14.5 Hz), 4.84 (1H,

d, J=14.0 Hz), 5.22 (1H, d, J=14.0 Hz), 6.52–6.88 (6H,

m), 6.93–7.35 (7H, m); MS (FAB) m/z 392 (M⁺+1,

100%). Anal. (C₂₃H₂₁NO₅) C, H, N.

5.22. Method V: N-aminoacetyl-N-(2-methoxybenzyl)-2-

phenoxyanilne (7-076)

A mixture of 7-075 (647 mg, 1.67 mmol) and PtO₂(20

mg) in MeOH (7.0 mL) was stirred under a hydrogen

atmosphere at room temperature overnight. The mix-

ture was ﬁltered through Celite, and the ﬁltrate was

concentrated in vacuo. The residue was chromato-

graphed on silica gel (hexane/AcOEt 6:1) and recrys-

tallized from AcOEt diisopropylether to obtain 7-076

(240 mg, 40%) as a colorless crystal: mp 85.0–86.0 ^ꢂC;

NMR (CDCl₃) d 3.21 (2H, s), 3.58(3H, s), 4.73 (1H, d,

J=14.4 Hz), 5.20 (1H, d, J=14.4 Hz), 6.70–7.41 (13H,

5.25. Method Y: N-acetyl-N-(2-methoxyphenyl)-2-phe-

noxyaniline (8)

A mixture of 12-001 (2.27 g, 10.0 mmol), 2-methoxy-

iodobenzene (1.3 mL, 10.0 mmol), K₂CO₃(1.38g, 10.0

mmol), copper powder (133 mg, 2.09 mmol) and CuBr

T. Okubo et al. / Bioorg. Med. Chem. 12 (2004) 423–438

437

(200 mg, 1.39 mmol) in nitrobenzene (20 mL) was

5.27. Binding study

heated at reﬂux for 8h. After addition of EtOAc, the

precipitate was ﬁltered oﬀ and the ﬁltrate was washed

with 0.5 M aqueous HCl, saturated aqueous NaHCO₃

and saturated brine, dried over Na₂SO₄, ﬁltered and

concentrated in vacuo. The residue was chromato-

graphed on silica gel (hexane/AcOEt 4:1) to obtain 8

(660 mg, 23%) as an light yellow oil: NMR (CDCl₃) d

1.97 (3Hꢄ2/3, s), 2.13 (3Hꢄ1/3, s), 3.98(3H, s), 6.80–

7.62 (13H, m) ; MS (EI) m/z 333 (M⁺), 291 (M⁺ꢀ42,

100%). Anal. (C₂₁H₁₉NO₃) C, H, N.

5.27.1. PBR. Preparation of mitochondria was as fol-

lows: Rata were decapitated, the whole brain rapidly

removed and the cerebral cortex homogenized in 10

volumes of 10 mM HEPES buﬀer (pH 7.4) containing

0.32 M sucrose, using a Teﬂon homogenizer, then cen-

trifuged at 900g for 5 min. The supernatant was cen-

trifuged at 12,000g for 10 min. The pellet (crude

mitochondrial fraction) was washed with 50 mM

HEPES buﬀer (pH 7.4) once, and suspended in

50 mM HEPES buﬀer (pH 7.4) at the protein concen-

tration of 0.3 mg/mL. The crude mitochondrial pre-

paration (1 mL) was incubated with [³H]-PK11195 for

90 min at 4 ^ꢂC, and the reaction was stopped by rapid

ﬁltration through a GF/B glass ﬁlter presoaked with

0.3% polyethyleneimine, after which the ﬁlters were

washed three times with 3 mL of the buﬀer. The radio-

activity was quantiﬁed in a liquid scintillation spectro-

meter. Nonspeciﬁc binding was determined in the

presence of 10 mM PK11195. The speciﬁc binding was

determined by subtracting nonspeciﬁc from total binding.

5.26. Method Z: N-acetyl-N-[2-(2-methoxyphenyl)ethyl]-

2-phenoxyaniline (9)

To a solution of 2-methoxyphenylacetic acid (4.98g,

30.0 mmol) and DMF (0.5 mL) in toluene (30 mL) was

added SOCl₂(4.00 mL, 54.8mmol), and the mixture

was stirred at 70 ^ꢂC for 1 h. The mixture was con-

centrated in vacuo and the residue was dissolved in

CH₂Cl₂(20 mL). The solution was added dropwise to

a solution of 2-phenoxyaniline 11-003 (5.55 g, 30.0

mmol) and triethylamine (4.6 mL, 33.0 mmol) in

CH₂Cl₂(30 mL). The reaction mixture was stirred at

room temperature for 1 h and concentrated in vacuo.

The residue was partitioned between ice water AcOEt.

The separated water phase was extracted with AcOEt

twice. The combined organic phase was washed with

0.5M aqueous HCl, saturated aqueous NaHCO₃and

saturated brine, dried over Na₂SO₄, ﬁltered and con-

centrated in vacuo. The residue was dissolved in dry

THF (40 mL) and the solution was added dropwise to a

suspension of LiAlH₄(1.70 g, 44.8mmol) in dry THF

(40 mL). The mixture was heated at reﬂux for 0.5 h and

then cooled in an ice bath. To the cooled mixture

was added dropwise saturated aqueous Na₂SO₄, and

the resulting precipitate was ﬁltered through MgSO₄

plate prepared from its powdered anhydrate. The

ﬁltrate was concentrated in vacuo and chromato-

graphed on silica gel (hexane/AcOEt 10:1) to obtain

N-[2-(2-methoxyphenyl)ethyl]-2-phenoxyaniline 14 (8.23

g, 86%) as an oil: NMR (CDCl₃) d 2.83–3.02 (2H, m),

3.26–3.49 (2H, m), 3.77 (3H, s), 4.49 (1H, brs), 6.51–

7.40 (13H, m); MS (ESI) m/z 320 (M⁺+1), 135

(M⁺ꢀ184, 100%).

5.27.2. CBR. Rata were decapitated, the whole brain

rapidly removed and the cerebral cortex was homo-

genized with 50 mM potassium phosphate buﬀer (pH

7.4), then centrifuged at 500g for 5 min. The super-

natant was centrifuged at 48,000g for 20 min, and the

pellet was washed once with the buﬀer. The ﬁnal pellet,

suspended in 50 mM potassium phosphate buﬀer (pH

7.4) at the protein concentration of 0.4 mg/mL was used

as a crude membrane preparation. The membrane pre-

paration (1 mL) was incubated with [³H]ﬂunitrazepam

(2 nM) for 1 h at 4 ^ꢂC, and the reaction was stopped by

rapid ﬁltration through a GF/B glass ﬁlter presoaked

with 0.3% polyethyleneimine, after which the ﬁlters

were washed three times with 3 mL of the buﬀer. The

radioactivity was quantiﬁed in a liquid scintillation

spectrometer. Nonspeciﬁc binding was determined in

the presence of 10 mM diazepam. The speciﬁc binding

was determined by subtracting nonspeciﬁc from total

binding.

Acknowledgements

To a solution of 14 (3.19 g, 10.0 mmol) and Et₃N (1.5

mL, 10.8mmol) in CH Cl₂(30 mL) was added AcCl

A part of synthetic research was carried out by M.

Nagamine, K. Harada, K. Yamamoto and Dr. M.

Yoshida (Research Division of Nihon Nohyaku Co.,

Ltd.). We wish to express our special thanks to them.

2

(0.80 mL, 11.3 mmol) with cooling in an ice bath. After

stirring at room temperature for 0.5H, the reaction

mixture was concentrated in vacuo. The residue was

partitioned between Et₂O water and the separated water

layer was extracted with Et₂O twice. The combined

organic layer was washed with 0.5 M aqueous HCl,

saturated aqueous NaHCO₃and saturated brine, dried

over Na₂SO₄, ﬁltered and concentrated in vacuo. The

residue was chromatographed on silica gel (hexane/

AcOEt 4:1) and crystallized from hexane to obtain 9

(2.64 g, 73%) as a colorless crystal: mp 79.0–80.0 ^ꢂC;

NMR (CDCl₃) d 1.90 (3H, s), 2.80–3.05 (2H, m), 3.56–

3.87 (1H, m), 3.71 (3H, s), 3.97–4.16 (1H, m), 6.73–7.42

(13H, m),; MS (SI) m/z 362 (M⁺+1, 100%). Anal.

(C₂₃H₂₃NO₃) C, H, N.

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Article Doi

Design, synthesis and structure-affinity relationships of aryloxyanilide derivatives as novel peripheral benzodiazepine receptor ligands

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