Development of fluorinated CB2 receptor agonists for PET studies

Bioorganic & Medicinal Chemistry 21 (2013) 7481–7498

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Bioorganic & Medicinal Chemistry

journal homepage: w ww.elsevier.com/locate/bmc

Development of ﬂuorinated CB₂receptor agonists for PET studies

Corinna Lueg ^a, Dirk Schepmann ^a, Robert Günther ^b, Peter Brust ^b, Bernhard Wünsch ^a,

⇑

^aInstitut für Pharmazeutische und Medizinische Chemie der Universität Münster, Corrensstraße 48, D-48149 Münster, Germany

^bHelmholtz-Zentrum Dresden-Rossendorf, Institut für Radiopharmazeutische Krebsforschung Forschungsstelle Leipzig, Abteilung Neuroradiopharmaka, Permoserstraße 15, D-04318

Leipzig, Germany

a r t i c l e i n f o

a b s t r a c t

Article history:

A convergent strategy was followed to modify systematically carbazole based CB₂receptor ligands. The

length of the N-(ﬂuoroalkyl) group (n in 7), the length of the alkanamide (m in 7) and the substitution

pattern of the phenyl moiety (X and Y in 7) were varied systematically. The highest CB₂afﬁnity was found

for the 2-ﬂuoroethyl substituted carbazole derivative 20a (K_i= 5.8 nM) containing the propionamide and

the 2-bromo-4-ﬂuorophenyl moiety. According to docking studies 20a ﬁts nicely into the binding pocket

of the CB₂receptor, but elongation of the ﬂuoroethyl side chain leads to a different binding mode of the

ligands. The high CB₂afﬁnity together with the high selectivity over the CB₂subtype qualiﬁes the ﬂuoro-

ethyl derivative 20a to be developed as a PET tracer.

Received 5 August 2013

Revised 12 September 2013

Accepted 16 September 2013

Available online 24 September 2013

Keywords:

CB₂receptor ligands

Carbazole derivatives

Fluorinated ligands

Structure afﬁnity relationships

PET

Docking

1. Introduction

which are devoid of psychotropic side effects mediated by the acti-

vation of CB₁receptors.^19–21Whereas the CB₂receptor expression

For centuries, Cannabis sativa was used as a medicinal plant

suppressing pain and inﬂammation. In the 1930s, tetrahydrocan-

nabinol (THC) and later on more than 60 different cannabinoids

were isolated and characterized.^1,2THC and its analogs led to the

identiﬁcation of the endocannabinoid system consisting of the

endogenous ligands anandamide (N-arachidonyl ethanolamine,

AEA)³and 2-O-arachidonylglycerol (2-AG),⁴which are agonists of

the G-protein coupled cannabinoid CB₁and CB₂receptors. Further-

more the enzymes, which are responsible for the biosynthesis (e.g.,

N-acyltransferase, phosphodiesterase D, diacylglycerol lipase) and

deactivation of endocannabinoids (e.g., fatty acid amide hydrolase,

monoacylglycerol lipase) belong to the endocannabinoid system.^5,6

For a long time the CB₂receptor was regarded as the ‘peripheral’

CB receptor, since the CB₂receptor is mainly expressed by hemato-

poietic cells, where its expression level is almost 100 times higher

than the expression level of the CB₁receptor.^7,8An important func-

tion of the CB₂receptor in the immune system is the regulation

and release of cytokines which play a key role in inﬂammatory pro-

cesses and immune response.⁹

in the CNS of healthy men is very low, an increased amount of CB₂

receptors is expressed as reaction on inﬂammatory stimuli.^22–25

Many neurodegenerative disorders like Alzheimer’s dis-

ease,^15,26,27multiple sclerosis,⁷Chorea Hungtington as well as

depression²⁵and schizophrenia²⁵are linked to neuroinﬂammation,

which is associated with an elevated CB₂receptor expression.^9,28–

31

Moreover, apoptosis of some tumor cells was stimulated by

CB₂receptor agonists.^32,33Regarding the role of CB₂receptors in

the regulation of neuronal cell proliferation, in neurodegenerative

and neuroinﬂammatory processes, CB₂receptor stimulation by

agonists could lead to reduction of neuroinﬂammation and stimu-

lation of neurogenesis.

Imaging of CB₂receptors by positron emission tomography

(PET) could be used to determine the current state of CB₂receptor

expression in the CNS, which will serve as biomarker for the judge-

ment of the therapeutic success in the ﬁght against neurodegener-

ative and neuroinﬂammatory processes.

During the PET tracer development many aspects have to be

considered in parallel. The ligand should bind with high afﬁnity

and selectivity at CB₂receptors. An intermediate lipophilicity is

required as very lipophilic ligands show very poor solubility

and stick in membranes. On the other hand very polar com-

pounds are not able to pass the blood-brain barrier and cannot

reach the CNS.³⁴Generally 18-ﬂuorine labeled tracers are pre-

ferred over 11-carbon labeled ligands due to the relatively long

half-life of 110 min of 18-ﬂuorine compared with 20 min of

11-carbon.

However, during the last decades it was shown that the CB₂

receptor is also expressed in the CNS, microglia, neurons and neu-

ronal stem cells.^10–14It has a regulatory function on the prolifera-

tion and survival of neurons.^15–18This discovery led to an

increasing interest in the development of selective CB₂ligands,

⇑

Corresponding author. Tel.: +49 251 8333311; fax: +49 251 8332144.

E-mail address: wuensch@uni-muenster.de (B. Wünsch).

http://dx.doi.org/10.1016/j.bmc.2013.09.040

7482

C. Lueg et al. / Bioorg. Med. Chem. 21 (2013) 7481–7498

In the literature only few PET tracer candidates for imaging of

CH₃

CB₂receptors are reported, which are summarized in Figure 1.

The quinolin-2-one 1 shows high CB₂afﬁnity (K_i= 2.8 nM) and

excellent selectivity over the CB₁subtype. However, the radio-

chemical yields obtained after introduction of 18-ﬂuorine into

the phenyl moiety of 1 did not exceed 12%. Moreover, the very poor

solubility of 1 inhibits the in vivo application.^35,36Introduction of

N

NC

O

F

N

H

O

N

6

F

the [¹⁸F]2-ﬂuoroethyl moiety led to rather low CB₂afﬁnity of the

( )_n

11-

inverse CB₂agonist 2a (K_i= 36 nM). The corresponding

[

N

X

C]methoxy derivative 2b reveals a reasonable afﬁnity towards

the CB₂receptor (K_i= 9.6 nM). Both tracers were rapidly metabo-

lized in plasma leaving 41% of [¹⁸F]tracer 2a and 24% of [¹¹C]tracer

2b unchanged after 10 min.³⁷The 11-carbon labeled tracer 2b

showed in a ﬁrst study with healthy humans the expected uptake

in lymphoid tissues and appropriate brain kinetics.³⁸The bissulf-

one 3 represents a promising candidate with afﬁnities towards

the human CB₁and CB₂receptor of 79 and 4.5 nM, respectively

(Fig. 1). Although the logP value of 3 is in a favorable range

(logP = 2.15), the brain uptake was very low. The high activity of

efﬂux transporters at the blood–brain barrier might explain the

low penetration of 3 into the central nervous system.³⁸In 2011

the 18-ﬂuorine-labeled indole derivative 4a was reported showing

moderate afﬁnity towards the human CB₂receptor, moderate brain

uptake in mice and a considerable fraction of radiometabolites in

the brain.⁴⁰Compared to the ﬂuoroethyl derivative 4a, the corre-

sponding 11-carbon labeled compound 4b has very similar CB₂

receptor afﬁnity and selectivity over the CB₁subtype. Both indole

derivatives have a low stability in vivo and radiometabolites were

trapped in the brain.^41,42Very high CB₂afﬁnity and selectivity of

the thiazole derivative 5 was reported. The 11-carbon labeled

derivative showed speciﬁc cerebral uptake in a mouse model of

neuroinﬂammation. However, the high lipophilicity of 5 led to rel-

atively high non-speciﬁc binding.^43,44Although the [¹¹C]methyl

ethers 2b, 4b and 5 show promising properties, we aim at the

development of 18-ﬂuorine labeled PET tracers with a longer

half-life of the radioisotope, which is easier to handle and does

not require a cyclotron on-site.

O

Y

N

( )_m

N

H

O

N

7

Figure 2. CB₂receptor agonist 6 reported by Cheng et al.⁴⁵and designed ﬂuorinated

CB₂ligands 7.

In this work we aim at the synthesis of ﬂuorinated CB₂recep-

tor ligands, which can be developed into a [¹⁸F]ﬂuorinated PET-

tracer for imaging of CB₂receptors in the brain. The starting

point of the project is the CB₂receptor agonist 6 reported by

Cheng et al.⁴⁵(Fig. 2). Whereas Whereas only functional data

are given in the original manuscript showing the CB₂agonistic

activity of 6, the afﬁnity towards the human CB receptors was

reported by Rühl et al. (K_i(CB₂) = 6.98 nM, K_i(CB₁) >10 l

M).⁵³

The ethyl side chain at the carbazole moiety will be used for

the introduction of a ﬂuorine atom. In order to identify the best

ﬂuorinated CB₂ligand for labeling with 18-ﬂuorine, a large set of

diverse ﬂuoroalkyl substituted carbazole derivatives 7 will be

synthesized and relationships between the structure and the

CB₂afﬁnity will be elaborated. In particular the ﬂuoroalkyl side

chain at the carbazole ring will be varied from ﬂuoroethyl

(n = 1) to ﬂuorobutyl (n = 3), the length of the alkanamide will be

varied from propionamide (m = 1) to butyramide (m = 2) and the

substitution pattern of the phenyl residue will be modiﬁed by

introduction of various substituents in different positions X and Y.

O

N

H

N

H

N

H

H₃CO

O

N

H

¹⁸F

RO

O

OBu

: R = ¹⁸FCH₂CH₂

2b: R = ¹¹CH₃

K_i(hCB₁) > 1 µM

K_i(hCB₂) = 9.6 nM

1

2a

K_i(hCB₁) >10 µM

K_i(hCB₂) = 2.8 nM

K_i(hCB₁) > 1 µM

K_i(hCB₂) = 36 nM

O

N

H₃C

NHSO₂CH₃

O¹¹CH₃

RO

H₃C

N

S

H₃C

CH₃

O

N

O

SO₂

O

¹¹CH₃

H₃CO

SO₂

CH₃

Cl

: R = ¹⁸FCH₂CH₂

K_i(hCB₁) > 10 µM

K_i(hCB₂) = 27 nM

5

: R = ¹¹CH₃

4b

K_i(hCB₁) = 6 µM

K_i(hCB₂) = 35 nM

3

4a

K_i(hCB₁) = 270 nM

K_i(hCB₂) = 0.64 nM

K_i(hCB₁) = 79 nM

K_i(hCB₂) = 4.5 nM

Figure 1. PET tracer candidates for imaging of CB₂receptors.

C. Lueg et al. / Bioorg. Med. Chem. 21 (2013) 7481–7498

7483

carbazoles 20–24 using the ﬂuorinating agent diet-

hylaminodiﬂuorosulﬁnium tetraﬂuoroborate (Et₂N@SF₂–BF₄, Xtal-

Fluor-E^Ò).⁵⁰After addition of NEt₃Á3HF to the reaction mixture,

the ﬂuorinated compounds 20–24 were isolated in 4–91% yields.

This synthesis led to a diverse set of ﬂuorinated CB₂ligands 20–

24, which differ in the chain length (n) of the ﬂuoroalkyl residue,

the length (m) of the alkanamide and the substitution pattern (X,

Y) of the phenyl moiety. Moreover, the corresponding alcohols

15–19 displaying a higher polarity than the ﬂuoro derivatives

20–24 were also included into the cannabinoid receptor binding

assays.

2. Synthesis

The synthesis of the ﬂuorinated carbazole derivatives 7 was

performed according to a convergent strategy, that is, various

hydroxyalkyl-substituted carbazolamines 12–14 were reacted

with different oxadiazolylalkanoic acids 9 and 11 to yield a diverse

set of coupling products 15–19 (Scheme 2).

The hydroxalkyl substituent of the carbazole derivatives 12–14

was introduced upon hydroxyalkylation of carbazole with cyclic

sulfates⁴⁶(ethylene sulfate, trimethylene sulfate) or 1,4-dibromo-

butane and subsequent substitution with NaOH as key step. Nitra-

tion, reduction and precipitation as HCl salt led to the homologous

series of hydroxyalkyl substituted carbazolamines 12–14.⁴⁷

The 1,2,4-oxadiazolylpropionic acids 9a–e were prepared

according to a literature procedure.⁴⁵Addition of hydroxylamine

to various benzonitriles 8a–e afforded the corresponding amidox-

imes, which were transformed with succinic anhydride into the

propionic acids 9a–e. (Scheme 1) For the synthesis of the nitrile

9f the bromobenzene 9a was heated with methanol and H₂SO₄

to obtain the ester 10a. A Rosenmund-von Braun reaction⁴⁵with

CuCN in boiling dimethylacetamide converted the bromobenzene

10a into the cyanobenzene 10f, which was subsequently hydro-

lyzed with LiOH to yield the propionic acid 9f.

The homologous butyric acids 11a–d were prepared according

to the same strategy. Reaction of the benzonitriles 8a–d with

hydroxylamine led to the intermediate amide oximes, which upon

treatment with glutaric anhydride in boiling dimethylformamide

provided the butyric acids 11a–d in 42–56% yield (Scheme 1).

Different coupling reagents (EDC, HATU) were investigated for

the reaction of the carbazolamines 12–14 with the alkanoic acids

9 and 11 (Scheme 2). It was found that the uronium salt COMU^Ò

(1-cyano-2-ethoxy-2-oxoethylidenaminooxy)dimethylamino-

morpholino-_carbenium hexaﬂuorophosphate)^48,49gave the highest

yields of amides and therefore COMU^Òwas used as standard

reagent for the preparation of all coupling products 15–19. The

alcohols 15–19 were transformed into the ﬂuoroalkyl substituted

3. Receptor afﬁnity

The CB₂receptor afﬁnity of the carbazole derivatives 15–24 was

determined in competition experiments with the radioligand

[³H]CP-55,940.^51,52The receptor material was obtained from

Table 1

CB₂receptor afﬁnity of carbazole derivatives 15–24

R

n

N

X

O

Y

N

H

m

O

N

15-24

.

Compd.

R

n

1

m

1

X

Y

K_iSEM (nM)

15a

15b

15c

15d

15e

15f

16a

16b

16c

16d

17a

18a

18b

18c

18d

19a

19b

19c

19d

20a

20b

20c

20d

20e

20f

21a

21b

21c

21d

22a

23a

23b

23c

23d

24a

24b

24c

24d

CP 55,940

WIN 55,212

HU 210

OH

Br

H

F

CN

Br

H

Br

H

Br

H

Br

H

F

CN

Br

H

Br

H

Br

H

F

Cl

CH₃

Br

F

Cl

CH₃

F

Cl

CH₃

F

367

1100

990

10%^a

35%^a

486

OH

2

1

33 1.1

195 45

—

OH

28%^a

96 29

0%^a

X

O

n

Y

OH

3

1

2

N

HO

12%^a

584

m

O

N

4%^a

HCl

NH₂

9a-f

9%^a

12-14

OH

F

2

1

2

1

11a-d

F

19%^a

10%^a

13%^a

5.8 2.4

41 15

291 57

377

(a)

O

Cl

CH₃

F

OH

F

Cl

CH₃

Br

F

Cl

CH₃

F

Cl

CH₃

F

Cl

CH₃

n

N

476

858

X

Y

N

H

F

2

1

1800

10%^a

43%^a

13%^a

35%^a

559

m

O

N

15-19

(b)

F

3

1

2

F

25%^a

23%^a

0%^a

25%

0%

—

0%

27 6.0

70 27

18 5.0

n

N

X

F

2

O

Y

N

H

m

H

O

N

20-24

Scheme 2. Reagents and reaction conditions: (a) 9a–f or 11a–d, NEt₃, COMU^Ò, then

addition of 12, 13 or 14, DMF, <10 °C, 35–85%. (b) 15–19, XtalFluor-E^Ò(Et₂N@SF₂–

BF₄), NEt₃Á3HF, CH₂Cl₂, À78 °C, rt, 3 h, 4–91%.

a

Inhibition (%) of the radioligand binding at a concentration of the test com-

pound of 1 M.

l

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C. Lueg et al. / Bioorg. Med. Chem. 21 (2013) 7481–7498

(d)

X

O

(b)

(a)

F

Y

N

H₃CO

HO

O

N

10a

10f

X

Y

9a-f

(c)

NC

8-11

8a-e

X

Y

a

b

c

d

e

f

Br

H

F

X

F

Y

HO

N

O

H

Cl

(e)

O

H

CH₃

Br

F

N

F

11a-d

CN

Scheme 1. Reagents and reaction conditions: (a) (1) NH₂OH–HCl, Na₂CO₃, H₂O, rt, 25 min, then addition of 8a–e, CH₃OH, 65 °C; (2) succinic anhydride, DMF, 148 °C, 30 min,

30–80%. (b) 9a, CH₃OH, concd H₂SO₄, 45 min, reﬂux. (c) CuCN, DMA, 18.5 h, 155 °C. (d) 10f, LiOH, THF/H₂O (3:1), 1 h, rt, 65%. (e) (1) NH₂OH–HCl, Na₂CO₃, H₂O, rt, 25 min, then

addition of 8a–d, CH₃OH, 86 °C; (2) glutaric anhydride, DMF, 148 °C, 30 min, 42–56%.

recombinant CHO cells expressing the human CB₂receptor in large

amounts. The non-speciﬁc binding of the radioligand was recorded

in the presence of a large amount (10 lM) of non-labeled CP-

55,940. The CB₂afﬁnity of compounds showing higher afﬁnity than

200 nM in the ﬁrst experiment were repeated twice and the mean

value of three experiments are given in Table 1. The CB₁afﬁnity of

the most potent CB₂ligands was determined in order to prove the

selectivity over this subtype.

Transformation of the alcohols into the corresponding

ﬂuoroalkyl derivatives led to increased CB₂receptor afﬁnity.

Generally the 2-ﬂuoroethyl derivatives 20 display higher CB₂afﬁnity

than the corresponding 3-ﬂuoropropyl (21) and 4-ﬂuorobutyl

(22) homologs. Elongation of the spacer between the carbazole

system and the 1,2,4-oxadiazole ring afforded the butyramides

23 and 24 (m = 2) with considerably reduced CB₂receptor

afﬁnity.

The alcohols 15–19 show a considerably lower CB₂afﬁnity than

the corresponding ﬂuoro substituted compounds 20–24. As a gen-

eral trend the hydroxypropyl substituted derivatives 16 have high-

er CB₂afﬁnity than the corresponding hydroxyethyl substituted

derivatives 15 (e.g., 15a/16a, 15b/16b). A further extension of the

carbazole substituent to a hydroxybutyl side chain (17a, K_i= 96

nM) led to slight reduction of the CB₂afﬁnity. Extension of the pro-

pionamides 15, 16 to butyramides 18, 19 led to an almost complete

loss of the CB₂receptor afﬁnity. Within this series of alcohols 15–

19 the propionamide 16a (m = 1) with a 3-hydroxypropyl side

chain (n = 2) at the carbazole system and the 2-bromo-4-ﬂuoro

substitution pattern at the phenyl ring revealed the strongest

interactions with the CB₂receptor.

The substitution pattern of the phenyl moiety at the 1,2,4-oxa-

diazole ring has a strong inﬂuence on the CB₂afﬁnity. The 4-ﬂuo-

rophenyl substituted compound 20b possesses a CB₂afﬁnity of

41 nM. Replacement of the ﬂuorine atom with a chlorine atom

(20c) or a methyl moiety (18d) led to reduced CB₂afﬁnity. An addi-

tional large substituent in 2-position as in the 2-bromophenyl

derivative 20a increased the CB₂afﬁnity to 5.8 nM. Obviously

two substituents attached to the phenyl moiety (i.e., a ﬂuorine

atom in 4-position and a large substituent in 2-position) appear

to be favorable for high CB₂afﬁnity. However, an unexpected

reduction of the CB₂afﬁnity was observed for 20e and 20f. Com-

pound 20e has the same but inverted substitution pattern (4-bro-

mo-2-ﬂuorophenyl residue) as the very potent CB₂ligand 20a and

Figure 3. Predicted binding modes of selected compounds to human CB₂receptors. (A) Binding mode of compounds 6 (grey) and 20a (cyan) after docking into the human CB₂

receptor binding pocket (indicated by dots). (B) Comparison of the binding modes of 6, 20a and 22a (yellow). The CB₂receptor is shown with the extracellular site up. This

ﬁgure was prepared with MOE (Chemical Computing Group Inc. Montreal, Canada).

C. Lueg et al. / Bioorg. Med. Chem. 21 (2013) 7481–7498

7485

the benzonitrile 20f represents the cyano analog of 20a as well as

the 2-ﬂuoroethyl analog of the lead compound 6.

5.0 lL; detection at k = 210 nm; solvents: A: water with 0.05% (v/

v) triﬂuoroacetic acid; B: acetonitrile with 0.05% (v/v) triﬂuoroace-

tic acid: gradient elution: (A%): 0–4 min: 90%, 4–29 min: gradient

from 90% to 0%, 29–31 min: 0%, 31–31.5 min: gradient from 0%

to 90%, 31.5–40 min: 90%.

In order to prove the selectivity the CB₁afﬁnity of the most

promising CB₂ligands 16a, 17a, 20a, 20b, and 20f was recorded

in receptor binding studies. It was shown that the CB₁afﬁnity of

these compounds was negligible (IC₅₀>1 l

M)⁵³indicating a very

high selectivity for the CB₂receptor over the CB₁receptor.

6.2. General procedures

4. Molecular modeling

6.2.1. General procedure A for the synthesis of 3-[(3-phenyl)-

1,2,4-oxadiazol-5-yl]propanoic acids 9⁴⁵(modiﬁed (solvent,

time, puriﬁcation) according to Ref. 45)

In order to gain more insight into the interaction of the com-

pounds with the CB₂receptor molecular docking studies were per-

formed. For this purpose, our recently published model of the

human CB₂receptor was used.⁵³The ﬂuoroethyl and ﬂuorobutyl

substituted compounds 20a and 22a were docked into the binding

site of the CB₂receptor to compare their interactions with the pro-

posed binding mode of the lead compound 6. Figure 3 shows that

the attachment of a ﬂuorine atom to the ethyl moiety has virtually

no impact on the binding geometry of the compound. This is in

excellent agreement with the measured afﬁnity data for the ethyl

derivative 6 (K_i= 4.3 nM)⁴⁵and the ﬂuoroethyl derivative 20a

(K_i= 5.8 nM).

Elongation of the alkyl chain leads to a drastic reduction of afﬁn-

ity, as shown in Table 1. The docking studies with the ﬂuorobutyl

derivative 22a suggest, that the longer chain results in a different

binding mode, which is illustrated in Figure 3B. The different bind-

ing mode might explain the reduced CB₂receptor afﬁnity.

Hydroxylamine hydrochloride (1.0 equiv) was dissolved in H₂O

(0.4 mL per mmol) and sodium carbonate (0.5 equiv) was added.

The mixture was stirred for 25 min at rt. A solution of the respective

benzonitrile 8 (1.0 equiv) in CH₃OH (1.8 mL per 1 mmol) was added

to the solution under vigorous stirring. The reaction mixture was

stirred at 65 °C until the starting material was converted. Then, CH_3-

OH was removed under reduced pressure, and the residue was di-

luted with brine and extracted with CH₂Cl₂until the product was

extracted completely. The organic layer was dried (Na₂SO₄) and re-

moved under reduced pressure. Afterwards, succinic anhydride

(0.9 equiv) and DMF (0.5 mL) were added to the residue and the

reaction mixture was stirred for 30 min at 148 °C. The solvent was

removed in vacuo and the residue was puriﬁed by fc (cyclohexane/

ethyl acetate/formic acid 50:50:0.01). The product was puriﬁed by

recrystallization (CH₂Cl₂/H₂O).

6.2.2. General procedure B for the synthesis of 3-[(3-phenyl)-

1,2,4-oxadiazol-5-yl]butanoic acids 11

5. Conclusion

Hydroxylamine hydrochloride (1.0 equiv) was dissolved in H₂O

(0.4 mL per mmol) and sodium carbonate (0.5 equiv) was added.

The mixture was stirred for 25 min at rt. A solution of the respec-

tive benzonitrile 8 (1.0 equiv) in CH₃OH (1.8 mL per 1 mmol) was

added to the solution under vigorous stirring. The reaction mixture

was stirred at 86 °C until the starting material was converted.

Then, CH₃OH was removed under reduced pressure and the residue

was diluted with brine and extracted with CH₂Cl₂until the product

was extracted completely. The organic layer was dried (Na₂SO₄)

and removed under reduced pressure. Afterwards, glutaric

anhydride (1.0 equiv) and DMF (0.5 mL) were added to the residue

and the reaction mixture was stirred for 30 min at 148 °C. The

solvent was removed in vacuo and the residue was puriﬁed by fc

(cyclohexane/ethyl acetate/formic acid 50:50:0.01). The product

was puriﬁed by recrystallization (CH₂Cl₂/H₂O).

A series of more than 30 carbazole based CB₂ligands was syn-

thesized and the afﬁnity towards the human CB₂receptor was re-

corded in receptor binding studies. The substitution pattern of the

phenyl ring is crucial for high CB₂afﬁnity. Elongation of the 2-ﬂu-

oroethyl side chain at the carbazole N-atom to a 3-ﬂuoropropyl

and 4-ﬂuorobutyl side chain (variation of n in 7) as well as elonga-

tion of the propionamide to a butyramide (variation of m in 7) lead

to a remarkable decrease of the CB₂afﬁnity. The high CB₂afﬁnity

(K_i= 5.8 nM) and CB₂over CB₁selectivity (>200) renders the ﬂu-

oroethyl derivative 20a a promising candidate for radiolabeling

with [¹⁸F]ﬂuorine for PET studies.

6. Experimental chemistry

6.1. Chemistry, general

6.2.3. General procedure C for the COMU^Ò-coupling of alkanoic

acids 9 and 11 with carbazole-3-amines 12–14

(1-Cyano-2-ethoxy-2-oxoethylidenaminooxy))dimethylamino-

morpholinecarbenioum hexaﬂuorophosphate (COMU^Ò, 1.2–

1.5 equiv) was added to a mixture of the respective 1,2,4-oxadiaz-

Unless otherwise noted, moisture sensitive reactions were con-

ducted under dry nitrogen. THF was dried with sodium/benzophe-

none and was freshly distilled before use. Thin layer

chromatography (tlc): Silica gel 60 F254 plates (Merck). Flash chro-

ole carboxylic acid

9 or 11 (1.0 equiv) and triethylamine

(2.0–3.0 equiv) in DMF, and the mixture was stirred for 30 min at

rt. The reaction mixture was cooled down to 0 °C and a solution

of the respective 3-aminocarbazole hydrochloride 12–14

(1.0 equiv) in DMF was added dropwise. This mixture was stirred

for 24 h at <10 °C. Then H₂O and brine were added and the mixture

was extracted with CHCl₃until the product was extracted com-

pletely. The combined organic layers were washed with brine,

dried (Na₂SO₄) and concentrated under reduced pressure. The res-

idue was puriﬁed by fc and ﬁnally by recrystallization with CH₂Cl₂.

matography (fc): Silica gel 60, 40–64 lm (Merck); parentheses in-

clude: diameter of the column, eluent, fraction size, R_fvalue.

Melting point: Melting point apparatus SMP 3 (Stuart Scientiﬁc),

uncorrected. MS: MAT GCQ (Thermo-Finnigan); EI = electron im-

pact, ESI = electro spray ionization: HRMS: MicroTof (Bruker Dal-

tronics, Bremen), calibration with sodium formate clusters before

measurement. IR: IR spectrophotometer 480Plus FT-ATR-IR (Jasco).

¹H NMR (400 MHz), ¹³C NMR (100 MHz): Unity Mercury Plus 400

spectrometer (Varian); d in ppm related to tetramethylsilane; cou-

pling constants are given with 0.5 Hz resolution. HPLC method for

determination of the product purity: Merck Hitachi Equipment; UV

detector: L-7400; autosampler: L-7200; pump: L-7100; degasser:

6.2.4. General procedure D for the ﬂuorination of the alcohols

15–19 with XtalFluor-E^Ò

L-7614; Method: column: LiChrospher^Ò60 RP-select B (5

250–4 mm cartridge; ﬂow rate: 1.00 mL/min; injection volume:

lm),

Under N₂, diethylaminodiﬂuorosulﬁnium tetraﬂuoroborate

(Et₂N@SF₂–BF₃, XtalFluor-E^Ò, 1.5–3.0 equiv) was suspended in

7486

C. Lueg et al. / Bioorg. Med. Chem. 21 (2013) 7481–7498

CH₂Cl₂. Triethylamine trihydroﬂuoride (1.5–3.0 equiv) and a solu-

tion of the respective alcohol 15–19 (1.0 equiv) in CH₂Cl₂were

added to the suspension via cannula at À78 °C. The resulting mix-

ture was warmed up to rt during 1 or 3 h. An aqueous solution of

Na₂CO₃(5% m/m) was added and the reaction mixture was stirred

for 15 min at rt. After addition of brine the mixture was extracted

with CH₂Cl₂until the product was extracted completely. The or-

ganic layer was dried (Na₂SO₄), the organic concentrated in vacuo,

the product was recrystallized from ethyl acetate.

6.3.3. Methyl 3-[3-(2-cyano-4-ﬂuorophenyl)-1,2,4-oxadiazol-5-

yl]propanoate (10f)⁴⁵

According to literature⁴⁵10a (500 mg, 1.3 mmol) and CuCN

(716 mg, 8.0 mmol) were suspended in N,N-dimethylacetamide

(5 mL) under N₂. The mixture was heated to 155 °C for 18.5 h. Sat-

urated NH₄Cl (4 mL) and ethyl acetate (16 mL) were added. The

precipitated CuCN was ﬁltered off and the ﬁltrate was washed once

with brine. The organic layer was dried (Na₂SO₄), concentrated un-

der reduced pressure and puriﬁed by fc (d = 8 cm, l = 14 cm, cyclo-

hexane/ethyl acetate 70:30, R_f0.50). Colorless solid, mp 80–82 °C,

yield 240 mg (65%). C₁₃H₁₀FN₃O₃(275.2 g/mol). Exact mass (APCI):

m/z = calcd for C₁₃H₁₀FN₃O₃H 276.0779 found 276.0769. Purity

(HPLC): 91.9% (t_R= 17.57 min). ¹H NMR (CDCl₃): d (ppm) = 2.96

(t, J = 7.1 Hz, 2H, CH₂CH₂CO₂CH₃), 3.31 (t, J = 7.1 Hz, 2H, CH₂CH_2-

CO₂CH₃), 3.73 (s, 3H, CH₂CH₂CO₂CH₃), 7.43 (ddd, J = 8.7/7.7/

2.6 Hz, 1H, 5-H), 7.54 (dd, J = 8.2/2.6 Hz, 1H, 3-H), 8.15 (dd,

J = 8.7/6.0 Hz, 1H, 6-H). ¹³C NMR (DMSO-d₆): d (ppm) = 21.6 (1C,

CH₂CH₂CO₂CH₃), 30.7 (1C, CH₂CH₂CO₂CH₃), 51.8 (1C, CH₂CH₂CO_2-

CH₃), 111.9 (d, J = 10.4 Hz, 1C, C-2), 116.1 (d, J = 2.6 Hz, 1C, CN),

121.6 (d, J = 21.9 Hz, 1C, C-5), 122.5 (d, J = 26.1 Hz, 1C, C-3), 125.0

(d, J = 3.6 Hz, 1C, C-1), 132.6 (d, J = 9.4 Hz, 1C, C-6), 162.9 (d,

J = 252.1 Hz, 1C, C-4), 165.0 (1C, C-5_oxadiazole), 171.7 (1C, CO₂CH₃),

6.3. Synthetic procedures

3-[3-(2-Bromo-4-ﬂuorophenyl)-1,2,4-oxadiazol-5-yl]propanoic

acid (9a)⁴⁵3-[3-(4-ﬂuorophenyl)-1,2,4-oxadiazol-5-yl]propanoic

acid (9b)⁴⁵3-[3-(4-chlorophenyl)-1,2,4-oxadiazol-5-yl]propanoic acid

(9c)⁴⁵3-[3-(4-methylphenyl)-1,2,4-oxadiazol-5-yl]propanoic acid

(9d)⁴⁵3-[3-(4-bromo-2-ﬂuorophenyl)-1,2,4-oxadiazol-5-yl]propanoic

acid (9e)⁴⁵

The propanoic acids 9a–e were prepared according to General

Procedure A, which has been modiﬁed according to reported

procedure.⁴⁵

180.0 (1C, C-3_oxadiazole). IR (neat):

m

(cm^À1) = 2210 (w, CN), 1712

(s, C@O).

6.3.1. 3-[3-(2-Cyano-4-ﬂuorophenyl)-1,2,4-oxadiazol-5-

yl]propanoic acid (9f)⁴⁵

6.3.4. 4-[3-(2-Bromo-4-ﬂuorophenyl)-1,2,4-oxadiazol-5-

yl]butanoic acid (11a)

The ester 10f (440 mg, 1.6 mmol) and LiOH (336 mg, 8.0 mmol)

were dissolved in THF (30 mL) and H₂O (10 mL) and the mixture

was stirred for 1 h at rt. Afterwards, the mixture was neutralized

with 1 M HCl, diluted with ethyl acetate and washed twice with

brine. The organic layer was dried (Na₂SO₄) and evaporated under

reduced pressure. The residue was recrystallized from CH₂Cl₂

(cyclohexane/ethyl acetate/formic acid 50:50:0.01, R_f0.66). Color-

less solid, mp 75–78 °C, yield 334 mg (80%). C₁₂H₈FN₃O₃(261.2 g/

mol). Exact mass (APCI): m/z = calcd for C₁₂H₈FN₃O₃H 262.0622

found 262.0619. Purity (HPLC): 98.8% (t_R= 14.79 min). ¹H NMR

(CDCl₃): d (ppm) = 2.82 (t, J = 7.0 Hz, 2H, CH₂CH₂CO₂H), 3.17 (t,

J = 7.0 Hz, 2H, CH₂CH₂CO₂H), 7.83 (td, J = 8.6/2.7 Hz, 1H, 5-H),

7.86 (dd, J = 8.7/2.6 Hz, 1H, 3-H), 8.20 (dd, J = 8.9/5.4 Hz, 1H,

6-H). ¹³C NMR (DMSO-d₆): d (ppm) = 21.7 (1C, CH₂CH₂CO₂H),

29.9 (1C, CH₂CH₂CO₂H), 111.8 (d, J = 10.4 Hz, 1C, C-2), 116.1

(d, J = 2.6 Hz, 1C, CN), 121.6 (d, J = 21.9 Hz, 1C, C-5), 122.5 (d,

J = 26.1 Hz, 1C, C-3), 125.0 (d, J = 3.6 Hz, 1C, C-1), 132.6 (d,

J = 9.4 Hz, 1C, C-6), 162.8 (d, J = 252.1 Hz, 1C, C-4), 165.0 (1C,

C-5_oxadiazole), 172.7 (1C, CH₂CH₂CO₂H), 180.2 (1C, C-3_oxadiazole). IR

According to General Procedure B, benzonitrile 8a (2.5 g,

12.5 mmol) was treated with NH₂OH–HCl (869 mg, 12.5 mmol)

and sodium carbonate (670 mg, 6.25 mmol) in H₂O (5 mL) and

CH₃OH (15 mL). The reaction mixture was stirred at 86 °C for

17.5 h. Afterwards, glutaric anhydride (1.4 g, 12.5 mmol) was

added to the intermediate and the reaction mixture was stirred

for 30 min at 148 °C. The residue was puriﬁed by fc (d = 6 cm,

l = 15 cm, cyclohexane/ethyl acetate/formic acid 50:50:0.01, R_f

0.29). Colorless solid, mp 94–95 °C, yield 1.3 g (32%). C₁₂H₁₀BrFN₂O₃

(329.1 g/mol). Exact mass (APCI): m/z = calcd for C₁₂H₁₀⁷⁹BrFN₂O_3-

H 330.0030 found 330.0048. Purity (HPLC): 97.3% (t_R= 17.29 min).

¹H NMR (CDCl₃): d (ppm) = 2.20–2.22 (m, 2H, CH₂CH₂CH₂CO₂H),

2.58 (t, J = 7.2 Hz, 2H, CH₂CH₂CH₂CO₂H), 3.08 (t, J = 7.4 Hz, 2H, CH_2-

CH₂CH₂CO₂H), 7.15 (ddd, J = 8.7/7.7/2.6 Hz, 1H, 5-H), 7.48 (dd,

J = 8.2/2.6 Hz, 1H, 3-H), 7.85 (dd, J = 8.7/6.0 Hz, 1H, 6-H). ¹³C NMR

(DMSO-d₆): d (ppm) = 21.4 (1C, CH₂CH₂CH₂CO₂H), 25.0 (1C, CH_2-

CH₂CH₂CO₂H), 30.2 (1C, CH₂CH₂CH₂CO₂H), 115.5 (d, J = 21.6 Hz,

1C, C-5), 121.3 (d, J = 25.1 Hz, 1C, C-3), 122.2 (d, J = 10.2 Hz, 1C,

C-2), 124.5 (d, J = 3.5 Hz, 1C, C-1), 133.7 (d, J = 9.5 Hz, 1C, C-6),

162.9 (d, J = 254.0 Hz, 1C, C-4), 166.6 (1C, C-5_oxadiazole), 173.8 (1C,

(neat):

C@O).

m

(cm^À1) = 3170–2310 (m, COOH), 2220 (w, CN), 1705 (s,

CH₂CH₂CO₂H), 179.5 (1C, C-3_oxadiazole). IR (neat):

m

(cm^À1) =

6.3.2. Methyl 3-[3-(2-bromo-4-ﬂuorophenyl)-1,2,4-oxadiazol-5-

yl]propanoate (10a)⁴⁵

3297–2965 (m, COOH), 1712 (s, C@O).

The carboxylic acid 9a (1.0 g, 3.2 mmol) was dissolved in

CH₃OH (50 mL) and H₂SO₄concd (0.03 mL, 0.7 mmol) was added.

The mixture was heated to reﬂux for 45 min. Then the reaction

mixture was neutralized with saturated NaHCO₃. The mixture

was concentrated in vacuo. The residue was dissolved in CH₂Cl₂

and washed twice with brine. The organic layer was dried

(Na₂SO₄), concentrated under reduced pressure and the residue

was recrystallized from ethyl acetate (cyclohexane/ethyl acetate/

formic acid 50:50:0.01, R_f0.70). Colorless solid, mp 114–116 °C,

yield 1.0 g (98%). C₁₂H₁₀BrFN₂O₃(329.0 g/mol). Exact mass (APCI):

m/z = calcd for C₁₂H₁₀⁷⁹BrFN₂O₃H 328.9932 found 328.9915. ¹H

NMR (CDCl₃): d (ppm) = 2.95 (t, J = 7.1 Hz, 2H, CH₂CH₂CO₂CH₃),

3.29 (t, J = 7.1 Hz, 2H, CH₂CH₂CO₂CH₃), 3.73 (s, 3H, CH₂CH₂CO_2-

CH₃), 7.15 (ddd, J = 8.7/7.7/2.6 Hz, 1H, 5-H), 7.48 (dd, J = 8.2/

6.3.5. 4-[3-(4-Fluorophenyl)-1,2,4-oxadiazol-5-yl]butanoic acid

(11b)

According to General Procedure B, benzonitrile 8b (5.0 g,

41.2 mmol) was treated with NH₂OH–HCl (2.9 g, 41.2 mmol) and

sodium carbonate (2.18 g, 20.6 mmol) in H₂O (16.5 mL) and CH₃OH

(65 mL). The reaction mixture was stirred at 86 °C for 3.5 h. After-

wards, glutaric anhydride (4.7 g, 41.2 mmol) was added to the

intermediate and the reaction mixture was stirred for 30 min at

148 °C. The residue was puriﬁed by fc (d = 6 cm, l = 15 cm, cyclo-

hexane/ethyl acetate/formic acid 50:50:0.01, R_f0.38). Colorless so-

lid, mp 89–91 °C, yield 5.8 g (56%). C₁₂H₁₁FN₂O₃(250.2 g/mol).

Exact mass (APCI): m/z = calcd for C₁₂H₁₁FN₂O₃H 251.0826 found

251.0824. Purity (HPLC): 87.0% (t_R= 16.48 min). ¹H NMR (CDCl₃):

d (ppm) = 2.22 (quint, J = 7.3 Hz, 2H, CH₂CH₂CH₂CO₂H), 2.56 (t,

J = 7.1 Hz, 2H, CH₂CH₂CH₂CO₂H), 3.05 (t, J = 7.1 Hz, 2H, CH₂CH₂CH_2-

CO₂H), 7.12–7.20 (m, 2H, 3-H, 5-H), 8.03–8.10 (m, 2H, 2-H, 6-H).

2.6 Hz, 1H, 3-H), 7.85 (dd, J = 8.7/6.0 Hz, 1H, 6-H). IR (neat):

m

(cm^À1) = 2966–2322 (m, COOH), 1735 (s, C@O).

C. Lueg et al. / Bioorg. Med. Chem. 21 (2013) 7481–7498

7487

¹³C NMR (DMSO-d₆): d (ppm) = 21.4 (1C, CH₂CH₂CH₂CO₂H), 25.1

(1C, CH₂CH₂CH₂CO₂H), 32.5 (1C, CH₂CH₂CH₂CO₂H), 116.4 (d,

J = 22.2 Hz, 2C, C-3, C-5), 122.9 (d, J = 3.1 Hz, C-1), 129.5 (d,

J = 9.0 Hz, 2C, C-2, C-6), 163.9 (d, J = 249.2, C-4), 166.7 (1C,

C-5_oxadiazole), 173.8 (1C, CH₂CH₂CH₂CO₂H), 180.3 (1C, C-3_oxadiazole).

CH₂H), 4.40 (t, J = 5.5 Hz, 2H, NCH₂CH₂OHCH₂CH₂H), 4.86 (t,

J = 5.4 Hz, 1H, NCH₂CH₂OHCH₂CH₂H), 7.15 (t, J = 7.4 Hz, 1H, 6-

H_carb), 7.41 (t, J = 6.5 Hz, 1H, 7-H_carb), 7.46 (td, J = 8.5/2.6 Hz, 1H,

5-H_phenyl), 7.51 (dd, J = 8.8/1.7 Hz, 1H, 2-H_carb), 7.54 (d, J = 8.8 Hz,

1H, 1-H_carb), 7.57 (d, J = 8.3 Hz, 1H, 8-H_carb), 7.83 (dd, J = 8.6/

2.6 Hz, 1H, 3-H_phenyl), 7.89 (dd, J = 8.7/6.1 Hz, 1H, 6-H_phenyl), 8.02

(d, J = 7.8 Hz, 1H, 5-H_carb), 8.39 (s, 1H, 4-H_carb), 10.13 (s, 1H, CONH).

¹³C NMR (DMSO-d₆): d (ppm) = 21.8 (1C, CH₂CH₂CONH), 32.0 (1C,

CH₂CH₂CONH), 45.3 (1C, NCH₂CH₂OH), 59.6 (1C, NCH₂CH₂OH),

109.5 (1C, C-8_carb), 109.7 (1C, C-1_carb), 110.9 (1C, C-4_carb), 115.5

(d, J = 21.6 Hz,1C, C-5_phenyl), 118.5 (1C, C-2_carb), 118.7 (1C, C-6_carb),

120.0 (1C, C-5_carb), 121.4 (d, J = 24.9 Hz, 1C, C-3_phenyl), 121.7 (1C, C-

4a_carb), 122.0 (1C, C-4b_carb), 122.2 (d, J = 10.1 Hz, 1C, C-2_phenyl),

124.5 (d, J = 3.4 Hz, 1C, C-1_phenyl), 125.6 (1C, C-7_carb), 131.0 (1C,

C-3_carb), 133.6 (d, J = 9.3 Hz, 1C, C-6_phenyl), 137.0 (1C, C-9a_carb),

140.9 (1C, C-8a_carb), 162.9 (d, J = 253.4 Hz, 1C, C-4_phenyl), 166.4

(1C, C-3_oxadiazole), 168.5 (1C, CONH), 179.6 (1C, C-5_oxadiazole). IR

IR (neat):

m

(cm^À1) = 3107–2357 (m, COOH), 1693 (s, C@O).

6.3.6. 4-[3-(4-Chlorophenyl)-1,2,4-oxadiazol-5-yl]butanoic acid

(11c)

According to General Procedure B, benzonitrile 8c (6.0 g,

43.6 mmol) was treated with NH₂OH–HCl (3.0 g, 43.6 mmol) and

sodium carbonate (2.3 g, 21.8 mmol) in H₂O (17 mL) and CH₃OH

(70 mL). The reaction mixture was stirred at 86 °C for 3.5 h. After-

wards, glutaric anhydride (5.0 g, 43.6 mmol) was added to the

intermediate and the reaction mixture was stirred for 30 min at

148 °C. The residue was puriﬁed by fc (d = 6 cm, l = 15 cm, cyclo-

hexane/ethyl acetate/formic acid 50:50:0.01, R_f0.31). Colorless so-

lid, mp 108–110 °C, yield 5.6 g (48%). C₁₂H₁₁ClN₂O₃(266.7 g/mol).

Exact mass (APCI): m/z = calcd for C₁₂H₁₁³⁵ClN₂O₃H 267.0531

found 267.0518. Purity (HPLC): 90.7% (t_R= 17.87 min). ¹H NMR

(CDCl₃): d (ppm) = 2.21 (quint, J = 7.2 Hz, 2H, CH₂CH₂CH₂CO₂H),

2.55 (t, J = 7.2 Hz, 2H, CH₂CH₂CH₂CO₂H), 3.04 (t, J = 7.4 Hz, 2H, CH_2-

CH₂CH₂CO₂H), 7.42–7.47 (m, 2H, 3-H, 5-H), 7.97–8.01 (m, 2H, 2-H,

6-H). ¹³C NMR (DMSO-d₆): d (ppm) = 21.4 (1C, CH₂CH₂CH₂CO₂H),

25.8 (1C, CH₂CH₂CH₂CO₂H), 32.8 (1C, CH₂CH₂CH₂CO₂H), 125.3

(1C, C-1), 128.9 (2C, C-2, C-6), 129.3 (2C, C-3, C-5), 137.5 (1C, C-

4), 167.6 (1C, C-5_oxadiazole), 178.6 (1C, CH₂CH₂CH₂CO₂H), 179.3

(neat):

m

(cm^À1) = 3421 (m, O–H), 3329 (m, N–H), 3078 (m, C–H,

arom), 2935 (m, C–H, aliph), 1678 (s, NH–C@O).

6.3.9. 3-[3-(4-Fluorophenyl)-1,2,4-oxadiazol-5-yl]-N-[9-(2-

hydroxyethyl)-9H-carbazol-3-yl]propanamide (15b)

According to the General Procedure C, 9b (1.0 g, 4.2 mmol) was

treated with 12 (0.86 g, 3.8 mmol), COMU^Ò(2.2 g, 5.1 mmol) and

triethylamine (1.7 mL, 12.6 mmol) in DMF (23 mL). This mixture

was stirred for 25 h at <10 °C. The residue was puriﬁed by fc

(d = 8 cm, l = 12 cm, cyclohexane/ethyl acetate 10:90, R_f0.55 (ethyl

acetate)). Colorless solid, mp 193–194 °C, yield 1.7 g (89%). C₂₅H_21-

FN₄O₃(444.5 g/mol). Exact mass (ESI): m/z = calcd for C₂₅H₂₁FN_4-

O₃H 445.1670 found 445.1666. Purity (HPLC): 96.3%

(t_R= 19.84 min). ¹H NMR (DMSO-d₆): d (ppm) = 3.00 (t, J = 7.0 Hz,

2H, CH₂CH₂CONHCH₂CH₂), 3.31 (t, J = 7.1 Hz, 2H, CH₂CH₂CON-

HCH₂CH₂), 3.76 (q, J = 5.5 Hz, 2H, NCH₂CH₂OHCH₂CH₂H), 4.39 (t,

J = 5.6 Hz, 2H, NCH₂CH₂OHCH₂CH₂H), 4.86 (t, J = 5.4 Hz, 1H, NCH_2-

CH₂OHCH₂CH₂H), 7.15 (t, J = 7.4 Hz, 1H, 6-H_carb), 7.37–7.44 (m, 3H,

7-H_carb, 3-H_phenyl, 5-H_phenyl), 7.48–7.55 (m, 2H, 1-H_carb, 2-H_carb),

7.57 (d, J = 8.3 Hz, 1H, 8-H_carb), 8.02 (d, J = 7.8 Hz, 1H, 5-H_carb),

8.03–8.08 (m, 2H, 2-H_phenyl, 6-H_phenyl), 8.39 (s, 1H, 4-H_carb), 10.14

(s, 1H, CONH). ¹³C NMR (DMSO-d₆): d (ppm) = 21.9 (1C, CH₂CH_2-

CONHCH₂CH₂), 32.0 (1C, CH₂CH₂CONHCH₂CH₂), 45.3 (1C, NCH_2-

CH₂OHCH₂CH₂H), 59.5 (1C, NCH₂CH₂OHCH₂CH₂H), 109.5 (1C, C-

(1C, C-3_oxadiazole). IR (neat):

m

(cm^À1) = 3110–2347 (m, COOH),

1691 (s, C@O).

6.3.7. 4-[3-(4-Methylphenyl)-1,2,4-oxadiazol-5-yl]butanoic acid

(11d)

According to General Procedure B, benzonitrile 8d (6.0 g,

51.2 mmol) was treated with NH₂OH–HCl (3.6 g, 51.2 mmol) and

sodium carbonate (2.7 g, 25.6 mmol) in H₂O (20.5 mL) and CH₃OH

(102 mL). The reaction mixture was stirred at 86 °C for 3.5 h. After-

wards, glutaric anhydride (5.9 g, 51.2 mmol) was added to the

intermediate and the reaction mixture was stirred for 30 min at

148 °C. The residue was puriﬁed by fc (d = 6 cm, l = 15 cm, cyclo-

hexane/ethyl acetate/formic acid 50:50:0.01, R_f0.33). Colorless so-

lid, mp 80–82 °C, yield 5.5 g (44%). C₁₃H₁₄N₂O₃(246.3 g/mol). Exact

mass (APCI): m/z = calcd for

C₁₃H₁₄N₂O₃H 247.1077 found

8_carb), 109.6 (1C, C-1_carb), 110.9 (1C, C-4_carb), 116.5 (d, J = 22.2 Hz,

247.1075. Purity (HPLC): 95.3% (t_R= 17.26 min). ¹H NMR (CDCl₃):

d (ppm) = 2.21 (quint, J = 7.3 Hz, 2H, CH₂CH₂CH₂CO₂H), 2.40 (s,

3H, CH₃), 2.55 (t, J = 7.2 Hz, 2H, CH₂CH₂CH₂CO₂H), 3.03 (t,

J = 7.4 Hz, 2H, CH₂CH₂CH₂CO₂H), 7.27 (d, J = 7.3 Hz, 2H, 3-H, 5-H),

7.94 (d, J = 8.2 Hz, 2 H, 2-H, 6-H). ¹³C NMR (DMSO-d₆): d (ppm) =

21.6 (1C, CH₃), 21.9 (1C, CH₂CH₂CH₂CO₂H), 25.8 (1C, CH₂CH₂CH_2-

CO₂H), 32.9 (1C, CH₂CH₂CH₂CO₂H), 124.0 (1C, C-1), 127.5 (2C, C-

2, C-6), 129.7 (2C, C-3, C-5), 141.6 (1C, C-4), 168.4 (1C, C-5_oxadiazole),

2C, C-3_phenyl, C-5_phenyl), 118.4 (1C, C-2_carb), 118.9 (1C, C-6_carb),

119.9 (1C, C-5_carb), 121.7 (1C, C-4a_carb), 121.9 (1C, C-4b_carb), 122.9

(d, J = 3.1 Hz, 1C, C-1_phenyl), 125.6 (1C, C-7_carb), 129.5 (d,

J = 9.3 Hz, 2C, C-2_phenyl, C-6_phenyl), 131.0 (1C, C-3_carb), 137.0 (1C,

C-9a_carb), 140.8 (1C, C-8a_carb), 163.9 (d, J = 249.1 Hz, 1C, C-4_phenyl),

166.7 (1C, C-3_oxadiazole), 168.5 (1C, CONH), 180.2 (1C, C-5_oxadiazole).

IR (neat):

H, aliph), 1678 (s, NH–C@O).

m

(cm^À1) = 3429 (m, O–H), 3329 (m, N–H), 2935 (m, C–

178.6 (1C, CH₂CH₂CH₂CO₂H), 179.3 (1C, C-3_oxadiazole). IR (neat):

m

(cm^À1) = 3210–2461 (m, COOH), 1708 (s, C@O).

6.3.10. 3-[3-(4-Chlorophenyl)-1,2,4-oxadiazol-5-yl]-N-[9-(2-

hydroxyethyl)-9H-carbazol-3-yl]propanamide (15c)

6.3.8. 3-[3-(2-Bromo-4-ﬂuorophenyl)-1,2,4-oxadiazol-5-yl]-N-

[9-(2-hydroxyethyl)-9H-carbazol-3-yl]propanamide (15a)

According to the General Procedure C, 9c (200 mg, 0.8 mmol)

was treated with 12 (210 mg, 0.8 mmol), COMU^Ò(340 mg,

0.9 mmol) and triethylamine (0.2 mL, 1.4 mmol) in DMF (12 mL).

This mixture was stirred for 20 h at <10 °C. The residue was

puriﬁed by fc (d = 8 cm, l = 12 cm, cyclohexane/ethyl acetate

15:85, R_f0.51 (ethyl acetate)). Colorless solid, mp 206–208 °C, yield

230 mg (65%). C₂₅H₂₁FN₄O₃(461.0 g/mol). Exact mass (ESI): m/

z = calcd for C₂₅H₂₁³⁵ClN₄O₃H 461.1375 found 461.1374. Purity

(HPLC): 98.4% (t_R= 20.53 min). ¹H NMR (DMSO-d₆): d (ppm) =

3.00 (t, J = 7.0 Hz, 2H, CH₂CH₂CONHCH₂CH₂), 3.30 (t, J = 7.1 Hz,

2H, CH₂CH₂CONHCH₂CH₂), 3.76 (q, J = 5.5 Hz, 2H, NCH₂CH₂OHCH_2-

CH₂H), 4.39 (t, J = 5.6 Hz, 2H, NCH₂CH₂OHCH₂CH₂H), 4.86 (t,

J = 5.4 Hz, 1H, NCH₂CH₂OHCH₂CH₂H), 7.15 (t, J = 7.4 Hz, 1H, 6-

According to the General Procedure C, 9a (400 mg, 1.3 mmol)

was treated with 12 (222 mg, 0.9 mmol), COMU^Ò(652 mg,

1.5 mmol) and triethylamine (0.54 mL, 3.9 mmol) in DMF

(15 mL). This mixture was stirred for 24 h at <10 °C. The residue

was puriﬁed by fc (d = 5 cm, l = 15 cm, cyclohexane/ethyl acetate

15:85, R_f0.51 (ethyl acetate)). Colorless solid, mp 163–165 °C, yield

368 mg (80%). C₂₅H₂₀BrFN₄O₃(523.4 g/mol). Exact mass (ESI): m/

z = calcd for C₂₅H₂₀⁷⁹BrFN₄O₃H 523.0776 found 523.0783. Purity

(HPLC): 97.7% (t_R= 20.24 min). ¹H NMR (DMSO-d₆): d (ppm) =

2.99 (t, J = 7.0 Hz, 2H, CH₂CH₂CONHCH₂CH₂), 3.35 (t, J = 7.1 Hz,

2H, CH₂CH₂CONHCH₂CH₂), 3.76 (q, J = 5.6 Hz, 2H, NCH₂CH₂OHCH_2-

7488

C. Lueg et al. / Bioorg. Med. Chem. 21 (2013) 7481–7498

H_carb), 7.41 (t, J = 7.7 Hz, 1H, 7-H_carb), 7.48–7.55 (m, 2H, 1-H_carb, 2-

_carb), 7.57 (d, J = 8.2 Hz, 1H, 8-H_carb), 7.60–7.66 (m, 2H, 3-H_phenyl

CH₂CONHCH₂CH₂), 32.0 (1C, CH₂CH₂CONHCH₂CH₂), 45.3 (1C,

NCH₂CH₂OHCH₂CH₂), 59.6 (1C, NCH₂CH₂OHCH₂CH₂), 109.5 (1C,

C-8_carb), 109.7 (1C, C-1_carb), 110.9 (1C, C-4_carb), 115.5 (d,

J = 21.7 Hz, 1C, C-1_phenyl), 118.5 (1C, C-2_carb), 118.7 (1C, C-6_carb),

120.0 (1C, C-5_carb), 121.4 (d, J = 24.9 Hz, 1C, C-3_phenyl), 121.7 (1C,

C-4a_carb), 122.0 (1C, C-4b_carb), 122.2 (d, J = 10.1 Hz, 1C, C-4_phenyl),

124.5 (d, J = 3.4 Hz, 1C, C-5_phenyl), 125.6 (1C, C-7_carb), 131.0 (1C,

C-3_carb), 133.6 (d, J = 9.3 Hz, 1C, C-6_phenyl), 137.0 (1C, C-9a_carb),

140.9 (1C, C-8a_carb), 162.9 (d, J = 252.9 Hz, 1C, C-2_phenyl), 166.6

(d, J = 9.4 Hz, 1C, C-3_oxadiazole), 168.5 (1C, CONH), 179.7

H

,

5-H_phenyl), 8.03–8.08 (m, 3H, 5-H_carb, 2-H_phenyl, 6-H_phenyl), 8.39 (s,

1H, 4-H_carb), 10.14 (s, 1H, CONH). ¹³C NMR (DMSO-d₆): d (ppm) =

21.9 (1C, CH₂CH₂CONHCH₂CH₂), 32.0 (1C, CH₂CH₂CONHCH₂CH₂),

45.3 (1C, NCH₂CH₂OHCH₂CH₂H), 59.5 (1C, NCH₂CH₂OHCH₂CH₂H),

109.5 (1C, C-8_carb), 109.6 (1C, C-1_carb), 110.9 (1C, C-4_carb), 118.4

(1C, C-2_carb), 118.9 (1C, C-6_carb), 119.9 (1C, C-5_carb), 121.7 (1C, C-

4a_carb), 121.9 (1C, C-4b_carb), 125.2 (1C, C-7_carb), 125.6 (1C, C-3_carb),

128.8 (2C, C-3_phenyl, C-5_phenyl), 129.5 (2C, C-2_phenyl, C-6_phenyl),

131.0 (1C, C-1_phenyl), 136.2 (1C, C-4_phenyl), 137.0 (1C, C-9a_carb),

140.8 (1C, C-8a_carb), 166.7 (1C, C-3_oxadiazole), 168.5 (1C, CONH),

(1C, C-5_oxadiazole). IR (neat):

N–H), 2935 (m, C–H, aliph), 1681 (s, NH–C@O).

m

(cm^À1) = 3429 (m, O–H), 3332 (m,

180.4 (1C, C-5_oxadiazole). IR (neat):

m

(cm^À1) = 3278 (m, N–H),

2931 (m, C–H, aliph), 1654 (s, NH–C@O).

6.3.13. 3-[3-(2-Cyano-4-ﬂuorophenyl)-1,2,4-oxadiazol-5-yl]-N-

[9-(2-hydroxyethyl)-9H-_carbazol-3-yl]propanamide (15f)

6.3.11. N-[9-(2-Hydroxyethyl)-9H-carbazol-3-yl]-3-[3-(4-

methylphenyl)-1,2,4-oxadiazol-5-yl]propanamide (15d)

According to the General Procedure C, 9f (240 mg, 0.92 mmol)

was treated with 12 (242 mg, 0.92 mmol), COMU^Ò(590 mg,

1.4 mmol) and triethylamine (0.5 mL, 3.5 mmol) in DMF (13 mL).

This mixture was stirred for 24 h at <10 °C. The residue was puri-

ﬁed by fc (d = 5 cm, l = 20 cm, cyclohexane/ethyl acetate 15:85, R_f

0.43 (ethyl acetate)). Colorless solid, mp 210 °C, yield 60 mg

(14%). C₂₆H₂₀FN₅O₃(470.5 g/mol). Exact mass (ESI): m/z = calcd

for C₂₆H₂₀FN₅O₃H 470.1623 found 470.1611. Purity (HPLC): 98.1%

(t_R= 18.95 min). ¹H NMR (DMSO-d₆): d (ppm) = 3.02 (t, J = 7.0 Hz,

2H, CH₂CH₂CONHCH₂CH₂), 3.28 (t, J = 7.1 Hz, 2H, CH₂CH₂CON-

HCH₂CH₂), 3.73–3.78 (m, 2H, NCH₂CH₂OHCH₂CH₂), 4.40 (t,

J = 5.6 Hz, 2H, NCH₂CH₂OHCH₂CH₂), 4.86 (t, J = 5.4 Hz, 1H, NCH_2-

CH₂OHCH₂CH₂), 7.15 (t, J = 7.4 Hz, 1H, 6-H_carb), 7.41 (t, J = 7.7 Hz,

According to the General Procedure C, 9d (500 mg, 2.2 mmol)

was treated with 12 (242 mg, 0.92 mmol), COMU^Ò(1.1 g,

2.6 mmol) and triethylamine (0.6 mL, 4.4 mmol) in DMF (17 mL).

This mixture was stirred for 24 h at <10 °C. The residue was puri-

ﬁed by fc (d = 5 cm, l = 15 cm, cyclohexane/ethyl acetate 5:95, R_f

0.51 (ethyl acetate)). Colorless solid, mp 172–174 °C, yield

600 mg (63%). C₂₆H₂₄N₄O₃(440.5 g/mol). Exact mass (ESI): m/

z = calcd for

C₂₆H₂₄N₄O₃H 441.1915 found 441.1917. Purity

(HPLC): 95.3% (t_R= 20.07 min). ¹H NMR (DMSO-d₆): d (ppm) =

2.37 (s, 3H, CH₃), 2.99 (t, J = 7.0 Hz, 2H, CH₂CH₂CONHCH₂CH₂),

3.30 (t, J = 7.2 Hz, 2H, CH₂CH₂CONHCH₂CH₂), 3.72–3.79 (m, 2H,

NCH₂CH₂OHCH₂CH₂H), 4.39 (t, J = 5.6 Hz, 2H, NCH₂CH₂OHCH₂CH_2-

H), 4.86 (t, J = 5.4 Hz, 1H, NCH₂CH₂OHCH₂CH₂H), 7.15 (t, J = 7.4 Hz,

1H, 6-H_carb), 7.36 (d, J = 8.2 Hz, 2H, 2-H_phenyl, 6-H_phenyl), 7.41 (t,

J = 7.7 Hz, 1H, 7-H_carb), 7.49–7.54 (m, 2H, 1-H_carb, 2-H_carb), 7.57

(d, J = 8.2 Hz, 1H, 8-H_carb), 7.89 (d, J = 8.1 Hz, 2H, 3-H_phenyl, 5-

1H, 7-H_carb), 7.49–7.53 (m, 2H, 1-H_carb

, 2-H_carb), 7.57 (d,

J = 8.2 Hz, 1H, 8-H_carb), 7.80 (td, J = 8.5/2.7 Hz, 1H, 5-H_phenyl), 8.03

(d, J = 7.8 Hz, 1H, 5-H_carb), 8.13 (dd, J = 8.7/2.7 Hz, 1H, 3-H_phenyl),

8.19 (dd, J = 8.7/5.4 Hz, 1H, 6-H_phenyl), 8.39 (s, 1H, 4-H_carb), 10.15

(s, 1H, CONH). ¹³C NMR (DMSO-d₆): d (ppm) = 21.9 (1C, CH₂CH_2-

CONHCH₂CH₂), 31.9 (1C, CH₂CH₂CONHCH₂CH₂), 45.3 (1C, NCH_2-

CH₂OHCH₂CH₂), 59.5 (1C, NCH₂CH₂OHCH₂CH₂), 109.5 (1C, C-

H_phenyl), 8.02 (d, J = 7.8 Hz, 1H, 5-H_carb), 8.39 (s, 1H, 4-H_carb),

10.13 (s, 1H, CONH). ¹³C NMR (DMSO-d₆): d (ppm) = 21.5 (1C,

CH₃), 22.6 (1C, CH₂CH₂CONHCH₂CH₂), 32.7 (1C, CH₂CH₂CONHCH_2-

CH₂), 45.9 (1C, NCH₂CH₂OHCH₂CH₂), 60.2 (1C, NCH₂CH₂OHCH_2-

CH₂), 110.3 (1C, C-8_carb), 111.6 (1C, C-1_carb), 119.1 (1C, C-4_carb),

119.4 (1C, C-2_carb), 120.6 (1C, C-6_carb), 122.4 (1C, C-5_carb), 122.6

(1C, C-4a_carb), 124.2 (1C, C-4b_carb), 126.2 (1C, C-1_phenyl), 127.6 (1C,

C-7_carb), 130.5 (2C, C-3_phenyl, C-5_phenyl), 131.7 (2C, C-2_phenyl, C-

8_carb), 109.6 (1C, C-1_carb), 110.9 (1C, C-4_carb), 116.2 (d, J = 2.7 Hz,

1C, CN), 118.5 (1C, C-2_carb), 118.7 (1C, C-6_carb), 120.0 (1C, C-5_carb),

121.6 (d, J = 21.9 Hz, 1C, C-5_phenyl), 121.7 (d, J = 5.5 Hz, 1-C, C-

2_phenyl), 122.0 (1C, C-4a_carb), 122.5 (d, J = 26.0 Hz, 1C, C-3_phenyl),

122.6 (1C, C-4b_carb), 125.1 (d, J = 3.5 Hz, 1C, C-1_phenyl), 125.6 (1C,

C-7_carb), 132.0 (1C, C-3_carb), 132.6 (d, J = 9.7 Hz, 1C, C-6_phenyl),

137.0 (1C, C-9a_carb), 140.8 (1C, C-8a_carb), 162.7 (d, J = 259.2 Hz,

1C, C-4_phenyl), 165.0 (1C, C-3_oxadiazole), 168.5 (1C, CONH), 180.6

6

_phenyl), 137.6 (1C, C-3_carb), 137.7 (1C, C-9a_carb), 141.5 (1C, C-

4_phenyl), 142.1 (1C, C-8a_carb), 168.1 (1C, C-3_oxadiazole), 169.3 (1C,

CONH), 180.6 (1C, C-5_oxadiazole). IR (neat):

(cm^À1) = 3356 (m, O–

m

(1C, C-5_oxadiazole). IR (neat): m

(cm^À1) = 3506 (m, O–H), 3329 (m,

H), 3278 (m, N–H), 2931 (m, C–H, aliph), 1654 (s, NH–C@O).

N–H), 2935 (m, C–H, aliph), 2233 (w, CN), 1685 (s, NH–C@O).

6.3.12. 3-[3-(4-Bromo-2-ﬂuorophenyl)-1,2,4-oxadiazol-5-yl)]-N-

[9-(2-hydroxyethyl)-9H-_carbazol-3-yl]propanamide (15e)

6.3.14. 3-[3-(2-Bromo-4-ﬂuorophenyl)-1,2,4-oxadiazol-5-yl]-N-

[9-(3-hydroxypropyl)-9H-_carbazol-3-yl]propanamide (16a)

According to the General Procedure C, 9a (453 mg, 1.4 mmol)

was treated with 13 (400 mg, 1.4 mmol), COMU^Ò(740 mg,

1.7 mmol) and triethylamine (0.4 mL, 2.8 mmol) in DMF (15 mL).

This mixture was stirred for 24 h at <10 °C. The residue was puri-

ﬁed by fc (d = 6 cm, l = 10 cm, cyclohexane/ethyl acetate 5:95, R_f

0.20 (ethyl acetate)). Colorless solid, mp 155–157 °C, yield

229 mg (30%). C₂₆H₂₂BrFN₄O₃(537.4 g/mol). Exact mass (ESI): m/

z = calcd for C₂₆H₂₂⁷⁹BrFN₄O₃H 537.0935 found 537.0932. Purity

(HPLC): 96.6% (t_R= 20.53 min). ¹H NMR (DMSO-d₆): d (ppm) =

1.82–1.91 (m, 2H, NCH₂CH₂CH₂OH), 2.97 (t, J = 7.1 Hz, 2H, CH₂CH_2-

CONHCH₂CH₂), 3.12 (t, J = 7.2 Hz, 2H, CH₂CH₂CONHCH₂CH₂),

3.33–3.36 (m, 2H, NCH₂CH₂CH₂OH), 4.40 (t, J = 6.7 Hz, 2H, NCH₂CH_2-

CH₂OH), 4.86 (t, J = 4.9 Hz, 1H, NCH₂CH₂OHCH₂CH₂), 7.13 (t,

J = 7.5 Hz, 1H, 6-H_carb), 7.38–7.47 (m, 2H, 7-H_carb, 5-H_phenyl), 7.52–

7.54 (m, 2H, 1-H_carb, 2-H_carb), 7.57 (d, J = 8.3 Hz, 1H, 8-H_carb), 7.78–

7.90 (m, 2H, 3-H_phenyl, 6-H_phenyl), 8.01 (d, J = 7.8 Hz, 1H, 5-H_carb),

8.38 (s, 1H, 4-H_carb), 10.12 (s, 1H, CONH). ¹³C NMR (DMSO-d₆): d

(ppm) = 21.1 (1C, CH₂CH₂CONHCH₂CH₂), 31.8 (1C, NCH₂CH₂CH₂

According to the General Procedure C, 9e (200 mg, 0.64 mmol)

was treated with 12 (144 mg, 0.635 mmol), COMU^Ò(326 mg,

0.76 mmol) and triethylamine (0.27 mL, 1.9 mmol) in DMF

(15 mL). This mixture was stirred for 26 h at <10 °C. The residue

was puriﬁed by fc (d = 5.5 cm, l = 17 cm, cyclohexane/ethyl acetate

15:85, R_f0.60 (ethyl acetate)). Colorless solid, mp 208 °C, yield

140 mg (42%). C₂₅H₂₀BrFN₄O₃(523.4 g/mol). Exact mass (ESI): m/

z = calcd for C₂₅H₂₀⁷⁹BrFN₄O₃H 523.0776 found 523.0717. Purity

(HPLC): 92.3% (t_R= 19.10 min). ¹H NMR (DMSO-d₆): d (ppm) =

3.02 (t, J = 6.9 Hz, 2H, CH₂CH₂CONHCH₂CH₂), 3.29 (t, J = 7.0 Hz,

2H, CH₂CH₂CONHCH₂CH₂), 3.76 (q, J = 5.5 Hz, 2H, NCH₂CH₂OHCH_2-

CH₂), 4.39 (t, J = 5.6 Hz, 2H, NCH₂CH₂OHCH₂CH₂), 4.86 (t, J = 5.4 Hz,

1H, NCH₂CH₂OHCH₂CH₂), 7.15 (t, J = 7.4 Hz, 1H, 6-H_carb), 7.41 (t,

J = 7.2 Hz, 1H, 7-H_carb), 7.48–7.55 (m, 2H, 1-H_carb, 2-H_carb), 7.57

(d, J = 8.3 Hz, 1H, 8-H_carb), 7.80 (td, J = 8.6/ 2.7 Hz, 1H, 5-H_phenyl),

8.02 (d, J = 7.8 Hz, 1H, 5-H_carb), 8.13 (dd, J = 8.7/2.7 Hz, 1H, 3-

H

_phenyl), 8.18 (dd, J = 8.8/5.5 Hz, 1H, 6-H_phenyl), 8.39 (s, 1H, 4-H_carb),

10.15 (s, 1H, CONH). ¹³C NMR (DMSO-d₆): d (ppm) = 21.8 (1C, CH₂

C. Lueg et al. / Bioorg. Med. Chem. 21 (2013) 7481–7498

7489

OH), 32.0 (1C, CH₂CH₂CONHCH₂CH₂), 58.0 (1C, NCH₂CH₂CH₂OH),

109.1 (1C, C-8_carb), 109.3 (1C, C-1_carb), 111.1 (1C, C-4_carb), 115.5 (d,

J = 21.8 Hz, 1C, C-5_phenyl), 118.5 (1C, C-2_carb), 118.9 (1C, C-6_carb),

120.1 (1C, C-5_carb), 121.4 (d, J = 24.6 Hz, 1C, C-3_phenyl), 121.7 (1C, C-

4a_carb), 121.9 (1C, C-4b_carb), 122.3 (d, J = 8.7 Hz, 1C, C-2_phenyl), 125.8

(d, J = 10.6 Hz, 1C, C-6_phenyl), 126.9 (1C, C-7_carb), 129.8 (1C, C-3_carb),

131.1 (d, J = 3.8 Hz, 1C, C-1_phenyl), 136.7 (1C, C-9a_carb), 141.4 (1C, C-

8a_carb), 163.7 (d, J = 258.9 Hz, 1C, C-4_phenyl), 167.4 (1C, C-3_oxadiazole),

168.6 (1C, CONH), 179.9 (1C, C-5_oxadiazole). The signal for NCH₂CH_2-

C-5_carb), 121.7 (1C, C-4a_carb), 121.9 (1C, C-4b_carb), 125.2 (1C, C-7_carb),

125.7 (1C, C-3_carb), 128.7 (2C, C-3_phenyl, C-5_phenyl), 129.5 (2C,

C-2_phenyl, C-6_phenyl), 131.0 (1C, C-1_phenyl), 136.2 (1C, C-4_phenyl), 136.6

(1C, C-9a_carb), 140.5 (1C, C-8a_carb), 166.7 (1C, C-3_oxadiazole), 168.6

(1C, CONH), 180.4 (1C, C-5_oxadiazole). The signal for NCH₂CH₂CH₂OH

is overlaid by the solvent peak. IR (neat): m

(cm^À1) = 3420 (m, O–H),

3290 (m, N–H), 2931 (m, C–H, aliph), 1643 (s, NH–C@O).

6.3.17. N-[9-(3-Hydroxypropyl)-9H-_carbazol-3-yl]-3-[3-(4-

methylphenyl)-1,2,4-oxadiazol-5-yl]propanamide (16d)

CH₂OH is overlaid by the solvent peak. IR (neat):

m

(cm^À1) = 3667

(m, O–H), 3290 (m, N–H), 1654 (s, NH–C@O).

According to the General Procedure C, 9d (350 mg, 1.5 mmol)

was treated with 13 (375 mg, 1.4 mmol), COMU^Ò(775 mg,

1.8 mmol) and triethylamine (0.4 mL, 2.8 mmol) in DMF (15 mL).

This mixture was stirred for 24 h at <10 °C. The residue was puri-

ﬁed by fc (d = 6 cm, l = 12 cm, cyclohexane/ethyl acetate 10:90, R_f

0.43 (ethyl acetate)). Colorless solid, mp 192 °C, yield 456 mg

(67%). C₂₇H₂₆N₄O₃(454.5 g/mol). Exact mass (ESI): m/z = calcd for

6.3.15. 3-[3-(4-Fluorophenyl)-1,2,4-oxadiazol-5-yl]-N-[9-(3-

hydroxypropyl)-9H-_carbazol-3-yl]propanamide (16b)

According to the General Procedure C, 9b (350 mg, 1.5 mmol)

was treated with 13 (370 mg, 1.3 mmol), COMU^Ò(762 mg,

1.8 mmol) and triethylamine (0.4 mL, 2.8 mmol) in DMF (24 mL).

This mixture was stirred for 22.5 h at <10 °C. The residue was puri-

ﬁed by fc (d = 6 cm, l = 12 cm, cyclohexane/ethyl acetate 10:90, R_f

0.48 (ethyl acetate)). Colorless solid, mp 167–168 °C, yield

480 mg (71%). C₂₆H₂₃FN₄O₃(458.5 g/mol). Exact mass (ESI): m/

C

₂₇H₂₆N₄O₃H 455.2078 found 455.2087. Purity (HPLC): 97.5%

(t_R= 20.65 min). ¹H NMR (DMSO-d₆):

d

(ppm) = 1.9 (quint,

J = 6.5 Hz, 2H, NCH₂CH₂CH₂OH), 2.37 (s, 3H, CH₃), 3.00 (t,

J = 7.0 Hz, 2H, CH₂CH₂CONHCH₂CH₂), 3.31 (t, J = 7.2 Hz, 2H, CH_2-

CH₂CONHCH₂CH₂), 3.37–3.43 (m, 2H, NCH₂CH₂CH₂OH), 4.40 (t,

J = 5.6 Hz, 2H, NCH₂CH₂CH₂OH), 4.65 (t, J = 4.9 Hz, 1H, NCH₂CH_2-

OHCH₂CH₂), 7.16 (t, J = 7.4 Hz, 1H, 6-H_carb), 7.36 (d, J = 8.3 Hz, 2H,

2-H_phenyl, 6-H_phenyl), 7.43 (t, J = 7.3 Hz, 1H, 7-H_carb), 7.49–7.52 (m,

2H, 1-H_carb, 2-H_carb), 7.56 (d, J = 8.2 Hz, 1H, 8-H_carb), 7.89 (d,

J = 8.1 Hz, 2H, 3-H_phenyl, 5-H_phenyl), 8.03 (d, J = 7.7 Hz, 1H, 5-H_carb),

8.41 (s, 1H, 4-H_carb), 10.15 (s, 1H, CONH). ¹³C NMR (DMSO-d₆): d

(ppm) = 21.1 (1C, CH₃), 21.9 (1C, CH₂CH₂CONHCH₂CH₂), 31.7 (1C,

NCH₂CH₂CH₂OH), 32.1 (1C, CH₂CH₂CONHCH₂CH₂), 58.0 (1C, NCH_2-

CH₂CH₂OH), 109.2 (1C, C-8_carb), 109.3 (1C, C-1_carb), 111.1 (1C, C-

z = calcd for

C₂₆H₂₃FN₄O₃H 459.1827 found 459.1809. Purity

(HPLC): 97.4% (t_R= 20.15 min). ¹H NMR (DMSO-d₆): d (ppm) =

1.85–1.94 (m, 2H, NCH₂CH₂CH₂OH), 3.00 (t, J = 7.0 Hz, 2H, CH₂CH_2-

CONHCH₂CH₂), 3.31 (t, J = 7.1 Hz, 2H, CH₂CH₂CONHCH₂CH₂), 3.39

(m, 2H, NCH₂CH₂CH₂OH), 4.40 (t, J = 6.8 Hz, 2H, NCH₂CH₂CH₂OH),

4.64 (t, J = 5.4 Hz, 1H, NCH₂CH₂CH₂OH), 7.16 (t, J = 7.4 Hz, 1H, 6-

H_carb), 7.36–7.46 (m, 3H, 7-H_carb, 3-H_phenyl, 5-H_phenyl), 7.53 (s, 2H,

1-H_carb, 2-H_carb), 7.57 (d, J = 8.2 Hz, 1H, 8-H_carb), 8.00–8.08 (m,

3H, 5-H_carb, 2-H_phenyl, 6-H_phenyl), 8.40 (s, 1H, 4-H_carb), 10.15 (s,

1H, CONH). ¹³C NMR (DMSO-d₆): d (ppm) = 21.9 (1C, CH₂CH₂CON-

HCH₂CH₂), 31.8 (1C, NCH₂CH₂CH₂OH), 32.0 (1C, CH₂CH₂CONHCH_2-

CH₂), 58.0 (1C, NCH₂CH₂CH₂OH), 109.2 (1C, C-8_carb), 109.3 (1C,

C-1_carb), 111.1 (1C, C-4_carb), 116.5 (d, J = 22.2 Hz, 2C, C-3_phenyl, C-

4

_carb), 118.5 (1C, C-2_carb), 118.9 (1C, C-6_carb), 120.1 (1C, C-5_carb),

121.7 (1C, C-4a_carb), 121.9 (1C, C-4b_carb), 123.6 (1C, C-7_carb), 125.8

(1C, C-1_phenyl), 126.9 (2C, C-3_phenyl, C-5_phenyl), 129.8 (2C, C-2_phenyl

,

5

_phenyl), 118.5 (1C, C-2_carb), 118.8 (1C, C-6_carb), 120.1 (1C, C-5_carb),

C-6_phenyl), 131.1 (1C, C-3_carb), 136.7 (1C, C-9a_carb), 140.5 (1C, C-

8a_carb), 141.4 (1C, C-4_phenyl), 167.5 (1C, C-3_oxadiazole), 168.6 (1C,

CONH), 179.9 (1C, C-5_oxadiazole). The signal for NCH₂CH₂CH₂OH is

121.7 (1C, C-4a_carb), 121.9 (1C, C-4b_carb), 122.9 (d, J = 3.1 Hz, 1C,

C-1_phenyl), 125.8 (1C, C-7_carb), 129.5 (d, J = 9.0 Hz, 2C, C-2_phenyl, C-

6_phenyl), 131.1 (1C, C-3_carb), 136.7 (1C, C-9a_carb), 140.5 (1C, C-8a_carb),

overlaid by the solvent peak. IR (neat): m

(cm^À1) = 3383 (m, O–

163.9 (d, J = 249.0 Hz, 1C, C-4_phenyl), 166.7 (1C, C-3_oxadiazole), 168.6

H), 3290 (m, N–H), 2935 (m, C–H, aliph), 1654 (s, NH–C@O).

(1C, CONH), 180.3 (1C, C-5_oxadiazole). The signal for NCH₂CH₂CH₂OH

is overlaid by the solvent peak. IR (neat):

3059 (w. C–H, arom), 2935 (m, C–H, aliph), 1647 (s, NH–C@O).

m

(cm^À1) = 3286 (m, N–H),

6.3.18. 3-[3-(2-Bromo-4-ﬂuorophenyl)-1,2,4-oxadiazol-5-yl]-N-

[9-(4-hydroxybutyl)-9H-_carbazol-3-yl]propanamide (17a)

According to the General Procedure C, 9a (275 mg, 0.87 mmol)

was treated with 14 (270 mg, 1.2 mmol), COMU^Ò(560 mg,

1.3 mmol) and triethylamine (0.36 mL, 3.6 mmol) in DMF

(15 mL). This mixture was stirred for 22.5 h at <10 °C. The residue

was puriﬁed by fc (d = 5 cm, l = 15 cm, cyclohexane/ethyl acetate

15:85, R_f0.43 (ethyl acetate)). Colorless solid, mp 158–161 °C, yield

158 mg (33%). C₂₇H₂₄BrFN₄O₃(551.4 g/mol). Exact mass (ESI): m/

z = calcd for C₂₇H₂₄⁷⁹BrFN₄O₃H 551.1089 found 551.1052. Pur-

ity > 99%. ¹H NMR (DMSO-d₆): d (ppm) = 1.37–1.45 (m, 2H, NCH_2-

CH₂CH₂CH₂OH), 1.73–1.82 (m. 2H, NCH₂CH₂CH₂CH₂OH), 2.98 (t,

J = 7.0 Hz, 2H, CH₂CH₂CONHCH₂CH₂), 3.31 (m, 2H, NCH₂CH₂CH_2-

CH₂OH), 3.36 (t, J = 7.0 Hz, 2H, CH₂CH₂CONHCH₂CH₂), 4.36 (q,

J = 6.7 Hz, 2H, NCH₂CH₂CH₂CH₂OH), 4.46 (t, J = 6.7 Hz, 1H, NCH_2-

CH₂CH₂CH₂OH), 7.16 (t, J = 7.7 Hz, 1H, 6-H_carb), 7.40–7.47 (m, 2H,

7-H_carb, 5-H_phenyl), 7.52–7.54 (m, 2H, 1-H_carb, 2-H_carb), 7.56 (d,

J = 8.2 Hz, 1H, 8-H_carb), 7.81 (dd, J = 8.4/2.4 Hz, 1H, 3-H_phenyl), 7.87

(dd, J = 8.7/6.0 Hz, 1H, 6-H_phenyl), 8.02 (d, J = 7.6 Hz, 1H, 5-H_carb),

8.38 (s, 1H, 4-H_carb), 10.16 (s, 1H, CONH). ¹³C NMR (DMSO-d₆): d

(ppm) = 21.81 (1C, CH₂CH₂CONHCH₂CH₂), 25.36 (1C, NCH₂CH₂CH_2-

CH₂OH), 29.98 (1C, NCH₂CH₂CH₂CH₂OH), 31.97 (1C, CH₂CH₂CON-

HCH₂CH₂), 42.19 (1C, NCH₂CH₂CH₂CH₂OH), 60.43 (1C,

NCH₂CH₂CH₂CH₂OH), 109.2 (1C, C-8_carb), 109.4 (1C, C-1_carb),

111.0 (1C, C-4_carb), 115.5 (d, J = 21.6 Hz, 1C, C-5_phenyl), 118.5 (1C,

C-2_carb), 118.8 (1C, C-6_carb), 120.1 (1C, C-5_carb), 121.4 (d,

6.3.16. 3-[3-(4-Chlorophenyl)-1,2,4-oxadiazol-5-yl]-N-[9-(3-

hydroxypropyl)-9H-_carbazol-3-yl]propanamide (16c)

According to the General Procedure C, 9c (550 mg, 2.2 mmol)

was treated with 13 (598 mg, 2.1 mmol), COMU^Ò(1.1 g, 2.6 mmol)

and triethylamine (0.6 mL, 4.4 mmol) in DMF (14 mL). This mix-

ture was stirred for 20 h at <10 °C. The residue was puriﬁed by fc

(d = 6 cm, l = 12 cm, cyclohexane/ethyl acetate 5:95, R_f0.50 (ethyl

acetate)). Colorless solid, mp 190 °C, yield 822 mg (80%). C₂₆H_23-

35-

FN₄O₃(474.9 g/mol). Exact mass (ESI): m/z = calcd for C₂₆H₂₃

ClN₄O₃H 475.1531 found 475.1534. Purity (HPLC): 96.1%

(t_R= 21.05 min). ¹H NMR (DMSO-d₆):

d (ppm) = 1.89 (quint,

J = 6.5 Hz, 2H, NCH₂CH₂CH₂OH), 3.00 (t, J = 7.0 Hz, 2H, CH₂CH_2-

CONHCH₂CH₂), 3.32 (t, J = 7.1 Hz, 2H, CH₂CH₂CONHCH₂CH₂),

3.36–3.42 (m, J = 5.5 Hz, 2H, NCH₂CH₂CH₂OH), 4.40 (t, J = 6.8 Hz,

2H, NCH₂CH₂CH₂OH), 4.65 (t, J = 4.9 Hz, 1H, NCH₂CH₂OHCH₂CH₂),

7.15 (t, J = 7.5 Hz, 1H, 6-H_carb), 7.43 (t, J = 8.2 Hz, 1H, 7-H_carb),

7.48–7.55 (m, 2H, 1-H_carb, 2-H_carb), 7.56 (d, J = 8.3 Hz, 1H, 8-H_carb),

7.61–7.65 (m, 2H, 3-H_phenyl, 5-H_phenyl), 7.99–8.04 (m, 3H, 5-H_carb, 2-

H

_phenyl, 6-H_phenyl), 8.40 (s, 1H, 4-H_carb), 10.15 (s, 1H, CONH). ¹³C

NMR (DMSO-d₆): d (ppm) = 21.9 (1C, CH₂CH₂CONHCH₂CH₂), 31.8

(1C, NCH₂CH₂CH₂OH), 32.0 (1C, CH₂CH₂CONHCH₂CH₂), 58.0 (1C,

NCH₂CH₂CH₂OH), 109.1 (1C, C-8_carb), 109.2 (1C, C-1_carb), 111.1

(1C, C-4_carb), 118.5 (1C, C-2_carb), 118.8 (1C, C-6_carb), 120.9 (1C,

7490

C. Lueg et al. / Bioorg. Med. Chem. 21 (2013) 7481–7498

J = 25.1 Hz, 1C, C-3_phenyl), 121.7 (1C, C-4a_carb), 121.9 (1C, C-4b_carb),

122.2 (d, J = 10.1 Hz, 1C, C-2_phenyl), 124.5 (d, J = 3.5 Hz, 1C, C-

C-1_phenyl), 125.6 (1C, C-7_carb), 129.5 (d, J = 9.3 Hz, 2C, C-2_phenyl, C-

6_phenyl), 131.0 (1C, C-3_carb), 137.0 (1C, C-9a_carb), 140.8 (1C, C-8a_carb),

163.9 (d, J = 249.1 Hz, 1C, C-4_phenyl), 166.7 (1C, C-3_oxadiazole), 169.8

1_phenyl), 125.7 (1C, C-7_carb), 131.0 (1C, C-3_carb), 133.6 (d, J = 9.5 Hz,

1C, C-6_phenyl), 136.1 (1C, C-9a_carb), 140.4 (1C, C-8a_carb), 162.9 (d,

J = 253.3 Hz, 1C, C-4_phenyl), 166.6 (1C, C-3_oxadiazole), 168.5 (1C,

CONH), 179.6 (1C, C-5_oxadiazole).

(1C, CONH), 180.2 (1C, C-5_oxadiazole). IR (neat): m

(cm^À1) = 3444

(m, O–H), 3286 (m, N–H), 2966 (m, C–H, aliph), 1651 (s, NH–C@O).

6.3.21. 4-[3-(4-Chlorophenyl)-1,2,4-oxadiazol-5-yl]-N-[9-(2-

hydroxyethyl)-9H-_carbazol-3-yl]butanamide (18c)

6.3.19. 4-[3-(2-Bromo-4-ﬂuorophenyl)-1,2,4-oxadiazol-5-yl]-N-

[9-(2-hydroxyethyl)-9H-_carbazol-3-yl]butanamide (18a)

According to the General Procedure C, 11c (475 mg, 1.8 mmol)

was treated with 12 (400 mg, 1.8 mmol), COMU^Ò(920 mg,

2.1 mmol) and triethylamine (0.5 mL, 3.5 mmol) in DMF (16 mL).

This mixture was stirred for 22 h at <10 °C. The residue was puri-

ﬁed by fc (d = 8 cm, l = 12 cm, cyclohexane/ethyl acetate 20:80, R_f

0.38 (ethyl acetate)). Colorless solid, mp 221–222 °C, yield

648 mg (77%). C₂₆H₂₃ClN₄O₃(475.0 g/mol). Exact mass (ESI): m/

z = calcd for C₂₆H₂₃³⁵ClN₄O₃Na 497.1272 found 497.1279. Purity

(HPLC): 97.7% (t_R= 20.31 min). ¹H NMR (DMSO-d₆): d (ppm) =

2.16 (quint, J = 7.2 Hz, 2H, CH₂CH₂CH₂CONH), 3.12 (t, J = 7.0 Hz,

2H, CH₂CH₂CH₂CONH), 3.76 (q, J = 5.5 Hz, 2H, NCH₂CH₂OHCH_2-

CH₂), 4.39 (t, J = 5.6 Hz, 2H, NCH₂CH₂OHCH₂CH₂), 4.86 (t,

J = 5.4 Hz, 1H, NCH₂CH₂OHCH₂CH₂), 7.15 (t, J = 7.1 Hz, 1H, 6-H_carb),

7.41 (t, J = 7.7 Hz, 1H, 7-H_carb), 7.49–7.53 (m, 2H, 1-H_carb, 2-H_carb),

7.57 (d, J = 8.2 Hz, 1H, 8-H_carb), 7.60–7.64 (m, 2H, 2-H_phenyl, 6-

According to the General Procedure C, 11a (586 mg, 1.8 mmol)

was treated with 12 (400 mg, 1.8 mmol), COMU^Ò(920 mg,

2.1 mmol) and triethylamine (0.5 mL, 3.5 mmol) in DMF (21 mL).

This mixture was stirred for 24 h at <10 °C. The residue was puri-

ﬁed by fc (d = 6 cm, l = 10 cm, cyclohexane/ethyl acetate 5:95, R_f

0.55 (ethyl acetate)). Colorless solid, mp 173–174 °C, yield

702 mg (73%). C₂₆H₂₂BrFN₄O₃(537.4 g/mol). Exact mass (ESI): m/

z = calcd for C₂₆H₂₂⁷⁹BrFN₄O₃H 537.0935 found 537.0933. Purity

(HPLC): 98.4% (t_R= 20.53 min). ¹H NMR (DMSO-d₆): d (ppm) =

2.10–2.20 (m, 2H, CH₂CH₂CH₂CONH), 3.14 (t, J = 7.3 Hz, 2H, CH_2-

CH₂CH₂CONH), 3.76 (q, J = 5.6 Hz, 2H, NCH₂CH₂OHCH₂CH₂), 4.40

(t, J = 5.7 Hz, 2H, NCH₂CH₂OHCH₂CH₂), 4.86 (t, J = 5.2 Hz, 1H, NCH_2-

CH₂OHCH₂CH₂), 7.16 (t, J = 7.5 Hz, 1H, 6-H_carb), 7.38–7.47 (m, 2H,

7-H_carb, 5-H_phenyl), 7.52 (s, 2H, 1-H_carb, 2-H_carb), 7.57 (d, J = 8.3 Hz,

1H, 8-H_carb), 7.84 (dd, J = 8.6/2.5 Hz, 1H, 3-H_phenyl), 7.89 (dd,

J = 8.7/6.2 Hz, 1H, 6-H_phenyl), 8.02 (d, J = 7.8 Hz, 1H, 5-H_carb), 8.39

(s, 1H, 4-H_carb), 9.95 (s, 1H, CONH). The signal for CH₂CONH is

overlaid by the solvent peak, but can be seen in CDCl₃. ¹³C NMR

(DMSO-d₆): d (ppm) = 22.0 (1C, CH₂CH₂CH₂CONH), 25.3 (1C, CH_2-

CH₂CH₂CONH), 34.9 (1C, CH₂CH₂CH₂CONH), 45.3 (1C, NCH₂CH_2-

OHCH₂CH₂), 59.5 (1C, NCH₂CH₂OHCH₂CH₂), 109.4 (1C, C-8_carb),

109.6 (1C, C-1_carb), 111.0 (1C, C-4_carb), 115.5 (d, J = 21.6 Hz, 1C, C-

H_phenyl), 7.98–8.04 (m, 3H, 5-H_carb, 3-H_phenyl, 5-H_phenyl), 8.38 (s,

1H, 4-H_carb), 9.95 (s, 1H, CONH). The signal for CH₂CH₂CH₂CONH

is overlaid by the solvent peak, but can be seen in CDCl₃. ¹³C

NMR (DMSO-d₆): d (ppm) = 22.7 (1C, CH₂CH₂CH₂CONH), 26.1 (1C,

CH₂CH₂CH₂CONH), 35.6 (1C, CH₂CH₂CH₂CONH), 45.9 (1C, NCH_2-

CH₂OHCH₂CH₂), 60.2 (1C, NCH₂CH₂OHCH₂CH₂), 110.0 (1C, C-8_carb),

110.3 (1C, C-1_carb), 111.7 (1C, C-4_carb), 119.1 (1C, C-2_carb), 119.5 (1C,

C-6_carb), 120.5 (1C, C-5_carb), 122.3 (1C, C-4a_carb), 122.6 (1C, C-

5_phenyl), 118.5 (1C, C-2_carb), 118.9 (1C, C-6_carb), 119.9 (1C, C-5_carb),

4b_carb), 125.9 (1C, C-7_carb), 126.2 (1C, C-1_phenyl), 129.5 (2C, C-3_phenyl,

121.3 (d, J = 25.2 Hz, 1C, C-3_phenyl), 121.6 (1C, C-4a_carb), 122.0 (1C,

C-4b_carb), 122.2 (d, J = 10.1 Hz, 1C, C-2_phenyl), 123.5 (d, J = 3.9 Hz,

1C, C-1_phenyl), 125.6 (1C, C-7_carb), 131.1 (1C, C-3_carb), 133.7 (d,

J = 9.3 Hz, 1C, C-6_phenyl), 137.0 (1C, C-9a_carb), 140.8 (1C, C-8a_carb),

163.2 (d, J = 261.0 Hz, 1C, C-4_phenyl), 166.6 (1C, C-3_oxadiazole), 169.8

C-5_phenyl), 130.1 (2C, C-2_phenyl, C-6_phenyl), 131.8 (1C, C-3_carb), 136.9

(1C, C-9a_carb), 137.7 (1C, C-4_phenyl), 142.5 (1C, C-8a_carb), 167.4 (1C,

C-3_oxadiazole), 170.5 (1C, CONH), 181.0 (1C, C-5_oxadiazole). IR (neat):

m

(cm^À1)=3376 (m, O–H), 3278 (m, N–H), 2970 (m, C–H, aliph),

1647 (s, NH–C@O).

(1C, CONH), 179.6 (1C, C-5_oxadiazole). IR (neat):

m

(cm^À1) = 3367

(m, N–H), 1662 (s, NH–C@O).

6.3.22. 4-[3-(4-Methylphenyl)-1,2,4-oxadiazol-5-yl]-N-[9-(2-

hydroxyethyl)-9H-_carbazol-3-yl]butanamide (18d)

6.3.20. 4-[3-(4-Fluorophenyl)-1,2,4-oxadiazol-5-yl]-N-[9-(2-

hydroxyethyl)-9H-_carbazol-3-yl]butanamide (18b)

According to the General Procedure C, 11d (440 mg, 1.8 mmol)

was treated with 12 (400 mg, 1.8 mmol), COMU^Ò(915 mg,

2.1 mmol) and triethylamine (0.5 mL, 3.5 mmol) in DMF (18 mL).

This mixture was stirred for 24 h at <10 °C. The residue was puri-

ﬁed by fc (d = 5 cm, l = 15 cm, cyclohexane/ethyl acetate 20:80, R_f

0.39 (ethyl acetate)). Colorless solid, mp 206–207 °C, yield

439 mg (54%). C₂₇H₂₆N₄O₃(454.5 g/mol). Exact mass (ESI): m/

According to the General Procedure C, 11b (450 mg, 1.8 mmol)

was treated with 12 (400 mg, 1.8 mmol), COMU^Ò(920 mg,

2.1 mmol) and triethylamine (0.5 mL, 3.5 mmol) in DMF (21 mL).

This mixture was stirred for 25 h at <10 °C. The residue was puri-

ﬁed by fc (d = 8 cm, l = 12 cm, cyclohexane/ethyl acetate 10:90, R_f

0.41 (ethyl acetate)). Colorless solid, mp 170–171 °C, yield

566 mg (69%). C₂₆H₂₃FN₄O₃(458.5 g/mol). Exact mass (ESI): m/

z = calcd for C₂₆H₂₃FN₄O₃H 459.1847 found 459.1827. Purity

(HPLC): 95.7% (t_R= 20.04 min). ¹H NMR (DMSO-d₆): d (ppm) =

2.11–2.15 (m, 2H, CH₂CH₂CH₂CONH), 3.11 (t, J = 6.9 Hz, 2H, CH_2-

CH₂CH₂CONH), 3.75 (q, J = 5.2 Hz, 2H, NCH₂CH₂OHCH₂CH₂), 4.39

(t, J = 5.6 Hz, 2H, NCH₂CH₂OHCH₂CH₂), 4.86 (t, J = 5.4 Hz, 1H, NCH_2-

CH₂OHCH₂CH₂), 7.15 (t, J = 7.9 Hz, 1H, 6-H_carb), 7.37–7.44 (m, 3H,

7-H_carb, 3-H_phenyl, 5-H_phenyl), 7.48–7.55 (m, 2H, 1-H_carb, 2-H_carb),

7.57 (d, J = 8.3 Hz, 1H, 8-H_carb), 8.01 (d, J = 7.8 Hz, 1H, 5-H_carb),

8.03–8.07 (m, 2H, 2-H_phenyl, 6-H_phenyl), 8.38 (s, 1H, 4-H_carb), 9.94

(s, 1H, CONH). The signal for CH₂CH₂CH₂CONH is overlaid by the

solvent peak, but can be seen in CDCl₃. ¹³C NMR (DMSO-d₆): d

(ppm) = 22.0 (1C, CH₂CH₂CH₂CONH), 25.4 (1C, CH₂CH₂CH₂CONH),

35.0 (1C, CH₂CH₂CH₂CONH), 45.3 (1C, NCH₂CH₂OHCH₂CH₂), 59.5

(1C, NCH₂CH₂OHCH₂CH₂), 109.4 (1C, C-8_carb), 109.6 (1C, C-1_carb),

111.1 (1C, C-4_carb), 116.4 (d, J = 22.2 Hz, 2C, C-3_phenyl, C-5_phenyl),

118.4 (1C, C-2_carb), 118.9 (1C, C-6_carb), 119.9 (1C, C-5_carb), 121.7

(1C, C-4a_carb), 121.9 (1C, C-4b_carb), 122.9 (d, J = 3.1 Hz, 1C,

z = calcd for

C₂₇H₂₆N₄O₃Na 476.1818 found 476.1819. Purity

(HPLC): 96.7% (t_R= 20.41 min). ¹H NMR (DMSO-d₆): d (ppm) =

2.16 (quint, J = 7.3 Hz, 2H, CH₂CH₂CH₂CONH), 2.38 (s, 3H, CH₃),

3.10 (t, J = 7.1 Hz, 2H, CH₂CH₂CH₂CONH), 3.76 (q, J = 5.7 Hz, 2H,

NCH₂CH₂OHCH₂CH₂), 4.40 (t, J = 5.6 Hz, 2H, NCH₂CH₂OHCH₂CH₂),

4.86 (t, J = 5.4 Hz, 1H, NCH₂CH₂OHCH₂CH₂), 7.15 (t, J = 7.1 Hz, 1H,

6-H_carb), 7.36 (d, J = 8.0 Hz, 2H, 3-H_phenyl, 5-H_phenyl), 7.42 (t,

J = 8.2 Hz, 1H, 7-H_carb), 7.49–7.53 (m, 2H, 1-H_carb, 2-H_carb), 7.57

(d, J = 8.2 Hz, 1H, 8-H_carb), 7.91 ((d, J = 8.2 Hz, 2H, 2-H_phenyl, 6-

H_phenyl), 8.01 (d, J = 7.7 Hz, 1H, 5-H_carb), 8.38 (s, 1H, 4-H_carb), 9.95

(s, 1H, CONH). The signal for CH₂CH₂CH₂CONH is overlaid by the

solvent peak, but can be seen in CDCl₃. ¹³C NMR (DMSO-d₆): d

(ppm) = 21.1(1C, CH₃), 22.0 (1C, CH₂CH₂CH₂CONH), 25.4 (1C, CH_2-

CH₂CH₂CONH), 35.0 (1C, CH₂CH₂CH₂CONH), 45.3 (1C, NCH₂CH_2-

OHCH₂CH₂), 59.5 (1C, NCH₂CH₂OHCH₂CH₂), 109.4 (1C, C-8_carb),

109.6 (1C, C-1_carb), 111.1 (1C, C-4_carb), 118.5 (1C, C-2_carb), 118.9

(1C, C-6_carb), 119.9 (1C, C-5_carb), 121.7 (1C, C-4a_carb), 122.0 (1C, C-

4b_carb), 123.6 (1C, C-1_phenyl) 125.6 (1C, C-7_carb), 127.0 (2C, C-3_phenyl

,

C-5_phenyl), 129.8 (2C, C-2_phenyl, C-6_phenyl), 131.1 (1C, C-3_carb), 137.0

C. Lueg et al. / Bioorg. Med. Chem. 21 (2013) 7481–7498

7491

(1C, C-9a_carb), 140.8 (1C, C-8a_carb), 141.4 (1C, C-4_phenyl), 167.5 (1C,

C-3_oxadiazole), 168.8 (1C, CONH), 179.9 (1C, C-5_oxadiazole). IR (neat):

m

136.6 (1C, C-9a_carb), 140.5 (1C, C-8a_carb), 163.9 (d, J = 247.2 Hz,

1C, C-4_phenyl), 166.7 (1C, C-3_oxadiazole), 169.8 (1C, CONH), 180.2

(1C, C-5_oxadiazole). The signal for NCH₂CH₂CH₂OH is overlaid by

(cm^À1) = 3363 (m, O–H), 3275 (m, N–H), 2970 (m, C–H, aliph),

1647 (s, NH–C@O).

the solvent peak. IR (neat): m

(cm^À1) = 3414 (m, O–H), 3298 (m,

N–H), 2935 (m, C–H, aliph), 1640 (s, NH–C@O).

6.3.23. 4-[3-(2-Bromo-4-ﬂuorophenyl)-1,2,4-oxadiazol-5-yl]-N-

[9-(3-hydroxypropyl)-9H-carbazol-3-yl]butanamide (19a)

According to the General Procedure C, 11a (250 mg, 0.8 mmol)

was treated with 13 (183 mg, 0.8 mmol), COMU^Ò(390 mg,

0.9 mmol) and triethylamine (0.2 mL, 1.4 mmol) in DMF (14 mL).

This mixture was stirred for 24 h at <10 °C. The residue was puri-

ﬁed by fc (d = 6 cm, l = 10 cm, cyclohexane/ethyl acetate 20:80, R_f

0.28 (ethyl acetate)). Colorless solid, mp 128–129 °C, yield

400 mg (90%). C₂₇H₂₄BrFN₄O₃(551.4 g/mol). Exact mass (ESI): m/

z = calcd for C₂₇H₂₄⁷⁹BrFN₄O₃H 551.1089 found 551.1077. Purity

(HPLC): 96.4% (t_R= 20.84 min). ¹H NMR (DMSO-d₆): d (ppm) =

1.82–1.92 (m, 2H, NCH₂CH₂CH₂OH), 2.07–2.18 (m, 2H, CH₂CH₂CH_2-

CONH), 3.11 (t, J = 7.2 Hz, 2H, CH₂CH₂CH₂CONH), 3.33–3.41 (m, 2H,

NCH₂CH₂CH₂OH), 4.40 (t, J = 6.7 Hz, 2H, NCH₂CH₂CH₂OH), 4.61 (t,

J = 4.9 Hz, 1H, NCH₂CH₂CH₂OH), 7.13 (t, J = 7.4 Hz, 1H, 6-H_carb),

7.36–7.40 (m, 2H, 7-H_carb, 5-H_phenyl), 7.52–7.54 (m, 2H, 1-H_carb, 2-

6.3.25. 4-[3-(4-Chlorophenyl)-1,2,4-oxadiazol-5-yl]-N-[9-(3-

hydroxypropyl)-9H-carbazol-3-yl]butanamide (19c)

According to the General Procedure C, 11c (405 mg, 1.5 mmol)

was treated with 13 (365 mg, 1.5 mmol), COMU^Ò(782 mg,

1.8 mmol) and triethylamine (0.4 mL, 2.8 mmol) in DMF (14 mL).

This mixture was stirred for 22 h at <10 °C. The residue was puri-

ﬁed by fc (d = 5 cm, l = 12 cm, cyclohexane/ethyl acetate 20:80, R_f

0.36 (ethyl acetate)). Colorless solid, mp 163–165 °C, yield

412 mg (56%). C₂₇H₂₅ClN₄O₃(489.0 g/mol). Exact mass (ESI): m/

z = calcd for C₂₇H₂₅³⁵ClN₄O₃H 489.1688 found 489.1724. Purity

(HPLC): 98.9% (t_R= 21.15 min). ¹H NMR (DMSO-d₆): d (ppm) =

1.85–1.92 (m, 2H, NCH₂CH₂CH₂OH), 2.11–2.21 (quint, J = 7.3 Hz,

2H, CH₂CH₂CH₂CONH), 3.10 (t, J = 7.3 Hz, 2H, CH₂CH₂CH₂CONH),

3.36–3.44 (m, 2H, NCH₂CH₂CH₂OH), 4.40 (t, J = 6.5 Hz, 2H, NCH_2-

CH₂OHCH₂CH₂), 4.64 (t, J = 4.8 Hz, 1H, NCH₂CH₂CH₂OH), 7.15 (t,

J = 7.3 Hz, 1H, 6-H_carb), 7.43 (t, J = 8.2 Hz, 1H, 7-H_carb), 7.49–7.53

(m, 2H, 1-H_carb, 2-H_carb), 7.57 (d, J = 8.2 Hz, 1H, 8-H_carb), 7.61 (d,

J = 8.5 Hz, 2H, 2-H_phenyl, 6-H_phenyl), 7.99–8.01 (m, 3H, 5-H_carb, 3-

H_carb), 7.54 (d, J = 8.2 Hz, 1H, 8-H_carb), 7.81 (dd, J = 8.6/2.5 Hz, 1H,

3-H_phenyl), 7.86 (dd, J = 8.7/6.0 Hz, 1H, 6-H_phenyl), 8.01 (d,

J = 7.7 Hz, 1H, 5-H_carb), 8.37 (s, 1H, 4-H_carb), 9.94 (s, 1H, CONH).

The signal for CH₂CH₂CH₂CONH is overlaid by the solvent peak,

but can be seen in CDCl₃. ¹³C NMR (DMSO-d₆): d (ppm) = 22.0

(1C, CH₂CH₂CH₂CONH), 25.3 (1C, CH₂CH₂CH₂CONH), 31.8 (1C,

NCH₂CH₂CH₂OH), 35.0 (1C, CH₂CH₂CH₂CONH), 58.0 (1C, NCH₂CH_2-

CH₂OH), 109.1 (1C, C-8_carb), 109.3 (1C, C-1_carb), 111.2 (1C, C-4_carb),

115.4 (d, J = 21.6 Hz, 1C, C-5_phenyl), 118.5 (1C, C-2_carb), 119.0 (1C, C-

H_phenyl, 5-H_phenyl), 8.39 (s, 1H, 4-H_carb), 9.96 (s, 1H, CONH). The sig-

nal for CH₂CH₂CH₂CONH is overlaid by the solvent peak, but can be

seen in CDCl₃. ¹³C NMR (DMSO-d₆): d (ppm) = 21.8 (1C, CH₂CH_2-

CH₂CONH), 25.2 (1C, CH₂CH₂CH₂CONH), 31.5 (1C, NCH₂CH₂CH_2-

OH), 34.7 (1C, CH₂CH₂CH₂CONH), 57.8 (1C, NCH₂CH₂CH₂OH),

108.8 (1C, C-8_carb), 109.0 (1C, C-1_carb), 111.0 (1C, C-4_carb), 118.2

(1C, C-2_carb), 118.7 (1C, C-6_carb), 119.8 (1C, C-5_carb), 121.4 (1C, C-

4a_carb), 121.7 (1C, C-4b_carb), 125.0 (1C, C-1_phenyl) 125.5 (1C, C-7_carb),

128.5 (2C, C-3_phenyl, C-5_phenyl), 129.1 (2C, C-2_phenyl, C-6_phenyl), 130.9

(1C, C-3_carb), 135.9 (1C, C-4_phenyl), 136.4 (1C, C-9a_carb), 140.8 (1C, C-

8a_carb), 166.5 (1C, C-3_oxadiazole), 169.6 (1C, CONH), 180.1 (1C, C-5_oxa-

_diazole). The signal for NCH₂CH₂CH₂OH is overlaid by the solvent

6

_carb), 120.1 (1C, C-5_carb), 121.3 (d, J = 25.0 Hz, 1C, C-3_phenyl), 121.7

(1C, C-4a_carb), 121.9 (1C, C-4b_carb), 122.2 (d, J = 10.1 Hz, 1C, C-

_phenyl), 124.5 (d, J = 3.5 Hz, 1C, C-1_phenyl), 125.7 (1C, C-7_carb),

2

131.2 (1C, C-3_carb), 133.7 (d, J = 9.6 Hz, 1C, C-6_phenyl), 136.6 (1C,

C-9a_carb), 140.5 (1C, C-8a_carb), 163.7 (d, J = 253.3 Hz, 1C, C-4_phenyl),

166.6 (1C, C-3_oxadiazole), 169.8 (1C, CONH), 179.6 (1C, C-5_oxadiazole).

The signal for NCH₂CH₂CH₂OH is overlaid by the solvent peak.

peak. IR (neat):

m

(cm^À1) = 3376 (m, O–H), 3282 (m, N–H), 2970

IR (neat):

m

(cm^À1) = 3670 (w, O–H), 3278 (m, N–H), 1647 (s,

(m, C–H, aliph), 1651 (s, NH–C@O).

NH–C@O).

6.3.26. 4-[3-(4-Methylphenyl)-1,2,4-oxadiazol-5-yl]-N-[9-(3-

hydroxypropyl)-9H-carbazol-3-yl]butanamide (19d)

6.3.24. 4-[3-(4-Fluorophenyl)-1,2,4-oxadiazol-5-yl]-N-[9-(3-

hydroxypropyl)-9H-carbazol-3-yl]butanamide (19b)

According to the General Procedure C, 11d (375 mg, 1.5 mmol)

was treated with 13 (365 mg, 1.5 mmol), COMU^Ò(780 mg,

1.8 mmol) and triethylamine (0.4 mL, 2.8 mmol) in DMF (15 mL).

This mixture was stirred for 24 h at <10 °C. The residue was puri-

ﬁed by fc (d = 5 cm, l = 12 cm, cyclohexane/ethyl acetate 20:80, R_f

0.43 (ethyl acetate)). Colorless solid, mp 162–163 °C, yield

411 mg (58%). C₂₈H₂₈N₄O₃(468.6 g/mol). Exact mass (ESI): m/

According to the General Procedure C, 11b (380 mg, 1.5 mmol)

was treated with 13 (365 mg, 1.5 mmol), COMU^Ò(380 mg,

1.8 mmol) and triethylamine (0.4 mL, 2.8 mmol) in DMF (14 mL).

This mixture was stirred for 24 h at <10 °C. The residue was puri-

ﬁed by fc (d = 5 cm, l = 12 cm, cyclohexane/ethyl acetate 15:85, R_f

0.37 (ethyl acetate)). Colorless solid, mp 161–162 °C, yield

335 mg (41%). C₂₇H₂₅FN₄O₃(472.5 g/mol). Exact mass (ESI): m/

z = calcd for C₂₇H₂₅FN₄O₃H 473.1983 found 473.1988. Purity

(HPLC): 98.2% (t_R= 20.22 min). ¹H NMR (CDCl₃): d (ppm) = 2.06–

2.13 (m, 2H, CH₂CH₂CH₂CONH), 2.34–2.43 (m, 2H, NCH₂CH₂CH_2-

OH), 2.60 (t, J = 7.1 Hz, 2H, CH₂CH₂CH₂CONH), 3.14 (t, J = 7.1 Hz,

2H, CH₂CH₂CH₂CONH), 3.60 (t, J = 5.8 Hz, 2H, NCH₂CH₂CH₂OH),

z = calcd for

C₂₈H₂₈N₄O₃H 469.2234 found 469.2237. Purity

(HPLC): 98.1% (t_R= 21.15 min). ¹H NMR (DMSO-d₆): d (ppm) =

1.84–1.94 (m, 2H, NCH₂CH₂CH₂OH), 2.16 (quint, J = 7.3 Hz, 2H,

NCH₂CH₂CH₂OH), 2.37 (s, 3H, CH₃), 3.12 (t, J = 7.4 Hz, 2H, CH₂CH_2-

CH₂CONH), 3.36–3.44 (m, 2H, NCH₂CH₂CH₂OH), 4.40 (t, J = 6.8 Hz,

2H, NCH₂CH₂CH₂OH), 4.64 (t, J = 4.9 Hz, 1H, NCH₂CH₂OHCH₂CH₂),

7.16 (t, J = 7.4 Hz, 1H, 6-H_carb), 7.43 (t, J = 7.1 Hz, 1H, 7-H_carb),

7.50–7.53 (m, 2H, 1-H_carb, 2-H_carb), 7.57 (d, J = 8.2 Hz, 1H, 8-H_carb),

7.59–7.64 (m, 2H, 2-H_phenyl, 6-H_phenyl), 7.99–8.04 (d, J = 7.7 Hz, 3H,

5-H_carb, 3-H_phenyl, 5-H_phenyl), 8.39 (s, 1H, 4-H_carb), 9.96 (s, 1H,

CONH). The signal for CH₂CH₂CH₂CONH is overlaid by the solvent

peak, but can be seen in CDCl₃. ¹³C NMR (DMSO-d₆): d (ppm) =

21.9 (1C, CH₃), 22.0 (1C, CH₂CH₂CH₂CONH), 25.4 (1C, CH₂CH₂CH_2-

CONH), 31.8 (1C, NCH₂CH₂CH₂OH), 35.0 (1C, CH₂CH₂CH₂CONH),

58.0 (1C, NCH₂CH₂CH₂OH), 109.0 (1C, C-8_carb), 109.3 (1C, C-1_carb),

111.2 (1C, C-4_carb), 118.5 (1C, C-2_carb), 119.0 (1C, C-6_carb), 120.1

(1C, C-5_carb), 121.7 (1C, C-4a_carb), 121.9 (1C, C-4b_carb), 125.2 (1C,

C-7_carb), 125.7 (1C, C-1_phenyl), 128.8 (2C, C-3_phenyl, C-5_phenyl), 129.4

4.46 (t, J = 6.6 Hz, 2H, NCH₂CH₂OHCH₂CH₂), 7.17 (m, 2H, 3-H_phenyl

5-H_phenyl), 7.19–7.24 (m, 1H, 6-H_carb), 7.38–7.52 (m, 5H, 1-H_carb, 2-

_carb, 4-H_carb, 7-H_carb, 8-H_carb), 748–7.55 (m, 3H, 5-H_carb, 2-H_phenyl

,

H

,

6-H_phenyl), 8.32 (s, 1H, CONH). A signal for the OH-moiety is not

been seen. ¹³C NMR (DMSO-d₆): d (ppm) = 22.0 (1C, CH₂CH₂CH_2-

CONH), 25.4 (1C, CH₂CH₂CH₂CONH), 31.8 (1C, NCH₂CH₂CH₂OH),

35.0 (1C, CH₂CH₂CH₂CONH), 59.5 (1C, NCH₂CH₂CH₂OH), 109.0

(1C, C-8_carb), 109.3 (1C, C-1_carb), 111.2 (1C, C-4_carb), 116.4 (d,

J = 22.2 Hz, 2C, C-3_phenyl, C-5_phenyl), 118.5 (1C, C-2_carb), 119.0 (1C,

C-6_carb), 120.1 (1C, C-5_carb), 121.7 (1C, C-4a_carb), 121.9 (1C, C-

4b_carb), 122.9 (d, J = 3.1 Hz, 1C, C-1_phenyl), 125.7 (1C, C-7_carb),

129.5 (d, J = 9.1 Hz, 2C, C-2_phenyl, C-6_phenyl), 131.2 (1C, C-3_carb),

7492

C. Lueg et al. / Bioorg. Med. Chem. 21 (2013) 7481–7498

(2C, C-2_phenyl, C-6_phenyl), 131.2 (1C, C-3_carb), 136.2 (1C, C-9a_carb),

136.6 (1C, C-4_phenyl), 140.5 (1C, C-8a_carb), 166.7 (1C, C-3_oxadiazole),

169.8 (1C, CONH), 180.3 (1C, C-5_oxadiazole). The signal for NCH₂CH_2-

CH₂OH is overlaid by the solvent peak. IR (neat):

(m, O–H), 3290 (m, N–H), 2947 (m, C–H, aliph), 1639 (s, NH–C@O).

6.3.29. 3-[3-(4-Chlorophenyl)-1,2,4-oxadiazol-5-yl]-N-[9-(2-

ﬂuoroethyl)-9H-carbazol-3-yl]propanamide (20c)

According to the General Procedure D, 15c (400 mg, 0.9 mmol)

was treated with XtalFluor-E^Ò(300 mg, 1.3 mmol) and triethyl-

amine trihydroﬂuoride (0.2 mL, 1.2 mmol) in CH₂Cl₂(50 mL)

at–78 °C. Theproductwaspuriﬁedbyfc (d = 5.5 cm, l = 15 cm, cyclo-

hexane/ethyl acetate 25:75, R_f0.25 (cyclohexane/ethyl acetate

50:50)). Colorless solid, mp 220–221 °C, yield 120 mg (30%).

m

(cm^À1) = 3468

6.3.27. 3-[3-(2-Bromo-4-ﬂuorophenyl)-1,2,4-oxadiazol-5-yl]-N-

[9-(2-ﬂuoroethyl)-9H-carbazol-3-yl]propanamide (20a)

C

₂₅H₂₀ClFN₄O₂(462.9 g/mol). Exact mass (APCI): m/z = calcd for

According to the General Procedure D, 15a (400 mg, 0.8 mmol)

was treated with XtalFluor-E^Ò(263 mg, 1.2 mmol) and triethyl-

amine trihydroﬂuoride (0.2 mL, 1.2 mmol) in CH₂Cl₂(35 mL)

at –78 °C. The product was puriﬁed by fc (d = 6 cm, l = 15 cm, cyclo-

hexane/ethyl acetate 20:80, R_f= 0.53 (ethyl acetate)). Colorless so-

lid, mp 201 °C, yield 82 mg (20%). C₂₅H₁₉BrF₂N₄O₂(525.3 g/mol).

Exact mass (APCI): m/z = calcd for C₂₅H₁₉⁷⁹BrF₂N₄O₂H 525.0732

found 525.0757. Purity (HPLC): 96.7% (t_R= 21.46 min). ¹H NMR

(CDCl₃): d (ppm) = 2.97 (t, J = 7.0 Hz, 2H, CH₂CH₂CONHCH₂CH₂),

3.39 (t, J = 7.0 Hz, 2H, CH₂CH₂CONHCH₂CH₂), 4.51 (dt, J = 24.2/

5.1 Hz, 2H, NCH₂CH₂F), 4.72 (dt, J = 46.8/5.1 Hz, 2H, NCH₂CH₂F),

7.03–7.09 (m, 1H, 5-H_phenyl), 7.16 (t, J = 7.0 Hz, 1H, 6-H_carb), 7.27

(d, J = 8.6 Hz, 1H, 1-H_carb), 7.32 (d, J = 8.2 Hz, 1H, 8-H_carb), 7.36–

7.43 (m, 3H, 2-H_carb, 7-H_carb, 3-H_phenyl), 7.56 (s, 1H, CONH), 7.76

(dd, J = 8.7/6.0 Hz, 1H, 6-H_phenyl), 7.97 (d, J = 7.8 Hz, 1H, 5-H_carb),

8.41 (d, J = 1.8 Hz, 1H, 4-H_carb). ¹³C NMR (DMSO-d₆): d (ppm) =

21.8 (1C, CH₂CH₂CONHCH₂CH₂), 32.0 (1C, CH₂CH₂CONHCH₂CH₂),

42.9 (d, J = 19.7 Hz, 1C, NCH₂CH₂F), 82.6 (d, J = 167.9 Hz, 1C, NCH_2-

CH₂F), 109.5 (1C, C-8_carb), 109.6 (1C, C-1_carb), 110.9 (1 C, C-4_carb),

115.5 (d, J = 21.7 Hz,1C, C-5_phenyl), 118.8 (1C, C-2_carb), 118.9 (1C,

C-6_carb), 120.0 (1C, C-5_carb), 121.4 (d, J = 25.1 Hz, 1C, C-3_phenyl),

121.9 (1C, C-4a_carb), 122.1 (1C, C-4b_carb), 122.2 (d, J = 9.9 Hz, 1C,

C-2_phenyl), 124.5 (d, J = 3.4 Hz,1C, C-1_phenyl), 125.8 (1C, C-7_carb),

131.4 (1C, C-3_carb), 133.6 (d, J = 9.3 Hz, 1C, C-6_phenyl), 136.7 (1C,

C-9a_carb), 140.6 (1C, C-8a_carb), 162.9 (d, J = 253.2 Hz, 1C, C-4_phenyl),

166.4 (1C, C-3_oxadiazole), 168.5 (1C, CONH), 179.6 (1C, C-5_oxadiazole).

C

₂₅H₂₀³⁵ClFN₄O₂H 463.1332 found 463.1304. Purity (HPLC): 98.6%

(t_R= 22.00 min). ¹H NMR (CDCl₃): d (ppm) = 3.04 (t, J = 7.0 Hz, 2H,

CH₂CH₂CONHCH₂CH₂), 3.43 (t, J = 7.0 Hz, 2H, CH₂CH₂CONHCH_2-

CH₂), 4.58 (dt, J = 24.5/4.9 Hz, 2H, NCH₂CH₂F), 4.78 (dt, J = 46.8/

5.1 Hz, 2H, NCH₂CH₂F), 7.23 (t, J = 7.3 Hz, 1H, 6-H_carb), 7.30–7.40

(m, 2H, 1-H_carb, 7-H_carb,), 7.41–7.50 (m, 4H, 2-H_carb, 8-H_carb, 3-H_phenyl

,

5-H_phenyl), 7.65 (s, 1H, CONH), 8.00–8.07 (m, 3H, 5-H_carb, 2-H_phenyl, 6-

H_phenyl), 8.31(s, 1H, 4-H_carb). ¹³CNMR(DMSO-d₆):d(ppm) =21.9(1C,

CH₂CH₂CONHCH₂CH₂), 32.0 (1C, CH₂CH₂CONHCH₂CH₂), 42.9 (d,

J = 20.1 Hz, 1C, NCH₂CH₂F), 82.6 (d, J = 167.8 Hz, 1C, NCH₂CH₂F),

109.5 (1C, C-8_carb), 109.6 (1C, C-1_carb), 111.0 (1C, C-4_carb), 118.8

(1C, C-2_carb), 118.9 (1C, C-6_carb), 120.1 (1C, C-5_carb), 121.9 (1C, C-

4a_carb), 122.1 (1C, C-4b_carb), 125.2 (1C, C-1_phenyl), 125.8 (1C, C-7_carb),

129.5 (2C, C-3_phenyl, C-5_phenyl), 129.5 (2C, C-2_phenyl, C-6_phenyl), 131.3

(1C, C-3_carb), 136.2 (1C, C-4_phenyl), 136.8 (1C, C-9a_carb), 140.6 (1C, C-

8a_carb), 166.7 (1C, C-3_oxadiazole), 168.6 (1C, CONH), 180.4 (1C, C-5_oxa-

_diazole). IR (neat):

1654 (s, NH–C@O).

m

(cm^À1) = 3302 (m, N–H), 2954 (m, C–H, aliph),

6.3.30. N-[9-(2-Fluoroethyl)-9H-carbazol-3-yl]-3-[3-(4-

methylphenyl)-1,2,4-oxadiazol-5-yl]propanamide (20d)

According to the General Procedure D, 15d (300 mg, 0.7 mmol)

was treated with XtalFluor-E^Ò(233 mg, 1.0 mmol) and triethyl-

amine trihydroﬂuoride (0.2 mL, 1.2 mmol) in CH₂Cl₂(40 mL) at

À78 °C. The product was puriﬁed by fc (d = 5 cm, l = 10 cm, cyclo-

hexane/ethyl acetate 25:75, R_f0.48 (cyclohexane/ethyl acetate

40:60)). Colorless solid, mp 187–188 °C, yield 60 mg (20%). C₂₆H_23-

FN₄O₂(442.5 g/mol). Exact mass (APCI): m/z = calcd for C₂₆H₂₃FN₄O_2-

H 443.1878 found 443.1860. Purity (HPLC): 98.8% (t_R= 21.67 min).

¹H NMR (DMSO-d₆): d (ppm) = 2.37 (s, 3H, CH₃), 3.00 (t, J = 7.1 Hz,

2H, CH₂CH₂CONHCH₂CH₂), 3.31 (t, J = 6.3 Hz, 2H, CH₂CH₂CON-

HCH₂CH₂), 4.69 (dt, J = 13.9/4.1 Hz, 2H, NCH₂CH₂F), 4.78 (dt,

J = 37.5/4.8 Hz, 2H, NCH₂CH₂F), 7.18 (t, J = 7.5 Hz, 1H, 6-H_carb),

7.36 (d, J = 7.9 Hz, 2H, 3-H_phenyl, 5-H_phenyl), 7.56 (d, J = 8.7 Hz, 1H,

1-H_carb), 7.43 (t, J = 7.7 Hz, 1H, 7-H_carb), 7.52 (dd, J = 8.8/1.9 Hz,

1H, 2-H_carb), 7.56 (d, J = 8.7 Hz, 1H, 8-H_carb), 7.89 (d, J = 8.2 Hz,

2H, 2-H_phenyl, 6-H_phenyl), 8.04 (d, J = 7.6 Hz, 1H, 5-H_carb), 8.41 (s,

1H, 4-H_carb), 10.16 (s, 1H, CONH). ¹³C NMR (DMSO-d₆): d (ppm) =

21.1 (1C, CH₃), 22.1 (1C, CH₂CH₂CONHCH₂CH₂), 35.0 (1C, CH₂CH_2-

CONHCH₂CH₂), 42.9 (d, J = 19.8 Hz, 1C, NCH₂CH₂F), 82.6 (d,

J = 167.8 Hz, 1C, NCH₂CH₂F), 109.4 (1C, C-8_carb), 109.6 (1C, C-1_carb),

111.2 (1C, C-4_carb), 118.9 (1C, C-2_carb), 119.0 (1C, C-6_carb), 120.1 (1C,

C-5_carb), 121.9 (1C, C-4a_carb), 122.1 (1C, C-4b_carb), 123.6 (1C, C-

IR (neat):

m

(cm^À1) = 3267 (m, N–H), 2954 (m, C–H, aliph), 1647

(s, NH–C@O).

6.3.28. N-[9-(2-Fluoroethyl)-9H-carbazol-3-yl]-3-[3-(4-

ﬂuorophenyl)-1,2,4-oxadiazol-5-yl]propanamide (20b)

According to the General Procedure D, 15b (200 mg, 0.5 mmol)

was treated with XtalFluor-E^Ò(70 mg, 0.3 mmol) and triethyl-

amine trihydroﬂuoride (0.1 mL, 0.6 mmol) in CH₂Cl₂(40 mL)

at –78 °C. The product was puriﬁed by fc (d = 3 cm, l = 12 cm, cyclo-

hexane/ethyl acetate 20:80, R_f0.69 (ethyl acetate)). Colorless solid,

mp 206–208 °C, yield 26 mg (13%). C₂₅H₂₀F₂N₄O₂(446.5 g/mol).

Exact mass (APCI): m/z = calcd for C₂₅H₂₀F₂N₄O₂H 447.1627 found

447.1597. Purity (HPLC): 98.3% (t_R= 21.14 min). ¹H NMR (DMSO-

d₆): d (ppm) = 3.00 (t, J = 6.9 Hz, 2H, CH₂CH₂CONHCH₂CH₂), 3.31

(t, J = 6.8 Hz, 2H, CH₂CH₂CONHCH₂CH₂), 4.69 (dt, J = 13.9/4.1 Hz,

2H, NCH₂CH₂F), 4.78 (dt, J = 37.5/4.8 Hz, 2H, NCH₂CH₂F), 7.18 (t,

J = 7.3 Hz, 1H, 6-H_carb), 7.36–7.45 (m, 3H, 7-H_carb, 3-H_phenyl, 5-

H_phenyl), 7.56 (d, J = 8.7 Hz, 1H, 1-H_carb), 7.52 (dd, J = 8.8/1.8 Hz,

1_phenyl), 125.8 (1C, C-7_carb), 127.0 (2C, C-3_phenyl, C-5_phenyl), 129.8

1H, 2-H_carb), 7.56 (d, J = 8.7 Hz, 1H, 8-H_carb), 8.01–8.09 (m, 3H, 5-

(2C, C-2_phenyl, C-6_phenyl), 131.5 (1C, C-3_carb), 136.8 (1C, C-9a_carb),

140.7 (1C, C-8a_carb), 141.4 (1C, C-4_phenyl), 167.5 (1C, C-3_oxadiazole),

169.1 (1C, CONH), 179.9 (1C, C-5_oxadiazole). IR (neat):

3275 (m, N–H), 2927 (m, C–H, aliph), 1639 (s, NH–C@O).

H_carb, 2-H_phenyl, 6-H_phenyl), 8.41 (s, 1H, 4-H_carb), 10.16 (s, 1H, CONH).

¹³C NMR (DMSO-d₆): d (ppm) = 21.9 (1C, CH₂CH₂CONHCH₂CH₂),

32.0 (1C, CH₂CH₂CONHCH₂CH₂), 42.9 (d, J = 20.1 Hz, 1C, NCH₂CH_2-

F), 82.6 (d, J = 168.0 Hz, 1C, NCH₂CH₂F), 109.5 (1C, C-8_carb), 109.6

m

(cm^À1) =

(1C, C-1_carb), 110.9 (1C, C-4_carb), 116.5 (d, J = 22.1 Hz, 2C, C-3_phenyl

C-5_phenyl), 118.8 (1C, C-2_carb), 118.9 (1C, C-6_carb), 120.1 (1C, C-5_carb),

,

6.3.31. 3-[3-(4-Bromo-2-ﬂuorophenyl)-1,2,4-oxadiazol-5-yl)]-N-

[9-(2-ﬂuoroethyl)-9H-carbazol-3-yl]propanamide (20e)

121.9 (1C, C-4a_carb), 122.1 (1C, C-4b_carb), 122.9 (d, J = 3.1 Hz, 1C, C-

According to the General Procedure D, 15e (100 mg,

0.2 mmol) was treated with XtalFluor-E^Ò(66 mg, 0.3 mmol)

and triethylamine trihydroﬂuoride (0.14 mL, 0.9 mmol) in CH₂Cl₂

(15 mL) at À78 °C. The product was puriﬁed by fc (d = 2 cm,

l = 10 cm, cyclohexane/ethyl acetate 25:75, R_f= 0.41 (cyclohex-

ane/ethyl acetate 40:60)). Colorless solid, mp 207–210 °C, yield

1_phenyl), 125.8 (1C, C-7_carb), 129.5 (d, J = 9.0 Hz, 2C, C-2_phenyl, C-

6_phenyl), 131.3 (1C, C-3_carb), 136.8 (1C, C-9a_carb), 140.6 (1C, C-8a_carb),

163.9 (d, J = 249.1 Hz, 1C, C-4_phenyl), 166.9 (1C, C-3_oxadiazole), 168.6

(1C, CONH), 180.2 (1C, C-5_oxadiazole). IR (neat):

(cm^À1) = 3267

(m, N–H), 2939 (m, C–H, aliph), 1643 (s, NH–C@O).

m

C. Lueg et al. / Bioorg. Med. Chem. 21 (2013) 7481–7498

7493

90 mg (89%). C₂₅H₁₉BrF₂N₄O₂(525.3 g/mol). Exact mass (APCI):

m/z = calcd for

₂₅H₁₉⁷⁹BrF₂N₄O₂H 525.0732 found 525.0724.

for C₂₆H₂₁⁷⁹BrF₂N₄O₂H 539.0889 found 539.0881. Purity (HPLC):

97.4% (t_R= 22.41 min). ¹H NMR (DMSO-d₆): d (ppm) = 2.00–2.09

(m, 2H, NCH₂CH₂CH₂F), 2.99 (t, J = 7.0 Hz, 2H, CH₂CH₂CONHCH_2-

CH₂), 3.31 (t, J = 7.0 Hz, 2H, CH₂CH₂CONHCH₂CH₂), 3.98 (dt,

J = 38.5/4.3 Hz, 2H, NCH₂CH₂CH₂F), 4.38 (t, J = 6.8 Hz, 2H, NCH_2-

CH₂CH₂F), 7.14 (t, J = 7.1 Hz, 1H, 6-H_carb), 7.32–7.46 (m, 2H, 7-

C

Purity (HPLC): 98.3% (t_R= 20.46 min). ¹H NMR (DMSO-d₆): d

(ppm) = 3.02 (t, J = 7.0 Hz, 2H, CH₂CH₂CONHCH₂CH₂), 3.37 (t,

J = 6.9 Hz, 2H, CH₂CH₂CONHCH₂CH₂), 4.69 (dt, J = 18.3/4.3 Hz,

2H, NCH₂CH₂F), 4.78 (dt, J = 38.5/4.5 Hz, 2H, NCH₂CH₂F), 7.18

(t, J = 7.4 Hz, 1H, 6-H_carb), 7.43 (t, J = 7.7 Hz, 1H, 7-H_carb), 7.50–

7.58 (m, 2H, 1-H_carb, 2-H_carb), 7.60 (d, J = 8.3 Hz, 1H, 8-H_carb),

7.80 (td, J = 8.6/2.7 Hz, 1H, 5-H_phenyl), 8.05 (d, J = 7.8 Hz, 1H, 5-

H_carb, 5-H_phenyl), 7.47–7.57 (m, 3H, 1-H_carb, 2-H_carb, 8-H_carb),

7.81 (dd, J = 8.6/2.6 Hz, 1H, 3-H_phenyl), 7.88 (dd, J = 8.7/6.0 Hz,

1H, 6-H_phenyl), 8.02 (d, J = 7.7 Hz, 1H, 5-H_carb), 8.41 (d,

J = 1.7 Hz, 1H, 4-H_carb), 10.15 (s, 1H, CONH). ¹³C NMR (DMSO-

H_carb), 8.13 (dd, J = 8.7/2.6 Hz, 1H, 3-H_phenyl), 8.18 (dd, J = 8.9/

5.5 Hz, 1H, 6-H_phenyl), 8.41 (s, 1H, 4-H_carb), 10.17 (s, 1H, CONH).

¹³C NMR (DMSO-d₆): d (ppm) = 21.9 (1C, CH₂CH₂CONHCH₂CH₂),

31.9 (1C, CH₂CH₂CONHCH₂CH₂), 42.9 (d, J = 19.7 Hz, 1C, NCH_2-

CH₂F), 82.6 (d, J = 167.9 Hz, 1C, NCH₂CH₂F), 109.5 (1C, C-8_carb),

109.6 (1C, C-1_carb), 111.0 (1 C, C-4_carb), 111.8 (d, J = 10.3 Hz,1C,

C-4_phenyl), 116.2 (1C, C-2_carb), 118.9 (1C, C-6_carb), 120.1 (1C, C-

5_carb), 121.5 (d, J = 21.8 Hz, 1C, C-1_phenyl), 121.9 (1C, C-4a_carb),

122.1 (1C, C-4b_carb), 122.5 (d, J = 26.1 Hz, 1C, C-3_phenyl), 125.1

(d, J = 3.4 Hz,1C, C-5_phenyl), 125.8 (1C, C-7_carb), 131.3 (1C, C-3_carb),

132.6 (d, J = 9.3 Hz, 1C, C-6_phenyl), 136.8 (1C, C-9a_carb), 140.7 (1C,

C-8a_carb), 162.8 (d, J = 252.2 Hz, 1C, C-2_phenyl), 165.0 (1C, C-3_oxadi-

d₆):

d

(ppm) = 21.8 (1C, CH₂CH₂CONHCH₂CH₂), 29.4 (d,

J = 19.6 Hz, 1C, NCH₂CH₂CH₂F), 32.0 (1C, CH₂CH₂CONHCH₂CH₂),

38.4 (d, J = 5.1 Hz, 1C, NCH₂CH₂CH₂F), 81.4 (d, J = 167.9 Hz, 1C,

NCH₂CH₂CH₂F), 109.0 (1C, C-8_carb), 109.2 (1C, C-1_carb), 111.1 (1

C, C-4_carb), 115.5 (d, J = 21.6 Hz,1C, C-5_phenyl), 118.7 (1C, C-2_carb),

118.9 (1C, C-6_carb), 120.2 (1C, C-5_carb), 121.4 (d, J = 25.1 Hz, 1C, C-

3_phenyl), 121.8 (1C, C-4a_carb), 122.1 (1C, C-4b_carb), 122.2 (d,

J = 9.9 Hz, 1C, C-2_phenyl), 124.5 (d, J = 3.5 Hz,1C, C-1_phenyl), 125.9

(1C, C-7_carb), 131.3 (1C, C-3_carb), 133.6 (d, J = 9.4 Hz, 1C, C-6_phenyl),

136.5 (1C, C-9a_carb), 140.4 (1C, C-8a_carb), 162.9 (d, J = 253.4 Hz,

1C, C-4_phenyl), 166.6 (1C, C-3_oxadiazole), 168.6 (1C, CONH), 179.6

_azole), 168.5 (1C, CONH), 180.6 (1C, C-5_oxadiazole). IR (neat):

m

(1C, C-5_oxadiazole). IR (neat): m

(cm^À1) = 3286 (m, N–H), 2970

(m, C–H, aliph), 1643 (s, NH–C@O).

(cm^À1) = 3332 (m, N–H), 2935 (m, C–H, aliph), 1689 (s, NH–

C@O).

6.3.34. 3-[3-(4-Fluorophenyl)-1,2,4-oxadiazol-5-yl]-N-[9-(3-

ﬂuoropropyl)-9H-carbazol-3-yl]propanamide (21b)

6.3.32. 3-[3-(2-Cyano-4-ﬂuorophenyl)-1,2,4-oxadiazol-5-yl]-N-

[9-(2-ﬂuoroethyl)-9H-carbazol-3-yl]propanamide (20f)

According to the General Procedure D, 16b (240 mg,

0.5 mmol) was treated with XtalFluor-E^Ò(180 mg, 0.8 mmol)

and triethylamine trihydroﬂuoride (0.12 mL, 0.8 mmol) in CH₂Cl₂

(30 mL) at –78 °C. The product was puriﬁed by fc (d = 6 cm,

l = 10 cm, cyclohexane/ethyl acetate 25:75, R_f0.71 (cyclohex-

ane/ethyl acetate 50:50)). Colorless solid, mp 175–176 °C, yield

218 mg (91%). C₂₆H₂₂F₂N₄O₂(460.5 g/mol). Exact mass (APCI):

m/z = calcd for C₂₆H₂₂F₂N₄O₂H 461.1783 found 461.1781. Purity

(HPLC): 99.2% (t_R= 22.49 min). ¹H NMR (DMSO-d₆): d (ppm) =

2.06–2.20 (m, 2H, NCH₂CH₂CH₂F), 3.00 (t, J = 7.1 Hz, 2H, CH₂CH_2-

CONHCH₂CH₂), 3.28 (t, J = 7.1 Hz, 2H, CH₂CH₂CONHCH₂CH₂), 4.40

(dt, J = 41.7/5.7 Hz, 2H, NCH₂CH₂CH₂F), 4.47–4.50 (m, 2H, NCH_2-

CH₂CH₂F), 7.17 (t, J = 7.1 Hz, 1H, 6-H_carb), 7.36–7.47 (m, 3H, 7-

According to the General Procedure D, 15f (250 mg, 0.5 mmol)

was treated with XtalFluor-E^Ò(170 mg, 0.8 mmol) and triethyl-

amine trihydroﬂuoride (0.25 mL, 1.6 mmol) in CH₂Cl₂(25 mL)

at –78 °C. The product was puriﬁed by fc (d = 3.5 cm, l = 10 cm,

cyclohexane/ethyl acetate 25:75, R_f0.50 (cyclohexane/ethyl ace-

tate 40:60)). Colorless solid, mp 203–205 °C, yield 97 mg (41%).

C₂₆H₁₉F₂N₅O₂(471.5 g/mol). Exact mass (APCI): m/z = calcd for

C

₂₆H₁₉F₂N₅O₂H 472.1580 found 472.1521. Purity (HPLC): 98.0%

(t_R= 21.49 min). ¹H NMR (DMSO-d₆):

d

(ppm) = 3.01 (t,

J = 6.9 Hz, 2H, CH₂CH₂CONHCH₂CH₂), 3.34 (t, J = 6.9 Hz, 2H, CH_2-

CH₂CONHCH₂CH₂), 4.69 (dt, J = 14.6/4.2 Hz, 2H, NCH₂CH₂F), 4.78

(dt, J = 38.5/4.1 Hz, 2H, NCH₂CH₂F), 7.18 (t, J = 7.4 Hz, 1H, 6-

H

_carb), 7.43 (t, J = 7.7 Hz, 1H, 7-H_carb), 7.51–7.65 (m, 4H, 1-H_carb

,

H_carb, 3-H_phenyl, 5-H_phenyl), 7.51–7.54 (m, 2H, 1-H_carb, 2-H_carb),

2-H_carb3-H_phenyl5-H_phenyl), 7.63 (d, J = 8.6 Hz, 1H, 8-H_carb),

,

7.56 (d, J = 8.3 Hz, 1H, 8-H_carb), 8.02–8.08 (m, 3H, 5-H_carb, 2-

7.95 (t, J = 8.0 Hz, 1H, 6-H_phenyl), 8.04 (d, J = 7.8 Hz, 1H, 5-H_carb),

8.40 (s, 1H, 4-H_carb), 10.16 (s, 1H, CONH). ¹³C NMR (DMSO-d₆):

d (ppm) = 21.8 (1C, CH₂CH₂CONHCH₂CH₂), 31.9 (1C, CH₂CH₂CON-

HCH₂CH₂), 42.9 (d, J = 19.7 Hz, 1C, NCH₂CH₂F), 82.0 (d,

J = 167.9 Hz, 1C, NCH₂CH₂F), 109.4 (1C, C-8_carb), 109.5 (2C, C-

H_phenyl, 6-H_phenyl), 8.41 (s, 1H, 4-H_carb), 10.16 (s, 1H, CONH).

¹³C NMR (DMSO-d₆): d (ppm) = 22.1 (1C, CH₂CH₂CONHCH₂CH₂),

29.4 (d, J = 19.7 Hz, NCH₂CH₂CH₂F), 35.0 (1C, CH₂CH₂CONHCH_2-

CH₂), 38.5 (d, J = 5.3 Hz, 1C, NCH₂CH₂CH₂F), 81.4 (d,

J = 161.9 Hz, 1C, NCH₂CH₂CH₂F), 108.9 (1C, C-8_carb), 109.1 (1C,

1

_carb, C-2_phenyl), 110.9 (1C, C-4_carb), 118.8 (1C, C-2_carb), 118.9

C-1_carb), 111.3 (1C, C-4_carb), 116.4 (d, J = 22.2 Hz, 2C, C-3_phenyl

C-5_phenyl), 118.7 (1C, C-2_carb), 119.1 (1C, C-6_carb), 120.2 (1C, C-

_carb), 121.8 (1C, C-4a_carb), 122.1 (1C, C-4b_carb), 122.9 (d,

,

(1C, C-6_carb), 119.2 (d, J = 3.2 Hz, 1C, CN), 120.1 (1C, C-5_carb),

120.2 (d, J = 22.0 Hz, 1C, C-5_phenyl), 122.5 (d, J = 24.3 Hz, 1C, C-

3_phenyl), 121.9 (1C, C-4a_carb), 122.1 (1C, C-4b_carb), 125.8 (1C, C-

5

J = 2.9 Hz, 1C, C-1_phenyl), 125.8 (1C, C-7_carb), 129.5 (d, J = 9.0 Hz,

2C, C-2_phenyl, C-6_phenyl), 131.4 (1C, C-3_carb), 136.5 (1C, C-9a_carb),

140.4 (1C, C-8a_carb), 163.9 (d, J = 249.1 Hz, 1C, C-4_phenyl), 166.8

(1C, C-3_oxadiazole), 169.9(1C, CONH), 180.2 (1C, C-5_oxadiazole). IR

7_carb), 128.5 (d, J = 3.6 Hz, 1C, C-1 phenyl), 131.3 (1C, C-3_carb),

132.6 (d, J = 9.7 Hz, 1C, C-6_phenyl), 136.8 (1C, C-9a_carb), 140.8

(1C, C-8a_carb), 157.1 (d, J = 250.3 Hz, 1C, C-4_phenyl), 166.4 (1C, C-

3_oxadiazole), 168.6 (1C, CONH), 179.9 (1C, C-5_oxadiazole). IR (neat):

(neat): m

(cm^À1) = 3302 (m, N–H), 2954 (m, C–H, aliph), 1654

m

(cm^À1) = 3329 (m, N–H), 2943 (m, C–H, aliph), 2233 (w, -

(s, NH–C@O).

CN), 1685 (s, NH–C@O).

6.3.35. 3-[3-(4-Chlorophenyl)-1,2,4-oxadiazol-5-yl]-N-[9-(3-

ﬂuoropropyl)-9H-carbazol-3-yl]propanamide (21c)

6.3.33. 3-[3-(2-Bromo-4-ﬂuorophenyl)-1,2,4-oxadiazol-5-yl]-N-

[9-(3-ﬂuoropropyl)-9H-carbazol-3-yl]propanamide (21a)

According to the General Procedure D, 16a (300 mg,

0.6 mmol) was treated with XtalFluor-E^Ò(192 mg, 0.8 mmol)

and triethylamine trihydroﬂuoride (0.14 mL, 0.8 mmol) in CH₂Cl₂

(25 mL) at –78 °C. The product was puriﬁed by fc (d = 5 cm,

l = 15 cm, cyclohexane/ethyl acetate 25:75, R_f0.68 (ethyl

acetate)). Colorless solid, mp 161–162 °C, yield 107 mg (33%).

According to the General Procedure D, 16c (300 mg, 0.6 mmol)

was treated with XtalFluor-E^Ò(220 mg, 1.0 mmol) and triethyl-

amine trihydroﬂuoride (0.3 mL, 1.8 mmol) in CH₂Cl₂(30 mL) at

À78 °C. The product was puriﬁed by fc (d = 5 cm, l = 8 cm, cyclo-

hexane/ethyl acetate 25:75, R_f0.40 (cyclohexane/ethyl acetate

50:50)). Colorless solid, mp 174–175 °C, yield 139 mg (48%). C_26-

H₂₂ClFN₄O₂(477.0 g/mol). Exact mass (APCI): m/z = calcd for C_26-

H₂₂³⁵ClFN₄O₂H 477.1488 found 477.1508. Purity (HPLC): 96.9%

C₂₆H₂₁BrF₂N₄O₂(539.4 g/mol). Exact mass (APCI): m/z = calcd

7494

C. Lueg et al. / Bioorg. Med. Chem. 21 (2013) 7481–7498

(t_R= 22.79 min). ¹H NMR (DMSO-d₆): d (ppm) = 2.07–2.20 (m, 2H,

NCH₂CH₂CH₂F), 3.01 (t, J = 7.4 Hz, 2H, CH₂CH₂CONHCH₂CH₂), 3.31

(t, J = 7.0 Hz, 2H, CH₂CH₂CH₂CONH), 4.41 (dt, J = 45.2/5.0 Hz, 2H,

NCH₂CH₂CH₂F), 4.78 (t, J = 6.8 Hz, 2H, NCH₂CH₂CH₂F), 7.17 (t,

J = 7.4 Hz, 1H, 6-H_carb), 7.44 (t, J = 7.4 Hz, 1H, 7-H_carb), 7.51–7.56

(m, 2H, 7-H_carb, 5-H_phenyl), 7.50–7.57 (m, 2H, 2-H_carb, 8-H_carb),

7.60 (d, J = 8.5 Hz, 1H, 1-H_carb), 7.83 (dd, J = 8.6/1.8 Hz, 1H, 3-

H

_phenyl), 7.88 (dd, J = 8.1/6.6 Hz, 1H, 6-H_phenyl), 8.04 (d, J = 7.4 Hz,

1H, 5-H_carb), 8.40 (s, 1H, 4-H_carb), 10.14 (s, 1H, CONH). ¹³C NMR

(DMSO-d₆): d (ppm) = 22.1 (1C, CH₂CH₂CONHCH₂CH₂), 25.5 (d,

J = 10.6 Hz, 1C, NCH₂CH₂CH₂CH₂F), 29.5 (d, J = 27.6 Hz, 1C, NCH_2-

CH₂CH₂CH₂F), 35.1 (1C, CH₂CH₂CONHCH₂CH₂), 43.1 (d, J = 5.1 Hz,

1C, NCH₂CH₂CH₂CH₂F), 81.4 (d, J = 167.9 Hz, 1C, NCH₂CH₂CH₂CH_2-

F), 109.6 (1C, C-8_carb), 109.8 (1C, C-1_carb), 111.9 (1 C, C-4_carb),

116.1 (d, J = 21.6 Hz,1C, C-5_phenyl), 119.4 (1C, C-2_carb), 119.7 (1C,

C-6_carb), 120.9 (1C, C-5_carb), 122.0 (d, J = 25.0 Hz, 1C, C-3_phenyl),

122.5 (1C, C-4a_carb), 122.7 (1C, C-4b_carb), 122.8 (d, J = 10.0 Hz, 1C,

C-2_phenyl), 125.2 (d, J = 3.5 Hz,1C, C-1_phenyl), 126.5 (1C, C-7_carb),

132.0 (1C, C-3_carb), 134.3 (d, J = 9.4 Hz, 1C, C-6_phenyl), 137.1 (1C,

C-9a_carb), 140.0 (1C, C-8a_carb), 163.5 (d, J = 253.3 Hz, 1C, C-4_phenyl),

167.3 (1C, C-3_oxadiazole), 170.5 (1C, CONH), 180.3 (1C, C-5_oxadiazole).

(m, 3H,1-H_carb, 2-H_carb, 8-H_carb), 7.63 (d, J = 8.2 Hz, 2H, 3-H_phenyl

,

5-H_phenyl), 8.01 (d, J = 8.1 Hz, 2H, 2-H_phenyl, 6-H_phenyl), 8.04 (d,

J = 7.8 Hz, 1H, 5-H_carb), 8.42 (s, 1H, 4-H_carb), 10.17 (s, 1H, CONH).

¹³C NMR (DMSO-d₆): d (ppm) = 21.9 (1C, CH₂CH₂CONHCH₂CH₂),

29.4 (d, J = 19.5 Hz, NCH₂CH₂CH₂F), 32.0 (1C, CH₂CH₂CONHCH_2-

CH₂), 38.4 (d, J = 5.0 Hz, 1C, NCH₂CH₂CH₂F), 81.4 (d, J = 162.1 Hz,

1C, NCH₂CH₂CH₂F), 109.0 (1C, C-8_carb), 109.2 (1C, C-1_carb), 111.1

(1C, C-4_carb), 118.7 (1C, C-2_carb), 118.9 (1C, C-6_carb), 120.2 (1C, C-

5_carb), 121.9 (1C, C-4a_carb), 122.0 (1C, C-4b_carb), 125.2 (1C, C-1_phenyl),

125.9 (1C, C-7_carb), 128.8 (2C, C-3_phenyl, C-5_phenyl), 129.5 (2C, C-

2

_phenyl, C-6_phenyl), 131.2 (1C, C-3_carb), 136.2 (1C, C-4_phenyl), 136.5

(1C, C-9a_carb), 140.4 (1C, C-8a_carb), 166.7 (1C, C-3_oxadiazole), 168.6

(1C, CONH), 180.4 (1C, C-5_oxadiazole). IR (neat):

(cm^À1) = 3298

(m, N–H), 2958 (m, C–H, aliph), 1654 (s, NH–C@O).

IR (neat):

m

(cm^À1) = 3267 (m, N–H), 3074 (m, C–H, arom), 1651

m

(s, NH–C@O).

6.3.38. 4-[3-(2-Bromo-4-ﬂuorophenyl)-1,2,4-oxadiazol-5-yl]-N-

[9-(2-ﬂuoroethyl)-9H-carbazol-3-yl]butanamide (23a)

6.3.36. N-[9-(3-Fluoropropyl)-9H-carbazol-3-yl]-3-[3-(4-

methylphenyl)-1,2,4-oxadiazol-5-yl]propanamide (21d)

According to the General Procedure D, 18a (500 mg, 0.9 mmol)

was treated with XtalFluor-E^Ò(320 mg, 1.4 mmol) and triethyl-

amine trihydroﬂuoride (0.3 mL, 1.8 mmol) in CH₂Cl₂(32 mL) at –

78 °C. The product was puriﬁed by fc (d = 6 cm, l = 10 cm, cyclohex-

ane/ethyl acetate 25:75, R_f0.44 (ethyl acetate)). Colorless solid, mp

158–159 °C, yield 118 mg (24%). C₂₆H₂₁BrF₂N₄O₂(539.4 g/mol).

Exact mass (APCI): m/z = calcd for C₂₆H₂₁⁷⁹BrF₂N₄O₂H 539.0889

found 539.0924. Purity (HPLC): 98.7% (t_R= 21.95 min). ¹H NMR

(CDCl₃): d (ppm) = 2.36 (quint, J = 7.1 Hz, 2H, CH₂CH₂CH₂CONH),

2.60 (t, J = 7.0 Hz, 2H, CH₂CH₂CH₂CONH), 3.16 (t, J = 7.0 Hz, 2H,

CH₂CH₂CH₂CONH), 4.57 (dt, J = 24.2/5.1 Hz, 2H, NCH₂CH₂F), 4.78

(dt, J = 46.8/5.1 Hz, 2H, NCH₂CH₂F), 7.10–7.17 (m, 1H, 6-H_carb),

7.20–7.25 (m, 1H, 7-H_carb), 7.33 (d, J = 8.6 Hz, 1H, 1-H_carb), 7.38

(d, J = 8.1 Hz, 1H, 8-H_carb), 7.44–7.50 (m, 3H, 2-H_carb, 3-H_phenyl, 5-

According to the General Procedure D, 16d (456 mg, 1.0 mmol)

was treated with XtalFluor-E^Ò(344 mg, 1.5 mmol) and triethyl-

amine trihydroﬂuoride (0.25 mL, 1.6 mmol) in CH₂Cl₂(55 mL) at

À78 °C. The product was puriﬁed by fc (d = 6 cm, l = 10 cm, cyclo-

hexane/ethyl acetate 25:75, R_f0.55 (cyclohexane/ethyl acetate

40:60)). Colorless solid, mp 173–174 °C, yield 177 mg (38%). C_27-

H₂₅FN₄O₂(456.5 g/mol). Exact mass (APCI): m/z = calcd for C₂₇H_25-

FN₄OH 457.2034 found 457.2055. Purity (HPLC): 98.3%

(t_R= 22.22 min). ¹H NMR (DMSO-d₆): d (ppm) = 2.06–2.20 (m, 2H,

NCH₂CH₂CH₂F), 2.37 (s, 3H, CH₃), 2.99 (t, J = 6.9 Hz, 2H, CH₂CH_2-

CONHCH₂CH₂), 3.30 (t, J = 7.1 Hz, 2H, CH₂CH₂CONHCH₂CH₂), 4.41

(dt, J = 45.0/5.7 Hz, 2H, NCH₂CH₂CH₂F), 4.48 (t, J = 6.8 Hz, 2H,

NCH₂CH₂CH₂F), 7.17 (t, J = 7.4 Hz, 1H, 6-H_carb), 7.36 (d, J = 8.1 Hz,

2H, 3-H_phenyl, 5-H_phenyl), 7.44 (t, J = 7.8 Hz, 1H, 7-H_carb), 7.49–7.54

(m, 2H,1-H_carb, 2-H_carb), 7.56 (d, J = 8.2 Hz, 1H, 8-H_carb), 7.89 (d,

J = 8.1 Hz, 2H, 2-H_phenyl, 6-H_phenyl), 8.05 (d, J = 7.8 Hz, 1H, 5-H_carb),

8.401 (s, 1H, 4-H_carb), 10.15 (s, 1H, CONH). ¹³C NMR (DMSO-d₆):

d (ppm) = 21.1 (1C, CH₃), 21.9 (1C, CH₂CH₂CONHCH₂CH₂), 29.4 (d,

J = 19.6 Hz, NCH₂CH₂CH₂F), 32.0 (1C, CH₂CH₂CONHCH₂CH₂), 38.4

(d, J = 5.1 Hz, 1C, NCH₂CH₂CH₂F), 81.4 (d, J = 162.1 Hz, 1C, NCH_2-

CH₂CH₂F), 109.0 (1C, C-8_carb), 109.1 (1C, C-1_carb), 111.1 (1C, C-4_carb),

118.8 (1C, C-2_carb), 118.9 (1C, C-6_carb), 120.2 (1C, C-5_carb), 121.9 (1C,

C-4a_carb), 122.0 (1C, C-4b_carb), 123.6 (1C, C-1_phenyl), 125.9 (1C, C-

H_phenyl), 7.65 (s, 1H, CONH), 7.84 (dd, J = 8.7/6.0 Hz, 1H, 6-H_phenyl),

8.05 (d, J = 7.8 Hz, 1H, 5-H_carb), 8.34 (d, J = 2.0 Hz, 1H, 4-H_carb). ¹³C

NMR (DMSO-d₆): d (ppm) = 22.0 (1C, CH₂CH₂CH₂CONH), 25.3 (1C,

CH₂CH₂CH₂CONH), 34.9 (1C, CH₂CH₂CH₂CONH), 42.9 (d,

J = 20.2 Hz, 1C, NCH₂CH₂F), 82.6 (d, J = 167.8 Hz, 1C, NCH₂CH₂F),

109.4 (1C, C-8_carb), 109.6 (1C, C-1_carb), 111.1 (1 C, C-4_carb), 115.4

(d, J = 21.6 Hz,1C, C-5_phenyl), 118.8 (1C, C-2_carb), 118.9 (1C, C-6_carb),

120.0 (1C, C-5_carb), 121.2 (1C, C-4a_carb), 121.5 (1C, C-4b_carb), 122.0

(d, J = 21.9 Hz, 1C, C-3_phenyl)122.2 (d, J = 10.2 Hz, 1C, C-2_phenyl),

124.5 (d, J = 3.4 Hz,1C, C-1_phenyl), 125.8 (1C, C-7_carb), 131.5 (1C, C-

7_carb), 126.9 (2C, C-3_phenyl, C-5_phenyl), 129.8 (2C, C-2_phenyl, C-6_phenyl),

3_carb), 133.7 (d, J = 9.4 Hz, 1C, C-6_phenyl), 136.7 (1C, C-9a_carb),

131.3 (1C, C-3_carb), 136.5 (1C, C-9a_carb), 140.7 (1C, C-8a_carb), 141.4

(1C, C-4_phenyl), 167.4 (1C, C-3_oxadiazole), 168.6 (1C, CONH), 179.9

140.6 (1C, C-8a_carb), 162.8 (d, J = 253.2 Hz, 1C, C-4_phenyl), 166.6

(1C, C-3_oxadiazole), 169.9 (1C, CONH), 179.6 (1C, C-5_oxadiazole). IR

(1C, C-5_oxadiazoleC-5_oxadiazole). IR (neat):

m

(cm^À1) = 3305 (m, N–H),

(neat): m

(cm^À1) = 3290 (m, N–H), 2935 (m, C–H. aliph), 1639 (s,

2970 (m, C–H, aliph), 1651 (s, NH–C@O).

NH–C@O).

6.3.37. 3-[3-(2-Bromo-4-ﬂuorophenyl)-1,2,4-oxadiazol-5-yl]-N-

[9-(4-ﬂuorobutyl)-9H-carbazol-3-yl] propanamide (22a)

6.3.39. N-[9-(2-Fluoroethyl)-9H-carbazol-3-yl]-4-[3-(4-

ﬂuorophenyl)-1,2,4-oxadiazol-5-yl]butanamide (23b)

According to the General Procedure D, 17a (180 mg, 0.3 mmol)

was treated with XtalFluor-E^Ò(110 mg, 0.5 mmol) and triethyl-

amine trihydroﬂuoride (0.16 mL, 1.0 mmol) in CH₂Cl₂(30 mL) at

–78 °C. The product was puriﬁed by fc (d = 5 cm, l = 15 cm, cyclo-

hexane/ethyl acetate 25:75, R_f0.86 (ethyl acetate)). Colorless solid,

mp 169–162 °C, yield 28 mg (14%). C₂₇H₂₃BrF₂N₄O₂(553.4 g/mol).

Exact mass (APCI): m/z = calcd for C₂₇H₂₃⁷⁹BrF₂N₄O₂H 553.1045

found 553.1004. Purity (HPLC): 98.7% (t_R= 22.61 min). ¹H NMR

According to the General Procedure D, 18b (428 mg, 1.0 mmol)

was treated with XtalFluor-E^Ò(320 mg, 1.4 mmol) and triethyl-

amine trihydroﬂuoride (0.25 mL, 1.6 mmol) in CH₂Cl₂(50 mL) at

À78 °C. The product was puriﬁed by fc (d = 5 cm, l = 8 cm, cyclo-

hexane/ethyl acetate 25:75, R_f0.62 (ethyl acetate)). Colorless solid,

mp 119–180 °C, yield 113 mg (27%). C₂₆H₂₂F₂N₄O₂(460.5 g/mol).

Exact mass (APCI): m/z = calcd for C₂₆H₂₂F₂N₄O₂H 461.1783 found

461.1750. Purity (HPLC): 95.1% (t_R= 21.57 min). ¹H NMR (CDCl₃): d

(ppm) = 2.32–2.42 (m, 2H, CH₂CH₂CH₂CONH), 2.59 (t, J = 7.0 Hz,

2H, CH₂CH₂CH₂CONH), 3.14 (t, J = 7.1 Hz, 2H, CH₂CH₂CH₂CONH),

4.59 (dt, J = 24.2/5.2 Hz, 2H, NCH₂CH₂F), 4.79 (dt, J = 46.9/5.2 Hz,

2H, NCH₂CH₂F), 7.16 (t, J = 8.7 Hz, 1H, 6-H_carb), 7.20–7.25 (m, 1H,

7-H_carb), 7.35 (d, J = 8.8 Hz, 1H, 1-H_carb), 7.40 (d, J = 8.1 Hz, 1H, 8-

(DMSO-d₆):

d (ppm) = 1.70–1.80 (m, 2H, NCH₂CH₂CH₂CH₂F),

1.82–1.92 (m, 2H, NCH₂CH₂CH₂CH₂F), 2.99 (t, J = 6.7 Hz, 2H, CH_2-

CH₂CONHCH₂CH₂), 3.35 (t, J = 7.0 Hz, 2H, CH₂CH₂CONHCH₂CH₂),

4.18 (dt, J = 41.5/5.6 Hz, 2H, NCH₂CH₂CH₂CH₂F), 4.48 (t, J = 6.0 Hz,

2H, NCH₂CH₂CH₂CH₂F), 7.16 (t, J = 7.2 Hz, 1H, 6-H_carb), 7.40–7.49

C. Lueg et al. / Bioorg. Med. Chem. 21 (2013) 7481–7498

7495

H_carb), 7.45–7.50 (m, 3H, 2-H_carb, 3-H_phenyl, 5-H_phenyl), 8.06 (d,

J = 7.1 Hz, 1H, 5-H_carb), 8.07–8.10 (m, 2H, 2-H_phenyl, 6-H_phenyl),

8.35 (d, J = 2.0 Hz, 1H, 4-H_carb). A signal for NH is not seen in the

spectrum. ¹³C NMR (DMSO-d₆): d (ppm) = 22.0 (1C, CH₂CH₂CH_2-

CONH), 25.4 (1C, CH₂CH₂CH₂CONH), 35.0 (1C, CH₂CH₂CH₂CONH),

42.9 (d, J = 20.3 Hz, 1C, NCH₂CH₂F), 82.6 (d, J = 167.9 Hz, 1C, NCH_2-

CH₂F), 109.4 (1C, C-8_carb), 109.6 (1C, C-1_carb), 111.1 (1C, C-4_carb),

116.4 (d, J = 22.2 Hz, 2C, C-3_phenyl, C-5_phenyl), 118.9 (1C, C-2_carb),

119.0 (1C, C-6_carb), 120.1 (1C, C-5_carb), 121.9 (1C, C-4a_carb), 122.1

(1C, C-4b_carb), 122.9 (d, J = 2.9 Hz, 1C, C-1_phenyl), 125.8 (1C, C-7_carb),

129.5 (d, J = 9.0 Hz, 2C, C-2_phenyl, C-6_phenyl), 131.5 (1C, C-3_carb),

136.8 (1C, C-9a_carb), 140.6 (1C, C-8a_carb), 163.9 (d, J = 249.1 Hz,

1C, C-4_phenyl), 166.7 (1C, C-3_oxadiazole), 169.9(1C, CONH), 180.2

d (ppm) = 21.9 (1C, CH₃), 22.05 (1C, CH₂CH₂CH₂CONH), 25.4 (1C,

CH₂CH₂CH₂CONH), 35.0 (1C, CH₂CH₂CH₂CONH), 42.9 (d,

J = 20.0 Hz, 1C, NCH₂CH₂F), 82.6 (d, J = 167.5 Hz, 1C, NCH₂CH₂F),

109.4 (1C, C-8_carb), 109.6 (1C, C-1_carb), 111.2 (1C, C-4_carb), 118.9

(1C, C-2_carb), 119.0 (1C, C-6_carb), 120.1 (1C, C-5_carb), 121.9 (1C, C-

4a_carb), 122.1 (1C, C-4b_carb), 123.6 (1C, C-1_phenyl), 125.8 (1C, C-7_carb),

127.0 (2C, C-3_phenyl, C-5_phenyl), 129.8 (2C, C-2_phenyl, C-6_phenyl), 131.5

(1C, C-3_carb), 136.8 (1C, C-9a_carb), 140.7 (1C, C-8a_carb), 141.4 (1C, C-

4

_phenyl), 167.5 (1C, C-3_oxadiazole), 169.1 (1C, CONH), 179.9 (1C, C-

5_oxadiazole). IR (neat):

m

(cm^À1) = 3282 (m, N–H), 2959 (m, C–H,

aliph), 1647 (s, NH–C@O).

6.3.42. 4-[3-(2-Bromo-4-ﬂuorophenyl)-1,2,4-oxadiazol-5-yl]-N-

[9-(3-ﬂuoropropyl)-9H-carbazol-3-yl]butanamide (24a)

(1C, C-5_oxadiazole). IR (neat):

C–H, aliph), 1647 (s, NH–C@O).

m

(cm^À1) = 3286 (m, N–H), 2951 (m,

According to the General Procedure D, 19a (180 mg, 0.3 mmol)

was treated with XtalFluor-E^Ò(221 mg, 0.9 mmol) and triethyl-

amine trihydroﬂuoride (0.13 mL, 0.8 mmol) in CH₂Cl₂(15 mL) at

À78 °C. The product was puriﬁed by fc (d = 5 cm, l = 10 cm, cyclo-

hexane/ethyl acetate 25:75, R_f0.78 (ethyl acetate)). Colorless solid,

mp 129–131 °C, yield 126 mg (71%). C₂₇H₂₃BrF₂N₄O₂(553.4 g/

6.3.40. 4-[3-(4-Chlorophenyl)-1,2,4-oxadiazol-5-yl]-N-[9-(2-

ﬂuoroethyl)-9H-carbazol-3-yl]butanamide (23c)

According to the General Procedure D, 18c (150 mg, 0.3 mmol)

was treated with XtalFluor-E^Ò(110 mg, 0.5 mmol) and triethyl-

amine trihydroﬂuoride (0.1 mL, 0.6 mmol) in CH₂Cl₂(20 mL) at

À78 °C. The product was puriﬁed by fc (d = 5 cm, l = 9 cm, cyclo-

hexane/ethyl acetate 25:75, R_f0.51 (cyclohexane/ethyl acetate

30:70)). Colorless solid, mp 201–202 °C, yield 69 mg (46%). C₂₆H_22-

mol). Exact mass (APCI): m/z = calcd for

C

₂₇H₂₃⁷⁹BrF₂N₄O₂H

553.1049 found 553.1044. Purity (HPLC): 99.0% (t_R= 22.31 min).

¹H NMR (CDCl₃): d (ppm) = 2.15–2.30 (m, 2H, NCH₂CH₂CH₂F),

2.37 (quint, J = 7.1 Hz, 2H, CH₂CH₂CH₂CONH), 2.60 (t, J = 7.0 Hz,

2H, CH₂CH₂CH₂CONH), 3.17 (t, J = 7.0 Hz, 2H, CH₂CH₂CH₂CONH),

4.39 (dt, J = 47.8/5.4 Hz, 2H, NCH₂CH₂CH₂F), 4.45 (t, J = 6.3 Hz, 2H,

NCH₂CH₂CH₂F), 7.15 (t, J = 8.3 Hz, 1H, 6-H_carb), 7.23 (t, J = 7.4 Hz,

1H, 7-H_carb), 7.36 (d, J = 8.7 Hz, 1H, 1-H_carb), 7.41 (d, J = 8.2 Hz,

1H, 8-H_carb), 7.44–7.52 (m, 3H, 2-H_carb, 3-H_phenyl, 5-H_phenyl), 7.66

(s, 1H, CONH), 7.85 (dd, J = 8.6/6.0 Hz, 1H, 6-H_phenyl), 8.05 (d,

J = 7.7 Hz, 1H, 5-H_carb), 8.35 (d, J = 1.7 Hz, 1H, 4-H_carb). ¹³C NMR

(DMSO-d₆): d (ppm) = 22.6 (1C, CH₂CH₂CH₂CONH), 26.0 (1C, CH_2-

CH₂CH₂CONH), 30.0 (d, J = 19.7 Hz, 1C, NCH₂CH₂CH₂F), 35.6 (1C,

CH₂CH₂CH₂CONH), 39.1 (d, J = 5.3 Hz, 1C, NCH₂CH₂CH₂F), 82.1 (d,

J = 167.2 Hz, 1C, NCH₂CH₂CH₂F), 109.6 (1C, C-8_carb), 109.8 (1C, C-

35-

ClFN₄O₂(477.0 g/mol). Exact mass (APCI): m/z = calcd for C₂₆H₂₂

ClFN₄O₂H 477.1488 found 477.1434. Purity (HPLC): 99.9%

(t_R= 22.00 min). ¹H NMR (DMSO-d₆): d (ppm) = 2.10–2.20 (m, 2H,

CH₂CH₂CH₂CONH), 3.10 (t, J = 7.4 Hz, 2H, CH₂CH₂CH₂CONH), 3.27

(t, J = 7.0 Hz, 2H, CH₂CH₂CH₂CONH), 4.68 (dt, J = 20.1/4.2 Hz, 2H,

NCH₂CH₂F), 4.78 (dt, J = 39.6/4.8 Hz, 2H, NCH₂CH₂F), 7.18 (t,

J = 7.4 Hz, 1H, 6-H_carb), 7.36 (d, J = 7.9 Hz, 2H, 3-H_phenyl, 5-H_phenyl),

7.43 (t, J = 7.7 Hz, 1H, 7-H_carb), 7.51–7.56 (m, 2H, 1-H_carb, 2-H_carb),

7.60 (d, J = 8.2 Hz, 1H, 8-H_carb), 7.90 (d, J = 8.1 Hz, 2H, 2-H_phenyl

,

6-H_phenyl), 8.03 (d, J = 7.7 Hz, 1H, 5-H_carb), 8.40 (s, 1H, 4-H_carb),

9.97 (s, 1H, CONH). ¹³C NMR (DMSO-d₆): d (ppm) = 21.9 (1C, CH_2-

CH₂CH₂CONH), 25.4 (1C, CH₂CH₂CH₂CONH), 35.0 (1C, CH₂CH₂CH_2-

CONH), 42.9 (d, J = 20.0 Hz, 1C, NCH₂CH₂F), 82.6 (d, J = 167.3 Hz,

1C, NCH₂CH₂F), 109.4 (1C, C-8_carb), 109.6 (1C, C-1_carb), 111.1 (1C,

C-4_carb), 118.9 (1C, C-2_carb), 119.0 (1C, C-6_carb), 120.0 (1C, C-5_carb),

121.9 (1C, C-4a_carb), 122.1 (1C, C-4b_carb), 125.2 (1C, C-1_phenyl),

125.7 (1C, C-7_carb), 129.4 (2C, C-3_phenyl, C-5_phenyl), 129.5 (2C, C-

1_carb), 111.9 (1 C, C-4_carb), 116.1 (d, J = 21.6 Hz,1C, C-5_phenyl),

119.4 (1C, C-2_carb), 119.7 (1C, C-6_carb), 120.9 (1C, C-5_carb), 122.0

(d, J = 25.0 Hz, 1C, C-3_phenyl), 122.5 (1C, C-4a_carb), 122.7 (1C, C-

4b_carb), 122.8 (d, J = 10.0 Hz, 1C, C-2_phenyl), 125.2 (d, J = 3.5 Hz,1C,

C-1_phenyl), 126.5 (1C, C-7_carb), 132.0 (1C, C-3_carb), 134.3 (d,

J = 9.4 Hz, 1C, C-6_phenyl), 137.1 (1C, C-9a_carb), 140.0 (1C, C-8a_carb),

163.5 (d, J = 253.3 Hz, 1C, C-4_phenyl), 167.3 (1C, C-3_oxadiazole), 170.5

2

_phenyl, C-6_phenyl), 131.5 (1C, C-3_carb), 136.2 (1C, C-4_phenyl), 136.8

(1C, C-9a_carb), 140.7 (1C, C-8a_carb), 166.8 (1C, C-3_oxadiazole), 169.9

(1C, CONH), 180.4 (1C, C-5_oxadiazole). IR (neat):

(cm^À1) = 3294

(m, N–H), 2954 (m, C–H, aliph), 1654 (s, NH–C@O).

(1C, CONH), 180.3 (1C, C-5_oxadiazole). IR (neat):

(m, N–H), 2966 (m, C–H, aliph), 1639 (s, NH–C@O).

m

(cm^À1) = 3286

m

6.3.43. 4-[3-(4-Fluorophenyl)-1,2,4-oxadiazol-5-yl]-N-[9-(3-

ﬂuoropropyl)-9H-carbazol-3-yl]butanamide (24b)

6.3.41. N-[9-(2-Fluoroethyl)-9H-carbazol-3-l]-4-[3-(4-

methylphenyl)-1,2,4-oxadiazol-5-yl]butanamide (23d)

According to the General Procedure D, 19b (300 mg, 0.6 mmol)

was treated with XtalFluor-E^Ò(221 mg, 1.0 mmol) and triethyl-

amine trihydroﬂuoride (0.2 mL, 1.2 mmol) in CH₂Cl₂(30 mL) at –

78 °C. The product was puriﬁed by fc (d = 5 cm, l = 9 cm, cyclohex-

ane/ethyl acetate 25:75, R_f0.73 (ethyl acetate)). Colorless solid, mp

146–147 °C, yield 116 mg (38%). C₂₇H₂₄F₂N₄O₂(474.5 g/mol). Exact

According to the General Procedure D, 18d (200 mg, 0.4 mmol)

was treated with XtalFluor-E^Ò(152 mg, 0.7 mmol) and triethyl-

amine trihydroﬂuoride (0.15 mL, 0.8 mmol) in CH₂Cl₂(25 mL) at

À78 °C. The product was puriﬁed by fc (d = 5 cm, l = 8 cm, cyclo-

hexane/ethyl acetate 25:75, R_f0.60 (cyclohexane/ethyl acetate

40:60)). Colorless solid, mp 197–198 °C, yield 80 mg (38%). C₂₇H_25-

FN₄O₂(456.5 g/mol). Exact mass (APCI): m/z = calcd for C₂₇H₂₅FN_4-

O₂Na 479.1775 found 479.1785. Purity (HPLC): 99.5%

mass (APCI): m/z = calcd for

475.1926. Purity (HPLC): 97.1% (t_R= 22.05 min). ¹H NMR (CDCl₃):

(ppm) = 2.16–2.31 (m, 2H, NCH₂CH₂CH₂F), 2.37 (quint,

C₂₇H₂₄F₂N₄O₂H 475.1940 found

d

(t_R= 22.25 min). ¹H NMR (DMSO-d₆):

d

(ppm) = 2.16 (quint,

J = 7.3 Hz, 2H, CH₂CH₂CH₂CONH), 2.59 (t, J = 7.1 Hz, 2H, CH₂CH_2-

CH₂CONH), 3.14 (t, J = 7.1 Hz, 2H, CH₂CH₂CH₂CONH), 4.39 (dt,

J = 47.2/5.4 Hz, NCH₂CH₂CH₂F), 4.46–4.48 (m, 2H, NCH₂CH₂CH₂F),

7.16 (t, J = 8.7 Hz, 1H, 6-H_carb), 7.23 (t, J = 7.7 Hz, 1H 7-H_carb), 7.37

(d, J = 8.7 Hz, 1H, 1-H_carb), 7.42 (d, J = 8.1 Hz, 1H, 8-H_carb), 7.45–

7.53 (m, 3H, 2-H_carb, 3-H_phenyl, 5-H_phenyl), 8.06 (d, J = 8.3 Hz, 1H,

5-H_carb), 8.08–8.11 (m, 2H, 2-H_phenyl, 6-H_phenyl), 8.35 (s, 1H, 4-

J = 7.4 Hz, 2H, CH₂CH₂CH₂CONH), 2.37 (s, 3H, CH₃), 3.27 (t,

J = 7.0 Hz, 2H, CH₂CH₂CH₂CONH), 4.68 (dt, J = 20.1/4.2 Hz, 2H,

NCH₂CH₂F), 4.78 (dt, J = 39.6/4.8 Hz, 2H, NCH₂CH₂F), 7.18 (t,

J = 7.4 Hz, 1H, 6-H_carb), 7.36 (d, J = 7.9 Hz, 2H, 3-H_phenyl, 5-H_phenyl),

7.43 (t, J = 7.7 Hz, 1H, 7-H_carb), 7.51–7.56 (m, 2H, 1-H_carb, 2-H_carb),

7.60 (d, J = 8.2 Hz, 1H, 8-H_carb), 7.90 (d, J = 8.1 Hz, 2H, 2-H_phenyl

,

6-H_phenyl), 8.03 (d, J = 7.7 Hz, 1H, 5-H_carb), 8.40 (s, 1H, 4-H_carb),

9.97 (s, 1H, CONH). The signal for CH₂CH₂CH₂CONH is overlaid by

the solvent peak, but can be seen in CDCl₃. ¹³C NMR (DMSO-d₆):

H

_carb). A signal for NH is not seen in the spectrum. ¹³C NMR

(DMSO-d₆): d (ppm) = 22.1 (1C, CH₂CH₂CH₂CONH), 25.4 (1C, CH_2-

CH₂CH₂CONH), 29.4 (d, J = 19.8 Hz, NCH₂CH₂CH₂F), 35.0 (1C, CH_2-

7496

C. Lueg et al. / Bioorg. Med. Chem. 21 (2013) 7481–7498

CH₂CH₂CONH), 38.5 (d, J = 5.3 Hz, 1C, NCH₂CH₂CH₂F), 81.4 (d,

J = 162.0 Hz, 1C, NCH₂CH₂CH₂F), 108.9 (1C, C-8_carb), 109.1 (1C, C-

120.2 (1C, C-5_carb), 121.8 (1C, C-4a_carb), 122.1 (1C, C-4b_carb), 122.1

(1C, C-1_phenyl), 125.9 (1C, C-7_carb), 128.8 (2C, C-3_phenyl, C-5_phenyl),

129.4 (2C, C-2_phenyl, C-6_phenyl), 131.4 (1C, C-3_carb), 136.2 (1C, C-

9a_carb), 136.8 (1C, C-4_phenyl), 140.7 (1C, C-8a_carb), 167.8 (1C, C-3_oxadi-

1_carb), 111.3 (1C, C-4_carb), 116.4 (d, J = 22.2 Hz, 2C, C-3_phenyl, C-

5_phenyl), 118.7 (1C, C-2_carb), 119.1 (1C, C-6_carb), 120.1 (1C, C-5_carb),

121.8 (1C, C-4a_carb), 122.0 (1C, C-4b_carb), 122.9 (d, J = 3.2 Hz, 1C,

C-1_phenyl), 125.8 (1C, C-7_carb), 129.5 (d, J = 9.0 Hz, 2C, C-2_phenyl, C-

_azole), 169.9 (1C, CONH), 180.4 (1C, C-5_oxadiazole). IR (neat): m

(cm^À1) =

3267 (m, N–H), 2970 (m, C–H, aliph), 1643 (s, NH–C@O).

6

_phenyl), 131.4 (1C, C-3_carb), 136.5 (1C, C-9a_carb), 140.4 (1C, C-8a_carb),

163.9 (d, J = 249.1 Hz, 1C, C-4_phenyl), 166.7 (1C, C-3_oxadiazole), 169.9

(1C, CONH), 180.2 (1C, C-5_oxadiazole). IR (neat):

(cm^À1) = 3294

(m, N–H), 2974 (m, C–H, aliph), 1643 (s, NH–C@O).

7. Experimental receptor binding studies

7.1. Materials

m

6.3.44. 4-[3-(4-Chlorophenyl)-1,2,4-oxadiazol-5-yl]-N-[9-(3-

ﬂuoropropyl)-9H-carbazol-3-yl] butanamide (24c)

The recombinant CHO cells expressing the CB₂receptor were a

generous donation of Professor Paul Prather (Little Rock, Arkansas,

USA). Cell incubator: Heracell 120 (Thermo Fisher Scientiﬁc,

Langenselbold, Germany). Homogenizers: Elvehjem Potter (B.

Braun Biotech International, Melsungen, Germany) and Soniprep

150, MSE, London, UK). Centrifuges: Cooling centrifuge model Roti-

na 35R (Hettich, Tuttlingen, Germany) and High-speed cooling cen-

trifuge model Sorvall RC-5C plus (Thermo Fisher Scientiﬁc,

Langenselbold, Germany). Multiplates: standard 96-well multi-

plates (Diagonal, Muenster, Germany). Shaker: self-made device

with adjustable temperature and tumbling speed (scientiﬁc work-

shop of the institute). Vortexer: Vortex Genie 2 (Thermo Fisher

Scientiﬁc, Langenselbold, Germany). Harvester: MicroBeta Filter-

Mate-96 Harvester. Filter: Printed Filtermat Typ A and B. Scintilla-

tor: Meltilex (Typ A or B) solid state scintillator. Scintillation

analyzer: MicroBeta Trilux (all Perkin Elmer LAS, Rodgau-Jüges-

heim, Germany). Chemicals and reagents were purchased from dif-

ferent commercial sources and of analytical grade.

According to the General Procedure D, 19c (200 mg, 0.4 mmol)

was treated with XtalFluor-E^Ò(140 mg, 0.6 mmol) and triethyl-

amine trihydroﬂuoride (0.2 mL, 1.2 mmol) in CH₂Cl₂(25 mL) at –

78 °C. The product was puriﬁed by fc (d = 6 cm, l = 8 cm, cyclohex-

ane/ethyl acetate 25:75, R_f0.65 (cyclohexane/ethyl acetate 30:70)).

Colorless solid, mp 178–180 °C, yield 109 mg (54%). C₂₇H₂₄ClFN₄O₂

(491.0 g/mol). Exact mass (APCI): m/z = calcd for C₂₇H₂₄³⁵ClFN₄O₂H

491.1645 found 491.1649. Purity (HPLC): 97.8% (t_R= 22.47 min).

¹H NMR (DMSO-d₆): d (ppm) = 2.10–2.22 (m, 4H, NCH₂CH₂CH₂F,

CH₂CH₂CH₂CONH), 3.28 (t, J = 7.0 Hz, 2H, CH₂CH₂CH₂CONH), 4.41

(dt, J = 42.6/5.7 Hz, 2H, NCH₂CH₂CH₂F), 4.47–4.49 (m, 2H, NCH_2-

CH₂CH₂F), 7.17 (t, J = 7.5 Hz, 1H, 6-H_carb), 7.44 (t, J = 7.6 Hz, 1H,

7-H_carb), 7.50 (d, J = 8.6 Hz, 1H,1-H_carb), 7.53 (dd, J = 8.3 Hz, 1H, 2-

H_carb), 7.56 (d, J = 8.3 Hz, 1H, 8-H_carb), 7.59–7.63 (m, 2H, 3-H_phenyl,

5-H_phenyl), 8.00–8.04 (m, 3H, 5-H_carb, 2-H_phenyl, 6-H_phenyl), 8.39 (s,

1H, 4-H_carb), 9.97 (s, 1H, CONH). The signal for CH₂CH₂CH₂CONH

is overlaid by the solvent peak, but can be seen in CDCl₃. ¹³C

NMR (DMSO-d₆): d (ppm) = 22.0 (1C, CH₂CH₂CH₂CONH), 25.4 (1C,

CH₂CH₂CH₂CONH), 29.4 (d, J = 19.2 Hz, NCH₂CH₂CH₂F), 35.0 (1C,

CH₂CH₂CH₂CONH), 38.5 (d, J = 5.3 Hz, 1C, NCH₂CH₂CH₂F), 81.4 (d,

J = 162.0 Hz, 1C, NCH₂CH₂CH₂F), 108.9 (1C, C-8_carb), 109.1 (1C, C-

7.2. Cell culture and preparation of membrane homogenates

from CB₂cells

The cell culture was modiﬁed according to Ref.⁵¹

CHO cells stably transfected with the gene for the human CB₂

receptor were grown in Dulbecco Modiﬁed Earl’s Medium (DMEM)

containing 10% of standardized FCS (Biochrom AG, Berlin, Ger-

1_carb), 111.3 (1C, C-4_carb), 118.7 (1C, C-2_carb), 119.1 (1C, C-6_carb),

120.2 (1C, C-5_carb), 121.8 (1C, C-4a_carb), 122.0 (1C, C-4b_carb), 125.2

(1C, C-1_phenyl), 125.8 (1C, C-7_carb), 128.8 (2C, C-3_phenyl, C-5_phenyl),

129.4 (2C, C-2_phenyl, C-6_phenyl), 131.3 (1C, C-3_carb), 136.5 (1C, C-

many) and 250 lg/mL Geneticin. The cells were harvested by

4_phenyl), 136.5 (1C, C-9a_carb), 140.4 (1C, C-8a_carb), 166.8 (1C, C-3_oxa-

scraping off the surface, resuspended in PBS buffer and pelleted

(10 min, 5000Âg) and the number of cells was determined using

an improved Neubauer’s counting chamber (VWR, Darmstadt, Ger-

many). Subsequently, the cells were lysed by sonication (4 °C,

6 Â 10 s cycles with breaks of 10 s). The resulting cell fragments

_diazole), 168.9 (1C, CONH), 180.3 (1C, C-5_oxadiazole). IR (neat):

m

(cm^À1) = 3267 (m, N–H), 2970 (m, C–H, aliph), 1643 (s, NH–C@O).

6.3.45. N-[9-(3-Fluoropropyl)-9H-carbazol-3-yl]-4-[3-(4-

methylphenyl)-1,2,4-oxadiazol-5-yl] butanamide (24d)

were centrifuged with

a high performance cool centrifuge

According to the General Procedure D, 19d (300 mg, 0.6 mmol)

was treated with XtalFluor-E^Ò(220 mg, 0.8 mmol) and triethyl-

amine trihydroﬂuoride (0.26 mL, 1.6 mmol) in CH₂Cl₂(30 mL) at

À78 °C. The product was puriﬁed by fc (d = 5 cm, l = 8 cm, cyclohex-

ane/ethyl acetate 25:75, R_f0.66 (cyclohexane/ethyl acetate 30:70)).

Colorless solid, mp 177–178 °C, yield 208 mg (69%). C₂₈H₂₇FN₄O₂

(470.5 g/mol). Exact mass (APCI): m/z = calcd for C₂₈H₂₈FN₄O₂Na

494.2088 found 494.2080. Purity (HPLC): 99.7% (t_R= 21.89 min).

¹H NMR (DMSO-d₆): d (ppm) = 2.11–2.19 (m, 4H, NCH₂CH₂CH₂F,

CH₂CH₂CH₂CONH), 2.37 (s, 3H, CH₃), 3.42 (t, J = 5.6 Hz, 2H, CH₂CH_2-

CH₂CONH), 4.38 (dt, J = 42.5/5.7 Hz, 2H, NCH₂CH₂CH₂F), 4.68 (t,

J = 6.2 Hz, 2H, NCH₂CH₂CH₂F), 7.18 (t, J = 7.4 Hz, 1H, 6-H_carb), 7.45

(t, J = 7.6 Hz, 1H, 7-H_carb), 7.47–7.52 (m, 2H, 3-H_phenyl, 5-H_phenyl),

7.56 (d, J = 8.5 Hz, 1H, 8-H_carb), 7.60–7.64 (m, 2H, 1-H_carb, 2-H_carb),

7.97–8.05 (m, 3H, 5-H_carb, 2-H_phenyl, 6-H_phenyl), 8.39 (s, 1H, 4-H_carb),

9.97 (s, 1H, CONH). The signal for CH₂CH₂CH₂CONH is overlaid by

the solvent peak, but can be seen in CDCl₃. ¹³C NMR (DMSO-d₆): d

(ppm) = 21.9 (1C, CH₃), 22.0 (1C, CH₂CH₂CH₂CONH), 25.4 (1C, CH_2-

CH₂CH₂CONH), 29.4 (d, J = 19.6 Hz, 1C, NCH₂CH₂CH₂F), 35.0 (1C,

CH₂CH₂CH₂CONH), 42.9 (d, J = 5.0 Hz, 1C, NCH₂CH₂CH₂F), 81.4 (d,

J = 162.1 Hz, 1C, NCH₂CH₂CH₂F), 108.9 (1C, C-8_carb), 109.2 (1C, C-

(20,000Âg, 4 °C). The supernatant was discarded and the pellet

resuspended in a deﬁned volume of TRIS buffer (50 mM TRIS,

12 mM MgCl₂, 4 mM EDTA, pH 7.4) yielding cell fragments of

approximately 2,000,000 cells/mL. The suspension of membrane

homogenates was sonicated again (4 °C, 2 Â 10 s cycles with

breaks of 10 s) and stored at À80 °C.

7.3. General protocol for the binding assays

The test compound solutions were prepared by dissolving

approximately 10 lmol (usually 2–4 mg) of test compound in

DMSO so that a 10 mM stock solution was obtained. To obtain

the required test solutions for the assay, the DMSO stock solution

was diluted with the respective assay buffer. The ﬁltermats were

presoaked in 0.5% aqueous polyethylenimine solution for 2 h at

room temperature before use. All binding experiments were car-

ried out in duplicates in 96-well multiplates. The concentrations

given are the ﬁnal concentrations in the assay. Generally, the as-

says were performed by addition of 50

buffer, 50 L test compound solution in various concentrations

(10-5, 10-6, 10-7, 10-8, 10-9 and 10-10 mol/L), 50 of

lL of the respective assay

l

L

1_carb), 111.3 (1C, C-4_carb), 118.7 (1C, C-2_carb), 119.1 (1C, C-6_carb),

C. Lueg et al. / Bioorg. Med. Chem. 21 (2013) 7481–7498

7497

corresponding radioligand solution and 50

receptor preparation into each well of the multiplate (total

volume 200 L). The receptor preparation was always added last.

During the incubation, the multiplates were shaken at a speed of

500–600 rpm at the speciﬁed temperature. Unless otherwise

noted, the assays were terminated after 120 min by rapid

ﬁltration using the harvester. During the ﬁltration each well

lL of the respective

References and notes

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was washed ﬁve times with 300 lL of water. Subsequently, the

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a

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Acknowledgement

We are very grateful to Prof. Dr. Paul Prather, Institute of phar-

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ported by the Deutsche Forschungsgemeinschaft, which is gratefully

acknowledged.

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Article Doi

Development of fluorinated CB2 receptor agonists for PET studies

DOI: 10.1016/j.bmc.2013.09.040

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