**2.1.1 Bicyclic quinolones**

#### *Position 1*

The studies on quinolones indicated that in order for the compound to have antibacterial activity, the N-1 position requires a substituent. Many quinolones contain in N-position : ethyl (norfloxacin, pefloxacin, lomefloxacin) , fluoroethyl (fleroxacin), vinyl, clloroethyl, trifluoroethyl, aminoethyl,, cyclopropyl (ciprofloxacin), *t*-butyl, bicyclopentyl,*p*fluorophenyl,2,4-difluorophenyl (Scott 1997)

#### *Position 2*

Quinolones contain at C-2 hydrogen (R2=H). The replacement at hydrogen has generally proven to be disadvantageous. However, some compounds containing a suitable C-1, C-2 ringhave recently been shown to possess biological activity. (Figure7 -Segawa 1992) (Figure 8 – Scott 1997)

Quinolones: Synthesis and Antibacterial Activity 261

The nature of the C-6 substituent have a great impact on the DNA-gyrase inhibitory activity and cell penetration. (Domagala et al. 1986). The R6 can be H, Cl, F, NO2, NH2, CN,

The choice of the C-7 substituent is a key issue which continues to guide the design of new antibacterial quinolones. The R7 can be substituted/unsubstituted piperazines, aminopyrrolidines, aminoalkylpyrrolidines, (Figure 5) (Chu & Fernandes 1991) (Scott 1997).

The most common variations at the C-8 position is hydrogen atom (X= CH) or a nitrogen atom(a naphthyridine) (X=N). However, compact, liophilic group (X = CF,C-CF3,, CCl, C-

The quinolones are of synthetic origin. (Chu & Fernandes, 1991). The most common synthetic methodology to prepare quinolone derivatives is Gould-Jacobs method (Figure 11). This method is used mainly for synthesis of compounds with N-1 alkyl substituents, and consists in the condensation of anilines (II) with diethyl ethoxymethylenemalonate (EMME) and cyclization of the obtained anilinomethylenemalonate**.** Termal cyclization can be carried out in dowterm (Koga, et al.1980), clorsulfonic acid, oleum acid or a mixture of clorosulfonic acid and oleum acid (Saukaita & Gupton, 1996). The key intermediary obtained (IV or X) will undergo a alkylation (Koga et al. 1980), cycloalkylation with bromocyclopropane (Kazimierozaack & Pyznar, 1987), (Sanjose&Ulpiano 1986), or with 1-bromo-1-ethoxy-cyclopropane, arylation with *para-*nitro-clorofenil or 2,4-dinitro-clorofenil (Raddl & Zikan, 1989) in order to insert the substituent in position 1 ofthe quinolone nucleus. The ethyl esther (V) undergoes a hydrolysis reaction, and the quinoline-3-carboxylic acid(VI), following regiospecific substitution of the 7-chloro group leads to the final compounds (VIII). Figure 11 illustrates also, methods for synthesis of 1-cyclopropyl-quinolones starting to anilines of formula II.Anilines (II) is reacted with 1-bromo-1-ethoxy-cyclopropane (Ramos & Garcia 1994)(Scriewer et al. 1988) or a cyclopropyl-metalic compound (McGuirk 1989). Alternatively, N-ethyl substituted anilines of formula XV may be formed by reductive amination with an appropiate aldehyde and a suitable reducing agent: diborane, palladium on carbon with hydrogen, sodium borohydride or sodium cyanoborohidride (McGuirk 1989) (Ramos 1994). N-isopropyl substituted quinolones may be form by alkylation with isopropylbromide (Pintilie et al. Sept. 2009), (Pintilie et al, oct.2009),(Pintilie et al. 2010), of

The modified Gould-Jacobs method will also be used, where the diethyl ethoxymethylenemalonate reacts with monosubstituted N aniline (XVII) (Figure 12). The aniline (XVII) is obtained by reductive amination of ketones and aldehydes with sodium borohydride-acetic acid (Itoh & Kato 1984) or triacetoxyborohydride. (Pintilie et al.2009).

OCH3) increase the antibacterial activity. (Chu & Fernandes 1991) (Scott 1997).

*Position 6* 

*Position 7* 

*Position 8* 

**2.2 Method of synthesis** 

compounds IV. (Figure 11).

(Pintilie et al. 2010).

*Gould-Jacobs method* 

CH3SCH3, COCH3 ) (Koga et al. 1980)

R = H, methyl, ethyl, substituted phenyl

R6= F, Cl

R7= heterocycle

Fig. 8. 7-Substituted-6-halo-4-oxo-4H-[1,3]-thiazeto[3,2]quinolin-3-carboxilyc acid.

#### *Position 3*

The C-3 carboxylic acid moiety is most commonly encountered. (Chu &Fernandes1991) . In the late of 1980s, a modification was described that eliminated the need for C-3 carboxylic acid. A fused izothiazolone ring was identified as serving as a carboxylic acid mimic,The compound A-62824 (Figure 9) have been found with biological activity.

Fig. 9. Quinolones with sulfur substituent at C-2.

Fig. 10. A-62824.

*Position 4* 

The C-4 oxo group of the quinolones nucleus is generally considered to be essential for antibacterial activity.

#### *Position 5*

The choice of the C-5 substituent appears to be dictated by the the steric regulations and the nature of the N-1 and C-8 substituent (Chu &Fernandes1991). (R5 = methyl, halogen, amino when X = CF).

#### *Position 6*

260 Antimicrobial Agents

O

R

S

CO2H

R6

R = H, methyl, ethyl, substituted phenyl

R6= F, Cl

*Position 3* 

F

Fig. 10. A-62824.

antibacterial activity.

*Position 4* 

*Position 5* 

when X = CF).

N N

HN

O

CO2H

Fig. 9. Quinolones with sulfur substituent at C-2.

S

R7= heterocycle

R7 <sup>N</sup>

Fig. 8. 7-Substituted-6-halo-4-oxo-4H-[1,3]-thiazeto[3,2]quinolin-3-carboxilyc acid.

F

HN

F

HN

N N

The C-4 oxo group of the quinolones nucleus is generally considered to be essential for

The choice of the C-5 substituent appears to be dictated by the the steric regulations and the nature of the N-1 and C-8 substituent (Chu &Fernandes1991). (R5 = methyl, halogen, amino

compound A-62824 (Figure 9) have been found with biological activity.

The C-3 carboxylic acid moiety is most commonly encountered. (Chu &Fernandes1991) . In the late of 1980s, a modification was described that eliminated the need for C-3 carboxylic acid. A fused izothiazolone ring was identified as serving as a carboxylic acid mimic,The

N N

O

O

CO2H

F

HN O

N N

O

CO2H

S

S

S NH

O

The nature of the C-6 substituent have a great impact on the DNA-gyrase inhibitory activity and cell penetration. (Domagala et al. 1986). The R6 can be H, Cl, F, NO2, NH2, CN, CH3SCH3, COCH3 ) (Koga et al. 1980)

#### *Position 7*

The choice of the C-7 substituent is a key issue which continues to guide the design of new antibacterial quinolones. The R7 can be substituted/unsubstituted piperazines, aminopyrrolidines, aminoalkylpyrrolidines, (Figure 5) (Chu & Fernandes 1991) (Scott 1997).

#### *Position 8*

The most common variations at the C-8 position is hydrogen atom (X= CH) or a nitrogen atom(a naphthyridine) (X=N). However, compact, liophilic group (X = CF,C-CF3,, CCl, C-OCH3) increase the antibacterial activity. (Chu & Fernandes 1991) (Scott 1997).

#### **2.2 Method of synthesis**

#### *Gould-Jacobs method*

The quinolones are of synthetic origin. (Chu & Fernandes, 1991). The most common synthetic methodology to prepare quinolone derivatives is Gould-Jacobs method (Figure 11). This method is used mainly for synthesis of compounds with N-1 alkyl substituents, and consists in the condensation of anilines (II) with diethyl ethoxymethylenemalonate (EMME) and cyclization of the obtained anilinomethylenemalonate**.** Termal cyclization can be carried out in dowterm (Koga, et al.1980), clorsulfonic acid, oleum acid or a mixture of clorosulfonic acid and oleum acid (Saukaita & Gupton, 1996). The key intermediary obtained (IV or X) will undergo a alkylation (Koga et al. 1980), cycloalkylation with bromocyclopropane (Kazimierozaack & Pyznar, 1987), (Sanjose&Ulpiano 1986), or with 1-bromo-1-ethoxy-cyclopropane, arylation with *para-*nitro-clorofenil or 2,4-dinitro-clorofenil (Raddl & Zikan, 1989) in order to insert the substituent in position 1 ofthe quinolone nucleus. The ethyl esther (V) undergoes a hydrolysis reaction, and the quinoline-3-carboxylic acid(VI), following regiospecific substitution of the 7-chloro group leads to the final compounds (VIII). Figure 11 illustrates also, methods for synthesis of 1-cyclopropyl-quinolones starting to anilines of formula II.Anilines (II) is reacted with 1-bromo-1-ethoxy-cyclopropane (Ramos & Garcia 1994)(Scriewer et al. 1988) or a cyclopropyl-metalic compound (McGuirk 1989). Alternatively, N-ethyl substituted anilines of formula XV may be formed by reductive amination with an appropiate aldehyde and a suitable reducing agent: diborane, palladium on carbon with hydrogen, sodium borohydride or sodium cyanoborohidride (McGuirk 1989) (Ramos 1994). N-isopropyl substituted quinolones may be form by alkylation with isopropylbromide (Pintilie et al. Sept. 2009), (Pintilie et al, oct.2009),(Pintilie et al. 2010), of compounds IV. (Figure 11).

The modified Gould-Jacobs method will also be used, where the diethyl ethoxymethylenemalonate reacts with monosubstituted N aniline (XVII) (Figure 12). The aniline (XVII) is obtained by reductive amination of ketones and aldehydes with sodium borohydride-acetic acid (Itoh & Kato 1984) or triacetoxyborohydride. (Pintilie et al.2009). (Pintilie et al. 2010).

Quinolones: Synthesis and Antibacterial Activity 263

N

F X

R1NH2 R2R3CO

N

R1

N

R1

Fig. 13. Method requiers the reaction of isatoic anhydride with sodium ethyl formyl acetate

An efficient and regiospecific synthesis via an intramolecular nucleophilic displacement

• reaction of benzoic acid chloride (I) with ethyl malonic acid; the compound (II) give

• acetophenone (Ia) is condensed with diethyl carbonate in the presence of sodium

VII

the compund (III).(Petersen & Grohe 1984a), (Petersen & Grohe 1984b),

O

O

PPA NaOH

F

CO2H I

HOCH=CHCO2Et

R7H

Key compund (III) can be obtained by:

hydride(Chu et al. 1985)

F

F

F R7

*Intramolecular nucleophilic displacement cyclization route to quinolones (a)* 

cyclization reaction was reported. (Chu,1985) (Figure 14).

F

NH2

NaBH4 NaCO2CH3 CH3COCH3

F

F F

Fig. 12. The modified Gould-Jacobs method.

F X O

F

CH3CO2H EMME

F F

CO2Et

XIX VIa

CO2H NH

R1

XX XXI XXIII

CO2Et

CO2H

X N

V VI

IIa XVII XVIII

N

F

F

F X

F X

F F

<sup>F</sup> CO2Et

F

NH <sup>N</sup>

O

CO2H

O N

O

CO2H

O

R1

O

R1

CO2Et

Fig. 11. Gould-Jacobs method.

*Method requiers the reaction of isatoic anhydride with sodium ethyl formyl acetate* 

Another synthesis method requiers the reaction of isatoic anhydride with sodio ethyl formyl acetate (Figure 13). 2,4,5-trihalobenzoic acid (XX) is reacted with an appropiate amine, and then is treated with the compound :R2R3CO (R2 = R3 = Cl, CCl3O or R2= C1-10alkyl and R3 = Cl) to produce benzoxazindione (XXII). The benzoxazindione (XXII) is then condensed with compound (HOCH=CHCO2Et) to provide key compound (V).

F

X

R8

N H

F

X

2

I I

> E MM E

> > N H

I I I

F

X

R1Y

R8

D E S N a O H H C l

C O

2E t

> C O

2E t

N

I V

> B r

> > O E t

R8

F

X

N

R1

V

R8

O

C O

2E t

R8

V I I I

r e d .

F

X

Δ

O H

> C O

2E t

N

O E t

O

C O

2E t

F

N

N H N NC H

3

I a

F

R7

R7

=

R7

F

R7

F

R7

F

R7

N H

N

N

R1

N

R1

Fig. 11. Gould-Jacobs method.

V I I

R8

O


X I

O

R1H a l

X

O H

1.E M M E

I X

> 2.Δ

N O

r e d . 2

R7H

X = C l

R8

=

H

F

X

R8

X I I

R8

X I I I

> 1.E MM E

R8 X I V

F

X

compound (HOCH=CHCO2Et) to provide key compound (V).

N H

N

1.P P A

2.A c O HH

2S O

4

C O

2E t

> C O

2E t

F

X

C H

N a O H

2 C O C l C O

2e T

N

R1

R8

V I

*Method requiers the reaction of isatoic anhydride with sodium ethyl formyl acetate* 

O

C O

2H

Another synthesis method requiers the reaction of isatoic anhydride with sodio ethyl formyl acetate (Figure 13). 2,4,5-trihalobenzoic acid (XX) is reacted with an appropiate amine, and then is treated with the compound :R2R3CO (R2 = R3 = Cl, CCl3O or R2= C1-10alkyl and R3 = Cl) to produce benzoxazindione (XXII). The benzoxazindione (XXII) is then condensed with

R8

X V I

> -O H

F

X

F

X

R8

N H

O E t

N O

2

I

B r

H2

/N i R y

O E t

> Me t a l

> > F

X

R8

N

O

2H

H

E t

X V

> H C O

P h Me

1.A c

2.B H

A c O H

2O

2

3. S Me

> N H

E t

2

C O

C O

> C O

2H

R7H

2E t F

X

2E t

Fig. 12. The modified Gould-Jacobs method.

Fig. 13. Method requiers the reaction of isatoic anhydride with sodium ethyl formyl acetate

#### *Intramolecular nucleophilic displacement cyclization route to quinolones (a)*

An efficient and regiospecific synthesis via an intramolecular nucleophilic displacement cyclization reaction was reported. (Chu,1985) (Figure 14).

Key compund (III) can be obtained by:


Quinolones: Synthesis and Antibacterial Activity 265

A synthesis method similar to that described above is shown in Figure 15. This method

**F <sup>F</sup> CH3**

**III**

**CO 2Et CO2Et** **NO <sup>2</sup>**

**NO2**

**CO 2Et**

**NO <sup>2</sup> NH VIII**

**O**

 **IX**

**F**

**N**

**XV**

**O**

**R7H R7H**

**CO 2H**

**F**

**F R7**

**N**

**F CO 2H**

**XII**

**Cl**

Fig. 15. Intramolecular nucleophilic displacement cyclization route to quinolones (b)*.* 

This paper presents experimental data regarding the synthesis of several quinolones with

**O**

**NO <sup>2</sup>**

**CO 2H**

**O**

**CO2Et**

**N**

**N**

**N**

**F CO 2H**

**XIV**

**O**

**F CO 2Et**

**XIII**

**O**

**O F CO 2Et**

**NO2 NO <sup>2</sup> IV**

**NO <sup>2</sup> NO <sup>2</sup>**

 **VII a**

*Intramolecular nucleophilic displacement cyclization route to quinolones (b)* 

**CH3**

**I II**

**COCl**

**O H**

**NO <sup>2</sup> NO <sup>2</sup>**

 **VII b**

**NO2 NO <sup>2</sup> V**

**F**

 **XI**

**2.3 Structure of the new compounds** 

general formula: (Figure 16)

**N**

**O**

**X**

**F NH2**

> **F Cl**

**N**

**O**

**CO2Et**

**CO 2Et**

involves intramolecular cyclization of the compound (VIII).(Egawa et al. 1987).

**+**

**O**

**F**

**H2/ Pd - C**

**CH3**

**F F F**

**NO <sup>2</sup> NO <sup>2</sup>**

**<sup>F</sup> <sup>F</sup> <sup>F</sup>**

**CO2Et**

**VI** 

 **NO <sup>2</sup> NO <sup>2</sup>**

Fig. 14. Intramolecular nucleophilic displacement cyclization route to quinolones (a).

Intermediates (III) reacts with acetic anhydride in the presence trietilortoformiate to produce 3-ethoxy-2-benzoyl-ethyl acrylate (IV). Compound (IV) is further reacted with an appropriate amine in dichloromethane at room temperature to provide 3-anilino-2-benzoylethyl acrylate (IVa).

Compound (IVa) can be also obtained directly from benzoic acid chloride (I). (Chu & Fernandes 1991).

Treatment with a base induces cyclization to produce the quinolone (V).

CH2 CO2Et CO2Et

MgOEt

(C2H5O)2CO NaH

COCl

Cl

C

O

CH3

Cl

O

F

NH OEt O

R1

R5

R8

I

R5

R8

R5

Ia

R8

N

R1

Treatment with a base induces cyclization to produce the quinolone (V).

O

NaH hydrolysis

F

ethyl acrylate (IVa).

Fernandes 1991).

CO2H

Fig. 14. Intramolecular nucleophilic displacement cyclization route to quinolones (a).

Intermediates (III) reacts with acetic anhydride in the presence trietilortoformiate to produce 3-ethoxy-2-benzoyl-ethyl acrylate (IV). Compound (IV) is further reacted with an appropriate amine in dichloromethane at room temperature to provide 3-anilino-2-benzoyl-

Compound (IVa) can be also obtained directly from benzoic acid chloride (I). (Chu &

CO2Et

NH R1

<sup>X</sup> <sup>N</sup>

R7H

IV IVa

VI VII

CO2H

O

C

O

CH

II

CO2Et CO2Et

R5

R8

acid

R5

R8

R5

R8

F

X

F

X

F

X

Cl OEt

R1NH2

Cl

*para* toluene sulfonic

C

O

CH2

CO2Et

CO2Et

Cl

III

Cl

O

(C2H5O)3CH

F

R7

R1

X

F

X

F

X

*Intramolecular nucleophilic displacement cyclization route to quinolones (b)* 

A synthesis method similar to that described above is shown in Figure 15. This method involves intramolecular cyclization of the compound (VIII).(Egawa et al. 1987).

Fig. 15. Intramolecular nucleophilic displacement cyclization route to quinolones (b)*.* 

#### **2.3 Structure of the new compounds**

This paper presents experimental data regarding the synthesis of several quinolones with general formula: (Figure 16)

Quinolones: Synthesis and Antibacterial Activity 267

halide to produce the qinolone 3-carboxylate ester (6). (R1 = ethyl, alyl, benzyl, *p*-nitrophenyl)

A modified approach resorts to the use of a monosubstitued aniline (4) as a starting material which avoids subsequent N-1-amine alkylation (R1 = isopropyl, 2-butyl, 2-pentyl). (Pintilie et al. 2009a) (Pintilie et al. 2009b),(Pintilie et al. 2010). A strong acid (such as polyphosphoric acid) is often needed to induce cyclization directly resulting in the formation of N-isopropyl-4-oxo-quinolone-3-carboxylate ester (6) (R1 = isopropyl, 2-butyl, 2-pentyl). In either case, the final manipulation is acid or basic hydrolysis to cleave the ester generating the biologically active free carboxylic acid (7). The biologically active free carboxylic acid (7) was also obtained from the corresponding 4-hidroxy-quinoline-3-carboxylate ester (3) by alkylation with dialkyl sulphates in presence of alkali, for example the reaction it can conveniently be carried out in aqueous 40 % sodium hydroxide solution. The displacement of 7-chloro group

The synthesis of new 1-aryl quinoline-3-carboxilyc acids is according Figure 18. compound (3) (R6=F,Cl,CH3) is direct N-arylation. Treatment of (3) with potasium carbonate in DMSO and *p*-fluoro-nitrobenzene yielded 9). The esters were hydrolized to the appropiate acids (10) by refluxing with a mixture of hydrochloric and acetic acids. Upon treatment with a heterocycle yielded compounds (11). The 1-(*p*-amino-phenyl)-quinoline-3-carboxylic acids

N

DMF N

Cl

N

NH2

R6

R7

O R6 CO2H

O R6 CO2H

NO2

N

R1

OCH3

O

CO2H

NO2

R7

O R6 CO2C2H5

(12) can be prepared by a common reduction of nitro group using sodium dithionite.

Cl

3 <sup>9</sup> <sup>10</sup>

<sup>11</sup> <sup>12</sup>

acids (14) was prepared allowing compound (13) to act with alkali metalic alcholate.

Cl

The sinthesys of the new 8-substituted quinoline-3-carboxylic acids is according Figure 19. 8-Chloro-quinoline-3-carboxylic acids (13) was synthesized from 8-unsubstituted qinoline-3 carboxilyc acids by chlorination with sulfuryl chloride. 8-Methoxy-quinoline-3-carboxilyc

N

SO2Cl2 CH3ONa

<sup>8</sup> <sup>13</sup> <sup>14</sup>

R1

O

CO2H

(Pintilie et al. 2003a) (Pintilie et al. 2003b),(Pintilie et al. 2003c)(Pintilie & Nita 2011).

with a heterocycle yielded compounds (8).

N

R7H

Fig. 18. Sinthesys of 1-aryl-quinolones.

N

R1

O

CO2H

R6

R7

OH

CO2C2H5 <sup>F</sup> NO2

K2CO3

N

NO2

R6

R7

Fig. 19. Sinthesys of the new 8-substituted quinoline-3-carboxylic acids.

R7

O R6 CO2H

R6

Cl

Fig. 16. The structure of the new compounds.

R1 = ethyl, isopropyl, 2-buthyl, 2-penthyl, benzyl, alyl, *p*-nitro-phenyl, *p*-amino-phenyl; R6 = hydrogen, fluor, chlor, methyl; R7 = 3-methyl-piperazinyl, 4-methyl-piperazinyl, piperidinyl, 3-methyl-piperidinyl, 4-methyl-piperidinyl, pirolidinyl, morpholinyl, homopiperazinyl;

R8 = hydrogen,chlor, methyl. methoxy, nitro

#### **2.4 Synthesis pathway**

The synthesis of the novel quinolones followed a Gould-Jacobs cyclization process (Figure 17). An appropriate unsubstituted aniline (1) is reacted with diethylethoxy methylene malonate (EMME) to produce the resultant anilinomethylenemalonate (2). A subsequent thermal process induces Gould-Jacobs cyclization to afford the corresponding 4-hidroxyquinoline-3-carboxylate ester (3). (R6 = fluoro, chloro, methyl, hydrogen) (Pintilie et al. 2009a) (Pintilie et al. 2009b),(Pintilie et al. 2010).

Fig. 17. Synthesis of the new quinolones.

The following operation is the alkylation of the 4-hidroxy-quinoline-3-carboxylate ester (3). which is usually accomplished by reaction with a suitable alkyl halide, dialkyl sulphates, aril

O

CO2H

**6**

**R6 Cl**

**R8 R1**

**N**

**O**

**CO2C2H5**

**NaOH AcOH**

**N**

**R1**

**R8**

**O**

**CO2H**

**R6 Cl** **- aq.**

**DES/Rhal K2CO3 DMF**

**DES / NaOH HCl 1. 2.**

**8 7**

**heterocycle**

**N**

**R1**

**R8**

**O**

**PPA**

**90-1000C**

**R6 CO2H**

**N**

**Cl R8**

**OH CO2C2H5 R6**

**R7**

The following operation is the alkylation of the 4-hidroxy-quinoline-3-carboxylate ester (3). which is usually accomplished by reaction with a suitable alkyl halide, dialkyl sulphates, aril

R6

R7

4-methyl-piperidinyl, pirolidinyl, morpholinyl, homopiperazinyl;

Fig. 16. The structure of the new compounds.

R8 = hydrogen,chlor, methyl. methoxy, nitro

2009a) (Pintilie et al. 2009b),(Pintilie et al. 2010).

**EMME R6**

**1300 C 1,5 h**

**Cl**

**1 2 3**

**R6 Cl** **CO2C2H5**

**CO2C2H5 Dowterm**

**2500C 45 min.**

**CO2C2H5 CO2C2H5**

**N R1**

**R8**

**R8 NH**

**<sup>4</sup> <sup>5</sup>**

Fig. 17. Synthesis of the new quinolones.

**EMME**

**1450C 1,5 h**

R6 = hydrogen, fluor, chlor, methyl;

**2.4 Synthesis pathway** 

**R6**

**Cl NH2 R8**

> **R6 Cl**

**R8 NH R1**

N

R8 R1

R1 = ethyl, isopropyl, 2-buthyl, 2-penthyl, benzyl, alyl, *p*-nitro-phenyl, *p*-amino-phenyl;

R7 = 3-methyl-piperazinyl, 4-methyl-piperazinyl, piperidinyl, 3-methyl-piperidinyl,

The synthesis of the novel quinolones followed a Gould-Jacobs cyclization process (Figure 17). An appropriate unsubstituted aniline (1) is reacted with diethylethoxy methylene malonate (EMME) to produce the resultant anilinomethylenemalonate (2). A subsequent thermal process induces Gould-Jacobs cyclization to afford the corresponding 4-hidroxyquinoline-3-carboxylate ester (3). (R6 = fluoro, chloro, methyl, hydrogen) (Pintilie et al. halide to produce the qinolone 3-carboxylate ester (6). (R1 = ethyl, alyl, benzyl, *p*-nitrophenyl) (Pintilie et al. 2003a) (Pintilie et al. 2003b),(Pintilie et al. 2003c)(Pintilie & Nita 2011).

A modified approach resorts to the use of a monosubstitued aniline (4) as a starting material which avoids subsequent N-1-amine alkylation (R1 = isopropyl, 2-butyl, 2-pentyl). (Pintilie et al. 2009a) (Pintilie et al. 2009b),(Pintilie et al. 2010). A strong acid (such as polyphosphoric acid) is often needed to induce cyclization directly resulting in the formation of N-isopropyl-4-oxo-quinolone-3-carboxylate ester (6) (R1 = isopropyl, 2-butyl, 2-pentyl). In either case, the final manipulation is acid or basic hydrolysis to cleave the ester generating the biologically active free carboxylic acid (7). The biologically active free carboxylic acid (7) was also obtained from the corresponding 4-hidroxy-quinoline-3-carboxylate ester (3) by alkylation with dialkyl sulphates in presence of alkali, for example the reaction it can conveniently be carried out in aqueous 40 % sodium hydroxide solution. The displacement of 7-chloro group with a heterocycle yielded compounds (8).

The synthesis of new 1-aryl quinoline-3-carboxilyc acids is according Figure 18. compound (3) (R6=F,Cl,CH3) is direct N-arylation. Treatment of (3) with potasium carbonate in DMSO and *p*-fluoro-nitrobenzene yielded 9). The esters were hydrolized to the appropiate acids (10) by refluxing with a mixture of hydrochloric and acetic acids. Upon treatment with a heterocycle yielded compounds (11). The 1-(*p*-amino-phenyl)-quinoline-3-carboxylic acids (12) can be prepared by a common reduction of nitro group using sodium dithionite.

Fig. 18. Sinthesys of 1-aryl-quinolones.

The sinthesys of the new 8-substituted quinoline-3-carboxylic acids is according Figure 19. 8-Chloro-quinoline-3-carboxylic acids (13) was synthesized from 8-unsubstituted qinoline-3 carboxilyc acids by chlorination with sulfuryl chloride. 8-Methoxy-quinoline-3-carboxilyc acids (14) was prepared allowing compound (13) to act with alkali metalic alcholate.

Fig. 19. Sinthesys of the new 8-substituted quinoline-3-carboxylic acids.

Quinolones: Synthesis and Antibacterial Activity 269

Quinolones R1 R6 R7 R8 m.p. (0C) Reference

ethyl F morpholin-1-yl Cl 244,6-244 Pintilie et

ethyl CH3 4-methyl-piperidin-1-yl H 240-242 Pintilie et

*iIso*-propyl CH3 4-methyl-piperidin-1-yl H 234-235 Pintilie et

benzyl CH3 4-methyl-piperidin-1-yl H 218-220 Pintilie et

alyl CH3 4-methyl-piperidin-1-yl H 244-246 Pintilie et

ethyl H 4-methyl-piperidin-1-yl H 240-242 Pintilie et

*iIso*-propyl H 4-methyl-piperidin-1-yl H 234-235 Pintilie et

benzyl H 4-methyl-piperidin-1-yl H 218-220 Pintilie et

alyl H 4-methyl-piperidin-1-yl H 244-246 Pintilie et

*iIso*-propyl H 4-methyl-piperazin-1-yl H 239-240 Pintilie et

ethyl H morpholin-1-yl H 267,3-269 Pintilie et

2-butyl H 4-methyl-piperidin-1-yl H 181,4-183 Pintilie et

phenyl F 4-methyl-piperidin-1-yl H 204-206 Pintilie&

phenyl F Homopiperazin-1-yl H 128-130 Pintilie&

phenyl Cl 4-methyl-piperidin-1-yl H 202-205 Pintilie&

phenyl CH3 4-methyl-piperidin-1-yl H 222-224 Pintilie&

phenyl F 4-methyl-piperidin-1-yl H 284-285,5 Pintilie&

phenyl CH3 4-methyl-piperidin-1-yl H 250-253 Pintilie&

Table 1. 4-Oxo- 1,4-dihydro-quinoline-3-carboxylic acids synthesized in this paper.

ethyl H 3-methyl-piperidin-1-yl H 190,1-

ethyl H 3-methyl-piperazin-1-yl H 191,3-

2-pentyl H 4-methyl-piperidin-1-yl H 138,5-

al. (2009b)

al. (2003a)

al. (2003a)

al. (2003a)

al. (2003a)

al. (2003c)

al. (2003c)

al. (2003c)

al. (2003c)

al. (2009a)

Pintilie et al. (2009a)

al. (2009a)

Pintilie et al. (2009a)

al. (2009a)

Pintilie et al. (2009a)

Nita (2011)

Nita (2011)

Nita (2011)

Nita (2011)

Nita (2011)

Nita (2011)

192,1

192,6

140,5

FPQ 28 C16H16ClFN2O4

> 6MeQ 83 C19H24N2O3

6MePQ 12 C20H26N2O3

6MePQ 11 C24H26N2O3

6MePQ 4 C20H24N2O3

HQ 83 C18H22FN2O3

HPQ 12 C19H24N2O3

HPQ 11 C23H24N2O3

HPQ 4 C19H22N2O3

HPQ 21 C18H23N3O3

HPQ 24 C18H22N2O3

HPQ 25 C16H18N2O4

HPQ 27 C17H21N3O3

HPQ 31 C19H24N2O3

HPQ 51 C19H24N2O3

PQ 3 C22H20FN3O5

PQ 7 C21H19FN4O5

6ClPQ 3 C22H20ClN3O5

6MePQ 3 C23H23N3O5

APQ 3 C22H22FN3O3

A6MePQ 3 C23H22N3O3

*p*-nitro-

*p*-nitro-

*p*-nitro-

*p*-nitro-

*p*-amino-

*p*-amino-

### **2.5 New compounds: Structure and antimicrobial activity**

#### **2.5.1 Structure of the new compunds**

A series of new 4-oxo-1,4-dihydro-quinoline-3-carboxylic acids was synthesized. (Figure 20) (Table 1).

Fig. 20. Structure of the new compounds.


A series of new 4-oxo-1,4-dihydro-quinoline-3-carboxylic acids was synthesized. (Figure 20)

N

R1

Quinolones R1 R6 R7 R8 m.p. (0C) Reference

R8

O

CO2H

ethyl F 4-methyl-piperidin-1-yl H 235-237 Pintilie et

ethyl F 4-methyl-piperidin-1-yl Cl 201-202,5 Pintilie et

ethyl F 4-methyl-piperidin-1-yl OCH3 <sup>170</sup>Pintilie et

*iIso*-propyl F 4-methyl-piperidin-1-yl H 253 Pintilie et

benzyl F 4-methyl-piperidin-1-yl H 240-242 Pintilie et

alyl F 4-methyl-piperidin-1-yl H 168-170 Pintilie et

ethyl F 3-methyl-piperidin-1-yl H 189,4 Pintilie et

*iIso*-propyl F 3-methyl-piperazin-1-yl H 215-218 Pintilie et

*iIso*-propyl F morpholin-1-yl H 266-268 Pintilie et

ethyl Cl 3-methyl-piperidin-1-yl H 216,4-

ethyl F morpholin-1-yl H 257,4-

ethyl Cl morpholin-1-yl H 267,1-

ethyl Cl 3-methyl-piperazin-1-yl H 170,5-

*iIso*-propyl F 3-methyl-piperidin-1-yl H 209,1-

al. (2003b)

al. (2003b)

al. (2003b)

al. (2003b)

al. (2003b)

al. (2003b)

al. (2009b)

Pintilie et al. (2009b)

Pintilie et al. (2009b)

al. (2009b)

al. (2009b)

Pintilie et al. (2009b)

Pintilie et al. (2009b)

Pintilie et al. (2009b)

218,4

211,7

258,7

269,2

171,4

**2.5 New compounds: Structure and antimicrobial activity** 

R6

R7

**2.5.1 Structure of the new compunds** 

Fig. 20. Structure of the new compounds.

(Table 1).

Q 83 C18H21FN2O3

Q 85 C18H20 Cl FN2O3

PQ 1 C19H23FN2O4

PQ 12 C19H23FN2O3

PQ 11 C23H23FN2O3

PQ 4 C19H21FN2O3

FPQ 24 C18H21FN2O3

6ClPQ 24 C18H21ClN2O3

PQ 24 C19H23FN2O3

PQ 22 C18H21FN3O3

PQ 23 C17H19FN2O4

FPQ 25 C16H17FN2O4

6ClPQ 25 C16H17ClN2O4

6ClPQ 27 C17H20FN3O3


Table 1. 4-Oxo- 1,4-dihydro-quinoline-3-carboxylic acids synthesized in this paper.

Quinolones: Synthesis and Antibacterial Activity 271

**<sup>4</sup> <sup>5</sup>**

**<sup>18</sup> <sup>17</sup> <sup>16</sup>**

Fig. 21. 1-Ethyl-6-fluoro-7-morpholinyl-8-chloro-1,4-dihydro-4-oxo-quinoline-3-carboxylic

1H-NMR(dmso-d6, δ ppm, *J* Hz): 8.97(s, 1H, H-2); 8.07(d, 1H, H-5, 11.8); 4.89(q, 2H, H-17, 7.2); 3.82(m, 4H, sist. A2B2, H-13-15); 3.37(m, 4H, sist. A2B2, H-12-16); 1.46(t, 3H, H-18, 7.2). 13C-NMR(dmso-d6, δ ppm, *J* Hz): 175.56(C-4); 166.12(C-21); 154.95(d, *J*(13C-19F)=254.8, C-6);158.37(Cq); 153.04(C-2); 125.94(Cq); 124.76(Cq); 116.86(Cq); 111.57(d, *J*(13C-19F)=23.5, C-5);

FT-IR(solid in ATR, ν cm-1): 3056; 2957; 2895; 2849; 1717; 1615; 1558; 1532; 1492; 1435; 1376;

Brighty, K & Gootz, T. (2000) Chemistry and Mechanism of action of the quinolone

Chu, D.T.W., Fernandes P., Claiborne, A.K., Pihuleac, E., Norden, C.W., Maleczka, J.R.E. &

Chu, D.T.W. & Fernandes, P. (1991). Recent developments in the field of quinolone

Buiuc, D. (1998) Determinarea sensibilităţii la medicamente antimicrobiene: tehnici

Egawa, H., Kataoka, M., Shibamori K., Miyamoto, J.N. & Matsumoto, J. (1987) A new

*Journal of Heterocyclic Chemistry,* Vol.24, (1987), pp 181-185, ISSN -0022-152X

Koga, H., Itoh, A. & Murayama, S.,(1980) Structure-activity relationships of antibacterial 6,7-

Academic Press, ISBN 0-12-013321-0, London ; San Diego ; New York Domagala, J.M., Heifetz, C.L., Mich, T.F. & Nichols, J.B., (1986) 1-Ethyl-7-[3- [(ethylamino)methyl]-1-pyrrolidinyl]-6,8-difluoro-1,4-dihydro-4-oxo-3-quinoline carboxylic acid. New quinolone antibacterial with potent gram-positive activity. *Journal of Medicinal Chemistry,* Vol. 29, No. 4, (apr. 1986), pp. 445-448, ISSN-0022-

antibacterial, In: *The Quinolones Third Edition*, Vincent Andriole, pp. 33-97,

Pernet, A.G. (1985). Synthesis and structure-activity relationships of novel arylfluoroquinolone antibacterial agents. *Journal of Medicinal Chemistry,* Vol. 28,

antibacterial agents, In : *Advances in drug research Vol. 21,* Bernard Testa, pp. 39-144,

cantitative, în "Microbiologie clinică", vol. I, 1998, pp. 438-442. Editura Didactică şi

synthetic route to 7-halo-1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxoquinoline-3 carboxylic acid, an intermediate for the synthesis of quinolone antibacterial agents.

and 7,8-disubstituted 1-alkyl-1,4-dihydro-4-oxoquinoline-3-carboxylic acids. *Journal of Medicinal Chemistry,* Vol. 23, No.12, (dec. 1980), pp. 1358-1363, ISSN-0022-2623

N N

Cl

**6 7 8 9 10**

F

O

98.35(C-3); 67.23(C-13-15); 53.64(C-12-16); 51.58(C-17); 16.14(C-18).

Academic Press, ISBN 978-0-12-059517-4

1300; 1253; 1207; 1102; 1033; 980; 920; 890; 846; 803; 740; 651; 528; 464.

No.12, (dec. 1985), pp. 1558-1564, ISSN-0022-2623

Itoh, Y & Kato, H. (1984) Ger. Offen *Patent* DE 34 33 924 , 1984. Kazimierozaack, J. & Pyznar, B. (1987). PL *Patent* 154 525, 1987.

acid –FPQ 28

**4. References** 

2623

Pedagogică, Bucureşti.

**1 2 3**

CH2CH3

O

 **FPQ - 28**

**21**

COOH

#### **2.5.2 Antibacterial activity of the new compunds**

The new compounds were evaluated for "in vitro" activity by determining minimum inhibitory concentration against of bacteria *Escherichia. Coli, Staphylococcus. Aureus and Pseudomonas .aeruginosa,* by agar dilution method (Buiuc 1998) (NCCLS 2003). (Table 2).


*a. Escherichia. coli ATCC 25922, b. Staphylococcus. aureus ATCC29213, c. Staphylococcus. aureus ATCC29223, d. Pseudomonas .aeruginosa ATCC27813,e. Pseudomonas .aeruginosa ATCC27853* 

Table 2. "In vitro" antibacterial activity of the new quinolones.

#### **3. Conclusion**

In conclusion, were synthesized new quinolones and was investigated their antibacterial activity. The results indicate that substituent combinations in the quinolone ring, might produce powerful antibacterial agents such as compound: FPQ-28 (1-ethyl-6-fluoro-7 morpholinyl-8-chloro-1,4-dihydro-4-oxo-quinoline-3-carboxylic acid), (Figure 21) in concordance with the QSARs studies (Tarko et al. 2008), showed excellent "in vitro" activity against *E. Coli* ATCC 25922 (MIC 0,125 µg/mL) and *S.aureus ATCC29213 (*MIC 0,06 µg/mL).

Fig. 21. 1-Ethyl-6-fluoro-7-morpholinyl-8-chloro-1,4-dihydro-4-oxo-quinoline-3-carboxylic acid –FPQ 28

1H-NMR(dmso-d6, δ ppm, *J* Hz): 8.97(s, 1H, H-2); 8.07(d, 1H, H-5, 11.8); 4.89(q, 2H, H-17, 7.2); 3.82(m, 4H, sist. A2B2, H-13-15); 3.37(m, 4H, sist. A2B2, H-12-16); 1.46(t, 3H, H-18, 7.2). 13C-NMR(dmso-d6, δ ppm, *J* Hz): 175.56(C-4); 166.12(C-21); 154.95(d, *J*(13C-19F)=254.8, C-6);158.37(Cq); 153.04(C-2); 125.94(Cq); 124.76(Cq); 116.86(Cq); 111.57(d, *J*(13C-19F)=23.5, C-5); 98.35(C-3); 67.23(C-13-15); 53.64(C-12-16); 51.58(C-17); 16.14(C-18).

FT-IR(solid in ATR, ν cm-1): 3056; 2957; 2895; 2849; 1717; 1615; 1558; 1532; 1492; 1435; 1376; 1300; 1253; 1207; 1102; 1033; 980; 920; 890; 846; 803; 740; 651; 528; 464.

#### **4. References**

270 Antimicrobial Agents

The new compounds were evaluated for "in vitro" activity by determining minimum inhibitory concentration against of bacteria *Escherichia. Coli, Staphylococcus. Aureus and Pseudomonas .aeruginosa,* by agar dilution method (Buiuc 1998) (NCCLS 2003). (Table 2).

Q 83 3,12 (a) 1,56 (c) 6,25 (e) Pintilie et al. (2003b) Q 85 3,12 (a) 0,39 (c) 6,25 (e) Pintilie et al. (2003b) PQ 1 3,12 (a) 0,78 (c) 3,12 (e) Pintilie et al. (2003b) PQ 4 12,5 (a) 1,56 (c) 6,25 (e) Pintilie et al. (2003b) FPQ 24 2,00 (a) 0,50 (b) 32,00 (d) Pintilie et al. (2009b) 6ClPQ 24 8,00 (a) 2,00 (b) >128 (d) Pintilie et al. (2009b) PQ 24 8,00 (a) 2,00 (b) 64,00 (d) Pintilie et al. (2009b) PQ 22 0,50 (a) 4,00 (b) 8,00 (d) Pintilie et al. (2009b) 6ClPQ 25 4,00 (a) 2,00 (b) 128 (d) Pintilie et al. (2009b) FPQ 25 0,125 (a) 0,06 (b) 8,00 (d) Pintilie et al. (2009b) FPQ 28 0,125 (a) 0,06 (b) 8,00 (d) Pintilie et al. (2009b) HPQ 21 8,00 (a) 64,00 (b) >128 (d) Pintilie et al. (2009a) HPQ 25 8,00 (a) 64,00 (b) >128 (d) Pintilie et al. (2009a) HPQ 27 >128 (a) 32,00 (b) >128 (d) Pintilie et al. (2009a) PQ 3 12,50 (a) 25,00 (c) 12,50 (e) Pintilie& Nita (2011) APQ 3 12,50 (a) 0,78 (c) 12,50 (e) Pintilie& Nita (2011) PQ 7 12,50 (a) 3,12 (c) 12,50 (e) Pintilie& Nita (2011) *a. Escherichia. coli ATCC 25922, b. Staphylococcus. aureus ATCC29213, c. Staphylococcus. aureus ATCC29223,* 

µg/ml Referances

Minimum inhibitory concentration

*d. Pseudomonas .aeruginosa ATCC27813,e. Pseudomonas .aeruginosa ATCC27853*  Table 2. "In vitro" antibacterial activity of the new quinolones.

In conclusion, were synthesized new quinolones and was investigated their antibacterial activity. The results indicate that substituent combinations in the quinolone ring, might produce powerful antibacterial agents such as compound: FPQ-28 (1-ethyl-6-fluoro-7 morpholinyl-8-chloro-1,4-dihydro-4-oxo-quinoline-3-carboxylic acid), (Figure 21) in concordance with the QSARs studies (Tarko et al. 2008), showed excellent "in vitro" activity against *E. Coli* ATCC 25922 (MIC 0,125 µg/mL) and *S.aureus ATCC29213 (*MIC

E. coli S. aureus P. aeruginosa

**2.5.2 Antibacterial activity of the new compunds** 

Quinolone

**3. Conclusion** 

0,06 µg/mL).


Itoh, Y & Kato, H. (1984) Ger. Offen *Patent* DE 34 33 924 , 1984.


**13** 

*USA* 

**Superbugs:** 

**Current Trends and Emerging Therapies** 

Modern pharmaceutical advancements have placed us in an era where fatalities due to common communicable diseases such as pneumonia or plague are rare. It is difficult to imagine a time when antibiotics were not used as the "fix all" for common illnesses, and even used in cases where antibiotic treatment is not indicated. Although we generally take current treatments for granted, it is important to point out that historically speaking, available treatments for bacterial illnesses were not developed until nearly one-third of the way through the 20th century. It is the accidental discovery of penicillin in 1928 by Alexander Fleming that is considered perhaps one of the largest medical advancements of modern medicine (Bellis, n.d). Prior to the discovery and subsequent development of penicillin, epidemics and pandemics

Early records identify epidemics of plague in Egypt as early as 1650BC, although it is not clear whether it was plague or influenza (Austin, 2003; Daileader, 2007; Wade, 2010). The first major plague outbreak, which is now considered the beginning of the first plague pandemic, began in the Byzantine Empire around 541. The "Black Death" which affected Europe and Asia from 1338 to 1351 claiming 100,000,000 lives marks the beginning of the second plague pandemic and carries the largest death toll to date. The "Black Death" plague re-occurred in several smaller outbreaks including the 1665 "Great Plague of London" as well as outbreaks in France, Spain, and Vienna. The third plague pandemic began in 1873 in China and eventually spread to India, South Africa, North America, South America, and Australia. The death toll in Hong Kong and India from this pandemic breached 12,500,000

were more frequent, more prominent, and carried larger death tolls.

**Plague Pandemic Death Toll Location** 

**1st Pandemic (Byzantine Plague) c541-c639** ~25,000,000 Southern Europe **2nd Pandemic 1338-1665 (Black Death, 1338-1351)** >100,000,000\* N. Europe, Asia

**3rd Pandemic 1873-1957** >12,500,000 Europe, N. Asia, India,

Table 1. Comparison of death toll and location for historical plague pandemics (Austin, 2003; Daileader, 2007; Wade, 2010; Williams, 1997). \*Death toll from black death period only.

**1. Introduction** 

**1.1 An era before antibiotic treatments** 

before 1957 (Williams, 1997).

Amy L. Stockert and Tarek M. Mahfouz

China

*The Raabe College of Pharmacy, Ohio Northern University* 

