Structure-activity relationships of the quinolone antibacterials against mycobacteria: Effect of structural changes at N-1 and C-7

Article abstract of DOI:10.1021/jm9507082

The re-emergence of tuberculosis infections which are resistant to conventional drug therapy has demonstrated the need for alternative chemotherapy against Mycobacterium tuberculosis. As part of a study to optimize the quinolone antibacterials against M. tuberculosis, we have prepared a series of N-1- and C-7-substituted quinolones to examine specific structure-activity relationships between modifications of the quinolone at these two positions and activity against mycobacteria. The compounds, synthesized by literature procedures, were evaluated for activity against Mycobacterium fortuitum and Mycobacterium smegmatis as well as Gram-negative and Gram-positive bacteria. The activity of the compounds against M. fortuitum was used as a barometer of M. tuberculosis activity. The results demonstrate that (i) the activity against mycobacteria was related more to antibacterial activity than to changes in the lipophilicity of the compounds, (ii) the antimycobacterial activity imparted by the N-1 substituent was in the order tert-butyl ≥ cyclopropyl > 2,4-difluorophenyl > ethyl ? cyclobutyl > isopropyl, and (iii) substitution with either piperazine or pyrrolidine heterocycles at C-7 afforded similar activity against mycobacteria.

Full text of DOI:10.1021/jm9507082

J . Med. Chem. 1996, 39, 729-735
729
Str u ctu r e-Activity Rela tion sh ip s of th e Qu in olon e An tiba cter ia ls a ga in st
Mycoba cter ia : Effect of Str u ctu r a l Ch a n ges a t N-1 a n d C-7†
Thomas E. Renau,* J oseph P. Sanchez, J effrey W. Gage, J ulie A. Dever, Martin A. Shapiro,
Stephen J . Gracheck, and J ohn M. Domagala
Parke-Davis Pharmaceutical Research, Division of Warner-Lambert Company, Ann Arbor, Michigan 48105
Received September 26, 1995X
The re-emergence of tuberculosis infections which are resistant to conventional drug therapy
has demonstrated the need for alternative chemotherapy against Mycobacterium tuberculosis.
As part of a study to optimize the quinolone antibacterials against M. tuberculosis, we have
prepared a series of N-1- and C-7-substituted quinolones to examine specific structure-activity
relationships between modifications of the quinolone at these two positions and activity against
mycobacteria. The compounds, synthesized by literature procedures, were evaluated for activity
against Mycobacterium fortuitum and Mycobacterium smegmatis as well as Gram-negative and
Gram-positive bacteria. The activity of the compounds against M. fortuitum was used as a
barometer of M. tuberculosis activity. The results demonstrate that (i) the activity against
mycobacteria was related more to antibacterial activity than to changes in the lipophilicity of
the compounds, (ii) the antimycobacterial activity imparted by the N-1 substituent was in the
order tert-butyl g cyclopropyl > 2,4-difluorophenyl > ethyl ≈ cyclobutyl > isopropyl, and (iii)
substitution with either piperazine or pyrrolidine heterocycles at C-7 afforded similar activity
against mycobacteria.
In tr od u ction
The incidence of tuberculosis (TB) infection has
steadily risen in the last decade, and this increase can
be attributed to a similar increase in HIV infection.1 The
association of tuberculosis and HIV infection is so
dramatic that, in some cases, nearly two-thirds of the
patients diagnosed with TB are also HIV-1 seropositive.2
Furthermore, numerous studies have shown that TB is
a cofactor in the progression of HIV infection.3 The re-
emergence of TB infection is further complicated by an
increase in cases which are resistant to conventional
drug therapy.4 For example, a recent study5 demon-
strated that nearly 19% of tuberculosis isolates in a New
York City hospital were resistant to both isoniazid and
rifampicin, the two most common antitubercular agents.6
Clearly, the development of alternative chemothera-
peutics for Mycobacterium tuberculosis infection is
urgently needed.
intrinsic activity against Gram-negative and/or Gram-
positive bacteria was more important than lipophilicity
at N-1 for activity against mycobacteria. Our results
suggested, however, that increasing the lipophilic char-
acter of the side chain at C-7 may be more important
for antimycobacterial activity than attempts to increase
the lipophilic character at N-1.
Several of the quinolone antibacterials, such as cipro-
floxacin (1a ), sparfloxacin (A), and ofloxacin (B), have
been examined as inhibitors of M. tuberculosis infection
as well as other mycobacterial infections.7 However, to
the best of our knowledge, no large, systematic study
has been undertaken to either optimize the quinolone
antibacterials against M. tuberculosis or examine spe-
cific structure-activity relationships (SAR) of the qui-
nolone antibacterials against mycobacteria. We recently
began such a study and have reported the effect of
changes in the lipophilicity of N-1 phenyl-substituted
fluoroquinolones against mycobacteria.8 The issue of
penetration of compounds into mycobacteria is impor-
tant in the design of new antituberculosis agents since
it is well-known that surface-associated lipids of myco-
bacteria form a transport barrier when compared to the
cell wall of true bacteria.9 We demonstrated that
To investigate this observation in more depth, we
have prepared and evaluated a variety of C-7-substi-
tuted quinolones with varying degrees of substitution
and lipophilicity on the heterocyclic side chain. We have
also examined how these changes are affected by
structural modifications of the substituent at N-1.
Thus, in the present report we describe the synthesis
and biological profile of several selected compounds from
this study and illustrate how changes at N-1 and C-7
of the quinolone nucleus effect antimycobacterial activ-
ity.
Ch em istr y
† Portions of this study were presented at the 35th Interscience
Conference on Antimicrobial Agents and Chemotherapy (ICAAC),
September 1995, San Francisco, CA.
The quinolone nuclei (compounds 1-6) used for the
preparation of final products were prepared according
to literature procedures8,10-12 and are described in Table
X Abstract published in Advance ACS Abstracts, J anuary 15, 1996.
0022-2623/96/1839-0729$12.00/0 © 1996 American Chemical Society

730 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 3
Renau et al.
Ta ble 1. Quinolone Intermediates Used To Prepare Final
Ta ble 2. Piperazinyl and Pyrrolidinyl Side-Chain Substituents
Compounds
(R7) Employed in This Study
a
compd
R1
R7
synth ref
1
2
3
4
5
6
c-C3H5
F
F
F
F
F
F
10
8
11
12
12
12
2,4-F2Ph
CH2CH3
(CH3)3C
(CH3)2CH
c-C4H7
a
c-C3H5, cyclopropyl; 2,4-F2Ph, 2,4-difluorophenyl; CH2CH3,
ethyl; (CH3)3C, tert-butyl; (CH3)2CH, isopropyl; c-C4H7, cyclobutyl.
1. The amine side chains used in the study, identified
by letters a -o, as well as their method of prepara-
tion10,13 are illustrated in Table 2. The synthesis of the
N-alkylated piperazine derivatives 9g-i is shown in
Scheme 1. Briefly, reductive amination14 of N-(tert-
butoxycarbonyl)piperazine (7) with an appropriate car-
bonyl derivative (1-3) using sodium cyanoborohydride
afforded the intermediates 8g-i which were deprotected
with trifluoroacetic acid to furnish 9g-i in modest
yields. Using this method, we found the preparation
of 9g-i to be superior to previous reports which involved
alkylation of piperazine with an appropriate alkyl
halide.15
The compounds listed in Table 3 were prepared from
literature procedures using the provided references.16-23
Synthetic, physical and analytical data of new com-
pounds which have not previously been published are
presented in Tables 3 and 4.
Biologica l Eva lu a tion
The series of N-1- and C-7-substituted quinolones
along with the reference agents ciprofloxacin (1a ) and
sparfloxacin (A) were tested against Mycobacterium
fortuitum (ATCC 6841) and Mycobacterium smegmatis
(ATCC 19420) using a previously described modification
of NCCLS procedures designed for rapidly growing
bacteria.8,24 The compounds were also tested against
four representative Gram-negative and Gram-positive
bacteria by using standard microtitration techniques.25
In both cases, minimum inhibitory concentrations (MICs
in µg/mL) were determined for each compound and are
recorded in Table 5. A computational model (MedChem
Version 3.54, Pomona College, Pomona, CA) was used
to determine the theoretical distribution coefficients (c
log P) for each compound.
Resu lts a n d Discu ssion
The activity of the studied compounds against M.
fortuitum and M. smegmatis and several representative
Gram-negative and Gram-positive bacteria are recorded
in Table 5. As we have previously described,8 the
activity of the compounds against the rapidly growing
organism M. fortuitum has been used as a measure of
M. tuberculosis activity. This approach is especially
useful for the comparison of relative differences in
activity between compounds. Testing results against M.
smegmatis are included for comparative purposes. Gen-
a
Commercially available.
erally, M. fortuitum was more sensitive to the com-
pounds than M. smegmatis.
The effect on antimycobacterial activity of increasing
the lipophilic character of the side chain at C-7 was
studied first. It is generally assumed that the more

Structure-Activity Relationships of the Quinolone Antibacterials
Sch em e 1. Synthesis of Piperazine Derivatives 9g-ia
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 3 731
(ethyl, tert-butyl, isopropyl, and cyclobutyl) since these
groups have been examined extensively in several
antibacterial programs.26 The activity of compounds
3-6 is recorded in Table 5.
The most active agents against mycobacteria in this
analysis were compounds 4, substituted at N-1 with a
tert-butyl group. These compounds were greatly supe-
rior in activity to the N-1-substituted 2,4-difluorophenyl
analogs 2 and slightly better than the N-1 cyclopropyl
analogs 1. Indeed, the activity of N-1 tert-butyl analogs
against mycobacteria was comparable or superior to the
activity of the positive controls, ciprofloxacin (1a ) and
sparfloxacin (A). A number of these agents, along with
additional N-1 tert-butyl-substituted analogs, are cur-
rently being evaluated in the more routine BACTEC
procedure vs M. tuberculosis.28 Note that here again
the compound expected to be the most lipophilic (4f) was
not as active as the unsubstituted 4a .
a
(i) (1) acetone; (2) isobutyraldehyde; (3) butyraldehyde.
lipophilic quinolones should have the best ability to
penetrate the lipid-rich cell wall of mycobacteria.9 Since
we have previously reported8 that antibacterial activity
is a requirement for corresponding activity against
mycobacteria, we focused our initial work on two series
of compounds containing structural features known to
elicit good antibacterial activity.26 The N-1 cyclopropyl-
and 2,4-difluorophenylquinolones (1a -o and 2a -l, re-
spectively) were substituted with a variety of piperazine
and pyrrolidine side chains having varying degrees of
alkyl substitution so as to modify the lipophilic character
of the heterocycle.
The results demonstrate that the N-1 cyclopropyl
derivatives (series 1) were more active against myco-
bacteria than the corresponding N-1 2,4-difluorophenyl
analogs 2. Similar trends were observed for these two
series of compounds in the antibacterial assay. An
increase in lipophilicity via alkyl substitution of the
heterocyclic side chain typically led to a decrease in
antimycobacterial as well as antibacterial activity. For
example, 1h and 2h , containing an isobutyl group at
N-4 of piperazine, were much less active than the less
substituted 1b and 2b. Similarly, the more substituted
pyrrolidines 1l and 2l were less active than the unsub-
stituted 3-aminopyrrolidines 1j and 2j, respectively.
Furthermore, the compounds expected to be the most
lipophilic such as li and 2i (see c log P values, Table 5)
were essentially inactive. In general, the more lipophilic
N-1 phenyl-substituted analogs (2a -l) had less activity
against mycobacteria than the corresponding N-1 cy-
clopropyl derivatives 1a -o.
The N-1 ethyl derivatives (3) were much less active
than compounds 1, 2, and 4, as active as compounds 6,
but slightly more active than the N-1 isopropyl analogs,
5. The cyclobutyl derivatives 6 were more active against
mycobacteria than the isopropyl analogs 5, but similar
trends were observed for both series of compounds in
the antibacterial screen.
The results for series 5, and to a lesser extent series
3 and 6, further demonstrate that (i) intrinsic antibacte-
rial activity is extremely important for corresponding
activity against mycobacteria and (ii) the N-1 position
does not seem to offer a mycobacteria specific group. The
actual degree of antibacterial activity needed for anti-
mycobacterial activity, however, is unknown. For ex-
ample, compounds from series 4 have only modest
antibacterial activity compared to the activity of the
corresponding N-1 cyclopropyl derivatives, even though
the antimycobacterial activity of series 4 is slightly
superior than that of series 1. Indeed, the antibacterial
activity of series 4 was more similar to the correspond-
ing antibacterial activity of compounds 2. Series 4 may
have just the right blend of structural features and
activity toward the gyrase to elicit good antimycobac-
terial activity.
Overall, our results demonstrate that, as a single
variable, lipophilicity of the side chain at C-7 has little
importance for activity against mycobacteria. These
data contradict a recent report suggesting that N-4
alkylation of the piperazine moiety on ciprofloxacin
resulted in compounds with good antimycobacterial
activity.27 The authors of this report, however, exam-
ined a more limited compound set than ours. The
current results, coupled with our previous work in this
area,8 argue that changes in the lipophilicity alone are
most likely irrelevant to antimycobacterial activity. This
is probably due in part to the fact that substituents
which add lipophilicity to the quinolone tend to reduce
overall antibacterial activity. Furthermore, even if
increased lipophilicity is a desirable feature for myco-
bacterial activity, it cannot, by itself, make up for the
loss in activity at the target, DNA gyrase.
To investigate the role changes at N-1 and C-7 have
on antimycobacterial activity, we chose six representa-
tive heterocycles which offered the best activity for
compounds 1 and 2. These included four piperazine
(heterocyclic letters a , c, d and f; Table 2) and two
pyrrolidine side chains (heterocyclic letters j and k ;
Table 2). We chose to examine four substituents at N-1
A comparison of the substitution pattern at C-7
demonstrates that the piperazine-substituted analogs
had essentially the same activity against mycobacteria
as the pyrrolidine-substituted derivatives. While sev-
eral pyrrolidine substituted derivatives (e.g., 1j, 1o, and
2j) were quite active against mycobacteria, other similar
analogs such as 1k -n were less active than the piper-
azine-substituted quinolones 1a -f. These results are
important since pyrrolidine-substituted analogs are
typically more cytotoxic than the corresponding C-7-
substituted piperazines.29 Certainly, the development
of any quinolone for tuberculosis would have to have
an excellent safety profile since it would need to be used
for several months in combination with other antitu-
bercular agents.
It is well-known that pyrrolidines enhance Gram-
positive antibacterial activity whereas piperazine-
substituted analogs are more active against Gram-
negative organisms such as Escherichia coli,26 and the
antibacterial data reported herein supports these previ-
ous observations. Interestingly, our results demon-
strate that, in the case of activity against mycobacteria,
there seems to be no preference for either selective

732 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 3
Renau et al.
Ta ble 3. Synthetic and Physical Data for the Quinolones Tested in This Study

Structure-Activity Relationships of the Quinolone Antibacterials
Ta ble 3 (Continued)
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 3 733
a
b
A: See Experimental Section for general methods A and B. 1: CH3CN, H2O, Et2O wash. 2: Isoelectric precipitation. This procedure
involves dissolving the compound in NaOH to pH 12, filtering to clarify and then slowly adjusting the pH to approximately 7.5. The
resultant solids are collected by filtration. c Yields are those obtained from the coupling step to final product isolation, including hydrolytic
deprotection where applicable.
Ta ble 4. Analytical Data of Compounds Prepared for This
probability that the corresponding MICs of M. fortuitum
Study
were e0.13 µg/mL. A stronger correlation is observed
compd
formula (CHN)a
C19H22N3O3F
when the antibacterial data is used to eliminate weakly
active antimycobacterial agents; ie., when the MICs of
E. coli were g0.4 µg/mL, the probability that the MICs
of M. fortuitum were g0.25 µg/mL was 88%. These
results were supported by data showing that if the MICs
of M. fortuitum were e0.13 µg/mL, there was an 86%
likelihood that the MICs of E. coli were e0.2 µg/mL.
Taken together, these correlations serve to reinforce our
previous observations that the governing requirement
for quinolone activity against mycobacteria is intrinsic
antibacterial activity.
1e
1g
1h
1i
2e
2f
2g
2h
2i
2k
4f
4k
5c
5d
5f
5j
5k
6c
6d
6f
6j
C
C
C
C
C
20H24N3O3F
21H26N3O3F
21H26N3O3F‚0.25H2O
22H20N3O3F3‚H2O
22H20N3O3F3
C23H22N3O3F3
C24H24N3O3F3
C24H24N3O3F3‚0.25H2O
C
C
C
C
C
C
C
C
C
C
C
C
C
22H20N3O3F3‚2.75H2O
20H26N3O3F
20H26N3O3F‚2.20H2O
18H22N3O3F‚2.25H2O
19H24N3O3F‚0.5H2O
19H24N3O3F
17H20N3O3F‚3.25H2O
19H24N3O3F‚HCl/0.5H2O
19H22N3O3F
20H24N3O3F‚0.25H2O
20H24N3O3F
18H20N3O3F‚1.25H2O
20H24N3O3F‚0.75H2O
Exp er im en ta l Section
In str u m en ta l Da ta . Melting points were determined on
a Thomas Hoover melting point apparatus and are uncor-
rected. Infrared (IR) spectra were determined in KBr on a
Mattson Cygnus 1200 FTIR instrument. Proton magnetic
resonance (NMR) were determined at either 300 or 400 MHz
with a Varian Unity 300/400 spectrometer. The chemical shift
values are expressed in δ values relative to the internal
standard tetramethylsilane. Mass spectra were recorded on
a Finnigan TSQ-70 spectrometer. Elemental analyses were
performed in house on a Perkin-Elmer 240 elemental analyzer
or sent to Robertson Microlit Laboratories, Madison, NJ . All
compounds had analytical results (0.4% of theoretical values.
Gen er a l P r oced u r e for th e P r ep a r a tion of th e P ip er -
a zin e Der iva tives 9g-i. 1-Isop r op ylp ip er a zin e (9g). N-
(tert-Butoxycarbonyl)piperazine (7, 18.0 g, 96.6 mmol) was
dissolved in 150 mL of MeOH containing acetone (11.2 g, 193
mmol) and acetic acid (580 mg, 9.66 mmol). The solution was
cooled in an ice bath, and sodium cyanoborohydride (12.0 g,
193 mmol) was added portionwise over 4 h. The reaction
mixture was allowed to warm to room temperature and then
6k
a
Symbols in parentheses refer to those elements analyzed.
Analyses were (0.4% of theoretical values.
Gram-positive or Gram-negative antibacterial activity.
These results could be useful in the development of
other quinolone derivatives for mycobacterial infections.
Having both the antibacterial and antimycobacterial
data together in such a large and varied data set has
allowed us to perform several correlations of the biologi-
cal results. For example, when the MICs of E. coli in
this data set were e0.2 µg/mL, there was a 63%

734 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 3
Renau et al.
Ta ble 5. Biological Testing Results from the Antibacterial and
Mycobacteria Assays, Reported as MIC (µg/mL), and Related c
log P Valuesa
further purification: NMR (CDCl3) δ 2.85 (m, 4H), 2.60 (m,
1H), 2.46 (m, 4H), 1.00 (m, 6H).
P r ep a r a tion of F in a l Qu in olon es. Gen er a l Meth od
A: Com p ou n d s 1e,g-i, 2e-i,k , 4f,k , 5c,d ,f,k , 6c,d ,f,k .
1-ter t-Bu tyl-7-(4-eth ylp ip er a zin -1-yl)-6-flu or o-4-oxo-1,4-
d ih yd r oqu in olin e-3-ca r boxylic Acid (4f). The N-1 tert-
butylquinolone (412, 1.0 g, 3.6 mmol) was suspended in 80 mL
of acetonitrile, and N-ethylpiperazine (1.6 g, 14.2 mmol) was
added. The reaction mixture was heated at reflux for 17 h,
cooled to room temperature, and filtered. The filtrate was
concentrated, the resultant oil diluted with H2O, and the pH
of the water mixture adjusted to 7 with 1 M HCl. The solid
was collected by filtration, washed with H2O and Et2O/EtOH,
and dried at 40 °C in vacuo for 72 h to furnish 890 mg (64%)
of pure 4f: mp 218-219 °C; NMR (DMSO-d6) δ 8.94 (s, 1H),
8.00 (d, 1H), 7.97 (d, 1H), 3.30 (m, 4H), 2.59 (m, 4H), 2.38 (q,
2H), 1.88 (s, 9H), 1.03 (t, 3H); IR (KBr) 1727, 1626 cm-1; MS
(relative intensity) m/ e 376 (100, M + 1), 320 (91). Anal.
C20H26N3O3F (C, H, N).
Gen er a l Meth od B: Com p ou n d s 5j a n d 6j. 7-(3-Am in o-
1-p yr r olid in yl)-6-flu or o-1-isop r op yl-4-oxo-1,4-d ih yd r o-
qu in olin e-3-ca r boxylic Acid (5j). To a solution of 512 (2.0
g, 7.4 mmol) in 80 mL of acetonitrile was added 3-[N-(tert-
butoxycarbonyl)amino]pyrrolidine10 (1.5 g, 8.1 mmol) and
triethylamine (4.5 g, 44.4 mmol). The mixture was heated at
reflux for 5 h and cooled to room temperature. The solid was
collected by filtration and washed with acetonitrile, H2O, and
Et2O to afford 2.2 g of the protected 5j.
antibacterialb
Gram-negative Gram-positive
Mycobacterium
compd EC-1 PA-7 SA-13 SP1-1 fortuitum smegmatis c log P
1a
1b
1c
1d
1e
1f
1g
1h
1i
1j
1k
1l
1m
1n
1o
0.05
0.05
0.05
0.05
0.1
0.05
0.1
0.2
0.1
0.05
0.2
0.1
0.4
0.2
0.4
0.2
0.8
0.8
0.8
1.6
1.6
1.6
0.2
0.8
1.6
3.1
0.8
0.4
0.8
0.2
0.8
0.4
0.8
0.2
0.2
0.4
0.4
0.4
0.2
0.8
0.4
0.2
0.1
0.4
1.6
0.8
>3.1
0.8
0.8
0.8
1.6
>3.1
0.8
0.1
0.8
1.6
0.2
0.05
0.06
0.06
0.06
0.06
0.13
0.06
0.25
1.0
0.25
0.25
0.25
0.13
0.25
0.13
0.25
0.25
0.5
0.25
0.5
0.5
0.5
0.5
2.04
2.89
2.56
3.08
3.09
3.42
3.73
4.35
4.48
1.94
2.13
2.66
2.97
2.62
2.51
1.0
e0.03
0.25
0.5
0.25
0.13
e0.03
0.2
0.1
0.06
2a
2b
2c
2d
2e
2f
2g
2h
2i
0.1
0.2
0.1
0.4
0.4
0.4
0.8
3.1
0.8
0.03
0.2
0.4
0.2
0.8
0.8
0.8
3.1
1.6
3.1
>3.1
3.1
0.2
0.8
1.6
0.4
0.2
0.4
0.4
0.4
0.2
0.4
0.8
0.4
0.05
0.1
0.2
0.4
1.6
0.4
0.8
0.8
0.8
3.1
>3.1
3.1
0.1
0.1
0.1
0.25
0.25
0.13
0.25
0.25
0.5
0.5
2.0
1.0
0.5
0.5
0.5
0.5
1.0
1.0
1.0
4.0
2.0
0.13
0.25
0.5
3.81
4.67
4.33
4.85
4.86
5.20
5.51
6.12
6.25
3.71
3.91
4.44
This compound was dissolved in CH2Cl2 (80 mL), and 30
mL of trifluoroacetic acid was added. The reaction was stirred
at room temperature for 16 h, concentrated to dryness, and
co-evaporated with CH2Cl2 (3 × 50 mL). The oil was diluted
with H2O, the pH of the solution adjusted to 7 with NaOH,
and the solid collected by filtration. The crude solid was
purified by isoelectric precipitation to afford 1.6 g of 5j (65%):
mp 280-281 °C; NMR (DMSO-d6) δ 8.69 (s, 1H), 7.85 (d, 1H),
6.80 (d, 1H), 5.19 (m, 1H), 3.74 (m, 2H), 3.59 (m, 2H), 2.10 (m,
2j
2k
2l
0.13
0.13
0.5
3a
3c
3d
3f
3j
0.1
0.2
0.4
0.1
0.4
3.1
0.8
>3.1
3.1
1.6
0.8
3.1
3.1
0.8
0.2
1.6
1.6
>3.1
>3.1
>3.1
3.1
0.8
0.4
0.5
1.0
0.13
0.25
1.0
2.0
2.0
1.0
0.5
4.0
8.0
2.21
2.73
3.25
3.60
2.11
2.31
1H), 1.75 (m, 1H), 1.55 (d, 6H); IR (KBr) 1630, 1507, 1243 cm-1
;
3k
>3.1
2.0
MS (relative intensity) m/ e 334 (100, M + 1). Anal.
C17H20N3O3F‚3.25H2O (C, H, N).
4a
4c
4d
4f
4j
0.2
0.1
0.2
0.2
0.2
0.4
0.4
0.8
1.6
1.6
0.4
1.6
0.8
0.4
0.4
0.2
0.4
0.2
1.6
>3.1
>3.1
>3.1
0.4
e0.03
0.03
0.06
0.13
0.06
0.13
0.13
0.06
0.06
0.13
0.13
0.25
2.92
3.44
3.96
4.31
2.82
3.02
Ack n ow led gm en t. The authors thank Susan Hagen
for the preparation of 4k and Natalie Rizzo for her
expert technical assistance. The authors thank Chris-
topher Gajda for review of the manuscript. This study
was supported by an NCDDG for opportunistic infec-
tions, AI35170-02 from the NIAID.
4k
0.2
5a
5c
5d
5f
5j
0.8
0.8
1.6
1.6
0.8
3.1
1.6 >3.1
>3.1
>3.1
>3.1
>3.1
>3.1
3.1
1.0
0.5
0.5
1.0
1.0
2.0
4.0
2.0
2.0
4.0
2.0
8.0
2.52
3.04
3.56
3.91
2.42
2.62
3.1
>3.1
>3.1
1.6
3.1
3.1
3.1
3.1
3.1
Refer en ces
5k
>3.1
(1) (a) Cantwell, M. F.; Snider, D. E. J r.; Cauthen, G. M.; Onorato,
I. M. Epidemiology of tuberculosis in the United States, 1985-
1992. J . Am. Med. Assoc. 1994, 272, 535-539. (b) Onorato, I.
M.; McCray, E. and the Field Services Branch. J . Infec. Dis.
1992, 165, 87-92. (c) Burwen, D. R.; Bloch, A. B.; Griffin, L. D.;
Ciesielski, C. A.; Stern, H. A.; Onorato, I. M. National trends in
the occurrence of tuberculosis and acquired immunodeficiency
syndrome. Arch. Intern. Med. 1995, 155, 1281-1286.
6a
6c
6d
6f
6j
0.4
0.4
0.4
0.8
0.4
0.8
1.6
1.6
3.1
>3.1
1.6
3.1
3.1
3.1
3.1
3.1
0.8
>3.1
>3.1
>3.1
>3.1
1.6
0.5
2.0
1.0
0.5
2.0
1.0
4.0
2.60
3.12
3.64
3.98
2.50
2.69
0.25
0.13
0.5
1.0
2.0
6k
3.1
1.6
A
0.025
0.8
0.05
0.1
0.06
0.13
2.42
(2) Alland, D.; Kalkut, G. E.; Moss, A. R.; McAdam, R. A.; Hahn, J .
A.; Bosworth, W.; Drucker, E.; Bloom, B. R. Transmission of
tuberculosis in New York city. An analysis by DNA fingerprint-
ing and conventional epidemiologic methods. N. Engl. J . Med.
1994, 330, 1710-1716.
(3) (a) Wallis, R. S.; Vjecha, M.; Amir-Tahmasseb, M.; Okwera, A.;
Byekwaso, F.; Nyole, S.; Kabengera, S.; Mugerwa, R. D.; Ellner,
J . J . Influence of tuberculosis on human immunodeficiency virus
(HIV-1): enhanced cytokine expression and elevated â2-micro-
globulin in HIV-1 associated tuberculosis. J . Infec. Dis. 1993,
167, 43-48. (b) Whalen, C.; Horsburgh, C. R.; Hom, D.; Lahart,
C.; Simberkoff, M.; Ellner, J . Accelerated course of human
immunodeficiency virus infection after tuberculosis. Am. J .
Respir. Crit. Care Med. 1995, 151, 129-135.
(4) (a) J acobs, R. F. Multiple-drug-resistant tuberculosis. Clin. Infec.
Dis. 1994, 19, 1-10. (b) Bloch, A. B.; Cauthen, G. M.; Onorato,
I. M.; Dansbury, K. D.; Kelly, G. D.; Driver, C. R.; Snider, D. E.
Nationwide survey of drug-resistant tuberculosis in the United
States. J . Am. Med. Assoc. 1994, 271, 665-671.
(5) Weltman, A. C.; Rose, D. N. Tuberculosis susceptibility patterns,
predictors of multidrug resistance, and implications for initial
therapeutic regimens at a New York city hospital. Arch. Intern.
Med. 1994, 154, 2161-2167.
a
Assay techniques and determination of c log P values described
in text. b EC-1, Escherichia coli Vogel; PA-7, Pseudomonas aerugi-
nosa U1-18; SA-13, Staphylococcus aureus H-228; SP1-1, Strep-
tococcus pyogenes C203. A ) sparfloxacin.
stirred for 48 h. At this time 50 mL of a saturated solution of
NaHCO3 was added, and the mixture was extracted directly
into CH2Cl2. The organic fractions (3 × 100 mL) were washed
with H2O, collected, and dried over Na2SO4. The solution was
filtered and the filtrate concentrated in vacuo to afford the
intermediate 8g as an oil.
A solution of 8g in 30 mL of trifluoroacetic acid was stirred
at room temperature for 16 h and then evaporated to dryness
and co-evaporated with CH2Cl2 (2 × 50 mL). The oil was
diluted with H2O and the pH adjusted to 12 with NaOH. The
title compound was extracted into CH2Cl2 (6 × 100 mL) and
the organic fractions were pooled, dried over Na2SO4, and
filtered. The filtrate was concentrated to dryness to afford 6.3
g of 9g (51%) as a tan liquid. This material was used without

Structure-Activity Relationships of the Quinolone Antibacterials
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 3 735
(6) Houston, S.; Fanning A. Current and potential treatment of
tuberculosis. Drugs 1994, 48, 689-708.
(17) Domagala, J . M.; Bridges, A. J .; Culbertson, T. P.; Gambino, L.;
Hagen, S. E.; Karrick, G.; Porter, K.; Sanchez, J . P.; Sesnie, J .
A.; Spense, G.; Szotek, D.; Wemple, J . Synthesis and biological
activity of 5-amino and 5-hydroxyquinolones, and the over-
whelming influence of the remote N1-substituent in determining
the structure-activity relationship. J . Med. Chem. 1991, 34,
1142-1154.
(18) Chu, D. T. W.; Fernandes, P. B.; Claiborne, A. K.; Pihuleac, E.;
Nordeen, C. W.; Maleczka, R. E., J r.; Pernet, A. G. Synthesis
and structure-activity relationships of novel arylfluoroquinolone
antibacterial agents. J . Med. Chem. 1985, 28, 1558-1564.
(19) Narita, H.; Konishi, Y.; Nitta, J .; Nagaki, H.; Kobayashi, Y.;
Watanabe, Y.; Minami, S.; Saikawa, I. Pyridonecarboxylic acids
as antibacterial agents. IV. Synthesis and structure-activity
relationship of 7-amino-1-aryl-6-fluoro-4-quinolone-3-carboxylic
acids. Yakugaku Zasshi 1986, 106, 795-801.
(20) Hagen, S. H.; Domagala, J . M.; Heifetz, C. L.; J ohnson, J .
Synthesis and biological activity of 5-alkyl-1,7,8-trisubstituted-
6-fluoroquinoline-3-carboxylic acids. J . Med. Chem. 1991, 34,
1155-1161.
(21) Koga, H.; Itoh, A.; Murayama, S.; Suzue, S.; Irikura, T. Structure-
activity relationships of antibacterial 6,7- and 7,8-disubstituted
1-alkyl-1,4-dihydro-4-oxoquinoline-3-carboxylic acids. J . Med.
Chem. 1980, 23, 1358-1363.
(22) Domagala, J . M.; Heifetz, C. L.; Mich, T. F.; Nichols, J . B. 1-ethyl-
7-[3-[(ethylamino)methyl]-1-pyrrolidinyl]-6,8-difluoro-1,4-dihy-
dro-4-oxo-3-quinoline-carboxylic acid. New quinolone antibac-
terial with potent Gram-positive activity. J . Med. Chem. 1986,
29, 445-448.
(23) Bouzard, D.; Di Cesare, P.; Essiz, M.; J acquet, J . P.; Kiechel, J .
R.; Remuzon, P.; Weber, A.; Oki, T.; Masuyoshi, M.; Kessler, R.
E.; Fung-Tomc, J .; Desiderio, J . Fluoronaphthyridines and
quinolones as antibacterial agents. 2. Synthesis and structure-
activity relationships of new 1-tert-butyl 7-substituted deriva-
tives. J . Med. Chem. 1990, 33, 1344-1352.
(24) National Committee for Clinical Laboratory Standards. Methods
for dilution susceptibility tests for bacteria that grow aerobically,
3rd ed.; antimicrobial approved standard; NCCLS publication
M7-A3: Villanova, PA, April 1993.
(25) Cohen, M. A.; Griffin, T. J .; Bien, P. A.; Heifetz, C. L.; Domagala,
J . M. In vitro activity of CI-934, a quinolone carboxylic acid
active against gram-positive and gram-negative bacteria. Anti-
microb. Agents Chemother. 1985, 28, 766-772.
(7) (a) Gorzynski, E. A. In vitro activity of fluoroquinolones against
Mycobacterium tuberculosis. Antimicrob. Newslett. 1989, 6, 45-
48. (b) Leysen, D. C.; Haemers, A.; Pattyn, S. R. Mycobacteria
and the new quinolones. Antimicrob. Agents Chemother. 1989,
33, 1-5. (c) Caekenberghe, D. V. Comparative in-vitro activities
of ten fluoroquinolones and fusidic acid against Mycobacterium
spp. J . Antimicrob. Chemother. 1990, 26, 381-386. (d) Berlin,
O. G. W.; Young, L. S.; Bruckner, D. A. In-vitro activity of six
fluorinated quinolones against Mycobacterium tuberculosis. J .
Antimicrob. Chemother. 1987, 19, 611-615. (e) Davies, S.;
Sparham, P. D.; Spencer, R. C. Comparative in-vitro activity of
five fluoroquinolones against mycobacteria. J . Antimicrob.
Chemother. 1987, 19, 605-609. (f) Karak, K.; De, P. K. Com-
parative in vitro activity of fluoroquinolones against Mycobac-
terium tuberculosis. Indian J . Med. Res. 1995, 101, 147-149.
(8) Renau, T. E.; Sanchez, J . P.; Shapiro, M. A.; Dever, J . A.;
Gracheck, S. J .; Domagala, J . M. Effect of lipophilicity at N-1
on activity of fluoroquinolones against mycobacteria. J . Med.
Chem. 1995, 38, 2974-2977.
(9) Besra, G. S.; Chatterjee D. Lipids and carbohydrates of Myco-
bacterium tuberculosis. In Tuberculosis; Bloom, B. R., Ed; ASM
Press: Washington, DC, 1994; pp 285-306.
(10) Sanchez, J . P.; Domagala, J . M.; Hagen, S. E.; Heifetz, C. L.;
Hutt, M. P.; Nichols, J . B.; Trehan, A. K. Quinolone antibacterial
agents. Synthesis and structure activity relationships of 8-sub-
stituted quinolone-3-carboxylic acids and 1,8-naphthyridine-3-
carboxylic acids. J . Med. Chem. 1988, 31, 983-991.
(11) Ciba-Geigy A. G. Quinolinecarboxylic acid fungicides. Chem.
Abstr. 1979, 90, 163334j.
(12) Bouzard, D.; Di Cesare, P.; Essiz, M.; J acquet, J . P.; Remuzon,
P.; Weber, A.; Oki, T.; Masuyoshi M. Fluoronaphthyridines and
quinolones as antibacterial agents. 1. Synthesis and structure-
activity relationships of new 1-substituted derivatives. J . Med.
Chem. 1989, 32, 537-542.
(13) Domagala, J . M.; Hagen. S. E.; J oannides, T.; Kiely, J . S.;
Laborde, E.; Schroeder, M. C.; Sesnie, J . A.; Shapiro, M. A.; Suto,
M. J .; Vanderroest, S. Quinolone antibacterials containing the
new 7-[3-(1-aminoethyl)-1-pyrrolidinyl] side chain: the effects
of the 1-aminoethyl moiety and its stereochemical configurations
on potency and in vivo efficacy. J . Med. Chem. 1993, 36, 871-
881.
(14) Lane, C. F. Sodium cyanoborohydride-a highly selective reducing
agent for organic functional groups. Synthesis 1975, 135-146.
(15) (a) Yung, D. K.; Chatten, L. G.; MacLeod, D. P. Potential
antiarrhythmic agents. I. Synthesis and pharmacological evalu-
ation of some piperazine and ethylenediamine analogs of procaine
amide. J . Pharm. Sci. 1968, 57, 2073-2080. (b) Marsella, J . A.
Ruthenium-catalyzed reactions of ethylene glycol with primary
amines: steric factors and selectivity control. J . Organomet.
Chem. 1991, 407, 97-105. (c) Yamane, T.; Hashizume, T.;
Yamashita, K.; Konishi, E.; Hosoe, K.; Hidaka, T.; Watanabe,
K.; Kawaharada, H.; Yamamoto, T.; Kuze, F. Synthesis and
biological activity of 3′-hydroxy-5′-aminobenzoxazinorifamycin
derivatives. Chem. Pharm. Bull. 1993, 41, 148-155.
(26) Chu, D. T. W.; Fernandes, P. B. Recent developments in the field
of quinolone antibacterial agents. In Advances in Drug Research;
Testa, B., Ed.; Academic Press: New York, 1991; pp 39-144.
(27) Haemers, A.; Leysen, D. C.; Bollaert, W.; Zhang, M.; Pattyn, S.
R. Influence of N substitution on antimycobacterial activity of
ciprofloxacin. Antimicrob. Agents Chemother. 1990, 34, 496-497.
(28) Heifets, L. B.; Good, R. C. Current laboratory methods for the
diagnosis of tuberculosis. In Tuberculosis; Bloom, B. R., Ed.;
ASM Press: Washington, DC, 1994; pp 85-110.
(29) Domagala, J . M. Structure-activity side-effect relationships for
the quinolone antibacterials. J . Antimicrob. Chemother. 1994,
33, 685-706.
(16) Grohe, K.; Heitzer, H. Cycloaracylierung von enaminen, I.
Synthese von 4-chinolon-3-carbonsaueren. Liebigs Ann. Chem.
1987, 29-37.
J M9507082