Synthesis and antibacterial activities of new piperidine substituted (5R)-[1,2,3]triazolylmethyl and (5R)-[(4-F-[1,2,3]triazolyl)methyl] oxazolidinones

Article abstract of DOI:10.1016/j.bmcl.2013.01.033

A novel series of 5(R)-[1,2,3]triazolylmethyl and (5R)-[(4-F-[1,2,3] triazolyl)methyl]oxazolidinones having various piperidine group were synthesized and evaluated antibacterial activity against clinically isolated resistant strains of Gram-positive and Gram-negative bacteria. The compound 12a having exo-cyanoethylidene group in the 4-position of piperidine ring was found to be two to threefold more potent than the linezolid against penicillin-resistant Staphylococcus pneumonia and Staphylococcus agalactiae, and also exhibited reduced MAO-B inhibitory activity.

Full text of DOI:10.1016/j.bmcl.2013.01.033

Bioorganic & Medicinal Chemistry Letters 23 (2013) 1193–1196
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Synthesis and antibacterial activities of new piperidine substituted
(5R)-[1,2,3]triazolylmethyl and (5R)-[(4-F-[1,2,3]triazolyl)methyl]
oxazolidinones
⇑
⇑
Hyo-Nim Shin, Seon Hee Seo, Hyunah Choo, Gyochang Kuem, Kyung Il Choi , Ghilsoo Nam
Center for Neuro-Medicine, Brain Science Institute, Korea Institutes of Science and Technology (KIST), Hwarangno 14-gil 5, Seoungbuk-gu, Seoul 136-791, South Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
A novel series of 5(R)-[1,2,3]triazolylmethyl and (5R)-[(4-F-[1,2,3]triazolyl)methyl]oxazolidinones having
various piperidine group were synthesized and evaluated antibacterial activity against clinically isolated
resistant strains of Gram-positive and Gram-negative bacteria. The compound 12a having exo-cyanoethy-
lidene group in the 4-position of piperidine ring was found to be two to threefold more potent than the
linezolid against penicillin-resistant Staphylococcus pneumonia and Staphylococcus agalactiae, and also
exhibited reduced MAO-B inhibitory activity.
Received 30 July 2012
Revised 3 January 2013
Accepted 8 January 2013
Available online 16 January 2013
Keywords:
Oxazolidinone
Antibiotics
Ó 2013 Elsevier Ltd. All rights reserved.
Synthesis
Antibacterial activity
Multidrug-resistant Gram-positive bacteria are an increasingly
pressing problem in clinic. Linezolid (Zybox, 1), an oxazolidinone
antibiotics approved for clinical use orally, represent new class
of antibiotic that has been very effective in treating multidrug-
resistant Gram-positive pathogens.1 The action mechanism of
oxazolidinone is known for inhibiting of initial stage of protein
synthesis which is formation of 70S mRNA initiation complex
due to binding of 30S mRNA and 50S ribosome through
fMet–tRNA.2 Linezolid has competes with chloramphenicol and
lincomycin because of having similar binding site but has only
infrequent cross-resistance between linezolid and chlorampenicol
or lincosamicine due to different mechanism.3 Because linezolid
has a novel mechanism of action, linezolid has same activity
against many antibiotic-sensitive and antibiotic-resistant bacteria,
and is active against methicillin resistant and vancomycin resis-
tant bacteria.4 Therefore therapeutic usage of linezolid is impres-
sively increased annually worldwide since its approval in 2000.
However, linezolid resistant organisms have been developed and
treatment failures have been reported.5 To overcome these un-
wanted drawbacks, further generation of oxazolidinone antibiot-
ics active against the resistance organisms are still needed
and actively studied by several research groups.6 Recently, we
reported that cyanomethylenepiperidinyl oxazolidinones (2)
showed good antibacterial activity against multidrug-resistant
strains including methicilline-resistant Staphylococcus aureus
(MRSA), Staphylococcus epidermidis (MRSE) and vancomycin resis-
tant enterococci (VRE).7 As a continuous effort to improve the po-
tency and broaden the spectrum of the oxazolidinine antibacterial
agents, we interested in the influence of substituent variation of
piperidine ring on the antibacterial activity of piperidinylphenyl
oxazolidinones having triazole heterocycle at the C-5 position of
oxazolidinone A-ring. It is reported that the introducing 1,2,3-tri-
azole ring instead of acetamide on the C-5 position of oxazolidi-
none core enhanced the antibacterial activity and among them,
4-substituted 1,2,3-triazole analogues were known to sustain
their antibacterial activities.8
Here we describe the synthesis of a novel series of 5(R)-
[1,2,3]triazolyl and (5R)-[(4-F-[1,2,3]triazolyl)methyl]oxazolidi-
nones having various piperidinyl moieties including 4-substituted
methyl-3-ene-piperidinyl groups, 4-substituted-exo-methylene-
piperidinyl, 4-substitutedpiperidinyl, and 4-substituted-3-ene-
piperidinyl as a modification of morpholine C-ring of linezolid
(Fig. 1), and evaluation of their biological activity against Gram-po-
sitive and Gram-negative bacteria clinically isolated strains in
South Korea. Also we tested their CYP profile, hERG inhibition,
and mitochondrial monoamine oxidase (MAO) inhibition for the
evaluation of toxicity.
The synthesis of oxazolidinone derivatives having 1,2,3-tria-
zoles at the C-5 position of oxazolidinone ring were started from
the known ketone intermediate 3 as shown in Scheme 1.9
The cycloaddition reaction of azide 3 with vinyl acetate or phe-
nyl
a
–fluorovinyl sulfone10 gave triazole 4a and 4-fluoro-1,2,3-tri-
⇑
Corresponding authors. Tel.: +82 2 958 5166; fax: +82 2 958 5189.
E-mail addresses: kichoi@kist.re.kr (K.I. Choi), gsnam@kist.re.kr (G. Nam).
azole 4b respectively.11
0960-894X/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2013.01.033

1194
H.-N. Shin et al. / Bioorg. Med. Chem. Lett. 23 (2013) 1193–1196
O
O
O
O
O
N
N
N
N
NHAc
NHAc
NC
F
F
2
Linezolid 1
O
2
3
O
1
R
Piperidine
N
A
B
N
N
5
4
N
F
R = H or F
R2
R3
NC
HO
N
Piperidine
=
N
NC
N
N
R1
Figure 1. Known oxazolidines and new triazolyl-oxazolidinones bearing piperidine group.
O
O
N
O
O
N
N
N3
a
b
R = H ( ), F ( )
3
F
F
i) or ii)
O
O
R
R
iii)
O
O
N
N
N
F
N
N
R1
N
N
N
N
: R1 = CN
5a 5b
,
4a 4b
,
6a : R1 = CO2Et
v)
iv)
O
R
O
R
N
R2
R3
O
N
HO
O
N
N
N
N
N
N
N
NC
N
N
N
F
F
13a, 13b
F
vi)
2
3
7a 7b
,
: R , R = H, CN
8a, 8b : R32, R3 = H, CO2Et
O
O
R
N
2
9a
: R , R =2H, COCH3
10a 10b
,
: R , R3 = CH3, CO2Et
NC
N
11a, 11b : R2, R3 = Cl, CO2Et
N
2
3
12a 12b
,
: R , R = CH3, CN
14a, 14b
Scheme 1. Reagents and conditions: (i) vinyl acetate, reflux; (ii) 1-(benzenesulfonyl)-1-fluoroethene, toluene, reflux; (iii) R1CH2CO2H, toluene, MS, 105 °C; (iv)
R2R3CH2P(@O)(OEt)2, NaH, THF or CNCH2R2, Al2O3; (v) TMSCN, InBr3, CH2Cl2, 0 °C, then formic acid, rt; (vi) POCl3, pyridine, rt.
A series of 4-substituted-methyl-3-ene-piperidyl (5a, 5b, and
6b) were prepared from ketone intermediates (4a, 4b) by employ-
ing modified Knoevenagel condensation with cyano acetic acid or
monomethyl malonate under high temperature. Knoevenagel
condensation or Wadsworth–Hornor–Emmons reaction of ketones
4a and 4b provided 4-substituted-exo-methylenepiperidinyl deriv-
atives (7–12) in 63–95% yields. The addition reaction of cyanide
into carbonyl group with TMSCN in the presence of indium bro-
mide followed by acidic deprotection of TMS group afforded the
corresponding cyanohydrin derivatives (13a, 13b). The dehydra-
tion of the corresponding cyanohydrin compounds with POCl3
and pyridine gave the cyano(endo-methylene)piperidyl derivatives
(14a, 14b) in 30% yields.
yl)methyl-3-[(30-fluoro-40piperidinyl)phenyl]oxazolidinones (5b–
14b) derivatives12 were tested for in vitro antimicrobial activity
against Gram-positive strains such as methicillin-resistant Staphy-
lococcus aureus (MRSA), methicillin-resistant Coagulase negative
staphylococci (MRCS) vancomycin-resistant Enterococcus faecalis,
(VRE), Streptococcus pneumonia (penicillin resistance and interme-
diate, PRSP), and Streptococcus agalactiae (S.a.) betalactamase posi-
tive Haemophilus influenzae {(H.i.(+)} clinically acquired in Korea.
The minimum inhibitory concentration (MIC) values of produced
by the Muller–Hinton agar dilution method13 for the compounds
(2, 5–14) are reported in Table 1.
Most of the obtained piperidinyl–oxazolidinone derivatives
bearing triazolyl C-5 side chain of oxazolidinone A-ring (5a–14a)
showed good activity comparable or superior to linezolid against
clinically isolated Gram-positive strains. Variation of piperidinyl
The all of 5(R)-[1,2,3]triazolylmethyl-3-[(30-fluoro-40-piperidi-
nyl)phenyl]oxazolidinones (5a–14a) and 5(R)-(4-F-[1,2,3]triazol-

H.-N. Shin et al. / Bioorg. Med. Chem. Lett. 23 (2013) 1193–1196
1195
Table 1
In vitro antibacterial activity of triazolyloxazolidinone derivatives (MIC,
l
g/mL)a
O
O
R
Piperidine
N
R1
R1
R2
R1
R2
R1
N
N
N
=
N
N
N
Piperidine R2
N
F
R = H or F
5-6
7-12
13
14
i
Compd
MRSAb
MRCSc
VREd
3.12
3.12
100
6.25
3.12
50
25
100
3.12
6.25
100
12.5
100
1.56
100
3.12
100
3.12
50
3.12
VREe
PRS.p.f
S.pg
S.ah
H.i.(+)
2
5a
5b
6a
7a
7b
8a
8b
3.12
3.12
100
6.25
3.12
50
3.12
3.12
100
6.25
3.12
100
25
100
3.12
12.5
100
25
3.12
3.12
100
6.25
1.56
50
0.39
0.39
50
0.78
0.39
25
1.56
0.39
50
6.25
50
0.78
0.78
100
6.25
50
0.39
6.25
0.78
6.25
1.56
0.78
1.56
25
1.56
0.78
0.78
1.56
12.5
1.56
0.39
6.25
6.25
6.25
0.78
0.78
100
3.12
0.78
6.25
100
12.5
100
1.56
1.56
100
6.25
25
0.19
12.5
1.56
12.5
1.56
100
1.56
25
25
12.5
100
3.12
12.5
100
25
100
1.56
100
3.12
100
3.12
100
3.12
100
6.25
6.25
100
25
100
1.56
100
3.12
100
3.12
50
6.25
1.56
1.56
100
6.25
50
0.39
6.25
1.56
6.25
1.56
6.26
0.78
9a
10a
10b
11a
11b
12a
12b
13a
13b
14a
14b
Linezolid
12.5
100
100
1.56
100
3.12
100
3.12
100
3.12
0.19
6.25
0.78
6.25
1.56
6.25
0.78
50
0.78
1.56
a
b
c
d
e
f
Minimum inhibitory concentration by agar dilution method.
Methicillin-resistant Staphylococcus aureus C463.
Methicillin-resistant Coagulase negative staphylococci.
Vancomycin-resistant Enterococcus faecalis C474.
Vancomycin-resistant Enterococcus faecium C803.
penicillin-resistant Staphylococcus pneumonia C402.
Staphylococcus pyogenes 308A.
g
h
i
Staphylococcus agalactiae ATCC 2901.
Betalactamase positive Haemophilus influenzae.
group such as exomethylene (7a–12a), endomethylene (5, 6, 14a)
or saturated (13a) piperidinyl group represent a little effect on
their antimicrobial activity. Among the screened compounds (2,
5–14) the cyanoethylidene compound 12a showed most potent
activity against all tested strains. The exo-cyanomethylene com-
pound 7a twofold higher activity against vancomycin-resistant
Enterococcus faecium and Staphylococcus pyogenes compare to its
C-5 acetamide oxazolidinone analogue 2. Although the variation
of piperidine ring have affected a little to the activity, the cyano
group on exomethylene type played an important role on the anti-
bacterial activity. However, all of 4-fluoro-[1,2,3]-triazole deriva-
tives (5b, 7b–14b) lost the activity against MRSA, MRCS and VRE
strains. The replacement of triazole group with 4-fluoro-[1,2,3]-tri-
azole group led to loss of antibacterial activity. The cyanomethyl-
ene compound 7b having 4-fluoro-[1,2,3]-triazole moiety was
inactive for all tested strains.
The most active two compounds 7a and 12a were profiled cyto-
chrome P450 (CYP) inhibition liabilities14 involved in drug–drug
interaction and also evaluated for hERG channel,15 MAO-A and
MAO-B enzyme activities.16 And the toxicity profiling data of cor-
responding 4-F-[1,2,3]-triazol derivatives 7b and 12b were also
presented for comparison (Table 2).
Both compounds 7a and 12a showed low inhibitory activities
against hERG and CYP except for the 3A4 inhibition of 12a. It
means that both compound found to have no problems involved
in drug metabolism and drug interaction. The compound 7a
The potency of MAO-B for 7a improved 3.5-fold relative to linezo-
lid as shown almost no inhibition, but the inhibition of MAO-A
which lead to severe hypertensive crises, increased compare to
linezolid.
Although the inhibition of MAO-A still sustained strong, the
compound 12a exhibits 10-fold reduced inhibitory activity against
MAO-A relative to compound 7a and also the inhibitory activity of
MAO-B showed threefold decreased compare to linezolid. While
the corresponding 4-F-[1,2,3]triazole derivatives 7b and 12b
showed over 10-fold higher inhibitory activities against hERG
channel than their unsubstitiuted trialzoles 7a and 12a, they
showed almost no inhibition against 1A2 and 2D6. In case of
12b, all of CYP-450 inhibitory activity is decreased compare to
12a. Therefore the 4-F-substitution of 1,2,3-triazole ring might be
good effect for reducing toxicity induced from CYP-450. The
MAO-A activity of 7b was reduced over 10-fold compare to 7a.
In summary, new series of 5(R)-[1,2,3]-triazolyl or 5(R)-(4-F-
[1,2,3]-triazolyl)methyl-3-[(30-fluoro)phenyl]oxazolidinone deriv-
atives containing various piperidinyl moieties on 40-position of
phenyl ring were designed, synthesized and evaluated for the anti-
bacterial activity against clinically isolated Gram-positive and
Gram-negative strains. We observed that the introducing of 4-flu-
oro-1,2,3-triazole group at C-5 position of oxazolidinone ring
showed loss of antibacterial activities. Although the biological
activity showed a little differences according to the variation of
piperidine moieties, compounds 12a having exo-cyanoethylidene
group in the 4-position of piperidine ring was found to be two to
threefold more potent than the linezolid against penicillin-resis-
tant Staphylococcus pneumonia and Staphylococcus agalactiae, and
also exhibited reduced MAO-B inhibitory activity.
exhibits high IC50 value (49.5 2.12 lM) against hERG channel
which plays a crucial role on cardiac side effects of drugs. And also
show high remaining activities for isozymes of CYP 450, indicating
that it is not affected in drug metabolism and drug interaction.

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H.-N. Shin et al. / Bioorg. Med. Chem. Lett. 23 (2013) 1193–1196
Table 2
Human hERG channel and CYP inhibition profile of selected compounds
a
Compd
hERG (IC50
,
lM)
% Control of CYP-450 (10
2D6 2C9
80.87
117.2
65.09
106.35
l
M)b
MAO (remaining%, 10 lM)
1A2
3A4
hMAO-Ac
hMAO-Bd
7a
7b
12a
12b
49.50 2.12
2.37 1.16
213.32 32.0
21.00 1.63
55.19
91.77
45.73
92.76
88.01
66.57
61.49
64.84
32.03
23.65
7.45
3.54
50.6
34.8
10.2
6.79
111.30
19.5
74.81
34.8
21.44
Linezolid
31.41
a
b
c
Human egg.
Values are remained% activities and the mean SD of triplicate determinations.
Monoamine oxidase A in human.
Monoamine oxidase B in human.
d
(m, 1H), 3.76–3.60 (m, 7H), 3.12 (s, 5H), 2.48 (2H); 6a 1H NMR (CDCl3,
300 MHz) d 8.03 (1H), 7.62–7.50 (m, 2H), 6.89 (1H), 5.20 (s, 1H), 5.05 (m, 1H),
4.81 (m, 2H), 4.16 (1H), 3.93 (1H), 3.12 (m, 4H), 2.76 (t, J = 5.28 Hz, 2H), 2.53 (t,
J = 5.28 Hz, 2H); 7a 1H NMR (300 MHz, CDCl3) d 7.79 (1H), 7.75 (1H), 7.32 (dd,
J = 14.0 Hz, 1.2 Hz, 1H), 6.97 (dd, J = 8.7 Hz, 1.1 Hz, 1H), 6.91 (t, J = 9.1 Hz, 1H),
5.19 (s, 1H), 5.08 (m, 1H), 4.79 (2H), 4.16 (t, J = 7.1 Hz, 1H), 3.93 (m, 1H), 3.16
(m, 4H), 2.78 (t, J = 5.28 Hz, 2H), 2.54 (t, J = 5.28 Hz, 2H). 13C NMR (300 MHz,
This work was financially supported by the Ministry of Science
and Technology (MOST) and Korea Institute of Science and Tech-
nology (KIST).
References and notes
CDCl3)
d 163.70, 157.01, 153.32, 134.55, 125.04, 119.86, 116.37, 114.27,
108.04, 93.90, 70.30, 51.97, 47.34, 35.30, 32.79; 12a 1H NMR (300 MHz, CDCl3)
d 7.79 (1H), 7.74 (1H), 7.32 (dd, J = 14.2 Hz, 2.6 Hz, 1H), 6.97 (dd, J = 8.8 Hz,
1.7 Hz, 1H), 6.90 (t, J = 9.1 Hz, 1H), 5.09 (m, 1H), 4.80 (2H), 4.16 (1H), 3.93 (1H),
3.12 (m, 4H), 2.78 (t, J = 5.4 Hz, 2H), 2.55 (t, J = 5.5 Hz, 2H), 2.00 (s, 3H), 1.93 (s,
3H). 13C NMR (300 MHz, CDCl3) d 157.95, 154.18, 153.38, 136.54, 134.53,
132.45, 125.08, 119.68, 114.31, 107.99, 102.32, 70.34, 51.98, 47.35, 34.15,
29.85, 15.45; 7b 1H NMR (CDCl3, 300 MHz) d 8.03 (1H) 7.62–7.50 (m, 2H), 6.89
(1H), 5.20 (s, 1H), 5.05 (m, 1H), 4.81 (m, 2H), 4.16 (1H), 3.93 (1H), 3.12 (m, 4H),
2.76 (t, J = 5.28 Hz, 2H), 2.53 (t, J = 5.28 Hz, 2H); 12b 1H NMR (CDCl3, 300 MHz)
d 8.04 (m, 1H), 7.52–7.68 (m, 2H), 6.90 (m, 1H), 5.09 (m, 1H), 4.80 (2H), 4.16
(1H), 3.93 (1H), 3.12 (m, 4H), 2.78 (t, J = 5.4 Hz, 2H), 2.55 (t, J = 5.5 Hz, 2H), 2.00
(s, 3H); 13a 1H NMR (DMSO, 300 MHz, d): 8.16 (1H), 7.76 (1H), 7.45–7.37 (1H),
7.14–7.07 (2H), 6.75(–OH), 5.12 (m, 1H) 4.83 (2H), 4.20 (1H), 3.87(1H), 3.22 (m,
2H) 2.93 (m, 2H) 2.08 (m, 2H) 1.93 (m, 2H); 13b 1H NMR (CDCl3, 300 MHz) d
7.76 (m, 1H), 7.45–7.37 (2H), 7.01 (1H) 6.75 (–OH), 4.89 (m, 1H), 4.60 (2H),
3.87 (2H), 3.13 (2H), 2.91 (2H), 2.09 (2H), 1.94 (2H); 14a 1H NMR (CDCl3,
300 MHz, d): 7.79–7.74 (2H), 7.33–7.28 (1H), 6.99–6.96 (1H), 6.91–6.85 (1H),
6.67 (s, 1H), 5.08–5.02 (m, 1H), 4.79 (2H), 4.17–4.10 (t, 1H), 3.93–3.88 (1H),
3.40 (2H), 3.25 (2H), 2.08 (2H); 14b 1H NMR (CDCl3, 300 MHz) d 8.03 (m, 1H),
7.62–7.49 (m, 2H), 6.88 (m, 1H), 5.05 (1H), 4.79 (2H), 4.12 (m, 1H), 3.86 (1H),
3.12 (2H), 2.13 (2H), 1.90 (2H).
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300 MHz) d 7.50–7.44 (dd, 1H), 7.10–7.06 (dd, 1H), 7.00–6.94 (t, 1H), 6.38 (NH,
1H), 4.80–4.77 (m, 1H), 4.06–4.00 (t, 1H), 3.80–3.77 (t, 1H), 3.69–3.63 (m, 2H),
3.67 (t, 4H), 2.62 (t, 4H), 2.03 (s, 3H) 13C NMR (CDCl3, 300 MHz) d 208.42,
171.59, 154.76, 136.12, 133.79, 120.30, 114.27, 107.76, 72.36, 64.74, 51.22,
48.00, 42.30, 23.51.; (b) 4b 1H NMR (300 MHz, CDCl3) d 8.08–8.05 (m, 1H),
7.65–7.51 (m, 2H), 6.92–6.90 (m, 1H), 5.12–5.01 (m, 1H), 4.81–4.60 (m, 2H),
4.11–4.00 (m, 2H), 3.39–3.35 (m, 4H), 2.64–2.60 (m, 4H).
12. Representative spectroscopic data of selected compounds which were evaluated
biological activity: 5a 1H NMR (CDCl3, 300 MHz) d 7.79–7.75 (m, 2H) 7.46 (1H),
7.08–7.05 (m, 1H), 6.97–6.91(t, 1H), 5.91(s, 1H), 5.05 (1H, m) 4.79 (2H), 4.05
(1H), 3.77 (1H), 3.62 (4H), 3.26 (2H), 3.11 (2H), 2.29 (s, 2H); 5b 1H NMR (CDCl3,
300 MHz) d 7.79–7.75 (2H) 7.45–7.4 (dd, 1H), 7.07–7.04 (dd, 1H), 6.94–6.88 (t,
1H), 6.15 (1H), 5.72 (s, 1H), 4.77–4.75 (m, 1H), 4.20–4.13 (m, 2H), 4.04–3.98
14. CYP450 remaining test was conducted using VividÒ CYP450 Screening Kits
Protocol (Invitrogen).
15. hERG assay for cardiac toxicity test was conducted using an automated patch
clamp device, NPC-16 Patchliner (Nanion Technologies, Munchen, Germany)
following reference Farre, C.; Haythornthwaite, A.; Haarmann, C.; Stoelzle, S.;
Kreir, M.; George, M.; Bruggemann, A.; Fertig, N. Pharmacol. Comb. Chem. High
Throughput Screen. 2009, 12, 24.
16. MAO enzyme assay was conducted using Amplex TM Red monoamine oxidase
kit (A-12214) produced by Molecular Probe Inc. (a) Anal. Biochem. 1997 253,
162; (b) Methods Enzymol. 1987, 142, 617