Synthesis and antibacterial activity of novel lincomycin derivatives. II. Exploring (7S)-7-(5-aryl-1,3,4-thiadiazol-2-yl-thio)-7-deoxylincomycin derivatives

Article abstract of DOI:10.1038/ja.2016.139

The synthesis and antibacterial activity of (7S)-7-(5-aryl-1,3,4-thiadiazol-2-yl-thio)-7-deoxylincomycin derivatives are described. These derivatives were mainly prepared by the Mitsunobu reaction of 2,3,4-tris-O-(trimethylsilyl)lincomycin and the corresponding thiols. Exploring structure-activity relationships of the substituent at the 5 position of a thiadiazole ring revealed that compounds with the ortho substituted phenyl group showed improved antibacterial activities against Streptococcus pneumoniae and Streptococcus pyogenes with erm gene compared with the reported compound (1) that had an unsubstituted benzene ring.

Full text of DOI:10.1038/ja.2016.139

The Journal of Antibiotics (2016), 1–9
2016 Japan Antibiotics Research Association All rights reserved 0021-8820/16
www.nature.com/ja
&
ORIGINAL ARTICLE
Synthesis and antibacterial activity of
novel lincomycin derivatives. II. Exploring
(7S)-7-(5-aryl-1,3,4-thiadiazol-2-yl-thio)-7-
deoxylincomycin derivatives
Ko Kumura, Yoshinari Wakiyama, Kazutaka Ueda, Eijiro Umemura, Takashi Watanabe, Megumi Kumura,
Takuji Yoshida and Keiichi Ajito
The synthesis and antibacterial activity of (7S)-7-(5-aryl-1,3,4-thiadiazol-2-yl-thio)-7-deoxylincomycin derivatives are described.
These derivatives were mainly prepared by the Mitsunobu reaction of 2,3,4-tris-O-(trimethylsilyl)lincomycin and the
corresponding thiols. Exploring structure–activity relationships of the substituent at the 5 position of a thiadiazole ring revealed
that compounds with the ortho substituted phenyl group showed improved antibacterial activities against Streptococcus
pneumoniae and Streptococcus pyogenes with erm gene compared with the reported compound (1) that had an unsubstituted
benzene ring.
The Journal of Antibiotics advance online publication, 7 December 2016; doi:10.1038/ja.2016.139
INTRODUCTION
is effective against resistant S. pneumoniae and S. pyogenes with erm
Lincomycin1 is a secondary metabolite of Streptomyces lincolnensis and and mef genes, we started chemical modification of lincomycin and
active mainly against Gram positive bacteria. Clindamycin2 (CLDM)
clarified that (7S)-7-arylthio-7-deoxylincomycin derivatives9–11 and
derived from lincomycin is a useful semisynthetic antibiotic that is (7S)-7-(azetidin-3-yl-thio)-7-deoxylincomycin derivatives12 exhibited
most widely used in the lincosamide class (Figure 1). Lincosamide moderate to strong antibacterial activities against S. pneumoniae and
antibiotics are protein synthesis inhibitors3 that act on 50S ribosome
in a similar way to macrolide antibiotics such as clarithromycin.4
S. pyogenes with erm gene. In this article, we report optimization
of previously reported (7S)-7-deoxy-7-(5-phenyl-1,3,4-thiadi-
azol-2-yl-thio)lincomycin (1). On the other hand, telithromycin13 is
However, CLDM shows almost no antibacterial activity against
resistant pathogens such as Streptococcus pneumoniae and Streptococcus
pyogenes with erm gene as shown in Table 1. Moreover, major
macrolides, clarithromycin and azithromycin,5 are also not active
against those pathogens with erm gene. Erm methyltransferases
methylate A2058Ec of rRNA and diminish the affinity of clinically
important macrolides, lincosamides and streptogramin B3, and this
mode of resistance is referred to as MLS resistance.6 Increased
emergence of resistant bacteria has been causing serious problems at
clinical sites.7 CLDM is attractive because of its safety and effectiveness
against resistant pathogens with efflux pump. It is known that the
antibacterial activities of macrolide antibiotics are influenced by efflux
effective enough against S. pneumoniae with erm gene, but it has been
reported to have potential to cause side effects in clinical use.7
Novel azalides14 were generated starting from 16-membered macro-
lides, and several optimized 16-membered azalides15 are effective
against resistant S. pneumoniae and S. pyogenes with erm gene.
These analogs, however, are still under research process and have
not been developed yet. Currently available oral drugs are not effective
enough against resistant bacteria with erm and mef genes causing
respiratory infections and have some problems in safety or taste in
clinical site.
pumps of resistant S. pneumoniae and S. pyogenes with mef gene Chemistry
(Figure 1; Table 1). Furthermore, CLDM can be administered as oral Schemes 1 and 2 show the synthetic routes for novel (7S)-7-
and injectable agents. As a rare case, moreover, it has been reported (5-aryl-1,3,4-thiadiazol-2-yl-thio)-7-deoxylincomycin derivatives. We
that CLDM is effective for invasive group A streptococcal infections utilized reported 2, 3, 4-tris-O-(trimethylsilyl)lincomycin (2)16 as a
caused by S. pyogenes.8 According to these reasons, we selected substrate for the Mitsunobu reaction with various thiols as we
lincosamide (not macrolide) as a starting material for medicinal reported earlier.10 After the Mitsunobu reaction, trimethylsilyl groups
chemistry. In order to generate a novel chemotherapeutic agent that were removed by acid treatment to give 3–22 (Scheme 1). Although
Pharmaceutical Research Center, Meiji Seika Pharma Co., Ltd., Yokohama, Japan
Correspondence: Dr K Ajito, Pharmaceutical Research Center, Meiji Seika Pharma Co., Ltd., 760 Morooka-cho, Kohoku-ku, Yokohama 222-8567, Japan.
E-mail: keiichi.ajito@meiji.com
This paper is dedicated to Professor Dr. Satoshi Ōmura for his Nobel Prize in Physiology or Medicine 2015.
Received 11 August 2016; revised 25 September 2016; accepted 23 October 2016

Synthesis of novel lincomycin derivatives
K Kumura et al
2
Me
N
Me
O
O
HN
HO
Me
7
Me
HO
Me
Me
OMe
Me
Me
Me
OH
Me
R
O
N
6
HO
Me
Me
OH
Me
OH
Me
NMe2
Me
NMe2
Me
SMe
HO
HO
O
O
O
O
O
O
Me
Me
HO
OH
O
O
O
O
OMe
Me
OMe
Me
Me
Me
Me
Me
Lincomycin (LCM): R =
Clindamycin (CLDM): R =
OH
Cl
OH
OH
O
O
N
N
1: R =
S
Clarithromycin (CAM)
Azithromycin (AZM)
S
Figure 1 Structures of clinically important macrolides, lincomycin, clindamycin and compound 1.
Table 1 Antibacterial activities of CAM, AZM, LCM, CLDM and compound 1 (MIC; μg ml− 1 a
)
No.
Test organismb
Characteristics
CAM
AZM
LCM
CLDM
1
1
Streptococcus pneumoniae DP1 type I
S. pneumoniae #2
Susceptible
0.03
0.03
0.015
4128
4128
4128
4128
4128
0.5
0.06
0.03
0.03
4128
4128
4128
4128
4128
0.5
1
1
0.13
0.13
0.13
4128
4128
4128
4128
4128
0.13
0.13
0.13
4128
0.13
8
0.13
0.06
0.06
64
2
Susceptible
3
S. pneumoniae #3
Susceptible
0.25
4128
4128
4128
128
128
1
4
S. pneumoniae #4
ermB methylase (c)
ermB methylase (c)
ermB methylase (c)+mefE
ermB methylase (i)
ermB methylase (i)
mefE efflux
5
S. pneumoniae #5
32
6
S. pneumoniae #6
128
16
7
S. pneumoniae #7
8
S. pneumoniae #8
16
9
S. pneumoniae #9
0.06
0.06
0.06
4
10
11
12
13
14
15
16
S. pneumoniae #10
Streptococcus pyogenes Cook
S. pyogenes #2
mefE efflux
0.5
0.5
1
Susceptible
0.015
4128
8
0.06
4128
8
0.13
4128
0.25
8
ermB methylase (c)
mefE efflux
S. pyogenes #3
0.13
16
Haemophilus influenzae #1
H. influenzae #2
Susceptible
2
0.25
1
Susceptible
4
16
8
16
H. influenzae #3
Susceptible
8
2
16
32
64
Abbreviations: AZM, azithromycin; c, constitutive; CAM, clarithromycin; CLDM, clindamycin; i, inducible; LCM, lincomycin; MIC, minimum inhibitory concentration.
aGray shading strains are target strains.
bAll strains except standard organisms were clinically isolated.
N
R
N
S
Me
Me
S
O
HN
HO
Me
7
O
Me
7
OH
O
a, b
N
N
HN
Me
Me
O
SMe
S
TMSO
TMSO
SMe
HO
3-22
OH
OTMS
2
N
N
N
5: R =
6: R =
3: R =
8: R =
7: R =
4: R =
O2N
O2N
NO2
Me
O
N
N
NO2
12: R =
9: R =
10: R =
11: R =
Me
HN
O2N
H2N
H2N
Cl
Me
N
N
N
16: R =
Me
21: R =
17: R =
13: R =
18: R =
14: R =
19: R =
15: R =
MeS
N
N
N
Me
O
S
O
Me
MeO
NC
20: R =
22: R =
Scheme 1 Synthesis of (7S)-7-(5-aryl-1,3,4-thiadiazol-2-yl-thio)-7-deoxylincomycin derivatives. Reagents: (a) ArSH, diethyl azodicarboxylate (DEAD), PPh3
and tetrahydrofuran; (b) 1 N HCl and MeOH.
The Journal of Antibiotics

Synthesis of novel lincomycin derivatives
K Kumura et al
3
N
N
N
S
S
Me
Me
O
Me
7
O
HN
HO
Me
7
NH2
OMs
O
N
N
HN
a, b
Me
Me
O
TMSO
SMe
SMe
TMSO
OTMS
HO
OH
24
23
c, d, e
N
N
N
S
N
S
Me
Me
Me
S
S
O
Me
7
O
HN
HO
Me
7
O
HN
HO
Me
CO2Me
CONR2
SH
O
N
N
N
HN
HO
g, h
f
Me
Me
Me
O
O
SMe
SMe
SMe
HO
OH
HO
26
OH
HO
OH
27: R = H
28: R= Me
25
N
N
R
S
R
N
S
N
S
Me
Me
S
O
HN
HO
Me
O Me
N
N
i
HN
HO
Me
Me
O
O
SMe
SMe
HO
OH
HO
OH
9: R = o-NO2Ph
10: R = m-NO2Ph
11: R = p-NO2Ph
29: R = o-NH2Ph
30: R = m-NH2Ph
31: R = p-NH2Ph
Scheme 2 Synthesis of (7S)-7-(5-aryl-1,3,4-thiadiazol-2-yl-thio)-7-deoxylincomycin derivatives. Reagents: (a) 5-(2-aminopyridin-3-yl)-1,3,4-thiadiazole-2-thiol,
K2CO3 and DMF; (b) 1 N HCl and MeOH; (c) KSAc and DMF; (d) 2 N HCl and MeOH; (e) NaOMe and MeOH; (f) methyl 2-(5-chloro-1,3,4-thiadiazol-2-yl)
benzoate, NaHMDS and DMF; (g) 2 N NaOH and MeOH; (h) NH3 for 27, HNMe2 for 28, WSC, HOBt and DMF; (i) SnCl2, NaBH4 and EtOH.
the Mitsunobu reaction is robust, 5-(2-aminopyridin-3-yl)-1,3, gene. On the basis of the results obtained in the above, we performed
4-thiadiazole-2-thiol (a side chain thiol of 24) did not give a desired further optimization focusing on substituents on the benzene ring.
To determine the optimal site of a substituent on the phenyl group,
we investigated compounds having a nitro group or an amino group
as shown in Table 3. As a matter of fact, compounds having a nitro or
an amino group at the ortho position (compounds 9 and 29) exhibited
clearly enhanced antibacterial activities against S. pneumoniae with erm
gene. Similarly, compounds with those groups at the meta position
improved the activities (compounds 10 and 30) but the enhancement
effect of the meta substitution seemed to be less than that of the ortho
substitution. Antibacterial activities of compounds with a para
substituted phenyl group were comparable to those of compound 1
against S. pneumoniae with erm gene but stronger than those of
compound 1 against S. pneumoniae with mef gene. On the other hand,
the position of a substituent did not significantly affect antibacterial
activities against S. pyogenes.
Our finding concerning the ortho substitution at the benzene ring
encouraged us to replace the benzene ring with other hetero aromatic
rings. Antibacterial activities of compounds having a pyrazole, a
pyridine or a pyrazine ring with a nitro or an amino group are shown
in Table 4. Although compound 14 showed improved antibacterial
activities against S. pneumoniae with erm gene, its antibacterial
activities were limited.
condensation product. In this case, the thiol was reacted with (7R)-
7-O-methanesulfonyllincomycin (23)10–12 in a basic condition to give
24 after an acid treatment (Scheme 2). Compounds 27 and 28 were
synthesized by an SNAr reaction of (7S)-7-deoxy-7-mercaptolinco-
myicn (25)11 and methyl 2-(5-chloro-1,3,4-thiadiazol-2-yl)benzoate
followed by hydrolysis of methyl ester (26) and condensation of the
corresponding amines. A nitro group of compounds 9, 10 and 11 were
converted to an amino group by stannous chloride and sodium
borohydride to give compounds 29, 30 and 31, respectively.
RESULTS AND DISCUSSION
We reported that compound 1 exhibited weak antibacterial activities
against S. pneumoniae and S. pyogenes with erm gene, although CLDM
did not show any activities against those pathogens.10 To enhance the
antibacterial activities of compound 1, we first changed the benzene
ring of compound 1 to other aryl and hetero aryl groups as shown in
Table 2. Compound 3 having a 2-naphtyl group showed weak
antibacterial activities against most of tested pathogens probably due
to bulkiness of the substituent based on our three-dimensional
analysis.11 As for pyridine analogs, antibacterial activities of
compounds 4 and 5 against erm-resistant S. pneumoniae were
comparable to those of compound 1, but compound 6 having a
We finally examined other substituents on the benzene ring instead
4-pyridyl group showed decreased activities against those pathogens. of a nitro or an amino group as shown in Table 5. Compounds 16, 18
Compounds 7 and 8 possessing a thienyl group or a furanyl group and 19 have an electron donating group at the ortho position of the
showed comparable antibacterial activities against S. pneumoniae to benzene ring. Among them, compound 16 exhibited comparable
compound 1, but decreased activities against S. pyogenes with erm antibacterial activities to compounds 9 and 29 against S. pneumoniae
The Journal of Antibiotics

Synthesis of novel lincomycin derivatives
K Kumura et al
4
Table 2 Antibacterial activities of novel lincomycin derivatives (MIC; μg ml− 1 a
)
Abbreviations: c, constitutive; CLDM, clindamycin; i, inducible; MIC, minimum inhibitory concentration.
aAll antibacterial evaluations were performed as hydrochloride. Gray shading strains are target strains.
bAll strains except standard organisms were clinically isolated.
and S. pyogenes with erm gene. Among the compounds with an graphy was performed with silica gel 60N (Kanto Chemical, Tokyo, Japan;
spherical, neutral).
electron withdrawing group, compounds 27 and 22 showed compar-
able antibacterial activities against S. pneumoniae and S. pyogenes with
erm gene to compounds 9 and 29.
(7S)-7-Deoxy-7-[5-(2-naphtyl)-1,3,4-thiadiazol-2-ylthio]lincomycin (3)
To a solution of compound 2 (240 mg, 0.39 mmol) in tetrahydrofuran (5 ml)
at 0 °C were added triphenylphosphine (160 mg, 0.61 mmol) and diethylazo-
dicarboxylate (0.1 ml, 0.55 mmol) and stirred at 0 °C for 30 min, and
5-(naphthalen-2-yl)-1,3,4-thiadiazole-2-thiol (130 mg, 0.53 mmol) was added
and stirred overnight at room temperature. The mixture was concentrated
in vacuo and added MeOH (5 ml), 1 N HCl (0.5 ml) and stirred at room
temperature for 30 min and concentrated in vacuo. The resulting residue was
dissolved in water and washed with diethyl ether. To the mixture was added
NaHCO3, and the mixture was extracted with ethyl acetate. The organic phase
was washed with water, dried over MgSO4, filtered and concentrated in vacuo.
The resulting residue was purified by preparative thin-layer chromatography
(CHCl3/CH3OH/28% aq NH4OH= 20/1/0.1) to afford 3 (22.3 mg, 9%)
CONCLUSIONS
In summary, we identified compounds 9, 16, 22, 27 and 29, which
exhibited improved antibacterial activities against S. pneumoniae
and S. pyogenes with erm gene by chemical modification of (7S)-
7-deoxy-7-(5-phenyl-1,3,4-thiadiazol-2-yl-thio)lincomycin (1). These
results indicate that a (7S)-7-deoxy-7-[5-(ortho-substituted-phenyl)-
1,3,4-thiadiazol-2-yl-thio]lincomycin analog is a promising framework
to overcome resistant S. pneumoniae and S. pyogenes. Further
structural optimizations are in progress.
as colorless solid. [α]D +64° (c 0.79, CHCl3); 1H NMR (300 MHz, CDCl3)
27
EXPERIMENTAL PROCEDURE
δ 9.03 (d, J = 8.8 Hz, 1H), 8.31 (s, 1H), 8.04–8.08 (m, 1H), 7.87–8.02 (m, 3H),
7.56–7.64 (m, 2H), 5.37 (d, J = 5.8 Hz, 1H), 3.99–4.48 (m, 1H), 4.31–4.37
(m, 1H), 4.28 (d, J = 10.4 Hz, 1H), 4.16 (dd, J = 9.9, 6.0 Hz, 1H), 3.68–3.74
(m, 1H), 3.54–3.64 (m, 1H), 3.42 (dd, J = 7.7, 5.5 Hz, 1H), 3.11 (dd, J = 9.9,
4.7 Hz, 1H), 2.41 (s, 3H), 2.19 (s, 3H), 2.06–2.18 (m, 2H), 1.86–2.02 (m, 2H),
1.58 (d, J = 6.9 Hz, 1H), 1.24–1.42 (m, 4H) and 0.86–0.99 (m, 3H); MS (FAB)
m/z 633 (M+H)+; HRMS (ESI) m/z calcd for C30H41N4O5S3 633.2234, found
633.2235 (M+H)+.
General
1H nuclear magnetic resonance (NMR) spectra were measured with Varian
Gemini-300 (Varian, Palo Alto, CA, USA) for 300 MHz, JEOL JNM-GSX 400
(JEOL, Tokyo, Japan) for 400 MHz or BRUKER Ascend 400 NMR spectro-
meter (BRUKER Corporation, Coventry, UK) for 400 MHz in CDCl3 or
CD3OD with 0.03% tetramethylsilane as an internal standard. 13C NMR spectra
were measured with BRUKER Ascend 400 NMR spectrometer (BRUKER
Corporation) for 100 MHz. Mass spectra were obtained on
a JEOL
JMS-FABmate spectrometer or JEOL JMS-700 mass spectrometer or Agilent
Technologies 6530-Q-TOF LC/MS mass spectrometer (Agilent Technologies,
Santa Clara, CA, USA). The optical rotations were recorded with Jasco P-2300
digital polarimeter (Jasco, Tokyo, Japan). The melting points were measured
(7S)-7-Deoxy-7-[5-(2-pyridyl)-1,3,4-thiadiazol-2-ylthio]lincomycin (4)
Reaction of 2 (240 mg, 0.39 mmol) with 5-(pyridin-2-yl)-1,3,4-thiadiazole-
2-thiol (100 mg, 0.51 mmol) gave 4 as a colorless solid in 11% yield by a similar
27
with Yanaco MP-S (Yanaco, Tokyo, Japan). The infrared (IR) spectra were procedure to 3. [α]D +140° (c 1.2, CHCl3); 1H NMR (300 MHz, CDCl3)
measured with Jasco FT/IR-410 (Jasco, Tokyo, Japan). Column chromato- δ 8.93 (d, J = 9.1 Hz, 1H), 8.63–8.67 (m, 1H), 8.28 (d, J = 8.0 Hz, 1H),
The Journal of Antibiotics

Synthesis of novel lincomycin derivatives
K Kumura et al
5
Table 3 Antibacterial activities of novel lincomycin derivatives (MIC; μg ml− 1 a
)
Abbreviations: c, constitutive; i, inducible; MIC, minimum inhibitory concentration.
aAll antibacterial evaluations were performed as hydrochloride. Gray shading strains are target strains.
bAll strains except standard organisms were clinically isolated.
7.84–7.91 (m, 1H), 7.38–7.44 (m, 1H), 5.36 (d, J = 5.5 Hz, 1H), 5.29 (m, 1H), (7S)-7-Deoxy-7-[5-(2-thienyl)-1,3,4-thiadiazol-2-ylthio]lincomycin (7)
4.32–4.47 (m, 2H), 4.25 (d, J = 9.9 Hz, 1H), 4.10–4.19 (m, 1H), 3.69–3.74
(m, 1H), 3.55–3.64 (m, 1H), 3.34–3.41 (m, 1H), 3.10 (dd, J = 10.3, 4.8 Hz, 1H),
2.71–2.79 (m, 1H), 2.41 (s, 3H), 2.15 (s, 3H), 2.06–2.14 (m, 2H), 1.88–2.00
(m, 2H), 1.57 (d, J = 6.9 Hz, 3H), 1.28–1.41 (m, 4H) and 0.88–0.97 (m, 3H);
MS (FAB) m/z 584 (M+H)+; HRMS (ESI) m/z calcd for C25H38N5O5S3
584.2030, found 584.2032 (M+H)+.
Reaction of 2 (240 mg, 0.39 mmol) with 5-(thiophen-2-yl)-1,3,4-thiadiazole-
2-thiol (100 mg, 0.50 mmol) gave 7 as a colorless solid in 17% yield by a similar
procedure to 3. [α]D30 +90° (c 1.1, CHCl3); 1H NMR (300 MHz, CDCl3) δ 8.96
(d, J =8.8 Hz, 1H), 7.48–7.54 (m, 2H), 7.11–7.16 (m, 1H), 5.34 (d, J = 5.5 Hz,
1H), 5.31 (br s, 1H), 4.36–4.46 (m, 1H), 4.22–4.33 (m, 2H), 4.15 (dd, J = 10.0,
5.5 Hz, 1H), 3.68–3.74 (m, 1H), 3.58 (dd, J =10.0, 3.4 Hz, 1H), 3.38 (dd,
J = 7.7, 5.5 Hz, 1H), 3.07 (dd, J =10.2, 4.9 Hz, 1H), 2.37 (s, 3H), 2.17 (s, 3H),
1.86–2.15 (m, 4H), 1.53 (d, J = 6.9 Hz, 3H), 1.28–1.39 (m, 4H) and 0.86–0.96
(m, 3H); MS (FAB) m/z 589 (M+H)+; HRMS (ESI) m/z calcd for
C24H37N4O5S4 589.1641, found 589.1646 (M+H)+.
(7S)-7-Deoxy-7-[5-(3-pyridyl)-1,3,4-thiadiazol-2-ylthio]lincomycin (5)
Reaction of 2 (240 mg, 0.39 mmol) with 5-(pyridin-3-yl)-1,3,4-thiadiazole-
2-thiol (100 mg, 0.51 mmol) gave 5 as a colorless solid in 37% yield by a similar
procedure to 3. [α]D +105° (c 1.0, CHCl3); 1H NMR (300 MHz, CDCl3)
27
δ 9.09 (s, 1H), 9.05 (d, J = 8.0 Hz, 1H), 8.72–8.78 (m, 1H), 8.24 (d, J = 8.2 Hz,
1H), 7.42–7.51 (m, 1H), 5.36 (d, J = 5.8 Hz, 1H), 5.31 (br s, 1H), 4.31–4.50
(m, 2H), 4.24 (d, J = 9.9 Hz, 1H), 4.09–4.19 (m, 2H), 3.69–3.75 (m, 1H),
3.51–3.61 (m, 1H), 3.36–3.44 (m, 1H), 3.07–3.14 (m, 1H), 2.41 (s, 3H), 2.18
(s, 3H), 2.04–2.16 (m, 2H), 1.84–2.02 (m, 2H), 1.57 (d, J = 6.9 Hz, 3H),
1.28–1.38 (m, 4H) and 0.87–0.96 (m, 3H); MS (FAB) m/z 584 (M+H)+;
HRMS (ESI) m/z calcd for C25H38N5O5S3 584.2030, found 584.2027 (M+H)+.
(7S)-7-Deoxy-7-[5-(2-furanyl)-1,3,4-thiadiazol-2-ylthio]lincomycin
(8)
Reaction of 2 (240 mg, 0.39 mmol) with 5-(furan-2-yl)-1,3,4-thiadiazole-2-
thiol (100 mg, 0.54 mmol) gave 8 as a colorless solid in 38% yield by a similar
procedure to 3. [α]D30 +88° (c 1.4, CHCl3); 1H NMR (300 MHz, CDCl3) δ 8.79
(d, J = 8.5 Hz, 1H), 7.58–7.62 (m, 1H), 7.13–7.17 (m, 1H), 6.57–6.63 (m, 1H),
5.34 (d, J = 5.5 Hz, 1H), 5.26 (br s, 1H), 4.35–4.44 (m, 1H), 4.31 (qd, J = 6.9,
3.3 Hz, 1H), 4.24 (d, J = 10.2 Hz, 1H), 4.11–4.21 (m, 2H), 3.67–3.74 (m, 1H),
3.53–3.64 (m, 2H), 3.47 (s, 1H), 3.29–3.39 (m, 1H), 3.06 (dd, J = 10.0, 4.5 Hz,
1H), 2.36 (s, 3H), 2.14 (s, 3H), 2.02–2.11 (m, 2H), 185–1.99 (m, 2H), 1.51
(d, J = 6.9 Hz, 3H), 1.11–1.40 (m, 4H) and 0.82–0.97 (m, 3H); MS (FAB) m/z
573 (M+H)+; HRMS (ESI) m/z calcd for C24H37N4O6S3 573.1870, found
573.1870 (M+H)+.
(7S)-7-Deoxy-7-[5-(4-pyridyl)-1,3,4-thiadiazol-2-ylthio]lincomycin (6)
Reaction of 2 (240 mg, 0.39 mmol) with 5-(pyridin-4-yl)-1,3,4-thiadiazole-
2-thiol (100 mg, 0.51 mmol) gave 6 as a colorless solid in 48% yield by a similar
procedure to 3. [α]D +124° (c 1.0, CHCl3); 1H NMR (300 MHz, CDCl3)
27
δ 9.03 (d, J = 8.8 Hz, 1H), 8.75–8.82 (m, 2H), 7.73–7.79 (m, 2H), 5.36
(d, J =5.5 Hz, 1H), 5.27 (br s, 1H), 4.44–4.54 (m, 1H), 4.39 (qd, J = 6.9, 3.3 Hz,
1H), 4.25 (d, J = 10.2 Hz, 1H), 4.17 (dd, J = 10.2, 5.5 Hz, 1H), 3.77 (br s, 1H),
3.59 (dd, J = 10.2, 3.0 Hz, 1H), 3.43–3.50 (br s 1H), 2.51 (br s, 3H), 2.16–2.29
(m, 2H), 2.15 (s, 3H), 1.89–2.09 (m, 2H), 1.57 (d, J = 6.9 Hz, 3H), 1.24–1.43
(m, 4H) and 0.87–0.96 (m, 3H); MS (FAB) m/z 584 (M+H)+; HRMS (ESI) m/z
calcd for C25H38N5O5S3 584.2030, found 584.2032 (M+H)+.
(7S)-7-Deoxy-7-[5-(2-nitrophenyl)-1,3,4-thiadiazol-2-ylthio]
lincomycin (9)
Reaction of 2 (320 mg, 0.51 mmol) with 5-(2-nitrophenyl)-1,3,4-thiadiazole-2-
thiol (160 mg, 0.67 mmol) gave 9 as a colorless solid in 54% yield by a similar
The Journal of Antibiotics

Synthesis of novel lincomycin derivatives
K Kumura et al
6
Table 4 Antibacterial activities of novel lincomycin derivatives (MIC; μg ml− 1 a
)
Abbreviations: c, constitutive; i, inducible; MIC, minimum inhibitory concentration; ND, not determined.
aAll antibacterial evaluations were performed as hydrochloride. Gray shading strains are target strains.
bAll strains except standard organisms were clinically isolated.
30
procedure to 3. mp 235–240 °C (decomp.); [α]D +91° (c 0.52, CHCl3); IR (7S)-7-Deoxy-7-[5-(4-nitrophenyl)-1,3,4-thiadiazol-2-ylthio]
(KBr) 3399, 2922, 1654 and 1533 cm− 1 1H NMR (300 MHz, CDCl3) δ 9.10
;
lincomycin (11)
(d, J =8.0 Hz, 1H), 7.68–7.79 (m, 1H), 7.68–7.79 (m, 3H), 5.36 (d, J = 5.5 Hz,
1H), 4.39–4.49 (m, 1H), 4.20–4.38 (m, 2H), 4.15 (dd, J =9.9, 5.5 Hz, 1H), 3.71
(br s, 1H), 3.53–3.61 (m, 1H), 3.31–3.38 (m, 1H), 3.09 (dd, J = 10.3, 4.8 Hz,
1H), 2.40 (s, 3H), 2.19 (s, 3H), 2.03–2.16 (m, 4H), 1.57 (d, J = 7.1 Hz, 3H),
1.24–1.40 (m, 4H) and 0.86–0.96 (m, 3H); 13C NMR (100 MHz, CDCl3)
δ 179.1, 164.9, 163.5, 148.5, 132.9, 132.0, 131.6, 124.9, 123.8, 89.1, 71.8, 71.0,
69.2, 68.4, 68.2, 62.5, 53.0, 44.9, 41.7, 38.1, 37.9, 35.7, 21.5, 18.5, 14.8 and 14.2;
MS (FAB) m/z 628 (M+H)+; HRMS (ESI) m/z calcd for C26H38N5O7S3
628.1928, found 628.1934 (M+H)+.
Reaction of 2 (240 mg, 0.39 mmol) with 5-(4-nitrophenyl)-1,3,4-thiadiazole-
2-thiol (120 mg, 0.50 mmol) gave 11 as a colorless solid in 33% yield by a
similar procedure to 3. [α]D +67° (c 0.81, CHCl3); 1H NMR (300 MHz,
30
CDCl3) δ 8.92 (d, J = 9.1 Hz, 1H), 8.35 (d, J = 8.5 Hz, 2H), 8.08 (d, J = 8.5 Hz,
2H), 5.34 (d, J = 5.5 Hz, 1H), 4.34–4.51 (m, 2H), 4.22 (d, J = 9.9 Hz, 1H), 4.16
(dd, J =10.3, 5.6 Hz, 1H), 3.72 (d, J = 3.0 Hz, 1H), 3.58 (dd, J = 10.0, 3.3 Hz,
1H), 3.33–3.39 (m, 1H), 3.11 (dd, J = 10.0, 4.5 Hz, 1H), 2.41 (s, 3H), 2.14
(s, 3H), 2.06–2.12 (m, 2H), 1.86–2.04 (m, 2H), 1.57 (d, J = 6.9 Hz, 3H),
1.23–1.38 (m, 4H) and 0.85–0.94 (m, 3H); MS (FAB) m/z 628 (M+H)+; HRMS
(ESI) m/z calcd for C26H38N5O7S3 628.1928, found 628.1927 (M+H)+.
(7S)-7-Deoxy-7-[5-(3-nitrophenyl)-1,3,4-thiadiazol-2-ylthio]
(7S)-7-Deoxy-7-[5-(1-methyl-5-nitro-1H-pyrazol-4-yl)-1,3,4-
lincomycin (10)
Reaction of 2 (320 mg, 0.51 mmol) with 5-(3-nitrophenyl)-1,3,4-thiadiazole- thiadiazol-2-ylthio]lincomycin (12)
2-thiol (160 mg, 0.67 mmol) gave 10 as a colorless solid in 41% yield by a Reaction of 2 (280 mg, 0.45 mmol) with 5-(1-methyl-5-nitro-1H-pyrazol-4-yl)-
30
similar procedure to 3. [α]D +85° (c 1.1, CHCl3); 1H NMR (300 MHz,
1,3,4-thiadiazole-2-thiol (120 mg, 0.49 mmol) gave 12 as a colorless solid in
35% yield by a similar procedure to 3. [α]D +51° (c 1.1, CHCl3); 1H NMR
31
CDCl3) δ 9.02 (d, J = 9.1 Hz, 1H), 8.07–8.75 (m, 1H), 8.35–8.42 (m, 1H),
8.24–8.29 (m, 1H), 7.73 (t, J = 8.0 Hz, 1H), 5.36 (d, J = 5.2 Hz, 1H), 5.31 (300 MHz, CDCl3) δ 8.89 (d, J = 8.8 Hz, 1H), 5.34 (d, J = 5.5 Hz, 1H), 5.27
(br s, 1H), 4.34–4.52 (m, 2H), 4.23 (d, J = 10.2 Hz, 1H), 4.15 (dd, J = 10.0, (br s, 1H), 4.37–4.48 (m, 2H), 4.23 (d, J = 10.4 Hz, 1H), 4.14 (dd, J = 10.0,
5.4 Hz, 1H), 3.69–3.75 (m, 1H), 3.57 (dd, J = 9.9, 3.0 Hz, 1H), 3.36–3.44 5.5 Hz, 1H), 4.08 (s, 3H), 3.70 (br s, 1H), 3.53–3.62 (m, 1H), 3.32–3.40
(m, 1H), 3.11 (dd, J = 10.0, 4.8 Hz, 1H), 2.43 (s, 3H), 2.18 (s, 3H), 2.08–2.17 (m, 1H), 3.09 (dd, J = 10.3, 4.8 Hz, 1H), 2.40 (s, 3H), 2.17 (s, 3H), 1.85–2.15
(m, 2H), 1.90–2.03 (m, 2H), 1.58 (d, J = 6.9 Hz, 3H), 1.24–1.44 (m, 4H) and (m, 4H), 1.55 (d, J = 6.9 Hz, 1H), 1.25–1.39 (m, 4H) and 0.85–0.96 (m, 3H);
0.88–0.99 (m, 3H); MS (FAB) m/z 628 (M+H)+; HRMS (ESI) m/z calcd for MS (FAB) m/z 632 (M+H)+; HRMS (ESI) m/z calcd for C24H38N7O7S3
C26H38N5O7S3 628.1928, found 628.1938 (M+H)+.
632.1989, found 632.1991 (M+H)+.
The Journal of Antibiotics

Synthesis of novel lincomycin derivatives
K Kumura et al
7
Table 5 Antibacterial activities of novel lincomycin derivatives (MIC; μg ml− 1 a
)
Abbreviations: c, constitutive; i, inducible; MIC, minimum inhibitory concentration; ND, not determined.
aAll antibacterial evaluations were performed as hydrochloride. Gray shading strains are target strains.
bAll strains except standard organisms were clinically isolated.
(7S)-7-Deoxy-7-[5-(1-methyl-4-nitro-1H-pyrazol-3-yl)-1,3,4-
thiadiazol-2-ylthio]lincomycin (13)
(d, J = 10.2 Hz, 1H), 4.17 (dd, J =10.5, 5.5 Hz, 1H), 3.67–3.75 (m, 1H), 3.60
(dd, J = 10.2, 3.3 Hz, 1H), 3.23–3.32 (m, 1H), 3.09 (dd, J =10.0, 4.5 Hz, 1H),
2.39 (s, 3H), 2.10 (s, 3H), 1.84 (m, 2H), 1.56 (d, J = 6.9 Hz, 3H), 1.20–1.40
(m, 4H) and 0.85–0.96 (m, 3H); MS (FAB) m/z 600 (M+H)+; HRMS (ESI)
m/z calcd for C24H38N7O5S3 600.2091, found 600.2092 (M+H)+.
Reaction of 2 (280 mg, 0.45 mmol) with 5-(1-methyl-4-nitro-1H-pyrazol-3-yl)-
1,3,4-thiadiazole-2-thiol (120 mg, 0.49 mmol) gave 13 as a colorless solid in
30
1
18% yield by a similar procedure to 3. [α]D +79° (c 0.52, CHCl3); H NMR
(300 MHz, CDCl3) δ 8.90 (d, J = 8.8 Hz, 1H), 8.33 (s, 1H), 5.35 (d, J = 5.5 Hz,
1H), 5.30 (br s, 1H), 4.37–4.49 (m, 2H), 4.23 (d, J = 10.4 Hz, 1H), 4.10–4.20
(m, 2H), 4.08 (s, 3H), 3.67–3.76 (m 2H), 3.52–3.63 (m, 2H), 3.49 (s, 1H),
3.29–3.44 (m, 2H), 3.09 (dd, J = 10.3, 4.3 Hz, 1H), 2.83–2.95 (m, 1H), 2.69
(d, J =7.7 Hz, 1H), 2.41 (s, 3H), 2.14 (s, 3H), 2.04–2.13 (m, 2H), 1.79–2.00
(m, 2H), 1.56 (d, J = 7.1 Hz, 3H), 1.27–1.38 (m, 4H) and 0.86–0.95 (m, 3H);
MS (FAB) m/z 632 (M+H)+; HRMS (ESI) m/z calcd for C24H38N7O7S3
632.1989, found 632.1982 (M+H)+.
(7S)-7-Deoxy-7-{5-[2-(methylamino)phenyl]-1,3,4-thiadiazol-2-
ylthio}lincomycin (16)
Reaction of 2 (160 mg, 0.26 mmol) with 5-[2-(methylamino)phenyl]-1,3,
4-thiadiazole-2-thiol (100 mg, 0.45 mmol) gave 16 as a colorless solid in 22%
yield by a similar procedure to 3. [α]D +55° (c 1.1, CHCl3); 1H NMR
31
(300 MHz, CDCl3) δ 8.85 (d, J = 9.1 Hz, 1H), 8.09–8.21 (m, 1 H), 7.27–7.45
(m, 2H), 6.63–6.85 (m, 2H), 5.35 (d, J =5.5 Hz, 1H), 5.26 (br s, 1H), 4.38–4.51
(m, 1H), 4.22–4.36 (m, 2H), 4.17 (dd, J = 9.9, 5.5 Hz, 1H), 3.68–3.77 (m, 1H),
3.60 (dd, J = 10.0, 3.4 Hz, 1H), 3.24–3.36 (m, 1H), 3.04–3.13 (m, 1H), 3.00
(d, J = 4.9 Hz, 3H), 2.38 (s, 3H), 2.14 (s, 3H), 1.88–2.12 (m, 4H), 1.54
(d, J = 6.9 Hz, 3H), 1.25–1.40 (m, 4H) and 0.85–0.97 (m, 3H); MS (FAB) m/z
(7S)-7-[5-(5-Amino-1-methyl-1H-pyrazol-4-yl)-1,3,4-thiadiazol-2-
ylthio]-7-deoxylincomycin (14)
Reaction of 2 (240 mg, 0.39 mmol) with 5-(5-amino-1-methyl-1H-pyrazol-
4-yl)-1,3,4-thiadiazole-2-thiol (115 mg, 0.54 mmol) gave 14 as a colorless solid
in 65% yield by a similar procedure to 3. [α]D30 +88° (c 1.0, CHCl3); 1H NMR 612 (M+H)+; HRMS (ESI) m/z calcd for C27H42N5O5S3 612.2343, found
612.2339 (M+H)+.
(300 MHz, CDCl3) δ 8.71 (d, J = 8.2 Hz, 1H), 7.46 (s, 1H), 5.38 (br s, 1H), 5.34
(d, J = 5.5 Hz, 1H), 5.23 (br s, 1H), 4.33–4.44 (m, 1H), 4.21–4.32 (m, 2H), 4.14
(dd, J = 10.0, 5.5 Hz, 1H), 3.70 (s, 3H), 3.55 (m, 1H), 3.26–3.33 (m, 1H),
3.07 (dd, J = 10.0, 4.5 Hz, 1H), 2.35 (s, 3H), 2.15 (s, 3H), 2.03–2.14 (m, 2H),
1.85–2.01 (m, 2H), 1.49 (d, J = 7.1 Hz, 3H), 1.25–1.38 (m, 4H) and 0.86–0.97
(m, 3H); MS (FAB) m/z 602 (M+H)+; HRMS (ESI) m/z calcd for
C24H40N7O5S3 602.2248, found 602.2243 (M+H)+.
(7S)-7-[5-(2-Chlorophenyl)-1,3,4-thiadiazol-2-ylthio]-7-
deoxylincomycin (17)
Reaction of 2 (240 mg, 0.39 mmol) with 5-(2-chlorophenyl)-1,3,4-thiadiazole-
2-thiol (100 mg, 0.44 mmol) gave 17 as a colorless solid in 34% yield by a
similar procedure to 3. [α]D +102° (c 1.0, CHCl3); 1H NMR (300 MHz,
30
CDCl3) δ 9.04 (d, J = 9.1 Hz, 1H), 8.25–8.33 (m, 1H), 7.37–7.60 (m, 3H), 5.35
(d, J = 5.5 Hz, 1H), 5.30 (br s, 1H), 4.21–4.44 (m, 5H), 3.66–3.75 (m, 1H),
3.51–3.64 (m, 2H), 3.30–3.43 (m, 1H), 3.29–3.39 (m, 1H), 3.09 (dd, J = 10.2,
4.7 Hz, 1H), 2.39 (s, 3H), 2.16 (s, 3H), 2.02–2.13 (m, 2H), 185–2.00 (m, 2H),
1.54 (d, J = 6.9 Hz, 3H), 1.19–1.42 (m, 4H) and 0.85–0.98 (m, 3H); MS (FAB)
m/z 617 (M+H)+; HRMS (ESI) m/z calcd for C26H38ClN4O5S3 617.1687, found
(7S)-7-[5-(3-Aminopyrazin-2-yl)-1,3,4-thiadiazol-2-ylthio]-7-
deoxylincomycin (15)
Reaction of 2 (240 mg, 0.39 mmol) with 5-(3-aminopyrazin-2-yl)-1,3,4-thia-
diazole-2-thiol (140 mg, 0.66 mmol) gave 15 as a colorless solid in 59% yield by
a similar procedure to 3. [α]D +62° (c 1.0, CHCl3); 1H NMR (300 MHz,
30
CDCl3) δ 8.74 (d, J = 8.8 Hz, 1H), 8.11 (d, J =2.4 Hz, 1H), 7.94 (d, J = 2.4 Hz,
1H), 5.34 (d, J =5.5 Hz, 1H), 5.20 (br s, 1H), 4.33–4.52 (m, 2H), 4.22 617.1691 (M+H)+.
The Journal of Antibiotics

Synthesis of novel lincomycin derivatives
K Kumura et al
8
(7S)-7-Deoxy 7-[5-(o-tolyl)-1,3,4-thiadiazol-2-ylthio]lincomycin
(18)
(td, J = 7.8, 1.4 Hz, 1H), 7.52–7.60 (m, 1H), 5.27 (d, J = 5.8 Hz, 1H), 4.22–4.44
(m, 2H), 4.15 (d, J = 9.6 Hz, 1H), 4.07 (dd, J = 9.9, 5.5 Hz, 1H), 3.61–3.68
(m, 1H), 3.44–3.56 (m, 1H), 3.31–3.39 (m, 1H), 2.99–3.09 (m, 1H), 2.36–2.47
(m, 3H), 2.25–2.36 (m, 1H), 2.11 (s, 3H), 1.80–2.09 (m, 4H), 1.43–1.58
(m, 3H) and 1.16–1.31 (m, 5H); 13C NMR (100 MHz, CDCl3) δ 185.8, 177.7,
153.9, 134.7, 133.3, 131.6, 131.1, 129.6, 117.1, 110.7, 90.9, 70.9, 70.3, 69.2, 68.5,
67.9, 63.0, 54.4, 51.4, 42.1, 37.7, 37.6, 35.8, 21.6, 15.8, 15.2 and 14.2; MS (FAB)
m/z 608 (M+H)+; HRMS (ESI) m/z calcd for C27H38N5O5S3 608.2030, found
608.2033 (M+H)+.
Reaction of 2 (240 mg, 0.39 mmol) with 5-(o-tolyl)-1,3,4-thiadiazole-2-thiol
(150 mg, 0.72 mmol) gave 18 as a colorless solid in 22% yield by a similar
procedure to 3. [α]D31 +88° (c 1.0, CHCl3); 1H NMR (400 MHz, CDCl3) δ 9.20
(d, J = 9.1 Hz, 1H), 7.64 (d, J = 7.9 Hz, 1H), 7.28–7.44 (m, 3H), 5.40 (br s, 1H),
5.36 (d, J = 5.5 Hz, 1H), 4.41–4.47 (m, 1H), 4.32 (qd, J = 7.1, 3.4 Hz, 1H), 4.27
(d, J = 10.3 Hz, 1H), 4.13–4.18 (m, 1H), 3.70–3.75 (m, 1H), 3.59 (dd, J = 10.1,
3.5 Hz, 1H), 3.39 (dd, J = 7.9, 5.4 Hz, 1H), 3.11 (dd, J = 10.5, 4.5 Hz, 1H), 2.61
(s, 3H), 2.41 (s, 1H), 2.19 (s, 3H), 2.06–2.17 (m, 3H), 1.86–2.03 (m, 2H), 1.57
(d, J = 7.1 Hz, 3H), 1.29–1.37 (m, 4H) and 0.85–0.96 (m, 3H); MS (FAB) m/z
597 (M+H)+; HRMS (ESI) m/z calcd for C27H41N4O5S3 597.2234, found
597.2238 (M+H)+.
(7S)-7-[5-(2-Aminopyridin-3-yl)-1,3,4-thiadiazol-2-ylthio]-7-
deoxylincomycin (24)
To a solution of 2310–12 (200 mg, 0.29 mmol) and K2CO3 (118 mg, 0.85 mmol)
in N,N-dimethylformamide (DMF) (2.0 ml) was added 5-(2-aminopyridin-3-
yl)-1,3,4-thiadiazole-2-thiol (120 mg, 0.57 mmol) and the mixture was stirred
at 80 °C for 10 h. After cooled to room temperature, the mixture was diluted
with ethyl acetate and washed with brine. The organic phase was dried over
Na2SO4, filtered and concentrated in vacuo. The residue was purified by silica
gel column chromatography (hexane-ethyl acetate) to give a colorless solid
(54 mg). To a solution of the compound obtained above (54 mg) in MeOH
(1 ml) was added 1 N HCl (1 ml) and the reaction mixture was stirred at room
temperature for 10 min. The mixture was diluted with ethyl acetate and
extracted with H2O. The aqueous phase was neutralized with 10% aqueous
NaHCO3 and extracted with ethyl acetate. The organic phase was dried over
Na2SO4, filtered and concentrated in vacuo. The resulting residue was purified
by preparative thin-layer chromatography (CHCl3/CH3OH/28% aq
(7S)-7-Deoxy-7-[5-(2-methoxyphenyl)-1,3,4-thiadiazol-2-ylthio]
lincomycin (19)
Reaction of 2 (240 mg, 0.39 mmol) with 5-(2-methoxyphenyl)-1,3,4-thiadia-
zole-2-thiol (130 mg, 0.58 mmol) gave 19 as a colorless solid in 48% yield by a
similar procedure to 3. [α]D +114° (c 1.2, CHCl3); 1H NMR (400 MHz,
30
CD3OD) δ 8.31 (dd, J = 8.0, 1.6 Hz, 1H), 7.55 (ddd, J = 8.0, 7.0, 1.6 Hz, 1H),
7.24 (d, J = 8.0 Hz, 1H), 7.10–7.18 (m, 1H), 5.27 (d, J = 5.7 Hz, 1H), 4.57
(dd, J = 9.7, 3.2 Hz, 1H), 4.43 (d, J = 9.7 Hz, 1H), 4.34 (qd, J =7.0, 3.1 Hz, 1H),
4.06–4.16 (m, 1H), 4.04 (s, 3H), 3.80–3.83 (m, 1H), 3.58 (dd, J = 10.3, 3.2 Hz,
1H), 3.26 (dd, J = 8.6, 6.0 Hz, 1H), 2.99 (dd, J = 10.4, 5.0 Hz, 1H), 2.35 (s, 3H),
2.15–2.26 (m, 1H), 2.02–2.14 (m, 2H), 2.01 (s, 3H), 1.96–2.00 (m, 1H),
1.71–1.91 (m, 1H), 1.54 (d, J = 7.0 Hz, 3H), 1.27–1.41 (m, 4H) and 0.86–0.95
(m, 3H); MS (FAB) m/z 613 (M+H)+; HRMS (ESI) m/z calcd for
C27H41N4O6S3 613.2183, found 613.2174 (M+H)+.
30
NH4OH= 10/1/0.1) to afford 24 (16 mg, 9%) as colorless solid. [α]D +84°
(c 0.22, CHCl3); 1H NMR (300 MHz, CD3OD) δ 8.10 (dd, J =4.9, 1.7 Hz, 1H),
7.87 (dd, J = 7.8, 1.7 Hz, 1H), 6.75 (dd, J = 7.8, 4.9 Hz, 1H), 5.27 (d, J = 5.6 Hz,
1H), 4.58–4.63 (m, 2H), 4.12 (dd, J = 10.2, 5.6 Hz, 1H), 3.81–3.83 (m, 1H),
(7S)-7-Deoxy-7-{5-[2-(methylthio)phenyl]-1,3,4-thiadiazol-2-ylthio}
lincomycin (20)
3.55–3.60
(m,
1
H),
3.20–3.28 (m, 1H), 3.01 (dd, J = 10.4, 5.0 Hz, 1H), 2.37 (s, 3H), 2.14–2.25
(m, 1H), 2.02–2.10 (m, 1H), 2.01 (s, 3H), 1.79–1.89 (m, 1H), 1.57
(d, J = 6.8 Hz, 3H), 1.27–1.37 (m, 4H) and 0.86–0.94 (m, 3H); MS (FAB)
m/z 599 (M+H)+; HRMS (ESI) m/z calcd for C25H39N6O5S3 599.2139, found
599.2152 (M+H)+.
Reaction of
2 (240 mg, 0.39 mmol) with 5-[2-(methylthio)phenyl]-1,3,
4-thiadiazole-2-thiol (150 mg, 0.62 mmol) gave 20 as a colorless solid in 44%
yield by a similar procedure to 3. [α]D +141° (c 1.1, CHCl3); 1H NMR
30
(400 MHz, CDCl3) δ 9.13 (d, J = 8.8 Hz, 1H), 8.00–8.06 (m, 1H), 7.42–7.54
(m, 2H), 7.29–7.37 (m, 1H), 5.35 (d, J = 5.5 Hz, 1H), 4.37–4.47 (m, 1H),
4.22–4.35 (m, 2H), 4.07–4.22 (m, 2H), 3.72 (t, J = 3.3 Hz, 1H), 3.57
(td, J = 10.0, 3.3 Hz, 1H), 3.41 (dd, J = 7.9, 5.4 Hz, 1H), 3.09 (dd, J = 10.6,
4.6 Hz, 1H), 2.50 (s, 3H), 2.18 (s, 3H), 2.04–2.16 (m, 2H), 1.89–2.01 (m, 3H),
1.55 (d, J = 7.1 Hz, 1H), 1.25–1.39 (m, 4H) and 0.84–0.97 (m, 3H); MS (FAB)
m/z 629 (M+H)+; HRMS (ESI) m/z calcd for C27H41N4O5S4 629.1954, found
629.1960 (M+H)+.
(7S)-7-Deoxy-7-{5-[2-(methoxycarbonyl)phenyl]-1,3,4-thiadiazol-2-
ylthio}lincomycin (26)
To a solution of 2511 (80 mg, 0.19 mmol) in DMF (0.5 ml) were added 1 M
sodium hexamethyldisilazane tetrahydrofuran solution (0.38 ml, 0.38 mmol)
and methyl 2-(5-chloro-1,3,4-thiadiazol-2-yl)benzoate (53 mg, 0.21 mmol) and
the mixture was stirred at room temperature for 10 min. The mixture was
diluted with ethyl acetate and washed with water. The organic phase was dried
over Na2SO4, filtered and concentrated in vacuo. The residue was purified by
silica gel column chromatography (CHCl3-MeOH) to give a colorless solid
(93 mg). 1H NMR (400 MHz, CDCl3) δ 9.00 (d, J = 9.0 Hz, 1H), 7.90–7.96
(m, 1H), 7.55–7.68 (m, 3H), 5.36 (d, J = 5.6 Hz, 1H), 5.31 (br s, 1H), 4.30–4.46
(m, 2H), 4.27 (d, J = 10.2 Hz, 1H), 4.16 (dd, J = 10.2, 5.5 Hz, 1H), 3.77–3.84
(m, 3H), 3.68–3.75 (m, 2 H), 3.59 (dd, J = 10.0, 3.2 Hz, 1H), 3.48 (s, 1H), 3.35
(dd, J = 7.9, 5.5 Hz, 1H), 3.09 (dd, J = 10.6, 4.5 Hz, 1H), 2.37 (s, 3H), 2.15–2.22
(m, 3H), 1.83–2.13 (m, 5H), 1.55 (d, J = 6.8 Hz, 3H), 1.29–1.36 (m, 3H) and
0.85-0.93 (m, 3H); MS (FAB) m/z 641 (M+H)+.
(7S)-7-Deoxy-7-{5-[2-(methylsulfonyl)phenyl]-1,3,4-thiadiazol-2-
ylthio}lincomycin (21)
Reaction of 2 (240 mg, 0.39 mmol) with 5-[2-(methylsulfonyl)phenyl]-1,3,
4-thiadiazole-2-thiol (120 mg, 0.44 mmol) gave 21 as a colorless solid in 32%
yield by a similar procedure to 3. [α]D +73° (c 1.1, CHCl3); 1H NMR
30
(400 MHz, CD3OD) δ 8.22–8.26 (m, 1H), 7.82–7.87 (m, 2H), 7.69–7.73
(m, 1H), 5.28 (d, J =5.6 Hz, 1H), 4.63 (dd, J = 9.8, 3.1 Hz, 1H), 4.51
(qd, J = 6.9, 2.9 Hz, 1H), 4.45 (d, J = 9.8 Hz, 1H), 4.12 (dd, J = 10.3,
5.6 Hz, 1H), 3.80–3.84 (m, 1H), 3.56–3.64 (m, 2H), 3.34–3.39 (m, 2H),
3.25 (dd, J = 8.5, 6.2 Hz, 1H), 3.00 (dd, J = 10.4, 5.1 Hz, 1H), 2.40 (s, 3H),
2.16–2.27 (m, 1H), 2.02–2.10 (m, 3H), 2.02 (s, 3H), 1.80–1.90 (m, 1H), 1.59
(d, J = 6.9 Hz, 3H), 1.28–1.39 (m, 4H) and 0.89–0.95 (m, 3H); MS (FAB) m/z
661 (M+H)+; HRMS (ESI) m/z calcd for C27H41N4O7S4 661.1853, found
661.1843 (M+H)+.
(7S)-7-Deoxy-7-[5-(2-dimethylcarbamoylphenyl)-1,3,4-thiadiazol-
2-ylthio]lincomycin (28)
To a solution of 26 (268 mg, 0.42 mmol) in MeOH (3.0 ml) were added
2 N NaOH (2.0 ml) and the mixture was stirred at room temperature for
30 min. The mixture was concentrated in vacuo and acidified with 1 N HCl and
extracted with CHCl3. The organic phase was dried over Na2SO4, filtered and
concentrated in vacuo to give a carboxylic acid (150 mg). To a solution of the
compound obtained above (60 mg, 0.096 mmol) in DMF (0.30 ml) were added
hydroxybenzotriazole (16 mg, 0.12 mmol) and 1-(3-dimethylaminopropyl)-
3-ethylcarbodiimide hydrochloride (22 mg, 0.12 mmol) and 2 M dimethylamine
(7S)-7-[5-(2-Cyanophenyl)-1,3,4-thiadiazol-2-ylthio]-7-
deoxylincomycin (22)
Reaction of 2 (240 mg, 0.39 mmol) with 2-(5-mercapto-1,3,4-thiadiazol-2-yl)
benzonitrile (100 mg, 0.46 mmol) gave 22 as a colorless solid in 32% yield by a
similar procedure to 3. mp 223–229 °C (decomp.); [α]D30 − 64° (c 1.5, CHCl3);
IR (KBr) 3397, 2922, 2227, 1655 and 1510 cm− 1; 1H NMR (300 MHz, CDCl3) MeOH solution (96 μl, 0.19 mmol) and stirred at room temperature for 2 h.
δ 9.05 (d, J = 8.8 Hz, 1H), 8.04 (d, J = 7.7 Hz, 1H), 7.75–7.82 (m, 1H), 7.68 The mixture was diluted with ethyl acetate and washed with 10% aqueous
The Journal of Antibiotics

Synthesis of novel lincomycin derivatives
K Kumura et al
9
30
NaHCO3 to afford 28 (52 mg, 43%) as colorless solid. [α]D +131° (c 1.2, (d, J = 5.6 Hz, 1H), 4.55 (dd, J = 9.8, 3.2 Hz, 1H), 4.42 (d, J = 10.4 Hz, 1H),
CHCl3); 1H NMR (300 MHz, CDCl3) δ 8.92 (d, J = 9.1 Hz, 1H), 7.88–7.93
(m, 1H), 7.49–7.58 (m, 2H), 7.36–7.40 (m, 1H), 5.34 (d, J = 5.4 Hz, 1H), 5.30
(d, J = 3.4 Hz, 1H), 4.34–4.44 (m, 2H), 4.23 (d, J = 10.0 Hz, 1H), 4.10–4.16
(m, 1H), 3.69–3.72 (m, 1H), 3.53–3.60 (m, 1H), 3.34–3.39 (m, 1H), 3.12
(s, 3H), 3.07–3.11 (m, 1H), 2.83 (s, 3H), 2.70–2.77 (m, 1H), 2.41 (s, 3H),
2.15–2.20 (m, 3H), 2.06–2.14 (m, 2H), 1.87–2.01 (m, 2H), 1.53 (d, J = 6.8 Hz,
3H), 1.29–1.38 (m, 4H) and 0.86–0.93 (m, 3H); MS (FAB) m/z 654 (M+H)+;
HRMS (ESI) m/z calcd for C29H44N5O6S3 654.2448, found 654.2456 (M+H)+.
4.30 (qd, J = 6.9, 3.2 Hz, 1H), 4.07–4.15 (m, 2H), 3.79–3.82 (m, 1H), 3.58
(dd, J = 10.3, 3.2 Hz, 1H), 3.25 (dd, J = 8.2, 6.2 Hz, 1H), 2.98 (dd, J = 10.5,
5.1 Hz, 1H), 2.34 (s, 3H), 2.13–2.25 (m, 1H), 2.03 (s, 3H), 1.97–2.02 (m, 1H),
1.78–1.91 (m, 1H), 1.53 (d, J = 7.0 Hz, 3H), 1.29–1.39 (m, 4H) and 0.89–0.95
(m, 3H); MS (FAB) m/z 598 (M+H)+; HRMS (ESI) m/z calcd for
C26H40N5O5S3 598.2186, found 598.2192 (M+H)+.
In vitro antibacterial activity
Minimum inhibitory concentration was determined by the agar dilution
method. Test strains were subjected to seed culture using sensitivity test broth
(Nissui Pharmaceutical, Tokyo, Japan) cultured on blood agar plate for
S. pneumoniae, S. pyogenes and H. influenzae. A 5 μl portion of cell suspension
of the test strains having about 106 colony-forming units per ml was inoculated
into sensitivity disk agar (Nissui Pharmaceutical) supplemented with 5% horse
blood and incubated at 37 °C for 20 h. Then, minimum inhibitory concentra-
tion was defined as the lowest drug concentration that prevented visible growth.
(7S)-7-[5-(2-Carbamoylphenyl)-1,3,4-thiadiazol-2-ylthio]-7-
deoxylincomycin (27)
Reaction of the carboxylic acid obtained in the first step of 28 (46 mg,
0.073 mmol) with 7 N NH3 MeOH solution (0.020 ml, 0.14 mmol) gave 27 as a
colorless solid in 44% yield by a similar procedure to 28. mp 228–235 °C
30
(decomp.); [α]D +127° (c 1.1, CHCl3); IR (KBr) 3397, 2924, 1664 and
1510 cm− 1 1H NMR (300 MHz, CD3OD) δ 7.76–7.83 (m, 1H), 7.57–7.67
;
(m, 3H), 5.27 (d, J =5.6 Hz, 1H), 4.60 (dd, J = 9.7, 3.2 Hz, 1H), 4.37–4.47
(m, 2H), 4.11 (dd, J = 10.2, 5.6 Hz, 1H), 3.81 (d, J = 2.2 Hz, 1H), 3.55–3.60
(m, 2H), 3.27 (dd, J = 8.6, 6.2 Hz, 1H), 3.53–3.63 (m, 1H), 2.34–2.42 (m, 3H),
2.01–2.08 (m, 2H), 2.00 (s, 3H), 1.79–1.90 (m, 1H), 1.56 (d, J =6.8 Hz, 3H),
1.26–1.40 (m, 4H) and 0.86–0.97 (m, 3H); 13C NMR (100 MHz, CDCl3) δ
178.8, 170.2, 166.8, 164.4, 135.7, 130.9, 130.8, 130.7, 128.3, 127.3, 89.0, 71.6,
71.1, 69.3, 68.4, 68.3, 62.6, 53.1, 44.7, 41.8, 38.1, 38.0, 35.7, 21.6, 18.9, 14.7 and
14.3; MS (FAB) m/z 626 (M+H)+; HRMS (ESI) m/z calcd for C27H40N5O6S3
626.2135, found 626.2137 (M+H)+.
CONFLICT OF INTEREST
The authors declare no conflict of interest.
ACKNOWLEDGEMENTS
We thank Dr E Shitara, Mr A Tamura and Dr T Okutomi for valuable scientific
discussion. We are grateful to Professor Emeritus Dr M Konno for supervision
through our in-house drug discovery program in lincomycin field. We are also
grateful to Ms T Miyara, Ms S Miki, Ms K Kaneda, Dr T Murata and Mr S Sato
for contribution toward analytical chemistry; Mr K Yamada for biological
studies; and Ms M Takagi for manuscript. We also thank Ms M Ishii for
direction in intellectual properties.
(7S)-7-[5-(2-Aminophenyl)-1,3,4-thiadiazol-2-ylthio]-7-
deoxylincomycin (29)
To a solution of compound 9 (390 mg, 0.63 mmol) in ethanol (12.0 ml) was
added SnCl2·H2O (560 mg, 2.5 mmol), NaBH4 (16.0 mg, 0.42 mmol) and
stirred at room temperature for 2 h. The mixture was concentrated under
reduced pressure. The resulting residue was dissolved by ethyl acetate, washed
with water, dried over MgSO4 and concentrated in vacuo. The resulting residue
was purified by preparative thin-layer chromatography (CHCl3/CH3OH/28%
aq NH4OH= 20/1/0.1) to obtain the title compound as a colorless solid
(123 mg, 33%). [α]D31 +62° (c 1.3, CHCl3); 1H NMR (400 MHz, CDCl3) δ 8.94
(d, J = 9.3 Hz, 1H), 7.37 (dd J = 7.9, 1.4 Hz, 1H), 7.21–7.26 (m, 1H), 6.81
(d, J = 8.1 Hz, 1H), 6.74 (t, J = 7.3 Hz, 1H), 6.10 (br s, 2H), 5.36 (d, J = 5.6 Hz,
1H), 5.28–5.35 (m, 1H), 4.23–4.33 (m, 2H), 4.12–4.18 (m, 1H), 3.68–3.75
(m, 1H), 3.53–3.13 (m, 1H), 3.31 (dd, J = 8.0, 5.7 Hz, 1H), 3.09 (dd, J = 10.5,
4.7 Hz, 1H), 2.72–2.81 (m, 1H), 2.39 (s, 3H), 2.18 (s, 3H), 2.04–2.16 (m, 2H),
1.87–2.02 (m, 3H), 1.55 (d, J = 7.1 Hz, 3H), 1.25–1.38 (m, 5H) and 0.87–0.96
(m, 3H); MS (FAB) m/z 598 (M+H)+; HRMS (ESI) m/z calcd for
C26H40N5O5S3 598.2186, found 598.2185 (M+H)+.
1
2
3
4
Mason, D. J., Dietz, A. & Deboer, C. Lincomycin, a new antibiotic I. Discovery and
biological properties. Antimicrob. Agents Chemother. 1962, 554–559 (1962).
Magerlein, B. J., Birkenmeyer, R. D. & Kagan, F. Chemical modification of lincomycin.
Antimicrob. Agents Chemother. 1966, 727–736 (1966).
Schlünzen, F. et al. Structural basis for the interaction of antibiotics with the peptidyl
transferase centre in eubacteria. Nature 413, 814–821 (2001).
Morimoto, S., Takahashi, Y., Watanabe, Y. & Omura, S. Chemical modification of
erythromycins. I. Synthesis and antibacterial activity of 6-O-methylerythromycins A. J.
Antibiot. 37, 187–189 (1984).
Djokic, S. et al. Erythromycin series. Part 13. Synthesis and structure elucidation of
10-dihydro-10-deoxo-11-methyl-11-azaerythromycin A. J. Chem. Res. Synop. 1988,
152–153 (1988).
Weisblum, B. Erythromycin resistance by ribosome modification. Antimicrob. Agents
Chemother. 39, 577–585 (1995).
Ajito, K., Miura, T., Furuuchi, T. & Tamura, A. Sixteen-membered macrolides: chemical
5
6
7
8
modifications and future applications. Heterocycles 89, 281–352 (2014).
Shah, P. J., Vakil, N.
& Kabakov, A. Role of intravenous immune globulin in
(7S)-7-[5-(3-Aminophenyl)-1,3,4-thiadiazol-2-ylthio]-7-
deoxylincomycin (30)
streptococcal toxic shock syndrome and Clostridium difficile infection. Am. J. Health
Syst. Pharm. 72, 1013–1019 (2015).
Umemura, E. et al. Synthesis of Novel lincomycin derivatives and their in vitro
9
Compound 30 was obtained from compound 10 (75 mg, 0.13 mmol) as a
antibacterial activities. J. Antibiot. 66, 195–198 (2013).
30
colorless solid in 24% yield by a similar procedure to 29. [α]D +140° (c 1.2,
10 Wakiyama, Y. et al. Synthesis and structure–activity relationships of novel lincomycin
derivatives. Part 1. Newly generated antibacterial activities against Gram-positive
bacteria with erm gene by C-7 modification. J. Antibiot. 69, 368–380 (2016).
11 Wakiyama, Y. et al. Synthesis and structure-activity relationships of novel lincomycin
derivatives. Part 2. Synthesis of 7(S)-7-deoxy-7-(4-morpholinocarbonylphenylthio)linco-
mycin and its 3-dimensional analysis with rRNA. J. Antibiot. 69, 428–439 (2016).
12 Kumura, K. et al. Synthesis and antibacterial activity of novel lincomycin derivatives. I.
Enhancement of antibacterial activities by introduction of substituted azetidines.
J. Antibiot. 69, 440–445 (2016).
CHCl3); 1H NMR (300 MHz, CDCl3) δ 8.94 (d, J = 9.1 Hz, 1H), 7.37
(d, J = 8.1 Hz, 1H), 7.20–7.26 (m, 1H), 6.80 (d, J = 8.1 Hz, 1H), 6.73
(t, J = 7.6 Hz, 1H), 6.11 (br s, 2H), 5.35 (d, J = 5.5 Hz, 1H), 5.32 (br s, 1H),
4.37–4.49 (m, 1H), 4.23–4.35 (m, 2H), 4.15 (dd, J = 10.0, 5.3 Hz, 1H), 3.71
(d, J = 2.5 Hz, 1H), 3.58 (dd, J = 10.0, 3.6 Hz, 1H), 3.31 (dd, J = 7.4, 5.3 Hz,
1H), 3.09 (dd, J = 10.2, 4.9 Hz, 1H), 2.39 (s, 3H), 2.18 (s, 3H), 2.05–2.16
(m, 2H), 1.86–2.02 (m, 3H), 1.55 (d, J = 6.9 Hz, 3H), 1.22–1.40 (m, 4H) and
0.87–0.97 (m, 3H); MS (FAB) m/z 598 (M+H)+; HRMS (ESI) m/z calcd for
C26H40N5O5S3 598.2186, found 598.2192 (M+H)+.
13 Denis, A. et al. Synthesis and antibacterial activity of HMR 3647 a new ketolide highly
potent against erythromycin-resistant and susceptible pathogens. Bioorg. Med. Chem.
Lett. 9, 3075–3080 (1999).
14 Miura, T. et al. Novel azalides derived from sixteen-membered macrolides. I. Isolation of
the mobile dialdehyde and its one-pot macrocyclization with an amine. J. Antibiot. 60,
407–435 (2007).
15 Miura, T. et al. Novel azalides derived from 16-membered macrolides. III. Azalides
modified at the C-15 and 400 positions: Improved antibacterial activities. Bioorg. Med.
Chem. 18, 2735–2747 (2010).
(7S)-7-[5-(4-Aminophenyl)-1,3,4-thiadiazol-2-ylthio]-7-
deoxylincomycin (31)
Compound 31 was obtained from compound 11 (50 mg, 0.84 mmol) as
30
a colorless solid by a similar procedure to 29. [α]D +67° (c 1.1, CHCl3);
16 Houtman, R. L. & Mich, P. Trimethylsilyl ethers of lincomycin and its compounds.
US Patent US3418414 (1966).
1H NMR (400 MHz, CD3OD) δ 7.59–7.65 (m, 2H), 6.70–6.75 (m, 2H), 5.26
The Journal of Antibiotics