Synthesis and antibacterial activity of novel lincomycin derivatives. IV. Optimization of an N-6 substituent

Article abstract of DOI:10.1038/ja.2017.143

The design and synthesis of lincomycin derivatives modified at the C-6 and C-7 positions are described. A substituent at the C-7 position is a 5-aryl-1,3,4-thiadiazol-2-yl-thio group that generates antibacterial activities against macrolide-resistant Streptococcus pneumoniae and Streptococcus pyogenes carrying an erm gene. An additional modification at the C-6 position was explored in application of information regarding pirlimycin and other related compounds. These dual modifications were accomplished by using methyl α-thiolincosaminide as a starting material. As a result of these dual modifications, the antibacterial activities were improved compared with those of compounds with a single modification at the C-7 position. The antibacterial activities of selected compounds in this report against macrolide-resistant S. pneumoniae and S. pyogenes with an erm gene were superior to those of telithromycin.

Full text of DOI:10.1038/ja.2017.143

The Journal of Antibiotics (2017), 1–10
2017 Japan Antibiotics Research Association All rights reserved 0021-8820/17
www.nature.com/ja
&
ORIGINAL ARTICLE
Synthesis and antibacterial activity of novel lincomycin
derivatives. IV. Optimization of an N-6 substituent
Ko Kumura, Yoshinari Wakiyama, Kazutaka Ueda, Eijiro Umemura, Yoko Hirai, Keiko Yamada and
Keiichi Ajito
The design and synthesis of lincomycin derivatives modified at the C-6 and C-7 positions are described. A substituent at the C-7
position is a 5-aryl-1,3,4-thiadiazol-2-yl-thio group that generates antibacterial activities against macrolide-resistant
Streptococcus pneumoniae and Streptococcus pyogenes carrying an erm gene. An additional modification at the C-6 position
was explored in application of information regarding pirlimycin and other related compounds. These dual modifications were
accomplished by using methyl α-thiolincosaminide as a starting material. As a result of these dual modifications, the
antibacterial activities were improved compared with those of compounds with a single modification at the C-7 position. The
antibacterial activities of selected compounds in this report against macrolide-resistant S. pneumoniae and S. pyogenes with an
erm gene were superior to those of telithromycin.
The Journal of Antibiotics advance online publication, 8 November 2017; doi:10.1038/ja.2017.143
INTRODUCTION
revealed the overlap of binding site on 50S ribosome. Thus, CLDM
Macrolide antibiotics have had a significant role in treatment of shows almost no antibacterial activity against these resistant pathogens
respiratory infections. Clarithromycin1 and azithromycin2 synthesized as shown in Table 1. CLDM, however, is attractive because of its safety
from 14-membered erythromycin are clinically important macrolides profile and effectiveness against resistant pathogens expressing a drug
and widely used over many years (Figure 1). However, prevalence of efflux pump. In addition, CLDM has no gastrointestinal side effect
macrolide resistance in Gram-positive bacteria such as S. pneumoniae caused by modulating motilin receptor.12 Furthermore, CLDM has
has been causing serious clinical problems.3,4 Clarithromycin and been reported to be effective for invasive group A streptococcal
azithromycin are inactive against resistant strains of S. pneumoniae, infections caused by S. pyogenes.13 A simple chemical structure of
which have a mechanism of ribosome methylation by an erm gene and CLDM compared with that of macrolide is attractive from the
decreased antibacterial activities against resistant strains with a mef viewpoint of production cost. Based on these reasons, we have been
gene, which expresses the efflux pump. Although telithromycin (TEL)5 expanding chemical modifications of lincosamide, in order to generate
derived from natural erythromycin has improved antibacterial activ-
ities against resistant S. pneumoniae with an erm gene and/or a mef S. pneumoniae and S. pyogenes with erm and mef genes.
gene, safety problems6 of TEL made its clinical use difficult. Another
It has been reported that modifications at the C-7 position of LCM
a novel antibacterial agent that is effective against resistant
promising example is a group of 16-membered azalides7,8 that are tend to provide comparable antibacterial activity to that of LCM.14,15
effective against resistant S. pneumoniae with an erm gene. However, against susceptible strains. We reported chemical modifications of
these compounds are still in the research phase and have not entered LCM and clarified that (7S)-7-deoxy-7-thiolincomycin derivatives16–22
development. Novel therapeutic agents that are effective against the exhibited moderate to strong antibacterial activities against S. pneu-
resistant S. pneumoniae without concerns of adverse events are moniae and S. pyogenes with an erm gene. Compound 1 that has a
required in clinical sites.
phenyl-thiadiazol-2-yl-thio moiety to the C-7 position showed
Lincomycin (LCM)9 (Figure 2) is one of secondary metabolites of response (very weak antibacterial activities) against those resistant
Streptomyces lincolnensis and has been used as antibacterial agent pathogens (Table 1). A nitro group at the 2-position and methoxy
mainly against Gram-positive bacteria. Chemical modification of LCM groups at the 4- and 5-positions in the benzene ring of 1 had a key
led to clindamycin (CLDM),10 which has an enhanced antibacterial role for enhancement of the antibacterial activity against S. pneumo-
activity against S. pneumoniae and an improved pharmacokinetic niae with an erm gene.21,22
profile. Although LCM and CLDM are distinct from macrolide
The ring-size modification of a proline moiety linked to the N-6
antibiotics in their chemical structures, they have cross-resistance position of lincosamides was reported by several groups23–27. As for
against S. pneumoniae with an erm gene.11 The cross-resistance is the piperidine derivatives, pirlimycin23 has been used for animal drugs
consistent with the result of X-ray crystallographic studies that and VIC-10555524–26 displays enhanced in vitro and in vivo activities
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
Received 22 August 2017; revised 7 October 2017; accepted 7 October 2017

Optimization of lincomycin derivatives
K Kumura et al
2
N
N
Me
N
O
N
Me
Me
Me
Me
O
HO
Me
OMe
Me
HO
Me
OH
Me
Me
Me
Me
OH
OH
Me
NMe2
Me
NMe2
Me
Me
HO
HO
N
OMe
Me
O
O
O
O
O
O
NMe2
Me
O
O
Me
Me
Me
HO
O
O
O
O
O
OMe
Me
OMe
Me
O
O
Me
Me
Me
Me
Me
O
O
OH
OH
O
O
Me
Clarithromycin (CAM)
Azithromycin (AZM)
Telithromycin (TEL)
Figure 1 Structures of widely used macrolides, clarithromycin and azithromycin, and telithromycin.
R2
1: R3 =
R3
N
N
S
Me
4'
Me
O Me
7
O Me
S
O Me
2'
O2N
R1
O
R
O
7
7
N
6
HN
6
N
HN
6
N
HN
HO
2: R3 =
3: R3 =
Me
H
Me
H
H
HO
H
O
HO
SMe
SMe
SMe
O2N
HO
OH
HO
OH
HO
OH
OMe
OMe
Pirlimycin: R1 = Cl; R2 = H
VIC-105555: R1 = R2 = Me
Lincomycin (LCM): R =
Clindamycin (CLDM): R =
OH
Cl
Figure 2 Structures of lincomycin, clindamycin, pirlimycin, VIC-105555, compounds 1, 2 and 3.
Table 1 Antibacterial activities of lincomycin derivatives previously reported by our group and known antibiotics (MIC; μg ml− 1 a
)
No. Test organismb
Characteristics
CLDM
CAM
TEL
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Optimization of lincomycin derivatives
K Kumura et al
3
R
R
4'
O Me
O Me
2'
7
OH
OH
O
6
N
Boc
HN
b, c
N
Boc
HN
2',4'-cis
H
O
H
HO
SMe
TMSO
SMe
Me
2',4'-cis
OH
O
R
HO
OH
TMSO
6a: R = Et
6b: R = nPr
6c: R = nBu
OTMS
4'
H2N
HO
O
2'
H
5a: R = Et
a
+
5b: R = nPr
5c: R = nBu
SMe
N
OH
Boc
HO
OH
( )-4a: R = Et
( )-4b: R = nPr
( )-4c: R = nBu
Me
Me
+
MTL
O Me
O Me
MTL:
OH
OH
Methyl
α-thiolincosaminide
N
Boc
HN
HO
b, c
N
HN
Boc
H
O
H
O
SMe
TMSO
SMe
HO
OH
TMSO
OTMS
5b'
6b'
Scheme 1 Synthesis of key intermediates having a 4-substituted piperidine 2-carbonyl group. Conditions: (a) DCC, HOBt, DMF, rt; (b) TMSCl, HMDS,
pyridine, rt; (c) 6N AcOH, MeOH, rt.
with superior efficacy over clindamycin in several experimental models the piperidine moiety and antibacterial activity, 2′-α-4′-α-cis isomer 7b′
(Figure 2). Although these compounds did not show antibacterial was also synthesized in the similar manner to 7a–7k from 6b′.
activities against resistant Gram-positive bacteria with an erm gene, Compound 7b was more polar than 7b′ on TLC as in the case of 6b
in vitro and/or in vivo properties of (7S)-7-deoxy-7-thiolincomycin and 6b′. A major reason for relatively low yield of these Mitsunobu
derivatives are expected to be improved by the modification of the reactions was explained by generation of an N-connected byproduct in
proline moiety. In this article, we report optimization of the proline the thiadiazole moiety instead of the desired S-connected derivative.
moiety of (7S)-7-deoxy-7-(5-(2-nitrophenyl)-1,3,4-thiadiazol-2-yl- 1′-Methylated compounds 8d, 8e and 8f were prepared by reductive
thio)lincomycin derivatives, in order to generate novel LCM deriva- N-methylation of the corresponding secondary amine. Synthesis of
tives exhibiting stronger antibacterial activities than TEL.
VIC-105555 and 10 were conducted based on the reported
procedure24 as shown in Scheme 3. The reduction of 9 gave a
diastereomeric mixture of VIC-105555 and 10. We separated these
isomers and a more polar isomer was assigned as VIC-105555.
Chemistry
Synthesis of important intermediates that have 4′-substituted piper-
idine-2′-carbonyl group instead of a natural 4′-propyl proline part is
shown in Scheme 1. A racemic mixture of 2,4-cis-piperidine-
carboxylic acids was prepared by a reported procedure28 from Antibacterial activities of LCM derivatives that have the 5-(2-nitro-
4-alkylpyridine. The protection of an amine gave carboxylic acids phenyl)-1,3,4-thiadiazol-2-yl-thio group at the C-7 position and the
RESULTS AND DISCUSSION
(
)-4a, ( )-4b and ( )-4c. Condensation of these carboxylic acids 4′-alkyl piperidin-2′-carbonylamino group at the C-6 position are
with methyl α-thiolincosaminide29 gave 1′-N-Boc protected com- shown in Table 2. Regarding stereoisomers 7b and 7b′, which are
pounds 5a, 5b and 5c as a 1:1 diastereomeric mixture. These mixtures 4′-propyl derivatives, antibacterial activities of 7b were clearly more
showed two spots on TLC, but complete separation by silica gel potent than those of 7b′ as expected. According to the result, the
chromatography was difficult. After exploring a solvent for selective assignment of stereochemistry in the piperidine moiety was also
precipitation, we found that less polar isomer was precipitated from supported by antibacterial activity. Similarly, VIC-105555 showed
ethyl acetate and more polar isomer was enriched in mother liquor. reported antibacterial activities against S. pneumoniae and S. pyogenes
Birkenmeyer et al.23 reported that more active 2′-β-4′-β-cis isomers of without an erm gene and antibacterial activities of stereoisomer 10 was
pirlimycin derivatives showed more polar profile on TLC. Based on much weaker than those of VIC-105555. Compared with a natural
the report, the more polar isomer of 5b was assigned as a 2′-β-4′-β-cis proline analog 2, transformation to 4′-n-propylpiperidine-2′-carbonyl
isomer. The 2′-β-4′-β-cis isomers of 5b were converted to tetra-O- analog remarkably improved the antibacterial activities against resis-
trimethylsilyl intermediate, which was followed by regioselective tant S. pneumoniae and S. pyogenes with an erm gene. 4′-Ethyl analog
deprotection of the 7-O-trimethylsilyl group and silica gel column (7a) showed improved antibacterial activities against susceptible
chromatography, afforded 6b. The other 2′-α-4′-α-cis isomer 6b′ was strains of S. pneumoniae and S. pyogenes compared to 2. However,
prepared from less polar isomer (5b′) as well. Regarding 4′-ethyl and its antibacterial activities against resistant S. pneumoniae with an erm
4′-n-butyl derivatives, 2′-β-4′-β-cis isomers 6a and 6c were obtained in gene were weaker than those of 7b. In contrast, 4′-n-butyl analog (7c)
the similar manner to 6b.
exhibited more potent antibacterial activities than 7b against all of the
Synthesis of (7S)-7-deoxy-7-(5-phenyl-1,3,4-thiadiazol-2-yl-thio)- test organisms. Antibacterial activities of these derivatives were
LCM derivatives modified at the C-6 position is shown in Scheme significantly superior to TEL against S. pyogenes with an erm gene.
2. Introductions of the 5-substituted 1,3,4-thiadiazol-2-yl-thio group
Table 3 shows antibacterial activities of 4-fluoro-2-nitrophenyl
at the C-7 position were achieved by Mitsunobu reaction and analogs. The antibacterial activities of 7d, 7e and 7f indicated that
subsequent deprotection led to target compounds 7a–7k. In order the effect of a fluorine atom on antibacterial activity against
to obtain information on the relationship between stereochemistry in S. pneumoniae and S. pyogenes was unclear. However, antibacterial
The Journal of Antibiotics

Optimization of lincomycin derivatives
K Kumura et al
4
O2N
O2N
O2N
R2
R2
Me
N
N
N
R1
R1
N
S
R3
N
S
N
S
S
S
S
O Me
O Me
HN
H
HO
O Me
4'
4'
4'
2'
2'
2'
c
6a
6b
6c
a, b
a, b
NH HN
HO
N
NH HN
HO
6b'
H
O
Me
O
H
O
SMe
SMe
SMe
HO
OH
HO
OH
HO
OH
7a: R1 = Et, R2 = R3 = H
7g: R1
7h: R1
=
=
nPr, R2 = H, R3 = NHMe
nPr, R2 = H, R3 = OMe
8d: R1 = Et, R2 = F
7b'
7b: R1
7c: R1
=
nPr, R2 = R3 = H
nBu, R2 = R3 = H
8e: R1
8f: R1
=
nPr, R2 = F
=
nBu, R2 = F
=
7i: R1 = Et, R2 = R3 = OMe
7d: R1 = Et, R2 = F, R3 = H
7j: R1
=
nPr, R2 = R3 = OMe
7e: R1
7f: R1
=
nPr, R2 = F, R3 = H 7k: R1 nBu, R2 = R3 = OMe
nBu, R2 = F, R3 = H
=
=
Scheme 2 Synthesis of (7S)-7-deoxy-7-(5-phenyl-1,3,4-thiadiazol-2-yl-thio)-LCM derivatives having a 4-substituted piperidine 2-carbonyl group. Conditions:
(a) ArSH, DEAD, PPh3, THF or toluene, 0 °C to rt; (b) TFA, DCM, − 20 °C to rt; (c) 36% HCHO, NaBH(OAc)3, AcOH, MeOH or EtOH, rt.
Me
Me
Me
4'
4'
O Me
O Me
O Me
2'
2'
Me
O
Me
O
Me
O
NH HN
HO
NH HN
HO
N
HN
H
HO
+
H
H
SMe
SMe
SMe
HO
OH
HO
OH
HO
OH
9
VIC-105555
10
Scheme 3 Synthesis of VIC-105555 and its 2′-α-4′-α-cis isomer 10. Condition: H2, PtO2, conc. HCl, MeOH-H2O, rt.
Table 2 Antibacterial activities of novel lincomycin derivatives (MIC; μg ml− 1 a
)
No. Test organismb
2
VIC-105555
Characteristics
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Optimization of lincomycin derivatives
K Kumura et al
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Table 3 Antibacterial activities of novel lincomycin derivatives (MIC; μg ml− 1 a
)
No. Test organismb
Characteristics
TEL
activities of 7f against S. pneumoniae with an erm gene were generally noted that antibacterial activities of 7k against resistant strains with an
more potent than those of TEL as well as 7c. On the other hand, 7d, erm gene are almost same as those against susceptible strains. These
7e and 7f exhibited enhanced antibacterial activities against Haemo- results encouraged us to investigate the antibacterial activities of
philus influenzae compared with the corresponding compounds 7a, 7b Mycoplasma pneumoniae. It is reported that macrolide resistant
and 7c without a fluorine atom. Compounds 8d, 8e and 8f, which
have a methyl group at the 1′-position showed weaker antibacterial
activities against resistant S. pneumoniae and S. pyogenes with an erm
gene than corresponding 1′-demethyl compounds, respectively.
Antibacterial activities of 2-nitrophenyl derivatives that have sub-
stituent(s) in the benzene ring are shown in Table 4. We previously
reported22 that the introduction of a substituent such as a methyla-
mino group and a methoxy group to the 5-position of the benzene
ring of LCM analog possessing a natural 4′-propyproline moiety
dramatically improved the antibacterial activities and their antibacter-
ial activities were further enhanced by additional substitution at the
4-position of the benzene ring. According to the antibacterial activities
of 7g and 7h, ring size expansion from a pyrrolidine ring found in the
original LCM to the piperidine ring enhanced antibacterial activities
against S. pneumoniae and S. pyogenes as in the case of the
2-nitrophenyl derivatives and 4-fluoro-2-nitrophenyl derivatives. In
addition, the conversion of 4,5-dimethoxy-2-nitrophenyl derivative 3
(Figure 2) to a piperidine analog gave 7j that exhibited apparently
M. pneumoniae has been prevailing in China, Japan and other
countries.30 Compounds tested showed potent antibacterial activities
against resistant M. pneumonia, except for 7h (#18).
In summary, we previously reported that 1 possessing the 5-phenyl-
1,3,4-thiadiazol-2-yl-thio group at the C-7 position showed weak
antibacterial activities against the resistant pathogens. In the course of
our continuous chemical derivatization, target antibacterial activities
were significantly improved. Compound 3 that has two methoxy
groups at the benzene ring exhibited potency comparable to that of
TEL. In this article, an additional modification at the C-6 position led
to 7k possessing the 4-n-butylpiperidine-2-carbonyl group instead of
the 4-n-propylpyrrolidin-2-carbonyl group at the C-6 position.
Selected compound 7k exhibited significantly potent antibacterial
activities against the resistant pathogens than TEL. This series of
compounds has a nitro group at the benzene ring. Although it is
known that a nitro group has a risk for mutagens and carcinogens,
there are drugs and drug candidates that have a nitro group.
more potent antibacterial activities against resistant S. pneumoniae and CONCLUSIONS
A series of LCM derivatives that have the 5-(2-nitrophenyl)-1,3,4-
S. pyogenes with an erm gene than TEL. Although antibacterial
thiadiazol-2-yl-thio moiety at the C-7 position in S-configuration and
activities of 4′-ethyl derivative (7i) against resistant S. pneumoniae
with an erm gene were remarkably weakened, 4′-n-butyl derivative the 4-alkylpipelidine-2-carbonylamino group at the C-6 position was
(7k) showed more potent antibacterial activities against resistant S. synthesized. Introductions of a substituent at the C-7 position were
pneumoniae and S. pyogenes with an erm gene than TEL. It should be accomplished by the Mitsunobu reaction, and stereochemistry of
The Journal of Antibiotics

Optimization of lincomycin derivatives
K Kumura et al
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Table 4 Antibacterial activities of novel lincomycin derivatives (MIC; μg ml− 1 a
)
No. Test organismb
Characteristics
TEL
O2N
O2N
OMe
OMe
OMe
OMe
Me
N
N
N
N
N
S
N
S
S
S
O Me
N
O Me
NH HN
O Me
N
Me
Me
S
S
N
Me
N
Me
H
H
H
O
H
O
H
O
HO
HO
SMe
HO
SMe
HO
HO
SMe
OH
HO
OH
OH
1
3
7k
0.015-0.03 μg / mL
0.25-1 μg / mL
16-128 μg / mL
Figure 3 Summary of SAR between potency (MIC against resistant S. pneumoniae with an erm gene) and (7S)-5-aryl-1,3,4-thiadiazol-2-yl-thio-LCM
derivatives.
4-alkylpiperidine-2-carbonyl moiety was assigned by the reported of SAR between antibacterial activity against resistant S. pneumoniae
information on the relationship between stereochemistry and polarity.
Additional modification at the C-6 position improved antibacterial
activities of (7S)-1,3,4-thiadiazol-2-yl-thio LCM derivatives. In this
study, we found the 4-n-butylpiperidine-2-carbonylamino group had
the most potent functionality at the C-6 position against resistant
S. pneumoniae and S. pyogenes with an erm gene. In particular,
compound 7k exhibited the most potent antibacterial activities among
all our (7S)-1,3,4-thiadiazol-2-yl-thio-LCM derivatives and apparently
with an erm gene and (7S)-7-(5-aryl-1,3,4-thiadiazol-2-yl-thio)-LCM
derivatives is shown in Figure 3. This series of LCM derivatives is
promising to overcome maclolide-resistant S. pneumoniae and
S. pyogenes with an erm gene.
EXPERIMENTAL PROCEDURES
General
1H NMR spectra were measured with Varian Gemini-300 (Varian, Inc., Palo
more potent in vitro than TEL against the resistant strains. Summary Alto, CA, USA) for 300 MHz, JEOL JNM-GSX 400 (JEOL Ltd, Tokyo, Japan)
The Journal of Antibiotics

Optimization of lincomycin derivatives
K Kumura et al
7
for 400 MHz or BRUKER Ascend 400 NMR spectrometer (BRUKER Corpora- 4′S)-1′-N-(tert-butoxycarbonyl)-4′-(n-propyl)piperidine-2′-
tion, Coventry, UK) for 400 MHz in CDCl3 or CD3OD with 0.03%
carbonyl]-α-thiolincosaminide
tetramethylsilane as an internal standard. MS 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). Column chromatography was
performed with silica gel 60 N (Kanto Chemical, Tokyo, Japan, spherical,
neutral).
Compound
( )-4b (11.7 g, 43.1 mmol), 1-hydroxybenzotriazole (7.55 g,
55.8 mmol), N,N′-dicyclohexylcarbodiimide (11.0 g, 53.3 mmol) and methyl
α-thiolincosaminide (14.2 g, 56.1 mmol) in N,N′-dimethylformamide (100 ml)
were treated for 12 h according to the similar procedure as described for the
preparation of mixture 5a to afford methyl 6-N-[1′-N-(tert-butoxycarbonyl)-4′-
(n-propyl)piperidine-2′-carbonyl]-α-thiolincosaminide (18.5 g, 84.9%, (2′S, 4′
R) isomer: (2′R, 4′S) isomer= ca. 50:50) as a colorless solid. To this colorless
solid was added ethyl acetate and insoluble matter was collected by filtration to
afford 5b′ (3.2 g, 15%) as a colorless solid and ethyl acetate solution was
concentrated under reduced pressure to afford mixture 5b (13.5 g, 62%, 20%
de ((2′S, 4′R): (2′R, 4′S) = 60:40)) as a colorless solid. 5b′: 1H NMR (400 MHz,
CDCl3) δ 6.55 (d, J = 8.6 Hz, 1H), 5.34 (d, J = 5.5 Hz, 1H), 4.62 (br s, 1H),
4.11–4.27 (m, 4H), 3.99 (d, J = 9.4 Hz, 1H), 3.90 (br s, 1H), 3.48–3.57 (m, 2H),
3.32–3.42 (m, 1H), 2.85–2.94 (m, 2H), 2.64 (br s, 1H), 2.16 (s, 3H), 1.94–2.03
(m, 1H), 1.77–1.87 (m, 1H), 1.62–1.69 (m, 1H), 1.50–1.59 (m, 1H), 1.47 (s,
9H), 1.23–1.38 (m, 5H), 1.22 (d, J = 6.4 Hz, 3H), 0.89 (t, J = 6.9 Hz, 3H); MS
Mixture 5a of methyl 6-N-[(2′S, 4′R)-1′-N-(tert-butoxycarbonyl)-4′-
ethylpiperidine-2′-carbonyl]-α-thiolincosaminide and methyl 6-N-
[(2′R, 4′S)-1′-N-(tert-butoxycarbonyl)-4′-ethylpiperidine-2′-
carbonyl]-α-thiolincosaminide
To a solution of ( )-4a (6.66 g, 25.9 mmol) in N,N′-dimethylformamide
(45 ml) were added 1-hydroxybenzotriazole (3.50 g, 25.9 mmol), N,N′-dicy-
clohexylcarbodiimide (6.05 g, 29.3 mmol), methyl α-thiolincosaminide (7.37 g,
29.1 mmol) and triethylamine (10.0 ml, 71.7 mmol), and stirred at room
temperature for overnight. To the mixture was added H2O and filtrated. Ethyl
acetate was added to the filtrate and washed with saturated aqueous NaHCO3.
The organic phase was dried over Na2SO4, filtrated and concentrated under
reduced pressure. The resulting residue was purified by silica gel column
chromatography (hexane/ethyl acetate= 50/50 to ethyl acetate, then ethyl
acetate to ethyl acetate/MeOH = 90/10) to afford methyl 6-N-[1′-N-(tert-
butoxycarbonyl)-4′-ethylpiperidine-2′-carbonyl]-α-thiolincosaminide (18.5 g,
84.9%, (2′S, 4′R) isomer: (2′R, 4′S) isomer= ca 50:50) as a colorless solid. To
this colorless solid was added ethyl acetate, and insoluble matter was filtrated
off and ethyl acetate solution was concentrated under reduced pressure to
afford mixture 5a (7.31 g, 60% de ((2′S, 4′R): (2′R, 4′S) = 80:20)) as a colorless
solid. 1H NMR (400 MHz, CDCl3) δ 6.72 (br s, 0.8H), 6.55 (d, J = 8.6 Hz,
0.2H), 5.30–5.36 (m, 1H), 4.58–4.65 (m, 0.2 H), 4.46 (br s, 0.8H), 4.07–4.26
(m, 5H), 3.95–3.98 (m, 0.8H), 3.90 (br s, 0.2H), 3.47–3.62 (m, 2H), 3.31–3.41
(m, 1H), 2.80–3.03 (m, 1H), 2.55–2.70 (m, 2H), 2.17 (s, 3H), 1.96–2.04 (m,
1H), 1.78–1.88 (m, 1H), 1.61–1.74 (m, 1H), 1.44–1.49 (m, 9H), 1.28–1.38 (m,
4H), 1.20–1.24 (m, 3H), 0.91 (t, J = 7.3 Hz, 3H).
1
(ESI) m/z 507 (M+H)+. 5b: H NMR (400 MHz, CDCl3) δ 6.74 (br s, 0.6H),
6.54 (d, J = 8.7 Hz, 0.4H), 5.30–5.35 (m, 1H), 4.60 (br s, 0.4H), 4.45 (br s,
0.6H), 3.88–4.27 (m, 6H), 3.47–3.62 (m, 2H), 3.28–3.42 (m, 1H), 2.61–3.06
(m, 3H) 2.16 (m, 3H), 1.92–2.02 (m, 1H), 1.74–1.86 (m, 1H), 1.61–1.67 (m,
1H), 1.49–1.54 (m, 1 H), 1.42–1.49 (m, 9H), 1.25–1.37 (m, 5H), 1.19–1.25 (m,
3H), 0.86–0.91 (m, 3H).
Methyl 6-N-[(2′S, 4′R)-1′-N-(tert-butoxycarbonyl)-4′-(n-propyl)
piperidine-2′-carbonyl]-2,3,4-tris-O-(trimethylsilyl)-α-
thiolincosaminide (6b)
Mixture 5b (13.5 g, 26.6 mmol, 20% de ((2′S, 4′R): (2′R, 4′S) = 60:40),
trimethylchlorosilane (17.0 ml, 133 mmol) and hexamethyldisilazane
(27.9 ml, 133 mmol) in pyridine (50 ml) were treated for 40 min according
to the similar procedure as described for the preparation of 6a and the crude
tetrakis-O-trimethylsilyl intermediate and 6 N acetic acid (5.8 ml) in MeOH
(138 ml) were treated for 2.5 h according to the similar procedure as described
for the preparation of 6a to afford 6b (9.28 g, 48% in 2 steps from
diastereomeric mixture 5b) as a colorless solid. 1H NMR (400 MHz, CDCl3)
δ 6.36 (d, J =9.4 Hz, 1H), 5.17 (d, J = 5.5 Hz, 1H), 4.30–4.37 (m, 1H), 4.09–
4.19 (m, 2H), 4.06 (d, J = 8.3 Hz, 1H), 3.95–4.03 (m, 1H), 3.98–3.92 (m, 1H),
3.61 (dd, J = 9.5, 2.6 Hz, 1H), 3.44–3.55 (m, 1H), 3.3–3.41 (m, 1H), 2.92 (d,
J = 6.5 Hz, 1H), 2.06 (s, 3H), 2.00–2.05 (m, 1H), 1.78–1.90 (m, 1H), 1.49–1.64
(m, 2H), 1.42–1.49 (m, 9H), 1.20–1.37 (m, 5H), 1.17 (d, J = 6.4 Hz, 3H), 0.85–
0.92 (m, 3H), 0.19–0.20 (m, 9H), 0.13–0.15 (m, 18H); MS (ESI) m/z 723
(M+H)+.
Methyl 6-N-[(2′S, 4′R)-1′-N-(tert-butoxycarbonyl)-4′-
ethylpiperidine-2′-carbonyl]- 2,3,4-tris-O-(trimethylsilyl)-α-
thiolincosaminide (6a)
To a solution of mixture 5a (7.31 g, 14.8 mmol, 60% de ((2′S, 4′R):(2′R, 4′
S) = 80:20)) in pyridine (38 ml) were added trimethylchlorosilane (8.0 ml,
6.3 mmol) and hexamethyldisilazane (6.0 ml, 2.8 mmol), and stirred at room
temperature for overnight. The mixture was added to saturated aqueous
NaHCO3 and was extracted with ethyl acetate, washed with brine. The organic
phase was dried over Na2SO4, filtrated and concentrated under reduced
pressure. To the resulting residue were added methanol (45 ml) and 6 N acetic
acid (2.7 ml), and stirred at room temperature for 3 h. The mixture was added
to saturated aqueous NaHCO3 and concentrated under reduced pressure. The
resulting mixture was extracted with ethyl acetate, dried over Na2SO4, filtrated
and concentrated under reduced pressure. The resulting residue was purified by
silica gel column chromatography (hexane/ethyl acetate= 19/1 to 3/1) to afford
6a (5.56 g, 30% from ( )-4a) as a colorless solid. 1H NMR (400 MHz, CDCl3)
δ 6.40 (d, J = 9.2 Hz, 1H), 5.17 (d, J =5.5 Hz, 1H), 4.30–4.38 (m, 1H), 4.19 (dd,
J = 9.0, 6.3 Hz, 1H), 4.12 (dd, J = 9.5, 5.5 Hz, 1H), 4.07 (d, J =8.3 Hz, 1H),
3.93–4.02 (m, 1H), 3.90–3.93 (m, 1H), 3.62 (dd, J = 9.5, 2.6 Hz, 1H), 3.48–3.59
Methyl 6-N-[(2′R, 4′S)-1′-N-(tert-butoxycarbonyl)-4′-(n-propyl)
piperidine-2′-carbonyl]-2,3,4-tris-O-(trimethylsilyl)-α-
thiolincosaminide (6b′)
Compound 5b′ (1.00 g, 1.97 mmol), trimethylchlorosilane (1.26 ml,
9.87 mmol) and hexamethyldisilazane (2.07 ml, 9.87 mmol) in pyridine
(4.0 ml) were treated for 30 min according to the similar procedure as
described for the preparation of 6a and the crude tetrakis-O-trimethylsilyl
intermediate was treated with 6 N acetic acid (0.42 ml) in MeOH (10 ml) for
1 h according to the similar procedure as described for the preparation of 6a to
1
afford 6b′ (926 mg, 65% in 2 steps) as a colorless solid. H NMR (400 MHz,
(m, 1H), 3.31–3.40 (m, 1H), 2.83–2.89 (m, 1H), 2.05 (s, 3H), 1.99–2.03 (m, CDCl3) δ 6.56 (d, J = 8.9 Hz, 1H), 5.21 (d, J = 5.5 Hz, 1H), 4.24–4.31 (m, 1H),
1H), 1.78–1.89 (m, 1H), 1.57–1.63 (m, 1H), 1.47 (s, 9H), 1.29–1.39
(m, 2H), 1.20–1.29 (m, 1H), 1.17 (d, J = 6.4 Hz, 3H), 0.90 (t, J = 7.3 Hz,
3H), 0.19 (s, 9H), 0.13–0.16 (m, 18H); MS (ESI) m/z 709 (M+H)+.
4.11–4.20 (m, 2H), 4.08 (d, J = 8.1 Hz, 1H), 4.02–4.04 (m, 1H), 3.63 (dd,
J = 9.5, 2.6 Hz, 1H), 3.32–3.51 (m, 3H), 2.04 (s, 3H), 1.86–1.93 (m, 1H), 1.70–
1.85 (m, 2H), 1.44–1.49 (m, 10H), 1.21–1.38 (m, 5H), 1.15 (d, J = 6.5 Hz, 3H),
0.89 (t, J = 6.9 Hz, 3H), 0.19 (s, 9H), 0.15 (s, 9H), 0.14 (s, 9H); MS (ESI) m/z
723 (M+H)+.
Methyl 6-N-[(2′R, 4′S)-1′-N-(tert-butoxycarbonyl)-4′-(n-propyl)
piperidine-2′-carbonyl] -α-thiolincosaminide (5b′) and mixture 5b
of methyl 6-N-[(2′S, 4′R)-1′-N-(tert-butoxycarbonyl)-4′-(n-propyl)
Mixture 5c of methyl 6-N-[(2′S, 4′R)-1′-N-(tert-butoxycarbonyl)-4′-
piperidine-2′-carbonyl]-α-thiolincosaminide and methyl 6-N-[(2′R, (n-butyl)piperidine-2′-carbonyl]-α-thiolincosaminide and methyl 6-
The Journal of Antibiotics

Optimization of lincomycin derivatives
K Kumura et al
8
N-[(2′R, 4′S)-1′-N-(tert-butoxycarbonyl)-4′-(n-butyl)piperidine-2′-
carbonyl]-α-thiolincosaminide
the similar procedure to 7a. [α]D26 +83° (c 0.17, CH3OH); 1H NMR (400 MHz,
CD3OD) δ 8.09–8.13 (m, 1H), 7.77–7.86 (m, 3H), 5.29 (d, J = 5.6 Hz, 1H),
4.63–4.69 (m, 1H), 4.41–4.47 (m, 1H), 4.43 (d, J =10.2 Hz, 1H), 4.06–4.12 (m,
1H), 3.87–3.91 (m, 1H), 3.56 (dd, J = 10.2, 3.4 Hz, 1H), 3.25–3.31 (m, 1H),
3.19–3.25 (m, 1H), 3.08–3.18 (m, 1H), 2.58–2.68 (m, 1H), 1.99 (s, 3H), 1.65–
1.72 (m, 1H), 1.56 (d, J = 7.1 Hz, 3H), 1.24–1.34 (m, 5H), 0.98–1.11 (m, 2H),
0.85–0.95 (m, 3H); MS (FAB) m/z 628 (M+H)+; HRMS (ESI) m/z calcd for
C26H38N5O7S3 628.1928, found 628.1926 (M+H)+.
Compound
( )-4c (12.6 g, 44.2 mmol), 1-hydroxybenzotriazole (7.77 g,
57.5 mmol), N,N′-dicyclohexylcarbodiimide (11.0 g, 53.3 mmol) and methyl
α-thiolincosaminide (14.6 g, 57.5 mmol) in N,N′-dimethylformamide (120 ml)
were treated for 20 h according to the similar procedure as described for the
preparation of mixture 5a to afford methyl 6-N-[1′-N-(tert-butoxycarbonyl)-4′-
(n-butyl)piperidine-2′-carbonyl]-α-thiolincosaminide (20.0 g, 87%, (2′S, 4′R)
isomer: (2′R, 4′S) isomer= ca 50:50) as a colorless solid. To this colorless solid
(14.5 g) was added ethyl acetate and insoluble matter was filtrated off and ethyl
acetate solution was concentrated under reduced pressure to afford mixture 5c
(8.15 g, 80% de ((2′S, 4′R): (2′R, 4′S) = 90:10)) as a colorless solid. 1H NMR
(400 MHz, CDCl3) δ 6.85 (br s, 0.9H), 6.58 (d, J = 8.7 Hz, 0.1H), 5.30–5.34 (m,
1H), 4.64 (br s, 0.1H), 4.46 (br s, 0.9H), 3.93–4.25 (m, 6H), 3.51–3.63 (m, 2H),
3.28–3.38 (m, 1H), 2.80–2.98 (m, 2H), 2.14–2.16 (m, 3H), 1.93–2.02 (m, 1H),
1.68–1.86 (m, 3H), 1.54 (br s, 1H), 1.44–1.47 (m, 9H), 1.19–1.35 (m, 7H),
1.19–1.25 (m, 3H), 0.86–0.91 (m, 3H).
Methyl (7S)-7-deoxy-7-[5-(2-nitrophenyl)-1,3,4-thiadiazol-2-yl-
thio]- 6-N-[(2′R, 4′S)-4′-(n-propyl)piperidine-2-carbonyl]-α-
thiolincosaminide (7b′)
Reaction of 6b′ (200 mg, 0.277) mmol) with 5-(2-nitrophenyl)-1,3,4-thiadia-
zole-2-thiol (104 mg, 0.435 mmol) afforded 7b′ as a light yellow solid in 25%
yield by the similar procedure to 7a. [α]D +110° (c 0.21, CH3OH); 1H NMR
26
(400 MHz, CD3OD) δ 8.08–8.12 (m, 1H), 7.75–7.85 (m, 3H), 5.27 (d,
J = 5.9 Hz, 1 H), 4.66 (dd, J = 10.1, 2.5 Hz, 1H), 4.39–4.49 (m, 2H), 4.07–
4.13 (m, 1H), 3.83–3.85 (m, 1H), 3.56 (dd, J = 10.2, 3.3 Hz, 1H), 3.24–3.29 (m,
1H), 3.09–3.15 (m, 1H), 2.58–2.66 (m, 1H), 2.01 (s, 3H), 1.94–1.99 (m, 1H),
1.65–1.73 (m, 1H), 1.58 (d, J = 6.9 Hz, 3H), 1.18–1.42 (m, 5H), 0.99–1.12 (m,
2H), 0.90 (t, J = 7.2 Hz, 3H); MS (FAB) m/z 628 (M+H)+; HRMS (ESI) m/z
calcd for C26H38N5O7S3 628.1928, found 628.1921 (M+H)+.
Methyl 6-N-[(2′S, 4′R)-1′-N-(tert-butoxycarbonyl)-4′-(n-butyl)
piperidine-2′-carbonyl]-2,3,4-tris-O-(trimethylsilyl)-α-
thiolincosaminide (6c)
Mixture 5c (8.15 g, 15.7 mmol, 80% de ((2′S, 4′R): (2′R, 4′S) = 90:10),
trimethylchlorosilane (100 ml, 78.3 mmol) and hexamethyldisilazane
(16.4 ml, 78.3 mmol) in pyridine (30 ml) were treated for 20 min according
to the similar procedure as described for the preparation of 6a and the crude
tetrakis-O-trimethylsilyl intermediate and 6 N acetic acid (3.4 ml) in MeOH
(88 ml) were treated for 40 min according to the similar procedure as described
for the preparation of 6a to afford 6c (8.20 g, 71% in 2 steps from
diastereomeric mixture 5c) as a colorless solid. 1H NMR (400 MHz, CDCl3)
δ 6.34 (d, J =9.3 Hz, 1H), 5.17 (d, J = 5.5 Hz, 1H), 4.30–4.36 (m, 1H), 4.09–
4.15 (m, 2H), 4.05 (d, J = 8.3 Hz, 1H), 3.95–4.03 (m, 1H), 3.88–3.90 (m, 1H),
3.61 (dd, J = 9.5, 2.6 Hz, 1H), 3.43–3.44 (m, 1H), 3.32–3.44 (m, 1H), 2.96 (d,
J = 6.5 Hz, 1H), 2.05 (s, 3H), 2.00–2.04 (m, 1H), 1.79–1.89 (m, 1H), 1.49–1.87
(m, 1H), 1.46 (s, 9H), 1.19–1.33 (m, 7H), 1.16 (d, J = 6.4 Hz, 3H), 0.85–0.92
(m, 3H), 0.17–0.19 (m, 9H), 0.12–0.15 (m, 18H); MS (ESI) m/z 737 (M+H)+.
Methyl (7S)-6-N-[(2′S, 4′R)-4′-(n-butyl)piperidine-2′-carbonyl]-7-
deoxy-7-[5-(2-nitrophenyl)-1,3,4-thiadiazol-2-yl-thio]-α-
thiolincosaminide (7c)
Reaction of 6c (500 mg, 0.678 mmol) with 5-(2-nitrophenyl)-1,3,4-thiadiazole-
2-thiol (211 mg, 0.882 mmol) afforded 7c as a colorless solid in 21% yield by
the similar procedure to 7a. [α]D25 +93° (c 0.48, CH3OH); 1H NMR (400 MHz,
CD3OD) δ 8.08–8.12 (m, 1H), 7.76–7.87 (m, 3H), 5.29 (d, J = 5.6 Hz, 1H), 4.68
(dd, J =10.1, 2.3 Hz, 1H), 4.46 (dd, J = 6.8, 2.4 Hz, 1H), 4.42 (d, J =10.2 Hz,
1H), 4.11 (dd, J =10.2, 5.6 Hz, 1H), 3.88–3.91 (m, 1H), 3.59–3.63 (m, 1H),
3.57 (dd, J =10.2, 3.2 Hz, 1H), 3.38 (dd, J = 11.9, 2.9 Hz, 1H), 3.15–3.22 (m,
1H), 2.63–2.72 (m, 1H), 1.99 (s, 3H), 1.68–1.76 (m, 1H), 1.52–1.58 (m, 4H),
1.24–1.34 (m, 6H), 1.02–1.17 (m, 3H), 0.84–0.92 (m, 3H); MS (FAB) m/z 642
(M+H)+; HRMS (ESI) m/z calcd for C27H40N5O7S3 642.2084, found 642.2092
(M+H)+.
Methyl (7S)-7-deoxy-6-N-[(2′S, 4′R)-4′-ethylpiperidine-2′-
carbonyl]-7-[5-(2-nitrophenyl)-1,3,4-thiadiazol-2-yl-thio]-α-
thiolincosaminide (7a)
Methyl (7S)-7-deoxy-6-N-[(2′S, 4′R)-4′-ethylpiperidine-2′-
carbonyl]-7-[5-(4-fluoro-2-nitrophenyl)-1,3,4-thiadiazol-2-yl-thio]-
α-thiolincosaminide (7d)
To a solution of 6a (270 mg, 0.381 mmol) in tetrahydrofuran (5 ml) at 0 °C
were added triphenylphosphine (200 mg, 0.762 mmol) and diethlazodicarbox-
ylate (0.150 ml, 0.823 mmol), and stirred at 0 °C for 10 min, and 5-(2-
nitrophenyl)-1,3,4-thiadiazole-2-thiol (200 mg, 0.836 mmol) was added and
stirred at room temperature for 3 h. The mixture was concentrated under
reduced pressure and added methanol (10 ml), 5 N hydrochloric acid (0.1 ml)
and stirred at room temperature for 1 h. The mixture was concentrated under
reduced pressure. To the resulting residue was added trifluoroacetic acid
(3.0 ml) and stirred at room temperature for 30 min. The mixture was
concentrated under reduced pressure and the resulting residue was purified
by preparative TLC (CHCl3/CH3OH/28% aq NH4OH= 20/1/0.1) to afford 7a
Reaction of 6a (180 mg, 0.253 mmol) with 5-(4-fluoro-2-nitrophenyl)-1,3,4-
thiadiazole-2-thiol (80.0 mg, 311 mmol) afforded 7d as a light yellow solid in
39% yield by the similar procedure to 7a. [α]D +89° (c 0.53, CH3OH); 1H
25
NMR (400 MHz, CD3OD) δ 7.98 (dd, J =8.3, 2.5 Hz, 1H), 7.85 (dd, J = 8.7,
5.3 Hz, 1H), 7.64 (ddd, J = 8.7, 7.7, 2.5 Hz, 1H), 5.27 (d, J = 5.6 Hz, 1H), 4.67
(dd, J = 10.0, 2.4 Hz, 1H), 4.46 (qd, J = 6.8, 2.4 Hz, 1H), 4.41 (dd, J = 10.1,
0.9 Hz, 1H), 4.10 (dd, J = 10.3, 5.9 Hz, 1H), 3.88 (dd, J = 3.2, 0.9 Hz, 1H), 3.55
(dd, J = 10.3, 3.2 Hz, 1H), 3.26–3.30 (m, 1H), 3.14–3.20 (m, 1H), 2.64 (td,
J = 12.8, 2.8 Hz, 1H), 1.99 (s, 3H), 1.95–1.98 (m, 1H), 1.68–1.75 (m, 1H), 1.56
(d, J =6.8 Hz, 3H), 1.37–1.50 (m, 1H), 1.26–1.35 (m, 2H), 1.00–1.11 (m, 2H),
0.92 (t, J = 7.5 Hz, 3H); MS (FAB) m/z 632 (M+H)+; HRMS (ESI) m/z calcd for
C25H35FN5O7S3 632.1677, found 632.1674 (M+H)+.
(52.5 mg, 22%) as colorless solid. [α]D +100° (c 1.3, CH3OH); 1H NMR
25
(400 MHz, CD3OD) δ 8.10 (d, J = 7.6 Hz, 1H), 7.76–7.86 (m, 3H), 5.28 (d,
J = 5.6 Hz, 1H), 4.67 (dd, J = 10.1, 2.5 Hz, 1H), 4.46 (qd, J = 6.8, 2.5 Hz, 1H),
4.38–4.43 (m, 1H), 4.07–4.12 (m, 1H), 3.87–3.89 (m, 1H), 3.56 (dd, J = 10.4,
3.3 Hz, 1H), 3.26–3.31 (m, 1H), 3.13–3.20 (m, 1H), 2.56–2.67 (m, 1H), 1.99 (s,
3H), 1.95–1.98 (m, 1H), 1.68–1.75 (m, 1H), 1.56 (d, J = 6.8 Hz, 3H), 1.36–1.50
(m, 1H), 1.25–1.34 (m, 2H), 0.98–1.11 (m, 2H), 0.89–0.95 (m, 3H); MS (FAB)
m/z 614 (M+H)+; HRMS (ESI) m/z calcd for C25H36N5O7S3 614.1771, found
614.1768 (M+H)+.
Methyl (7S)-7-deoxy-6-N-[(2′S, 4′R)-4-ethyl-1′-N-methylpiperidine-
2′-carbonyl]-7-[5-(4-fluoro-2-nitrophenyl)-1,3,4-thiadiazol-2-yl-
thio]-α-thiolincosaminide (8d)
To a solution of compound 7d (52 mg, 0.082 mmol) in MeOH (3 ml) at 0 oC
were added 36% aqueous formaldehyde (100 μl, 1.2 mmol), acetic acid (50 μl,
0.79 mmol) and NaBH(OAc)3 (120 mg, 0.57 mmol) and stirred at room
temperature for 4 h. The mixture was concentrated under reduced pressure.
Ethyl acetate was added to the residue and washed with saturated aqueous
NaHCO3. The organic phase was dried over MgSO4, filtrated and concentrated
Methyl (7S)-7-deoxy-7-[5-(2-nitrophenyl)-1,3,4-thiadiazol-2-yl-
thio]-6-N-[(2′S, 4′R)-4′-(n-propyl)piperidine-2′-carbonyl]-α-
thiolincosaminide (7b)
Reaction of 6b (200 mg, 0.277 mmol) with 5-(2-nitrophenyl)-1,3,4-thiadiazole- under reduced pressure. The resulting residue was purified by preparative TLC
2-thiol (114 mg, 0.476 mmol) afforded 7b as a colorless solid in 24% yield by (CHCl3/MeOH/28% aq NH4OH= 10/1/0.1) to afford 8d (41 mg, 77%) as a
The Journal of Antibiotics

Optimization of lincomycin derivatives
K Kumura et al
9
light yellow solid. [α]D25 +80° (c 0.92, CH3OH); 1H NMR (400 MHz, CD3OD) 1.83–1.92 (m, 1H), 1.67–1.76 (m, 1H), 1.57 (d, J = 7.1 Hz, 3H), 1.21–1.42 (m,
9H), 0.85–0.93 (m, 3H); MS (FAB) m/z 674 (M+H)+; HRMS (ESI) m/z calcd
δ 7.98 (dd, J = 8.3, 2.6 Hz, 1H), 7.85 (dd, J = 8.7, 5.3 Hz, 1H), 7.61–7.67 (m,
1H), 5.28 (d, J =5.6 Hz, 1H), 4.69 (dd, J = 10.1, 2.6 Hz, 1H), 4.48 (qd, J = 6.9,
2.6 Hz, 1H), 4.43 (dd, J = 10.1, 0.8 Hz, 1H), 4.12 (dd, J = 10.2, 5.6 Hz, 1H),
3.83–3.87 (m, 1H), 3.57 (dd, J = 10.2, 2.9 Hz, 1H), 2.93–3.99 (m, 1H), 2.58–
2.64 (m, 1H), 2.25 (s, 3H), 2.06–2.15 (m, 1H), 1.98–2.01 (m, 3H), 1.85–1.91
(m, 1H), 1.69–1.76 (m, 1H), 1.58 (d, J = 6.9 Hz, 3H), 1.23–1.34 (m, 5H), 0.87–
0.94 (m, 3H); MS (FAB) m/z 646 (M+H)+; HRMS (ESI) m/z calcd for
C27H39FN5O7S3 646.1834, found 646.1833 (M+H)+.
for C28H41FN5O7S3 674.2147, found 674.2160 (M+H)+.
Methyl (7S)-7-deoxy-7-[5-(5-methylamino-2-nitrophenyl)-1,3,4-
thiadiazol-2-yl-thio]-6-N-[(2′S, 4′R)-4′-(n-propyl)piperidine-2′-
carbonyl]-α-thiolincosaminide (7g)
Reaction of 6b (200 mg, 0.277 mmol) with 5-(5-methylamino-2-nitrophenyl)-
1,3,4-thiadiazole-2-thiol (96.6 mg, 0.360 mmol) afforded 7 g as a yellow solid in
26% yield by the similar procedure to 7a. [α]D +91° (c 0.41, CH3OH); 1H
24
Methyl (7S)-7-deoxy-7-[5-(4-fluoro-2-nitrophenyl)-1,3,4-thiadiazol-
2-yl-thio]-6-N-[(2′S, 4′R)-4′-(n-propyl)piperidine-2′-carbonyl]-α-
thiolincosaminide (7e)
Reaction of 6b (2.80 g, 3.87 mmol) with 5-(4-fluoro-2-nitrophenyl)-1,3,4-
thiadiazole-2-thiol (1.19 mg, 4.59 mmol) afforded 7e as a light yellow solid
NMR (300 MHz, CDCl3) δ 8.16 (d, J = 8.7 Hz, 1H), 6.62–6.72 (m, 2H), 5.33
(d, J =5.7 Hz, 1H), 4.46–4.53 (m, 1H), 4.31 (d, J = 9.9 Hz, 1H), 4.11–4.25 (m,
2H), 3.87–3.91 (m, 1H), 3.56–3.68 (m, 1H), 3.37–3.46 (m, 1H), 3.16–3.24 (m,
1H), 2.91 (s, 3H), 2.68–2.90 (m, 2H), 2.61–2.68 (m, 1H), 2.19 (s, 3H), 2.00–
2.09 (m, 1H), 1.64–1.72 (m, 1H), 1.51 (d, J = 6.9 Hz, 3H), 1.16–1.36 (m, 4H),
in 39% yield by the similar procedure to 7a except for using toluene as a solvent
of Mitunobu reaction. [α]D +93° (c 0.20, CH3OH); 1H NMR (400 MHz, 0.98–1.12 (m, 2H), 0.79–0.89 (m, 3H); MS (FAB) m/z 657 (M+H)+; HRMS
26
(ESI) m/z calcd for C27H41N6O7S3 657.2193, found 657.2193 (M+H)+.
CD3OD) δ 7.99 (dd, J = 8.3, 2,7 Hz, 1H), 7.85 (dd, J = 8.6, 5.2 Hz, 1H), 7.60–
7.69 (m, 1H), 5.27 (d, J = 5.6 Hz, 1H), 4.66 (dd, J = 10.1, 2.6 Hz, 1H), 4.43–
4.50 (m, 1H), 4.41 (d, J = 10.1 Hz, 1H), 4.10 (dd, J = 10.3, 5.6 Hz, 1H), 3.85–
3.90 (m, 1H), 3.55 (dd, J = 10.3, 3.3 Hz, 1H), 3.12–3.19 (m, 1H), 2.57–2.67 (m,
1H), 1.99 (s, 3H), 1.92–1.97 (m, 1H), 1.65–1.74 (m, 1H), 1.56 (d, J = 6.8 Hz,
3H), 1.19–1.42 (m, 5H), 0.99–1.12 (m, 2H), 0.90 (t, J = 7.2 Hz, 3H); MS (FAB)
m/z 646 (M+H)+; HRMS (ESI) m/z calcd for C26H37FN5O7S3 646.1834, found
646.1836 (M+H)+.
Methyl (7S)-7-deoxy-7-[5-(5-methoxy-2-nitrophenyl)-1,3,4-
thiadiazol-2-yl-thio]-6-N-[(2′S, 4′R)-4′-(n-propyl)piperidine-2′-
carbonyl]-α-thiolincosaminide (7h)
Reaction of 6b (200 mg, 0.277 mmol) with 5-(5-methoxy-2-nitrophenyl)-1,3,4-
thiadiazole-2-thiol (97.0 mg, 0.360 mmol) afforded 7h as a light yellow solid in
24
24% yield by the similar procedure to 7a. [α]D +79° (c 0.12, CH3OH); 1H
NMR (300 MHz, CDCl3) δ 8.11–8.20 (m, 1H), 7.07–7.16 (m, 2H), 6.62–6.72
(m, 2H), 5.36 (d, J = 5.7 Hz, 1H), 4.47–4.53 (m, 1H), 4.09–4.35 (m, 3H), 3.94
(s, 3H), 3.77–3.89 (m, 1H), 3.55–3.70 (m, 1H), 3.36–3.51 (m, 1H), 3.16–3.29
(m, 1H), 2.65–2.79 (m, 2H), 2.15 (s, 3H), 1.98–2.09 (m, 1H), 1.64–1.73 (m,
1H), 1.52 (d, J = 6.9 Hz, 3H), 1.17–1.36 (m, 4H), 0.98–1.13 (m, 2H), 0.77–0.89
(m, 3H); MS (FAB) m/z 658 (M+H)+; HRMS (ESI) m/z calcd for
Methyl (7S)-7-deoxy-7-[5-(4-fluoro-2-nitrophenyl)-1,3,4-thiadiazol-
2-yl-thio]-6-N-[(2′S, 4′R)-1′-N-methyl-4′-(n-propyl)piperidine-2′-
carbonyl]-α-thiolincosaminide (8e)
The title compound was synthesized from 7e (55 mg, 0.086 mmol) as a light
26
yellow solid in 37% yield by the similar procedure to 8d. [α]D +88° (c 0.17,
CH3OH); 1H NMR (400 MHz, CD3OD) δ 7.99 (dd, J = 5.2 Hz, 1H), 7.85
(dd, J = 8.9, 5.2 Hz, 1H), 7.61–7.67 (m, 1H), 5.28 (d, J = 5.6 Hz, 1H), 4.69 C27H40N5O8S3 658.2034, found 658.2038 (M+H)+.
(dd, J = 10.2, 2.4 Hz, 1H), 4.45–4.52 (m, 1H), 4.43 (d, J = 10.2 Hz, 1H), 4.12
(dd, J = 10.2, 5.7 Hz, 1H), 3.84–3.86 (m, 1H), 3.57 (dd, J = 10.2, 3.2 Hz, 1H),
2.92–3.00 (m, 1H), 2.57–2.65 (m, 1H), 2.25 (s, 3H), 2.10–2.18 (m, 1H), 2.00 (s,
Methyl (7S)-7-deoxy-6-N-[(2′S, 4′R)-4′-ethylpiperidine-2′-
carbonyl]-7-[5-(4,5-dimethoxy-2-nitrophenyl)-1,3,4-thiadiazol-2-yl-
3H), 1.83–1.90 (m, 1H), 1.68–1.74 (m, 1H), 1.57 (d, J = 7.6 Hz, 3H), 1.20–1.40
(m, 7H), 0.86–0.92 (m, 3H); MS (FAB) m/z 660 (M+H)+; HRMS (ESI) m/z
thio]-α-thiolincosaminide (7i)
Reaction of 6a (158 mg, 0.223 mmol) with 5-(4,5-dimethoxy-2-nitrophenyl)-
calcd for C27H39N5O7S3 660.1990, found 660.1995 (M+H)+.
1,3,4-thiadiazole-2-thiol (80.0 mg, 0.267 mmol) afforded 7i as a light yellow
25
solid in 11% yield by the similar procedure to 7a. [α]D +89° (c 0.46,
Methyl (7S)-6-N-[(2′S, 4′R)-4′-(n-butyl)piperidine-2′-carbonyl]-7-
deoxy-7-[5-(4-fluoro-2-nitrophenyl)-1,3,4-thiadiazol-2-yl-thio]-α-
thiolincosaminide (7f)
1
CH3OH); H NMR (400 MHz, CD3OD) δ 7.75 (s, 1H), 7.21 (s, 1H), 5.28 (d,
J = 5.6 Hz, 1H), 4.67 (dd, J = 10.0, 2.4 Hz, 1H), 4.40–4.48 (m, 2H), 4.10 (dd,
J = 10.3, 5.6 Hz, 1H), 3.98 (s, 3H), 3.96 (s, 3H), 3.88–3.91 (m, 1H), 3.56 (dd,
J = 10.3, 3.4 Hz, 1H), 3.14–3.20 (m, 1H), 2.64 (td, J = 12.9, 2.7 Hz, 1H), 2.01 (s,
3H), 1.98 (br s, 1H), 1.69–1.75 (m, 1H), 1.55 (d, J = 6.8 Hz, 3H), 1.39–1.49 (m,
1H), 1.24–1.34 (m, 2H), 1.00–1.12 (m, 2H), 0.92 (t, J =7.3 Hz, 3H); MS (FAB)
m/z 674 (M+H)+; HRMS (ESI) m/z calcd for C27H40N5O9S3 674.1983, found
Reaction of 6c (500 mg, 0.678 mmol) with 5-(4-fluoro-2-nitrophenyl)-1,3,4-
thiadiazole-2-thiol (224 mg, 0.882 mmol) afforded 7f as a light yellow solid in
26
1
30% yield by the similar procedure to 7a. [α]D +100° (c 0.27, CH3OH); H
NMR (400 MHz, CD3OD) δ 7.98 (dd, J = 8.2, 2,6 Hz, 1H), 7.85 (dd, J = 8.6,
5.2 Hz, 1H), 7.60–7.68 (m, 1H), 5.28 (d, J = 5.6 Hz, 1H), 4.67 (dd, J = 10.2,
2.4 Hz, 1H), 4.43–4.51 (m, 1H), 4.41 (d, J = 10.2 Hz, 1H), 4.10 (dd, J = 10.2, 674.1988 (M+H)+.
5.6 Hz, 1H), 3.87–3.91 (m, 1H), 3.56 (dd, J = 10.2, 3.2 Hz, 1H), 3.32–3.36 (m,
1H), 3.14–3.21 (m, 1H), 2.61–2.71 (m, 1H), 2.00–2.04 (m, 1H), 1.99 (s, 3H),
Methyl (7S)-7-deoxy-7-[5-(4,5-dimethoxy-2-nitrophenyl)-1,3,4-
1.68–1.75 (m, 1H), 1.56 (d, J = 7.1 Hz, 3H), 1.23–1.34 (m, 6H), 0.99–1.14 (m,
2H), 0.86–0.91 (m, 3H); MS (FAB) m/z 660 (M+H)+; HRMS (ESI) m/z calcd
for C27H39FN5O7S3 660.1990, found 660.1994 (M+H)+.
thiadiazol-2-yl-thio]-6-N-[(2′S, 4′R)-4′-(n-propyl)piperidine-2′-
carbonyl]-α-thiolincosaminide (7j)
Reaction of 6b (200 mg, 0.277 mmol) with 5-(4,5-dimethoxy-2-nitrophenyl)-
1,3,4-thiadiazole-2-thiol (99.4 mg, 0.332 mmol) afforded 7j as a light yellow
Methyl (7S)-6-N-[(2′S, 4′R)-4′-(n-butyl)-1′-N-methylpiperidine-2′-
carbonyl]-7-deoxy-7-[5-(4-fluoro-2-nitrophenyl)-1,3,4-thiadiazol-2-
yl-thio]-α-thiolincosaminide (8f)
26
solid in 10% yield by the similar procedure to 7a. [α]D +97° (c 0.30,
1
CH3OH); H NMR (400 MHz, CD3OD) δ 7.77 (s, 1H), 7.22 (s, 1H), 5.28 (d,
J = 5.6 Hz, 1H), 4.67 (dd, J = 10.2, 2.4 Hz, 1H), 4.39–4.48 (m, 2H), 4.10 (dd,
J = 10.2, 5.6 Hz, 1H), 3.99 (s, 3H), 3.96 (s, 3H), 3.87–3.90 (m, 1H), 3.56 (dd,
J = 10.2, 3.0 Hz, 1H), 3.32–3.38 (m, 1H), 3.15–3.20 (m, 1H), 2.63–2.71 (m,
1H), 2.02 (s, 3H), 1.97–2.01 (m, 1H), 1.68–1.75 (m, 1H), 1.55 (d, J = 7.1 Hz,
3H), 1.31–1.40 (m, 2H), 1.20–1.28 (m, 2H), 1.02–1.15 (m, 3H), 0.90 (t,
J = 7.2 Hz, 3H); MS (FAB) m/z 688 (M+H)+; HRMS (ESI) m/z calcd for
The title compound was synthesized from 7f (72 mg, 0.11 mmol) as a light
26
yellow solid in 85% yield by the similar procedure to 8d. [α]D +94° (c 0.22,
1
CH3OH); H NMR (400 MHz, CD3OD) δ 7.98 (dd, J = 8.2, 2,6 Hz, 1H), 7.85
(dd, J = 8.6, 5.2 Hz, 1H), 7.60–7.68 (m, 1H), 5.28 (d, J = 5.6 Hz, 1H), 4.70 (dd,
J = 10.1, 2.7 Hz, 1H), 4.45–4.53 (m, 1H), 4.43 (d, J = 10.1 Hz, 1H), 4.12 (dd,
J = 10.2, 5.6 Hz, 1H), 3.82–3.87 (m, 1H), 3.57 (dd, J = 10.2, 3.3 Hz, 1H), 2.93–
3.01 (m, 1H), 2.62–2.68 (m, 1H), 2.27 (s, 3H), 2.09–2.18 (m, 1H), 2.00 (s, 3H), C28H42N5O9S3 688.2139, found 688.2153 (M+H)+.
The Journal of Antibiotics

Optimization of lincomycin derivatives
K Kumura et al
10
for biological studies; and Ms. M Takagi for manuscript. We also thank Ms. M
Ishii for direction in intellectual properties.
Methyl (7S)-6-N-[(2′S, 4′R)-4′-(n-butyl)piperidine-2′-carbonyl]-7-
deoxy-7-[5-(4,5-dimethoxy-2-nitrophenyl)-1,3,4-thiadiazol-2-yl-
thio]-α-thiolincosaminide (7k)
Reaction of 6c (200 mg, 0.271 mmol) with 5-(4,5-dimethoxy-2-nitrophenyl)-
1,3,4-thiadiazole-2-thiol (106 mg, 0.353 mmol) afforded 7k as a light yellow
1
2
Morimoto, S., Takahashi, Y., Watanabe, Y. & Ōmura, S. Chemical modification of
erythromycins. I. Synthesis and antibacterial activity of 6-O-methylerythromycins A. J.
Antibiot. 37, 187–189 (1984).
Slobodan, D. 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).
26
solid in 19% yield by the similar procedure to 7a. [α]D +96° (c 0.49,
1
CH3OH); H NMR (400 MHz, CD3OD) δ 7.75 (s, 1H), 7.21 (s, 1H), 5.28 (d,
J = 5.7 Hz, 1H), 4.63–4.69 (m, 1H), 4.38–4.47 (m, 2H), 4.10 (dd, J = 10.1,
5.7 Hz, 1H), 3.98 (s, 3H), 3.96 (s, 3H), 3.87–3.90 (m, 1H), 3.54–3.58 (m, 1H),
3.27–3.29 (m, 1H), 3.12–3.18 (m, 1H), 2.58–2.67 (m, 1H), 2.01 (s, 3H), 1.92–
2.00 (m, 1H), 1.65–1.74 (m, 1H), 1.55 (d, J = 6.8 Hz, 3H), 1.46–1.52 (m, 1H),
1.20–1.34 (m, 6H), 0.99–1.11 (m, 2H), 0.86–0.93 (m, 3H); MS (FAB) m/z 702
(M+H)+; HRMS (ESI) m/z calcd for C29H44N5O9S3 702.2296, found 702.2294
(M+H)+.
3
4
Ajito, K., Miura, T., Furuuchi, T. & Tamura, A. Sixteen-membered macrolides: chemical
modifications and future applications. Heterocycles 89, 281–352 (2014).
Sato, T. et al. In vitro antibacterial activity of modithromycin, a novel 6,11-bridged
bicyclolide, against respiratory pathogens, including macrolide-resistant Gram-
positive cocci. Antimicrob. Agents Chemother. 55, 1588–1593 (2011).
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potent against erythromycin-resistant and susceptible pathogens. Bioorg. Med. Chem.
Lett. 9, 3075–3080 (1999).
5
Methyl 7-deoxy-7-methyl-6-N-[(2′S, 4′R)-4′-(n-propyl)piperidine-
2′-carbonyl]-α-thiolincosaminide (VIC-105555) and methyl 7-
deoxy-7-methyl-6-N-[(2′R, 4′S)-4′-(n-propyl)piperidine-2′-
carbonyl]-α-thiolincosaminide (10)
6
7
Clay, K. D. et al. Severe hepatotoxicity of telithromycin: three case reports and
literature review. Ann. Intern. Med. 144, 415–420 (2006).
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).
Miura, T. et al. Novel azalides derived from 16-membered macrolides. III. Azalides
modified at the C-15 and 4” positions: improved antibacterial activities. Bioorg. Med.
Chem. 18, 2735–2747 (2010).
8
9
To a solution of compound 9 (1.36 g, 3.41 mmol) in MeOH-H2O (5:2, 100 ml)
were added conc. hydrochloric acid (410 μl, 4.90 mmol), platinum (IV) oxide
(1.16 g, 5.12 mmom) and stirred under a hydrogen pressure of 3.9 MPa at
room temperature for 24 h. The mixture was filtered and concentrated under
reduced pressure. The resulting residue was added saturated aqueous NaHCO3
and extracted with ethyl acetate. The organic phase was dried over Na2SO4,
filtered and concentrated under reduced pressure. The resulting residue was
purified by silica gel column chromatography (CHCl3/MeOH/28% aq
NH4OH= 95/5/0.5 to 85/15/1.5), to afford the title compounds as colorless
solids (VIC-105555; more polar, 630 mg, 46%: 10; less polar, 653 mg, 47%).
Mason, D. J., Dietz, A. & Deboer, C. Lincomycin, a new antibiotic I. Discovery and
biological properties. Antimicrob. Agents Chemother. 1962, 554–559 (1962).
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11 Weisblum, B. Erythromycin resistance by ribosome modification. Antimicrob. Agents
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12 Tsuzuki, K. et al. Motilides, macrolides with gastrointestinal motor stimulating activity.
I. O-substituted and tertiary N-substituted derivatives of 8,9-anhydroerythromycin A
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13 Shah, P. J., Vakil, N.
& Kabakov, A. Role of intravenous immune globulin in
streptococcal toxic shock syndrome and Clostridium difficile infection. Am. J. Health
Syst. Pharm. 72, 1013–1019 (2015).
26
1
VIC-105555: [α]D +170° (c 0.91, CH3OH); H NMR (400 MHz, CD3OD) δ
5.24 (d, J = 5.6 Hz, 1H), 4.16 (d, J = 10.0, 3.1 Hz, 1H), 4.08 (dd, J = 10.3,
5.6 Hz, 1H), 4.04 (d, J = 10.0 Hz, 1H), 3.79–3.81 (m, 1H), 3.51 (dd, J = 10.3,
3.2 Hz, 1H), 3.24–3.29 (m, 1H), 3.10–3.16 (m, 1H), 2.62 (td, J = 12.8, 2.8 Hz,
1H), 2.12–2.20 (m, 1H), 2.11 (s, 3H), 1.89–1.96 (m, 1H), 1.66–1.73 (m, 1H),
1.46–1.57 (m, 1H), 1.32–1.41 (m, 2H), 1.21–1.28 (m, 2H), 0.98–1.10 (m, 2H),
0.89–0.96 (m, 9H); MS (FAB) m/z 405 (M+H)+; HRMS (ESI) m/z calcd for
14 Sztaricskai, F. et al. Semisynthetic modification of antibiotic lincomycin. J. Antibiot.
49, 941–943 (1996).
15 Goffic, L. F. Structure activity relationships in lincosamide and streptogramin anti-
biotics. J. Antimicrob. Chemother. 16(Suppl A), 13–21 (1985).
16 Umemura, E. et al. Synthesis of novel lincomycin derivatives and their in vitro
antibacterial activities. J. Antibiot. 66, 195–198 (2013).
17 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).
18 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).
19 Wakiyama, Y. et al. Synthesis and structure-activity relationships of novel lincomycin
derivatives part 3: discovery of the 4-(pyrimidin-5-yl)phenyl group in synthesis of 7(S)-
thiolincomycin analogs. J. Antibiot. 70, 52–64 (2017).
20 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).
21 Kumura, K. et al. Synthesis and antibacterial activity of novel lincomycin derivatives. II.
Synthesis and antibacterial activity of novel lincomycin derivatives. II. Exploring (7S) -7-
(5-aryl-1,3,4-thiadiazol-2-yl-thio)-7-deoxylincomycin derivatives. J. Antibiot. 70,
655–663 (2017).
22 Kumura, K. et al. Synthesis and antibacterial activity of novel lincomycin derivatives. III.
Optimization of a phenyl thiadiazole moiety. J. Antibiot. doi:10.1038/ja.2017.59 (2017).
23 Birkenmeyer, R. D., Kroll, S. J., Lewis, C., Stern, K. F. & Zurenko, G. E. Synthesis and
antimicrobial activity of clindamycin analogues: pirlimycin, a potent antibacterial agent.
J. Med. Chem. 27, 216–223 (1984).
24 Lewis, J. G. et al. The lincomycin derivatives possessing antibacterial activity. WO/
2004/016632 A2, 26 February (2004).
25 Lewis, J. G. et al. Novel Antimicrobial 7-Methyl Lincosamides: Pipecolamide Analogs.
43rd Interscience Conference on Antimicrobial Agents and Chemotherapy. Poster
F-1389 (2004).
26
C19H37N2O5S 405.2418, found 405.2422 (M+H)+. 10: [α]D +200° (c 1.2,
1
CH3OH); H NMR (400 MHz, CD3OD) δ 5.25 (d, J = 5.7 Hz, 1H), 4.14 (dd,
J = 9.9, 3.6 Hz, 1H), 4.09 (dd, J = 10.2, 5.7 Hz, 1H), 4.06 (d, J = 9.9 Hz, 1H),
3.76–3.79 (m, 1H), 3.52 (dd, J = 10.2, 3.5 Hz, 1H), 3.24 (dd, J = 11.6, 2.8 Hz,
1H), 3.08–3.14 (m, 1H), 2.61 (td, J = 12.7, 2.7 Hz, 1H), 2.12–2.19 (m, 1H), 2.11
(s, 3H), 1.93–1.99 (m, 1H), 1.65–1.72 (m, 1H), 1.42–1.55 (m, 1H), 1.31–1.42
(m, 2H), 1.20–1.29 (m, 2H), 0.96–1.11 (m, 2H), 0.88–0.96 (m, 9H); MS (FAB)
m/z 405 (M+H)+; HRMS (ESI) m/z calcd for C19H37N2O5S 405.2418, found
404.2423 (M+H)+.
In vitro antibacterial activity
MIC 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 CFU ml−1 was inoculated into sensitivity disk agar (Nissui Pharmaceutical)
supplemented with 5% horse blood and incubated at 37 °C for 20 h. Then, MIC
was defined as the lowest drug concentration that prevented visible growth.
CONFLICT OF INTEREST
The authors declare no conflict of interest.
26 Lopez, S. L. et al. Characterization of the Spectrum of In Vitro Activity of VIC-105555, a
New Lincosamide. 44th Interscience Conference on Antimicrobial Agents and Che-
motherapy. Poster F-2038 (2004).
27 O’Dowd, H. et al. Novel antibacterial azetidine lincosamides. Bioorg. Med. Chem. Lett
18, 2645–2648 (2008).
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. Y Takayama
28 Shuman, R. T., Ornstein, P. L., Paschal, J. W. & Gesellchen, P. D. An improved
synthesis of homoproline and derivatives. J. Org. Chem. 55, 738–741 (1990).
29 Schroeder, W., Bannister, B.
& Hoeksema, H. Lincomycin. III. The structure and
stereochemistry of the carbohydrate moiety. J. Am. Chem. Soc. 89, 2448–2453 (1967).
30 Eldere, J. V. et al. Overview of antimicrobial options for Mycoplasma pneumoniae
pneumonia: focus on macrolide resistance. Clin. Respir. J. 11, 419–429 (2017).
The Journal of Antibiotics