Total Synthesis of Nucleoside Antibiotics Amicetin, Plicacetin, and Cytosaminomycin A—D

Article abstract of DOI:10.1002/cjoc.202100284

Amicetin and congeners constitute a small family of complex pyrimidine nucleosides, which exhibit strong antibiotic activities against Gram-positive bacteria and notably against strains of Mycobacterium tuberculosis. Herein, we report chemical synthesis of a series of disaccharide congeners of the amicetin family, including amicetin, plicacetin, and cytosaminomycin A—D. It is the first time for successful synthesis of amicetin, the prototypical member, and cytosaminomycins. The synthetic approach employs glycosyl N-phenyltrifluoroacetimidate and thioglycoside donors to construct the characteristic aminodeoxydisaccharides consisting of α-(1→4)-glycosidic linkage, uses gold(I)-catalyzed N-glycosylation to furnish 2-deoxy-β-nucleosides, and finally exploits amidation and global deprotection to complete the syntheses. It is noteworthy that the 3-O-protecting group in the 2-deoxydisaccharide donors is found to be crucial for a successful N-glycosylation to assemble the cytosaminomycin disaccharide nucleosides.

Full text of DOI:10.1002/cjoc.202100284

Chinese Journal
of Chemistry
CJC
中 国 化 学 - An International Journal
Accepted Article
Title: Total Synthesis of Nucleoside Antibiotics Amicetin, Plicacetin, and
Cytosaminomycin A-D
Authors: Jiqiang Fu, Peng Xu,* and Biao Yu*
This manuscript has been accepted and appears as an Accepted Article online.
This work may now be cited as: Chin. J. Chem. 2021, 39, 10.1002/cjoc.202100284.
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Cite this paper: Chin. J. Chem. 2021, 39, XXX—XXX. DOI: 10.1002/cjoc.202100XXX
Total Synthesis of Nucleoside Antibiotics Amicetin, Plicacetin,
and Cytosaminomycin A-D
Jiqiang Fu,a Peng Xu,*,a,b and Biao Yu*,a,b
a State Key Laboratory of Bioorganic and Natural Products Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of
Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China.
b School of Chemistry and Materials Science, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, 1 Sub-lane
Xiangshan, Hangzhou 310024, China.
Keywords
Total Synthesis |Glycosylation | Nucleoside Antibiotics | Amicetin | Cytosaminomycin
Main observation and conclusion
Amicetin and congeners constitute a small family of complex pyrimidine nucleosides, which exhibit strong antibiotic activities against
Gram-positive bacteria and notably against strains of Mycobacterium tuberculosis. Herein, we report the chemical synthesis of a series
of the disaccharide congeners of the amicetin family, including amicetin, plicacetin, and cytosaminomycin A-D. It is the first time for the
successful synthesis of amicetin, the prototypical member, and cytosaminomycins. The synthetic approach employs glycosyl N-phenyl-
trifluoroacetimidate and thioglycoside donors to construct the characteristic aminodeoxydisaccharides consisting of α-(1→4)-glycosidic
linkage, uses the gold(I)-catalyzed N-glycosylation to furnish the 2-deoxy-β-nucleosides, and finally exploits amidation and global depro-
tection to complete the syntheses. It is noteworthy that the 3-O-protecting group in the 2-deoxydisaccharide donors is found to be
crucial for a successful N-glycosylation to assemble the cytosaminomycin disaccharide nucleosides.
Comprehensive Graphic Content
-
α
O
(1)
-Glycosylation
Amidation
(3)
O
NR
N
HO
H
O
R
N
N
HO
H
HO
N
O
O
N
N
HO
O
O
HO
O
O
N
N
O
O
H2N
O
OH
S
A-D
HN
Cytosaminomycin
-
N
Amicetin
-Glycosylation
β
(2)
H
N
NH2
Plicacetin
*E-mail: byu@sioc.ac.cn; peterxu@sioc.ac.cn.
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2021
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CAS,
Shanghai,
&
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First author et al.
Report
this method, we also achieved total synthesis of the largest conge-
ner of the amicetin family, streptcytosine A, together with the
smaller fragments plicacetin (2) and cytosamine (3).[18] However,
the synthesis of amicetin was not successful due to failure in the
final amidation and deprotection. Herein, we report the first total
synthesis of amicetin (1), adopting modification of the previous syn-
thetic approach. In addition, cytosaminomycin A-D (3-6), which
bear olivose instead of amicetose in the disaccharide and a serious
acyl residues at cytimidine, are synthesized for the first time,
wherein the requisite N-glycosylation has been explored.
Background and Originality Content
Amicetin (1; Figure 1), a disaccharide pyrimidine nucleoside,
was originally isolated from Streptomyces vinaceusdrappus in early
1950s.[1,2] It has attracted great attention by its activities against
both Gram-negative and Gram-positive bacteria, as well as myco-
bacteria broth both in vitro and in vivo.[3,4] As a universal antibiotic,
amicetin exerts effects against microorganisms of different evolu-
tionary origins by functioning as a peptidyl transferase inhibitor to
block protein synthesis.[5] Thus far, over a dozen congeners of am-
icetin have been identified from natural sources, those include pli-
cacetin, bamicetin, streptcytosines, and cytosaminomycins.[6-12]
Many of these amicetin-type nucleosides also exhibit strong antibi-
otic activities against Gram-positive bacteria and most notably
against strains of Mycobacterium tuberculosis. In 2019, Ma et al.
disclosed that the natural acyl derivatives of cytosamine showed cy-
totoxicity against HCT-116 human colon cancer cell lines with IC50
values from 0.39 to 6.63 μM.[12] Recently, Looper et al. reported that
the amicetin-type aminohexopyranose nucleoside could be a trac-
table scaffold for the development of new anti-tubercular agents.[13]
They found that the cytimidine aglycone of amicetin and bacicetin
displayed no activity at 100 μM against Mtb H37Ra, indicating the
critical role of the disaccharide moiety for their antibiotic activities.
Results and Discussion
A linear approach was initially planned for the chemical synthe-
sis of the disaccharide pyrimidine nucleosides (Figure 2), so that en
route adjustment of the protecting groups and coupling sequence
would be flexible.[31] Additionally, this approach would ensure di-
vergent assembly of amicetin’s congeners and derivatives to facili-
tate the SAR studies. Thus, the introduction of acyl groups (R1) on
the poorly reactive NH2 of the cytosine nucleus (in A) could be
achieved by an effective microwave-assisted amidation.[32] The
gold(I)-catalyzed N-glycosylation (with disaccharide donor B) was
exploited to regioselectively install the cytosine nucleus.[33,34] The
construction of the α-linkage between an amosamine imidate do-
nor (C) and an amicetose/olivose acceptor (D) could be realized in
an ether solvent.[35]
NR1R2
O
HO
H
O
N
HO
H
N
N
N
HO
R
O
HO
O
O
O
N
N
N
N
O
HO
O
O
H2N
H
N
OH
=
NR1R2
1
):
Amicetin
(
S
=
A
3
R
Cytosaminomycin
(
):
O
O
O
O
N
HO
H
N
N
NH
NH2
=
1
2
OH
R2
O
:
A
NR R
R1
Streptcytosine
N
H
N
R2O
O
HO
=
=
O
O
B
C
D
4
R
R
O
O
Cytosaminomycin
Cytosaminomycin
(
):
N
N
N
N
R
R
O
Plicacetin
NR1R2 NH2
2
):
=
(
-
O
O
A
1
6
5
(
):
O
N
HO
O
O
nBu
O
NH2
N3
R2O
HO
O
O
=
6
R
R2O
N3
PMBO
Cytosaminomycin
O
(
):
N
N
O
O
+
HO
R
R3
O
O
LG
Cytosamine
R
O
OPMB
O
B
C
D
Figure 1 Structures of amicetin (1), streptcytosine A, plicacetin (2), cytosa-
mine, and cytosaminomycin A-D (3-6)
Figure 2 Retrosynthesis of amicetin (1) and congeners (2-6)
Structurally, the amicetin-type nucleosides are characterized
with a cytosine core that is attached to a 2,3,6-trideoxy-hexopyra-
nose (namely amicetose) or 2,6-dideoxy-hexopyranose (namely
olivose) via a β-N-glycosidic linkage (Figure 1). The cytosine base is
typically modified with different acyl groups; one of which is a p-
aminobenzoyl group that could be further amidated with L-Ala or
α-methyl-L-Ser. Another characteristic feature is the presence of an
α-(1→4)-glycosidic linkage between amosamine and am-
icetose/olivose. It is noteworthy that the biosynthetic pathway of
the amicetin-type nucleosides has recently been explored.[14,15]
Given the significant antibiotic activity and the unique struc-
tures, chemical synthesis of amicetin-type nucleosides is highly de-
sirable.[16-21] In 1972, Stevens et al. reported the total synthesis of
plicacetin, via O-glycosylation between an amosamine-type β-gly-
cosyl chloride donor and an amicetose nucleoside acceptor under
harsh conditions, resulting in only 38% yield of the desired α-linked
disaccharide.[16] Sugimura et al. accomplished the synthesis of cy-
tosamine and cytosaminomycin C, by coupling an amosamine-type
glycosyl fluoride donor with an amicetose/olivose nucleoside ac-
ceptor, affording disaccharide nucleoside in moderate yields
(60~70%) and stereoselectivity (α/β ≈ 5/1).[17,19,20] Our group has
devoted much effort on the N-glycosylation of nucleobases.[22-26] Es-
pecially, the gold(I)-catalyzed glycosylation protocol using glycosyl
ortho-alkynylbenzoates (Abz) as donors has been successfully ap-
plied to the synthesis of highly complex natural nucleoside antibi-
otics, including A201A, tunicamycins, and amipurimycin.[27-30] With
The synthesis of amicetin (1) commenced with the preparation
of carboxylic acid segments 9 and 10 (Scheme 1). The known acid
7[36] was amidated with methyl p-aminobenzoate in the presence of
HATU [O-(7-Azabenzotriazol-1-yl)-N,N,N',N'-Tetramethyluronium
Hexafluorophosphate] to provide amide 8. Hydrolysis and opening
of the oxazolidine ring under acidic conditions[36] followed by selec-
tive silylation of the primary hydroxyl group afforded acids 9 and 10
in moderate yields. Under the similar conditions for the previous
synthesis of plicacetin (2) and streptcytosine A,[18] the microwave-
assisted amidation between cytosamine and acid 9 or 10 in the
presence of HATU in pyridine at 80 oC failed to deliver the coupled
product D. We speculated that the unprotected amine in 9 and 10
had an adverse effect on the amidation reaction. Notwithstanding,
condensation of the fully protected carboxylic acid 8 and cytosa-
mine were also attempted under similar conditions, no desired ami-
dated products were obtained. We reasoned that the unprotected
amosamine moiety could exert a measure of influence on the ami-
dation reaction, furthermore the newly generated amido bond was
labile to the basic conditions, resulting in hydrolysis during the post-
processing manipulation.
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Chin. J. Chem. 2021, 39, XXX－XXX

Running title
Chin. J. Chem.
Scheme 1 Attempts toward the synthesis of amicetin
cosylation conditions between Abz-donor 16 and 15, the desired di-
saccharide 17 was obtained in a satisfactory yield and stereoselec-
tivity (70%, β/α = 5.6/1.0). Finally, reduction of the azide group in
17β, followed by reductive dimethylation of the nascent amine, and
subsequent cleavage of the PMB and Cbz groups (CF3CO2H;
H2/Pd(OH)2/C), furnished plicacetin (2) in 18% yield over 3 steps.
Due to the poor yield of the deprotection reactions at late stage,
our two synthetic routes to plicacetin are much the same from the
synthetic efficiency aspect.
O
O
Me
methyl p-aminobenzoate,
O
DMF, 80oC;
OH
OMe
O
HATU,DIPEA,
Me
N
N
tBu
Boc
O
H
79%
N
tBu
Boc
8
7
O
O
LiOH-H
THF, H
OH
2O,
2O,
1)
Me
50 o
HATU,
,
cytosamine
80 °C
C;
HCl
N
RO
pyridine,
80 °C;
H
2)
3)
(6 N),
or
NH2
:
=
TBS; 62%
=
TBDPS; 40%
TBSCl TBDPSCl,
9
R
:
imidazole,
DMF
10
R
Scheme 3 An alternative synthesis of plicacetin (2)
Me
H2N
O
H
OR
N
NHCbz
O
H
N
HO
CO2H
H
N
N
SOCl2, 30 °C;
BSTFA, CH3CN;
,
HO
O
O
N
N
O
CbzHN
16, PPh
3AuNTf2
HN
N
O
cytosine, pyridine
56%
D
BSTFA, CH CN, 5 MS
Å
3
14
15
O
O
=
70%,
5.6:
1.0
β/α
NHCbz
To solve this problem, we considered an alternative synthetic
pathway by coupling fully elaborated disaccharide 13 with acid 9
(Scheme 2). First, reduction of the azide group in intermediate 11[18]
under Staudinger conditions, followed by reductive dimethylation
with paraformaldehyde and NaBH3CN, led to disaccharide 12 in 70%
yield. Hydrolysis of the amido linkage under basic conditions fur-
nished PMB-protected cytosamine 13. With carboxylic acid 9 and
protected cytosamine 13 in hand, an optimal combination of acti-
vator, base, solvent and reaction temperature was screened care-
fully. Pleasingly, the desired amidation reaction successfully oc-
curred under microwave conditions (HATU, Hünig’s base,
PMe Et
NaBH CN, 59%;
3
,
3
O
N;
1)
2)
(CHO)n,
3
N3
PMBO
H
N
CF CO
50%;
2H,
3
PMBO
O
1 atm H 62%
,
3) Pd(OH)/C,
O
2
N
N
O
O
17
NH2
O
nBu
N3
O
H
N
HO
PMBO
N
PMBO
O
HO
O
O
O
O
N
N
O
O
O
16
Plicacetin
(2)
o
ClCH2CH2Cl, 70 C). Subsequently, desilylation with triethylamine
trihydrofluoride, followed by treatment with CF3CO2H, furnished
amicetin (1) in 27% yield over 3 steps. The poor yield of the last
three-step sequence was attributable to the following reasons: 1)
the amidation reaction was sluggish due to the inherently low reac-
tivity of the nucleoside NH2, and 2) the amido linkage was prone to
decompose during the deprotection reactions and the post-pro-
cessing manipulation.
One of the structural variables among amicetins and cytosa-
minomycins occurs at C-3’ of the pyranose, which could exist as the
deoxy or hydroxylated form, the latter sugar is known as olivose.
We speculated that the synthetic route toward amicetins could be
adopted to the preparation of cytosaminomycin A-D (3-6), employ-
ing an amosamine-type donor and an olivose acceptor (Scheme 4).
The 3-OH group in the known thioglycoside 18[37] was masked with
PMB ether, leading to the fully protected 2-deoxy-glucoside 19 in
89% yield. Cleavage of the 4,6-O-benzylidene acetal with TsOH·H2O
gave diol 20 (85%). The primary hydroxyl in 20 underwent selective
tosylation; and LiAlH4-mediated reduction furnished the 2,6-deoxy
olivose derivative 21 (29% for 2 steps, α/β = 3.3/1.0). Olivose ac-
ceptor 21α was coupled with amosanime-type imidate 22[18] under
optimal conditions (TBSOTf, 4Å MS, ether, -40 oC),[38] affording ex-
clusively α-disaccharide 23 in a moderate yield (47%). The moder-
ate yield of glycosylation was attributable to the high nucleophilicity
of the sulfur in 21, which is prone to undergo an intermolecular
aglycone transfer reaction.[39] As expected, hydrolysis of thioglyco-
side 23 in the presence of NBS (N-bromosuccinimide), followed by
esterification of the resulting hemiacetal with o-alkynylbenzoic acid
gave Abz-donor 24 in 65%. The gold(I)-catalyzed N-glycosylation of
disaccharide 24 with Cbz-protected cytosine 25 was then examined.
Disappointingly, the desired disaccharide E was not obtained under
a variety of conditions, resulting in hydrolysis of donor 24 and the
formation of a glycal-type by-product.[40] This failure was attributa-
ble to a mismatch of the poorly reactive NH acceptor in the cytosine
nucleus and the highly reactive PMB-protected disaccharide do-
nor.[41] It showed that the subtle structural variable at C-3’ of the
pyranose has a huge impact on the N-glycosylation.
Scheme 2 Synthesis of amicetin (1)
O
O
N
N3
PMBO
PMe3 NEt
,
THF, H2O;
,
3
NHCbz
NHCbz
PMBO
PMBO
PMBO
O
O
O
O
N
N
N
N
O)n, NaBH CN,
(CH2
3
O
O
12
11
MeOH, 70%
9
HATU, DIPEA,
,
CH2ClCH2Cl,
MW 70 °C, 30 min;
HF•NEt THF;
1)
O
N
NH2
PMBO
NaOH, MeOH, H2O
99%
,
2)
3)
3
PMBO
O
N
O
N
CF CO
CH Cl ; 27%
2 2
2H,
3
13
O
Me
H2N
O
H
OH
N
O
N
HO
H
N
HO
O
O
N
O
N
O
Amicetin
1
)
(
In our previous studies of the chemical synthesis of plicacetin
(2),[18] a gold(I)-catalyzed N-glycosylation led to the desired disac-
charide nucleoside in good yield and regioselectivity. However, ac-
ylation of cytosamine and iron-mediated nitro-reduction at a late
stage afforded plicacetin (2) in poor yield. Hence, we planned to
study an alternative route to the convergent synthesis of plicacetin
(2), by coupling disaccharide Abz-donor 16 with the PABA-modified
cytosine acceptor 15 (Scheme 3). Thus, Cbz-protected PABA 14 was
converted to acyl chloride, which was subjected to amidation with
cytosine to provide 15 in 56% yield. After briefly screening the gly-
Chin. J. Chem. 2021, 39, XXX－XXX
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First author et al.
Report
Scheme 4 Attempts toward the synthesis of disaccharide nucleoside E
Scheme 5 Synthesis of disaccharide nucleoside 34
O
O
Ph
O
Ph
O
O
2O,
1)
tBu
O
TBAF, AcOH;
NaOMe;
·H
TsOH
CH Cl /MeOH
PMBCl, NaH, DMF
89%
1)
2)
3)
STol
2
2
STol
;
PPh imidazole, NaHCO
,
3 3
I
PMBO
OAc
O
;
,
2
2) DTBS(OTf)2
HO
Si
O
AcO
O
85%
tBu
O
HO
AcO
Pd/C, 1 atm H , NaHCO
Ac
DMAP
2O,
2
3
3)
O
19
AcO
AcO
18
77%
3 steps
for
66% for 3 steps
OMP
22
4
MS,
, TBSOTf,
Å
28
OMP
OMP
HO
HO
PMBO
°
27
26
O
=
O
ether, -40
C
TsCl,
LiAlH THF, 60 o
HO
1)
2)
pyridine;
STol
STol
α
only
47%,
PMBO
21
O
,
4
C
N3
O
N3
PMBO
α
,
/
3.3: 1.0)
β
O
(29%,
N3
PMBO
20
STol
SEMO
DDQ;
1)
2)
SEMO
PMBO
O
O
AcO
29
PMBO
O
O
SEMCl, DIPEA,
TBAI, 80 o 81%
O
nBu
NIS, TBSOTf, 4
MS, CH2Cl2, -60
Å
C
N3
PMBO
PMBO
AcO
°
C;
OMP
O
N3
PMBO
NBS, acetone,
α
1)
=
11: 1
OMP
O
91%,
/
β
°
,
CH Cl -20 C;
2 2
31
O
O
H
-
30
2O,
O
O
PMBO
PMBO
O
O
o
n-
acid,
nBu
2)
butylethynylbenzoic
EDCI, DMAP; 65%
PMBO
N3
24
CAN;
-
1)
2)
SEMO
STol
25
,
PPh AuNTf
,
2
23
3
o
n-
acid,
SEMO
butylethynylbenzoic
O
O
O
BSTFA,
MS, CH CN
3
5Å
77%
EDCI, DMAP;
NHCbz
AcO
=
69%
1:1.2
,
β/α
O
32
HN
O
N
NPh
CF3
O
N3
25
PPh AuNTf
,
,
2
NHCbz
O
3
PMBO
N3
PMBO
O
PMBO
BSTFA,
MS, CH CN
3
O
N
5Å
O
×
N
OPMB
22
PMBO
PMe NEt 50 °C
;
,
3
,
′
1)
3
O
O
N
3
N3
SEMO
NaBH CN,
O
2) (CH2O)n,
AcOH;
3
NH2
NHCbz
SEMO
E
SEMO
O
SEMO
O
O
O
N
N
N
N
NaOH
63%
(aq.);
3)
HO
AcO
O
O
33
Since high reactive donors are prone to proceed side reactions,
we decided to adjust the protection pattern by introducing an elec-
tron-withdrawing acyl group onto the donor (Scheme 5). Com-
pound 28 was prepared in a straightforward manner from p-meth-
oxyphenyl (MP) 3,4,6-tri-O-acetyl-2-deoxy-α-D-glucopyranoside
26.[42] After removal of the acetyl groups, the 4,6-hydroxyl groups
were selectively protected as di-tert-butylsilanediyl acetal, and the
free 3-OH was masked with acetyl group, leading to the fully pro-
tected monosaccharide 27 in 66% yield over 3 steps from 26. The
4,6-O-di-tert-butylsilanediyl acetal was cleaved with TBAF (tetrabu-
tylammonium fluoride) and acetic acid to give the corresponding
4,6-diol. The resultant primary 6-OH was regioselectively iodinated
and then immediately reduced over Pd/C in the presence of Na-
HCO3 to afford the olivose acceptor 28 in 77% overall yield. Olivose
acceptor 28 was subjected to glycosylation with thioglycoside do-
nor 29[18] (NIS, TBSOTf, 4Å MS, CH2Cl2, -60 oC), affording disaccha-
ride 30 in an excellent yield and stereoselectivity (91%, α/β = 11/1).
It is noteworthy that replacing of the thioglycoside acceptor 21 with
MP-glycoside acceptor 28 avoided completely the aforementioned
intermolecular aglycone transfer side-reaction. Because the PMB
ether was found to be vulnerable during deprotection of the MP
group, it was replaced with SEM [2-(Trimethylsilyl)ethoxymethyl]
ether. Thus, disaccharide 30 was smoothly converted to 31 via oxi-
dative removal of PMB ethers with DDQ and Williamson etherifica-
tion with SEMCl. Selective cleavage of the anomeric MP group with
CAN in a mixed solvent of acetonitrile and phosphate buffer (pH 7),
followed by esterification with o-alkynylbenzoic acid provided Abz-
donor 32 in 77% over 2 steps. The coupling of 32 with 25 under sim-
ilar conditions as for the previous glycosylation with Abz-donor 24
afforded the desired disaccharide in 69% yield with a β/α ratio of
1.0/1.2; the anomers could be separated by silica gel plate chroma-
tography. In comparison to the previous β-selective N-glycosylation
in the amicetin synthesis, the present N-glycosylation was no longer
stereoselective due to the presence of the 3-O-acetyl group in the
disaccharide donor.[43-45] Reduction of the azide group in 33β under
Staudinger conditions, followed by reductive dimethylation and hy-
drolysis furnished SEM-protected disaccharide 34 in good yield (63%
for 3 steps).
34
Starting from the advanced intermediate 34, cytosaminomycin
A-D (3-6) were synthesized conveniently in two steps (Scheme 6).
Thus, disaccharide nucleoside 34 was subjected to coupling with
the requisite carboxylic acids or acyl chlorides (35-38) under esteri-
fication conditions and subsequent removal of the SEM group un-
der acidic conditions to furnish cytosaminomycin A-D (3-6) in 25-77%
yield. It was noted that the isolated yield of cytosaminomycin B (4)
was only 25%, mainly because intermediate 34 could not be fully
consumed in the amidation process, and the poor solubility of the
PABA-modified nucleosides brought loss of product in the subse-
quent purification process. The NMR spectra and specific rotation
of the synthetic amicetin (1), plicacetin (2) and cytosaminomycin A-
D (3-6) were in good accordance with those reported for the natural
products.[10,15,21]
Scheme 6 Synthesis of cytosaminomycin A-D (3-6)
or
35 36
or
or
37 38
chloride
(
O
acid
esterification;
acyl
1)
2)
(
)
),
H
N
HO
N
R
HO
CF CO
CH Cl
2H,
O
3
2
2
O
34
N
N
HO
77%
3
,
25%
4
,
6
for
for
O
5
56% for 64% for
,
S
=
=
A
3
4
R
R
Cytosaminomycin
Cytosaminomycin
(
):
O
O
O
S
OH
Cl
Cl
H
N
O
B
35
36
37
(
):
H
O
O
N
=
=
C
D
5
R
R
Cytosaminomycin
Cytosaminomycin
(
):
OH
38
O
O
6
):
(
Conclusions
We have developed a general approach to the chemical synthe-
sis of amicetin-type nucleoside antibiotics, and the synthesis of am-
icetin (1) and cytosaminomycin A-D (3-6) are realized for the first
time. The synthetic approach employs an α-selective O-glycosyla-
tion to construct the disaccharide moiety, a gold(I)-catalyzed N-gly-
cosylation to install the β-nucleosides, and a late-stage amidation
to complete the modular syntheses. Notwithstanding, the gold(I)-
catalyzed N-glycosylation towards cytosaminomycins, requiring an
electron-withdrawing acyl protecting group in the donor and lead-
ing to loss of regioselectivity, remains to be improved. In addition,
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Running title
Chin. J. Chem.
for the synthesis of other amicetin members and derivatives, the
effectiveness of the amidation reaction is yet to be explored. The
accessibility of amicetin-like nucleosides would enable us to eluci-
date the precise structure-activity relationships and to facilitate fur-
ther development of this new type of antimicrobial agents.
Serrano, C. M.; Reddy, H. R. K.; Eiler, D.; Koch, M.; Tresco, B. I. C.; Bar-
rows, L. R.; VanderLinden, R. T.; Testa, C. A.; Sebahar, P. R.; Looper, R.
E., Unifying the aminohexopyranose- and peptidyl-nucleoside antibi-
otics: Implications for antibiotic design. Angew. Chem. Int. Ed. 2020,
59, 11330-11333.
Zhang, G.; Zhang, H.; Li, S.; Xiao, J.; Zhang, G.; Zhu, Y.; Niu, S.; Ju, J.;
Zhang, C., Characterization of the amicetin biosynthesis gene cluster
from Streptomyces vinaceusdrappus NRRL 2363 implicates two alter-
native strategies for amide bond formation. Appl. Environ. Microbiol.
2012, 78, 2393-2401.
Chen, R.; Zhang, H.; Zhang, G.; Li, S.; Zhang, G.; Zhu, Y.; Liu, J.; Zhang,
C., Characterizing amosamine biosynthesis in amicetin reveals AmiG as
a reversible retaining glycosyltransferase. J. Am. Chem. Soc. 2013, 135,
12152-12155.
Stevens, C. L.; Němec, J.; Ransford, G. H., Total synthesis of the amino
sugar nucleoside antibiotic, plicacetin. J. Am. Chem. Soc. 1972, 94,
3280-3281.
Sugimura, H.; Watanabe, K.-i., Formal synthesis of cytosamine—a
component of nucleoside antibiotics, the amicetin family. Synth. Com-
mun. 2001, 31, 2313-2321.
Fu, J.; Laval, S.; Yu, B., Total synthesis of nucleoside antibiotics plica-
cetin and streptcytosine A. J. Org. Chem. 2018, 83, 7076-7084.
Sugimura, H., Synthetic study of cytosaminomycins using the intramo-
lecular glycosylation as a key step. Nucleic Acids Res. Suppl. 2003, 21-
22.
Sugimura, H.; Watanabe, R., Total synthesis of cytosaminomycin C.
Chem. Lett. 2008, 37, 1038-1039.
Haskell, T. H., Amicetin, Bamicetin and Plicacetin. Chemical Studies. J.
Am. Chem. Soc. 1958, 80, 747-751.
Experimental
Experimental procedures are available in Supporting Infor-
mation.
Supporting Information
The supporting information for this article is available on the
WWW under https://doi.org/10.1002/cjoc.2021xxxxx.
Acknowledgement
Financial support from the National Natural Science Foundation
of China (21861162011, 22031011, & 21621002), National Key Re-
search & Development Program of China (2018YFA0507602), Key
Research Program of Frontier Sciences of CAS (ZDBS-LY-SLH030),
Strategic Priority Research Program of CAS (XDB20020000), and
Youth Innovation Promotion Association of CAS (2020258) are
acknowledged.
Liao, J.; Sun, J.; Yu, B., Effective synthesis of nucleosides with glycosyl
trifluoroacetimidates as donors. Tetrahedron Lett. 2008, 49, 5036-
5038.
Liao, J.; Sun, J.; Yu, B., An improved procedure for nucleoside synthesis
using glycosyl trifluoroacetimidates as donors. Carbohydr. Res. 2009,
344, 1034-1038.
Zhang, Q.; Sun, J.; Zhu, Y.; Zhang, F.; Yu, B., An efficient approach to
the synthesis of nucleosides: gold(I)-catalyzed N-glycosylation of py-
rimidines and purines with glycosyl ortho-alkynyl benzoates. Angew.
Chem. Int. Ed. 2011, 50, 4933-4936.
Yang, F.; Zhu, Y.; Yu, B., A dramatic concentration effect on the stere-
oselectivity of N-glycosylation for the synthesis of 2'-deoxy-β-ribonu-
cleosides. Chem. Commun. 2012, 48, 7097-7099.
Hu, Z.; Tang, Y.; Yu, B., Glycosylation with 3,5-dimethyl-4-(2'-phe-
nylethynylphenyl)phenyl (EPP) glycosides via a dearomative activation
mechanism. J. Am. Chem. Soc. 2019, 141, 4806-4810.
Nie, S.; Li, W.; Yu, B., Total synthesis of nucleoside antibiotic A201A. J.
Am. Chem. Soc. 2014, 136, 4157-4160.
Li, J.; Yu, B., A modular approach to the total synthesis of tunicamycins.
Angew. Chem. Int. Ed. 2015, 54, 6618-6621.
Wang, S.; Sun, J.; Zhang, Q.; Cao, X.; Zhao, Y.; Tang, G.; Yu, B., Amipu-
rimycin: Total synthesis of the proposed structures and diastereoiso-
mers. Angew. Chem. Int. Ed. 2018, 57, 2884-2888.
Wang, S.; Zhang, Q.; Zhao, Y.; Sun, J.; Kang, W.; Wang, F.; Pan, H.; Tang,
G.; Yu, B., The Miharamycins and Amipurimycin: their structural revi-
sion and the total synthesis of the latter. Angew. Chem. Int. Ed. 2019,
58, 10558-10562.
Yu, B.; Sun, J.; Yang, X., Assembly of naturally occurring glycosides,
evolved tactics, and glycosylation methods. Acc. Chem. Res. 2012, 45,
1227-1236.
Valeur, E.; Bradley, M., Amide bond formation: beyond the myth of
coupling reagents. Chem. Soc. Rev. 2009, 38, 606-631.
Yu, B., Gold(I)-Catalyzed glycosylation with glycosyl o-alkynylbenzo-
ates as donors. Acc. Chem. Res. 2018, 51, 507-516.
Li, W.; Yu, B., Gold-catalyzed glycosylation in the synthesis of complex
carbohydrate-containing natural products. Chem. Soc. Rev. 2018, 47,
7954-7984.
References
Flynn, E. H.; Hinman, J. W.; Caron, E. L.; Woolf, D. O., The chemistry of
amicetin, a new antibiotic. J. Am. Chem. Soc. 1953, 75, 5867-5871.
Stevens, C. L.; Nagarajan, K.; Haskell, T. H., The structure of amicetin.
J. Org. Chem. 1962, 27, 2991-3005.
DeBoer, C.; Caron, E. L.; Hinman, J. W., Amicetin, a new streptomyces
antibiotic. J. Am. Chem. Soc. 1953, 75, 499-500.
Hinman, J. W.; Caron, E. L.; DeBoer, C., The isolation and purification
of amicetin. J. Am. Chem. Soc. 1953, 75, 5864-5866.
Leviev, I. G.; Rodriguez-Fonseca, C.; Phan, H.; Garrett, R. A.; Heilek, G.;
Noller, H. F.; Mankin, A. S., A conserved secondary structural motif in
23S rRNA defines the site of interaction of amicetin, a universal inhib-
itor of peptide bond formation. The EMBO Journal 1994, 13, 1682-
1686.
Haskell, T. H.; Ryder, A.; Frohardt, R. P.; Fusari, S. A.; Jakubowski, Z. L.;
Bartz, Q. R., The isolation and characterization of three crystalline an-
tibiotics from Streptomyces plicatus. J. Am. Chem. Soc. 1958, 80, 743-
747.
Konishi, M.; Naruishi, M.; Tsuno, T.; Tsukiura, H.; Kawaguchi, H., Ox-
amicetin, a new antibiotic of bacterial origin. II. Structure of oxam-
icetin. J. Antibiot. (Tokyo) 1973, 26, 757-764.
Evans, J. R.; Weare, G., Norplicacetin, a new antibiotic from Strepto-
myces plicatus. J. Antibiot. (Tokyo) 1977, 30, 604-606.
Miyadoh, S.; Amano, S.; Shomura, T., Strain SF2457, a new producer of
amicetin group antibiotic. Actinomycetologica 1990, 4, 85-88.
Haneda, K.; Shinose, M.; Seino, A.; Tabata, N.; Tomoda, H.; Iwai, Y.;
Omura, S., Cytosaminomycins, new anticoccidial agents produced by
Streptomyces sp. KO-8119. I. Taxonomy, production, isolation and
physico-chemical and biological properties. J. Antibiot. (Tokyo) 1994,
47, 774-781.
Bu, Y. Y.; Yamazaki, H.; Ukai, K.; Namikoshi, M., Anti-mycobacterial nu-
cleoside antibiotics from
TPU1236A. Mar. Drugs 2014, 12, 6102-6112.
Xu, C. D.; Zhang, H. J.; Ma, Z. J., Pyrimidine nucleosides from Strepto-
myces sp. SSA28. J. Nat. Prod. 2019, 82, 2509-2516.
a marine-derived Streptomyces sp.
Chin. J. Chem. 2021, 39, XXX－XXX
© 2021 SIOC, CAS, Shanghai, & WILEY-VCH GmbH
www.cjc.wiley-vch.de

First author et al.
Report
Satoh, H.; Hansen, H. S.; Manabe, S.; van Gunsteren, W. F.; Hünen-
Paul, S.; Jayaraman, N., Synthesis of aryl-2-deoxy-D-lyxo/arabino-hex-
opyranosides from 2-deoxy-1-thioglycosides. Carbohydr. Res. 2007,
342, 1305-1314.
Crich, D.; Hu, T.; Cai, F., Does neighboring group participation by non-
vicinal esters play a role in glycosylation reactions? Effective probes for
the detection of bridging intermediates. J. Org. Chem. 2008, 73, 8942-
8953.
Baek, J. Y.; Lee, B.-Y.; Jo, M. G.; Kim, K. S., β-Directing effect of electron-
withdrawing groups at O-3, O-4, and O-6 positions and α-directing ef-
fect by remote participation of 3-O-acyl and 6-O-acetyl groups of do-
nors in mannopyranosylations. J. Am. Chem. Soc. 2009, 131, 17705-
17713.
berger, P. H., Theoretical investigation of solvent effects on glycosyla-
tion reactions: stereoselectivity controlled by preferential confor-
mations of the intermediate oxacarbenium-counterion complex. J.
Chem. Theory Comput. 2010, 6, 1783-1797.
Serrano, C. M.; Looper, R. E., Synthesis of cytimidine through a one-
pot copper-mediated amidation cascade. Org. Lett. 2011, 13, 5000-
5003.
Chen, J.-H.; Ruei, J.-H.; Mong, K.-K. T., Iterative α-glycosylation strat-
egy for 2-deoxy- and 2,6-dideoxysugars: Application to the one-pot
synthesis of deoxysugar-containing oligosaccharides. Eur. J. Org. Chem.
2014, 1827-1831.
Yu, B.; Tao, H., Glycosyl trifluoroacetimidates. Part 1: Preparation and
application as new glycosyl donors. Tetrahedron Lett. 2001, 42, 2405-
2407.
Yu, H.; Yu, B.; Wu, X.; Hui, Y.; Han, X., Synthesis of a group of diosgenyl
saponins with a combined use of glycosyl trichloroacetimidate and thi-
oglycoside donors. J. Chem. Soc., Perkin Tran. 1 2000, 1445–1453.
Christensen, H. M.; Oscarson, S.; Jensen, H. H., Common side reactions
of the glycosyl donor in chemical glycosylation. Carbohydr. Res. 2015,
408, 51-95.
Spijker, N. M.; van Boeckel, C. A. A., Double stereodifferentiation in
carbohydrate coupling reactions: The mismatched interaction of do-
nor and acceptor as an unprecedented factor governing the α/β ratio
of glycoside formation. Angew. Chem. Int. Ed. 1991, 30, 180-183.
Xu, K.; Man, Q.; Zhang, Y.; Guo, J.; Liu, Y.; Fu, Z.; Zhu, Y.; Li, Y.; Zheng,
M.; Ding, N., Investigation of the remote acyl group participation in
glycosylation from conformational perspectives by using trichloroace-
timidate as the acetyl surrogate. Org. Chem. Front. 2020, 7, 1606-1615.
(The following will be filled in by the editorial staff)
Manuscript received: XXXX, 2021
Manuscript revised: XXXX, 2021
Manuscript accepted: XXXX, 2021
Accepted manuscript online: XXXX, 2021
Version of record online: XXXX, 2021
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Running title
Chin. J. Chem.
Entry for the Table of Contents
Total Synthesis of Nucleoside Antibiotics Amicetin, Plicacetin, and Cytosaminomycin A-D
Jiqiang Fu, Peng Xu,* and Biao Yu*
Chin. J. Chem. 2021, 39, XXX—XXX. DOI: 10.1002/cjoc.202100XXX
H2N
O
Amicetin
Cytosaminomycins
H
OH
N
O
N
HO
O
H
H
N
HO
N
R
O
N
HO
HO
O
O
O
O
N
N
O
N
N
HO
O
O
α
-Selective N
-Selective O
Amidation of
poorly
NH
nucleophilic
β
-glycosylation
-glycosylation
2
Amicetin and congeners constitute a small family of complex pyrimidine nucleosides, which exhibit strong antibiotic activities. Herein, we report the
first chemical synthesis of a series of the disaccharide congeners of the amicetin family, including amicetin and cytosaminomycin A-D.
Chin. J. Chem. 2021, 39, XXX－XXX
© 2021 SIOC, CAS, Shanghai, & WILEY-VCH GmbH
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