Synthesis of seven-membered iminosugars fused thiazolidin-4-one and benzthiazinan-4-one and their HIV-RT inhibitory activity

Article abstract of DOI:10.1016/j.carres.2016.02.011

Novel seven-membered iminosugars fused thiazolidin-4-one and benzthiazinan-4-one were conveniently synthesized by the tandem Staudinger/aza-Wittig/cyclization reaction under microwave radiation. Benzoyl group (Bz) migrations were found in the synthesis of

Full text of DOI:10.1016/j.carres.2016.02.011

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Contents lists available at ScienceDirect
Carbohydrate Research
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Synthesis of seven-membered iminosugars fused thiazolidin-4-one
and benzthiazinan-4-one and their HIV-RT inhibitory activity
Yuheng Hou a, Shunkai Xing a, Jie Shao a, Zhuqing Yin a, Le Hao a, Tianyu Yang a,
Hongzhi Zhang a, Mo Zhu a, Hua Chen a,b,*, Xiaoliu Li a,b,
*
a Key Laboratory of Chemical Biology of Hebei Province, College of Chemistry and Environmental Science, Hebei University, Baoding 071002, China
b National Research Center for Carbohydrate Synthesis, Jiangxi Normal University, Nanchang 330022, China
A R T I C L E
I N F O
A B S T R A C T
Article history:
Novel seven-membered iminosugars fused thiazolidin-4-one and benzthiazinan-4-one were conve-
niently synthesized by the tandem Staudinger/aza-Wittig/cyclization reaction under microwave radiation.
Benzoyl group (Bz) migrations were found in the synthesis of 8c and 9b using D-galactoside or D-mannoside
as starting materials, respectively, which was suggested by HMBC and X-ray. The new bi/tricyclic iminosugars
3~4(a–d) and 5(b–d) were examined for their HIV reverse transcriptase (RT) inhibitory activities. The
result showed that all compounds except 5b could effectively inhibit RT activity. Among them, com-
pounds 3c and 4c were the best ones with the IC50 values of RT inhibitory activities of 2.11 μM and 2.73 μM,
respectively. Structure–activity relationship analysis suggested that the phenyl group in the tricyclic
azasugars was beneficial for their anti-HIV RT activity.
Received 4 December 2015
Received in revised form 23 February 2016
Accepted 27 February 2016
Available online
Keywords:
Seven-membered iminosugar
Thiazolidin-4-one
Benzthiazinan-4-one
Staudinger/aza-Wittig
Anti-HIV RT activity
© 2016 Elsevier Ltd. All rights reserved.
1. Introduction
HIV-RT inspired us to explore its innovative analogs to develop novel
iminosugar-based drugs with higher activity.
Iminosugars or azasugars, which exhibit effective inhibition
against carbohydrate-processing enzymes, have attracted great in-
terest for their potential clinical applications as anti-HIV, anti-
diabetic, and anti-cancer agents and immunomodulators in past
decades.1–4 The bicyclic azasugars, including the naturally occur-
ring compounds (A–D)5–8 and the synthetic ones (E–F)9–17 (Fig. 1),
have also been paid much attention due to their increased possi-
bility leading to the discovery of new bioactive therapeutic agents.
To date, a large number of bicyclic azasugars bearing six-membered
nitrogen heterocycle have been synthesized and evaluated.18–20 Much
less efforts have been put into higher ring size analogs.21,22 Addi-
tionally, the tricyclic azasugars were so far scarcely reported for their
synthesis and biological activity study.
Recently, by using microwave-assisted one-pot Staudinger/aza-
Wittig/condensation reaction, we have conveniently synthesized a
series of novel bi/tricyclic azasugars fused thiazolidin-4-one and
thiazinan-4-one (1 and 2, Fig. 1).23–26 The biological evaluation in-
dicated that these bi/tricyclic azasugars (1 and 2) exhibited strong
HIV reverse transcriptase (HIV-RT) inhibitory activities but poor in-
hibitory against glycosidases.23,25 The promising activity against
Polyhydroxyazepanes, having the more flexibility and higher
water solubility compared with five- or six-membered rings, are po-
tentially useful as drug candidates or structural motifs.27 As a
continuation of our researches, herein, we would like to report the
synthesis of the novel bi/tricyclic seven-membered azasugars fused
thiazolidin-4-one and thiazinan-4-one (3–5, Fig. 2). Such newly syn-
thetic azasugars were evaluated for their HIV-RT inhibitory activity
in order to further investigate the structure–activity relationship
(SAR).
2. Results and discussion
2.1. Synthesis of the bi/tricyclic seven-membered azasugars fused
thiazolidin-4-one and thiazinan-4-one (3–5)
The requisite azidosugars 6a–c (Table 1) were prepared from
D-glucose, D-galactose, D-mannose according to the literatures.28,29
The key reaction for the synthesis of the bi/tricyclic azasugars fused
thiazolidin-4-one and benzthiazinan-4-one (7–9) was the
microwave-assisted one-pot Staudinger/aza-Wittig/cyclization re-
action using 6a–c as the starting materials (Scheme 1). Following
the reported procedures,23,24 the microwave-assisted reactions af-
forded mainly two diastereoisomers of the bi/tricyclic seven-
membered azasugars in low yields with low stereoselectivity except
the case of entry 5. In entry 5, the reaction of 6c with mercapto-
acetic acid stereospecifically afforded single diastereoisomer 9b and
*
Corresponding authors. Key Laboratory of Chemical Biology of Hebei Province,
College of Chemistry and Environmental Science, Hebei University, Baoding 071002,
China. Tel.: 0086 312 5971116; fax: 0086 312 5971116.
E-mail addresses: hua-todd@163.com (H. Chen), lixl@hbu.cn (X. Li).
http://dx.doi.org/10.1016/j.carres.2016.02.011
0008-6215/© 2016 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Yuheng Hou, et al., Synthesis of seven-membered iminosugars fused thiazolidin-4-one and benzthiazinan-4-one and their HIV-RT inhibitory activ-
ity, Carbohydrate Research (2016), doi: 10.1016/j.carres.2016.02.011

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Y. Hou et al./Carbohydrate Research ■■ (2016) ■■–■■
excessive consumption of imine maybe caused the low yields of the
HO
HO
HO
HO
O
HO
HO
OH
reactions. After workup and purification by silica gel column
chromatography, each pair of the diastereoisomeric products 7–9
was obtained, respectively.
H
N
H
N
N
N
H
OH
HO
HO
CH2COOH
O
N
OH
HO
N
HO
H
NHAc
OH
It should be noted that Bz migrations were observed in the prod-
ucts in entries 4 and 5. The position of the naked hydroxyl group
was determined by the analysis of the HMBC spectra of the prod-
ucts (see supporting information). Taken the 9b as example (Fig. 3),
the C and H signals of 6, 7, 8, 9, and 9a were assigned by the key JC–H
couplings between C-3/9a-H(δH 5.11 ppm), C-9a(δC 62.8 ppm)/2-H,
5-H, 8-H(δH 6.28 ppm) and 9-H(δH 5.70 ppm), C-9(δC 76.3 ppm)/2-H,
9a-H and 7-H(δH 6.05 ppm), C-8(δC 67.8 ppm)/6-H(δH 4.58 ppm),
C-7(δC 72.4 ppm)/9-H, and the absent correlations between
C-9/6-H; C-6(δC 67.7 ppm)/9-H in the HMBC spectrum, then the un-
protected hydroxyl group at C-6 was deduced from the cross peaks
of the C — O on Bz and 7-H, 8-H, and 9-H. Using the same protocol,
compounds 7a, 7c, 8a, 8b, 9b-1, 2, 3, and 9c were checked for their
positions of the unprotected hydroxyl groups by HMBC.
Deprotection in NaOMe solution at room temperature, the cor-
responding bi/tricyclic azasugars fused thiazolidin-4-one 3~4(a–
b) and 5b, and benzthiazinan-4-one 3~5(c–d) were obtained in good
yields. The structures of all the newly synthesized bi-/tricyclic
iminosugars were determined by their 1H, 13C NMR, and HRMS (ESI)
spectra. Both analytical and spectral data of compounds are in agree-
ment with the proposed structures. The typical coupling constants
of 9a-H and 9-H (Table 2) indicated that compounds 3a, 3c, 4a, 4c,
5b, and 5d with big J9,9a values should have trans-relationship
between 9a-H and 9-H, while their corresponding diastereomers
A castanospermine
B swainsonine
C kifunensine
D nagstatin
HO
O
S
HO
HO
H
O
HO
HO
N
H
HO
N
HO
X
N
R
O
Z
N
N
S
HO
HO
HO
HO
Y
HO
OH
H
HO
2a
2b
HO
H
1a R=H2
1b R=O
F (Z=O, S, NR)
E (X=Y=N, CH)
H
Fig. 1. The structures of some bi/tricyclic azasugars.
its benzoyl group (Bz) migrated analogs 9b-1, 9b-2, and 9b-3, pos-
sibly due to the synergistic hindrance effects of the cis neighboring
Bz groups at 8, 9 positions, which made a dominant exo-attack of
the sulfur atom to the intermediate imine (I) (Scheme 2). However,
the reactions of 6c with 2-mercaptobenzoic acid (Entry 6) af-
forded two diastereoisomers 9c and 9d with equal amount. The
hypothesized formation mechanism of the 4-benzthiazinanone-
azasugar hybrids 9c and 9d was shown in Scheme 2. It was likely
that the phenyl group could stabilize the delocalized anionic charge
in the intermediate (II) by conjugated effect, which made the ra-
cemization at C-9a. The byproduct that was generated by
intramolecular nucleophilic addition from the corresponding
intermediate imine was obtained in entry 2 (Scheme 3).30 The
O
O
O
S
O
S
S
O
S
S
S
O
R
N
R
N
N
N
R
R
N
R
N
R
OH
OH
OH
OH
OH
OH
OH
OH
OH
OH
HO
HO
H
O
OH
HO
H
O
H
O
HO
OH
OH
OH
H
O
OH
H
O
3a: R=
3b: R=
3c: R =
3d: R=
;
H
;
H
4a: R = H;
4b: R= H;
4c: R=
4d: R=
;
H
;
H
5c: R= H;
5d: R= H;
H;
H;
5b: R=
;
H
Fig. 2. The synthetic bi/tricyclic seven-membered azasugars fused thiazolidin-4-one and thiazinan-4-one.
Table 1
The synthesis of the bi-/tricyclic azasugars 7~8(a–d) and 9(b–d) by the microwave-assisted one-pot tandem Staudinger/aza-Wittig/cyclization reactions
Azido sugars
Mercaptan acids
Entry
DCC (equiv.)
Products
Total yields (%)a
Ratio of 9aS:9aRb
9aS
9aR
c
6a
SHCH2COOH
1
2
–
7a
7c
7b
7d
55.5
20.5
1.8:1
2.0:1
1.2d
COOH
SH
6b
6c
SHCH2COOH
3
4
1.2
1.2
8a
8c
8b
8d
18.4
13.7
1.2:1
1.2:1
COOH
SH
SHCH2COOH
5
6
1.2
1.2
N. D.e
9b, 9b-1
9b-2, 9b-3
9d
38f
20
0:1
9c
1:1.1
COOH
SH
a
Isolated yield.
b
Determined by 1H NMR.
c
6a (or 6b, 6c) and Ph3P were firstly stirred in 3 mL dry toluene for 10 min at M. W. 80 °C, then mercaptan acid was added for another 15 min stirring at M. W. 80 °C. The
ratio of reactants: 6a (1 mmol) : Ph3P : mercaptan acid = 1 : 1.5 : 2, and the reaction was performed in 10 mL sealed tube.
d
DCC (1.2 equiv.) was added accompanied with mercaptan acid, then the mixture was stirred for another 20 min at M. W. 100 °C.
Not detected.
The total yields of 9b, 9b-1, 9b-2, and 9b-3.
e
f
Please cite this article in press as: Yuheng Hou, et al., Synthesis of seven-membered iminosugars fused thiazolidin-4-one and benzthiazinan-4-one and their HIV-RT inhibitory activ-
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3
2
O
O
S
1
S
3
N3
4
H
N
N
H
a
9
PPh3 toluene
)
)
i
+
PPh3 toluene
i)
)
O
O
S
O
H
S
OBz
OBz
5
9
+
BzO
BzO
O
H
N
N
H
H
6
8
H
H
H
ii
SC 2COO
7
SH
ii
OBz
OBz
OBz
H
O
H
O
OBz
MW
OBz
COOH
MW
OBz
OBz
HO
OBz
O
OBz
D
6a: -Glucoside
a
7
OBz
7c
OBz
7
b
d
7
O
O
S
S
N3
BzO
BzO
N
N
H
H
OBz
)
PPh3 toluene
i
+
PPh3 toluene
O
)
i
S
O
S
O
OBz
+
H
O
N
H
N
H
OBz
)
ii
H
H
H
SC 2COO
H
S
)
ii
OBz
OBz
OBz
HO
O
HO
MW
OBz
H
COO
MW
OBz
8a
OBz
8b
BzO
OBz
OBz
BzO
6b: -Galactoside
D
OH
8d
OH
8c
Bz migration
O
S
S
H
OBz
N
N
H
+
OB z
OBz
BzO
OBz
HO
OH
OBz
9b
N3
9b-1
O
PPh3 toluene
i)
PPh3 toluene
i)
S
S
O
O
+
BzO
N
H
H
OBz
OH
OBz
N
H
S
HSCH2COOH
MW
ii)
ii)
OBz
O
O
BzO
S
S
COOH
MW
OBz
HO
OBz
H
OBz
H
H
O
N
N
6c: D-Mannoside
H
O
+
OBz
9d
OBz
9c
BzO
OBz
OH
BzO
OBz
OBz
9b-2
9b-3
Bz migration
Scheme 1. The synthesis of the bi-/tricyclic azasugars 7~8(a–d) and 9(b–d) by the microwave-assisted reaction using 6a–c.
are of cis forms. Thus, the absolute configuration of compounds 3a,
3c, 4a, 4c, and 5c could be determined to be of (9aS), the others
were of (9aR). The absolute configuration of compound 4a was de-
termined to be of (9aS) by its X-ray crystallographic data (Fig. 4),31
being consistent with the above NMR result. The X-ray crystallo-
graphic structure of the Bz protected compound 8d further supported
its absolute configurations of (9aR) and Bz migration from hy-
droxyl group on C-7 to C-6(Fig. 4).
O
exo
O
N
S
attack
HO
N3
H
N
S
N
PPh3
O
z
B
O
Cyclization
H
H
H
SC 2COO
OBz
OBz
H
O
Staudinger
BzO
OH
OBz
OBz
OBz
H
O
z
aza-Wittig
z
B
O
B
O
H
O
BzO
I
OBz
9b
BzO
6c
exo
attack
H
S
H
COO
O
O
O
Cyclization
DCC
racemization
S
S
H
O
S
S
H
O
H
O
H
O
N
*
N
N
N
*
*
OBz
OBz
OBz
OBz
OBz
OBz
OBz
OBz
HO
HO
HO
HO
BzO
BzO
BzO
II
BzO
9c and 9d
Scheme 2. Hypothesized formation mechanism of the 4-benzthiazinanone-azasugar hybrids 9b–9d.
Please cite this article in press as: Yuheng Hou, et al., Synthesis of seven-membered iminosugars fused thiazolidin-4-one and benzthiazinan-4-one and their HIV-RT inhibitory activ-
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NH
N3
N
O
PPh3
Staudinger
aza-Wittig
O
OBz
H
O
BzO
H
O
intramolecular
nucleophilic addition
OBz
OBz
byproduct
BzO
OBz
BzO
BzO
OBz
6a
Scheme 3. The formation of the main byproduct.
2.2. HIV-RT inhibition assay
which indicated that both of them might be better accommo-
dated into the HIV-1 RT binding site. The inhibitory activities of the
tricyclic azasugars fused benzthiazinan-4-one 3~5(c–d) (bearing
phenyl group) are much higher than those of bicyclic azasugars fused
thiazolidin-4-one 3~4(a–b) and 5b, respectively, which indicated
that the phenyl group would be favorable to the HIV-RT inhibitory
activities of the compounds. Moreover, the inhibitory activities of
the bi/tricyclic azasugars 3~4(a–d) derived from glucoside and ga-
lactoside were more active than those of 5(b–d) derived from
mannoside, suggesting that the configuration of hydroxyl groups
would have certain effect on their anti-HIV-RT activities.
HIV-1 reverse transcriptase (RT) inhibitory activity was prelimi-
narily evaluated with the bi/tricyclic azasugars 3~4(a–d) and 5(b–d)
(Fig. 2) by determining their percentage inhibition of HIV-RT ac-
tivity in HIV-1-RT kit by comparison with AZT.32 The results are
shown in Table 3. It could be seen that all the newly synthesized
bi/tricyclic azasugars 3–5 except 5b showed significant HIV-RT in-
hibitory activity, better than that of positive control AZT. Especially,
compounds 3c and 4c showed a more significant HIV-RT inhibito-
ry activity with the IC50 value of 2.11 μM and 2.73 μM, respectively,
In conclusion, novel bi-/tricyclic seven-membered azasugars fused
thiazolidin-4-one and benzthiazinan-4-one 3~4(a–d) and 5(b–d)
were conveniently synthesized by the microwave-assisted one-
pot Staudinger/aza-Wittig/cyclization reaction. Bz migrations were
found in the cases using D-galactoside or D-mannoside as starting
materials, which was proved by HMBC and X-ray. All the newly syn-
thesized bi/tricyclic azasugars showed significant HIV-RT inhibitory
activity except 5b. Among them, compounds 3c and 4c were the
best ones with the IC50 values of RT inhibitory activities of 2.11 μM
and 2.73 μM, respectively. The structure activity relationship (SAR)
analysis indicated that the phenyl group in the tricyclic azasugars
would be favorable to their anti-HIV-RT inhibitory activity.
O
O
H
5
6
3
N
7
2
Bz
O
a
9
S
8
9
H
OBz
BzO
Fig. 3. Key HMBC (C→H) correlations of 9b.
Table 2
The coupling constants (Hz) of 9a-H and 9-H in 3~4(a-d) and 5(b-d)
3. Experiments
3.1. General methods
Cis (9aR)
J9a,9/Hz
Trans (9aS)
J9a,9/Hz
3b
3d
4b
4d
1.8
1.8
1.8
1.8
3a
3c
4a
4c
5b (9aR)
5d (9aR)
9.6
9.6
8.4
9.0
7.8
9.6
All microwave-assisted reactions were carried out on a CEM Dis-
cover S-Class Synthesizer (CEM Co. Ltd., USA). Melting points were
measured on an SGW® X-4 micro melting point apparatus and were
uncorrected. Optical rotations were determined on an SGW®-1 au-
tomatic polarimeter. 1H- and 13C- NMR spectra were measured on
5c (9aS)
1.8
4a
8d
Fig. 4. X-ray crystographical structure of 4a and 8d.
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Table 3
3.2.2. Synthesis of compounds 8(a-b), 9b, and 7–9(c-d)
In vitro HIV-1-RT kit assay for the bi/tricyclic azasugars
A mixture of azidosugar 6 (1.0 mmol) and PPh3 (393 mg,
1.5 mmol) was dissolved in 3 mL anhydrous toluene and was
stirred in sealed tube at 80 °C under microwave irradiation in a
CEM Discover S-Class Synthesizer for 10 min. After cooling,
2-mercaptobenzoic acid (2.0 mmol) and DCC (1.2 mmol) were added
and the mixture was stirred at 100 °C in sealed tube by irradiating
microwave for another 20 min reaction. After the reaction was
finished, solid K2CO3 was added to the solution to neutralize
2-mercaptobenzoic acid and then was removed with DCU by fil-
tration. Subsequently, the solution was extracted with CH2Cl2
(10 mL×3), then the organic layer was combined and dried with an-
hydrous MgSO4. The solvent was evaporated under reduced pressure
to get a crude product that was purified using flash column chro-
matography (ethyl acetate–cyclohexane V/V = 1:3~2:1) to get two
diastereoisomers 7c and 7d.
Compounds
IC50 (μM)
(HIV-RT kit assay)
Compounds
IC50 (μM)
(HIV-RT kit assay)
3a
3c
4a
4c
5b
5d
4.49 0.42
2.11 0.35
7.71 0.62
2.73 0.63
28.09 4.86
13.44 3.82
3b
3d
4b
4d
5c
11.01 1.15
3.44 0.38
6.84 0.57
5.51 0.49
17.17 3.31
20.14 1.32
AZT
an RT-NMR Bruker AVANCE 400 and a Bruker AVANCE 600 (400 MHz
and 600 MHz), NMR spectrometer using tetramethylsilane (Me4Si)
as an internal standard. Mass Spectra (MS) and High Resolution Mass
Spectra (HRMS) were carried out on an FTICR-MS (Ionspec 7.0T) mass
spectrometer with electrospray ionization (ESI). X-ray crystallo-
graphic measurements were made on a Bruker SMART CCD
Diffractometer. The optical densities for examining HIV-RT inhibi-
tion were measured on a BioRad Model 3550 microplate
spectrophotometer. Thin-layer chromatography (TLC) was per-
formed on precoated plates (Qingdao GF254) with detection of
phosphomolybdic acid in EtOH/H2O followed by heating. Column
chromatography was performed using SiO2 (Qingdao 300–400 mesh).
Using the same procedure, the iminosugars fused thiazolidin-
4-one 8(a-b) and 9b, and benzthiazinan-4-one 8–9(c-d) were
obtained.
(5aS,6R,7S,8R,9R)-9-hydroxy-12-oxo-6,7,8,9,10,12-hexahydro-
5aH-benzo[5,6][1,3]thiazino[3,2-a]azepine-6,7,8-triyl tribenzoate
(7c): white solid, yield 13.7 %, mp. 129–130 °C, [α] 22D +221.8 (c 1.0,
EtOAc), 1H NMR (600 MHz, CDCl3) δ (ppm) 8.16 (d, J = 7.2 Hz, 1H, CH),
8.05 (d, J = 7.2 Hz, 1H, CH), 7.89 (d, J = 7.2 Hz, 2H, CH), 7.71–7.74
(m, 1H, CH), 7.57–7.62 (m, 6H, CH), 7.45–7.48 (m, 3H, CH), 7.35–
7.38 (m, 1H, CH), 7.13–7.22 (m, 4H, CH), 5.90–5.96 (m, 2H, CH), 5.52
(d, J = 9.6 Hz, 1H, CH), 5.21 (d, J = 9.6 Hz, 1H, CH), 5.04–5.07 (m, 1H,
CH), 4.83–4.85 (m, 1H, CH), 3.54–3.58 (m, 1H, CH); 13C NMR
(150 MHz, CDCl3) δ (ppm) 165.3, 164.2, 163.8, 163.1, 133.8, 133.3,
133.2, 132.9, 130.4, 130.0, 129.7, 128.8, 128.7, 128.4, 128.2, 127.4,
126.7, 74.5, 74.3, 69.8, 65.3, 62.7, 50.9; HR-ESI-MS: calcd for
C34H27NO8SNa ([M + Na]+), 632.1355, found: 632.1361.
(5aR,6R,7S,8R,9R)-9-hydroxy-12-oxo-6,7,8,9,10,12-hexahydro-
5aH-benzo[5,6][1,3]thiazino[3,2-a]azepine-6,7,8-triyl tribenzoate
(7d): white solid, yield 6.8 %, mp. 206–207 °C, [α] 28D +167.4 (c 1.0,
CHCl3), 1H NMR (600 MHz, CDCl3) δ (ppm) 8.25 (d, J = 6.0 Hz, 1H,
CH), 8.04 (d, J = 6.0 Hz, 1H, CH), 7.84 (dd, J = 17.4 Hz, 7.8 Hz, 4H, CH),
7.41 (q, J = 15.0 Hz, 3H, CH), 7.23–7.33 (m, 4H, CH), 7.16 (d, J = 12.0 Hz,
2H, CH), 7.07–7.10 (m, 1H, CH), 6.96–7.01 (m, 3H, CH), 6.88
(d, J = 6.0 Hz, 1H, CH), 6.14 (dd, J = 9.0 Hz, 6.0 Hz, 1H, CH), 5.97 (dd,
J = 5.4 Hz, 3.6 Hz, 1H, CH), 5.72 (dd, J = 9.0 Hz, 1.8 Hz, 1H, CH), 5.20
(d, J = 5.4 Hz, 1H, CH), 5.10 (dd, J = 15.0 Hz, 3.0 Hz, 1H, CH2), 4.56 (brs,
1H, CH), 3.53 (dd, J = 15.0 Hz, 3.0 Hz, 1H, CH); 13C NMR (150 MHz,
CDCl3) δ (ppm) 167.1, 165.8, 164.9, 164.8, 134.6, 133.3, 132.9, 132.4,
130.6, 129.9, 129.7, 129.6, 128.9, 128.4, 128.3, 128.2, 128.0, 127.8,
126.9, 126.4, 125.6, 77.9, 72.9, 70.7, 60.3, 53.1, 52.1; HR-ESI-MS: calcd
for C34H27NO8SNa ([M + Na]+), 632.1355, found: 632.1376.
(6R,7S,8S,9R,9aS)-6-hydroxy-3-oxooctahydrothiazolo[3,2-
a]azepine-7,8,9-triyl tribenzoate (8a): oily, yield 10.2%, [α] 25D −80
(c 0.2, CH2Cl2), 1H NMR (600 MHz, CDCl3) δ (ppm) 8.09 (dd, J = 7.8 Hz,
1.2 Hz, 2H, Ph-H), 8.00 (dd, J = 8.4 Hz, 1.2 Hz, 2H, Ph-H), 7.95 (dd,
J = 8.4 Hz, 1.2 Hz, 2H, Ph-H), 7.39–7.62 (m, 9H, Ph-H), 6.03 (dd,
J = 8.4 Hz, 1.8 Hz, 1H, CH-8), 5.92 (dd, J = 7.8 Hz, 1.8 Hz, 1H, CH-7),
5.84 (dd, J = 7.8 Hz, 4.2 Hz, 1H, CH-9), 5.11 (dd, J = 4.2 Hz, 1.8 Hz, 1H,
CH-9a), 4.69–4.70 (m, 1H, CH-6), 4.43 (dd, J = 14.4 Hz, 4.8 Hz, 1H,
CH-5), 3.49 (d, J = 15.6 Hz, 1H, CH-2), 3.44 (d, J = 15.6 Hz, 1H, CH-2),
3.31 (dd, J = 14.4 Hz, 9.0 Hz, 1H, CH-5); 13C NMR (150 MHz, CDCl3)
δ (ppm) 171.6, 165.9, 165.3, 165.2, 133.8, 133.7, 133.6, 130.0, 129.8,
129.7, 129.2, 128.7, 128.7, 128.6, 74.6, 73.7, 71.4, 66.8, 63.4, 46.5, 31.7;
HR-ESI-MS: calcd for C29H25NO8SNa ([M + Na]+), 570.1198, found:
570.1186.
3.2. Experimental procedures
3.2.1. Synthesis of compounds 7a and 7b
A mixture of azidosugar 6a (1.0 mmol) and PPh3 (393 mg,
1.5 mmol) was dissolved in 3 mL anhydrous toluene and was stirred
in sealed tube at 80 °C under microwave irradiation in a CEM Dis-
cover S-Class Synthesizer for 10 min. After cooling, mercaptoacetic
acid (140 μL, 2.0 mmol) was added and the mixture was stirred at
80 °C in sealed tube by irradiating microwave for another 15 min
reaction. After the reaction was finished, solid K2CO3 was added to
the solution to neutralize mercaptoacetic acid and then was removed
by filtration. Subsequently, the solution was extracted with CH2Cl2
(10 mL×3), then the organic layer was combined and dried with an-
hydrous MgSO4. The solvent was evaporated under reduced pressure
to get a crude product that was purified using flash column chro-
matography (ethyl acetate–cyclohexane V/V = 1:3~2:1) to get two
diastereoisomers 7a and 7b.
(6R,7R,8S,9R,9aS)-6-hydroxy-3-oxooctahydrothiazolo[3,2-
a]azepine-7,8,9-triyl tribenzoate (7a): white solid, yield 35.5 %, mp.
219–221 °C, [α] 30D −119.1 (c 1.0, CHCl3), 1H NMR (400 MHz, CDCl3)
δH (ppm): 7.90 (brs, 4H, Bz-H), 7.76 (d, J = 7.6 Hz, 2H, Bz-H), 7.21–
7.50 (m, 9H, Bz-H), 6.23 (t, J = 8.8 Hz, 1H, CH), 5.58 (t, J = 9.2 Hz, 1H,
CH), 5.45 (d, J = 9.6 Hz, 1H, CH), 5.59 (d, J = 10.0 Hz, 1H, CH), 4.61
(brs, 1H, CH), 3. 93 (d, J = 14.4 Hz, 1H, CH), 3.74 (d, J = 15.6 Hz, 1H,
CH2), 3.54 (d, J = 14.8 Hz, 1H, CH2), 3.36–3.40 (m, 2H, CH2, OH); 13
C
NMR (100 MHz, CDCl3) δ (ppm): 172.6, 165.7, 165.5, 165.3, 133.6,
133.4, 133.3, 129.8, 129.8, 129.6, 129.0, 128.8, 128.5, 128.4, 128.3,
75.0, 74.7, 711, 68.8, 60.6, 47.3, 30.5; HR-ESI-MS: calcd for C29H26NO8S
([M + H]+), 548.1379, found: 548.1365.
(6R,7R,8S,9R,9aR)-6-hydroxy-3-oxooctahydrothiazolo[3,2-
a]azepine-7,8,9-triyl tribenzoate (7b): white solid, yield 20.1 %, mp.
96–98 °C, [α] 30D +25.6 (c 1.0, CHCl3), 1H NMR (400 MHz, CDCl3) δH
(ppm): 7.85–7.95 (m, 7H, Bz-H), 7.21–7.50 (m, 8H, Bz-H), 5.86
(q, J = 7.0 Hz, 1H, CH), 5.60–5.65 (m, 2H, 2CH), 5.35 (s, 1H, CH), 4.60
(brs, 1H, CH), 4.41 (q, J = 14.2 Hz, 1H, CH), 3.59 (d, J = 15.6 Hz, 1H,
CH2), 3.39–3.45 (m, 2H, CH2), 3.33 (1H, d, J = 5.4 Hz, OH);13C NMR
(100 MHz, CDCl3) δ (ppm): 172.8, 166.2, 164.6, 164.5, 133.7, 133.6,
133.6, 129.9, 129.8, 128.7, 128.5, 128.4, 76.6, 76.1, 70.2, 68.0, 60.1,
46.0, 32.4; HR-ESI-MS: calcd for C29H25NO8SNa ([M + Na]+), 570.1198,
found: 570.1206.
(6R,7S,8S,9R,9aR)-6-hydroxy-3-oxooctahydrothiazolo[3,2-
a]azepine-7,8,9-triyl tribenzoate (8b): oily, yield 8.2%, [α] 25D +120
(c 0.2, CH2Cl2), 1H NMR (600 MHz, CDCl3) δ (ppm) 8.06–8.08 (m, 4H,
Ph-H), 7.94 (dd, J = 7.8 Hz, 1.2 Hz, 2H, Ph-H), 7.38–7.62 (m, 9H, Ph-H),
6.02–6.06 (m, 2H, CH-8, CH-9), 5.77 (d, J = 6.0 Hz, 1H, CH-7), 5.30
Please cite this article in press as: Yuheng Hou, et al., Synthesis of seven-membered iminosugars fused thiazolidin-4-one and benzthiazinan-4-one and their HIV-RT inhibitory activ-
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Y. Hou et al./Carbohydrate Research ■■ (2016) ■■–■■
(dd, J = 3.6 Hz, 1.2 Hz, 1H, CH-9a), 4.46 (dd, J = 15.0 Hz, 2.4 Hz, 1H,
CH-5), 4.35 (brs, 1H, CH-6), 3.69–3.72 (m, 2H, CH-5, CH-2), 3.54
(d, J = 15.6 Hz, 1H, CH-2), 3.29 (d, J = 4.8 Hz, OH); 13C NMR (150 MHz,
CDCl3) δ (ppm) 173.8, 165.6, 164.8, 164.6, 133.7, 133.6, 133.5, 130.0,
129.9, 129.7, 129.3, 128.9, 128.7, 128.6, 128.5, 75.3, 71.0, 70.6, 70.2,
62.5, 47.5, 32.6; HR-ESI-MS: calcd for C29H25NO8SNa ([M + Na]+),
570.1198, found: 570.1203.
(5aS,6R,7S,8S,9R)-8-hydroxy-12-oxo-6,7,8,9,10,12-hexahydro-
5aH-benzo[5,6][1,3]thiazino[3,2-a]azepine-6,7,9-triyl tribenzoate
(8c): oily, yield 7.5%, [α] 25D +75 (c 0.2, CH2Cl2), 1H NMR (600 MHz,
CDCl3) δ (ppm) 8.11 (d, J = 7.2 Hz, 2H, Bz-H), 8.01 (d, J = 7.2 Hz, 2H,
Bz-H), 7.97 (d, J = 7.2 Hz, 2H, Bz-H), 7.89 (d, J = 7.2 Hz, 1H, Bz-H), 7.11–
7.63 (m, 12H, Bz-H), 5.91 (brs, 1H, CH), 5.78 (d, J = 9.0 Hz, 1H, CH),
5.60 (brs, 1H, CH), 5.18 (d, J = 14.4 Hz, 6.6 Hz, 1H, CH-5), 4.90–4.96
(m, 2H, 2CH), 3.24 (dd, J = 14.4 Hz, 9.0 Hz, 1H, CH-5), 3.09 (brs, 1H,
OH); 13C NMR (150 MHz, CDCl3) δ (ppm) 165.9, 164.6, 164.5, 162.8,
133.6, 133.5, 133.0, 132.7, 130.5, 130.1, 130.0, 130.0, 129.2, 129.0,
128.7, 128.6, 128.4, 128.4, 128.2, 127.6, 126.6, 75.3, 73.9, 73.8, 66.5,
62.9, 52.1; HR-ESI-MS: calcd for C34H27NO8SNa ([M + Na]+), 632.1355,
found: 632.1381.
(d, J = 16.2 Hz, 1H, CH-2), 3.57 (d, J = 15.6 Hz, 1H, CH-2), 3.47 (dd,
J = 14.4 Hz, 2.4 Hz, 1H, CH-5); 13C NMR (150 MHz, CDCl3) δ (ppm)
171.5, 165.9, 165.5, 133.9, 133.6, 133.3, 129.9, 129.9, 129.8, 129.5,
129.0, 128.9, 128.8, 128.6, 128.5, 77.1, 72.8, 68.0, 67.5, 61.2, 42.5, 31.8;
HR-ESI-MS: calcd for C29H25NO8SNa ([M + Na]+), 570.1198, found:
570.1212.
(6R,7R,8S,9S,9aR)-9-hydroxy-3-oxooctahydrothiazolo[3,2-
a]azepine-6,7,8-triyl tribenzoate (9b-3): white solid, yield 12.5%,
mp. 120–122 °C, [α] 25D −55 (c 0.2, CH2Cl2), 1H NMR (600 MHz, CDCl3)
δ (ppm) 8.00 (d, J = 7.2 Hz, 2H, Bz-H), 7.91 (d, J = 7.2 Hz, 2H, Bz-H),
7.78 (d, J = 7.8 Hz, 2H, Bz-H), 7.58-7.21 (m, 9H, Bz-H), 6.19 (dd,
J = 9.6 Hz, 3.6 Hz, 1H, CH-7), 6.06 (d, J = 9.6 Hz, 1H, CH-8), 5.74 (brs,
1H, CH-6), 5.04 (brs, 1H, CH-9a), 4.58 (dd, J = 15 Hz, 5.4 Hz, 1H, CH-5),
4.30 (brs, 1H, CH-9), 3.61 (t, J = 16.2 Hz, 2H, CH-2), 3.46 (d, J = 14.4 Hz,
1H, CH-5); 13C NMR (150 MHz, CDCl3) δ (ppm) 171.4, 165.6, 165.5,
165.4, 133.4, 133.3, 133.2, 129.7, 129.7, 129.0, 129.0, 128.5, 128.4,
128.3, 74.8, 70.4, 69.9, 68.3, 63.9, 41.8, 32.3; HR-ESI-MS: calcd for
C29H25NO8SNa ([M + Na]+), 570.1198, found: 570.1201.
(5aS,6S,7S,8R,9R)-9-hydroxy-12-oxo-6,7,8,9,10,12-hexahydro-
5aH-benzo[5,6][1,3]thiazino[3,2-a]azepine-6,7,8-triyl tribenzoate
(9c): oily, yield 9.5%, [α] 25D −10 (c 0.2, CH2Cl2), 1H NMR (150 MHz,
CDCl3) δ (ppm) 8.05 (d, J = 7.8 Hz, 1H, Bz-H), 7.93 (d, J = 7.2 Hz, 2H,
Bz-H), 7.74 (d, J = 7.2 Hz, 2H, Bz-H), 7.68 (d, J = 7.2 Hz, 2H, Bz-H),
6.99–7.55 (m, 12H, Bz-H), 6.18 (t, J = 2.4 Hz, 1H, CH-7), 6.12 (dd,
J = 10.2 Hz, 3.0 Hz, 1H, CH-8), 5.85 (dd, J = 9.6 Hz, 2.4 Hz, 1H, CH-9),
5.46 (d, J = 1.8 Hz, 1H, CH-9a), 4.80–4.83 (m, 1H, CH-6), 4.78 (dd,
J = 14.4 Hz, 4.8 Hz, 1H, CH-5) 4.01 (dd, J = 14.4 Hz, 5.4 Hz, 1H, CH-5),
13C NMR (150 MHz, CDCl3) δ (ppm) 165.4, 164.9, 164.6, 134.7, 133.4,
133.3, 133.2, 131.9, 130.6, 129.9, 129.8, 129.7, 129.1, 128.8, 128.6,
128.4, 128.2, 127.9, 126.5, 125.6, 74.4, 72.5, 69.6, 67.9, 60.4, 47.8;
HR-ESI-MS: calcd for C34H27NO8SNa ([M + Na]+), 632.1355, found:
632.1359.
(5aR,6R,7S,8S,9R)-8-hydroxy-12-oxo-6,7,8,9,10,12-hexahydro-
5aH-benzo[5,6][1,3]thiazino[3,2-a]azepine-6,7,9-triyl tribenzoate
25
(8d): white solid, yield 6.2%, mp. 109–110 °C, [α]
−25 (c 0.2,
D
CH2Cl2), 1H NMR (600 MHz, CDCl3) δ (ppm) 8.27 (d, J = 7.8 Hz, 2H,
Bz-H), 8.21 (dd, J = 7.8 Hz, 1.2 Hz, 1H, Bz-H), 7.88 (dd, J = 7.2 Hz, 1.2 Hz,
2H, Bz-H), 7.12–7.64 (m, 14H, Bz-H), 6.14 (dd, J = 7.8 Hz, 4.2 Hz, 1H,
CH), 5.71 (d, J = 7.8 Hz, 1H, CH), 5.51 (d, J = 4.2 Hz, 1H, CH), 5.40–
5.42 (m, 1H, CH), 5.19 (d, J = 15.0 Hz, 1H, CH-5), 4.61 (t, J = 5.4 Hz,
1H, CH), 4.25 (s, 1H, OH), 3.61 (dd, J = 15.0 Hz, 2.4 Hz, 1H, CH-5);
13C NMR (150 MHz, CDCl3) δ (ppm) 166.2, 166.0, 165.3, 162.9, 135.1,
133.3, 133.3, 133.0, 132.0, 130.4, 130.3, 129.8, 129.8, 129.6, 129.3,
129.1, 128.6, 128.4, 128.3, 128.2, 127.9, 126.3, 125.6, 125.3, 76.7, 76.5,
72.7, 72.2, 59.9, 49.2; HR-ESI-MS: calcd for C34H27NO8SNa ([M + Na]+),
632.1355, found: 632.1356.
(5aR,6S,7S,8R,9R)-9-hydroxy-12-oxo-6,7,8,9,10,12-hexahydro-
5aH-benzo[5,6][1,3]thiazino[3,2-a]azepine-6,7,8-triyl tribenzoate
25
(6R,7R,8S,9S,9aR)-6-hydroxy-3-oxooctahydrothiazolo[3,2-
a]azepine-7,8,9-triyl tribenzoate (9b): oily, yield 9.5%, [α] 25D −67
(c 0.2, CH2Cl2), 1H NMR (600 MHz, CDCl3) δ (ppm) 8.13 (d, J = 7.2 Hz,
2H, Bz-H), 7.96 (d, J = 7.2 Hz, 2H, Bz-H), 7.85 (d, J = 7.2 Hz, 2H, Bz-H),
7.27–7.69 (m, 9H, Bz-H), 6.28 (dd, J = 9.6 Hz, 1.2 Hz, 1H, CH-8), 6.05
(dd, J = 9.6 Hz, 3.0 Hz, 1H, CH-7), 5.70 (t, J = 1.8 Hz, 1H, CH-9), 5.11
(d, J = 1.8 Hz, 1H, CH-9a), 4.54–4.59 (m, 2H, CH-6, CH-5), 3.79 (dd,
J = 15.6 Hz, 1.8 Hz, 1H, CH-2), 3.71 (dd, J = 15.6 Hz, 0.6 Hz, 1H, CH-2),
3.41 (d, J = 14.4 Hz, 1H, CH-5); 13C NMR (150 MHz, CDCl3) δ (ppm)
172.8, 165.9, 165.1, 165.0, 134.0, 133.4, 133.3, 129.9, 129.8, 129.7,
129.0, 128.9, 128.9, 128.4, 128.3, 76.3, 72.4, 67.8, 67.7, 62.8, 44.5,
32.4; HR-ESI-MS: calcd for C29H25NO8SNa ([M + Na]+), 570.1198,
found: 570.1195.
(9d): white solid, yield 10.5%, mp. 225–227 °C, [α]
+115 (c 0.2,
D
CH2Cl2), 1H NMR (600 MHz, CDCl3) δ (ppm) 8.25 (d, J = 7.8 Hz, Bz-H),
7.94–7.98 (m, 6H, Bz-H), 7.23–7.62 (m, 12H, Bz-H), 6.24 (dd, J = 8.4 Hz,
3.0 Hz, 1H, CH), 5.99 (dd, J = 8.4 Hz, 4.8 Hz, 1H, CH), 5.94
(dd, J = 9.6 Hz, 3.0 Hz, 1H, CH), 5.07 (d, J = 9.6 Hz, 1H, CH), 5.00
(d, J = 13.8 Hz, 1H, CH-5), 4.54–4.55 (m, 1H, CH), 4.28–4.29 (d,
J = 9.6 Hz, 1H, CH) 3.77 (dd, J = 15.6 Hz, 4.8 Hz, 1H, CH-5); 13C NMR
(150 MHz, CDCl3) δ (ppm) 165.6, 165.2, 164.7, 164.6, 133.7, 133.5,
133.4, 131.2, 130.0, 129.9, 129.6, 128.7, 128.5, 128.3, 127.7, 126.5,
70.2, 70.1, 70.0, 69.7, 62.0, 53.4; HR-ESI-MS: calcd for C34H27NO8SNa
([M + Na]+), 632.1355, found: 632.1365.
(6R,7R,8S,9S,9aR)-7-hydroxy-3-oxooctahydrothiazolo[3,2-
a]azepine-6,8,9-triyl tribenzoate (9b-1): oily, yield 7.5%, [α] 25D −35
(c 0.2, CH2Cl2), 1H NMR (600 MHz, CDCl3) δ (ppm) 8.05–8.11 (m, 6H,
Bz-H), 7.46–7.69 (m, 12H, Bz-H), 6.07 (dd, J = 9.0 Hz, 1.2 Hz, 1H, CH-8),
5.77 (dd, J = 3.0 Hz, 1.8 Hz, 1H, CH-9), 5.68–5.70 (m, 1H, CH-6), 5.10
(t, J = 1.8 Hz, 1H, CH-7), 4.73 (dd, J = 14.4 Hz, 5.4 Hz, 1H, CH-5), 4.67
(brs, 1H, CH-9a), 3.63 (d, J = 17.4 Hz, 1H, CH-2), 3.58 (d, J = 14.4 Hz,
1H, CH-2), 3.39 (dd, J = 15.0 Hz, 1.8 Hz, 1H, CH-5); 13C NMR (150 MHz,
CDCl3) δ (ppm) 171.3, 166.1, 165.7, 164.9, 134.0, 133.6, 133.4, 129.9,
129.9, 129.8, 129.8, 129.5, 129.2, 129.0, 128.9, 128.8, 128.6, 128.5,
75.4, 70.5, 70.5, 70.1, 62.2, 42.0, 32.0; HR-ESI-MS: calcd for
C29H25NO8SNa ([M + Na]+), 570.1198, found: 570.1187.
3.2.3. Synthesis of compounds 3~4(a-d) and 5(b-d)
Compounds 7~8(a–d) or 9(b–d) (1 mmol) were dissolved in 10 mL
anhydrous methanol. The solution was stirred under nitrogen at-
mosphere at room temperature for 5 min, and then sodium
methoxide (54 mg, 1 mmol) was added to the solution; the solu-
tion was stirred for another 30 min. After the reaction was finished,
Cationic resin H+ (Dowex-50) was added to the solution to neutral-
ize sodium methoxide and then was removed by filtration. The
solvent was evaporated under reduced pressure to get a crude
product that was purified using flash column chromatography (ethyl
acetate–methanol V/V = 5:1~3:1) to get compounds 3~4(a–d) and
5(b–d), respectively.
(6R,7R,8S,9S,9aR)-8-hydroxy-3-oxooctahydrothiazolo[3,2-
a]azepine-6,7,9-triyl tribenzoate (9b-2): oily, yield 8.5%, [α] 25D −110
(c 0.2, CH2Cl2), 1H NMR (600 MHz, CDCl3) δ (ppm) 8.10 (dd, J = 8.4 Hz,
1.2 Hz, 2H, Bz-H), 7.95–7.97 (m, 4H, Bz-H), 7.39–7.66 (m, 9H, Bz-H),
5.91–5.93 (m, 1H, CH-6), 5.87 (dd, J = 8.4 Hz, 3.0 Hz, 1H, CH-7), 5.54
(dd, J = 4.2 Hz, 1.8 Hz, 1H, CH-9), 5.16 (d, J = 4.2 Hz, 1H, CH-9a), 4.72–
4.74 (m, 1H, CH-8), 4.58 (dd, J = 14.4 Hz, 6.6 Hz, 1H, CH-5), 3.65
(6R,7R,8S,9R,9aS)-6,7,8,9-tetrahydroxyhexahydrothiazolo[3,2-
a]azepin-3(2H)-one (3a): white solid, yield 70.5%, mp. 193–195 °C,
[α] 20D −107.6 (c 1.0, CH3OH), 1H NMR (600 MHz, CD3OD) δH (ppm):
4.84 (dd, J = 9.6 Hz, 1.8 Hz, 1H, CH-9a), 4.11–4.12 (m, 1H, CH); 3.70
(dd, J = 11.4 Hz, 3.6 Hz, 1H, CH), 3.69 (d, J = 8.4 Hz, 1H, CH), 3.53 (dd,
J = 16.2 Hz, 1.8 Hz, 1H, CH2), 3.49 (dd, J = 9.0 Hz, 1.8 Hz, 1H, CH2), 3.31–
3.36 (m, 3H, CH2, CH); 13C NMR (150 MHz, CD3OD) δ (ppm): 173.6,
Please cite this article in press as: Yuheng Hou, et al., Synthesis of seven-membered iminosugars fused thiazolidin-4-one and benzthiazinan-4-one and their HIV-RT inhibitory activ-
ity, Carbohydrate Research (2016), doi: 10.1016/j.carres.2016.02.011

ARTICLE IN PRESS
Y. Hou et al./Carbohydrate Research ■■ (2016) ■■–■■
7
76.9, 74.1, 74.0, 68.8, 64.1, 46.7, 29.8; HR-ESI-MS: calcd for
C8H13NO5SNa ([M + Na]+), 258.0412, found: 258.0422.
(600 MHz, CD3OD) δ (ppm) 8.03 (dd, J = 7.8 Hz, 1.2 Hz, 1H, Ph-H),
7.37–7.39 (m, 1H, Ph-H), 7.29 (d, J = 7.8 Hz, 1H, Ph-H), 7.20–7.23
(m, 1H, Ph-H), 5.11 (d, J = 1.8 Hz, 1H, CH-9a), 4.29 (dd, J = 14.4 Hz,
2.4 Hz, 1H, CH-5), 3.98–4.03 (m, 2H, 2CH), 3.81–3.88 (m, 3H, 3CH);
13C NMR (150 MHz, CD3OD) δ (ppm) 165.9, 137.0, 131.6, 129.2, 127.8,
125.9, 124.7, 76.9, 75.1, 73.8, 72.7, 61.8, 51.9; HR-ESI-MS: calcd for
C13H15NO5SNa ([M + Na]+), 320.0568, found: 320.0553.
(6R,7R,8S,9S,9aR)-6,7,8,9-tetrahydroxyhexahydrothiazolo[3,2-
a]azepin-3(2H)-one (5b): white solid, yield 70.5%, mp. 152–153 °C,
[α] 25D −60 (c 0.2, MeOH), 1H NMR (600 MHz, CD3OD) δ (ppm) 4.96
(dd, J = 7.8 Hz, 1.2 Hz,1H, CH-9a), 4.15–4.16 (m, 1H, CH), 4.02 (s, 2H,
CH), 3.97 (dd, J = 13.8 Hz, 7.2 Hz, 1H, CH), 3.86 (d, J = 5.4 Hz, 1H, CH),
3.55 (brs, 2H, CH), 3.28 (dd, J = 13.8 Hz, 3.0 Hz, 1H, CH); 13C NMR
(150 MHz, CDCl3) δ (ppm) 173.1, 73.8, 70.4, 67.1, 63.6, 44.1, 31.0; HR-
ESI-MS: calcd for C8H13NO5SNa ([M + Na]+), 258.0412, found:
258.0407.
(5aS,6S,7S,8R,9R)-6,7,8,9-tetrahydroxy-7,8,9,10-tetrahydro-
5aH-benzo[5,6][1,3]thiazino[3,2-a]azepin-12(6H)-one (5c): white
solid, yield 65.5%, mp. > 250 °C, [α] 25D +25 (c 0.2, MeOH), 1H NMR
(600 MHz, CD3OD) δ (ppm) 7.89 (dd, J = 8.4 Hz, 1.8 Hz, 1H, Ph-H),
7.33–7.36 (m, 1H, Ph-H), 7.28 (d, J = 7.8 Hz, 1H, Ph-H), 7.18–7.21 (m,
1H, Ph-H), 5.07 (d, J = 1.8 Hz, 1H, CH-9a), 4.10 (t, J = 1.8 Hz, 1H, CH),
4.03–4.04 (m, 1H, CH), 3.95 (dd, J = 13.8 Hz, 7.2 Hz, 1H, CH-5), 3.88
(dd, J = 14.4 Hz, 3.0 Hz, 1H, CH-5), 3.68 (dd, J = 8.0 Hz, 1.8 Hz, 1H, CH),
3.62 (dd, J = 8.4 Hz, 2.4 Hz, 1H, CH); 13C NMR (150 MHz, CDCl3) δ
(ppm) 166.0, 137.6, 131.4, 129.8, 128.7, 126.2, 125.0, 75.5, 72.1, 71.8,
68.3, 63.5, 60.9; HR-ESI-MS: calcd for C13H15NO5SNa ([M + Na]+),
320.0568, found: 320.0549.
(5aR,6S,7S,8R,9R)-6,7,8,9-tetrahydroxy-7,8,9,10-tetrahydro-
5aH-benzo[5,6][1,3]thiazino[3,2-a]azepin-12(6H)-one (5d): white
solid, yield 72.0%, mp. 208–209 °C, [α] 25D +65 (c 0.2, MeOH), 1H NMR
(600 MHz, CD3OD) δ (ppm) 8.01 (d, J = 7.8 Hz, 1H, Ph-H), 7.45
(t, J = 7.2 Hz, 1H, Ph-H), 7.38 (d, J = 7.8 Hz, 1H, Ph-H), 7.30 (t, J = 7.8 Hz,
1H, Ph-H), 4.84 (d, J = 9.6 Hz, 1H, CH-9a), 4.31 (d, J = 10.8 Hz, 1H, CH),
4.18 (dd, J = 9.6 Hz, 1.8 Hz, 1H, CH), 4.15 (dd, J = 6.6 Hz, 2.4 Hz, 1H,
CH), 4.08–4.10 (m, 1H, CH), 4.05 (dd, J = 7.2 Hz, 3.0 Hz, 1H, CH), 3.67
(dd, J = 14.4 Hz, 3.6 Hz, 1H, CH-5); 13C NMR (150 MHz, CDCl3) δ (ppm)
165.5, 131.9, 129.9, 128.4, 127.3, 125.6, 71.6, 69.7, 68.7, 63.3, 48.3;
HR-ESI-MS: calcd for C13H15NO5SNa ([M + Na]+), 320.0568, found:
320.0574.
(6R,7R,8S,9R,9aR)-6,7,8,9-tetrahydroxyhexahydrothiazolo[3,2-
a]azepin-3(2H)-one (3b): white solid, yield 83.0%, mp. 70–73 °C,
30
1
[α]
+38.6 (c 1.0, CH3OH), H NMR (600 MHz, CD3OD) δH (ppm):
D
5.04 (d, J = 1.8 Hz, 1H, CH-9a), 4.20 (dd, J = 8.4 Hz, 2.4 Hz,1H, CH),
4.14–4.18 (m, 1H, CH), 3.92 (d, J = 1.8 Hz, 2H, 2CH), 3.86 (brs, 1H,
CH), 3.82 (dd, J = 15.0 Hz 1.2 Hz, 1H, CH2), 3.40 (d, J = 15.6 Hz, 1H,
CH2), 3.15 (dd, J = 13.2 Hz 1.2 Hz, 1H, CH2); 13C NMR (150 MHz,
CD3OD) δ (ppm): 170.0, 80.2, 78.9, 73.7, 69.1, 60.5, 45.5, 31.8; HR-
ESI-MS: calcd for C8H13NO5SNa ([M + Na]+), 258.0412, found:
258.0408.
(5aS,6R,7S,8R,9R)-6,7,8,9-tetrahydroxy-7,8,9,10-tetrahydro-
5aH-benzo[5,6][1,3]thiazino[3,2-a]azepin-12(6H)-one (3c): white
30
solid, yield 50.0%, mp. 213–215 °C, [α]
−97.5 (c 1.0, MeOH), 1H
D
NMR (600 MHz, CD3OD) δ (ppm) 8.00 (d, J = 8.0 Hz, 1H, CH), 7.43
(td, J = 7.8 Hz, 1.2 Hz, 1H, CH), 7.34 (d, J = 7.8 Hz, 1H, CH), 7.29–7.31
(m, 1H, CH), 4.85 (d, J = 9.6 Hz, 1H, CH-9a), 4.48 (dd, J = 13.2 Hz, 6.0 Hz,
1H, CH), 4.36–4.38 (m, 1H, CH), 4.09–4.13 (m, 1H, CH), 3.66
(d, J = 9.6 Hz, 1H, CH2), 3.23–3.27 (m, 1H, CH2); 13C NMR (150 MHz,
CD3OD) δ (ppm) 163.5, 134.3, 131.9, 129.6, 128.4, 127.7, 125.6, 76.4,
74.7, 74.3, 66.0, 64.4, 48.8; HR-ESI-MS: calcd for C13H15NO5SNa
([M + Na]+), 320.0568, found: 320.0580.
(5aR,6R,7S,8R,9R)-6,7,8,9-tetrahydroxy-7,8,9,10-tetrahydro-
5aH-benzo[5,6][1,3]thiazino[3,2-a]azepin-12(6H)-one (3d): white
solid, yield 51.1%, mp. 153–155 °C, [α] 28D −260.0 (c 5.0, MeOH), 1H
NMR (600 MHz, CD3OD) δ (ppm) 7.96 (dd, J = 7.8 Hz, 0.6 Hz, 1H, CH),
7.36 (td, J = 7.8 Hz, 1.2 Hz, 1H, CH), 7.27 (d, J = 7.8 Hz, 1H, CH), 7.21–
7.23 (m, 1H, CH), 5.05 (d, J = 1.8 Hz, 1H, CH-9a), 4.52 (q, J = 7.2 Hz,
1H, CH), 4.12–4.14 (m, 2H, CH), 3.97–3.99 (m, 1H, CH2), 3.94–3.95
(m, 1H, CH2), 3.62 (dd, J = 14.4 Hz, 3.6 Hz, 1H, CH); 13C NMR (150 MHz,
CD3OD) δ (ppm) 165.5, 136.4, 131.5, 129.4, 128.8, 126.2, 125.1, 80.0,
76.2, 71.2, 69.5, 60.0, 46.3; HR-ESI-MS: calcd for C13H15NO5SNa
([M + Na]+), 320.0568, found: 320.0571.
(6R,7S,8S,9R,9aS)-6,7,8,9-tetrahydroxyhexahydrothiazolo[3,2-
a]azepin-3(2H)-one (4a): white solid, yield 62.5%, mp. 98–99 °C,
[α] 25D −45 (c 0.2, MeOH), 1H NMR (600 MHz, CD3OD) δ (ppm) 4.68
(dd, J = 8.4 Hz, 1.8 Hz, 1H, CH-9a), 3.92–4.05 (m, 5H, CH-5, CH-6, CH-7,
CH-8, CH-9), 3.64 (dd, J = 15.6 Hz, 2.4 Hz, 1H, CH-2), 3.43
(d, J = 15.6 Hz, 1H, CH-2), 3.06 (dd, J = 15.0 Hz, 9.6 Hz, 1H, CH-5); 13
C
NMR (150 MHz, CD3OD) δ (ppm) 172.8, 75.1, 74.5, 73.2, 68.0, 66.3,
46.1, 30.6; HR-ESI-MS: calcd for C8H13NO5SNa ([M + Na]+), 258.0412,
found: 258.0419.
3.3. In vitro HIV-RT kit assay
(6R,7S,8S,9R,9aR)-6,7,8,9-tetrahydroxyhexahydrothiazolo[3,2-
a]azepin-3(2H)-one (4b): white solid, yield 65.5%, mp. 93–94 °C,
[α] 25D +55 (c 0.2, MeOH), 1H NMR (600 MHz, CD3OD) δ (ppm) 5.08
(t, J = 1.8 Hz, 1H, CH-9a), 4.02 (dd, J = 6.0 Hz, 1.8 Hz, 1H, CH-7), 3.97–
4.00 (m, 1H, CH), 3.89 (dd, J = 6.0 Hz, 1.8 Hz, 1H, CH), 3.70–3.78 (m,
3H, CH, CH-5, CH-2), 3.47 (dd, J = 13.8 Hz, 4.2 Hz, 1H, CH-5), 3.40
(d, J = 15.0 Hz, 1H, CH-2); 13C NMR (150 MHz, CD3OD) δ (ppm) 173.9,
74.2, 73.2, 72.9, 68.4, 61.9, 32.0; HR-ESI-MS: calcd for C8H13NO5SNa
([M + Na]+), 258.0412, found: 258.0430.
(5aS,6R,7S,8S,9R)-6,7,8,9-tetrahydroxy-7,8,9,10-tetrahydro-
5aH-benzo[5,6][1,3]thiazino[3,2-a]azepin-12(6H)-one (4c): white
solid, yield 75.5%, mp. 237–238 °C, [α] 25D +20 (c 0.2, MeOH), 1H NMR
(600 MHz, CD3OD) δ (ppm) 8.00 (dd, J = 7.8 Hz, 1.2 Hz, 1H, Ph-H),
7.42–7.45 (m, 1H, Ph-H), 7.34 (d, J = 7.8 Hz, 1H, Ph-H), 7.28–7.31 (m,
1H, Ph-H), 4.64 (dd, J = 13.8 Hz, 6.0 Hz, 1H, CH), 4.42 (d, J = 9.0 Hz,
1H, CH-9a), 4.25–4.29 (m, 1H, CH), 3.97 (d, J = 3.6 Hz, 1H, CH), 3.76–
3.79 (m, 2H, 2CH), 2.91 (dd, J = 13.8 Hz, 10.2 Hz, 1H, CH-5); 13C NMR
(150 MHz, CD3OD) δ (ppm) 163.6, 134.2, 131.8, 129.7, 128.7, 127.6,
125.6, 77.7, 73.9, 73.7, 66.5, 65.9, 52.0; HR-ESI-MS: calcd for
C13H15NO5SNa ([M + Na]+), 320.0568, found: 320.0574.
The HIV-RT inhibition assay was performed by using an RT assay
kit (Roche), and the procedure for assaying RT inhibition was per-
formed as described in the kit protocol. Briefly, the reaction mixture
consists of template/primer complex, 2′-deoxy-nucleotide-5′-
triphosphates (dNTPs) and reverse transcriptase (RT) enzyme in the
lysis buffer with or without inhibitors. After 1 h incubation at 37 °C
the reaction mixture was transferred to streptavidine-coated
microtiter plate (MTP). The biotin labeled dNTPs that are incorpo-
rated in the template due to activity of RT were bound to
streptavidine. The unbound dNTPs were washed using wash buffer
and antidigoxigenin-peroxidase (DIG-POD) was added in MTP. The
DIG-labeled dNTPs incorporated in the template was bound to anti-
DIG-POD antibody. The unbound anti-DIG-POD was washed and the
peroxide substrate (ABST) was added to the MTP. A colored reac-
tion product was produced during the cleavage of the substrate
catalyses by a peroxide enzyme. The absorbance of the sample was
determined at OD 405 nM using microtiter plate ELISA reader. The
resulting color intensity is directly proportional to the actual RT ac-
tivity. The percentage inhibitory activity of RT inhibitors was
calculated by comparing to a sample that does not contain an in-
hibitor. The percentage inhibition was calculated by formula as given
below: % Inhibition = 100 − [(OD 405 nm with inhibitor/OD 405 nm without
inhibitor) × 100].
(5aR,6R,7S,8S,9R)-6,7,8,9-tetrahydroxy-7,8,9,10-tetrahydro-
5aH-benzo[5,6][1,3]thiazino[3,2-a]azepin-12(6H)-one (4d): white
solid, yield 80.5%, mp. 211–213 °C, [α] 25D −40 (c 0.2, MeOH), 1H NMR
Please cite this article in press as: Yuheng Hou, et al., Synthesis of seven-membered iminosugars fused thiazolidin-4-one and benzthiazinan-4-one and their HIV-RT inhibitory activ-
ity, Carbohydrate Research (2016), doi: 10.1016/j.carres.2016.02.011

ARTICLE IN PRESS
8
Y. Hou et al./Carbohydrate Research ■■ (2016) ■■–■■
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We would like to acknowledge the financial support from the
National Natural Science Foundation of China (NSFC) (21372060),
Hebei Province Natural Science Fund for Distinguished Young Schol-
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Please cite this article in press as: Yuheng Hou, et al., Synthesis of seven-membered iminosugars fused thiazolidin-4-one and benzthiazinan-4-one and their HIV-RT inhibitory activ-
ity, Carbohydrate Research (2016), doi: 10.1016/j.carres.2016.02.011