Concise and practical route to tri- and tetra-hydroxy seven-membered iminocyclitols as glycosidase inhibitors from d-(+)-glucurono-γ-lactone

Article abstract of DOI:10.1016/j.tet.2010.08.060

An efficient and short total synthesis of tetrahydroxy-1c and trihydroxy-azepane 1d is reported in 72% and 57% overall yields, respectively, from d-(+)-glucurono-γ-lactone. Thus, d-glucuronolactone 2 on acetonide protection, DIBAL-H reduction and one-pot intermolecular reductive amination followed by -NCbz protection afforded 6-(N-benzyl-N-benzyloxycarbonyl) amino-6-deoxy-1,2-O-isopropylidene-α-d-gluco-1,4-furanose 5a. 1,2-Acetonide hydrolysis in 5a and Pd-mediated intramolecular reductive aminocyclization afforded tetrahydroxyazepane 1c. An analogous pathway with 5-deoxy-1,2-O-isopropylidene-α-d-glucurono-6,3-lactone 3b gave trihydroxy-azepane 1d. Glycosidase inhibitory activity of 1c/1d was studied and 1d was found to be potent inhibitor of α-mannosidase and β-galactosidase.

Full text of DOI:10.1016/j.tet.2010.08.060

Tetrahedron 66 (2010) 8522e8526
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Concise and practical route to tri- and tetra-hydroxy seven-membered
iminocyclitols as glycosidase inhibitors from
D
-(þ)-glucurono-
g-lactone
Navnath B. Kalamkar a, Vijay M. Kasture a, Sanjay T. Chavan b, Sushma G. Sabharwal b, Dilip D. Dhavale a
,
*
a Department of Chemistry, Garware Research Centre, University of Pune, Pune 411 007, India
b Division of Biochemistry, Department of Chemistry, University of Pune, Pune 411 007, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 30 June 2010
Received in revised form 25 August 2010
Accepted 25 August 2010
Available online 24 September 2010
An efficient and short total synthesis of tetrahydroxy-1c and trihydroxy-azepane 1d is reported in 72%
and 57% overall yields, respectively, from -lactone. Thus, -glucuronolactone 2 on
-(þ)-glucurono-
acetonide protection, DIBAL-H reduction and one-pot intermolecular reductive amination followed by
eNCbz protection afforded 6-(N-benzyl-N-benzyloxycarbonyl) amino-6-deoxy-1,2-O-isopropylidene-
-gluco-1,4-furanose 5a. 1,2-Acetonide hydrolysis in 5a and Pd-mediated intramolecular reductive ami-
nocyclization afforded tetrahydroxyazepane 1c. An analogous pathway with 5-deoxy-1,2-O-iso-
propylidene- -glucurono-6,3-lactone 3b gave trihydroxy-azepane 1d. Glycosidase inhibitory activity of
1c/1d was studied and 1d was found to be potent inhibitor of -mannosidase and -galactosidase.
Ó 2010 Elsevier Ltd. All rights reserved.
D
g
D
a-
D
Keywords:
Iminocyclitols
Glucuronolactone
Reductive amination
Glycosidase inhibitors
a-D
a
b
1. Introduction
required to mimic the putative oxo-carbenium ion like TS with
minimum energetic demand, thus favoring binding to the enzyme
active site in the glycosidase process.9 As a result, polyhydroxylated
azepanes were found to be potent glycosidase inhibitors and in some
cases proven to be more active than their lower ring analogues. For
Iminosugars are known for their potential therapeutic applica-
tions in the treatment of cancer,1 diabetes,2 Gaucher’s disease,3 and
the viral infections including HIV4 due to their glycosidase inhibitory
activity. Amongst monocyclic iminosugars5 the seven-membered
iminocyclitols, commonly known as azaseptanoses or polyhydroxy
azepanes,6 also demonstrate potent glycosidase7 and glycosyl-
transferase inhibitory activity.8 Due to flexibility of seven-membered
ring (compared with five and six-membered-ring) polyhydroxylated
azepanes 1 (Fig. 1) adopt different pseudo-half-chair conformations,
example, tetrahydroxy azepane 1a is a better inhibitor of
tylglucosaminidase than 1-deoxy-N-acetylnojirimycin and 1b is
exhibiting higher -mannosidase and -galactosidase inhibitory
b-N-ace-
a
b
activity than its six-membered ring analogues 1-deoxymanno-
jirimycin and 1-deoxygalactonojirimycin, respectively.10 In addition
the high water solubility and flexibility of iminocycloheptitols allow
the hydroxyl groups to adopt a variety of positions increasing the
probability of them forming hydrogen bonds with the purine and
pyrimidine bases, hence that make them potentially useful as DNA
minor groove binding ligands (MGBL’s).11
H
H
N
H
N
7 N
1
6
OH
OH
OH
OH
HO
HO
HO
5
HO
HO
A number of syntheses for trihydroxy-12,14a and tetrahydroxy-
azepanes13,14b,c along with their hydroxymethyl/acetamido analo-
gues15 are known in the literature. In general, chiron approaches to
iminocycloheptitols make use of starting materials, such as chiro-
3 OH
HO
OH
1b
1c
1a
H
N
H
H
N
N
6
1
inositols,
L-serine, D-mannitol, trans-4-hydroxy-L-proline, D-glucose,
5
OH
HO
HO
OH
OH
2
4
and -quinic acid. etc., whereas, in asymmetric approaches Prinz-
D
3 OH
1d
OH
HO
1f
HO
bach et al. illustrated a cyclooctatetraene route and Mehta and
Lakshminath reported a norbornyl route toward the synthesis of
novelpolyhydroxylatedazepanes.15h,i Achemo-enzymatic approach
to various polyhydroxy azepanes has been reported independently
by Wong and Wang groups.10,13d
1e
Fig. 1. Azepane iminocyclitols.
As a part of our ongoing efforts in syntheses and investigation of
* Corresponding author. Tel.: þ91 2025691727; fax: þ91 2025691728; e-mail
biological activity of polyhydroxy azepanes and azocanes,14 we
address: ddd@chem.unipune.ac.in (D.D. Dhavale).
0040-4020/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.08.060

N.B. Kalamkar et al. / Tetrahedron 66 (2010) 8522e8526
8523
thought of exploiting
oxidation of amylose and commercially cheap as compared to
diacetone
-glucose)16 as a substrate in the synthesis of iminocy-
D
-glucurono lactone 2 (easily available by
protected C-6 amino compound 5a. (88% yield in two steps
after column chromatography). Finally, hydrolysis of 1,2-aceto-
nide functionality in 5a using TFA/water (3:2) at 25 ꢁC fur-
nished C-1 anomeric mixture 6a that was directly subjected to
intramolecular reductive aminocyclization using 10% Pd(OH)2/C
in aq methanol at 90 psi to afford tetrahydroxy azepane 1c (86%
in two steps) as a yellowish sticky solid. This one-pot three-step
process involves hydrogenolysis of N-benzyl and N-Cbz func-
tionalities, in situ formation of seven-membered cyclic-imine
and concomitant reduction under hydrogenation conditions to
give tetrahydroxy azepane 1c. The specific rotation and spectral
data of 1c were found to be in agreement with that reported;
D
clitols 1c and 1d. The only one example reported, by Dax et al. using
glucuronolactone derivative in the synthesis of tetrahydroxy aze-
pane 1c via the key step SN2 displacement by an azide nucleophile,
on
5-chloro-5-deoxy-1,2-O-isopropylidene-b-L
-ido-furanose13h
leading to the mixture of regio-isomeric products with low yields
of target molecules. Here we report the short, high yielding and
stereospecific synthesis, of
D
-gluco-configured tetrahydroxy-1c and
-glucurono-
D-xylo-configured trihydroxy-azepanes 1d from
D
g-
lactone, and evaluation of their glycosidase inhibitory activity.
25
20
[
a
]
ꢀ24.2 (c 0.85, H2O) [lit.13h
[
a
]
ꢀ23.0 (c 0.85, H2O).
D
D
Treatment of 1c with methanol-HCl afforded hydrochloride salt
1c$HCl (98%) whose spectral and analytical data was also found
to be in consonance with that reported.13h
2. Result and discussion
As shown in Scheme 1,
D
-(þ)-glucurono-6,3-lactone 2 was
While targeting the synthesis of trihydroxy-azepane 1d, we
were in need of 5-deoxy-1,2-O-isopropylidene-glucuronolactone.
Although different methods are known for the deoxygenation of 3a
to 3b,18 we adopted one-step process reported by Rauter et al.18a
Thus lactone 3a was reacted with triphenylphosphine, imidazole,
and iodine at 60 ꢁC for 3.5 h to give 5-deoxy-1,2-O-isopropylidene-
treated with acetone and concentrated H2SO4 to get the l,2-O-iso-
propylidene-
Reaction of
a-D
-glucofuranurono-6,3-lactone 3a in 95% yield.17
g
-lactone 3a with DIBAL-H in dichloromethane
at ꢀ78 ꢁC afforded lactol 4a that was directly (without purifi-
cation) subjected to the intermolecular reductive amination
with benzyl amine, acetic acid (cat.) and NaBH3CN in methanol.
The amine thus generated was treated, in the same pot, with aq
sodium bicarbonate and benzyl chloroformate to give N-Cbz
D-glucurono-6,3-lactone 3b as a crystalline solid in 76% yield.
Reaction of lactone 3b with DIBAL-H in anhydrous CH2Cl2 at ꢀ78 ꢁC
afforded lactol 4b, as an anomeric mixture, that on reductive ami-
nation using benzyl amine and NaBH3CN in cat acetic acid afforded
amine, which was (in same pot) treated with benzyl chloroformate
and aq NaHCO3 to get eNCbz protected aminol 5b in 93% yield in
two steps after column chromatography. The eNCbz protected
aminol 5b on treatment with 60% aq TFA and hydrogenation using
10% Pd(OH)2/C in methanol/H2O (9:1) afforded trihydroxy-azepane
1d in 85% yield in two steps. The spectral data were found to be in
agreement that with reported by us and ‘that with its enatio-
mer’.12b,14a The hydrochloride salt of 1d is not known, therefore we
treated 1d with methanol/HCl that afforded hydrochloride salt
1d$HCl in 98% yield whose spectral and analytical data were found
to be in agreement with the structure.
O
O
H
O
O
HO
O
O
H2SO4
OH
R
Acetone, 95%
O
OH
O
2
Ph3P, I2,
3a R = OH
Imidazole
3b R = H, 76%
DIBAL-H
CH2Cl2
2.1. Biological evaluation
Cbz
NBn
OH
6
BnNH2 /H
Iminocyclitols 1c and 1d thus obtained as free bases were tested
for their inhibitory activity against various glycosidases namely
NaCNBH3
MeOH
H
O
R
OH
a
-galactosidase,
N-acetyl- -glucosaminidase (all isolated from almond seeds),
-galactosidase (from Geobacillus toebii BK1), and -glucosidase
(from Baker’s yeast-Sigma Chemical Co.). Thus, tetrahydroxy
azepane 1c showed a strong inhibitoin against -galactosidase
(Ki¼5
M) isolated from the green coffee beans.10 Inhibition against
b-galactosidase, b-glucosidase, a-mannosidase,
5
4
O
O
1
b
R
then
a
a
O
2
O
O
3
aq NaHCO3
CbzCl
O
a
m
5a R = OH 88% (2 steps) 4a R = OH
b
-glucosidase (inhibition¼9%) isolated from almond seeds and
a-
4b R = H
glucosidase (inhibition¼21%) from bakers yeast was insignificant10
while, no significant inhibition was observed for 1c against the
other enzymes studied. Trihydroxy-azepane 1d was found to be
5b R = H 92% (2 steps)
TFA/H2O
a
potent competitive inhibitor of a-mannosidase and b-
Cbz
NBn
H
Table 1
N
1
6
Glycosidase inhibition study of 1d (as free base)a,b
H
R
H2, Pd(OH)2
5
OH
R
Enzyme
IC50
Ki
OH
O
a-Galactosidase
b-Galactosidase
a-Glucosidase
b-Glucosidase
a-Mannosidase
NI
147
NI
142
775
NI
NI
OH
aq. MeOH
161
NI
485
100
NI
OH
HO
OH
6a R = OH
6b R = H
1c R = OH, 86%
1d R = H, 85%
N-Acetyl-
b-glucosaminidase
MeOH
HCl
a
-Galactosidase
NI
NI
1c.HCl R = OH, 98%
1d.HCl R = H, 99%
(G. toebii BK1)
a
IC50 and Ki Values are in mM.
NI¼No inhibition at 1 mM concentration of Inhibitor.
b
Scheme 1. Synthesis of 1c and 1d.

8524
N.B. Kalamkar et al. / Tetrahedron 66 (2010) 8522e8526
galactosidase with Ki values of 100 and 161
1). Compound 1d also showed moderate inhibition against
m
M, respectively (Table
-glu-
M) and was noticed to be
-glucosidase than its enantiomer 1e
m
M)12b and its C2 epimer 1f12c (Fig. 1).
filtered through Celite and residue washed with acetone
b
(200 mLꢂ3) the combine filtrate was concentrated, dissolved in
chloroform (500 mL), and washed with water (100 mL). Organic
layer was dried on sodium sulfate and concentrated under vacuum,
the residue was recrystallised (CHCl3/n-hexane) to give 2 (23.54 g)
cosidase (Ki¼485
m
M and IC50¼142
m
a
better inhibitor of
b
(IC50¼250
as white solid, mp 119e121 ꢁC [lit.17 119e120 ꢁC]; [ 25 52.0 (c 1.95,
a]
D
20
3. Conclusions
CHCl3) [lit.17
[
a
]
52.5 (c 1.95, CHCl3)].
D
In summary, we have developed a new, short, and straight-
forward total synthesis of tetrahydroxy-1c and trihydroxy-aze-
4.1.2. 1,2-O-Isopropylidene-6-(N-benzyl,N-benzyloxycarbonyl)
amino-6-deoxy- -gluco-1,4-furanose (5a). To a cooled solution of
a-D
panes 1d starting from readily available and cheap
D
-
3a (2 g, 9.25 mmol) in dry CH2Cl2 (100 mL) at ꢀ78 ꢁC was added
1 M solution of DIBAL-H in toluene (10.12 mL, 10.18 mmol). After
stirring for 0.5 h at ꢀ78 ꢁC, reaction mixture was quenched by aq
ammonium chloride (20 mL) and stirred for 2 h at 0 ꢁC. The so-
lution was filtered through Celite, and residue was washed with
dichloromethane (20 mLꢂ4). Evaporation of solvent under re-
duced pressure afforded lactol 4a (1.93 g, 96% crude yield) as
a sticky solid. To the solution of crude lactol 4a (1.71 g) at ꢀ20ꢁC in
dry methanol (15 mL) was added an ice cold solution of benzyl
amine (0.94 mL, 8.62 mmol) and glacial acetic acid (0.07 mL
1.17 mmol) in dry methanol (2 mL) over a period of 10 min and
solution was stirred at ꢀ20 ꢁC for 1 h. Sodium cyanoborohydride
(1.21 g, 19.61 mmol) was added in three portions (20 min) at
ꢀ20 ꢁC, and the solution was warmed to 0 ꢁC and stirred for 2 h.
To the above ice cold solution was added aq NaHCO3 (3.29 g,
39.15 mmol in 10 mL water) followed by addition of 50% solution
of benzyl chloroformate in toluene (3.95 mL 23.5 mmol). The re-
action mixture was allowed to attain room temperature and stir-
red for 3 h. Methanol was evaporated under reduced pressure and
the residue was extracted with chloroform (25 mLꢂ3). The com-
bined organic layer was dried (Na2SO4) and concentrated. Purifi-
cation by column chromatography using n-hexane/ethyl
acetate¼7/3 gave 5a (3.19 g, 88% over two steps) as a colorless
(þ)-glucurono- -lactone in five and six steps in overall 72% and
g
57% yields, respectively. The practicability of our method lies with
the fact that: (a) apart from protection and de-protection steps
(three) the other two steps involve routine reactions such as
DIBAL-H reduction, reductive amination and hydrogenation (b)
column chromatography was applied at only two stages-one for
the purification of N-Cbz aminol compounds 5a/5b and other for
the purification of iminocyclitols 1c/1d thus making the synthetic
route workable on multigram scale. From the literature values of
other iminosugars,12b,c it is better to say that trihydroxy-azepane
1d showed moderate to weak inhibitory properties against
a-
mannosidase, -galactosidase and -glucosidase. The methodol-
b
b
ogy could be further extended in the syntheses of different other
iminosugars and polyhydroxylated azepanes, using other readily
available sugar
progress.
g
-lactones,19 and work in this direction is in
4. Experimental
4.1. General methods
Melting points were recorded with Thomas Hoover Capillary
melting point apparatus and are uncorrected. IR spectra were
recorded with Shimadzu FTIR-8400 as a thin film or in Nujol mull
or using KBr pellets and are expressed in cmꢀ1. 1H (300 MHz) and
13C (75 MHz) NMR spectra were recorded with Varian Mercury
instrument using CDCl3, D2O or CD3OD as a solvent. Elemental
analyses were carried out with Thermo-Electron Corporation
CHNS analyzer Flash-EA 1112 at Department of Chemistry, Uni-
versity of Pune, Pune. Optical rotations were measured using
Bellingham Stanley-ADP 220 digital polarimeter with sodium light
(589.3 nm) at 25 ꢁC. Thin layer chromatography was performed on
pre-coated plates (0.25 mm, silica gel 60 F254). Visualization was
made by absorption of UV light or by thermal development after
spraying with 3.5% solution of 2,4-dinitrophenylhydrazine in
ethanol/H2SO4 and with basic aqueous potassium permanganate
solution. Column chromatography was carried out with silica gel
(100e200 mesh). Unless not mention the reactions were carried
out in oven-dried glasswares under dry N2. Acetone, dichloro-
methane, toluene, and methanol were purified and dried before
use. Distilled n-hexane, ethyl acetate, CH2Cl2, and methanol were
used for column chromatography. After decomposition of the re-
action with water, the work-up involves washing of combined
organic layer with water, brine, drying over anhydrous sodium
sulfate, and evaporation of solvent at reduced pressure using ro-
tary evaporator.
sticky solid. Found: C, 65.15; H, 6.70. C24H29NO7 requires: C, 65.00;
25
H, 6.59; Rf 0.40 (n-hexane/ethyl acetate¼1/1); [
a
]
D
ꢀ1.2 (c 4.68,
CHCl3); IR (CH2Cl2) 3429 (broad), 1678, 1244, 1076 cmꢀ1
;
1H NMR
300 MHz (CDCl3þD2O)
d
1.25 (3H, s, CH3), 1.42 (3H, s, CH3),
3.41e3.60 (2H, br s, NeCH2Ph), 3.97 (1H, dd, J¼5.7 and 1.5 Hz, H-
4), 4.00e4.10 (1H, m, H-5), 4.32 (1H, br s, H-3), 4.46 (1H, d,
J¼3.5Hz, H-2), 4.54 (1H, br s, 6-H), 4.62e4.70 (1H, m, 6-H), 5.16
(2H, s, O-CH2Ph) 5.94 (1H, d, J¼3.5Hz, H-1), 7.02e7.42 (10H, m,
AreH); 13C NMR (75 MHz, CDCl3)
d 26.1 (CH3), 26.8 (CH3), 51.7 (C-
6), 52.1 (NeCH2Ph), 68.0 (O-CH2Ph) 70.4 (C-5), 75.1, 80.6, 85.1 (C-2,
C-3, C-4), 105.1 (C-1), 111.6 (isopropylidene), 127.4, 127.5, 127.9,
128.2, 128.5, 128.6, 130.9, 140.0 (Ar), 159.0 (NCOO).20
4.1.3. 1,6-Dideoxy-1,6-imino- -glucitol (1c). A solution of 5a (0.43 g,
D
2.63 mmol) in TFA/H2O (3:2, 8 mL) was stirred at 0 ꢁC for 30 min
and at 25 ꢁC for 4 h. Solvent was co-evaporated with toluene at
rotary evaporator using high vacuum to furnish sticky solid. A
solution of the above product and 10% Pd(OH)2/C (0.06 g) in aq
methanol (5 mL, 9:1) was hydrogenated at 90 psi for 48 h at 25 ꢁC.
The catalyst was filtered through Celite and solvent was evaporated
to afford thick liquid. Purification by column chromatography
(CH2Cl2/MeOH/25% NH4OH¼2/2/0.2) yielded 1c (136 mg, 86%) as
a semi solid: Rf 0.4 (CH2Cl2/MeOH/25% NH4OH¼2/7/1); [
a]
25 ꢀ24.2
D
(c 0.85, H2O) [lit.13h
[
a
]
20 ꢀ23.0 (c 0.85, H2O).
D
4.1.1. 1,2-O-Isopropylidene-
was prepared by the slightly modified procedure of Klemer et al.17
To stirred suspension of -glucurono- -lactone (20.0 g,
0.17 mmol) in dry acetone (500 mL) concentrated sulfuric acid
(10 mL) was added drop wise over the period of 20 min at room
temperature, the reaction mixture was then vigorously stirred for
further 4 h. The resulting clear yellow solution was neutralized with
slow of addition of solid sodium carbonate (27 g). Solution was
a
-
D
-glucofuranurono-6,3-lactone (2). It
4.1.4. 1,6-Dideoxy-1,6-imino-D-glucitol, hydrochloride salt (1c$HCl).
To an ice cold solution of 1c (15 mg, 0.092 mmol) in methanol
(1 mL) was added concentrated HCl (0.1 mL) and the reaction
mixture was stirred at 25 ꢁC for 12 h. The solvent was evaporated to
dryness and the residue was dissolved in distilled water (1 mL) and
extracted with chloroform (1 mLꢂ3). The aqueous layer was con-
centrated to afford hydrochloride salt of 1c (17 mg, 98%) as
a gummy solid. Found: C, 36.40; H, 7.35. C6H14ClNO4 requires: C,
a
a
-D
g

N.B. Kalamkar et al. / Tetrahedron 66 (2010) 8522e8526
8525
25
36.10; H, 7.07; Rf 0.3 (CH2Cl2/MeOH/25% NH4OH¼2/7/1); [
a
]
buffer (pH 9.8) and absorbance of the liberated p-nitrophenol was
measured at 405 nm with a UVevisible Spectrophotometer. Con-
trols were run simultaneously in the absence of test compound.
One unit of glycosidase activity is defined as the amount of enzyme
D
ꢀ12.6 (c 1.3, MeOH) [lit.13f
[a
]
26 ꢀ15.0 (c 1, H2O)].
D
4.1.5. 5,6-Dideoxy-6-(N-benzyl,N-benzyloxycarbonyl)amino-1,2-O-
isopropylidene- -gluco-1,4-furanose (5b). Reaction of 3b (1.7 g,
a-
D
that hydrolyzed 1 m
mol of p-nitrophenol per minute at 37 ꢁC. The
8.5 mmol) in dry CH2Cl2 (90 mL) with 1 M solution of DIBAL-H in
toluene (9.33 mL, 9.35 mmol) as stated for 4a furnished lactol 4b
(1.66 g, 97% crude yield) as a sticky solid. Reaction of 4b (1.2 g
5.94 mmol) with benzyl amine (0.71 mL, 6.53 mmol), sodium cya-
noborohydride (0.92 g, 14.8 mmol) and glacial acetic acid (0.05 mL
0.9 mmol) in dry methanol (2 mL) followed by reaction with benzyl
chloroformate in toluene (2.98 mL 17.81 mmol) and aq NaHCO3
(2.5 g, 29.7 mmol, 8 mL water) as described for 5a and column
chromatography using n-hexane/ethyl acetate¼4/1 yielded 5b
(2.43 g, 92% in two steps) as a colorless thick liquid. Found: C, 67.21;
inhibition constants (Ki) and the nature of the inhibition were de-
termined from LineweavereBurk plots.
Acknowledgements
We are grateful to Prof. M.S. Wadia for helpful discussions. We
are thankful to the University of Pune for financial support (BCUD/
OSD/184-2009). N.B.K. and V.M.K. are thankful to the CSIR, New
Delhi, for Senior Research Fellowships.
H, 7.12. C24H29NO6 requires:C, 67.43; H, 6.84; Rf 0.56 (n-hexane/ethyl
Supplementary data
25
acetate¼1/1); [
a]
ꢀ2.3 (c 2.54, CHCl3); IR (CH2Cl2) 3443 (broad),
D
1693,1220,1076 cmꢀ1; 1H NMR (300 MHz, CDCl3)
d 1.29 (3H, s, CH3),
Copies of 1H and 13C NMR spectra of 5a, 5b, 1c, 1c$HCl, 1d,
1d$HCl and LineweavereBurk plots of 1d against glycosidase.
Supplementary data associated with this article can be found in
online version at doi:10.1016/j.tet.2010.08.060. These data include
MOL files and InChIKeys of the most important compounds de-
scribed in this article.
1.45 (3H, s, CH3), 1.54e2.0 (2H, m, H-5), 3.10e3.40 (2H, m, H-6),
3.80e4.20 (3H, m, H-3, H-4, OH), 4.38e4.6 (3H, m, NeCH2Ph, H-2),
5.20 (2H, s, O-CH2Ph), 5.82 (1H, d, J¼3.57, 1-H), 7.10e7.40 (10H, m,
AreH); 13C NMR (75 MHz, CDCl3)
d 26.0 (CH3), 26.5 (CH3), 43.5 (C-5),
44.0 (C-6) 50.7 (NeCH2Ph), 67.3 (O-CH2Ph) 74.9 (C-4), 78.0 (C-3),
85.1 (C-2), 104.2 (C-1), 111.1 (isopropylidene), 127.3, 127.7, 127.9,
128.3, 128.4, 136.2, 137.3 (Ar), 156.4 (NCOO).21
References and notes
4.1.6. 1,5,6-Trideoxy-1,6-imino- -xylo-hexitol (1d). Reaction of 5b
D
1. (a) Woynaroska, B.; Wilkiel, H.; Sharma, M.; Carpenter, N.; Fleet, G. W. J.; Ber-
nacki, R. J. Anticancer Res. 1992, 12, 161; (b) Gross, P. E.; Baker, M. A.; Carver, J. P.;
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5. (a) Stutz, A. E. Iminosugars as Glycosidase Inhibitors: Nojirimycin and Beyond, 1st
ed.; Wiley: Weinheim, Germany, 1999; (b) Iminosugars: From Synthesis to
Therapeutic Applications; Compain, P., Martin, O. R., Eds.; John Wiley: Chi-
chester, UK, 2007; (c) Paulsen, H. Angew. Chem., Int. Ed. Engl. 1966, 5, 495; (d)
Look, G. C.; Fotsch, C. H.; Wong, C.-H. Acc. Chem. Res. 1993, 26, 182; (e) Ganem, B.
Acc. Chem. Res. 1996, 29, 340; (f) de Melo, E. B.; Gomes, A. d. S.; Carvalho, I.
Tetrahedron 2006, 62, 10277; (g) Pandey, G.; Dumbre, S. G.; Khan, M. I.; Shabab,
M. J. Org. Chem. 2006, 71, 8481; (h) Davis, B. G. Tetrahedron: Asymmetry 2009,
20, 652.
(0.61 g, 1.42 mmol) with TFA/H2O (3:2, 12 mL) followed by hydro-
genation with 10% Pd(OH)2/C (0.08 g) in aq methanol (10 mL, 9:1)
as described for 1c and column chromatography purification using
CH2Cl2/MeOH/25% NH4OH 3/2/0.2 afforded 1d (178 mg, 85%) as
a sticky solid: Rf 0.4 (CH2Cl2/MeOH/25% NH4OH¼3/6/1); [
a]
25 18.1
D
(c 0.95, MeOH) [lit.14a 26 16.36 (c 0.33, MeOH)].
[a]
D
4.1.7. 1,5,6-Trideoxy-1,6-imino-D-xylo-hexitol, hydrochloride salt
(1d$HCl). Compound 1d (40 mg, 0.27 mmol) in methanol (3 mL)
was reacted with concentrated HCl (0.3 mL) as described for 1c$HCl
to afford hydrochloride salt 1d$HCl (49 mg, 99%) as a yellow
gummy solid. Found: C, 39.53; H, 7.91. C6H14ClNO3 requires C,
22
39.24; H, 7.68; Rf 0.3 (CH2Cl2/MeOH/25% NH4OH¼2/6/1); [
a
]
D
4.0
(c 2.4, H2O). IR (KBr) 3331e2833 (broad), 1579, 1053 cmꢀ1; 1H NMR
(300 MHz, D2O) 2.12e2.25 (2H, m, H-5), 3.16e3.30 (1H, m, H-6),
d
3.32e3.58 (3H, m, H-1/H-6), 3.68 (1H, dd, J¼7.2 and 5.2 Hz, H-3),
6. Paulsen, H.; Todt, K. Chem. Ber. 1967, 100, 512.
7. (a) Simmott, M. L. Chem. Rev. 1990, 90, 1171; (b) Winchester, B.; Fleet, G. W. J. Gly-
cobiology 1992, 2, 199; (c) Bols, M. Acc. Chem. Res.1998, 31, 1; (d) Heightman, T. D.;
Vasella, A. T. Angew. Chem., Int. Ed. 1999, 38, 750; (e) Zechel, D. L.; Withers, S. G.
Acc. Chem. Res. 2000, 33,11;(f)Lillelund,V. H.;Jensen,H.H.;Liang,X.;Bols, M.Chem.
Rev. 2002, 102, 515; (g) Asano, N. Curr. Top. Med. Chem. 2003, 3, 471.
3.84 (1H, dt, J¼7.2 and 3.6 Hz, H-4), 4.10 (1H, dt, J¼5.2 and 2.3 Hz, H-
2); 13C NMR (75 MHz, D2O)
(C-4), 72.5 (C-2), 78.4 (C-3).
d 27.6 (C-5), 42.2 (C-6), 45.3 (C-1) 68.2
8. (a) Kim, Y. J.; Ichikawa, M.; Ichikawa, Y. J. Am. Chem. Soc.1999,121, 5829; (b) Sears,
P.; Wong, C.-H. Angew. Chem., Int. Ed.1999, 38, 2301; (c) Saotome, C.; Wong, C.-H.;
Kanie, O. Chem. Biol. 2001, 8, 1061; (d) Pandey, G.; Kapur, M. Org. Lett. 2002, 4,
3883; (e) Compain, P.; Martin, O. R. Curr. Top. Med. Chem. 2003, 3, 541.
9. Qian, X.-H.; Moris-Varas, F.; Wong, C.-H. Bioorg. Med. Chem. Lett. 1996, 6, 1117.
10. Our results are well in agreement with that reported see: Moris-Varas, F.; Qian,
X.-H.; Wong, C.-H. J. Am. Chem. Soc. 1996, 118, 7647.
11. Johnson, H. A.; Thomas, N. R. Bioorg. Med. Chem. Lett. 2002, 12, 237.
12. For trihydroxy azepane 1d and stereoisomers see: (a) Shih, T.-L.; Yang, R.-Y.; Li,
S.-T.; Chiang, C.-F.; Lin, C.-H. J. Org. Chem. 2007, 72, 4258; (b) Moutel, S.; Shipman,
M.; Martin, O. R.; Ikeda, K.; Asano, N. Tetrahedron: Asymmetry 2005, 16, 487; (c)
Andersen, S. M.; Ekhart, C.; Lundt, I.; Stutz, A. E. Carbohydr. Res. 2000, 326, 22; (d)
Gallos, J. K.; Demeroudi, S. C.; Stathopoulou, C. C.; Dellios, C. C. Tetrahedron Lett.
2001, 42, 7497;(e) See Ref. 6. This paperdoes notdescribe the synthesis of the free
azepane base but the protected version: N-Ac, tri-O-Ac derivative.
13. For tetrahydroxy azepane 1c and stereoisomers see: (a) Ref. 10. (b) Painter, G. F.;
Eldridge, P. J.; Falshaw, A. Bioorg. Med. Chem. 2004, 12, 225; (c) Painter, G. F.;
Falshaw, A.; Wong, H. Org. Biomol. Chem. 2004, 2, 1007; (d) Andreana, P. R.;
Sanders, T.; Janczuk, A.; Warrick, J. I.; Wang, P. G. Tetrahedron Lett. 2002, 43,
6525; (e) Fuentes, J.; Gasch, C.; Olano, D.; Pradera, M. A.; Repetto, G.; Sayago, F.
J. Tetrahedron: Asymmetry 2002, 13, 1743; (f) Joseph, C. C.; Regeling, H.; Zwa-
nenburg, B.; Chittenden, G. J. F. Tetrahedron 2002, 58, 6907; (g) Painter, G. F.;
Falshaw, A. J. Chem. Soc., Perkin Trans. 1 2000, 1157; (h) Dax, R.; Gaigg, B.;
Grassberger, B.; Koelblinger, B.; Stutz, A. E. J. Carbohydr. Chem. 1990, 9, 479; (i)
Fuentes, J.; Gasch, C.; Olano, D.; Pradera, M. A. Tetrahedron Lett. 1999, 40, 4063;
4.2. Procedure for the inhibition assay
The enzymes
mannosidase, and N-acetyl-
from almond seeds; -galactosidase was isolated from G. toebii BK1
and -glucosidase was procured from Sigma Chemical Co. were
a
-galactosidase,
b
-galactosidase,
b-glucosidase, a-
b-D-glucosaminidase were isolated
a
a
used for glycosidase inhibitory activity. Inhibition potencies of 1c
and 1d were determined by measuring the residual hydrolytic
activities of the glycosidases. The substrates p-nitrophenyl-
copyranoside, p-nitrophenyl- -glucopyranoside, p-nitrophenyl-
-galactopyranoside and p-nitrophenyl- -galactopyranoside,
p-nitrophenyl-N-acetyl- -glucopyranoside, and p-nitrophenyl-
-mannopyranoside (all of Sigma Chemicals Co., USA) of 2 mM
b-D-glu-
a-D
a
-D
b-D
b-
D
a-
D
concentration, were prepared in 0.025 M citrate buffer with pH 4.0
and used for assay. The test compound (of various concentrations
from 20
buffered at its optimal pH, for 1 h at 37 ꢁC. The enzyme reaction was
initiated by the addition of 100 L of substrate. Reaction was ter-
minated at the end of 90 min by the addition of 0.05 M borate
mM to 1000 mM) was pre-incubated with the enzyme,
m

8526
N.B. Kalamkar et al. / Tetrahedron 66 (2010) 8522e8526
(j) Gauzy, L.; Merrer, Y. L.; Depezay, J.-C. Tetrahedron Lett. 1999, 40, 6005; (k)
Tzou, D.-L. M.; Subramanian, T.; Lin, C.-C. Bioorg. Med. Chem. 2004, 12, 3259;
(g) Assiego, C.; Pino-Gonzalez, M. S.; Lopez-Herrera, F. J. Tetrahedron Lett.
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Merrer, Y. L.; Poitout, L.; Depezay, J.-C.; Dosbaa, I.; Geoffroy, S.; Foglietti, M.-J.
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16. Cost of
D
-glucuronolactone is 100 g¼e$ 42.0 and that of diacetone
D-glucose is
25 g¼w $ 25.6 see: Aldrich Chemistry, Handbook of Fine Chemicals; Aldrich
Chemical: Milwaukee, WI, 2009e2010; pp 1084 and 1478.
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1037; (b) Matsuura, D.; Takabe, K.; Yoda, H. Tetrahedron Lett. 2006, 47, 1371.
€
14. For synthesis of 1c and 1d from our group see: (a) Dhavale, D. D.; Chaudhari, V.
D.; Tilekar, J. N. Tetrahedron Lett. 2003, 44, 7321; (b) Tilekar, J. N.; Patil, N. T.;
Jadhav, H. S.; Dhavale, D. D. Tetrahedron 2003, 59, 1873; (c) For our recent re-
ports on azepane and other iminosugars see: Jadhav, V. H.; Bande, O. P.; Puranik,
V. G.; Dhavale, D. D. Tetrahedron 2010, 66, 2830; (d) Jadhav, V. H.; Bande, O. P.;
Puranik, V. G.; Dhavale, D. D. Tetrahedron: Asymmetry 2010, 21,163; (e) Kalamkar,
N. B.; Kasture, V. M.; Dhavale, D. D. J. Org. Chem. 2008, 73, 3619; (f) Dhavale, D. D.;
Markad, S. D.; Karanjule, N. S.; Reddy, P. J. J. Org. Chem. 2004, 69, 4760 and ref-
erences cited therein.
19. For other sugar g-lactones see: (a) Csuk, R.; Honig, H.; Nimp, J.; Weidmann, H.
Tetrahedron Lett. 1980, 21, 2135; (b) Martin, A.; Watterson, M. P.; Brown, A. R.;
Imtiaz, F.; Winchester, B. G.; Watkin, D. J.; Fleet, G. W. J. Tetrahedron: Asym-
metry 1999, 10, 355; (c) Weymouth-Wilson, A. C.; Clarkson, R. A.; Jones, N. A.;
Best, D.; Wilson, F. X.; Pino-Gonzalez, M.-S.; Fleet, G. W. J. Tetrahedron Lett.
2009, 50, 6307.
15. For recent literature on hydroxy methyl/actamido analogues of azepanes see:
(a) Estevez, A. M.; Soengas, R. G.; Otero, J. M.; Estevez, J. C.; Nash, R. J.; Es-
tevez, R. J. Tetrahedron: Asymmetry 2010, 21, 21; (b) Marcelo, F.; He, Y.; Yuzwa,
20. The 1H and 13C NMR spectra of 5a and 5b showed additional signals >10% due
to the isomerization by restricted rotation around CeN. see: In Applications of
NMR Spectroscopy in Organic Chemistry; Jackman, L. M., Sternhell, S., Eds.;
Pergamon: Elmsford, NY, 1978; p 361.
ꢀ
S. A.; Nieto, L.; Jimecnez-Barbero, J.; Sollogoub, M.; Vocadlo, D. J.; Davies, G.
ꢀ
D.; Blecriot, Y. J. Am. Chem. Soc. 2009, 131, 5390; (c) Li, H.; Marcelo, F.; Bello, C.;
Vogel, P.; Butters, T. D.; Rauter, A. P.; Zhang, Y.; Sollogoub, M.; Yves, B. Bioorg.
Med. Chem. Lett. 2009, 17, 5598; (d) Li, H.; Zhang, Y.; Vogel, P.; Sinay, P.; Bleriot, Y.
Chem. Commun. 2007, 183; (e) Chang, M.-Y.; Kung, Y.-H.; Ma, C.-C.; Chen, S.-T.
Tetrahedron 2007, 63, 1339; (f) Lin, C.-C.; Pan, Y.-S.; Patkar, L. N.; Lin, H.-M.;
21. The 1H and 13C NMR spectra of 5b showed additional signals >10% due to the
isomerization by restricted rotation around CeN. see: In Applications of NMR
Spectroscopy in Organic Chemistry; Jackman, L. M., Sternhell, S., Eds.; Pergamon:
Elmsford, NY, 1978; p 361.