α-geminal dihydroxymethyl piperidine and pyrrolidine iminosugars: Synthesis, conformational analysis, glycosidase inhibitory activity, and molecular docking studies

Article abstract of DOI:10.1021/jo3009534

The Jocic-Reeve and Corey-Link type reaction of dichloromethyllithium with suitably protected 5-ketohexofuranoses followed by treatment with sodium azide and sodium borohydride reduction gave 5-azido-5-hydroxylmethyl substituted hexofuranoses 7a-c with required geminal dihydroxymethyl group. Removal of protecting groups and converting the C-1 anomeric carbon into free hemiacetal followed by intramolecular reductive aminocyclization with in situ generated C5-amino functionality afforded corresponding 5C-dihydroxymethyl piperidine iminosugars 2a-c. Alternatively, removal of protecting groups in 7b and 7c and chopping of C1-anomeric carbon gave C2-aldehyde that on intramolecular reductive aminocyclization with C5-amino gave 4C-dihydroxymethyl pyrrolidine iminosugars 1b and 1c, respectively. On the basis of the ¹H NMR studies, the conformations of 2a/2b were assigned as ⁴C₁ and that of 2c as ¹C₄. The glycosidase inhibitory activities of all five iminosugars were studied with various glycosidase enzymes and compared with natural D-gluco-1-deoxynojirimycin (DNJ). All the five compounds were found to be potent inhibitors of rice α-glucosidase with K_i and IC ₅₀ values in the nanomolar concentration range. Iminosugars 2b and 1b were found to be more potent inhibitors than their parent iminosugar. These results were substantiated by in silico molecular docking studies.

Full text of DOI:10.1021/jo3009534

Article
pubs.acs.org/joc
α‑Geminal Dihydroxymethyl Piperidine and Pyrrolidine Iminosugars:
Synthesis, Conformational Analysis, Glycosidase Inhibitory Activity,
and Molecular Docking Studies
Nitin J. Pawar,† Vijay Singh Parihar,† Sanjay T. Chavan,‡ Rakesh Joshi,§ Pranaya V. Joshi,∥
Sushma G. Sabharwal,‡ Vedavati G. Puranik,∥ and Dilip D. Dhavale*,†
†Department of Chemistry, Garware Research Centre, University of Pune, Pune, 411 007, India
‡Division of Biochemistry, Department of Chemistry, University of Pune, Pune, 411 007, India
§Biochemical Sciences Division, National Chemical Laboratory, Pune, 411 008, India
∥Centre for Material Characterization, National Chemical Laboratory, Pune, 411 008, India
S
* Supporting Information
ABSTRACT: The Jocic−Reeve and Corey−Link type reaction of dichloromethyllithium with suitably protected 5-keto-
hexofuranoses followed by treatment with sodium azide and sodium borohydride reduction gave 5-azido-5-hydroxylmethyl
substituted hexofuranoses 7a−c with required geminal dihydroxymethyl group. Removal of protecting groups and converting the
C-1 anomeric carbon into free hemiacetal followed by intramolecular reductive aminocyclization with in situ generated C5-amino
functionality afforded corresponding 5C-dihydroxymethyl piperidine iminosugars 2a−c. Alternatively, removal of protecting
groups in 7b and 7c and chopping of C1-anomeric carbon gave C2-aldehyde that on intramolecular reductive aminocyclization
with C5-amino gave 4C-dihydroxymethyl pyrrolidine iminosugars 1b and 1c, respectively. On the basis of the 1H NMR studies,
the conformations of 2a/2b were assigned as 4C1 and that of 2c as 1C4. The glycosidase inhibitory activities of all five iminosugars
were studied with various glycosidase enzymes and compared with natural D-gluco-1-deoxynojirimycin (DNJ). All the five
compounds were found to be potent inhibitors of rice α-glucosidase with Ki and IC50 values in the nanomolar concentration
range. Iminosugars 2b and 1b were found to be more potent inhibitors than their parent iminosugar. These results were
substantiated by in silico molecular docking studies.
In a classical variation in the position of dihydroxymethyl
substituents, Altenbach et al. and Estevez et al. synthesized α-
geminal dihydroxymethyl substituted pyrrolidine iminosugar 1a
(Figure 1) that showed potent α-galactosidase inhibitory
activity,6 while Fleet and co-workers reported seven membered
azepane iminosugars that showed loss in inhibitory activity due
to conformational distortion.7 Although five and seven
membered α-geminal dihydroxymethyl iminosugars are
known, analogous six membered piperidine iminosugars are
not known so far. As a part of our continuing efforts in this
area,8 we are now reporting hitherto unknown α-geminal
dihydroxymethyl substituted pyrrolidine iminosugars 1b, 1c
and piperidine iminosugars 2a, 2b, 2c and study of their
INTRODUCTION
■
A number of piperidine Ia (Figure 1) and pyrrolidine IIa
iminosugars, with variation in the position and orientation of
hydroxyalkyl substitution, are known to be promising and
selective glycosidase inhibitors.1,2 In an attempt to know the
effect of an additional hydroxymethyl group on their biological
activity, the dihydroxyalkyl substituted six/five membered
iminosugars were either isolated or synthesized and evaluated
for glycosidase inhibitory activity.3 For example, naturally
occurring α-D-gluco-homonojirimycin, β-D-manno-homonojiri-
mycin (general structure Ib)3a and 2,5-dideoxy-2,5-imino-D-
mannitol (DMDP) IIb,1 with α,α′-dihydroxymethyl group, are
potent inhibitors of α-glucosidases, α-L-fucosidase and α-
glucosidase, respectively.3b Similarly, α,β- and α,β′-dihydrox-
ymethyl substituted piperidine iminosugars were found to be
more potent and selective inhibitors of different glycosidases.4,5
Received: May 24, 2012
© XXXX American Chemical Society
A
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lithium to the C-5 ketone functionality of D-hexo-5-uloses C
(easily obtained from hexoses) will give an access to suitably
protected α-dichloromethyl carbinol B.10 Our results in this
direction are described herein.
RESULTS AND DISCUSSION
■
Required benzyl-2,3-O-isopropylidene-6-O-benzyl-α-D-manno-
furanoside 3a was prepared from D-mannose as reported
earlier.11 Oxidation of 3a using PCC afforded ketone 4a as a
white solid (Scheme 2) in 93% yield. The condensation of
ketone 4a with dichloromethyllithium gave a diastereomeric
mixture of dichloroalcohols, in the ratio of 9:1, as evident from
the 1H NMR spectrum of crude product. An appreciable
difference in the Rf value allowed us to separate the isomers by
column chromatography to get 5a and its C5-epimer in the 85
Figure 1. Piperidine and pyrrolidine iminosugars.
1
and 9% yield, respectively. The H NMR spectra were unable
glycosidase inhibitory activity. A unique feature of iminosugars
1 and 2 is their dual configurational nature due to the presence
of stereogenic C-4 or C-5 carbon atom, respectively, wherein
diastereotopic hydroxymethyl groups in 1b allow it to be called
as either 4-C-hydroxymethyl-1,4-dideoxy-1,4-imino-D-arabinitol
(C1−C5) or 4-C-hydroxymethyl-1,4-dideoxy-1,4-imino-L-xylitol
(C1−C5′). Similarly, 2b may be recognized as either D-gluco-
deoxynojirimycin (C1−C6) or L-ido-deoxynojirimycin (C1−
C6′).
In general, introduction of the geminal dihydroxyalkyl moiety
at the α-position to the ring nitrogen atom of the piperidine/
pyrrolidine ring skeleton is difficult. Altenbach et al. introduced
hydroxymethyl group using the Birch reduction of methyl N-
Boc-pyrrolecarboxylate followed by treatment with iodomethyl
pivalate and a reduction of the carboxylate group to get racemic
geminal dihydroxymethyl pyrrolidine 1a.6a Estevez et al.
introduced geminal hydroxymethyl groups in one pot by
aldol condensation of protected nitrotetrose with paraformal-
dehyde.6b In our approach, we thought of utilizing a carbon
skeleton of D-hexoses (D-glucose, D-allose, and D-mannose)
wherein the C-6 hydroxymethyl of hexoses is retained in the
target compound, and the second hydroxymethyl group is
introduced by the Jocic−Reeve and Corey−Link type
approach9 with D-hexo-5-uloses.10 As shown in retrosynthetic
analysis (Scheme 1), intramolecular reductive amination of the
to differentiate the C5-diasteriomeres. Fortunately, the major
isomer 5a was isolated as a solid, and the X-ray crystallographic
data (Figure 2) established the absolute configuration as 5S and
confirmed the formation of L-gulo-isomer. The minor isomer
was therefore considered as D-manno isomer, with 5R absolute
configuration. Formation of 5a as a major product could be
explained by considering the preferred conformer of 4a (Figure
3). We believe that the dipole movement in 4a is considerably
minimized by alignment of oxygen atoms in the C-5 ketone and
the furanose ring on the opposite sides, wherein the Re face
attack to the C5-keto group, from the side opposite to the 2,3-
O-isopropylidene group, is preferred over the Si face attack
(hindered because of the acetonide group), leading to the
formation of 5a as a major product.
In the next step, treatment of 5a with sodium azide afforded
α-azido aldehyde 6a via formation of epoxy-chloride
intermediate10 followed by opening of the oxirane ring by
SN2 attack of the azide ion at C-5. Absolute configuration at the
newly generated C-5 center was assigned as 5R on the basis of
the X-ray crystallographic data of the compound obtained in
the subsequent steps. Thus, reduction of the α-azido aldehyde
6a using NaBH4 afforded α-hydroxymethyl azido compound 7a
as a thick liquid that on removal of the 2,3-acetonide group
with TFA−water gave triol 8a as a white solid. The X-ray
crystallographic data of 8a (Figure 4) established the absolute
configuration as 5R, and therefore confirm the formation of D-
manno-isomer 6a with 5R configuration. In the final step,
reductive aminocyclization of 8a using H2, 10% Pd/C in
methanol afforded 5-C-hydroxymethyl-D-manno-1-deoxynojiri-
mycin 2a (C1−C6) in 91% yield as a thick liquid. This one pot
three steps process involves hydrogenolysis of C6- and C1-O-
benzyl groups to get anomeric mixture of hemiacetals,
reduction of azide functionality to primary amine, and
concomitant intramolecular reductive aminocyclization of C5-
amino functionality with C1-aldehyde to give α-geminal
dihydroxymethyl piperidine iminosugar 2a as a single product.
For the synthesis of piperidine iminosugar 2b, the required
3,6-di-O-benzyl-1,2-O-isopropylidene-α-D-xylo-hexofuranose-5-
ulose 4b was prepared from D-glucose as reported earlier.11 The
condensation of ketone 4b with dichloromethyllithium at −78
°C afforded an inseparable diastereomeric mixture of
dichloroalcohols 5b in 89% yield (Scheme 3).12 In the next
step, treatment of 5b with sodium azide gave α-azido aldehydes
6b as an inseparable mixture of diastereomers. Reduction of
aldehydes in 6b using NaBH4 gave hydroxymethyl compounds
7b, which on hydrolysis of 1,2-acetonide group with TFA−
water (to get an anomeric mixture of hemiacetals) followed by
Scheme 1. Retrosynthesis of 1 and 2
C-5 amino functionality (formed in situ from the C-5 azido
group) with the C-2 or C-1 aldehyde in azido derivative A will
lead to the formation of pyrolidine 1 or piperidine 2
immunosugars, respectively. The azido compound A with
required geminal dihydroxymethyl groups at the C-5 of hexoses
will be obtained from the α-dichloromethyl carbinol B by
treatment with NaN3 (to get α-azido aldehyde) followed by
reduction. The nuclophilic addition of the dichloromethyl
B
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Scheme 2. Synthesis of Iminosugar 2a
Figure 4. ORTEP diagram of compound 8a.
hexofuranose-5-ulose 4c.11 The reaction of 4c with dichlor-
omethyllithium in THF at −78 °C also afforded an inseparable
mixture of diastereomers 5c.12
Figure 2. ORTEP diagram of compound 5a.
Treatment of 5c with NaN3 gave azido aldehydes 6c that on
reduction with NaBH4 gave 7c in 77% (over three steps).
Hydrolysis of the 1,2-acetonide functionality in 7c with TFA−
water followed by reductive aminocyclization (H2, 10% Pd/C)
gave 5-C-hydroxymethyl-D-allo-1-deoxynojirimycin 2c (C1−C6)
as a semisolid.
The syntheses of α-geminal dihydroxymethyl pyrrolidine
iminosugars 1b and 1c were achieved from 7b and 7c,
respectively (Scheme 3). Thus, hydrolysis of the 1,2-O-
acetonide functionality in 7b/7c with TFA−water gave
anomeric mixture of hemiacetals that on oxidative cleavage
using sodium metaperiodate in acetone−water (to cleave
anomeric carbon) followed by reductive aminocyclization
using H2, 10% Pd/C in methanol afforded 4-C-hydroxymeth-
Figure 3. Explanation for diastereoselectivity.
intramolecular reductive aminocyclization using H2,10% Pd/C
in methanol at 200 psi afforded 5-C-hydroxymethyl-D-gluco-1-
deoxynojirimycin 2b (C1−C6) as a semisolid. The same
sequence of reactions, as described for 2b, was separately
performed with 3,6-di-O-benzyl-1,2-O-isopropylidene-α-D-ribo-
C
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Scheme 3. Synthesis of Iminosugars 1b, 1c, 2b, 2c
yl-1,4-dideoxy-1,4-imino-D-arabinitol 1b (C1−C5) and 4-C-
hydroxymethyl-1,4-dideoxy-1,4-imino-D-ribitol 1c (C1−C5) in
81 and 75% yield (over three steps), respectively.
Similarly, in 2b the high coupling constant of J1a,2a = 12.0 Hz
and small coupling constant for J1e,2a = 4.0 Hz indicated the 4C1
for 2b, while in 2c the small coupling constant J1a,2e = 4.1 Hz
and J1e,2e = 7.1 Hz suggested that the compound 2c exists in 1C4
conformation (Figure 5). We believe that the conformation 1C4
is stabilized by intramolecular hydrogen bonding between C-2
and C-4 OH, thus resulting into little twist in the conformation
wherein the dihedral angle between H1e, H2e is ∼140°, which is
in agreement with the observed J1e,2e = 7.1 Hz.8j,k
Biological Activity. Glycosidase inhibitory activity of 1b,
1c, 2a, 2b, 2c was studied with reference to the known standard
D-gluco-1-deoxynojiromycin (DNJ) and is summarized in Table
2. All the five compounds were found to be potent inhibitors of
rice α-glucosidase with Ki and IC50 values in the nanomolar
concentration range. The presence of hydroxymethyl group at
C-5 position in 2b resulted in a slight increase in its α-
glucosidase inhibitory activity as compared to DNJ. Iminosu-
gars 2b and 1b moderately inhibited the α-glucosidase from
baker’s yeast. Iminosugar 2c showed moderate inhibition of β-
galactosidase from bovine liver. Although DNJ did not show
any inhibitory activity against β-galactosidase (bovine liver) and
α-galactosidase (Geobacillus sp.), iminosugars 1b, 2a, 2b and 2c
were found to have moderate inhibitory activity against the
microbial α-galactosidase (Geobacillus sp.) under assay con-
ditions. Also, all the tested iminosugars did not show any
significant inhibitory activity against β-galactosidase, β-
glucosidase (from almond seeds), α-mannosidase, N-acetyl-β-
D-glucosaminidase (Jack bean seeds), α-fucosidase and N-
acetyl-β-D-glucosaminidase (bovine kidney). The inhibition
constants (Ki) were determined from Lineweaver−Burk plots
(Supporting Information).
Conformational Assignments of 2a, 2b and 2c. In
4
general, six membered piperidine iminosugars exist in C1 or
1C4 conformation depending on orientation of hydroxyalkyl
substituent in the ring.2v,8a A change in conformation of
iminosugars has profound effect on their binding properties
with glycosidases and thus affects their inhibitory potential.2,7a
As the iminosugars 2 have two hydroxymethyl substituents at
α-position to the ring nitrogen, it is interesting to find their
conformations. Conformations in 2 were determined by
coupling constant values between the H-1 and H-2 protons
(1H NMR in D2O). The coupling constant values were
obtained from decoupling experiments and are listed in Table
1. In 2a, the lower coupling constant of the H-1 and H-2 for
Table 1. Coupling /values of 2a, 2b and 2c
2a
2b
2c
H1a
H1e
2.92 (dd)
2.63 (dd)
2.90 (dd)
J1a,1e = 14.8 Hz
J1a,2e = 3.0 Hz
3.01 (dd)
J1a,1e = 12.0 Hz
J1a,2a =12.0 Hz
2.95 (dd)
J1a,1e = 13.5 Hz
J1a,2e = 4.1 Hz
2.98 (dd)
J1e,1a = 14.8 Hz
J1e,2e = 1.7 Hz
J1e,1a= 12.0 Hz
J1e,2a= 4.0 Hz
J1e,1a = 13.5 Hz
J1e,2e = 7.1 Hz
axial−equatorial protons (3.0 Hz) and diequatorial protons (1.7
Hz) requires equatorial orientation of the H-2. This indicated
that compound 2a exists in 4C1 conformation (Figure 5).
Molecular Docking Studies. Three dimensional (3D)
model of yeast α-glucosidase, rice α-glucosidase and Geobacillus
α-galactosidase were built by comparative modeling using
MODELER 9 V4 crystallographic structure of related protein as
a template.13 Modeled structures were validated by Ramchan-
dra plot analysis.13b Binding pockets of enzymes and docking
simulation were predicted using AutoDock 4.0.13c This employs
the preparation of receptor by adding hydrogens and assigning
Figure 5. Conformations of 2a, 2b and 2c.
D
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a
Table 2. IC50 (μM) and Ki (μM) Values for New Iminosugars and Standard DNJ
DNJ
1b
1c
2a
2b
2c
IC50
(μM)
Ki
(μM)
IC50
(μM)
Ki
(μM)
IC50
(μM)
Ki
(μM)
IC50
(μM)
Ki
(μM)
IC50
(μM)
Ki
(μM)
IC50
(μM)
Ki
(μM)
Enzymes (Source)
α-glucosidase (rice)
0.036
23
0.066
22
0.028
128
NI
0.083
25
5
4
4
3
0.032
97
0.066
20
0.052
NI
0.083
NI
α-glucosidase (baker’s yeast)
β-galactosidase (bovine liver)
NI
NI
NI
NI
NI
NI
NI
NI
22
NI
NI
20
NI
NI
NI
NI
NI
40
25
α-galactosidase (Geobacillus
sp.)
NI
NI
14
40
15
13
19
34
a
NI: No inhibition at 1 mM concentration of inhibitor. Data is average of three sets of assay performed.
Kollman charges. Similarly, the ligands were prepared by
assigning the Gasteiger charges and nonpolar hydrogens.
Docking simulations were done with Lamarckian Genetic
algorithm (LGA). LGA uses a set of 30 structurally known
protein ligand complexes with experimentally determined
binding constants to calibrate empirical free energy function.
Grid box for docking was set around central atom of protein
with dimension of 40 × 40 × 40 Å. Parameters were set to a
LGA calculation of 10 000 runs, whereas energy evaluations
were set to 1 500 000 and 27 000 generations (repetition of
process). The obtained docked poses were then summarized
and analyzed using Autodock Tool.
hydroxyalkyl derivatives of 1 and 2 could be easily obtained to
get the library of iminosugars for biological evaluation. Work in
this direction is in progress.
EXPERIMENTAL SECTION
■
General Methods. Melting points were recorded with Thomas−
Hoover melting point apparatus and are uncorrected. IR spectra were
recorded with a FTIR as a thin film or using KBr pellets and are
expressed in cm−1. 1H NMR (300 MHz/400 MHz) and 13C NMR (75
MHz) spectra were recorded using CDCl3 or D2O as solvent(s).
Chemical shifts were reported in δ unit (parts per million) with
reference to TMS as an internal standard, and J values are given in
Hertz. Elemental analyses were carried out with C, H-analyzer. Optical
rotations were measured using polarimeter at 25 °C. High resolution
mass spectra (HRMS) were obtained in positive ion electrospray
ionization (ESI) mode using TOF (time-of-flight) analyzer. Thin-layer
chromatography was performed on precoated plates (0.25 mm, silica
gel 60 F254). Column chromatography was carried out with silica gel
(100−200 mesh). The reactions were carried out in oven-dried
glassware under dry N2 atmosphere. Methanol, DCM and THF were
purified and dried with the method reported.14 Petroleum ether (PE)
that was used is a distillation fraction between 40 and 60 °C. 10% Pd/
C were purchased from Aldrich or Fluka. After neutralization, workup
involves washing of combined organic layer with water, brine, drying
over anhydrous sodium sulfate, and evaporation of solvent under
reduced pressure.
Ramchandra plot analysis13b of the rice α-glucosidase, yeast
α-glucosidase and Geobacillus α-galactosidase structures showed
that >95% residues are favored and allowed φ, ψ backbone
conformational regions (Supporting Information, Figure 1A−
C). All inhibitor molecules form the weak interactions (van der
Walls interaction and hydrogen bonds) with binding site
(Table 3 and Figure 6) of rice/yeast α-glucosidase and
Geobacillus α-galactosidase and binding energy values of
interactions were summarized in Table 3. Binding poses
(orientations and conformations) and different interactions of
the inhibitor in the binding site of the enzymes were shown in
Figure 6. For further analysis, the hits with best binding scores
were selected. The trend followed by theoretical binding energy
was corroborated with experimentally observed inhibitory
activity values. Compounds 1b, 2b and 2c were found to be
potent inhibitor of rice α-glucosidase with lowest Ki/IC50 and
binding energy values (Table 2 and 3).
Ligands 1b, 2b and 2c form ∼6, 5, and 6 stable hydrogen
bonds, respectively, with the binding site residues of rice α-
glucosidase. Lower binding free energy for ligand 1b, 2a and 2c
suggests the strong binding to the binding site of enzyme. The
higher binding affinity for these ligands is presumably attributed
to the formation of higher number of stable hydrogen bonds
between the reactive group and several amino acids at the
binding site.
Benzyl-2,3-O-isopropylidene-6-O-benzyl-α-D-lyxo-hexofura-
noside-5-ulose (4a). To a suspension of PCC (25.2 g, 120 mmol)
and finely powdered molecular sieves 4 Å (32.0 g) in dry CH2Cl2 (150
mL) was added a solution of 3a (16.0 g, 40 mmol) in dry CH2Cl2 (15
mL). The mixture was stirred at 30 °C for 3 h. The reaction mixture
was quenched using 2-propanol (10 mL), diluted with ether and
filtered through Celite, and the filtrate was evaporated in vacuo. The
residue was purified by column chromatography by eluting with
petroleum ether/EtOAc, (9:1) to give 4a (14.8 g, 93%) as a white
22
solid: Rf 0.42 (petroleum ether/EtOAc, 9:1); mp 57−9 °C; [α]D
=
−5.0 (c 0.69, CH2Cl2); IR (KBr, ν, cm−1) 1730, 1381, 1111, 1089; 1H
NMR (300 MHz, CDCl3) δ 1.25 (s, 3H), 1.33 (s, 3H), 4.33 (s, 2H),
4.48 (d, J = 11.4 Hz, 1H), 4.56−4.70 (m, 4H), 4.72 (d, J = 4.3 Hz,
1H), 5.10 (dd, J = 5.8, 4.3 Hz, 1H), 5.21 (s, 1H), 7.28−7.37 (m, 10H);
13C NMR (75 MHz, CDCl3) δ 24.5, 25.7, 69.3, 73.4, 74.1, 80.8, 84.2,
84.3, 105.5, 113.1, 127.9, 128.0, 128.2, 128.5, 136.8, 137.2, 203.0. Anal.
Calculated for C23H26O6: C, 69.33; H, 6.58. Found: C, 69.49; H, 6.62.
Benzyl-2,3-O-isopropylidene-6-O-benzyl-5-C-dichlorometh-
yl-α-L-gulo-furanoside (5a). To a solution of diisopropylamine
(5.32 mL, 37.68 mmol) in dry THF (80 mL) at 30 °C under nitrogen
atmosphere was added 1.6 molar solution of n-butyllithium in hexane
(23.53 mL, 37.68 mmol). After stirring for 30 min, the solution was
cooled to −78 °C and ketone 4a (5.0 g, 12.56 mmol) in dry CH2Cl2
(20 mL) was added dropwise. The temperature was then allowed to
raise slowly to 20 °C and then stirred at 20 °C for 4 h. Saturated
solution of NH4Cl (10 mL) was added slowly, the mixture was diluted
with EtOAc, and the usual workup followed, chromatographic
purificaion first elution using with (petroleum ether/EtOAc, 98:02)
gave minor isomer (C-5 epimer) (0.54 g, 9%) as thick liquid: Rf 0.56
CONCLUSIONS
■
In conclusion, we have exploited the C-5 keto functionality of
D-gluco-, D-allo- and D-manno- hexoses to introduce hydrox-
ymethyl and amino functionalities required to achieve synthesis
of geminal dihydroxymethyl substituted piperidine 2a, 2b, 2c
and pyrrolidine 1b, 1c iminosugars. These iminosugars
inhibited rice α-glucosidase, yeast α-glucosidase, and the
Geobacillus α-galactosidase, although to different extents,
possibly because of their different specificities and different
sources. The trend observed in docking results is in agreement
with the experimental studies. The present synthetic analogy
could be exploited to different keto hexoses to get a variety of
iminosugars. In addition, N-alkylated (C1−C10 chain) or N-
23
(petroleum ether/EtOAc, 9:1); [α]D = +72.7 (c 0.52, CH2Cl2); IR
E
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(neat, ν, cm−1) 3362−3504, (br), 1635,1085, 871; 1H NMR (300
MHz, CDCl3) δ 1.21 (s, 3H), 1.42 (s, 3H), 3.85 (d, J = 10.6 Hz, 1H),
4.05 (d, J = 10.6 Hz, 1H), 4.36 (d, J = 2.9 Hz, 1H), 4.39 (d, J = 11.2
Hz, 1H), 4.56 (d, J = 5.3 Hz, 1H), 4.57 (ABq, J = 12.0 Hz, 2H), 4.65
(d, J = 11.2 Hz, 1H), 4.94 (dd, J = 5.3, 2.9 Hz, 1H), 5.06 (s, 1H), 5.15
(s, exchangeable with D2O, 1H), 6.10 (s, 1H), 7.19−7.34 (m, 10H);
13C NMR (75 MHz, CDCl3) δ 24.2, 25.7, 69.1, 71.2, 73.9, 75.2, 76.7,
78.3, 81.8, 85.2, 104.0, 112.9, 127.3, 127.6, 128.0, 128.3, 128.5, 136.8,
137.9. Anal. Calculated For C24H28Cl2O6; C,59.63; H, 5.84. Found: C,
59.80; H, 5.94. Further elution with (petroleum ether/EtOAc, 98:04
to 90:10) gave 5a (5.14 g, 85%) as crystalline white solid: Rf 0.50
22
(petroleum ether/EtOAc, 9:1); mp 110−12 °C; [α]D = +74.4 (c
0.19, CH2Cl2); IR (KBr, ν, cm−1) 3427 (st), 1074, 731; 1H NMR (300
MHz, CDCl3) δ 1.32 (s, 3H), 1.50 (s, 3H), 3.88 (ABq, J = 9.9 Hz,
2H), 4.41 (d, J = 3.4 Hz, 1H), 4.45 (d, J = 11.9 Hz, 1H), 4.55 − 4.71
(m, 4H), 4.85 (s, exchangeable with D2O, 1H), 5.10 − 5.20 (m, 2H),
6.17 (s, 1H), 7.22−7.37 (m, 10H); 13C NMR (75 MHz, CDCl3) δ
24.3, 25.8, 69.1, 71.5, 73.7, 75.5, 75.8, 79.3, 81.7, 85.3, 104.3, 113.1,
127.6, 127.7, 128.0, 128.2, 128.3, 128.5, 136.9, 137.8. Anal. Calculated
For C24H28Cl2O6: C, 59.63; H, 5.84. Found: C, 60.00; H, 5.98.
Diastereomeric ratio was evaluated by 1H NMR analysis of crude
reaction mixture, dr: 1:9.
Benzyl-5-deoxy-5-azido-5-C-benzyloxymethyl-2,3-O-isopro-
pylidene-α-D-manno-furano-1,6-dialdose (6a). To a solution of
5a (3.55 g, 7.36 mmol) in dry DMF (15 mL) was added sodium azide
(2.39 g, 36.82 mmol), TBAI (1.35 g, 3.68 mmol), and the mixture was
heated for 4 h at 110 °C. Reaction mixture was extracted with EtOAc
(100 mL × 3) and washed with water (50 mL × 2) and brine. Organic
layer was dried over anhydrous sodium sulfate, and solvent was
evaporated under reduced pressure. Chromatography using petroleum
ether/EtOAc, (95:05) as an eluant to gave 6a (3.15 g, 94%) as thick
22
liquid: Rf 0.50 (petroleum ether/EtOAc, 92:08); [α]D = +64.9 (c
1
0.80 CH2Cl2); IR (neat, ν, cm−1) 2125, 1735 (N3, CHO); H NMR
(300 MHz, CDCl3) δ 1.29 (s, 3H), 1.43 (s, 3H), 3.84 (AB quartet, J =
10.5 Hz, 2H), 4.27 (d, J = 3.3 Hz, 1H), 4.48 (d, J = 12.0 Hz, 1H),
4.59−4.67 (m, 4H), 4.82 (dd, J = 5.7, 3.3 Hz, 1H), 5.16 (s,1H), 7.27−
7.36 (m,10H), 9.72 (s, 1H), 13C NMR (75 MHz, CDCl3) δ 24.1, 25.2,
69.4, 69.8, 70.4, 73.8, 79.0, 80.3, 84.4, 105.4, 113.1, 127.5, 127.9, 128.0,
128.1, 128.5, 136.9, 137.1, 195.6. Anal. Calculated For C24H27N3O6: C,
63.56; H, 6.00; N, 9.27. Found: C, 63.84; H, 6.18; N, 9.01.
Benzyl-5-deoxy-5-azido-5-C-benzyloxymethyl-2,3-O-isopro-
pylidene-α-D-manno-furanoside (7a). To an ice-cooled solution of
6a (2.00 g, 4.41 mmol) in MeOH (10 mL) was added sodium
borohydride (326 mg, 8.83 mmol) in two portions. Reaction mixture
was stirred for 3 h and quenched by adding saturated aq NH4Cl
solution (5 mL). Methanol was evaporated under reduced pressure
and residue extracted with EtOAc (30 mL × 3) and concentrated.
Usual workup and purification by column chromatography (petroleum
ether/ethyl acetate, 9:1) gave 7a (1.88 g, 94%) as a thick liquid: Rf 0.33
(petroleum ether/ethyl acetate, 9:1); [α]D22 = +40.5 (c 1.73, CH2Cl2);
1
IR (neat, ν, cm−1) 3489 (br), 2125 (st),1080, 754; H NMR (300
MHz, CDCl3) δ 1.29 (s, 3H), 1.44 (s, 3H), 2.64 (t, J = 6.7 Hz,
exchangeable with D2O, 1H), 3.78 (ABq, J = 10.0 Hz, 2H), 3.91 (d, J =
6.7 Hz, after D2O exchange appear as, s, 2H), 4.23 (d, J = 2.8 Hz, 1H),
4.46 (d, J = 11.5 Hz, 1H), 4.53−4.66 (m, 4H), 4.77 (dd, J = 5.8, 3.3
Hz, 1H), 5.09 (s, 1H), 7.26−7.35 (m, 10H); 13C NMR (75 MHz,
CDCl3) δ 24.2, 25.6, 63.6, 66.5, 69.2, 70.9, 73.7, 79.5, 79.7, 85.0, 104.8,
112.9, 127.7, 127.8, 127.9, 128.1, 128.5, 137.0, 137.5. Anal. Calculated
For C24H29N3O6: C, 63.28; H, 6.42; N, 9.22. Found: C, 63.22; H, 6.57;
N, 8.95.
Benzyl-5-deoxy-5-azido-5-C-benzyloxymethyl-α-D-manno-
furanoside (8a). A solution of 7a (350 mg, 0.76 mmol) in TFA−
water (4 mL, 3:1) was stirred for 3 h at 0 °C. TFA was coevaporated
with toluene at reduced pressure. Purification by column chromatog-
raphy (petroleum ether/EtOAc, 7:3) gave 8a (296 mg, 92%) as a
white solid: Rf 0.50 (petroleum ether/EtOAc, 1:1); mp 97−99 °C;
22
[α]D = +54.2 (c 0.16, CH2Cl2); IR (KBr, ν, cm−1) 3317 (br), 2125
1
(st), 1038, 1004, 732; H NMR (300 MHz, CDCl3) δ 2.09−3.40 (br,
exchangeable with D2O, 3H), 3.75 (s, 2H), 3.89 (AB quartet, J = 11.9
Hz, 2H), 4.12−4.17 (m, 2H), 4.33 (t, J = 4.6 Hz, 1H), 4.45 (d, J = 11.9
F
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Figure 6. Binding of ligands DNJ, 2a, 2b, 2c, 1b, and 1c with active pocket of rice α-glucosidase, yeast α-glucosidase and Geobacillus α-galactosidase.
Hz, 1H), 4.58 (bs, 2H), 4.67 (d, J = 11.9 Hz, 1H), 5.09 (d, J = 1.9 Hz,
1H, after opening of 2,3-O-isopropylidene H1 becomes d), 7.27−7.39
(m, 10H); 13C NMR (75 MHz, CDCl3) δ 63.6, 66.7, 70.2, 70.3, 71.5,
74.0, 77.0, 79.6, 107.1, 127.8, 127.9, 128.2, 128.5, 128.6, 136.8, 137.5.
Anal. Calculated For C21H25N3O6: C, 60.71; H, 6.07; N, 10.11. Found:
C, 60.45; H, 6.22; N, 9.92.
(3R,4R,5S)-2,2-Bis(hydroxymethyl)piperidine-3,4,5-triol (2b).
Reaction of 7b (300 mg, 0.65 mmol) with TFA−water (4 mL, 3:1)
followed by hydrogenation as discussed for 2a gave 2b (110 mg, 86%)
as semisolid: Rf 0.33 (25% aq NH4OH/MeOH, 1:99); [α]D24 = +10.0
1
(c 1.59, MeOH); IR (KBr, ν, cm−1) 3134−3600 (br); H NMR (400
MHz, D2O) δ 2.63 (dd, J = 12.0, 12.0 Hz, 1H), 2.95 (dd, J = 12.0, 4.0
Hz, 1H), 3.42−3.56 (m, 3H), 3.58 (d, J = 12.0 Hz, 1H), 3.63 (d, J =
12.0 Hz, 1H), 3.68 (d, J = 12.0 Hz, 1H), 3.82 (d, J = 12.0 Hz, 1H); 13C
NMR (75 MHz, D2O) δ 43.5, 57.4, 60.0, 63.1, 70.9, 72.4, 74.5; MS
(ESI) m/z = 194 (MH+); HRMS calculated for C7H15NO5 (MH+)
194.1028, found 194.1029;
(3R,4R)-2,2-Bis(hydroxymethyl)pyrrolidine-3,4-diol (1b). Re-
action of 7b (500 mg, 1.09 mmol) with TFA−water (6 mL, 3:1) as
described for 2b gave crude hemiacetals that were treated with sodium
metaperiodate (415 mg, 1.64 mmol) in acetone−H2O (8 mL, 3:1) at 0
°C to rt for 1 h. Reaction mixture was quenched with ethylene-diol (2
mL), acetone was evaporated under reduced pressure, and reaction
mixture was filtered through Celite, washed with EtOAc, and solvent
was evaporated at reduced pressure to afford a thick liquid: Rf = 0.80
(petroleum ether/EtOAc, 1:1). The above crude product was
dissolved in methanol and hydrogenated with H2-10%Pd/C (50 mg)
at 200 psi at 60 °C for 24 h. The catalyst was filtered through Celite,
washed with methanol, and evaporated to give thick oil. Purification by
(3R,4R,5R)-2,2-Bis(hydroxymethyl)piperidine-3,4,5-triol (2a).
To a solution of 8a (200 mg, 0.48 mmol) in methanol (20 mL) was
added 10% Pd/C (50 mg), and reaction mixture was hydrogenated at
200 psi for 24 h. Reaction mixture was filtered through Celite, washed
with methanol, and solvent was evaporated at reduced pressure.
Purification by column chromatography (chloroform/methanol, 8:2)
gave 2a (85 mg, 91%) as a thick liquid: Rf 0.33 (25% aq NH4OH/
22
MeOH, 1/99); [α]D = −40.4 (c 1.09 MeOH); IR (neat, ν, cm−1)
3593−3300 (br); 1H NMR (300 MHz, D2O) δ 2.92 (dd, J = 14.8, 3.0
Hz, 1H), 3.01 (dd, J = 14.8, 1.7 Hz, 1H), 3.61 (d, J = 11.5 Hz, 1H),
3.66 (d, J = 12.4 Hz, 1H), 3.77−3.86 (m, 3H),[irradiation of signal at
4.03 gives 3.81 (d, J = 11.5 Hz, 1H), 3.82 (d, J = 12.4 Hz, 1H), 3.83 (d,
J = 9.8 Hz, 1H)], 3.93 (d, J = 9.8 Hz, 1H), 4.01−4.05 (narrow m, 1H);
13C NMR (75 MHz, D2O) δ 46.2, 60.0, 63.4, 64.7, 71.0, 71.2, 73.0; MS
(ESI) m/z = 194 (MH+); HRMS calculated for C7H15NO5 (MH+)
194.1028, found 194.1029.
G
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column chromatography (chloroform/methanol, 8:2) gave 1b (145
mg, 81% over three steps) as a thick oil: Rf 0.36 (25% aq NH4OH/
128.6, 136.2, 137.1, 196.2. Anal. Calculated For C24H27N3O6: C, 63.56;
H, 6.00; N, 9.27. Found: C, 63.58; H, 6.36; N, 8.95.
Synthesis of Azido Alcohols (7b). Reaction of 6b (2.03 g, 4.48
24
MeOH, 1:99); [α]D = +7.3 (c 0.81, MeOH); IR (neat, ν, cm−1)
1
3441−3450 (b); H NMR (300 MHz, D2O) δ 2.95 (dd, J = 12.0, 5.8
mmol) as described for 7a gave azido alcohols 7b (1.90 g, 93%) as
1
Hz, 1H), 3.39 (dd, J = 12.0, 6.5 Hz, 1H), 3.70 (s, 2H), 3.72 (ABq, J =
12.2 Hz, 2H), 4.09 (d, J = 5.0 Hz, 1H), 4.28 (ddd, J = 6.5, 5.8, 5.0 Hz,
1H); 13C NMR (75 MHz, D2O) δ 48.1, 59.8, 61.5, 68.2, 75.6, 78.4;
MS (ESI) m/z = 164 (MH+); HRMS calculated for C6H13NO4 (MH+)
164.0923, found 164.0927.
inseparable mixture of diastereomers (dr = 2:3) as evaluated by H
NMR analysis of crude reaction mixture: Rf 0.33 (petroleum ether/
EtOAc, 8:2); IR (neat, ν, cm−1) 3454−3487 (br), 2117, 1076, 1028,
1
738; Partial interpretation δH and δC.; For major diastereomer, H
NMR (300 MHz, CDCl3) δ 1.31 (3H, s), 1.47 (3H, s), 2.75 (t, J = 6.7
Hz, exchangeable with D2O, 1H) 3.65−4.03 and 4.28−4.66 (multiple
signal, 11H), 5.92 (d, J = 3.5 Hz, 1H), 7.25−7.38 (Multiple signal,
10H); 13C NMR (75 MHz, CDCl3) δ 26.2, 26.7,63.5, 65.8, 71.3, 72.0,
73.6, 79.9, 81.5, 82.1, 104.4, 111.9, 127.6, 127.8, 128.1, 128.2, 128.4,
(3R,4S,5S)-2,2-Bis(hydroxymethyl)piperidine-3,4,5-triol (2c).
Reaction of 7c (300 mg, 0.65 mmol) with TFA−water (4 mL, 3:1)
followed by hydrogenation as described for 2b gave 2c (115 mg, 90%
over two steps) as semisolid: Rf 0.40 (25% aq NH4OH/MeOH, 1/99);
1
27
1
[α]D = +8.0 (c 2058, MeOH); IR (neat, ν, cm−1) 3439 (br); H
NMR (300 MHz, D2O) δ 2.90 (dd, J = 13.5, 4.1 Hz, 1H), 2.98 (dd, J =
13.5, 7.1 Hz, 1H), 3.61 (d, J = 11.7 Hz, 1H), 3.69 (d, J = 11.8 Hz, 1H),
3.72 (d, J = 11.7 Hz, 1H), 3.81 (d, J = 3.0 Hz, 1H), 3.82−3.90 (m,
1H), 3.95 (d, J = 11.8 Hz, 1H), 4.01 (t, J = 3.0 Hz, 1H); 13C NMR (75
MHz, D2O) δ 42.0, 60.5 (2C), 60.8, 67.9, 69.1, 69.4; MS (ESI) m/z =
194 (MH+); HRMS calculated for C7H15NO5 (MH+) 194.1028, found
194.1028.
128.6, 136.5, 137.4; For minor diastereomer, H NMR (300 MHz,
CDCl3) δ 1.32 (3H, s), 1.50 (3H, s), 2.64 (t, J = 6.7 Hz, exchangeable
with D2O, 1H) 3.65−4.03 and 4.28−4.66 (multiple signal, 11H), 5.92
(d, J = 3.5 Hz, 1H), 7.25−7.38 (Multiple signal, 10H); 13C NMR (75
MHz, CDCl3) δ 26.2, 26.8, 63.8, 66.4, 71.3, 71.8, 73.6, 80.3, 81.6, 82.1,
104.3, 112.0, 127.6, 127.8, 128.1, 128.2, 128.4, 128.6, 136.5, 137.4; MS
(ESI-, m/z) 455.88 (M+); LCMS (M+Na) = 478. Anal. Calculated For
C24H29N3O6: C, 63.28; H, 6.42; N, 9.22. Found: C, 63.49; H, 6.70; N,
8.98.
(3R,4S)-2, 2-Bis(hydroxymethyl)pyrrolidine-3,4-diol (1c). Re-
action of 7c (500 mg, 1.09 mmol) with TFA−water (4 mL, 3:1)
followed by NaIO4 and hydrogenation as described for 1b gave 1c
(135 mg, 75% over three steps) as a semisolid: Rf 0.42 (25% aq NH4/
Synthesis of Dichloro Alcohols (5c). Reaction of 4c (5.50 g,
13.88 mmol) as described for 5a gave dichloro alcohols 5c (6.67 g,
91%) as a inseparable mixture of diastereomer (2:3) as evaluated by
1H NMR analysis of crude reaction mixture: Rf 0.50 (petroleum ether/
EtOAc, 3:1); IR (KBr, ν, cm−1) 3452 (br), 1026, 1105, 738, 698;
25
MeOH, 1/99); [α]D = +15.1 (c 0.30 MeOH); IR (KBr, ν, cm−1)
1
3348 (br); H NMR (300 MHz, D2O) δ 3.37 (dd, J = 12.6, 3.0 Hz,
1
1H), 3.47 (dd, J = 12.6, 4.4 Hz, 1H), 3.76 (d, J = 12.0 Hz, 1H), 3.79
(d, J = 12.4 Hz, 1H), 3.87 (d, J = 12.0 Hz, 1H), 3.99 (d, J = 12.4 Hz,
1H), 4.34 (d, J = 4.7 Hz, 1H), 4.46−4.56 (m, 1H); 13C NMR (75
MHz, D2O) δ 48.5, 58.5, 60.1, 69.6, 70.1, 72.2; MS (ESI) m/z = 164
(MH+); HRMS calculated for C6H13NO4 (MH+) 164.0923, found
164.0927.
Partial interpretation of δH and δC; For major diastereomer, H NMR
(300 MHz, CDCl3) δ 1.35 (s, 3H), 1.57 (s, 3H), 3.47 (s, exchangeable
with D2O, 1H), 3.80 (ABq, J = 10.2 Hz, 2H), 4.16 (dd, J = 4.0, 4.0 Hz,
1H), 4.36−4.77 (multiple signal, 6H), 5.70 (d, J = 3.5 Hz, 1H), 5.95
(s, 1H), 7.28 −7.38 (Multiple signal, 10H); 13C NMR (75 MHz,
CDCl3) δ 26.7, 26.9, 69.2, 71.9, 73.8, 75.2, 76.1, 77.5, 77.7, 78.4, 104.1,
113.4, 127.6, 127.7, 127.8, 127.9, 128.0, 128.1, 128.3, 128.4, 128.5,
137.1, 137.5; For minor diastereomer, 1H NMR (300 MHz, CDCl3) δ
1.35 (s, 3H), 1.56 (3H, s), 3.53 (s, exchangeable with D2O, 1H), 3.81
(ABq, J = 10.2 Hz, 2H), 4.08 (dd, J = 4.3, 4.3 Hz, 1H), 4.36−4.77
(multiple signal, 6H), 5.74 (d, J = 3.6 Hz, 1H), 6.09 (s, 1H), 7.28
−7.38 (Multiple signal, 10H); 13C NMR (75 MHz, CDCl3) δ 26.8,
27.0, 67.0, 72.1, 73.7, 75.7, 76.0, 77.3, 77.8, 78.8, 104.0, 113.4, 127.6,
127.7, 127.8, 127.9, 128.0, 128.1, 128.3, 128.4, 128.5, 137.2, 137.3;
LCMS (MH+Na) = 507. Anal. Calculated For C24H28Cl2O6: C, 59.63;
H, 5.84. Found: C, 59.85; H, 6.10.
Synthesis of Azido Aldehydes (6c). Reaction of 5c (4.00 g, 8.29
mmol) with sodium azide as described for 6a gave azido-aldehydes 6c
(3.38 g, 90%) as inseparable mixture of diastereomers (2:3) as
evaluated by 1H NMR analysis of crude reaction mixture: Rf 0.50
(petroleum ether/EtOAc, 8:2); IR (KBr, ν, cm−1) 2993, 2987, 2933,
2127, 1741; Partial interpretation δH and δC.; For major diastereomer,
1H NMR (300 MHz, CDCl3) δ 1.33 (3H, s), 1.56 (s, 3H), 3.60−4.12
and 4.30−4.72 (multiple signal, 9H), 5.72 (d, J = 3.5 Hz, 1H), 7.24−
7.36 (Multiple signal, 10H), 9.61 (s,1H,); 13C NMR (75 MHz,
CDCl3) δ 26.3, 26.8, 71.0, 72.3, 73.2, 73.7, 77.0, 77.2, 77.8, 104.6,
113.6, 127.6, 127.7, 127.9, 128.2, 128.3, 128.5, 136.7, 136.9, 195.6; For
minor diastereomer, 1H NMR (300 MHz, CDCl3) δ 1.32 (3H, s), 1.56
(3H, s), 3.60−4.12 and 4.30−4.72 (multiple signal, 9H), 5.70 (d, J =
3.5 Hz, 1H), 7.24−7.36 (Multiple signal, 10H), 9.48 (s, 1H); 13C
NMR (75 MHz, CDCl3) δ 26.5, 26.8, 69.5, 72.2, 73.1, 73.7, 76.6, 77.4,
77.7, 104.3, 113.6, 127.6, 127.7, 127.9, 128.2, 128.3, 128.5, 136.7,
136.9, 196.7. Anal. Calculated For C24H27N3O6: C, 63.56; H, 6.00; N,
9.27. Found: C, 63.87; H, 6.31; N, 9.53.
Synthesis of Dichloro Alcohols (5b). Reaction of 4b (5.10 g,
12.81 mmol) with LDA as described for 5a for 6 h gave dichloro
alcohols 5b (5.50 g, 89%) as inseparable mixture of diastereomers (dr
= 2:3) as evaluated by the 1H NMR analysis of crude reaction mixture:
Rf 0.50 (petroleum ether/EtOAc, 8:2); IR (KBr, ν, cm−1) 3435 (st),
1080, 736, 698; Partial interpretation of δH and δC; For major
1
diastereomer, H NMR (300 MHz, CDCl3) δ 1.33 (s, 3H), 1.50 (s,
3H), 3.80−4.20 and 4.30−4.75 (multiple signal, 9H), 4.40 (bs,
exchangeable with D2O, 1H), 5.96 (d, J = 3.4 Hz, 1H), 6.09 (s, 1H),
7.06−7.38 (Multiple signal, 10H); 13C NMR (75 MHz, CDCl3) δ
26.2, 26.6, 72.12, 73.7, 74.4, 75.2, 75.8, 79.5, 81.4, 84.8, 103.6, 111.9,
127.5, 127.6, 127.8, 128.0, 128.1, 128.2, 128.5, 128.6, 135.8, 137.8; For
minor diastereomer, 1H NMR (300 MHz, CDCl3) δ 1.34 (s, 3H), 1.49
(s, 3H), 3.80−4.20 and 4.30−4.75 (multiple signal, 9H), 5.29 (bs,
exchangeable with D2O, 1H), 5.98 (d, J = 3.8 Hz, 1H), 6.19 (s, 1H),
7.06−7.38 (Multiple signal, 10H); 13C NMR (75 MHz, CDCl3) δ
26.4, 26.9, 70.8, 72.08, 72.12, 75.0, 77.4, 78.0, 81.6, 84.7, 104.0, 112.2,
127.5, 127.6, 127.8, 128.0, 128.1, 128.2, 128.5, 128.6, 136.1, 137; MS
(ESI-, m/z) 483.01 (MH+); LCMS (MH + Na) = 507. Anal.
Calculated For C24H28Cl2O6: C, 59.63; H, 5.84. Found: C, 59.27; H,
6.12.
Synthesis of Azido Aldehydes (6b). Reaction of 5b (3.30 g, 6.84
mmol) with sodium azide as described for 6a gave azido aldehydes 6b
(2.87 g, 92%) as inseparable mixture of diastereomers (dr = 2:3) as
evaluated by 1H NMR analysis of crude reaction mixture: Rf 0.50
(petroleum ether/EtOAc = 8:2); IR (neat, ν, cm−1) 2928, 2125, 1730,
1
1074; Partial interpretation δH and δC.; For major diastereomer, H
NMR (300 MHz, CDCl3) δ 1.28 (3H, s), 1.45 (3H, s), 3.68−4.06 and
4.24−4.59 (multiple signal, 9H), 5.89 (d, J = 3.5 Hz, 1H), 7.19−7.39
(Multiple signal, 10H), 9.66 (s, 1H); 13C NMR (75 MHz, CDCl3) δ
26.2, 26.8, 70.3, 72.2, 72.7, 73.6, 81.1, 81.3, 81.9, 105.2, 112.5, 127.5,
127.8, 128.0, 128.2, 128.3, 128.4, 128.5, 128.6, 136.3, 137.2, 195.2; For
minor diastereomer, 1H NMR (300 MHz, CDCl3) δ 1.32 (s, 3H), 1.48
(s, 3H), 3.80−4.06 and 4.24−4.49 (multiple signal, 9H), 5.96 (d, J =
3.8 Hz, 1H), 7.19−7.39 (Multiple signal, 10H), 9.60 (s, 1H); 13C
NMR (75 MHz, CDCl3) δ 26.4, 26.9, 69.7, 70.7, 73.7, 76.6, 81.7, 81.9,
82.1, 105.0, 112.3, 127.5, 127.8, 128.0, 128.2, 128.3, 128.4, 128.5,
Synthesis of Azido Alcohols (7c). Reaction of 6c (2.20 g, 4.85
mmol) with NaBH4 as described for 7a gave azido-alcohols 7c (2.08 g,
94%) as inseparable mixture of diastereomers (2:3) as evaluated by 1H
NMR analysis of crude reaction mixture: Rf 0.33 (petroleum ether/
EtOAc, 8:2); IR (neat, ν, cm−1) 3489−3508 (br), 2115; Partial
interpretation δH and δC.; For major diastereomer, 1H NMR (300
MHz, CDCl3) δ 1.35 (s, 3H), 1.56 (s, 3H), 2.69 − 2.73 (m,
exchangeable with D2O, 1H), 3.51−4.19 and 4.46−4.80 (multiple
signal, 11H), 5.74 (d, J = 3.8 Hz, 1H), 7.26−7.37 (Multiple signal,
H
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10H); 13C NMR (75 MHz, CDCl3) δ 26.6, 26.9, 63.9, 66.1, 70.1, 72.2,
73.6, 77.2, 77.7, 79.4, 104.0, 113.3, 127.5, 127.6, 127.7, 127.8, 128.0,
128.1, 128.2, 128.3, 128.4, 128.5, 128.6, 136.9, 137.4; For minor
R. Tetrahedron: Asymmetry 2009, 20, 672. (u) Winchester, B. G.
Tetrahedron: Asymmetry 2009, 20, 645. (v) Luo, B.; Marcelo, F.; Desir,
J.; Zhang, Y.; Sollogoub, M.; Kato, A.; Adachi, I.; Canada, F. J.;
Jimenez-Barbero, J.; Bleriot, Y. J. Carbohydr. Chem. 2011, 30, 641.
(3) (a) Asano, N.; Yamauchi, T.; Kagamifuchi, K.; Shimizu, N.;
Takahashi, S.; Takatsuka, H.; Ikeda, K.; Kizu, H.; Chuakul, W.;
Kettawan, A.; Okamoto, T. J. Nat. Prod. 2005, 68, 1238. (b) Asano, N.;
Nishida, M.; Kato, A.; Kizu, H.; Matsui, K.; Shimada, Y.; Itoh, T.; Baba,
M.; Watson, A. A.; Nash, R. J.; Lilley, P. M.; de., Q.; Watkin, D. J.;
Fleet, G. W. J. J. Med. Chem. 1998, 41, 2565. (c) Ye, X.-S.; Sun, F.; Liu,
M.; Li, Q.; Wang, Y.; Zhang, G.; Zhang, L.-H.; Zhang, X.-L. J. Med.
Chem. 2005, 48, 3688.
(4) (b) Ostrowski, J.; Altenbach, H.-J.; Wischnat, R.; Brauer, D. J.
Eur. J. Org. Chem. 2003, 1104. (b) Schuster, M. Bioorg. Med. Chem.
Lett. 1999, 9, 615.
(5) Gupta, P.; Vankar, Y. D. Eur. J. Org. Chem. 2009, 1925.
(6) (a) Schieweck, F.; Altenbach, H. J. Chem. Soc., Perkin Trans. 1
1
diastereomer, H NMR (300 MHz, CDCl3) δ 1.36 (s, 3H), 1.60 (s,
3H), 2.69 − 2.73 (m, exchangeable with D2O, 1H), 3.51−4.19 and
4.46−4.80 (multiple signal, 11H), 5.79 (d, J = 3.8 Hz, 1H), 7.26−7.37
(Multiple signal, 10H); 13C NMR (75 MHz, CDCl3) δ 26.6, 26.9,
62.1, 66.5, 66.9, 72.1, 73.5, 77.1, 77.3, 79.5, 104.2, 113.3, 127.5, 127.6,
127.7, 127.8, 128.0, 128.1, 128.2, 128.3, 128.4, 128.5, 128.6, 136.3,
137.6; LCMS (M+Na) = 478. Anal. Calculated For C24H29N3O6: C,
63.28; H, 6.42; N, 9.22. Found: C, 63.46; H, 6.68; N, 9.50.
ASSOCIATED CONTENT
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S
* Supporting Information
1
Copies of H and 13C NMR spectra of compounds 4a, 5a−c,
6a−c, 7a−c, 8a−c, 2a−c, and 1b−c as well as crystallographic
data (CIF) of compound 5a and 8a, glycosidase inhibition
assay, Lineweaver−Burk plots and docking tables/plots. This
material is available free of charge via the Internet at http://
pubs.acs.org.
́ ́
2001, 3409. (b) Otero, J. M.; Soengas, R. G.; Estevez, J. C.; Estevez, R.
J.; Watkin, D. J.; Evinson, E. L.; Nash, R. J.; Fleet, G. W. J. Org. Lett.
2007, 9 (4), 623.
(7) (a) Otero, J. M.; Estev
Nash, R. J.; Fleet, G. W. J.; Estev
2008, 19, 2443. (b) Soengas, R. G.; Estev
2010, 5190.
́
ez, A. M.; Soengas, R. G.; Estev
ez, R. J. Tetrahedron: Asymmetry.
ez, A. M. Eur. J. Org. Chem.
́
ez, J. C.;
́
AUTHOR INFORMATION
Corresponding Author
*E-mail: ddd@chem.unipune.ac.in.
́
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(8) (a) Dhavale, D. D.; Markad, S. D.; Karanjule, N. S.;
PrakashaReddy, J. J. Org. Chem. 2004, 69, 4760. (b) Patil, N. T.;
Tilekar, J. N.; Dhavale, D. D. J. Org. Chem. 2001, 66, 1065. (c) Markad,
S. D.; Karanjule, N. S.; Sharma, T.; Sabharwal, S. G.; Dhavale, D. D.
Bioorg. Med. Chem. 2006, 14, 5535. (d) Matin, M. M.; Sharma, T.;
Sabharwal, S. G.; Dhavale, D. D. Org. Biomol. Chem. 2005, 3, 1702.
(e) Dhavale, D. D.; Matin, M. M.; Sharma, T.; Sabharwal, S. G. Bioorg.
Med. Chem. 2004, 12, 4039. (f) Dhavale, D. D.; Ajish Kumar, K. S.;
Chaudhari, V. D.; Sharma, T.; Sabharwal, S. G.; PrakashaReddy., J.
Org. Biomol. Chem. 2005, 3, 3720. (g) Ajish Kumar, K. S.; Chaudhari,
V. D.; Puranik, V. G.; Dhavale, D. D. Eur. J. Org. Chem. 2007, 29, 4895.
(h) Mane, R. S.; Ajish Kumar, K. S.; Dhavale, D. D. J. Org. Chem. 2008,
73, 3284. (i) Jabgunde, A. M.; Kalamkar, N. B.; Chavan, S. T.;
Sabharwal, S. G.; Dhavale, D. D. Bioorg. Med. Chem. 2011, 19, 5912
and references cited therein. (j) Sanap, S. P.; Ghosh, S.; Jabgunde, A.
M.; Pinjari, R. V.; Gejji, S. P.; Singh, S.; Chopade, B. A.; Dhavale, D. D.
Org. Biomol. Chem. 2010, 8, 3307. (k) Karanjule, N. S.; Markad, S. D.;
Sharma, T.; Sabharwal, S. G.; Puranik, V. G.; Dhavale., D. D. J. Org.
Chem. 2005, 70, 1356.
(9) (a) Reeve, W. Synthesis 1971, 3, 131. (b) Corey, E. J.; Link, J. O.
Tetrahedron lett. 1992, 33, 3431. (c) Corey, E. J.; Link, J. O. J. Am.
Chem. Soc. 1992, 114, 1906. (d) Snowdem, T. S. ARKIVOC 2012, 24.
(10) (a) Sato, K.; Kajihara, Y.; Nakamura, Y.; Yoshimura, J. Chem.
Lett. 1991, 1559. (b) Sato, K.; Suzuki, K.; Ueda, M.; Kajihara, Y.; Hori,
H. Bull. Chem. Soc. Jpn. 1997, 70, 225. (c) Sato, K.; Sekiguchi, T.;
Hozumi, T.; Yamazaki, T.; Akai, S. Tetrahedron Lett. 2002, 43, 3087.
(d) Yoshikawa, M.; Yokokawa, Y.; Okuno, Y.; Murakami, N.
Tetrahedron 1995, 51 (22), 6209. (e) Sarda, P.; Olesker, A.; Lukacs,
G. Tetrahedron 1997, 53 (15), 5493. (f) Sato, K.; Akai, S.; Shoji, H.;
Sugita, N.; Yoshida, S.; Nagai, Y.; Suzuki, K.; Nakamura, Y.; Kajihara,
Y.; Funabashi, M.; Yoshimura, J. J. Org. Chem. 2008, 73, 1234.
(g) Cafiero, L. R.; Snowden, T. S. Org. Lett. 2008, 10, 3853.
(h) Sorensen, M. H.; Nielsen, C.; Nielsen, P. J. Org. Chem. 2001, 66,
4878.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
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We are thankful to Department of Science and Technology,
New Delhi (Project File No. SR/S1/OC-20/2010) for
providing financial support. Authors N.J.P. and S.T.C. are
thankful to UGC and CSIR, New Delhi for providing the
Senior Research Fellowship.
REFERENCES
■
(1) Asano, N.; Oseki, K.; Kiuz, H.; Matsui, K. J. Med. Chem. 1994, 37,
3701.
(2) (a) Bols, M.; Lillelund, V. H.; Jensen, H. H.; Liang, X. Chem. Rev.
2002, 102, 515. (b) Heightman, T. D.; Vasella, A. T. Angew. Chem., Int.
Ed. 1999, 38, 750. (c) Stutz, A. E. Iminosugars as Glycosidase Inhibitors,
Nojirimycin and Beyond; Wiley-VCH: Weinheim, 1999. (d) See the
recent book on iminosugars: Compain, P., Martin, O. R., Eds.;
Imunosugars: From Synthesis to Therapeutic Applications; Wiley: New
York, 2007. (e) Blanco, M. J.; Sardina, F. J. J. Org. Chem. 1998, 63,
3411. (f) Burley, I.; Hewson, A. T. Tetrahedron Lett. 1994, 35, 7099.
(g) Bols, M. Tetrahedron Lett. 1996, 37, 2097. (h) Pawar, V. U.;
Chavan, S. T.; Sabharwal, S. G.; Shinde, V. S. Bioorg. Med. Chem. 2010,
18, 7799. (i) Kato, A.; Kato, N.; Kano, E.; Adachi, I.; Ikeda, K.; Yu, L.;
Okamoto, T.; Banba, Y.; Ouchi, H.; Takahata, H.; Asano, N. J. Med.
Chem. 2005, 48, 2036. (j) Simone, M. I.; Soengas, R. G.; Jenkinson, S.
F.; Evinson, E. L.; Nash, R. J.; Fleet, G. W. J. Tetrahedron: Asymmetry
2012, 23, 401. (k) Dragutan, I.; Dragutan, V.; Demonceau, A. RSC
Adv. 2012, 2, 719. (l) Moreno-Clavijo, E.; Carmona, A. T.; Moreno-
Vargas, A. J.; Molina, L.; Robina, I. Curr. Org. Synth. 2011, 8, 102.
(m) Dragutan, I.; Dragutan, V.; Mitan, C.; Vosloo, H. C. M.; Delaude,
L.; Demonceau, A. Beilstein J. Org. Chem. 2011, 7, 699. (n) Oulaidi, F.;
Front-Deschamps, S.; Gallienne, E.; Lesellier, E.; Ikeda, K.; Asano, N.;
Compain, P.; Martin, O. R. ChemMedChem 2011, 6, 353. (o) Wardrop,
(11) (a) Yu, H.; Cao, H.; Tiwari, V. K.; Li, Y.; Chen, X. Bioorg. Med.
Chem. Lett. 2011, 21, 5037. (b) Hanaya, T.; Sugiyama, K -i.;
Kawamoto, H.; Yamamoto, H. Carbohydr. Res. 2003, 338, 1641.
(c) Malik, S.; Dixit, V. A.; Bharatam, P. V.; Kartha, K. P. R. Carbohydr.
Res. 2010, 345, 559.
D. J.; Waidyarachchi, S. L. Nat. Prod. Rep. 2010, 27, 1431. (p) Estev
A. M.; Soengas, R. G.; Otero, J. M.; Estevez, J. C.; Nash, R. J.; Estev
́
ez,
ez,
́
́
R. J. Tetrahedron: Asymmetry 2010, 21, 21. (q) Cipolla, L; Araujo, A.
́
(12) From the 1NMR spectrum of crude product 5b/5c, the
diastereomeric ratio of C-5 epimeric compounds was found to be
∼2:3. Our attempts to separate diastereomeric mixture using column/
flash chromatography were unsuccessful. As the C-5 stereocenter is
destroyed in the final product to get geminal-dihydroxymethyl group,
C.; Bini, D.; Gabrielli, L.; Russo, L.; Shaikh, N. Expert Opin. Drug
Discovery 2010, 5, 721. (r) Compain, P.; Decroocq, C.; Iehl, J.; Holler,
́
M.; Hazelard, D.; Barragan, T. M.; Mellet, C. O.; Nierengarten, J.-F.
Angew. Chem., Int. Ed. 2010, 49, 5753. (s) Davis, B. G. Tetrahedron:
Asymmetry 2009, 20, 652. (t) Compain, P.; Chagnault, V.; Martin, O.
I
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we continued with the diastereomeric mixture of 5b and 5c for further
steps.
(13) Sali, A.; Blundell, T. L. J. Mol. Biol. 1993, 234, 779.
(b) Laskowski, R. A.; MacArthur, M. W.; Moss, D .S.; Thornton, J.
M. J. Appl. Crystallogr. 1993, 26, 283. (c) Morris, G. M.; Goodsell, D.
S.; Halliday, R. S.; Huey, R.; Hart, W. E.; Belew, R. K.; Olson, A. J. J.
Comput. Chem. 1998, 19, 1639.
(14) Vogel, A. I., Tatchell, A. R., Furnis, B. S., Hannaford, A. J.,
Smith, P. W. G. Vogel's Textbook of Practical Organic Chemistry (5th
Edition), Addison-Wesley, 1989.
J
dx.doi.org/10.1021/jo3009534 | J. Org. Chem. XXXX, XXX, XXX−XXX