Synthesis and evaluation of the glycosidase inhibitory activity of 5-hydroxy substituted isofagomine analogues

Article abstract of DOI:10.1039/b418283a

An efficient strategy for the synthesis of 5-hydroxy substituted isofagomine analogues 4a, 4b and 4c, having both -CH₂OH/CH ₃ and -OH functionality at the C-5 position, and evaluation of their inhibitory potency is reported. The synt

Full text of DOI:10.1039/b418283a

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A R T I C L E
Synthesis and evaluation of the glycosidase inhibitory activity of
5-hydroxy substituted isofagomine analogues
Mohammed M. Matin,a Tarun Sharma,b Sushma G. Sabharwalb and Dilip D. Dhavale*c
a Department of Chemistry, University of Chittagong, Chittagong 4331, Bangladesh
b Division of Biochemistry, Department of Chemistry, University of Pune, Pune 411 007, India
c Garware Research Centre, Department of Chemistry, University of Pune, Pune 411 007, India.
E-mail: ddd@chem.unipune.ernet.in; Fax: +91-20-2569-1728
Received 3rd December 2004, Accepted 16th February 2005
First published as an Advance Article on the web 29th March 2005
An efficient strategy for the synthesis of 5-hydroxy substituted isofagomine analogues 4a, 4b and 4c, having both
–CH2OH/CH3 and –OH functionality at the C-5 position, and evaluation of their inhibitory potency is reported.
The synthetic methodology involves the aldol–Cannizzaro reaction of easily available a-D-xylopentodialdose
followed by hydrogenolysis to afford the triol 5. Selective amidation of the a- and b-hydroxymethyl group at C-4,
deprotection of the 1,2-acetonide group and hydrogenation gave the target molecules, which were found to be potent
against b-glycosidases with IC50 values in the micro molar range. Compound 4c showed excellent potency against
glycosidases and human salivary amylase.
Introduction
A number of natural as well as synthetic analogues of aza-
sugars such as nojirimycin 1a, 1-deoxynojirimycin 1b and 1,2-
dideoxynojirimycin namely fagomine 2 (Fig. 1) are potent
glycosidase inhibitors and are therefore of significant thera-
peutic interest in the treatment of diabetes, viral infection and
influenza.1 In the search for the design and development of the
anomer-selective b-glycosidase inhibitors, Bols and co-workers
noticed a subtle change in the glycosidase inhibitory activity
by moving the nitrogen atom of fagomine 2 to the anomeric
position C-1. This led to the development of isofagomine
3a which showed stronger and more selective b-glucosidase
inhibitory activity.2 The 5-hydroxy isofagomine 3b is notable
and found to be an inhibitor of glycolipid biosynthesis although
with little inhibitory activity against glycosidases.3 As part
of our continuing efforts in the area of azasugars,4 we are
now reporting the synthesis of hitherto unknown 5-hydroxy
isofagomine analogues 4a–c (Fig. 1) and their glycosidase
inhibitory activity. Pandey and co-workers have reported the
synthesis of compound 3c however; mistakenly the structure of
the compound was drawn as 4b.2i,5
Scheme 1 Reagents and conditions: (a) see ref. 4e; (b) TsCl, pyridine,
−15 ◦C, 24 h, 57%; (c) NaN3, DMF, 110 ◦C, 60 h, 30%; (d) i. LAH, THF,
0 ◦C–rt, 1.5 h; ii. CbzC1, NaHCO3, EtOH–H2O, 4 h, 83%; (e) TFA–H2O
(3 : 2), 0 ◦C–rt, 2.5 h, 97%; (f) HCOONH4, 10% Pd/C, MeOH, reflux,
45 min, 91%; (g) dry MeOH, HCl, 25 ◦C, 2 h, 98%.
O-benzyl-1,2-O-isopropylidene-a-D-xylopentodialdose.4e Tosy-
lation of 5 furnished the crystalline compound 6 (57%) wherein
the 4b-O-hydroxymethylene group was selectively tosylated. The
assignment of structure 6 was established by 1D-NOESY in
which irradiation of a signal at d 4.26 (H-3a) showed NOE for
the methylene protons at d 3.65 and 3.88 indicating the presence
of a 4a-CH2OH group with (4S) absolute configuration. The for-
mation of 6 could be attributed to the presence of an a-oriented
1,2-acetonide functionality that hindered the approach of the
bulky tosyl group from the a-face.6 In the next step, treatment
of 6 with NaN3 in DMF afforded 7 as an amorphous solid. An
1
interesting observation was noticed in the H NMR spectrum
of 7 in which the H-3 proton was found to be considerably
downfield, appearing at d 5.03, as compared to the normal
position (d ∼4.00). This downfield shift could be attributed to
the diamagnetic anisotropic effect of the azide group. In the
next step, the reduction of the azide functionality in 7 with
LAH and selective N-Cbz protection gave amino alcohol 8 as a
syrup. Finally, hydrolysis of the 1,2-acetonide functionality and
hydrogenation (ammonium formate and 10% Pd/C) afforded
5-hydroxy isofagomine 4a as a thick oil. Treatment of 4a with
MeOH–HCl gave hydrochloride salt 9a.
Fig. 1 Azasugar analogues.
Results and discussion
Synthesis of (3S, 4R, 5R)-3,4,5-trihydroxy-5-hydroxymethylpip-
Synthesis of (3S, 4R, 5S)-3,4,5-trihydroxy-5-hydroxymethylpip-
eridine (4b)
eridine (4a)
The synthesis of 5-hydroxy isofagomine 4b, the C-5 epimer of 4a,
requires selective tosylation of the 4a-hydroxymethylene group
in 5. Thus, treatment of triol 5 with 2,2-dimethoxy propane
Our synthetic strategy begins with the known triol 5 (Scheme 1)
that was easily obtained by the aldol–Cannizzaro reaction of 3-
1 7 0 2
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 1 7 0 2 – 1 7 0 7
T h i s j o u r n a l i s
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5
©

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Table 1 1H–1H coupling constants in compounds 4a–c and 9a,b
and p-TSA (cat.) in methanol afforded the 1,2 : 3,5-di-O-
isopropylidene derivative 10 (Scheme 2) as the only product
(57%).4e The tosylation of the free 4a-hydroxymethylene group
in 10 gave 11 that on treatment with sodium azide afforded 12.
The reduction of 12 with LAH and selective N-Cbz protection
furnished 13 (88%). In the final step, one pot hydrolysis of
both acetonide groups in 13 followed by hydrogenation afforded
4b as a thick oil. The reaction of 4b with MeOH–HCl gave
hydrochloride salt 9b.3
J/Hz
Compound no. J2a,2e
J2a,3a J2e,3a J2e,6e J3a,4a J6a,6e J7a,7b
4a
9a
4b
9b
4c
11.0
11.6
12.0
11.9
11.9
10.8 5.3
11.0 5.4
12.0 4.9
11.9 5.2
11.9 5.3
1.5
2.0
1.7
1.7
1.8
9.4
9.1
9.4
9.4
9.4
11.0 13.4
11.6 13.4
13.5 11.7
13.2 11.7
13.2
—
5
2
might exist in either C2 or C5 conformations depending on
the type and orientation of substituents at C3–C5.4c Therefore,
the conformations of 4a–c were studied using coupling constant
1
information obtained from H NMR decoupling experiments
(Table 1). In 4a, the appearances of a doublet of doublet for H-2a
at d 2.16 (J2a,2e = 11.0 and J2a,3 = 10.8 Hz) and a ddd for H-2e at d
2.92 (J2e,2a = 11.0, J2e,3 = 5.3 and J2e,6e = 1.5 Hz) were informative.
The large coupling constant (J2a,3 = 10.8 Hz) for the H-2 axial
proton requires a trans-diaxial relationship with H-3. In addi-
tion, the trans-diaxial disposition of the H-3 and H-4 protons
was evident from the large coupling constant (J3,4 = 9.4 Hz). In
the precursor 8, the relative stereochemistry of the substituents
at C-2, C-3 and C-3, C-4 is trans and the same stereochemistry
is retained in the product. Based on this data compound 4a
Scheme 2 Reagents and conditions: (a) 2,2-dimethoxy propane, p-TSA,
MeOH, 25 ◦C, 5 min, 97%; (b) TsCl, pyridine, 0 ◦C–rt, 12 h, 92%;
(c) NaN3, DMF, TBAI, MS, 110 ◦C, 48 h, 62%; (d) i. LAH, THF,
0
◦C–rt, 1.5 h; ii. CbzCl, NaHCO3, EtOH–H2O, 0 ◦C–rt, 4 h, 88%;
(e) i. TFA–H2O (3 : 2), 0 ◦C–rt, 2.5 h, 95%; ii. HCOONH4, 10% Pd/C,
MeOH, reflux, 45 min, 83%; (f) dry MeOH, HCl, 25 ◦C, 2 h, 98%.
5
Synthesis of (3S, 4R, 5S)-3,4,5-trihydroxy-5-methylpiperidine
(4c)
was assigned the C2 conformation with a (5S) configuration
(Fig. 2). In this conformation, although the –CH2OH group
is axially oriented with 1,3-diaxial interactions, we believe that
the conformation (5C2) is stabilized by intramolecular hydrogen
bonding between the –CH2OH and the ring nitrogen atom as
shown in Fig. 2. This fact is supported by the 1H NMR spectrum
of 4a wherein the methylene protons (–CH2OH) were found to
be relatively shielded (d 2.56 and 2.72) as compared to their
normal position (d ∼3.50). This upfield shift could be attributed
to the hydrogen bonding that increases the electron density at
the oxygen atom (of –CH2OH) and thus makes it less electron
withdrawing compared with the normal oxygen atom. While, in
the 1H NMR spectrum of the corresponding hydrochloride salt
9a the methylene protons appeared at their normal positions [d
3.19 (d, J = 13.4 Hz) and 3.44 (d, J = 13.4 Hz)], probably due
to the loss of intramolecular hydrogen bonding. In the 1H NMR
spectrum of 4a, the appearance of H-6e as a doublet of doublet
at d 2.66 (J = 11.0 and 1.5 Hz) was due to ‘W’ type coupling
with H-2e. This was supported by the appearance of H-2e as a
ddd with J = 11.0, 5.3 and 1.5 Hz. The small J of 1.5 Hz was
thus due to ‘W’ type coupling as shown in Fig. 2.
During the synthesis of isofagomine 4a, the conversion of 6 to
azido derivative 7 resulted in a poor yield irrespective of a change
in reaction conditions like solvent, temperature and mole ratio.
In order to improve the yield, the reaction of 6 with NaN3 was
performed in the presence of TBAI (0.5 equiv) that furnished
two compounds, 7 and 14, in 22% and 19% yield, respectively
(Scheme 3). The exact mechanism for the formation of 14 is
not clear to us. However, we believe that the scrambling of the
tosyl group between the C4-hydroxymethylene groups leads to
the formation of a 4a-tosyl derivative that on SN2 displacement
with iodide afforded 14. Our attempts to improve the yield of 14
were unsuccessful. The structure of 14 was established by 1D-
NOESY wherein the irradiation of two proton singlets at d 3.65
(CH2I) showed NOE for the singlet at d 5.04 (H-3a) indicating
the a-orientation of the –CH2I group. In the subsequent step,
the reaction of 14 with LAH in THF furnished an amino
compound (as evident from the 1H NMR of the crude product)
that was directly converted to an N-Cbz protected amino alcohol
15. The removal of the 1,2-acetonide functionality followed by
hydrogenation gave isofagomine 4c as a thick oil with –OH and
–CH3 groups at the C-5 position.
Fig. 2 Conformations of azasugars.
In the 1H NMR spectrum of 4b, the appearance of one triplet
at d 2.57 for H-2a with large coupling constants (J2a,2e = J2a,3
12.0 Hz) indicated a trans-diaxial relationship of H-2a with the
H-3 proton. The H-2e appeared as a ddd at d 3.24 (J2e,2a
=
=
12.0, J2e,3 = 4.9 and J2e,6 = 1.7 Hz), wherein the small coupling
constant J2e,6 = 1.7 Hz with the H-6e proton was due to ‘W’
coupling. The H-4 proton appeared as a doublet with J = 9.4 Hz;
this clearly requires trans-diaxial orientation between the H-3
and H-4 protons. In the precursor 13, the C-4 and C-5 –OH
Scheme 3 Reagents and conditions: (a) NaN3, TBAI (0.5 equiv), DMF,
110 ◦C, 6 h, 41%; (b) i. LAH, THF, 0 ◦C–rt, 1.5 h; ii. NaHCO3, CbzCl,
MeOH–H2O, 0 ◦C–rt, 4 h, 89%; (c) i TFA–H2O (3 : 2), 0 ◦C–rt, 3 h; ii.
HCOONH4, 10% Pd/C, MeOH, reflux, 45 min, 72%.
5
groups are cis-orientated. Therefore, 4b was assigned the C2
conformation with a (5R) configuration. The 1H NMR spectra
of 4a/4b and their corresponding hydrochloride salts 9a/9b were
very similar with respect to coupling constants of protons (except
the downfield shifts of the H-2 and H-6 protons). This indicated
that the conformations of 4a and 4b remained unchanged in the
presence of a piperidinium ion.7
Conformational assignment of 4a, 4b and 4c
The isofagomine 3a is known to exist in a 2C5 conformation how-
ever; our recent studies indicated that isofagomine analogues
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 1 7 0 2 – 1 7 0 7
1 7 0 3

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#
Table 2 Ki*/IC50 values in lM
a-Glucosidasea
b-Glucosidaseb
a-Galactosidasec
>5000#
b-Galactosidased
>5000#
230*
4.3*
2000#
420#
610#
5.7*
a Yeast a-glucosidase. b Sweet almond b-glucosidase. c Green coffee bean a-galactosidase. d Aspergillus oryzae b-galactosidase.
1
In the case of 4c, the H NMR spectrum also showed the
trans-diaxial relationship between H-2a and H-3 as well as H-3
4a,4b and 5-hydroxy-5-methyl isofagomine analogue 4c. The
glycosidase inhibitory activity of 4a–c showed good inhibitory
potency against the b-glycosidases. Isofagomine 4c showed
excellent potency against human salivary amylase.
and H-4 as evident from the large coupling constants (J2a,3
=
11.9 and J3,4 = 9.4 Hz). As the trans relationship between the
C-4 and C-5 –OH groups in the precursor 15 should be retained
5
in the product, the C2 conformation with an axially oriented
methyl group and (5S) configuration was assigned to 4c.
Experimental
General methods
Glycosidase inhibitory study
Melting points were recorded with a Thomas Hoover melting
point apparatus and are uncorrected. IR spectra were recorded
with Shimadzu FTIR-8400 as a thin film or in nujol mull or using
Isofagomine is known to be a potent inhibitor of b-glucosidase
(IC50 0.11 lM) and most of the inhibition data for isofagomine
analogues is known in IC50 values. So the IC50 values were deter-
mined for compounds 4a–c and are summarized in Table 3. The
a-glucosidases however are generally more powerfully inhibited
by 1-deoxynojirimycin analogues. There are several explanations
available for the observed inhibitory profiles of isofagomine
compared to that of the related 1-deoxynojirimycin.8 For com-
parative studies, the inhibitory profile of previously known struc-
turally related compounds 16a and 16b was taken into account.
The IC50 values of 16a and 16b indicate that both compounds are
moderate to poor inhibitors of glycosidases (Table 2).1d However,
inhibition potential increased tremendously for compounds 4a
and 4b, which have a C3a-OH group (Table 3). Compound
4a showed selectivity towards b-glycosidase inhibition that is
an expected notion for the isofagomine class of glycosidase
inhibitors. Compound 4c, with methyl and hydroxyl groups
at C-5 and C3a–OH, strongly inhibits most of the glycosidase
enzymes. This result could be attributed to the hydrophobic
interaction of the CH3 group at the active site of glycosidases. In
addition, 4c also demonstrated excellent potency against human
salivary amylase.
1
KBr pellets and are expressed in cm−1. H (300 MHz) and 13C
(75 MHz) NMR spectra were recorded with Varian Mercury 300
using CDCl3 or D2O as a solvent. Chemical shifts were reported
in d unit (ppm) with reference to TMS as an internal standard
and J values are given in Hz. Elemental analyses were carried
out with Elemental Analyser Flash 1112. Optical rotations were
measured using a Bellingham Stanle◦y-ADP digital polarimeter
with sodium light (589.3 nm) at 25 C. Thin layer chromatog-
raphy was performed on Merck pre-coated 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. Methanol, DMF and
THF were purified and dried before use. Petroleum ether (PE)
that was used is a distillation fraction between 40–60 ◦C. LAH,
CbzCl, 10% Pd–C were purchased from Aldrich and/or Fluka.
After decomposition of the reaction with water, the work-up
involves washing of the combined organic layer with water,
brine, drying over anhydrous sodium sulfate and evaporation
of the solvent at reduced pressure. Triol 5 was prepared by
the aldol–crossed Cannizzaro reaction of dialdose and was
reported earlier.4e For enzyme inhibition studies, substrates were
purchased from Sigma Chemicals Co. USA. a-Glucosidase from
yeast, b-mannosidase from jack beans and b-galactosidase from
bovine testis were purchased from Sigma Chemicals Co. USA.
b-Glucosidase and b-galactosidase were extracted and purified
from sweet almonds.
Conclusion
Thus, we have demonstrated a convenient method for the
synthesis of 5-hydroxy-5-hydroxymethyl isofagomine analogues
Table 3 Inhibitory potencies of 1-azasugars 4a–c
IC50/lM
1,2-O-Isopropylidene-4-(S)-C-(hydroxymethyl)-5-O-p-toluen-
esulfonyl-b-L-threo-pento-1,4-furanose (6). To
a
cooled
solution of triol 5 (2.1 g, 9.53 mmol) at −15 ◦C in dry pyridine
(3 mL) was added p-toluenesulfonyl chloride (1.73 g, 9.07 mmol)
and stirring was continued at −15 ◦C for 24 h. The reaction
was decomposed by the addition of ice–water. Pyridine was
co-evaporated with toluene (2 × 3 mL). Chromatographic
purification (PE–ethyl acetate = 9 : 1) gave monotosyl derivative
6 (2.04 g, 57%) as a white solid, mp 132–133 ◦C. Found: C,
51.41; H, 6.02. Calc. for C16H22SO8 C, 51.33; H, 5.92; Rf 0.49
(66% ethyl acetate–n-hexane); [a]D −7.1 (c 0.85, CHCl3); mmax
(nujol) 3600–3220 (br band) and 1379 cm−1; dH (300 MHz,
CDCl3 + D2O) 1.33 (3H, s, CH3), 1.56 (3H, s, CH3), 2.49 (3H, s,
Enzyme
4a
4b
4c
a-Glucosidasea
NI
7.11
1.75
1.76
NI
1.89
1.77
0.34
b-Glucosidaseb
2.57
8.74
2.18
2.20
NI
16.78
17.12
16.85
NI
a-Galactosidaseb
b-Galactosidasec
a-Mannosidased
Human salivary amylase
6.43
a Yeast. b Almonds. c Bovine testis. d Jack bean. NI—inhibition not
observed under assay conditions. Data is average of three sets of assay
performed.
1 7 0 4
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 1 7 0 2 – 1 7 0 7

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CH3), 3.65 (1H, d, J = 12.2 Hz, CH2OH), 3.88 (1H, d, J =
12.2 Hz, CH2OH), 4.19 (1H, d, J = 10.0 Hz, CH2OTs), 4.23
(1H, d, J = 10.0 Hz, CH2OTs), 4.26 (1H, s, H3), 4.66 (1H, d,
J = 4.1 Hz, H2), 5.94 (1H, d, J = 4.1 Hz, H1), 7.40 (2H, d, J =
8.1 Hz, Ar-H), 7.84 (2H, d, J = 8.1 Hz, Ar-H); dC (75 MHz,
CDCl3) 21.7, 25.9, 26.6 (CH3), 61.4 (CH2OH), 66.7 (CH2OTs),
76.0 (C-3), 87.2 (C-4), 88.8 (C-2), 105.2 (C-1), 112.7 (OCO),
128.0, 130.0, 131.9, 145.5 (Ar–C).
through celite, washed with methanol and concentrated. The
concentrated thick liquid was purified by a silica column using
CHCl3–MeOH–NH3 (25% solution) = 50 : 49 : 1 as an eluant to
yield 4a (0.231 g, 91%) as a thick oil. Found: C, 44.20; H, 8.08.
Calc. for C6H13NO4 C, 44.16; H, 8.03; Rf 0.09 (50% MeOH–
CHCl3); [a]D +34.3 (c 0.35, MeOH); mmax (neat) 3600–3200 (br
band) cm−1; dH (300 MHz, D2O) 2.16 (1H, dd, J = 11.0 and
10.8 Hz, H2a), 2.39 (1H, d, J = 11.0 Hz, H6a), 2.56 (1H, d,
J = 13.4 Hz, O-CH2), 2.66 (1H, dd, J = 11.0 and 1.5 Hz, H6e),
2.72 (1H, d, J = 13.4 Hz, O-CH2), 2.92 (1H, ddd, J = 11.0, 5.3
and 1.5 Hz, H2e), 3.26 (1H, d, J = 9.4 Hz, H4), 3.58 (1H, ddd,
J = 10.8, 9.4 and 5.3 Hz, H3); dC (75 MHz, D2O) 45.6, 49.2
(C-2/C-6), 50.4 (CH2OH), 69.0, 73.7, 75.6 (C-3/C-4/C-5).
1,2-O-Isopropylidene-4-(S)-C-(hydroxymethyl)-5-azido-b-L-
threo-pento-1,4-furanose (7). To a solution of 6 (2.2 g,
5.9 mmol) in anhydrous DMF (12 mL) was added NaN3
(2.28 g, 35.2 mmol) and MS (1.5 g) and the reaction mixture
was stirred at 110 ◦C for 60 h. The reaction mixture was cooled
to room temperature. After adding water the reaction mixture
was extracted with ethyl acetate. The organic layer was dried,
concentrated and purified by chromatography (n-hexane–ethyl
acetate = 4 : 1) to furnish azido compound 7 (0.432 g, 30%)
as a white solid, mp 80–81 ◦C. Found: C, 44.14; H, 6.12. Calc.
for C9H15N3O5 C, 44.08; H, 6.16; Rf 0.22 (33% ethyl acetate–
n-hexane); [a]D −4.0 (c 1, CHCl3); mmax (nujol) 3500–3200 (br
band) and 2104 cm−1; dH (300 MHz, CDCl3) 1.36 (3H, s, CH3),
1.52 (3H, s, CH3), 1.70–1.98 (2H, br s, OH, exchange with
D2O), 3.86 (2H, AB quartet, J = 12.0 Hz, CH2N3), 4.36 (1H,
d, J = 7.5 Hz, CH2OH), 4.63 (1H, d, J = 7.5 Hz, CH2OH),
4.75 (1H, d, J = 2.9 Hz, H2), 5.03 (1H, s, H3), 6.26 (1H, d,
J = 2.9 Hz, H1); dC (75 MHz, CDCl3) 26.5, 27.5 (CH3), 62.8
(CH2N3), 78.7 (CH2OH), 84.6, 88.2, 89.6 (C-2/C-3/C-4), 107.8
(C-1), 114.3 (OCO).
(3S,4R,5S)-3,4,5-Trihydroxy-5-hydroxymethylpiperidine hy-
drochloride (9a). To a stirred solution of compound 4a (0.2 g,
1.3 mmol) in dry methanol was added HCl (0.2 mL) under
nitrogen. The reaction mixture was stirred at 25 ◦C for 2 h and
the solvent was evaporated under reduced pressure to give 9a
(0.24 g, 98%) as a semi-solid. Found: C, 36.12; H, 7.15. Calc. for
C6H14NO4Cl C, 36.09; H, 7.07; Rf 0.02 (80% MeOH–CHCl3);
[a]D +15.0 (c 0.4, MeOH); mmax (nujol) 3600–3220 (br band) cm−1;
dH (300 MHz, D2O) 2.90 (1H, dd, J = 11.6 and 11.0 Hz, H2a),
3.13 (1H, d, J = 11.6 Hz, H6a), 3.19 (1H, d, J = 13.4 Hz, O-
CH2), 3.40 (1H, dd, J = 11.6 and 2.0 Hz, H6e), 3.44 (1H, d,
J = 13.4 Hz, O-CH2), 3.54 (1H, ddd, J = 11.6, 5.4 and 2.0 Hz,
H2e), 3.69 (1H, d, J = 9.1 Hz, H4), 4.60 (1H, ddd, J = 11.0, 9.1
and 5.4 Hz, H3); dC (75 MHz, D2O) 44.2, 46.4 (C-2/C-6), 48.7
(CH2OH), 65.3, 69.6, 74.8 (C-3/C-4/C-5).
1,2-O-Isopropylidene-4-(S)-C-(hydroxymethyl)-5-(N-benzoxy-
carbonylamino)-b-L-threo-pento-1,4-furanose (8). To an ice
cooled suspension of LAH (0.464 g, 12.3 mmol) in dry THF
(10 mL) was added a solution of 7 (0.5 g, 2.04 mmol) in dry
THF (7 mL) over a period of 10 min. The reaction mixture was
warmed to room temperature and stirred for 1.5 h. Ethyl acetate
(10 mL) was added at 0 ◦C, stirred for 10 min and quenched
with a saturated solution of NH4Cl (2 mL). The solution was
filtered, the residue was washed with ethyl acetate (3 × 3 mL)
and worked up. The organic layer was concentrated, dried
and dissolved in ethanol–water (10 mL, 1 : 1), followed by the
1,2 : 3,5-Di-O-isopropylidene-4-(R)-C-(p-toluenesulfonyloxy-
methyl)-b-L-threo-pento-1,4-furanose (11). To a solution of 10
(1.0 g, 3.9 mmol) in anhydrous pyridine (2 mL) was added
p-toluenesulfonyl chloride (0.88 g, 4.6 mmol) at 0 ◦C. The
reaction mixture was allowed to reach room temperature and
was stirred for 12 h. Usual work-up and chromatography (PE–
ethyl acetate = 9.5 : 0.5) provided monotosylate 11 (1.47 g, 92%)
as a white solid, mp 114–115 ◦C. Found: C, 55.03; H, 6.37. Calc.
for C19H26SO8 C, 55.06; H, 6.32; Rf 0.43 (33% ethyl acetate–n-
hexane); [a]D −21.18 (c 0.85, CHCl3); mmax (KBr) 1375 cm−1; dH
(300 MHz, CDCl3) 1.27 (3H, s, CH3), 1.31 (3H, s, CH3), 1.37
(3H, s, CH3), 1.40 (3H, s, CH3), 2.47 (3H, s, CH3), 3.63 (1H, d,
J = 12.7 Hz, CH2), 3.94 (1H, d, J = 12.7 Hz, CH2), 3.99 (1H,
d, J = 10.0 Hz, CH2OTs), 4.26 (1H, s, H3), 4.32 (1H, d, J =
10.0 Hz, CH2OTs), 4.56 (1H, d, J = 3.8 Hz, H2), 5.99 (1H, d,
J = 3.8 Hz, H1), 7.38 (2H, d, J = 8.2 Hz, Ar-H), 7.83 (2H, d,
J = 8.2 Hz, Ar-H); dC (75 MHz, CDCl3) 20.6, 21.6, 25.3, 25.8,
26.8 (CH3), 62.1 (CH2), 68.9 (CH2OTs), 73.9 (C-3), 81.5 (C-4),
85.2 (C-2), 98.5 (OCO), 106.0 (C-1), 112.3 (OCO), 128.1, 129.9,
132.4, 145.1 (Ar-C).
◦
addition of NaHCO3 (0.479 g, 5.70 mmol) at 0 C and benzyl
chloroformate (0.522 g, 3.1 mmol). The mixture was stirred at
room temperature for 4 h, quenched with water and extracted
with ethyl acetate (3 × 10 mL). Work-up and chromatography
(n-hexane–ethyl acetate = 4 : 1) provided 8 (0.598 g, 83%) as a
syrup. Found: C, 57.83; H, 6.63. Calc. for C17H23NO7 C, 57.78;
H, 6.56; Rf 0.33 (66% ethyl acetate–n-hexane); [a]D −24.7 (c
1.0, CHCl3); mmax (neat) 3550–3200 (br band) and 1670 cm−1; dH
(300 MHz, CDCl3 + D2O) 1.29 (3H, s, CH3), 1.50 (3H, s, CH3),
3.50 (1H, d, J = 14.0 Hz, CHAHBNH), 3.64 (2H, AB quartet,
J = 13.6 Hz, CH2OH), 3.69 (1H, d, J = 14.0 Hz, CHAHBNH),
4.16 (1H, s, H3), 4.61 (1H, d, J = 4.1 Hz, H2), 5.11 (2H,
br s, O-CH2Ph), 5.93 (1H, d, J = 4.1 Hz, H1), 7.22–7.40 (5H,
m, Ar-H); dC (75 MHz, CDCl3 + D2O) 25.7, 26.7 (CH3),
42.9 (N-CH2), 61.0 (O-CH2Ph), 67.3 (CH2OH), 77.4, 87.2,
89.8 (C-2/C-3/C-4), 105.4 (C-1), 112.1 (OCO), 128.1, 128.5,
136.0 (Ar–C), 157.9 (CO). [The 13C NMR spectrum showed
doubling of signals due to rotational isomers possible because
of restricted rotation around the C–N bond].
1,2
:
3,5-Di-O-isopropylidene-4-(R)-C-(azidomethyl)-b-L-
mixture of 11 (1.2 g,
threo-pento-1,4-furanose (12).
A
2.9 mmol), NaN3 (1.13 g, 17.4 mmol), TBAI (0.015 g, cat) and
MS (1 g) in anhydrous DMF was stirred at 110 ◦C for 48 h.
The reaction mixture was cooled to room temperature. After
adding water the reaction mixture was extracted with ethyl
acetate. The organic layer was dried, concentrated and purified
by chromatography (n-hexane–ethyl acetate = 19 : 1) to furnish
azido compound 12 (0.512 g, 62%) as a pale yellow solid, mp
91–92 ◦C. Found: C, 50.59; H, 6.66. Calc. for C12H19N3O5 C,
50.52; H, 6.71); Rf 0.66 (33% ethyl acetate–n-hexane); [a]D +2.1
(c 0.95, CHCl3); mmax (nujol) 2098 cm−1; dH (300 MHz, CDCl3)
1.34 (3H, s, CH3), 1.39 (3H, s, CH3), 1.41 (3H, s, CH3), 1.62
(3H, s, CH3), 3.44 (1H, d, J = 12.6 Hz, CH2N3), 3.68 (2H, d,
J = 12.6 Hz, CH2N3 and O-CH2), 3.90 (1H, d, J = 12.6 Hz,
O-CH2), 4.15 (1H, s, H3), 4.63 (1H, d, J = 3.9 Hz, H2), 6.08
(1H, d, J = 3.9 Hz, H1); dC (75 MHz, CDCl3) 21.2, 25.3,
26.2, 26.4 (CH3), 53.2 (CH2N3), 63.0 (O-CH2), 75.0, 84.5, 85.0
(C-2/C-3/C-4), 99.0 (OCO), 106.2 (C-1), 112.2 (OCO).
(3S,4R,5S)-3,4,5-Trihydroxy-5-hydroxymethylpiperidine (4a).
To a solution of TFA–water (5 mL, 3 : 2) was added 8
◦
(0.55 g, 1.6 mmol) at 0 C, which was then stirred for 30 min.
The solution was allowed to warm to 25 ◦C and stirred for
2.5 h. TFA–water was co-evaporated with toluene under a
high vacuum to provide an anomeric mixture of hemiacetal
(0.473 g, 97%), which was directly used in the next reaction.
To a solution of hemiacetal in dry methanol (8 mL) was added
10% Pd/C (0.1 g) and ammonium formate (0.761 g, 12.1 mmol).
The reaction mixture was refluxed for 45 min and filtered
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 1 7 0 2 – 1 7 0 7
1 7 0 5

View Article Online
1,2
:
3,5-Di-O-isopropylidene-4-(R)-C-(N-benzoxycarbony-
1,2-O-Isopropylidene-4-(R)-C-(iodomethyl)-5-azido-b-L-threo-
pento-1,4-furanose (14). To a solution of 6 (2.0 g, 5.34 mmol) in
anhydrous DMF (12 mL) was added NaN3 (2.08 g, 32.0 mmol),
TBAI (0.5 equiv) and MS (1.5 g) and the reaction mixture was
stirred at 110 ◦C for 60 h. The reaction mixture was cooled
to room temperature. After adding water the reaction mixture
was extracted with ethyl acetate. The organic layer was dried,
concentrated and purified by chromatography (n-hexane–ethyl
acetate = 19 : 1) to furnish azido compound 14 (0.36 g, 19%)
as a syrup. Found: C, 30.49; H, 4.01. Calc. for C9H14N3O4I
C, 30.44; H, 3.97; Rf 0.66 (25% ethyl acetate–n-hexane); [a]D
−49.33 (c 1.5, CH2Cl2); mmax (neat) 3550–3250 (br band), 2104
and 1230 cm−1; dH (300 MHz, CDCl3) 1.40 (3H, s, CH3), 1.57
(3H, s, CH3), 1.61–1.80 (1H, br s, OH, exchange with D2O),
3.65 (2H, s, CH2I), 4.42 (1H, d, J = 7.5 Hz, CH2N3), 4.67
(1H, d, J = 7.5 Hz, CH2N3), 4.74 (1H, d, J = 3.2 Hz, H2),
5.04 (1H, s, H3), 6.27 (1H, d, J = 3.2 Hz, H1); dC (75 MHz,
CDCl3) 26.6, 27.6 (CH3), 53.0 (CH2N3), 79.4 (CH2I), 84.2, 87.2
(C-2/C-3), 87.8 (C-4), 107.7 (C-1), 114.8 (OCO).
laminomethyl)-b-L-threo-pento-1,4-furanose (13). To an ice
cooled suspension of LAH (0.319 g, 8.4 mmol) in dry THF
(10 mL) was added a solution of 12 (0.4 g, 1.40 mmol) in dry
THF (7 mL) over a period of 10 min. The reaction mixture was
warmed to room temperature and stirred for 1.5 h. Ethyl acetate
(10 mL) was added at 0 ◦C, stirred for 10 min and quenched with
a saturated solution of NH4Cl (2 mL). The solution was filtered,
the residue washed with ethyl acetate (3 × 3 mL) and worked
up. The organic layer was concentrated, dried and dissolved in
ethanol–water (5 mL, 1 : 1) followed by the addition of NaHCO3
(0.329 g, 3.92 mmol) at 0 ◦C and benzyl chloroformate (0.358 g,
2.1 mmol). The mixture was stirred at room temperature for 4 h,
quenched with water and extracted with chloroform (3 × 10 mL).
Work-up and chromatography (n-hexane–ethyl acetate = 25 : 1)
provided 13 (0.485 g, 88%) as a solid, mp 84–85 ◦C. Found: C,
61.15; H, 7.00. Calc. for C20H27NO7 C, 61.06; H, 6.92; Rf 0.63
(25% ethyl acetate–n-hexane); [a]D −19.44 (c 0.72, CHCl3); mmax
(KBr) 3360–3100 (br band), 1693 cm−1; dH (300 MHz, CDCl3)
1.32 (3H, s, CH3), 1.38 (3H, s, CH3), 1.40 (3H, s, CH3), 1.54
(3H, s, CH3), 3.47 (1H, dd, J = 14.0 and 2.9 Hz, CH2N3), 3.64
(1H, d, J = 12.3 Hz, O-CH2), 3.72 (1H, dd, J = 14.0 and 8.0 Hz,
CH2N3), 3.78 (1H, d, J = 12.3 Hz, O-CH2), 4.13 (1H, s, H3),
4.61 (1H, d, J = 3.8 Hz, H2), 5.14 (2H, d, J = 3.3 Hz, O-
CH2Ph), 5.26–5.29 (1H, br d, J = 8.0 Hz, NH, exchange with
D2O), 6.02 (1H, d, J = 3.8 Hz, H1), 7.30–7.45 (5H, m, Ar-H)
[on D2O exchange, the doublet of doublets at d 3.47 and 3.72
became doublets with J = 14.0 Hz]; dC (75 MHz, CDCl3) 21.2,
25.3, 26.1, 26.3 (CH3), 44.0 (N-CH2), 63.3 (O-CH2Ph), 66.6 (O-
CH2), 75.3, 84.3, 85.2 (C-2/C-3/C-4), 98.9 (OCO), 105.8 (C-1),
112.1 (OCO), 127.9, 128.1, 128.3, 136.3 (Ar-C), 156.6 (CO).
Further elution with n-hexane–ethyl acetate (4 : 1) provided
the azido compound 7 (0.288 g, 22%) as a white solid, mp 80–
81 ◦C.
1,2-O-Isopropylidene-4-(R)-C-(methyl)-5-(N-benzoxycarbon-
ylamino)-b-L-threo-pento-1,4-furanose (15). A solution of 14
(0.35 g, 0.986 mmol) in THF (6 mL) was added to a suspension
of◦LAH (0.224 g, 5.9 mmol) in THF over a period of 10 min at
0 C. The reaction mixture was warmed to room temperature,
stirred for 1.5 h and worked up as described for compound
7. The residue was dissolved in ethanol–water (5 mL, 1 : 1)
followed by the addition of NaHCO3 (0.231 g, 2.75 mmol) at
0
◦C and benzyl chloroformate (0.252 g, 1.477 mmol). The
(3S,4R,5R)-3,4,5-Trihydroxy-5-hydroxymethylpiperidine (4b).
To a solution of TFA–water (4 mL, 3 : 2) was added 13
(0.39 g, 0.99 mmol) at 0 ◦C, which was then stirred for 30 min.
The solution was allowed to warm to 25 ◦C and stirred for
2.5 h. TFA–water was co-evaporated with toluene under a
high vacuum to provide an anomeric mixture of hemiacetal
(0.304 g, 98%), which was directly used in the next reaction. To
a solution of hemiacetal in dry methanol (7 mL) was added 10%
Pd/C (0.08 g) and ammonium formate (0.489 g, 7.75 mmol).
The reaction mixture was refluxed for 45 min and filtered
through celite, washed with methanol and concentrated. The
concentrated thick liquid was purified by a silica column using
CHCl3–MeOH–NH3 (25% solution) = 50 : 49 : 1 as an eluant to
yield 4b (0.131 g, 83%) as a thick oil. Found: C, 44.22; H, 8.09.
Calc. for C6H13NO4 C, 44.16; H, 8.03; Rf 0.09 (50% MeOH–
CHCl3); [a]D +33.68 (c 0.95, MeOH); mmax (nujol) 3550–3200
(br band) cm−1; dH (300 MHz, D2O) 2.57 (1H, t, J = 12.0 Hz,
H2a), 2.86 (1H, d, J = 13.5 Hz, H6a), 3.06 (1H, dd, J = 13.5
and 1.7 Hz, H6e), 3.24 (1H, ddd, J = 12.0, 4.9 and 1.7 Hz,
H2e), 3.41 (1H, d, J = 9.4 Hz, H4), 3.49 (2H, AB quartet, J =
11.7 Hz, CH2OH), 3.83 (1H, ddd, J = 12.0, 9.4 and 4.9 Hz, H3);
dC (75 MHz, D2O) 47.2, 49.2 (C-2/C-6), 63.0 (CH2OH), 66.4,
72.5, 72.9 (C-3/C-4/C-5).
mixture was stirred at room temperature for 4 h, quenched
with water and extracted with chloroform (3 × 10 mL).
Work-up and chromatography (n-hexane–ethyl acetate = 5 :
1) provided 15 (0.296 g, 89%) as a thick oil. Found: C, 60.49;
H, 6.89. Calc. for C17H23NO6 C, 60.52; H, 6.87; Rf 0.55 (50%
ethyl acetate–n-hexane); [a]D −12.7 (c 1.1, CHCl3); mmax (neat)
3600–3190 (br band) and 1709 cm−1; dH (300 MHz, CDCl3) 1.23
(3H, s, CH3), 1.33 (3H, s, CH3), 1.51 (3H, s, CH3), 3.32–3.56
(2H, m, CH2NH), 4.07 (1H, s, H3), 4.65 (1H, d, J = 4.0 Hz,
H2), 5.14 (2H, br s, O-CH2Ph), 5.30–5.40 (1H, br s, NH/OH,
exchange with D2O), 5.87 (1H, d, J = 4.0 Hz, H1), 7.31–7.40
(5H, m, Ar-H); dC (75 MHz, CDCl3 + D2O) 18.9, 26.2, 26.8
(CH3), 46.3 (N-CH2), 66.9, 87.5, 87.7 (C-2/C-3/C-4), 103.9
(C-1), 112.3 (OCO), 127.9, 128.1, 128.5, 136.3 (Ar-C), 157.1
(CO).
(3S,4R,5S)-3,4,5-Trihydroxy-5-methylpiperidine (4c). To a
solution of TFA–water (4 mL, 3 : 2) was added 15 (0.26 g,
0.77 mmol) at 0 ◦C, which was then stirred for 30 min.
The solution was allowed to warm to 25 ◦C and stirred for
2.5 h. TFA–water was co-evaporated with toluene under a
high vacuum to provide an anomeric mixture of hemiacetal
(0.224 g, 98%), which was directly used in the next reaction.
To a solution of hemiacetal in dry methanol (8 mL) was added
10% Pd/C (0.08 g) and ammonium formate (0.38 g, 6.03 mmol).
The reaction mixture was refluxed for 45 min and filtered
through celite, washed with methanol and concentrated. The
concentrated thick liquid was purified by a silica column using
CHCl3–MeOH–NH3 (25% solution) = 55 : 44 : 1 as an eluant to
yield 4c (0.082 g, 72%) as a thick oil. Found: C, 45.02; H, 8.95.
Calc. for C6H13NO3 C, 48.97; H, 8.90; Rf 0.21 (50% MeOH–
CHCl3); [a]D +10.67 (c 0.75, MeOH); mmax (nujol) = 3540–3100
(br band) cm−1; dH (300 MHz, D2O) 1.33 (3H, s, CH3), 2.85 (1H,
t, J = 11.9 Hz, H2a), 3.10 (1H, d, J = 13.2 Hz, H6a), 3.26 (1H,
dd, J = 13.2 and 1.8 Hz, H6e), 3.42 (1H, d, J = 9.4 Hz, H4),
3.48 (1H, ddd, J = 11.9, 5.3 and 1.8 Hz, H2e), 4.00 (1H, ddd,
J = 5.3, 9.4 and 11.9 Hz, H3); dC (75 MHz, D2O) 21.7 (CH3),
46.7, 52.1 (C-2/C-6), 65.4 (C-5), 69.9, 75.9 (C-3/C-4).
(3S,4R,5R)-3,4,5-Trihydroxy-5-hydroxymethylpiperidine hy-
drochloride (9b). To a stirred solution of compound 4b (0.1 g,
0.613 mmol) in dry methanol was added HCl (0.1 mL) under
nitrogen. The reaction mixture was stirred at 25 ◦C for 2 h
and the solvent was evaporated under reduced pressure to give
9b (0.12 g, 98%) as a semi-solid. Found: C, 36.12; H, 7.15.
Calc. for C6H14NO4Cl C, 36.09; H, 7.07; Rf 0.02 (90% MeOH–
CHCl3); [a]D +18.95 (c 0.95, MeOH); mmax (nujol) 3600–3230 (br
band) cm−1; dH (300 MHz, D2O) 2.71 (1H, t, J = 11.9 Hz, H2a),
3.02 (1H, d, J = 13.2 Hz, H6a), 3.20 (1H, dd, J = 13.2 and
1.7 Hz, H6e), 3.37 (1H, ddd, J = 11.9, 5.2 and 1.7 Hz, H2e),
3.45 (1H, d, J = 9.4 Hz, H4), 3.47 (1H, d, J = 11.7 Hz, CH2OH),
3.56 (1H, d, J = 11.7 Hz, CH2OH), 3.91 (1H, ddd, J = 11.9, 9.4
and 5.2 Hz, H3); dC (75 MHz, D2O) 46.5, 48.9 (C-2/C-6), 62.7
(CH2OH), 65.3, 71.9, 72.4 (C-3/C-4/C-5).
1 7 0 6
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 1 7 0 2 – 1 7 0 7

View Article Online
General procedure for inhibition assay
Glycobiology, 1992, 2, 199; (i) Y. L. Merror, L. Poitout, J. Deepazy, I.
Dosbaa, S. Geoffroy and M. Foglietti, Bioorg. Med. Chem., 1997, 5,
519; (j) A. E. Stuts, Iminosugars as Glycosidase Inhibitors. Nojirimycin
and Beyond, Wiley-VCH, Weinheim, 1999; (k) T. D. Heightman and
A. T. Vasella, Angew. Chem., Int. Ed., 1999, 38, 750; (l) M. Bols,
V. H. Lillelund, H. H. Jensen and X. Liang, Chem. Rev., 2002, 102,
515 and references cited therein; (m) J. Y. Goujon, D. Gueyrard,
C. Philippe, M. R. Olivier and N. Asano, Tetrahedron: Asymmetry,
2003, 14, 1969.
2 (a) W. Dong, T. Jespersen, M. Bols, T. Skrydstrup and M. R. Sierks,
Biochemistry, 1996, 35, 2788; (b) T. M. Jespersen, W. Dong, M. R.
Sierks, T. Skrydstrup, I. Lundt and M. Bols, Angew. Chem., Int. Ed.
Engl., 1994, 33, 1778; (c) T. M. Jespersen and M. Bols, Tetrahedron,
1994, 50, 13449; (d) Y. Ichikawa and Y. Igarashi, Tetrahedron Lett.,
1995, 36, 4585; (e) M. Bols, Acc. Chem. Res., 1998, 31, 1; (f) Y.
Ichikawa, Y. Igarashi, M. Ichikawa and Y. Suhura, J. Am. Chem.
Soc., 1998, 120, 5854; (g) S. J. Willams, R. Hoos and S. G. Withers,
J. Am. Chem. Soc., 2000, 122, 2223; (h) Y. Nishimura, E. Shitara, H.
Adachi, M. Toyoshima, M. Nakajima, Y. Okami and T. Takeuchi,
J. Org. Chem., 2000, 65, 2; (i) G. Pandey, M. Kapur, M. I. Khan and
S. M. Gaikwad, Org. Biomol. Chem., 2003, 1, 3321.
Inhibition potencies of the isofagomine analogues 4a–c were
determined by measuring the residual hydrolytic activities of the
glycosidases. The substrates (purchased from Sigma Chemicals
Co. USA) namely p-nitrophenyl-a-D-glucopyranoside, p-nitro-
phenyl-b-D-glucopyranoside, p-nitrophenyl-b-D-galactopyrano-
side, p-nitrophenyl-a-D-galactopyranoside, of 2 mM concentra-
tion were prepared in a 0.025 M citrate buffer at pH 6.0, p-
nitrophenyl-a-D-mannopyranoside of 2 mM was prepared in
a 0.025 M citrate buffer at pH 4.0. The test compound was
preincubated with the respective enzyme buffered at its optimal
pH, for 1 h at 25 ◦C. The enzyme reaction was initiated
by the addition of 100 lL of substrate. Controls were run
simultaneously in the absence of a test compound. The reaction
was terminated at the end of 10 min by the addition of a
0.05 M borate buffer (pH 9.8) and absorbance of the liberated
p-nitrophenol was measured at 405 nm using a Shimadzu
Spectrophotometer UV-1601. One unit of glycosidase activity is
defined as the amount of enzyme that hydrolyzed 1 lmole of p-
nitrophenyl pyranoside per minute at 25 ◦C.9 Inhibitory potency
of the compounds against human salivary amylase (HSA) was
estimated using soluble starch as a substrate.10
3 M. Ichikawa, Y. Igarashi and Y. Ichikawa, Tetrahedron Lett., 1995,
36, 1767. The isofagomine analogues 3b and 4b are enantiomers. The
1H and 13C NMR of the hydrochloride salt of 3b is in consonance
with 9b (the hydrochloride salt of 4b). The authors have not reported
the specific rotation for 3b·HCl.
4 (a) D. D. Dhavale, S. D. Markad, N. S. Karanjule and J.
PrkashaReddy, J. Org. Chem., 2004, 69, 4760; (b) N. T. Patil, J. N.
Tilekar and D. D. Dhavale, J. Org. Chem., 2001, 66, 1065 and
references cited therein; (c) N. T. Patil, S. John, S. G. Sabharwal
and D. D. Dhavale, Bioorg. Med. Chem., 2002, 10, 2155; (d) D. D.
Dhavale, M. M. Matin, T. Sharma and S. G. Sabharwal, Bioorg.
Med. Chem., 2003, 11, 3295; (e) D. D. Dhavale and M. M. Matin,
Tetrahedron, 2004, 60, 4275; (f) D. D. Dhavale, M. M. Matin, T.
Sharma and S. G. Sabharwal, Bioorg. Med. Chem., 2004, 12, 4039.
5 We are thankful to Dr Ganesh Pandey for providing the spectral data
of 3c, which is different from that of compound 4b.
Acknowledgements
We thank the Department of Science and Technology
(SP/S1/G-32/2000), New Delhi for financial support. MMM
is grateful to the Indian Council for Cultural Relations (ICCR),
New Delhi for a fellowship. The support of the University Grants
Commission under CAS phase I (New Delhi) to procure a High
Field NMR facility is gratefully acknowledged.
6 An alternative explanation for this selectivity is the intramolecular
hydrogen bonding of the C-3 oxygen atom with the hydrogen atom of
the C-4b CH2OH group, which makes this hydroxymethylene oxygen
more nucleophilic for tosylation. We are grateful to one of the referees
for this suggestion.
7 Mikael Bols and co-workers have reported that polyhydroxylated
piperidines change their conformation with respect to hydrogen ion
concentration, see: H. H. Jensen, L. Lyngbye, A. Jensen and M. Bols,
Chem. Eur. J., 2002, 8, 1218.
8 (a) D. L. Zechel and S. G. Withers, Acc. Chem. Res., 2000, 33, 11;
(b) T. D. Heightman and A. T. Vasella, Angew. Chem., Int. Ed., 1999,
38, 750; (c) T. M. Jespersen, W. Dong, M. R. Sierks, T. Skrydstrup,
I. Lundt and M. Bols, Angew. Chem., Int. Ed. Engl., 1994, 33, 1778.
9 L. Yu-The and L. Suc-Chen, in Methods in Enzymology, ed. Victor
Ginsberg, Academic Press, 1972, vol. 28, part B, 702.
References
1 (a) T. Kajimoto, K. K. C. Liu, R. L. Pederson, Z. Zhong Jr., Y.
Ichikawa, J. A. Porco and C. H. Wong, J. Am. Chem. Soc., 1991, 113,
6187; (b) Y. Xu and W. Zhou, J. Chem. Soc., Perkin Trans. 1, 1997,
1, 741; (c) N. Asano, A. Kato, M. Miyauchi, H. Kizu, Y. Kameda,
A. A. Watson, R. J. Nash and G. W. J. Fleet, J. Nat. Prod., 1998, 61,
625; (d) M. Bols, V. H. Lillelund, H. H. Jensen and X. Liang, Chem.
Rev., 2002, 102, 515; (e) A. D. Elbein, Annu. Rev. Biochem., 1987, 56,
497; (f) A. Karpas, G. W. J. Fleet, R. A. Dwek, S. Petursson, S. K.
Namgoong, N. G. Ramsden, G. S. Jacob and T. W. Rademacher, Proc.
Natl. Acad. Sci. USA, 1988, 85, 9229; A. Karpas, G. W. J. Fleet, R. A.
Dwek, S. Petursson, S. K. Namgoong, N. G. Ramsden, G. S. Jacob
and T. W. Rademacher, FEBS Lett., 1988, 237, 128; (g) G. W. J.
Fleet, Chem. Br., 1989, 287; (h) B. Winchester and G. W. J. Fleet,
10 G. L. Miller, Anal. Chem., 1972, 31, 426.
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 1 7 0 2 – 1 7 0 7
1 7 0 7