N-hydroxyethyl-piperidine and -pyrrolidine homoazasugars: Preparation and evaluation of glycosidase inhibitory activity

Article abstract of DOI:10.1016/S0968-0896(03)00231-1

An efficient and practical strategy for the synthesis of N-hydroxyethyl-1-deoxy-homonojirimycins 4 and 5 and N-hydroxyethyl-pyrrolidine homoazasugars 6 and 7 with full stereocontrol is being reported. The key step involved is the intermolecular Michael ad

Full text of DOI:10.1016/S0968-0896(03)00231-1

Bioorganic & Medicinal Chemistry 11 (2003) 3295–3305
N-Hydroxyethyl-piperidine and -Pyrrolidine Homoazasugars:
Preparation and Evaluation of Glycosidase Inhibitory Activity
Dilip D. Dhavale,a,* Mohammed M. Matin,a Tarun Sharmab and Sushma G. Sabharwalb
aDepartment of Chemistry, Garware Research Centre, University of Pune, Pune-411 007, India
bDepartment of Chemistry, Division of Biochemistry, University of Pune, Pune-411 007, India
Received 14 March 2003; revised 4 April 2003; accepted 7 April 2003
Abstract—An efficient and practical strategy for the synthesis of N-hydroxyethyl-1-deoxy-homonojirimycins 4 and 5 and N-
hydroxyethyl-pyrrolidine homoazasugars 6 and 7 with full stereocontrol is being reported. The key step involved is the inter-
molecular Michael addition of benzylamine to d-glucose derived a,b-unsaturated ester 8 followed by N-alkylation with ethyl bromo-
acetate. Reduction with LAH, acetylation, hydrogenation and protection with -Cbz group afforded compounds 14a and 14b.
Removal of 1,2-acetonide functionality, hydrogenation and deacetylation afforded N-hydroxyethyl-d-gluco-1-deoxyhomonojir-
imycin (4) and N-hydroxyethyl-l-ido-1-deoxyhomonojirimycin (5), respectively. Compounds 14a and 14b on acetylation followed
by removal of 1,2-acetonide functionality, sodium metaperiodate oxidation, hydrogenation and deacetylation gave 1,4,5-trideoxy-
1,4-imino-N-hydroxyethyl-d-arabino-hexitol (6) and 1,4,5-trideoxy-1,4-imino-N-hydroxyethyl-l-xylo-hexitol (7), respectively. The
glycosidase inhibition activity of compounds 4, 5, 6, 7, 16a and 16b was evaluated using sweet almond seed as a rich source of
different glycosidases.
# 2003Elsevier Science Ltd. All rights reserved.
Introduction
against hepatitis B virus (HBV).10 In cell culture, N-
alkylated derivatives are also more effective inhibitors
of glucosidase I than is the parent compound 1a.11
More therapeutic applications of N-alkylated DNJ
are being uncovered. For example, N-butyl-1-deoxy-
The discovery of polyhydroxylated piperidine1 and
pyrrolidine2 alkaloids such as nojirimycin 1, 1-deoxy-
nojirimycin (DNJ) 1a and 2,5-dihydroxymethyl-3,4-
dihydroxy-pyrrolidine (DMDP) 3 (Fig. 1) manifests
the spectacular development of azasugars (or imino-
sugars) and has opened a dynamic research field at the
interface between glycobiology and organic chemistry
due to their action as glycosidases inhibitors. In recent
years, the scope of biological activities has been extended
to the inhibition of glycosyltransferases,3 of glycogen3
and nucleoside4 phosphorylases and of sugar nucleotide
mutase (UDP-Galp mutase).5 These properties led to a
new generation of azasugar-based medicines in a wide
range of diseases such as viral infections,6 diabetes,7 and
tumor metastasis.8 In this respect, N-alkylated aza-
sugars were demonstrated to be stronger glycosidase
inhibitors than the corresponding non-alkylated deriva-
tives.9 For example, N-alkylation of DNJ induces a shift
in specific inhibition of purified glucosidases from a-
glucosidase II to a-glucosidase I and may be useful
*Corresponding author. Tel.: +91-20-560-1225x583; fax: +91-20-
569-1728; e-mail: ddd@chem.unipune.ernet.in
Figure 1.
0968-0896/03/$ - see front matter # 2003Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0968-0896(03)00231-1

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D. D. Dhavale et al. / Bioorg. Med. Chem. 11 (2003) 3295–3305
nojirimycin 2 (Fig. 1) was identified as the most
active anti-HIV agent without significant cytotoxi-
city12 and also active against Gaucher disease, a
severe lysosomal storage disorder.13 Amongst N-alky-
lated derivatives, N-hydroxyethyl-1-deoxynojirimycin
was found to be a potent sucrase inhibitor.14 In gen-
eral, the synthetic routes to N-alkylated derivatives
make use of azasugar itself as a substrate and
reductive amination with a suitable alkyl aldehyde
using sodium cyanoborohydride or catalytic hydro-
genation or sodium bicarbonate in methanol-di-
oxane.9,15 In view of the high potential of N-alkylated
azasugars and as a part of our continuing interest
in the synthesis of azasugars,16 we report herein a
practical approach for the synthesis of hitherto
unknown N-hydroxyethyl-d-gluco-1-deoxyhomonojir-
imycin (4), N-hydroxyethyl-l-ido-1-deoxy-homono-
jirimycin (5) and pyrrolidine alkaloids such as 1,4,5-
trideoxy-1,4-imino-N-hydroxyethyl-d-arabino-hexitol (6)
prochiral C-5 centre was achieved by the reaction of
lithium N-benzylamide with a mixture (E+Z) of 8 in
THF at ꢁ40 ꢀC for 2 h, which afforded 9b (l-ido) as the
only isolable diastereomer in 85% yield.17 Having both
the sugar b-amino esters in hand, we have attempted the
N-alkylation with ethyl bromoacetate using different
bases like NaH, KOtBu, pyridine under a variety of
reaction conditions. However, better result was
obtained by the reaction of 9a with ethyl bromoacetate,
in the presence of potassium carbonate in DMF at
room temperature for 30 h, to give 10a in 71% yield
(Scheme 1). Reduction of both the carbethoxy groups in
10a by LAH gave the b-amino alcohol 11a, which on
acetylation afforded the diacetate 12a in good yield.
Removal of N- and O-benzyl groups in 12a by hydro-
genolysis (10% Pd/C, methanol) gave 13a, that on
selective N-benzyloxycarbonyl protection gave the
N-Cbz derivative 14a.18,19 Opening of the 1,2-O-iso-
propylidene functionality in 14a with TFA-water gave
hemiacetal which was directly treated with 10% Pd/C
and ammonium formate in methanol under reflux to
afford diacetate 15a, wherein removal of N-Cbz group
produce primary amine that concomitantly undergoes
cyclic imine formation and gets reduced to afford
piperidine ring skeleton. Deacetylation of 15a with
sodium methoxide in methanol at 0 ꢀC afforded the N-
and
1,4,5-trideoxy-1,4-imino-N-hydroxyethyl-l-xylo-
hexitol (7).
Results and Discussion
Synthesis of N-hydroxyethyl-D-gluco-1-deoxyhomonojiri-
mycin 4 and N-hydroxyethyl-L-ido-1-deoxyhomonojiri-
mycin 5
hydroxyethyl-d-gluco-1-deoxyhomonojirimycin
4.
Compound 4 on reaction with acetic anhydride in pyri-
dine at room temperature gave pentaacetate derivative
16a. The 1H and 13C NMR data was in accordance with
the structures 4 and 16a.
d-Glucose was converted to a geometrical mixture (E
and Z) of a,b-unsaturated esters 8a and 8b, respectively,
by our earlier procedure.16c,d The conjugate addition of
N-benzylamine with 8 at 25 ꢀC afforded a diastereo-
meric mixture of b-amino esters 9a (d-gluco) and 9b (l-
ido) in the ratio 3:7. The stereocontrolled formation of
The same sequence of reactions was repeated with 9b
and compounds 10b, 11b, 12b, 13b and 14b were iso-
lated in good yield. Treatment of 14b with TFA–water
Scheme 1. Reagents and conditions: (i) BnNH2, rt 20 h; (ii) BrCH2COOEt, K2CO3, DMF, rt, 24–30 h; (iii) LAH, THF, 0 ꢀC, 2 h; (iv) Ac2O, Py, 0–
25 ꢀC, 40 h; (v) 10% Pd/C, H2, 80 psi, MeOH, 12 h; (vi) CbzCl, NaHCO3, EtOH–H2O (8:2), 0 ꢀC–rt, 4 h; (vii) TFA–H2O (3:2), 0–30 ꢀC, 3h; (viii)
10% Pd/C, HCOONH4, MeOH, reflux, 45 min; (xi) NaOMe, MeOH, 0–30 ꢀC, 2 h; (x) Ac2O, Py, 0–30 ꢀC, 12 h.

D. D. Dhavale et al. / Bioorg. Med. Chem. 11 (2003) 3295–3305
3297
and hydrogenation with 10% Pd/C, ammonium for-
Conformational assignment of 4 and 5
mate gave diacetate 15b which on deacetylation affor-
ded the N-hydroxyethyl-l-ido-1-deoxyhomonojirimycin
5. The structure 5 was confirmed by converting it into
pentaacetate derivative 16b, which was characterized by
spectral and analytical methods.
Nojirimycin 1 and 1-deoxynojirimycin 1a are known to
4
exist in C1 conformation. However, in case of com-
pounds 4 and 5 the presence of –CH2CH2OH groups,
on adjacent atoms, increases the bulk in the molecule.
Therefore, it was thought to derive the conformations of
4 and 5 using 1H NMR spectral data. The coupling
constants determined from the 300 MHz 1H NMR
spectra and decoupling experiments in D2O of 4 and 5
are shown in Table 1. In case of 4, appearance of two
distinct doublet of doublets for 1-Ha at d 2.20
(J1a,1e=11.8 and J1a,2=9.7 Hz) and for 1-He at d 2.94
(J1e,1a=11.8 and J1e,2=4.4 Hz) were informative. The
large coupling constant (J1a,2=9.7 Hz) for the 1-H axial
proton requires trans-diaxial relationship with 2-H pro-
ton. This clearly requires 2-H proton to be axial. In one
step earlier compound 14a, the relative stereochemistry
of the substituents at C-2, C-3and C-3, C-4 is trans and
the same stereochemistry is retained in the product for-
mation. In addition, the trans diaxial disposition of 4-H
and 5-H protons was evident from the larger coupling
constant (J4,5=9.2 Hz). This confirms that compound 4
exists in 4C1 conformation with C-5 substituent
(ꢁCH2CH2OH) equatorially oriented [(5R) configuration].
Synthesis of 1,4,5-trideoxy-1,4-imino-N-hydroxyethyl-D-
arabino-hexitol (6) and 1,4,5-trideoxy-1,4-imino-N-hydro-
xyethyl-L-xylo-hexitol (7)
The compounds 14a and 14b were found to be promis-
ing intermediates for the synthesis of five member pyr-
rolidine homoazasugars 6 and 7. Thus, acetylation of 3-
OH in 14a with acetic anhydride in pyridine afforded
triacetate 17a as semi solid in 94% yield (Scheme 2).
Deprotection of the acetonide functionality in 17a with
TFA-water followed by sodium metaperiodate oxida-
tion gave amino-aldehyde (with one carbon atom less),
which was directly subjected to hydrogenation with
10% Pd/C and ammonium formate in methanol to give
triacetylated pyrrolidine derivative 18a. Deacetylation
of 18a with sodium methoxide in methanol afforded
1,4,5-trideoxy-1,4-imino-N-hydroxyethyl-d-arabino-
hexitol (6). Similarly, 14b on acetylation gave the tri-
acetate 17b, which on treatment with TFA-water,
sodium metaperiodate and hydrogenation yielded pyr-
rolidine derivative 18b. Deacetylation of 18b with
sodium methoxide in methanol gave 1,4,5-trideoxy-1,4-
imino-N-hydroxyethyl-l-xylo-hexitol (7). The struc-
tures 6 and 7 were confirmed by converting them into
tetraacetate derivatives 19a and 19b, respectively,
which were characterized by spectral and analytical
methods.
Since the 1H NMR spectrum of 5 is very different from 4,
it was thought that 5 could exist in different conformation.
However, the appearance of one triplet at d 3.24 for 3-H
with large coupling constants (J3,4=J2,3=9.1 Hz) indi-
cated trans-diaxial relationship with adjacent protons. In
addition, 1-Ha appeared as doublet of doublet at d 2.34
(J1a,1e=12.2 and J1a,2=9.9 Hz), wherein the large cou-
pling constant J1a,2=9.9 Hz requires trans-diaxial rela-
tion with 2-H proton. This is clear indicative of the fact
4
that compound 5 exist in C1 conformation. The small
coupling constant between 4-H and 5-H (J4,5=4.9 Hz)
clearly requires 5-H proton to be equatorial and sug-
gestive of the fact that –CH2CH2OH substituent at C-5
is axial with (5S) configuration.
In case of N-butyl-1-deoxynojirimycin (2) various rota-
mer populations about C-5–C-6 bond were pro-
posed,9a,b,20 which were estimated by the J5,6a and J5,6b
coupling constants. In compounds 4 and 5, where
hydroxyethyl group is present instead of hydroxymethyl
group at the C-5 position, the coupling constants
J5,6a=J5,6b=ꢂ2.6 Hz suggest a large population of the
gauche–gauche rotamer for 4 as shown in Figure 2. This
could be explained on the basis of possible hydrogen
bonding between –OH of –CH2CH2OH at C-5 and the
ring nitrogen atom (the basicity of nitrogen is increased
due to the presence of alkyl chain). Formation of such
hydrogen bonding requires the 6-Ha and 6-Hb to be
gauche to 5-H resulting in low J (ꢂ2.6 Hz) value with
both of these hydrogens. On the other hand, in com-
pound 5, one of the staggered conformers about the C-
5–C-6 bond is destabilized due to the large steric inter-
actions of ꢁCH2CH2OH (at C-5) with axial hydrogen at
C-1 and C-3(ring protons). Hence, the two other stag-
gered conformations about this bond would result in
one hydrogen (6-Ha) being anti and other (6-Hb) gauche
to C-5 hydrogen. The rotation around C-5–C-6 would
Scheme 2. Reagents and conditions: (i) Ac2O, Py, 0–25 ꢀC, 3h; (ii)
TFA–H2O (3:2), 30 ꢀC, 3h; (iii) NalO 4, acetone–H2O, 0 ꢀC–rt, 3h; (iv)
10% Pd/C, HCOONH4, MeOH, reflux, 45 min; (v) NaOMe, MeOH,
0–30 ꢀC, 1.5 h; (vi) Ac2O, Py, 0–30 ꢀC, 12 h.

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D. D. Dhavale et al. / Bioorg. Med. Chem. 11 (2003) 3295–3305
Table 1. Coupling constants for N-hydroxyethyl-1-deoxy-homonojirimycin derivatives 4, 16a, 5, 16b and N-hydroxyethyl-pyrrolidine analogues 6,
19a, 7 and 19b
Compd
Coupling constants (Hz)
0 0
J1 aa,1 ab
0 0
J1 aa,2 a
0 0
J1 ab,2 a
J1a,1b
J1a,2
J1b,2
J2,3
J3,4
J4,5a
J4,5b
J4,5
J5,6a
J5,6b
4
16a
5
16b
6
19a
7
11.8
9.7a
10.0a
9.9
4.4
4
5.2
5.5
9.2a
2.8a
2.8a
13.5
14
5.7
5.35.7
6.6
12.6
9.5
9.1
9.6
9.5
9.1
12.2a
13.2
4.9a
5.5
6.1a
6.1a
12.4a
10.7
10.2
7.1a
7.1
8.2a
12.1
a
11.36.35.5
11.35.31.5
11
1.5 .0
1.8
3
13.2
13.2
5.3
5.7
a
5.39
5.1
5.5
9
12.6
5.7
6.8
5.2
5.2
6.1
6.6
2.5
2.5
5
8
6.6
19b
11
aThis value was determined by decoupling experiments.
Table 2. Concentration of N-hydroxyethyl-1-deoxyhomonojirimycin
and N-hydroxyethyl-pyrrolidine derivatives (mM) giving 50% inhibi-
tion of glycosidases
Compd
IC50 (mM)
b-
b-
a-
Glucosidase Galactosidase Galactosidase Mannosidase
a-
4
5
16a
16b
6
4.25
2.11
NI
2.32
NI
9.04
1.29
NI
6.96
23.5
3.40
NI
NI
NI
NI
3.27
3.11
NI
3.52
NI
NI
6.54
4.20
Figure 2.
7
NI
lead to 6-Ha gauche and 6-Hb anti. These two staggered
conformational rotamers will be in equilibrium and
would result in increased coupling constants for these
hydrogens (6-Ha and 6-Hb) with C-5 hydrogen which
was indeed observed (J5,6a=J5,6b=6.1 Hz). In the case
of pyrrolidine analogues, the magnitude of the vicinal
coupling constants within the five membered ring of
d-arabino-hexitol 6 was considerably different from that
of l-xylo-hexitol (7) (Table 1). In particular, 1-Ha, 1-Hb,
3-H and 4-H signals of 6 significantly differed from those
of the l-xylo-hexitol 7. However, as in another furanose
analogue DMDP (3), it is impossible to obtain conforma-
tional information from NMR experiments.
NI, inhibition not observed under assay condition.
All above values are an average obtained from three sets of assay
performed.
them more potent against b-glycosidases as compared
to a-glycosidases. Comparison of IC50 values between 4
and 5 suggests that the replacement of C-5 position with
a-oriented –CH2CH2OH functionality in 5 resulted in
increased potency towards b-galactosidases. Inhibitory
effectiveness of both azasugars (4 and 5) is more than
that of their pentaacetate forms (16a and 16b). The N-
hydroxyethyl pyrrolidine 6 and 7 were found to be
moderate to weak glycosidase inhibitors.
Biological Activity
Conclusion
Glycosidases particularly b-glucosidase (E.C. 3.2.1.21),
a-galactosidase (E.C 3.2.1.22), b-galactosidase (E.C.
3.2.1.23) and a-mannosidase (E.C. 3.2.1.24) are abun-
dantly present in sweet almonds. Therefore inhibitory
potency of homoazasugars 4, 5, 6, 7, 16a and 16b was
evaluated using glycosidases extracted from sweet
almonds. The IC50 values obtained for the above men-
tioned compounds are summarized in Table 2.
In summary, the synthetic strategy based on the 1,4-
Michael addition of benzylamine to sugar derived a,b-
unsaturated ester 8 followed by N-alkylation provides
an efficient, practical and general access to N-(hydroxy-
ethyl)-d-gluco- and l-ido-homo-DNJ 4 and 5. The
reaction sequence could be extended for the synthesis of
different N-alkylated five- and six-member azasugar
analogues by changing the alkylating agent. The same
strategy was successfully utilized for the synthesis of
N-hydroxyethyl-pyrrolidine homoazasugrs 6 and 7. We
have also demonstrated that the homoazasugars 4 and 5
exist in 4C1 conformation in aqueous medium, although
in 5 the bulky –CH2CH2OH group at C-5 is axially
oriented. The glycosidase inhibitory potency (IC50) of
homoazasugars 4, 5, 6, 7, 16a and 16b was evaluated
and this showed that the presence of a-oriented
ꢁCH2CH2OH functionality at C-5 in 5 and 16b or C-4
in 7, has significant effect on the glycosidase inhibition
1-Deoxynojirimycin (1a) is reported to be a potent
inhibitor of all types of mammalian a-glucosidases and
is also a moderate to weak inhibitor of b-glucosidase,
b-galactosidase and a-mannosidase.1d From the IC50
obtained for N-hydroxyethyl compounds 4 and 5, it can
be observed that they are potent b-galactosidase, b-glu-
cosidase and a-mannosidase inhibitors, but do not
inhibit a-galactosidase. Thus, the introduction of
N-hydroxyethyl and C-5 hydroxyethyl functionality
(instead of C-5 hydroxymethyl group as in 1a) makes

D. D. Dhavale et al. / Bioorg. Med. Chem. 11 (2003) 3295–3305
3299
than that of the corresponding C-5 epimers or C-4 epi-
mers, respectively.
for 30 h, decomposed with cooled water (2 cm3) and
extracted with chloroform (10 cm3ꢃ3). Work-up fol-
lowed by chromatography (n-hexane/ethyl acetate=96/
4) gave 10a (0.38 g, 71%) as a thick syrup (Found: C,
66.75; H, 7.36. C30H39NO8 requires C, 66.53; H,
7.26%); Rf=0.64 (n-hexane/ethyl acetate=4/1); [a]D
ꢁ26.67 (c 0.15 in CHCl3); nmax (neat)/cmꢁ1 1754; dH
(300 MHz, CDCl3) 1.17 (3H, t, J=7.0, CH3), 1.24 (3H,
t, J=7.0, CH3), 1.30 (3H, s, CH3), 1.45 (3H, s, CH3),
2.67–2.82 (2H, m, 6-Ha and Hb), 3.36 (2H, AB quartet,
J=17.3, N-CH2CO), 3.81–4.28 (9H, m, 3-H, 4-H, 5-H,
N-CH2Ph, 2 O-CH2CH3), 4.51 (1H, d, J=11.7, O-
CH2Ph), 4.54 (1H, d, J=3.8, 2-H), 4.64 (1H, d, J=11.7,
O-CH2Ph), 5.84 (1H, d, J=3.8, 1-H), 7.12–7.29 (10H,
m, Ar-H); dC (75 MHz, CDCl3) 14.0, 14.1, 26.2, 26.6
(CH3), 34.5 (C-6), 52.6, 54.9 (N-CH2Ph/N-CH2CO),
57.9 (C-5), 60.0, 67.9 (O-CH2), 71.4 (O-CH2Ph), 79.9,
81.5, 82.4 (C-2/C-3/C-4), 104.6 (c-1), 111.1 (O-C-O),
126.8, 127.3, 127.5, 127.9, 128.1, 128.6, 137.2, 138.7 (Ar-
C), 171.8, 172.5 (CO).
Experimental
Melting points were recorded with Thomas Hoover
melting point apparatus and are uncorrected. IR spectra
were recorded with FTIR as a thin film or in Nujol mull
.
or using KBr pellets and are expressed in cmꢁ1 1H
(300 MHz) and 13C (75 MHz) NMR spectra were
recorded 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 C,H-ana-
lyzer. Optical rotations were measured using polari-
meter at 25 ꢀC. Thin-layer chromatography was
performed on pre-coated plates (0.25 mm, silica gel 60
F254). Column chromatography was carried out with
silica gel (100–200 mesh). Resin column was performed
with Dowex IR resin (H+ form, 100–200 mesh, 50ꢃ8)
with ammonia solution (25%, Merck). The reactions
were carried out in oven-dried glassware under dry N2.
N-Benzylamine, methanol, DMF, THF were purified and
dried before use. Petroleum ether (PE) that was used is a
distillation fraction between 40 and 60 ꢀC. N-Benzylamine,
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 combined organic
layer with water, brine, drying over anhydrous sodium
sulfate and evaporation of solvent at reduced pressure.
Compounds 9a and 9b were prepared by the inter-
molecular Michael addition of benzyl amine to a,b-unsat-
urated ester 8 as per our earlier reported procedure.16d,f
Ethyl 1,2-O-isopropylidene-3-O-benzyl-5-(N-benzyl, N-
carbethoxymethylene)amino-5,6-dideoxy-ꢁ-L-ido-hepto-
furanuronate (10b). The reaction of 9b (0.67 g, 1.47
mmol), anhydrous potassium carbonate (1.0 g, 7.30
mmol) and ethyl bromoacetate (0.30 g, 1.80 mmol) in
dry DMF (10 cm3) as stated for 9a after 20 h and col-
umn chromatographic purification (n-hexane/ethyl ace-
tate=94/6) yielded compound 10b (0.74 g, 93%) as a
thick syrup (Found: C, 66.71; H, 7.34. C30H39NO8
requires C, 66.53; H, 7.26%); Rf=0.49 (n-hexane/ethyl
acetate=4/1); [a]D ꢁ3.6 (c 0.25 in CHCl3); nmax (neat)/
cmꢁ1 1745 and 1734; dH (300 MHz, CDCl3) 1.16 (3H, t,
J=7.1, CH3), 1.23(3H, t, J=7.1, CH3), 1.35 (3H, s,
CH3), 1.52 (3H, s, CH3), 2.08 (1H, dd, J=3.5 and 14.2,
6-Ha), 2.36 (1H, dd, J=10.7 and 14.2, 6-Hb), 3.37 (1H,
d, J=16.8, N-CH2Ph), 3.54 (1H, d, J=16.8, N-CH2Ph),
3.77 (1H, d, J=3.3, 3-H), 3.84 (1H, ddd, J=3.1, 3.5 and
10.7, 5-H), 3.86 (1H, d, J=13.8, N-CH2CO), 3.99 (2H,
q, J=7.1, CH2CH3), 4.00–4.24 (3H, m, N-CH2CO,
CH2CH3), 4.29 (1H, dd, J=3.1 and 9.9, 4-H), 4.42 (1H,
d, J=11.8, O-CH2Ph), 4.64 (1H, d, J=3.9, 2-H), 4.70
(1H, d, J=11.8, O-CH2Ph), 5.98 (1H, d, J=3.9, 1-H),
7.18–7.42 (10H, m, Ar-H); dC (75 MHz, CDCl3) 14.0,
14.1, 26.2, 26.7 (CH3), 35.9 (C-6), 53.3, 55.2 (N-CH2CO/
N-CH2Ph), 57.7 (C-5), 59.9, 60.3( O-CH2CH3), 71.3( O-
CH2Ph), 80.6, 81.2, 81.7 (C-2/C-3/C-4), 104.8 (C-1),
111.4 (O-C-O), 126.7, 127.8, 127.9, 128.0, 128.3, 129.1,
136.8, 139.5 (Ar-C), 171.1, 172.0 (CO).
Assay method
The substrates p-nitrophenyl-b-d-glucopyranoside,
p-nitrophenyl-b-d-galactopyranoside, p-nitrophenyl-a-
d-galactopyranoside and p-nitrophenyl-a-d-mannopyr-
anoside of 2 mM concentration were prepared in
0.025 M citrate buffer with pH 4.0. An aliquot of 200 mL
of test compound (5 mg/mL solution in distilled water)
was preincubated with the enzyme (almond seed
extract) for 1 h at 37 ꢀC. The enzyme reaction was initi-
ated by the addition of 100 mL substrate. Controls were
run simultaneously in absence of test compound. The
reaction was terminated at the end of 1.5 h by the addition
of 0.05M borate buffer (pH 9.8) and absorbance of the
liberated p-nitrophenol was measured at 420 nm. One unit
of glycosidase activity is defined as the amount of enzyme
that hydrolyzed 1 mmol of p-nitrophenyl pyranoside per
min at 25ꢀC.21 IC50 is the amount of inhibitor in mM
concentration required to decrease enzyme activity by
50% under assay conditions.
1,2-O-Isopropylidene-3-O-benzyl-5-(N-benzyl, N-hydroxy-
ethyl)amino-5,6-dideoxy-ꢀ-D-gluco-heptofuranose (11a).
To an ice cooled suspension of LAH (0.35 g, 9.23 mmol)
in dry THF (8 cm3) was added a solution of 10a (1.0 g,
1.85 mmol) in dry THF (7 cm3) over a period of 10 min.
The reaction mixture was warmed to room temperature
and stirred for 2 h. Ethyl acetate (10 cm3) was added at
0 ꢀC, stirred for 10 min and quenched with saturated
solution of NH4Cl (2 cm3). The solution was filtered,
Ethyl 1,2-O-isopropylidene-3-O-benzyl-5-(N-benzyl, N-
carbethoxymethylene)amino-5,6-dideoxy-ꢀ-D-gluco-hep-
tofuranuronate (10a). To a stirred solution of 9a (0.45
g, 0.98 mmol) and anhydrous potassium carbonate (0.68
3
the residue washed with ethyl acetate (3cm ꢃ3) and
3
g, 4.07 mmol) in dry DMF (3cm ) was added ethyl
bromoacetate (0.27 g, 1.62 mmol) in dry DMF (1 cm3).
The reaction mixture was stirred at room temperature
worked-up. The organic layer was evaporated and puri-
fied by column chromatography (n-hexane/ethyl ace-
tate=3/2) to give 11a (0.69 g, 82%) as a thick liquid

3300
D. D. Dhavale et al. / Bioorg. Med. Chem. 11 (2003) 3295–3305
(Found: C, 68.44; H, 7.88. C26H35NO6 requires C,
68.25; H, 7.71%); Rf=0.30 (n-hexane/ethyl ace-
tate=2/3); [a]D ꢁ20 (c 0.2 in CHCl3); nmax (nujol)/
(2H, m, CH2OAc), 4.10–4.30 (2H, m, CH2OAc), 4.40
(1H, d, J=11.8, O-CH2Ph), 4.54 (1H, d, J=3.8, 2-H),
4.60 (1H, d, J=11.8, O-CH2Ph), 5.87 (1H, d, J=3.8, 1-
H), 7.19–7.28 (10H, m, Ar-H); dC (75 MHz, CDCl3) 20.9,
21.0, 26.3, 26.9 (CH3), 27.3(C-6), 49.0 ( N-CH2CH2), 54.3
(N-CH2Ph), 55.8 (C-5), 62.7, 62.8 (CH2OAc), 71.4 (O-
CH2Ph), 78.8, 81.5, 83.0 (C-2/C-3/C-4), 104.7 (C-1),
111.3(O- C-O), 126.9, 127.3, 127.7, 128.1, 128.3, 128.6,
137.2, 139.5 (Ar-C), 170.7, 170.9 (CO).
cmꢁ1
3450–3100
(br
band);
dH
(300 MHz,
CDCl3+D2O) 1.32 (3H, s, CH3), 1.49 (3H, s, CH3),
1.49–2.10 (2H, m, 6-Ha and Hb), 2.51–2.60 (1H, m,
N-CH2CH2), 2.83–2.94 (1H, m, N-CH2CH2), 3.34
(1H, dt, J=4.4 and 8.8, 5-H), 3.40–3.60 (3H, m,
CH2OH and N-CH2Ph), 3.60–3.68 (1H, m, CH2OH),
3.71–3.80 (1H, m, CH2OH), 3.84 (1H, d, J=13.8, N-
CH2Ph), 3.89 (1H, d, J=3.5, 3-H), 4.32 (1H, dd,
J=3.5 and 4.4, 4-H), 4.41 (1H, d, J=11.8, O-CH2Ph)
4.58 (1H, d, J=3.8, 2-H), 4.63 (1H, d, J=11.8, O-
CH2Ph), 5.89 (1H, d, J=3.8, 1-H), 7.20–7.34 (10H, m,
Ar-H); dC (75 MHz, CDCl3) 26.3, 26.9 (CH3), 30.0 (C-
6), 52.3( N-CH2CH2), 55.3( N-CH2Ph), 57.0 (C-5),
59.9, 62.2 (CH2OH), 71.6 (O-CH2Ph), 76.6, 81.4, 83.4
(C-2/C-3/C-4), 104.5 (C-1), 111.4 (O-C-O), 127.1,
127.6, 127.9, 128.3, 128.4, 128.8, 136.9, 138.8 (Ar-C).
1,2-O-Isopropylidene-3-O-benzyl-5-(N-ꢁ-acetoxyethyl,
N-benzyl)amino-7-O-acetyl-5,6-dideoxy-ꢁ-L-ido-hepto-
furanose (12b). Acetylation of diol 11b (0.21 g, 0.46
mmol) with acetic anhydride (0.84 g, 8.28 mmol) in dry
pyridine (1 cm3) at 0 ꢀC to room temperature for 4 h, as
stated for 11a, gave diacetate 12b (0.21 g, 82%) as syrup
(Found: C, 66.71; H, 7.34. C30H39NO8 requires C,
66.53; H, 7.26%); Rf=0.50 (n-hexane/ethyl acetate=2/
1); [a]D ꢁ66.67 (c 0.33 in CHCl3); nmax (neat)/cmꢁ1
1736; dH (300 MHz, CDCl3) (1.24–1.54 (2H, m, 6-Ha
and Hb), 1.35 (3H, s, CH3), 1.52 (3H, s, CH3), 1.83(3H,
s, CH3), 1.98 (3H, s, CH3), 2.82–2.92 (1H, m, N-
CH2CH2), 3.01 (1H, dt, J=4.6 and 14.0, N-CH2CH2),
3.35 (1H, ddd, J=3.0, 10.2 and 11.3, 5-H), 3.97 (1H, d,
J=3.0, 3-H), 3.85 (2H, AB quartet, J=13.5, N-CH2Ph),
3.92–4.08 (2H, m, CH2OAc), 4.12–4.23(2H, m,
CH2OAc), 4.27 (1H, dd, J=3.0 and 10.2, 4-H), 4.43
(1H, d, J=11.5, O-CH2Ph), 4.62 (1H, d, J=3.8, 2-H),
4.67 (1H, d, J=11.5, O-CH2Ph), 5.99 (1H, d, J=3.8, 1-
H), 7.21–7.34 (10H, m, Ar-H); dC (75 MHz, CDCl3)
20.7, 20.8, 26.2, 26.9 (CH3), 28.2 (C-6), 49.1 (N-
CH2CH2), 53.8 (N-CH2Ph), 55.2 (C-5), 61.6, 63.1
(CH2OAc), 71.5 (O-CH2Ph), 81.2, 81.7, 82.2 (C-2/C-3/C-
4), 104.9 (C-1), 111.4 (O-C-O), 126.7, 127.6, 127.9, 128.0,
128.4, 129.1, 137.1, 140.4 (Ar-C), 171.1 (strong, 2ꢃcO).
1,2-O-Isopropylidene-3-O-benzyl-5-(N-benzyl, N-hydroxy-
ethyl)amino-5,6-dideoxy-ꢁ-L-ido-heptofuranose
(11b).
The reaction of 10b (0.5 g, 0.92 mmol) and LAH (0.18
g, 4.74 mmol) in dry THF (8 cm3) for 2 h as described
for 10a and column chromatography (n-hexane/ethyl
acetate=3/2) gave 11b (0.34 g, 83%) as a thick liquid
(Found: C, 68.41; H, 7.84. C26H35NO6 requires C,
68.25; H, 7.71%); Rf=0.49 (n-hexane/ethyl acetate=2/
3); [a]D ꢁ80 (c 0.25 in CHCl3); nmax (neat)/cmꢁ1 3440-
3200 (br band); dH (300 MHz, CDCl3+D2O) 0.85–1.05
(1H, m, 6-Ha), 1.35 (3H, s, CH3), 1.50 (3H, s, CH3),
1.50–1.66 (1H, m, 6-Hb), 2.84–3.00 (2H, m, N-
CH2CH2), 3.42-3.70 (5H, m, 5-H, 2 CH2OH), 3.77 (1H,
d, J=3.0, 3-H), 3.88 (2H, AB quartet, J=12.7, N-
CH2Ph), 4.25 (1H, dd, J=3.0 and 10.2, 4-H), 4.37 (1H,
d, J=11.8, O-CH2Ph), 4.62 (1H, d, J=3.8, 2-H), 4.69
(1H, d, J=11.8, O-CH2Ph), 6.00 (1H, d, J=3.8, 1-H),
7.22–7.38 (10H, m, Ar-H); dC (75 MHz, CDCl3) 26.2,
26.8 (CH3), 30.2 (C-6), 52.8 (N-CH2CH2), 55.4 (N-
CH2Ph), 57.0 (c-5), 60.4, 61.9 (2CH2OH), 71.5 (O-
CH2Ph), 81.2, 81.4, 82.0 (C-2/C-3/C-4), 104.9 (C-1),
111.5 (O-C-O), 127.1, 127.9, 128.1, 128.4, 128.5, 129.5,
137.0, 139.6 (Ar-C).
1,2-O-Isopropylidene-5-(N-ꢁ-acetoxyethyl)amino-7-O-
acetyl-5,6-dideoxy-ꢀ -D -gluco-heptofuranose (13a). A
solution of 12a (0.64 g, 0.67 mmol) and 10% Pd/C (0.13
g) in methanol (7 cm3) was hydrogenolyzed at room
temperature at 80 psi for 12 h. The catalyst was filtered
through Celite and washed with methanol. Methanol
was evaporated off in vacuo and the residue was pur-
ified by column chromatography (n-hexane/ethyl ace-
tate=3/1) to yield 13a (0.38 g, 89%) as thick oil
(Found: C, 53.24; H, 7.69. C16H27NO8 requires C,
53.18; H, 7.53%); Rf=0.44 (n-hexane/ethyl acetate=1/
9); [a]D ꢁ26 (c 1.0 in CHCl3); nmax (neat)/cmꢁ1 3450–
3100 and 1735; dH (300 MHz, CDCl3) 1.30 (3H, s, CH3),
1.46 (3H, s, CH3), 1.89–1.98 (2H, m, 6-Ha and Hb), 2.05
(6H, s, 2ꢃCOCH3), 2.82–3.04 (2H, m, N-CH2CH2),
3.35 (1H, dt, J=3.0 and 6.6, 5-H), 3.41-3.55 (2H, br s,
exchange with D2O, NH and OH), 4.01 (1H, t, J=3.0,
4-H), 4.07–4.22 (4H, m, 2ꢃCH2OAc), 4.25 (1H, d,
J=3.0, 3-H), 4.47 (1H, d, J=3.6, 2-H), 5.94 (1H, d,
J=3.6, 1-H); dC (75 MHz, CDCl3) 20.8, 20.9, 26.1, 26.8
(CH3), 30.2 (C-6), 47.0 (N-CH2CH2), 55.3(C-5), 61.4,
63.2 (CH2OAc), 76.0, 80.3, 85.4 (C-2/C-3/C-4/), 104.6
(C-1), 111.4 (O-C-O), 170.5, 170.7 (CO).
1,2-O-Isopropylidene-3-O-benzyl-5-(N-ꢁ-acetoxyethyl,
N-benzyl)amino-7-O-acetyl-5,6-dideoxy-ꢀ-D-gluco-hepto-
furanose (12a). To a cooled (0 ꢀC) solution of diol 11a
(0.72 g, 1.57 mmol) in dry pyridine (1.5 cm3) was added
acetic anhydride (2.65 g, 25.95 mmol). After stirring the
reaction mixture for 4 h at 25 ꢀC, ice water was added
and extracted with chloroform (3ꢃ15 cm3). Usual work-
up and chromatography (n-hexane/ethyl acetate=9/1)
provided the diacetate 12a (0.72 g, 84%) as syrup
(Found: C, 66.67; H, 7.35. C30H39NO8 requires C, 66.53;
H, 7.26%); Rf=0.54 (n-hexane/ethyl acetate=2/1); [a]D
ꢁ16 (c 0.25 in CHCl3); nmax (neat)/cmꢁ1 1738; dH
(300MHz, CDCl3) 1.31 (3H, s, CH3), 1.49 (3H, s, CH3),
1.90 (3H, s, CH3), 1.99 (3H, s, CH3), 1.90–2.15 (2H, m, 6-
Ha and Hb), 2.68 (1H, dt, J=5.6 and 14.0, N-CH2CH2),
2.88 (1H, dt, J=6.4 and 14.0, N-CH2CH2), 3.25 (1H,
ddd, J=3.5, 5.0 and 8.8, 5-H), 3.55(1H, d, J=13.7, N-
CH2Ph), 3.68 (1H, dd, J=3.0 and 3.5, 4-H), 3.77 (1H, d,
J=13.7, N-CH2Ph), 3.89 (1H, d, J=3.0, 3-H), 3.92–4.08
1,2-O-Isopropylidene-5-(N-ꢁ-acetoxyethyl)amino-7-O-ace-
tyl-5,6-dideoxy-ꢁ-L-ido-heptofuranose (13b). Hydro-
genolysis of 12b (0.74 g, 1.37 mmol) in dry methanol (5

D. D. Dhavale et al. / Bioorg. Med. Chem. 11 (2003) 3295–3305
3301
cm3) as described for 12a followed by chromatography
(n-hexane/ethyl acetate=3/1) afforded 13b (0.35 g,
71%) as a thick oil (Found: C, 53.25; H, 7.58.
C16H27NO8 requires C, 53.18; H, 7.53%); Rf=0.58 (n-
hexane/ethyl acetate=1/9); [a]D +14 (c 2.0 in CHCl3);
nmax (neat)/cmꢁ1 3460–3100 and 1736; dH (300 MHz,
CDCl3) 0.90–1.80 (4H, m, NH, OH, 6-Ha and 6-Hb, on
D2O exchange integrated for 2H), 1.31 (3H, s, CH3),
1.48 (3H, s, CH3), 2.08 (6H, s, 2ꢃCOCH3), 2.68–2.90
(1H, m, N-CH2CH2), 3.05–3.20 (2H, m, 5-H, N-
CH2CH2), 4.04–4.27 (6H, m, 3-H, 4-H, 2 CH2OAc),
4.52 (1H, d, J=3.3, 2-H), 5.94 (1H, d, J=3.3, 1-H); dC
(75 MHz, CDCl3) 20.8, 20.9, 26.1, 26.9 (CH3), 30.4 (C-
6), 44.7 (N-CH2CH2), 54.7 (C-5), 61.2, 63.3 (CH2OAc),
77.4, 77.6, 85.8 (C-2/C-3/C-4), 104.8 (C-1), 111.5 (O-C-
O), 171.0, 171.1 (CO).
20.9, 26.3, 26.7 (CH3), 27.5 (C-6), 41.8 (N-CH2CH2),
52.1 (C-5), 61.4, 62.0 (CH2OAc), 67.3( O-CH2Ph), 74.7,
79.5, 85.5 (C-2/C-3/C-4), 104.1 (C-1), 111.6 (O-C-O),
127.5, 127.9, 128.4, 136.2 (Ar-C), 156.4, 170.7, 170.9
(CO).
1,5,6-Trideoxy-1,5-imino-N-(ꢁ-acetoxyethyl)-7-O-ace-
tyl-D-gluco-heptitol (15a). To a solution of TFA/water
(2 cm3, 3:2), cooled at 0 ꢀC, was added 14a (0.5 g, 1.01
mmol) and stirred for 30 min. The solution was allowed to
warm to 30ꢀC and stirred for 2 h. TFA-water was co-eva-
porated with toluene under high vacuum to provide an
anomeric mixture of hemiacetal which was directly used
in the next reaction. To a solution of hemiacetal in dry
methanol (6 cm3) was added 10% Pd/C (0.09 g) and
ammonium formate (0.38 g, 6.06 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 IR resin col-
umn (H+ form, 100-200 mesh, Dowex 50ꢃ8) using
CHCl3/MeOH/NH3 (25% solution)=80/18/2 as an
eluant to yield 15a (0.28 g, 89%) as a thick oil (Found:
C, 51.24; H, 7.75. C13H23NO7 requires C, 51.14; H,
7.59%); Rf=0.64 (CHCl3/MeOH=4/1);[a]D ꢁ24 (c1.0 in
CHCl3); nmax (nujol)/cmꢁ1 3500–3300 (br band) and 1728;
dH (300MHz, D2O) 1.90–2.20 (2H, br m, 6-Ha and Hb),
2.10 (6H, br s, 2ꢃCH3), 2.40–4.60 (12H, br m, 2-H, 3-H, 4-
H, 5-H, 2ꢃN-CH2 and 2ꢃCH2OAc); dC (75MHz, CDCl3)
21.0, 21.1 (CH3), 26.9 (C-6), 49.6, 56.5 (C-1/C-10), 61.2
(strong, C-7/C-20), 62.3( C-5), 69.1, 72.6, 79.1 (C-2/C-3/C-
4), 171.1, 171.4 (CO).
1,2-O-Isopropylidene-5-(N-ꢁ-acetoxyethyl, N-benzoxy-
carbonyl)amino-7-O-acetyl-5,6-dideoxy-ꢀ-D-gluco-hepto-
furanose (14a). To a stirred solution of 13a (0.46 g,
1.28 mmol) and NaHCO3 (0.3g, 3.60 mmol) in etha-
nol/water (2 cm3, 1:1,) at 0 ꢀC, was added benzyl
chloroformate (0.33 g, 1.93 mmol). The mixture was
stirred at room temperature for 4 h, quenched with
water and extracted with chloroform (3ꢃ10 cm3).
Work-up and chromatography (n-hexane/ethyl ace-
tate=9/1) provided 14a (0.56 g, 88%) as a thick
liquid19 (Found: C, 58.25; H, 6.83. C24H33NO10
requires C, 58.17; H, 6.71%); Rf=0.50 (n-hexane/ethyl
acetate=3/2); [a]D +42.86 (c 0.14 in CHCl3); nmax
(neat)/cmꢁ1 3430, 1736 and 1680; dH (300 MHz,
CDCl3) 1.20–2.00 (2H, br m, 6-Ha and H-b), 1.31 (3H,
s, CH3), 1.50 (3H, s, CH3), 1.98 (3H, s, CH3), 2.06 (3H,
s, CH3), 2.26–2.38 (1H, m, N-CH2CH2), 3.24–3.36 (1H,
m, N-CH2CH2), 3.56 (1H, dt, J=5.1 and 14.8, 5-H),
3.94–4.24 (6H, m, 3-H, 4-H and 2ꢃCH2OAc), 4.37–4.52
(1H, br m, OH, exchange with D2O), 4.53(1H, d,
J=3.6, 2-H), 5.08–5.26 (2H, AB quartet, J=12.1, O-
CH2Ph), 5.92 (1H, d, J=3.6, 1-H), 7.31–7.39 (5H, m,
Ar-H); dC (75 MHz, CDCl3) 20.9 (strong), 26.0, 26.8
(CH3), 28.2 (C-6), 42.0 (N-CH2CH2), 153.1 (C-5), 61.2,
62.4 (CH2OAc), 68.6 (O-CH2Ph), 73.9, 81.2, 84.4 (C-2/
C-3/C-4), 105.0 (C-1), 111.4 (O-C-O), 128.0, 128.5,
128.6, 135.3 (Ar-C), 156.2, 170.6, 170.8 (CO).
1,5,6-Trideoxy-1,5-imino-N-(ꢁ-acetoxyethyl)-7-O-ace-
tyl-L-ido-heptitol (15b). A reaction of (0.4 g, 0.80 mmol)
with TFA/water (2 cm3, 3:2) followed by hydrogenolysis
in dry methanol (5 cm3) with 10% Pd/C (0.08 g) and
ammonium formate (0.3g, 4.84 mmol) as stated for 14a
gave 15b (0.18 g, 88%) as a thick syrup (Found: C, 51.19;
H, 7.68. C13H23NO7 requires C, 51.19; H, 7.56%);
Rf=0.32 (CHCl3/MeOH=4/1); [a]D +4.35 (c 0.46 in
CHCl3); nmax (neat)/cmꢁ1 3500–3300 (br band) and 1730;
dH (300MHz, CDCl3+D2O) 1.60–2.15 (2H, br m, 6-Ha
and Hb), 2.05 (6H, s, 2ꢃCH3), 2.20–3.30 (5H, m, 2ꢃN-
CH2 and 5-H), 3.36–3.95 (3H, m, 2-H, 3-H and 4-H),
4.02–4.20 (4H, m, 2ꢃCH2OAc); dC (75 MHz, CDCl3)
21.0, 21.1 (CH3), 23.0 (C-6), 51.1, 52.8 (C-1/C-10), 59.2
(C-5), 62.0, 63.2 (C-7/C-20), 69.6, 70.9, 76.6 (C-2/C-3/C-
4), 171.2, 171.4 (CO).
1,2-O-Isopropylidene-5-(N-ꢁ-acetoxyethyl, N-benzoxy-
carbonyl)amino-7-O-acetyl-5,6-dideoxy-ꢁ-L-ido-heptofur-
anose (14b). A reaction of 13b (0.35 g, 0.97 mmol),
NaHCO3 (0.23g, 2.71 mmol) and benzyl chloroformate
(0.25 g, 1.45 mmol) in ethanol/water (3cm 3, 1:1) at 0 ꢀC
for 3h as described for 13a and chromatography (hex-
ane/ethyl acetate=3/1) yielded 14b (0.43g, 90%) as
white solid,19 mp 108–109 ꢀC (Found: C, 58.20; H, 6.85.
C24H33NO10 requires C, 58.46; H, 7.00%); Rf=0.50 (n-
hexane/ethyl acetate=1/1); [a]D ꢁ44.19 (c 0.86 in
CHCl3); nmax (nujol)/cmꢁ1 3451, 1736 and 1683; dH
(300 MHz, CDCl3) 1.29 (3H, s, CH3), 1.47 (3H, s, CH3),
1.70–2.00 (2H, m, 6-Ha and Hb), 1.98 (3H, s, CH3), 2.00
(3H, s, CH3), 2.82–2.98 (1H, br s, exchange with D2O),
3.37–3.56 (3H, m, 5-H and N-CH2CH2), 3.98–4.30 (6H,
m, 3-H, 4-H and 2ꢃCH2OAc), 4.51 (1H, d, J=3.0, 2-
H), 5.13(2H, s, O-CH2Ph), 5.88 (1H, d, J=3.0, 1-H),
7.26–7.34 (5H, m, Ar-H); dC (75 MHz, CDCl3) 20.8,
1,5,6-Trideoxy-1,5-imino-N-hydroxyethyl-D-gluco-hepti-
tol (4). To a cooled solution (0 ꢀC) of dry MeOH (3
cm3) a piece of Na (0.005 g) was added followed by 15a
(0.25 g, 0.82 mmol) in dry MeOH (1 cm3). Reaction
mixture was allowed to warm to 30 ꢀC and stirred for 2
h. IR resin (H+ form, 100–200 mesh, Dowex 50ꢃ8) was
added to the reaction mixture till neutral pH, filtered
and methanol was concentrated. The residue thus
obtained was purified by IR resin (H+ form) column
(CHCl3/MeOH/NH3=50/48/2) to afford pentaol 4
(0.154 g, 88%) as a hygroscopic syrup (Found: C, 48.70;
H, 8.73. C9H19NO5 requires C, 48.86; H, 8.65%);
Rf=0.15 (CHCl3/MeOH=1/1); [a]D ꢁ22.5 (c 0.8 in
MeOH); nmax (neat)/cmꢁ1 3450-3200 (br band); dH

3302
D. D. Dhavale et al. / Bioorg. Med. Chem. 11 (2003) 3295–3305
(300 MHz, D2O) 1.73–1.89 (2H, br m, 6-Ha and Hb),
2.12 (1H, dd, J=9.2 and 11.8, 1-Ha), 2.15–2.24 (1H, m,
5-H), 2.44 (1H, dt, J=5.7 and 13.5, 10-Ha), 2.73(1H, dt,
J=6.6 and 13.5, 10-Hb), 2.94 (1H, dd, J=4.4 and 11.8,
1-He), 3.04–3.14 (2H, m, 3-H and 4-H), 3.33–3.64 (5H,
m, 2-H and 2ꢃCH2OH); dC (75 MHz, D2O) 31.0 (C-6),
52.4, 56.0 (C-1/C-10), 58.3( C-5), 59.0, 62.5 (C-7/C-20),
68.3, 72.8, 78.3 (C-2/C-3/C-4).
J=10.7 and 13.2, 1-Ha), 2.84–3.08 (3H, m, 1-He and N-
CH2CH2), 3.18–3.29 (1H, m, 5-H), 3.98–4.22 (4H, m,
2ꢃCH2OAc), 4.95 (1H, ddd, J=5.5, 9.6 and 10.7, 2-H),
5.05 (1H, dd, J=5.5 and 10.2, 4-H), 5.23(1H, dd,
J=9.6 and 10.2, 3-H); dC (75 MHz, CDCl3) 21.1, 21.2
(strong), 21.3( CH3), 24.1 (C-6), 47.3( C-1), 53.4 (C-10),
56.7 (C-5), 62.1, 63.2 (C-7/C-20), 69.4, 70.3, 71.2 (C-2/
C-3/C-4), 170.0, 170.2, 170.3, 171.0, 171.1 (CO).
1,5,6-Trideoxy-1,5-imino-N-hydroxyethyl-L-ido-heptitol
(5). A reaction of 15b (0.27 g, 0.88 mmol) with
sodium methoxide in dry MeOH (1 cm3) for 2 h as
described for 15a followed by purification with IR
resin column using CHCl3/MeOH/NH3=50/48/2 as
an eluant gave pure 5 (0.19 g, 95%) as hygroscopic
syrup (Found: C, 48.72; H, 8.54. C9H19NO5 requires
C, 48.86; H, 8.65%); Rf=0.25 (CHCl3/EtOH=3/1);
[a]D ꢁ14.29 (c 2.1 in MeOH); nmax (neat)/cmꢁ1 3450–
3250 (br band); dH (300 MHz, D2O) 1.51–1.60 (2H, m
[apparent quartet with J=6.1], 6-Ha and Hb), 2.34
(1H, dd, J=9.9 and 12.2, 1-Ha), 2.51–2.62 (2H, m, N-
CH2CH2), 2.62 (1H, dd, J=5.2 and 12.2, 1-He), 2.82–
2.90 (1H, m, 5-H), 3.24 (1H, t, J=9.1, 3-H), 3.34–3.59
(6H, m, 2-H, 4-H and 2ꢃCH2OH); dC (75 MHz, D2O)
25.0 (C-6), 50.3, 55.2 (C-1/C-10), 59.2 (C-5), 60.1, 61.5
(C-7/C-20), 69.3, 70.4, 74.5 (C-2/C-3/C-4).
1,2-O-Isopropylidene-3,7-di-O-acetyl-5-(N-ꢁ-acetoxyethyl,
N-benzoxycarbonyl)amino-5,6-dideoxy-ꢀ-D-gluco-hepto-
furanose (17a). To a stirred solution of diacetate 14a
(1.0 g, 2.018 mmol) in pyridine (3cm 3 mmol) was added
acetic anhydride (3.70 g, 36.32 mmol) at 0 ꢀC. The mix-
ture was stirred at room temperature for 3h and quen-
ched with water. Usual workup and purification by
column chromatography (n-hexane/ethyl acetate=9/1)
provided 17a (1.02 g, 94%) as a semi solid19 (Found: C,
58.25; H, 6.80. C26H35NO11 requires C, 58.09; H,
6.56%); Rf=0.41 (n-hexane/ethyl acetate=3/1); [a]D
+8.6 (c 0.93in CHCl 3); nmax (neat)/cmꢁ1 1743and
1703; dH (300 MHz, CDCl3) 1.30 (3H, s, CH3), 1.52
(3H, s, CH3), 1.54–2.20 (2H, m, 6-Ha and Hb), 1.98
(3H, s, CH3), 2.06 (3H, s, CH3), 2.07 (3H, s, CH3), 3.18–
3.29 (1H, m, NCH2CH2), 3.38–3.52 (1H, m, 5-H), 3.98–
4.36 (6H, m, 4-H, NCH2CH2 and 2ꢃCH2OAc), 4.96–
5.18 (1H, d, J=3.7, 2-H), 5.08 (2H, s, O-Ch2Ph), 5.34
(1H, br s, 3-H), 5.91 (1H, d, J=3.7, 1-H), 7.21–7.38
(5H, m, Ar-H); dC (75 MHz, CDCl3) 20.7 (strong), 20.9,
25.9, 26.5 (CH3), 28.8 (C-6), 42.6 (N-CH2CH2), 51.7 (C-
5), 61.4, 62.7 (CH2OAc), 67.5 (O-CH2Ph), 74.5, 79.7, 83.2
(C-2/C-3/C-4), 104.4 (C-1), 111.7 (O-C-O), 127.5, 127.8,
128.3, 135.8 (Ar-C), 155.9, 169.1, 169.4, 170.5 (CO).
1,5,6-Trideoxy-1,5-imino-2,3,4,7-tetra-O-acetyl-N-(ꢁ-
acetoxyethyl)-D-gluco-heptitol (16a). To an ice cold
solution of 4 (0.12 g, 0.54 mmol) in pyridine (0.8 cm3)
was added acetic anhydride (0.99 g, 9.72 mmol). The
reaction mixture was allowed to warm and stirred at
30 ꢀC for 12 h. Toluene (5 cm3) was added and evapo-
rated at reduced pressure (three times). The residue
obtained on chromatography (hexane/ethyl acetate=5/
5) gave 16a (0.23g, 98%) as a thick syrup (Found: C,
52.97; H, 6.89. C19H29NO10 requires C, 52.89; H,
6.77%); Rf=0.59 (CHCl3/MeOH=9.5/0.5); [a]D +15 (c
1.2 in CHCl3); nmax (neat)/cmꢁ1 1738 (br); dH
(300 MHz, CDCl3) 1.74–1.90 (1H, m, 6-Ha), 1.99 (3H, s,
CH3), 2.01 (3H, s, CH3), 2.02 (3H, s, CH3), 2.03–2.10
(1H, m, 6-Hb), 2.04 (3H, s, CH3), 2.05 (3H, s, CH3),
2.42–2.52 (1H, m, 5-H), 2.74–2.88 (2H, m, 1-Ha and 10-
Ha), 2.97 (1H, dt, J=5.3and 14.0, 1 0-Hb), 3.27 (1H, dd,
J=4.0 and 12.6, 1-He), 4.02–4.27 (4H, m, 2ꢃCH2OAc),
4.92 (1H, t, J=9.5, 3-H), 4.92–5.06 (2H, m, 2-H and 4-
H); dC (75 MHz, CDCl3) 20.7 (strong), 20.8, 20.9, 21.0
(CH3), 26.7 (C-6), 47.3( C-1), 52.4 (C-10), 59.7 (C-5),
60.5, 61.6 (C-7/C-20), 68.1, 70.9, 74.7 (C-2/C-3/C-4),
169.7, 169.8, 170.1, 170.7, 170.8 (CO).
1,2-O-Isopropylidene-3,7-di-O-acetyl-5-(N-ꢁ-acetoxyethyl,
N-benzoxycarbonyl)amino-5,6-dideoxy-ꢁ-L-ido-heptofur-
anose (17b). Acetylation of 14b (1.2 g, 2.42 mmol) with
acetic anhydride (4.45 g, 43.56 mmol) in pyridine (3
cm3) for 3h as stated for 14a afforded 17b (1.26 g, 77%)
as a white solid19 mp 83–84 ꢀC; (Found: C, 58.00; H,
6.55. C26H35NO11 requires C, 58.09; H, 6.56%);
Rf=0.50 (n-hexane/ethyl acetate=1/1); [a]D ꢁ17.5 (c
0.8 in CHCl3); nmax (nujol)/cmꢁ1 1744 and 1701; dH
(300 MHz, CDCl3) 1.29 (3H, s, CH3), 1.50 (3H, s, CH3),
1.49–2.30 (2H, m, 6-Ha and Hb), 1.98 (3H, s, CH3), 2.02
(3H, s, CH3), 2.08 (3H, s, CH3), 2.35–3.09 (2H, m, 5-H
and NCH2CH2), 3.92–4.30 (6H, m, 4-H, NCH2CH2 and
2ꢃCH2OAc), 4.48 (1H, d, J=3.3, 2-H), 5.10–5.19 (3H,
m, 3-H and O-CH2Ph), 5.86 (1H, d, J=3.3, 1-H), 7.25–
7.33 (5H, m, Ar-H); dC (75 MHz, CDCl3) 20.6, 20.8,
26.1, 26.3, 26.5 (CH3), 27.2 (C-6), 41.1 (N-CH2CH2),
50.9 (C-5), 60.6, 61.7 (CH2OAc), 67.1 (O-CH2Ph), 75.8,
77.7, 83.4 (C-2/C-3/C-4), 104.1 (C-1), 111.9 (O-C-O),
127.4, 127.8, 128.3, 136.2 (Ar-C), 156.3, 169.4, 170.4,
170.5 (CO).
1,5,6-Trideoxy-1,5-imino-2,3,4,7-tetra-O-acetyl-N-(ꢁ-
acetoxyethyl)-L-ido-heptitol (16b). Acetylation of 5 (0.15
g, 0.68 mmol) with acetic anhydride (1.25 g, 12.24
mmol) in pyridine (1 cm3) for 12 h as stated for 4 and
purification by column chromatography provided 16b
(0.28 g, 97%) as a thick syrup (Found: C, 52.95; H,
6.83. C19H29NO10 requires C, 52.89; H, 6.77%);
Rf=0.45 (CHCl3/EtOH=9/1); [a]D ꢁ12 (c 0.1 in
CHCl3); nmax (neat)/cmꢁ1 1740 (br); dH (300 MHz,
CDCl3) 1.81–1.92 (1H, m, 6-Ha), 2.02 (3H, s, CH3), 2.03
(3H, s, CH3), 2.04 (3H, s, CH3), 2.05 (3H, s, CH3), 2.07
(3H, s, CH3), 2.06–2.16 (1H, m, 6-Hb), 2.69 (1H, dd,
1,4,5-Trideoxy-1,4-imino-2,6-di-O-acetyl-N-(ꢁ-acetoxy-
ethyl)-D-arabino-hexitol (18a). A solution of 17a (0.85 g,
0.74 mmol) in TFA/water (5 cm3, 3:2) was stirred at
30 ꢀC for 3h. Toluene (5 cm ) was added and evapo-
3
rated at reduced pressure to give a hemiacetal as a thick
oil. To a mixture of hemiacetal in acetone/water (4 cm3,
2:1) at 0 ꢀC sodium metaperiodate (0.51 g, 2.37 mmol)

D. D. Dhavale et al. / Bioorg. Med. Chem. 11 (2003) 3295–3305
3303
3
was added and stirred for 3h. Ethylene glycol (0.3cm
)
MeOH=1/1); [a]D ꢁ13.04 (c 0.46 in MeOH); nmax
(nujol)/cmꢁ1 3450–3200 (br band); dH (300 MHz, D2O)
1.58–1.73(1H, m, 5-Ha), 1.85–1.98 (1H, m, 5-Hb),
2.28–2.42 (2H, m, N-CH2CH2), 2.68 (1H, dd, J=6.3
and 11.3, 1-Ha), 2.85–3.00 (2H, m, 1-Hb and 4-H),
3.55–3.80 (5H, m, H-3 and 2ꢃCH2OH), 4.00 (1H, ddd,
J=1.5, 5.5 and 6.3, 2-H); dC (75 MHz, D2O) 33.9 (C-5),
55.9, 59.1 (C-1/C-10), 59.5 (strong, CH2OH), 69.3( C-4),
75.9 (C-3), 82.6 (C-2).
was added to the reaction mixture and extracted with
dichloromethane (5 cm3 ꢃ 3). The organic layer was
dried, concentrated and the residue was purified by col-
umn chromatography (hexane/ethyl acetate=3/1) to
afford a semi-solid (0.78 g). To a solution of the semi-
solid in dry methanol (5 cm3) was added 10% Pd/C
(0.15 g) and ammonium formate (0.6 g, 9.51 mmol). The
reaction mixture was refluxed for 45 min and the solu-
tion was filtered through Celite, washed with methanol
and concentrated. The residue was passed through silica
column [hexane/ethyl acetate/ammonia solution
(25%)=64/35/1] to afford 18a (0.38 g, 76%) as a thick
oil (Found: C, 53.22; H, 7.52. C14H23NO7 requires C,
52.99; H, 7.30%); Rf=0.45 (hexane/ethyl acetate=1/4);
[a]D ꢁ12.86 (c 1.4 in CHCl3); nmax (neat)/cmꢁ1 3400–
3150 (br band) and 1734; dH (300 MHz, CDCl3+D2O)
1.74–1.86 (1H, m, 5-Ha), 2.00–2.15 (1H, m, 5-Hb), 2.05
(3H, s, CH3), 2.06 (3H, s, CH3), 2.10 (3H, s, CH3), 2.34–
2.48 (2H, m, N-CH2CH2), 2.75 (1H, dd, J=7.5 and
11.3, 1-Ha), 3.04 (1H, ddd, J=5.5, 6.8 and 12.6, 4-H),
3.21 (1H, dd, J=1.8 and 11.3, 1-Hb), 3.87 (1H, dd,
J=2.7 and 6.8, 3-H), 4.07–4.24 (4H, m, 2ꢃCH2OAc),
4.73(1H, ddd, J=1.8, 2.7 and 8.0, 2-H); dC (75 MHz,
D2O) 21.0, 21.1, 21.2 (CH3), 29.9 (C-5), 51.7, 57.3( C-1/
C-10), 61.3( C-4), 62.5, 67.3( C-2/C-6), 81.1 (C-2), 81.7
(C-3), 170.7, 170.9, 172.3 (CO).
1,4,5-Trideoxy-1,4-imino-N-hydroxyethyl-L-xylo-hexitol
(7). A reaction of 18b (0.4 g, 1.26 mmol) with sodium
3
methoxide in dry methanol (3cm ) for 1.5 h as descri-
bed for 18a followed by purification with IR resin col-
umn chromatography (CHCl3/MeOH/NH3=50/48/2)
gave 7 as syrup (0.23g, 96%) as a oil (Found: C,
50.41; H, 8.22. C8H17NO4 requires C, 50.25; H,
8.36%); Rf=0.19 (CHCl3/MeOH=1/2); [a]D +40 (c
0.35 in MeOH); nmax (nujol)/cmꢁ1 3460–3100 (br
band); dH (300 MHz, D2O) 1.71–1.82 (2H, m, 5-H),
2.26 (1H, dd, J=5.2 and 11.0, 1-Ha), 2.41 (1H, dt,
J=5.7 and 12.6, N-CH2CH2), 2.77 (1H, dt, J=5.1 and
9.0, 4-H), 2.91 (1H, dt, J=6.8 and 12.6, N-CH2CH2),
3.38 (1H, dd, J=6.1 and 11.0, 1-Hb), 3.60–3.68 (4H, m,
2ꢃCH2OH), 3.97 (1H, dd, J=2.5 and 5.0, 3-H), 4.04–
4.09 (1H, m, 2-H); dC (75 MHz, D2O) 29.6 (C-5), 56.2,
58.8 (C-1/C-10), 59.5, 59.6 (CH2OH), 64.6 (C-4), 76.2
(C-3), 77.2 (C-2).
1,4,5-Trideoxy-1,4-imino-2,6-di-O-acetyl-N-(ꢁ-acetoxy-
ethyl)-L-xylo-hexitol (18b). A reaction of 17b (1.0 g, 1.86
mmol) with TFA/water (6 cm3, 3:2) for 3 h followed by
sodium metaperiodate oxidation, hydrogenation as
described for 17a and purification by chromatography
(n-hexane/ethyl acetate/ammonia=70/28/2) gave 18b as
a thick oil (0.53g, 90%) (Found: C, 53.24; H, 7.55.
C14H23NO7 requires C, 52.99; H, 7.30%); Rf=0.35 (n-
hexane/ethyl acetate=1/4); [a]D +40 (c 0.5 in CHCl3);
nmax (neat)/cmꢁ1 3450–3150 (br band) and 1736; dH
(300 MHz, CDCl3+D2O) 1.88–2.21 (2H, m, 5-H), 2.06
(6H, strong s, 2ꢃCH3), 2.08 (3H, s, CH3), 2.34 (1H, dd,
J=5.7 and 10.7, 1-Ha), 2.53(1H, dt, J=5.7 and 13.2,
N-CH2CH2), 2.69 (1H, ddd, J=4.4, 4.7 and 9.6, 4-H),
3.05 (1H, dt, J=5.7 and 13.2, N-CH2CH2), 3.65 (1H,
dd, J=6.6 and 10.7, 1-Hb), 4.02 (1H, dd, J=1.7 and
4.7, 3-H), 4.08–4.25 (4H, m, 2ꢃCH2OAc), 4.88 (1H,
ddd, J=1.7, 5.2 and 6.6, 2-H); dC (75 MHz, CDCl3)
21.0 (s), 21.1 (CH3), 26.2 (C-5), 51.7, 57.2 (C-1/C-10),
62.1 (C-4), 62.5, 64.3( CH2OAc), 75.9 (C-3), 79.6 (C-2),
170.7, 170.8, 170.9 (CO).
1,4,5-Trideoxy-1,4-imino-2,3,6-tri-O-acetyl-N-(ꢁ-acetoxy-
ethyl)-D-arabino-hexitol (19a). To an ice-cold solution of
6 (0.10 g, 0.52 mmol) in pyridine (0.8 cm3) was added
acetic anhydride (0.1 g, 9.36 mmol). The reaction mix-
ture was allowed to warm and stirred at 30 ꢀC for 12 h.
Toluene (4 cm3) was added and evaporated at reduced
pressure (three times). The residue thus obtained on
chromatography (hexane/ethyl acetate/ammonia solu-
tion=70/29/1)) gave tetra-acetate 19a (0.17 g, 93%) as a
thick oil (Found: C, 53.69; H, 7.32%. C16H25NO8
requires C, 53.47; H, 7.01%); Rf=0.46 (hexane/ethyl
acetate=1/1; [a]D ꢁ46.80 (c 0.47 in CHCl3); nmax (neat)/
cmꢁ1 1740 (br); dH (300 MHz, CDCl3) 1.80–2.08 (2H,
m, 5-H), 2.05 (3H, s, CH3), 2.06 (6H, s, 2ꢃCH3), 2.09
(3H, s, CH3), 2.50 (1H, dt, J=5.3and 1.32,
N-
CH2CH2), 2.62–2.68 (1H, m, N-CH2CH2), 2.78 (1H, dd,
J=5.3 and 11.3, 1-Ha), 3.01 (1H, ddd, J=5.3, 7.1 and
12.1, 4-H), 3.17 (1H, dd, J=1.5 and 11.3, 1-Hb), 4.05–
4.26 (4H, m, 2ꢃCH2OAc), 5.01 (2H, br d, J=5.3, 2-H
and 3-H); dC (75 MHz, CDCl3) 21.0 (strong), 21.1
(strong, CH3), 29.7 (C-5), 52.2, 57.9 (C-1/C-1), 61.0 (C-
4), 62.5, 66.3( CH2OAc), 76.6 (C-2), 80.7 (C-3), 169.7,
170.2, 170.6, 170.8 (CO).
1,4,5-Trideoxy-1,4-imino-N-hydroxyethyl-D-arabino-hex-
itol (6). To a cooled (0 ꢀC) solution of dry MeOH (2
cm3) a piece of sodium (0.005 g) was added with stirring
followed by 18a (0.22 g, 0.69 mmol) in dry MeOH (1
cm3). Reaction mixture was allowed to warm to 30 ꢀC
and stirred for 1.5 h. IR resin was added to the reaction
mixture until pH became neutral, filtered and con-
centrated. The residue thus obtained was washed with
dry dichloromethane, concentrated in vacuo and pur-
ified by IR resin column using CHCl3/MeOH/NH3=50/
48/2 as eluant to afford tetraol 6 (0.13g, 95%) as
hygroscopic oil (Found: C, 49.98; H, 8.66. C8H17NO4
requires C, 50.25; H, 8.36%); Rf=0.20 (CHCl3/
1,4,5-Trideoxy-1,4-imino-2,3,6-tri-O-acetyl-N-(ꢁ-acetoxy-
ethyl)-L-xylo-hexitol (19b). Acetylation of 7 (0.15 g, 0.78
mmol) with acetic anhydride (1.43g, 14.04 mmol) in
pyridine (1 cm3) for 12 h as described for 6 and chro-
matographic purification (n-hexane/ethyl acetate/
ammonia solution=70/29/1) gave 19b (0.27 g, 97%) as
a thick syrup (Found: C, 53.69; H, 7.17. C16H25NO8
requires C, 53.47; H, 7.01%); Rf=0.41 (n-hexane/ethyl
acetate=2/3); [a]D +28.0 (c 0.5 in CHCl3); nmax (neat)/
cmꢁ1 1738 (br); dH (300 MHz, CDCl3) 1.78–1.94 (2H,

3304
D. D. Dhavale et al. / Bioorg. Med. Chem. 11 (2003) 3295–3305
m, 5-H), 2.04 (3H, s, CH3), 2.07 (3H, s, CH3), 2.08 (3H,
s, CH3), 2.12 (3H, s, CH3), 2.33 (1H, dd, J=5.2 and
11.0, 1-Ha), 2.57 (1H, dt, J=5.7 and 13.2, N-CH2CH2),
2.89 (1H, ddd, J=5.0, 5.5 and 8.0, 4-H), 3.03 (1H, dt,
J=6.6 and 13.2, N-CH2CH2), 3.65 (1H, dd, J=6.6 and
11.0, 1-Hb), 4.07–4.22 (4H, m, 2ꢃCH2OAc), 5.00 (1H,
ddd, J=2.5, 5.2 and 6.6, 2-H), 5.22 (1H, dd, J=2.5 and
5.5, 3-H); dC (75 MHz, CDCl3) 21.0 (strong, CH3), 26.7
(C-5), 52.3, 57.6 (C-1/C-10), 61.8 (C-4), 62.6, 62.9
(CH2OAc), 76.5, 77.2 (C-2/C-3), 169.8, 169.9, 170.6,
170.7 (CO).
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Acknowledgements
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We thank the Indian Council for Cultural Relations
(ICCR), New Delhi and Department of Science and
Technology (SP/S1/G-32/2000), New Delhi for financial
support and the University of Chittagong, Bangladesh
for study leave. We are grateful to Professor M. S.
Wadia for helpful discussion.
References and Notes
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restricted rotation around C–N bond. The prominent

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