N-Glycosylamines of 4,6-Oethylidene-α-D-gIucopyranose: Synthesis, characterisation and structure of CO2H, Cl and F ortho-substituted phenyl derivatives and metal ion complexes of the CO2H derivative

Article abstract of DOI:10.1039/b004854m

A saccharide based ligand suitable for metal binding (HL_COOH) has been synthesized using 4,6-O-ethylidene-α-D-glucopyranose (4,6-O-EGP) and anthranilic acid. A few analogous glycosylamines with chloro and fluoro ortho substitutions have also been synthesized and characterised. Complexes of HL_COOHwith Na⁺, K⁺, Mg²⁺, Ca²⁺, Ba²⁺, Cd²⁺ and Hg²⁺ have been isolated and characterised fully. The crystal structures of 4,6-O-EGP, the chloro analogue of HL_COOH and the K⁺ complex of L_COOH are established. The anomeric nature, orientation of the binding core and the co-ordination aspects of K⁺ have been derived from these structures. The Royal Society of Chemistry 2000.

Full text of DOI:10.1039/b004854m

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N-Glycosylamines of 4,6-O-ethylidene-ꢀ-D-glucopyranose: synthesis,
characterisation and structure of CO2H, Cl and F ortho-substituted
phenyl derivatives and metal ion complexes of the CO2H
derivative†
Ajay K. Sah,a Chebrolu P. Rao,*a Pauli K. Saarenketo,b Elina K. Wegelius,b Kari Rissanenb
and Erkki Kolehmainenb
a Bioinorganic Laboratory, Department of Chemistry, Indian Institute of Technology, Bombay,
Powai, Mumbai-400 076, India. Fax: (ϩ91-22) 572 3480; E-mail:
cprao@ether.chem.iitb.ernet.in
b Department of Chemistry, University of Jyvaskyla, Jyvaskyla, Fin 40351, Finland
Received 19th June 2000, Accepted 30th August 2000
First published as an Advance Article on the web 3rd October 2000
A saccharide based ligand suitable for metal binding (HLCOOH) has been synthesized using 4,6-O-ethylidene-α--
glucopyranose (4,6-O-EGP) and anthranilic acid. A few analogous glycosylamines with chloro and fluoro ortho
substitutions have also been synthesized and characterised. Complexes of HLCOOH with Naϩ, Kϩ, Mg2ϩ, Ca2ϩ, Ba2ϩ
,
Cd2ϩ and Hg2ϩ have been isolated and characterised fully. The crystal structures of 4,6-O-EGP, the chloro analogue
of HLCOOH and the Kϩ complex of LCOOH are established. The anomeric nature, orientation of the binding core and
the co-ordination aspects of Kϩ have been derived from these structures.
(4,6-O-EGP) based aromatic glycosylamines possessing ortho
Introduction
substitutions. Further this paper also deals with the synthesis,
and analytical and spectral characterisations, of complexes of
N-(o-carboxyphenyl)-4,6-O-ethylidene-β--glucopyranosyl-
amine with Naϩ, Kϩ, Mg2ϩ, Ca2ϩ, Ba2ϩ, Cd2ϩ and Hg2ϩ ions.
The potassium complex has been characterized by single crystal
X-ray diffraction.
Knowledge regarding the chemistry of interaction of metal
ions with saccharides is of potential importance to the field of
inorganic chemistry in general and bioinorganic chemistry in
particular, due to the fact that both saccharides and metal ions
coexist in biological systems.1,2 Only during the past decade or
so, the literature is concerned mainly with the characterisation
of the isolated products of interaction of transition metal ions
with simple saccharides.3 However, the understanding of these
interactions was limited due to the lack of crystal structures of
sufficient metal ion–saccharide complexes. This problem can
partly be circumvented via modifying the saccharides either by
selectively blocking some OH groups or by modifying these
through glycosylation at position C1 or by a combination of
both.4–7 Some recent literature reports include crystal structures
of glucose based platinum() complexes by Steinborn’s group8
and metal ion complexes of 1,2- and 5,6-blocked glucofuran-
ose by the groups of Floriani, Duthaler and Togni.6,9,10 Jäger,
Klemm and co-workers have recently communicated bi- and
tri-nuclear copper complexes of a glucose based β-oxoenamine
ligand.11 On the other hand, Yano’s group has reported crystal
structures of a number of transition metal ion complexes of
C1–N glycosides derived from the reactions of glucose and dif-
ferent amines,7,12 Leary’s group has reported only the structure
of an aminoglycoside ligand derived from diethylenetriamine
and demonstrated the interaction of this with Zn2ϩ based on
mass spectral data.13a All the metal ion complexes of the glyco-
sylamines reported are ionic in nature. However, there have
been hardly any literature reports regarding metal ion com-
plexes of glycosylamines derived from aromatic amines possess-
ing ortho functionalities, which are expected to enhance the
metal ion binding characteristics of the corresponding sacchar-
ides. Therefore, in this paper we report the synthesis and char-
acterisation of a series of 4,6-O-ethylidene-α--glucopyranose
Experimental
Glucose was procured from Aldrich Chem. Co. (USA), amines
from Lancaster Synthesis Ltd (UK) and paraldehyde from
BDH (UK). All the solvents were purified and dried
immediately before use. Elemental analysis was carried out on
a Carlo-Erba elemental analyser and FTIR spectra were
recorded on a Nicolet Impact 400 machine. TGA/DTA studies
1
were carried out on a Perkin-Elmer TGA7/DTA7 System. H
NMR spectra were recorded on a Bruker Avance DRX 500
spectrometer in (CD3)2SO.
Synthesis of ligands
4,6-O-ethylidene-ꢀ-D-glucopyranose (4,6-O-EGP). This was
prepared by a literature procedure using 200 mmol -glucose.14
The crystalline product was isolated in two crops. This com-
pound was also synthesized on a 2000 mmol scale by appropri-
ately scaling-up all the components. Single crystals suitable
for X-ray diffraction were grown from an ethanolic solution of
the compound by slow diffusion of toluene.
N-(o-Carboxyphenyl)-4,6-O-ethylidene-ꢁ-D-glucopyranosyl-
amine (HLCOOH). 4,6-O-EGP (6.18 g, 30 mmol) and anthranilic
acid (4.11 g, 30 mmol) were suspended in ethanol (40 mL) and
the reaction mixture was refluxed while stirring for 30 min
during which it turned to solid material. This was then cooled
to room temperature and the product filtered off, washed with
ethanol and dried under vacuum.
† Dedicated to Professor S. J. Lippard on his 60th birthday.
DOI: 10.1039/b004854m
J. Chem. Soc., Dalton Trans., 2000, 3681–3687
3681
This journal is © The Royal Society of Chemistry 2000

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Table 1 Composition, yield, mp, and elemental analysis data for all the compounds
Found (Calc.) (%)
Compound
Composition
Yield (%)
Mp/ЊC
C
H
N
4,6-O-EGP
HLCOOH
C8H14O6
56
71
42
33
65
70
57
84
84
77
72
174–175
46.33
(46.60)
55.26
(55.38)
55.64
(56.21)
53.37
(53.25)
49.22
(49.32)
46.20
(46.16)
44.81
(45.11)
46.58
(46.28)
41.97
6.83
(6.84)
6.03
(5.89)
6.11
(6.06)
5.88
(5.74)
5.85
(5.51)
5.63
(5.42)
6.03
(6.31)
6.08
(5.95)
5.37
—
C15H19NO7
159–161a
139–141a
150–152a
138–140a
152–154a
3.89
(4.30)
4.42
(4.68)
4.82
(4.43)
3.74
(3.83)
3.55
(3.59)
3.31
(3.50)
3.86
(3.60)
3.15
(3.26)
2.99
LF
C14H18FNO5
LCl
C14H18ClNO5
1 Na–LCOOH
2 K–LCOOH
3 Mg–LCOOH
4 Ca–LCOOH
5 Ba–LCOOH
6 Cd–LCOOH
7 Hg–LCOOH
C15H18NNaO7ؒH2O
(KC15H18NO7)2ؒ3H2O
Mg(C15H18NO7)2ؒ7H2O
Ca(C15H18NO7)2ؒ5H2O
Ba(C15H18NO7)2ؒ4H2O
Cd(C15H18NO7)2ؒ5H2O
Hg(C15H18NO7)2ؒ2H2O
>160b
>170b
>170b
(42.01)
42.19
(42.31)
40.63
(5.17)
5.86
(5.45)
4.38
146–149a
146–148a
(3.29)
2.90
(3.16)
(40.71)
(4.55)
a Compound melted and turned brown. b Compound turned brown but did not melt.
4,6-O-Ethylidene-N-(o-fluorophenyl)-ꢁ-D-glucopyranosyl-
amine (LF). 4,6-O-EGP (0.41 g, 1.99 mmol) and o-fluoroaniline
(0.20 mL, 2.07 mmol) were suspended in ethanol (7 mL) and a
catalytic amount of zinc chloride (0.006 g, 0.04 mmol) was
added. The reaction mixture was allowed to reflux for 3 h, then
cooled to room temperature. It was concentrated under reduced
pressure to about 4 mL and kept overnight at room temperature
to yield a solid product which was separated by filtration and
the residue then washed with cold ethanol followed by ether
and dried in vacuo.
Ca–LCOOH 4. To a solution of HLCOOH (0.60 g, 1.85 mmol) in
40 mL of THF, triethylamine (0.26 mL, 1.9 mmol) was added
and the reaction mixture stirred at room temperature under N2
atm for 0.5 h and then CaCl2ؒ2H2O (0.14 g, 0.92 mmol) was
added and stirring continued. In 10 minutes the mixture
became light yellow. This was stirred for 18 h at room temper-
ature, concentrated and kept in a deep freezer at Ϫ20 ЊC. After
4 h, 10 mL of ether were added. A white precipitate was formed
which was collected after one day and was twice stirred in
CHCl3 to remove NEt3ؒHCl formed during the reaction.
N-(o-Chlorophenyl)-4,6-O-ethylidene-ꢁ-D-glucopyranosyl-
amine (LCl). This compound was prepared by adopting the
procedure given for LF, but using 4,6-EGP (0.41 g, 1.99 mmol),
o-chloroaniline (0.21 ml, 2.00 mmol) and a catalytic amount of
zinc chloride (0.006 g). Single crystals of the product suitable
for X-ray diffraction study were grown by slow evaporation of
the concentrated ethanolic solution.
Ba–LCOOH 5. This compound was prepared by a procedure
similar to that adopted for 1, but by using 0.33 g (1.01 mmol) of
HLCOOH and 0.16 g (0.49 mmol) Ba(OH)2ؒ8H2O in 25 mL of
THF.
Cd–LCOOH 6. This compound was prepared by a procedure
similar to that adopted for 1, but by using 0.33 g (1.01 mmol) of
HLCOOH and 0.13 g (0.47 mmol) Cd(OAc)2ؒ2H2O in 25 mL
THF.
Synthesis of metal ion complexes
Na–LCOOH 1. To a solution of 0.36 g (1.10 mmol) HLCOOH in
30 ml THF–methanol (5:1 v/v), solid sodium hydroxide 0.045 g
(1.125 mmol) was added and allowed to stir at room temper-
ature. After 24 h the stirring was stopped and the reaction
mixture concentrated to about 4–5 mL under vacuum followed
by addition of ether to precipitate the product. The product was
isolated by filtration, re-dissolved in methanol and precipitated
using diethyl ether.
Hg–LCOOH 7. This compound was prepared by a procedure
similar to that adopted for 3, but by using 0.32 g (0.98 mmol)
HLCOOH and 0.16 g (0.49 mmol) Hg(OAc)2 in 25 mL of THF.
Preliminary data including analytical results of all these
compounds are listed in Table 1.
X-Ray crystallography
Standard procedures were used for mounting the crystals. The
diffraction data were collected for 4,6-O-EGP, LCl and K–
LCOOH 2 on a Nonius Kappa CCD machine in the ꢀ scan ϩω
scan mode using Mo-Kα radiation. The structures were solved
using SHELXS 97 and refined using SHELXL 97 program
packages.15 The diagrams were generated using ORTEP 3 and
PLUTON 98 programs.16 Full matrix least-squares refinement
with anisotropic thermal parameters for all non-hydrogen
atoms was used. The hydrogen atoms were treated as riding
atoms with fixed thermal parameters. Other details of data
collection and structure refinement are provided in Table 2.
CCDC reference number 186/2168.
K–LCOOH 2. This complex was prepared by adopting the
procedure given for Na–LCOOH, but using 0.30 g (0.92 mmol) of
HLCOOH and 0.68 g (0.91 mmol) of potassium hydroxide. Single
crystals suitable for X-ray studies were obtained by slow
evaporation of a methanolic solution of the product at 4 ЊC.
Mg–LCOOH 3. To a clear solution of 0.33 g (1.01 mmol) HLCOOH
in 25 mL THF, 0.11 g (0.51 mmol) of solid Mg(OAc)2ؒ4H2O
was added and the reaction mixture stirred at room temperature
for 24 h. A white precipitate of the product was formed during
the course of the reaction, which was isolated by filtration and
the filtrate concentrated to 4–5 mL followed by addition of an
excess of ether to precipitate a second crop.
See http://www.rsc.org/suppdata/dt/b0/b004854m/ for crys-
tallographic files in .cif format.
3682
J. Chem. Soc., Dalton Trans., 2000, 3681–3687

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Table 2 Summary of crystallographic data for compounds 4,6-O-EGP, LCl and K–LCOOH
2
4,6-O-EGP
LCl
K–LCOOH 2
Empirical formula
Molecular weight
C8H14O6
206.19
C14H18ClNO5
315.74
C32.5H47K2N2O17
815.92
T/K
Crystal system
Space group
173(2)
Monoclinic
P21
173(2)
Orthorhombic
P212121
173(2)
Monoclinic
C2
a/Å
b/Å
c/Å
5.012(1)
6.738(1)
13.748(4)
97.31(1)
460.51(18)
2
7.056(1)
12.346(1)
16.512(1)
—
1438.4(3)
4
21.562(1)
13.501(1)
15.041(1)
122.07(1)
3710.4(4)
4
β/Њ
V/Å3
Z
Total reflections
Unique reflections
Final R (I > 2σ(I))
Rw
1130
7624
10452
7437 [R(int) = 0.0227]
0.0375
1130 [R(int) = 0.0000]
0.0544
0.1125
4287 [R(int) = 0.0322]
0.0313
0.0754
0.0944
Results and discussion
Protected glucose, 4,6-O-EGP, its C1–N glycosylated products
(HLCOOH, LF, and LCl) and the metal ion complexes of LCOOH
(Na–LCOOH 1; K–LCOOH 2; Mg–LCOOH 3; Ca–LCOOH 4; Ba–
LCOOH 5; Cd–LCOOH 6 and Hg–LCOOH 7) have been synthesized
as shown in Scheme 1 and were well characterized.
Scheme 1 i, Paraldehyde/concentrated H2SO4 (catalyst); ii, suitable
ortho-substituted aniline and iii, suitable metal salt.
4,6-O-Ethylidene-ꢀ-D-glucopyranose (4,6-O-EGP)
-Glucopyranose was protected at its 4 and 6 positions using
paraldehyde to result in 4,6-O-EGP as in the Experimental sec-
tion. H NMR and its D2O exchange spectra of this molecule
Fig. 1 1H NMR of (a) 4,6-O-EGP, (b) HLCOOH and (c) Ca–LCOOH
measured in DMSO-d6.
1
revealed the presence of only three hydroxyl groups observed at
δ 6.45, 4.99 and 4.72 respectively. The hydrogen atom attached
to C1 was found at δ 4.93 and its J value (4.4 Hz) supports the
presence of the α anomeric form in the molecule. The 1H NMR
spectrum of this molecule is shown in Fig. 1(a). However, a
reaction of 4,6-O-EGP with anilines substituted in the ortho-
position by CO2H (HLCOOH), F (LF), and Cl (LCl). All these
compounds showed satisfactory elemental analysis (Table 1),
1
1
and were characterized based on FTIR and H NMR spectra.
mixture of anomers was found, based on H NMR, when this
One, LCl, has been structurally characterized by single crystal
X-ray diffraction. Formation of glycosylamines was indicated
by FTIR spectra where the sharp band originating from the
C1–OH stretching vibration (3491 cmϪ1) disappeared as
expected. Formation of the glycosylated product was further
revealed by comparing its FTIR spectrum with that of the pre-
cursor, i.e. 4,6-O-EGP. The fingerprint region clearly indicated
the presence of an aromatic moiety. In the case of LCOOH, νC᎐O
α form was left in solution to equilibrate over a period of time.
The molecular structure of 4,6-O-EGP based on single crystal
X-ray diffraction is shown in Fig. 2(a). The molecule adopts a
pyranose structure with positions 4 and 6 being connected by
an ethylidene moiety. The stereo view of this molecule shown in
Fig. 2(b) also supports the α-anomeric form. The pyranose ring
is present in the chair form. Some important bond lengths and
bond angles are given in Table 3 and the data does not show any
abnormalities. The crystal lattice exhibited five O–H ؒ ؒ ؒ O type
intermolecular hydrogen bonds with O ؒ ؒ ؒ O distances in the
range 2.714–3.160 Å and angles in the range 131.4–174.6Њ,
indicating the presence of intermolecular interactions.
was found at 1700 cmϪ1
.
1
In all cases H NMR spectra were recorded in DMSO-d6
from fresh solutions, since stored solutions exhibited anomer-
isation of the glycosylamine; the corresponding data are given
in Table 4. The spectrum of HLCOOH is shown in Fig. 1(b). The
spectra were compared with that of the precursor, i.e. 4,6-O-
ortho-Substituted aromatic glycosylamines of 4,6-O-ethylidene-
ꢀ-D-glucopyranose
1
EGP. The H NMR spectra of the glycosylamines showed the
presence of only two OH groups from the saccharide moiety
Three different C1–glycosylamines are synthesized from the
and indicated the loss of C1–OH, which was found at δ 6.45
J. Chem. Soc., Dalton Trans., 2000, 3681–3687
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for the precursor molecule 4,6-O-EGP, as expected due to
glycosylation at C1. The peak positions of the OH groups were
cross-checked by their signal disappearance upon addition of
D2O. Both the chemical shift (δ 4.59–4.71) and the J value
for the C1–H (7.5–8.5 Hz) of the glycosylated products clearly
its α-anomeric form. Such a change in the anomeric form on
going from 4,6-O-EGP to its C1–glycosylamine is in accord-
ance with the low energy conformation expected with the
β-anomeric form13b in the latter case. The remaining skeletal
proton signals appeared in the expected ranges, as given in
Table 4.
supported the presence of the β-anomeric form13a in HLCOOH
,
LF, and LCl. However, the precursor 4,6-O-EGP was found in
The molecular structure of LCl based on single crystal X-ray
diffraction is shown in Fig. 3(a). It revealed the presence of
C1–glycosylation of the saccharide moiety with the correspond-
ing amine. Further, the saccharide moiety maintained its
pyranose form with the 4 and 6 positions being protected by
the ethylidene moiety as in the structure of the precursor, 4,6-
O-EGP. The stereo view of this molecule shown in Fig. 3(b)
supports the presence of the β-anomeric form. The glycosyl-
ation clearly resulted in a change in the state of the anomeric
form from α to β. Thus the results obtained from the crystal
structure are comparable with those obtained from solution
studies, based on 1H NMR spectra. Some important bond
lengths and bond angles are given in Table 5. The metric
parameters have not shown any abnormalities. The stereo view
shown in Fig. 3(b) of this molecule indicates that the ortho
substituent is oriented in the same direction as that of C2–OH.
The pyranose ring is present in the chair form. The orientation
of the molecule observed in the lattice was expected to facilitate
the binding of metal ions if the ortho substituent were to be a
group capable of binding (the group that is present in place of
Cl). Therefore, among the three glycosylamines reported here,
HLCOOH is suited for metal ion binding, and we report the
synthesis, characterisation and crystal structure of metal ion
bound products of HLCOOH. The crystal lattice of LCl exhibited
Fig. 2 (a) Molecular structure of 4,6-O-EGP and (b) a stereo view
showing 25% probability thermal ellipsoids using ORTEP.
Table 3 Selected bond lengths (Å) and angles (Њ) for 4,6-O-EGP
O(3)–C(3)
O(4)–C(4)
O(5)–C(5)
O(6)–C(6)
C(2)–C(3)
C(4)–C(5)
C(7)–C(8)
1.433(5)
1.436(4)
1.424(4)
1.425(5)
1.522(5)
1.521(5)
1.501(6)
O(4)–C(7)
O(5)–C(1)
O(6)–C(7)
C(1)–C(2)
C(3)–C(4)
C(5)–C(6)
1.428(5)
1.423(5)
1.418(5)
1.535(6)
1.498(7)
1.502(7)
C(1)–O(5)–C(5)
O(1)–C(1)–O(5)
O(5)–C(1)–C(2)
O(2)–C(2)–C(1)
O(3)–C(3)–C(2)
C(4)–C(3)–C(2)
O(4)–C(4)–C(5)
O(5)–C(5)–C(6)
C(6)–C(5)–C(4)
O(6)–C(7)–O(4)
O(4)–C(7)–C(8)
111.7(3)
112.0(3)
110.1(3)
111.1(3)
111.0(3)
108.8(3)
108.2(3)
110.6(3)
108.0(3)
111.2(3)
107.9(4)
C(7)–O(4)–C(4)
C(7)–O(6)–C(6)
O(1)–C(1)–C(2)
O(2)–C(2)–C(3)
O(3)–C(3)–C(4)
C(3)–C(2)–C(1)
O(4)–C(4)–C(3)
C(3)–C(4)–C(5)
O(5)–C(5)–C(4)
O(6)–C(6)–C(5)
O(6)–C(7)–C(8)
111.0(3)
111.2(3)
107.3(3)
108.4(3)
109.6(3)
110.8(3)
110.5(3)
110.4(3)
110.1(3)
108.3(3)
108.0(3)
Fig. 3 (a) Molecular structure of LCl and (b) stereo view showing 50%
probability level thermal ellipsoids using ORTEP for all non-hydrogen
atoms.
Table 4 1H NMR data (δ) for all the compounds recorded in DMSO-d6
Saccharide protons
Compound
HLCOOH
NH
8.39
C1–H
OH
Aromatic protons
4.71
5.47, 5.32
6.69 (1H), 6.84 (1H), 7.38 (1H), 7.80 (1H)
12.78 (CO2H)
5.27, 5.16
5.35, 5.29
5.63
6.05, 5.64
5.44
5.57
5.70
5.45
5.42, 5.29
LF
LCl
5.52
5.57
9.83
9.97
9.06
9.38
9.57
9.06
8.78
4.56
4.62
4.59
4.56
4.65
4.66
4.65
4.64
4.70
6.63 (1H), 6.95 (3H)
6.71 (1H), 6.93 (1H), 7.15 (1H), 7.28 (1H)
6.51 (1H), 6.71 (1H), 7.09 (1H), 7.81 (1H)
6.49 (1H), 6.67 (1H), 7.05 (1H), 7.77 (1H)
6.59 (1H), 6.80 (1H), 7.21 (1H), 7.91 (1H)
6.57 (1H), 6.77 (1H), 7.17 (1H), 7.93 (1H)
6.55 (1H), 6.75 (1H), 7.14 (1H), 7.90 (1H)
6.59 (1H), 6.79 (1H), 7.21 (1H), 7.92 (1H)
6.64 (1H), 6.87 (1H), 7.27 (1H), 7.87 (1H)
1 Na–LCOOH
2 K–LCOOH
3 Mg–LCOOH
4 Ca–LCOOH
5 Ba–LCOOH
6 Cd–LCOOH
7 Hg–LCOOH
C5–H of the saccharide molecule was found in the range δ 3.97–4.00 and the rest of the five skeletal protons in the range δ 3.00–3.50. CH3 of the
protecting group was found at δ 1.22–1.25 and its CH at δ 4.69–4.72.
3684
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1
Table 5 Selected bond lengths (Å) and angles (Њ) for LCl
Based on H NMR spectra, it was evident that no organic
solvent molecules were associated with the metal ion complexes.
However the FTIR spectra indicated the presence of H2O
molecules. The latter was supported by TGA/DTA analysis.
The complexes (1, 2, and 4–7) lost water molecules till about
160 ЊC, followed by slow decomposition of the organic moiety.
Complexes 1, 2, 4, 5, 6 and 7 lost 1, 3, 5, 4, 5 and 2 molecules of
water respectively. In the case of Hg–LCOOH 7 the weight loss
was ≈100% at 685 ЊC indicating that Hg was vaporised due to
the decomposition of HgO. All the other complexes exhibited
residual mass (11.3 to 23.5%) indicating the presence of non-
volatile products at the end. In the case of the barium complex,
5, no weight loss were found beyond 500 ЊC. Thus the presence
of H2O molecules has been identified based on FTIR, TGA/
DTA and elemental analysis. While on the one hand the alkali
and alkaline-earth metal ions are hydrophilic, at least some of
the water molecules present in these complexes seem to be
involved in stabilising the corresponding co-ordination poly-
hedron as the glycosylamine alone cannot fulfil the co-
ordination sphere. However, the co-ordination sphere around
each metal ion can be fulfilled by the formation of a polymeric
structure incorporating the solvent molecules as demonstrated
in case of the potassium complex, 2, where crystallisation
from MeOH resulted in the replacement of some of the water
molecules by MeOH.
C(2)–O(1)
C(2)–C(3)
C(3)–C(4)
C(4)–C(6)
C(6)–C(8)
C(8)–O(1)
C(11)–O(10)
C(11)–C(12)
C(16)–Cl(17)
1.419(18)
1.531(2)
1.504(2)
1.528(2)
1.533(2)
1.447(18)
1.406(19)
1.497(2)
1.742(2)
C(2)–C(9)
C(3)–O(13)
C(4)–O(5)
1.517(2)
1.431(18)
1.428(17)
1.417(19)
1.419(2)
1.436(2)
1.438(17)
1.387(19)
C(6)–O(7)
C(8)–N(14)
C(9)–O(10)
C(11)–O(13)
C(15)–N(14)
O(1)–C(2)–C(9)
C(9)–C(2)–C(3)
O(13)–C(3)–C(2)
O(5)–C(4)–C(3)
C(3)–C(4)–C(6)
O(7)–C(6)–C(8)
N(14)–C(8)–O(1)
O(1)–C(8)–C(6)
110.57(12)
108.27(12)
109.17(12)
108.98(11)
108.53(12)
106.93(12)
108.69(12)
110.40(11)
O(1)–C(2)–C(3)
O(13)–C(3)–C(4)
C(4)–C(3)–C(2)
O(5)–C(4)–C(6)
O(7)–C(6)–C(4)
C(4)–C(6)–C(8)
N(14)–C(8)–C(6)
O(10)–C(9)–C(2)
O(10)–C(11)–C(12)
C(15)–N(14)–C(8)
C(11)–O(10)–C(9)
109.37(12)
110.32(11)
109.02(12)
112.42(12)
110.45(12)
109.90(13)
110.82(13)
107.87(12)
110.11(14)
123.53(14)
111.54(13)
O(10)–C(11)–O(13) 110.08(12)
O(13)–C(11)–C(12)
C(2)–O(1)–C(8)
107.85(12)
111.08(11)
110.85(11)
C(3)–O(13)–C(11)
two strong O–H ؒ ؒ ؒ O type intermolecular hydrogen bonds
where the two free OH groups of the saccharide moiety act as
donors, with O ؒ ؒ ؒ O distances of 2.785 and 2.956 Å and
H-bond angles of 179 and 170.2Њ respectively, indicating
intermolecular interactions.
Molecular and lattice structure of K–LCOOH
2
At 4 ЊC the complex K–LCOOH 2 crystallised in the monoclinic
space group from its methanolic solution resulting in an
empirical formula, (KLCOOH)2ؒ2MeOHؒH2O. This compound
exhibited an interesting crystal structure. Two types of potas-
sium ions are present in the asymmetric unit, of which one (K1)
has full occupancy whereas the other occupies two positions
(K2a and K2b), having occupancy 0.5 each as these two sit on
special positions in the unit cell. K1 is co-ordinated to six oxy-
gen atoms giving rise to an octahedral co-ordination sphere.
The metric data around K1 clearly indicated distorted octa-
hedral geometry. The co-ordinated oxygen centers for K1 arise
from the saccharide as well as from two methanol molecules.
One of these methanol molecules bridges between K1 and K2b.
K2a and K2b are surrounded by 8 oxygen donor atoms. The
co-ordination around each crystallographic potassium ions is
shown in Fig. 4(a), (b) and (c). The packing diagram of the unit
cell shows an interesting layer type structure, where one layer
contains only K1 followed by the next layer, which contains
K2a and K2b. A view of the lattice structure of this complex is
shown in Fig. 5. K2b and K1 are connected via bridging carb-
oxylic oxygen as well as methanol oxygens. The binding mode
of the ligand LCOOH towards Kϩ ions in the lattice is shown in
Fig. 6. Thus both the glycosylamine moiety and MeOH are
responsible for the formation of the layered type polymeric
structure. Selected bond lengths and bond angles about each
potassium ion center are given in Table 6. The potassium–
oxygen distances in all the three co-ordination spheres are in the
range 2.721 to 3.046 Å, with an average of 2.861 Å. These bond
lengths are well consistent with literature values for KO6 and
KO8 systems.17
Metal ion complexes of HLCOOH
A series of metal ion complexes of HLCOOH has been syn-
thesized using Naϩ, Kϩ, Mg2ϩ, Ca2ϩ, Ba2ϩ, Cd2ϩ and Hg2ϩ. The
composition of all these complexes is given in Table 1. All these
products were characterized based on FTIR, 1H NMR spectra
and on TGA/DTA analysis. One, K–LCOOH 2, has structurally
been characterised by single crystal X-ray diffraction.
In the FTIR spectra of the metal ion complexes, 1 to 7, νC᎐O
was found in the range 1600–1620 cmϪ1whereas in case of the
precursor ligand, HLCOOH, νC᎐O was found at 1700 cmϪ1. The
shift observed supports the pa᎐rticipation of the CO2H group in
complex formation. The spectra observed in the OH stretching
vibrational region were broadened when compared to that of
the precursor ligand due to the presence of H2O in the metal
ion complexes.
The metal ion complex formation was further supported by
1H NMR studies. The corresponding data are given in Table 4.
Disappearance of the CO2H proton, downfield shift of the NH
proton and shifts of the saccharide OH proton signals were
1
some of the general features observed in the H NMR spectra
of these complexes. The spectrum of a representative complex
Ca–LCOOH 2 is shown in Fig. 1(c). Both the NH and OH proton
signals were identified through D2O exchange experiments. In
the metal ion complexes, 1 to 7, the two saccharide OH
groups and one NH group were found to retain their protons.
The NH proton signals were shifted downfield for the com-
plexes in DMSO-d6 by 0.4 to 1.6 ppm when compared to
their position for the precursor ligand, HLCOOH. Thus the
observed shifts in the NH proton signal of the complexes are
in the order Hg2ϩ < Cd2ϩ ≈ Mg2ϩ < Ca2ϩ < Ba2ϩ < Naϩ < Kϩ,
higher with monovalent ions than with divalent ones. Fur-
ther, in the case of alkali and alkaline-earth metal ions, in the
same group, as the size increases the downfield shift also
increases. 1H NMR spectral data corresponding to the sac-
charide OH groups clearly indicated that these are not
involved in co-ordination in the case of the complexes of
cadmium and mercury, 6 and 7. Combining this result with
that of the analytical composition and the chemical nature of
the metal ions, it is possible to propose tetrahedral structures
Conclusion
A successful systematic approach has been reported in this
paper to synthesize saccharide based ligands suitable for metal
ion binding. Glucose has partially been protected to result
in 4,6-O-EGP in the α-anomeric form. The presence of the α-
anomeric form of glucose in 4,6-O-EGP has been established
1
based on H NMR as well as single crystal XRD study. A few
analogous glycosylamines based on 4,6-O-EGP have also been
synthesized and were well characterised. Although 4,6-O-EGP
Ϫ
1
for these complexes where the CO2 and NH are bound in 6
was in the α-anomeric form, H NMR of the glycosylamines
and 7.
indicated the presence of the β-anomeric form. The presence of
J. Chem. Soc., Dalton Trans., 2000, 3681–3687
3685

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Table 6 Selected bond lengths (Å) and angles (Њ) for K–LCOOH
K(1)–O(1B)
K(1)–O(16B)
K(1)–O(12B 4)
K2a–O3a, K2a–O3a 2
2.721(2)
K(1)–O(31)
K(1)–O(41)
K(1)–O(19B)
2.750(2)
2.821(2)
2.936(18)
2.983(2)
2.722(18)
2.870(2)
2.985(19)
2.926(2)
3.046(19)
2.930(19)
2.754(18)
2.815(19)
2.815(2)
_
_
_
_
K2a–O3b 3, K2a–O3b 4
_
_ _
K2a–O18a, K2a–O18a 2
K2a–O18b 3, K2a–O18b 4
_
_
_
K2b–O1b, K2b–O1b 2
K2b–O16a 3, K2b–O16a 4
_
_
_
K2b–O18a 3, K2b–O18a 4
K2b–O31, K2b–O31 2
O1b–K1–O31
O1b–K1–O41
O1b–K1–O19b
O31–K1–O16b
O31–K1–O19b
70.85(7)
115.52(6)
108.97(6)
75.12(6)
78.73(6)
125.61(6)
100.59(6)
112.73(5)
115.32(6)
55.18(5)
93.23(8)
169.73(6)
52.89(5)
130.84(5)
160.58(6)
117.52(9)
91.29(6)
73.30(9)
74.10(5)
67.79(6)
58.03(5)
139.59(5)
85.70(5)
76.84(7)
O1b–K1–O16b
O1b–K1–O12b 4
145.56(6)
88.66(6)
85.49(6)
159.16(6)
66.00(6)
58.20(5)
124.15(5)
85.93(8)
125.28(6)
74.72(5)
78.43(5)
83.74(6)
110.47(7)
86.42(5)
79.39(6)
168.69(9)
79.59(6)
108.02(5)
131.81(6)
159.27(8)
133.15(6)
119.71(5)
78.06(5)
_
O31–K1–O41
O31–K1–O12b 4
_
O16b–K1–O41
O16b–K1–O19b
O41–K1–O19b
_
O16b–K1–O12b 4
_
O41–K1–O12b 4
_
_
O18a–K2a–O18a 2
O12b 4–K1–O19b
_
_
_
_ _ _
O18a–K2a–O18b 4, O18a 2–K2a–O18b 3
O18a–K2a–O18b 3, O18a 2–K2a–O18b 4
_
_
_
_ _ _
O18a–K2a–O3b 4, O18a 2–K2a–O3b 3
O18a–K2a–O3b 3, O18a 2–K2a–O3b 4
_
_
_ _ _ _
O18b 3–K2a–O3b 3, O18b 4–K2a–O3b 4
O18b 3–K2a–O18b 4
_
_
_
_
_ _ _
O18b 4–K2a–O3a, O18b 3–K2a–O3a 2
O18b 4–K2a–O3b 3, O18b 3–K2a–O3b 4
_
_
_
_ _
O3b 3–K2a–O3b 4
O18 4–K2a–O3a 2, O18b 3–K2a–O3a
O3a 2–K2a–O3b 3
_
_
_ _ _
O3a 2–K2a–O3b 4, O3a–K2a–O3b 3
_
_ _
O18a–K2a–O3a, O18a 2–K2a–O3a 2
O18a–K2a–O3a 2
_
_ _
O16a 3–K2b–O16a 4
O3a–K2a–O3a 2
_
_
_
_ _ _
O16a 4–K2b–O31, O16a 3–K2b–O31 2
O16a 3–K2b–O31, O16a 4–K2b–O31 2
_
_ _ _
O16a 3–K2b–O1b 2, O16a 4–K2b–O1b
O31–K2b–O31 2
_
_
_
_ _
O31–K2b–O1b 2, O31 2–K2b–O1b
O16a 3–K2b–O1b, O16a 4–K2b–O1b 2
_
_
_
_
O1b–K2b–O1b 2
O31–K2b–O1b, O31 2–K2b–O1b 2
_
_
_
_ _ _ _
O16a 4–K2b–O18a 3, O16a 3–K2b–O18a 4
O16a 4–K2b–O18a 4, O16a 3–K2b–O18a 3
_
_
_
_
_
_ _ _
O31–K2b–O18a 4, O31 2–K2b–O18a 3
O31–K2b–O18a 3, O31 2–K2b–O18a 4
_
_ _ _
O1b–K2b–O18a 3, O1b 2–K2b–O18a 4
O1b–K2b–O18a 4, O1b 2–K2b–O18a 3
_
_
O18a 3–K2b–O18a 4
Fig. 5 3-D Molecular structure of K–LCOOH showing the layer type
structure obtained from ORTEP 50% probability level thermal ellips-
oids for all non-hydrogen atoms.
Fig. 4 Co-ordination around (a) K1, (b) K2a and (c) K2b in the
molecular structure of K–LCOOH generated from ORTEP showing 50%
probability level thermal ellipsoids.
the latter form in one of the glycosylamines (LCl) has been
confirmed from single crystal X-ray study. The structure of the
C(1)-glycosylamine has indicated a suitable orientation for
metal binding utilising the OH groups of the saccharide
Fig. 6 Binding mode of LCOOH towards Kϩ ions; C1, C2, C3, C4, C5
and C6 denote the numbering system followed for the glucose moiety.
and the ortho substituent. Complexes of Naϩ, Kϩ, Mg2ϩ, Ca2ϩ
,
Ba2ϩ, Cd2ϩ and Hg2ϩ have been synthesized with one of the
glycosylamines (HLCOOH) and were characterized using various
(4,6-O-EGP), a glycosylamine (LCl), and a metal ion complex
(K–LCOOH) were established. In the structure of K–LCOOH it was
found that primarily oxygen atoms participate in the co-
ordination. While the carboxyl group is bound to the metal ion
analytical and spectral means, and in the case of K–LCOOH
2
also by single crystal X-ray study. Thus during the present
study molecular and crystal structures of the starting precursor
3686
J. Chem. Soc., Dalton Trans., 2000, 3681–3687

View Article Online
9 U. Piarulli, D. N. Williams, C. Floriani, G. Gervasio and D. Viterbo,
as carboxylate, the OH groups of the saccharide interacted
without deprotonation in the case of the alkali and alkaline-
earth metal ion complexes, 1–5. However, in 6 and 7 the
saccharide OH group is not bound to the metal ion. These
molecules are potentially suitable for complexation with trans-
ition metal ions as well and corresponding studies are currently
underway in our laboratory.
J. Chem. Soc., Chem. Commun., 1994, 1409; U. Piarulli, D. N.
Williams, C. Floriani, G. Gervasio and D. Viterbo, J. Chem. Soc.,
Dalton Trans., 1995, 3329; U. Piarulli, C. Floriani, N. Re,
G. Gervasio and D. Viterbo, Inorg. Chem., 1998, 37, 5142.
10 R. O. Duthaler, P. Herold, W. Lottenbach, K. Oertle and
M. Riediker, Angew. Chem., Int. Ed. Engl., 1989, 28, 495; G. Bold,
R. O. Duthaler and M. Riediker, Angew. Chem., Int. Ed. Engl., 1989,
28, 497; M. Riediker, A. Hafner, U. Piantini, G. Rihs and A. Togni,
Angew. Chem., Int. Ed. Engl., 1989, 28, 499.
11 R. Wegner, M. Gottschaldt, H. Görls, E.-G. Jäger and D. Klemm,
Angew. Chem., Int. Ed. Engl., 2000, 39, 595.
Acknowledgements
C. P. R. acknowledges financial support from the Department
of Science and Technology, Board of Research in Nuclear
Sciences of Department of Atomic Energy and Council of
Scientific and Industrial Research. We thank Dr A. Ramanan,
IIT Delhi for TGA/DTA data.
12 S. Yano, S. Inoue, Y. Yasuda, T. Tanase, Y. Mikata, T. Kakuchi,
T. Tsubomura, M. Yamasaki, I. Kinoshita and M. Doe, J. Chem.
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I. Kinoshita, K. Shibata, M. Doe, J. Fujii and S. Yano, Inorg. Chem.,
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13 (a) S. P. Gaucher, S. F. Pedersen and J. A. Leary, J. Org. Chem.,
1999, 64, 4012; (b) I. L. Finar, Organic Chemistry Volume 2:
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J. Chem. Soc., Dalton Trans., 2000, 3681–3687
3687