Dimethyl N,N′-oxalamidodiethanoate

Article abstract of DOI:10.1107/S0108270101006965

The title compound, dimethyl 2,2′-(oxalyldiimino)diethanoate, C₈H₁₂N₂O₆, exhibits a network of hydrogen bonds between amide and ester groups. Molecules lie on inversion centres and show a planar conformation for both the oxalamide and ester groups. The glycine residues adopt a conformation close to the polyglycine II structure.

Full text of DOI:10.1107/S0108270101006965

organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
ISSN 0108-2701
Dimethyl N,N0-oxalamidodiethanoate
Figure 1
ORTEPII (Johnson, 1976) drawing of the title compound with the atomic
numbering scheme for non-H atoms. Displacement ellipsoids are drawn
at the 50% probability level and H atoms are drawn as circles of arbitrary
radii.
a
b
 a
Elaine Armelin, Lourdes Urpõ, Xavier Solans and Jordi
Âa
Puiggalõ *
a
Â
Á
Departament d'Enginyeria Quõmica, Universitat Politecnica de Catalunya, Av.
Diagonal 647, E-08028 Barcelona, Spain, and bDepartament de Cristallografia,
Á
Â
Â
Mineralogia i Diposits Minerals, Universitat de Barcelona, Martõi Franques, E-08028
The planar conformation of the oxalamide group is also
favoured by the establishment of an intramolecular NHÁ Á ÁOC
hydrogen bond (Table 2) of a pseudo-C5 type (a ®ve-
membered ring characteristic of amino acids, where in this
case a carbonyl C atom replaces the Cꢀ atom; Karle et al.,
1994). The torsion angles (O1ÐC2ÐC3ÐN1) and ' (C2Ð
C3ÐN1ÐC4), which de®ne the glycine residue, are close to
those found in the polyglycine II structure ( 145 and 75ꢁ,
respectively; Crick & Rich, 1955). However, the angle
deviates towards 180ꢁ, in agreement with theoretical studies
(Momenteua et al., 1988) on polydepsipeptide chains and also
with experimental data from model compounds of polyester
Barcelona, Spain
Correspondence e-mail: puiggali@eq.upc.es
Received 23 February 2001
Accepted 26 April 2001
The title compound, dimethyl 2,20-(oxalyldiimino)diethan-
oate, C8H12N2O6, exhibits a network of hydrogen bonds
between amide and ester groups. Molecules lie on inversion
centres and show a planar conformation for both the
oxalamide and ester groups. The glycine residues adopt a
conformation close to the polyglycine II structure.
Â
amides (Urpõ et al., 1998).
Molecules lie on inversion centres and the crystal structure
is de®ned by a bilayered organization, as shown in Fig. 2. The
packing is characterized by the establishment of a network of
intermolecular hydrogen bonds that only involve the NH and
CO moieties of the oxalamide and ester groups, respectively.
This observation is also in agreement with theoretical inves-
Comment
Studies of the conformational preferences of the oxalamide
group are nowadays interesting for the design of enzyme
mimics and potential inhibitors (Karle et al., 1994), since it
corresponds to a retrobispeptide unit. In addition, molecules
with oxalamide groups are capable of forming two-dimen-
sional networks, constituting signi®cant targets for supramol-
ecular synthesis (Coe et al., 1997). Polyoxalamides have also
been widely studied in materials science because of the
properties afforded by their stiff and hydrophilic units
(Shalaby et al., 1973; Gaymans et al., 1984; Tirrell & Vogl,
1977). Our research has recently focused on the study of
polyester amides derived from natural ꢀ-amino acids and
various diols and dicarboxylic acids, since a biodegradable
behaviour is characteristic of this kind of polymer (Paredes et
al., 1998). The title compound, (I), was chosen as the simplest
model constituted by glycine residues in combination with
oxalamide and ester groups.
Â
tigations (Aleman et al., 1995), which indicated a similar
The title molecule is shown in Fig. 1, with selected torsion
angles and hydrogen-bond geometry in Tables 1 and 2,
respectively.
The amide and ester groups are planar within experimental
accuracy, with an r.m.s. distance of the atoms from the best
Figure 2
Packing diagram of the title compound showing the network of
intermolecular hydrogen bonds between NH and CO groups (dashed
lines). The view is along the crystallographic a axis.
Ê
planes passing through them of 0.0062 and 0.0075 A for C3/
N1/C4/O3/C40/O30/N10/C30 and C1/O1/C2/O2/C3, respectively.
ꢀ
932 # 2001 International Union of Crystallography
Printed in Great Britain ± all rights reserved
Acta Cryst. (2001). C57, 932±933

organic compounds
Table 1
strength for amide±ester and amide±amide interactions.
Crystal structures of compounds with oxalamide units and
neighbouring ester or acid groups show both possibilities: (a)
`like-to-like' amide±amide hydrogen bonds (Klaska et al.,
1980; Yamaguchi et al., 1992; Bhattacharjee & Ammon, 1982)
and (b) `like-to-unlike' amide±acid (Coe et al., 1997; Karle &
Ranganathan, 1995) or amide±ester (Karle et al., 1994)
hydrogen bonds. The structure of the latter is similar to that
found in the title compound. However, it should be pointed
out that, in those cases, the `like-to-unlike' interactions would
be favoured by the steric hindrance of lateral groups
(compounds with aminoisobutyryl or leucyl residues) or the
capability to form additional hydrogen bonds between the
oxalamide carbonyl and the hydroxyl of the acid groups.
Two CÐHÁ Á ÁO interactions found in the crystal may also be
classi®ed as hydrogen bonds (Table 2). One of these interac-
tions involves the ester group, whereas the second one affects
the oxalamide unit.
Selected bond angles (ꢁ).
C1ÐO1ÐC2ÐC3
C4iÐC4ÐN1ÐC3
178.58 (17)
179.01 (14)
C4ÐN1ÐC3ÐC2
O1ÐC2ÐC3ÐN1
80.54 (19)
162.85 (14)
Symmetry code: (i) 2 x; y; 1 z.
Table 2
Hydrogen-bonding geometry (A, ).
ꢁ
Ê
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
N1ÐH1NÁ Á ÁO2i
0.77 (2)
0.77 (2)
2.26 (2)
2.37 (2)
2.886 (2)
2.707 (2)
139 (2)
108 (2)
N1ÐH1NÁ Á ÁO3ii
Symmetry codes: (i)
3
2
1 1
x; y
;
2 2
z; (ii) 2 x; y; 1 z.
H atoms were found in difference Fourier maps. However, those
not linked to the amide N atoms were re®ned using constraints
Ê
(CÐH = 0.96±0.97 A).
Data collection: CAD-4 Software (Kiers, 1994); cell re®nement:
SETANG and LS in CAD-4 Software; data reduction: local program;
program(s) used to solve structure: SHELXS97 (Sheldrick, 1997);
program(s) used to re®ne structure: SHELXL97 (Sheldrick, 1997);
molecular graphics: ORTEPII (Johnson, 1976).
Experimental
A solution of glycine methyl ester hydrochloride (0.2 mol) and
triethylamine (0.4 mol) in chloroform (250 ml) was treated with a
solution of oxaloyl chloride (0.1 mol) in chloroform (150 ml), which
was added slowly while maintaining the temperature at 273 K. After
1.5 h at room temperature, the solution was evaporated, yielding a
white powder which was recrystallized from 2-propanol (yield 47%,
m.p. 434 K). Colourless prismatic crystals were obtained by vapour
diffusion (293 K) of a 46:54 (v/v) chloroform/carbon tetrachloride
mixture, as precipitant, into a 56:44 (v/v) chloroform/carbon tetra-
chloride solution (concentration 2.6 mg ml 1).
This research was supported through CICYT grant
MAT2000/0995. The authors are grateful to Dr Campos for
help with the data collection.
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: JZ1454). Services for accessing these data are
described at the back of the journal.
References
Crystal data
Â
Aleman, C., Navas, J. J. & MunÄoz-Guerra, S. (1995). J. Phys. Chem. 99, 17653±
17661.
3
C8H12N2O6
Mr = 232.20
Monoclinic, P21/n
Dx = 1.403 Mg m
Cu Kꢀ radiation
Cell parameters from 25
re¯ections
Bhattacharjee, S. K. & Ammon, H. L. (1982). Acta Cryst. B38, 2503±2505.
Coe, S., Kane, J. J., Nguten, T. L., Toledo, L. M., Wininger, E., Fowler, F. W. &
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Ê
a = 10.4122 (11) A
ꢂ = 10.0±28.5ꢁ
ꢃ = 1.05 mm
T = 293 (2) K
Ê
b = 4.7567 (8) A
1
Ê
c = 11.6778 (16) A
ꢁ = 108.168 (10)ꢁ
3
Ê
V = 549.54 (13) A
Z = 2
Prism, colourless
0.24 Â 0.14 Â 0.12 mm
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Laboratory, Tennessee, USA.
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Data collection
Enraf±Nonius CAD-4 diffrac-
tometer
!/2ꢂ scans
999 measured re¯ections
999 independent re¯ections
880 re¯ections with I > 2ꢄ(I)
ꢂmax = 67.9ꢁ
h = 12 ! 11
k = 0 ! 5
l = 0 ! 14
3 standard re¯ections
frequency: 120 min
intensity decay: none
Â
Â
Â
Paredes, N., Rodrõguez-Galan, A. & Puiggalõ, J. (1998). J. Polym. Sci. Polym.
Re®nement
Chem. Ed. 36, 1271±1282.
Shalaby, S. W., Pearce, E. M., Fredericks, R. J. & Turi, E. A. (1973). J. Polym.
Sci. Polym. Phys. Ed. 11, 1±14.
È
Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Gott-
ingen, Germany.
Tirrell, D. & Vogl, O. (1977). J. Polym. Sci. Polym. Chem. Ed. 15, 1889±1903.
Re®nement on F2
R[F2 > 2ꢄ(F2)] = 0.057
wR(F2) = 0.155
S = 1.10
999 re¯ections
83 parameters
w = 1/[ꢄ2(Fo2) + (0.1062P)2
+ 0.1100P]
where P = (Fo2 + 2Fc2)/3
(Á/ꢄ)max = 0.015
3
Ê
Áꢅmax = 0.34 e A
3
Ê
0.26 e A
   Â
Urpõ, L., Rodrõguez-Galan, A. & Puiggalõ, J. (1998). Macromol. Chem. Phys.
Áꢅmin
=
199, 1167±1173.
Yamaguchi, K., Matsumura, G., Haga, N. & Shudo, K. (1992). Acta Cryst. C48,
558±559.
H atoms treated by a mixture of
independent and constrained
re®nement
ꢀ
Acta Cryst. (2001). C57, 932±933
Elaine Armelin et al. C8H12N2O6 933