Molecular self assembly of benzene-1,3,5-tricarbonyl phenylalanine

Article abstract of DOI:10.1016/j.molstruc.2011.09.006

Benzene-1,3,5-tricarboxylic acid derivatives with amino acids have a strong tendency to aggregate in solution. In the present communication we report a detailed study of the self assembly of these derivatives containing Phe and Val. Intermolecular hydrogen bonding, π?π and weak C-H?X (X = π, O, N) interactions are involved in the process of molecular assembly.

Full text of DOI:10.1016/j.molstruc.2011.09.006

Journal of Molecular Structure 1006 (2011) 180–184
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Molecular self assembly of benzene-1,3,5-tricarbonyl phenylalanine
⇑
Gannoju Srinivasulu, Balasubramanian Sridhar, Krishnan Ravi Kumar , Bojja Sreedhar, Venna Ramesh,
Ragampeta Srinivas, Ajit C. Kunwar
⇑
Indian Institute of Chemical Technology (CSIR), Hyderabad 500 007, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 20 July 2011
Received in revised form 2 September 2011
Accepted 2 September 2011
Available online 21 September 2011
Benzene-1,3,5-tricarboxylic acid derivatives with amino acids have a strong tendency to aggregate in
solution. In the present communication we report a detailed study of the self assembly of these deriva-
tives containing Phe and Val. Intermolecular hydrogen bonding,
interactions are involved in the process of molecular assembly.
pꢀ ꢀ ꢀp
and weak C–Hꢀ ꢀ ꢀX (X =
p, O, N)
Ó 2011 Elsevier B.V. All rights reserved.
Keywords:
Molecular self assembly
H-bonding
p–
p
Stacking
CH–X ( , O, N) interactions
p
1. Introduction
presence of the benzyl group (Phe group) may result in additional
interactions and favor aggregation whereas H-bonding may
p–p
Self-assembled symmetric molecules, because of their ability to
form nano sized architectures with stable and compact conforma-
tions, serve as important building blocks in materials science and
biology [1]. The formation of stable conformers in these molecules
is governed primarily by secondary interactions like: hydrogen
have a minor influence. In order to discern the role of these inter-
actions in detail, we have investigated Phe and Val derivative of
TMA containing only the methoxy protecting group at the C termi-
nus (2 and 3) (Fig. 1). It was surprising that instead of the parallel
arrangement with infinite
p–p stacking, along with H-bonds ob-
bonding (H-bond), hydrophobic, hydrophilic, electrostatic,
p–p
served by Banerjee et al. [7a], in our studies, carboxamide 2 con-
and CH– interactions. A variety of these structures are known,
p
tains an edge to edge supramolecular self assembly with H-
which contain strong (self-complementary) and unidirectional
intermolecular interactions to arrange into multi-dimensional
self-assembled architectures [2]. Benzene-1,3,5-tricarboxylic acid
(trimesic acid, TMA) (1) derivatives represent an interesting class
of compounds, displaying well-defined assemblies in the solution
as well as in solid state. Molecules derived from TMA have been
studied in detail as organogelators [3], liquid crystals [4], nucleat-
ing agents for isotactic polypropylene [5] and nanostructured
materials [6].
bonding along with the
Hꢀ ꢀ ꢀN interactions in solid state.
p
ꢀ ꢀ ꢀ
p
, weak C–Hꢀ ꢀ ꢀ , C–Hꢀ ꢀ ꢀO and C–
p
Compounds 2 and 3, prepared from commercially available
benzene 1,3,5-tricarbonylchloride, were obtained as white solid.
Methanol/water system was used to get single crystals of 2. The
self assembly was studied in detail by NMR including the DOSY
(diffusion-ordered NMR spectroscopy) experiments, X-ray, TEM
(Transmission Electron Microscope) and Mass Spectral analysis.
For 2, only one set of signals in 1H NMR in non-polar solvent
CDCl3 indicates that it retains 3-fold symmetry in solution. The
information on the H-bonding has been derived from the temper-
Several X-ray structures of TMA derivatives have been reported
[7]. Banerjee et al. [7a], in a rather interesting study on TMA deriv-
atives of Val and Leu, showed a novel triple helical assembly stabi-
ature coefficients of the chemical shifts (
Dd/DT). Large magnitudes
lized by both an array of
p–p
stacking and H-bonds. However,
of Dd/DT, in non-polar solvent like CDCl3, have generally been used
achiral Aib containing derivatives displayed non-helical nanofi-
brils. In yet another study, de Loos et al. [3d] synthesized TMA
derivatives containing a phenylalanine, having a long chain hydro-
carbon as the carboxyl protecting group. They concluded that the
to indicate the involvement of amide protons in intermolecular H-
bonding, which readily break on heating [8]. Thus for the amide
protons
D
d/D
T = ꢁ10.0 ppb/K, imply their participation in inter-
molecular H-bonding. Changing the solute concentration in the
range 0.03–30 mg/0.6 mL, displayed large change in chemical
shifts of amide protons (Fig. 2), further confirming the presence
of molecular association [8]. Chemical shift of the central and
Phe aromatic protons also display modest change (ꢂ0.12 ppm) as
⇑
Corresponding authors. Tel.: +91 40 27193976; fax: +91 40 27193108.
E-mail addresses: ravikumar@iict.res.in (K. Ravi Kumar), kunwar@iict.res.in (A.C.
Kunwar).
0022-2860/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2011.09.006

G. Srinivasulu et al. / Journal of Molecular Structure 1006 (2011) 180–184
181
MeO
R
HO
O
O
HN
O
2. R = CH2Ph (*R)
O
O
OH
H
N
O
3. R = CH(CH3)2 (*S)
*
OMe
OH
O
R
NH
R
O
*
1
O
MeO
Fig. 1. Chemical structure of trimesic acid (1). Phe (2) and Val (3) derivatives of trimesic acid.
8.0
7.6
7.2
6.8
8.0
7.6
7.2
6.8
NH
Ar-H
Ar-H
NH
0.1
1
10
-40 -20
0
20
40
Concentration in mg/0.6 mL CDCl3
Temperature in °C
Fig. 2. Concentration and temperature dependent amide proton chemical shifts of compound 2 in CDCl3.
Fig. 3. TEM images of 2 at varying concentration in methanol–water (1:1). (a) With 2 mg/mL along with the SAED image (inset) and (b) with 4 mg/mL.
a function of concentration, which suggests that
p
ꢀ ꢀ ꢀ
p
and C–Hꢀ ꢀ ꢀ
p
Table 1
Diffusion constants (m2/s) and the molecular mass (Dalton) of the molecular
interactions also play a role in the molecular self assembly. We
therefore, also synthesized the Val derivative (3), and interestingly
found the behavior very similar to that for 2 in the NMR studies.
Accordingly we conclude that these molecules self assemble in
assembly of compound 2 at different concentrations in CDCl3.
Concentration
(D1) Ar–H
(Dref) TMS
Dref/D1
Molecular mass
(3.6 mM)
(120 mM)
5.7 ꢃ 10ꢁ10
1.9 ꢃ 10ꢁ9
3.33
4.35
3300
7300
CDCl3 by forming intermolecular H-bonding and p–p interactions.
3.9 ꢃ 10ꢁ10
1.7 ꢃ 10ꢁ9
For Transmission Electron Microscope (TEM) analysis, two solu-
tions with 2 mg (a), and 4 mg (b) of compound 2 in 1 mL metha-
nol–water (1:1) were prepared with continuous sonication for
5 min. In sample (a) (2 mg/mL), crystalline nature was evident
with particles of about 1 lm, which is supported by Selected Area
Electron Diffraction (SAED) image (inset in Fig. 3a). For sample (b)
(4 mg/mL) on the other hand, nanofibers with thickness of about
100 nm and lengths in the range of about 10 lm (Fig. 3b) were ob-
served. This behavior is in variance with that observed by Banerjee
et al. [7a], with Val and Leu derivatives, where triple helical prop-
agation was noticed. The achiral Aib derivatives, however, dis-
played assemblies similar to those for 2.
as internal standard [9]. The hydrodynamic radius of the molecular
cluster was calculated using Stokes–Einstein Eq. (1), under the
assumption of a spherical shape for the assembly (Table 1), where
M1 and Mref (88 for TMS) is the molecular weight of the aggregates
and the internal reference compound (TMS), respectively and D1
and Dref is the diffusion coefficient of the aggregates and reference
compound. It is noticed that while the solution with 3.6 mM con-
centration, appears to have an assembly of about 5 molecules,
the 120 mM solution show the presence of larger aggregates con-
taining about 10 molecules.
More evidences for the self assembly of these molecules was
obtained by concentration dependent self diffusion coefficient (D)
measurements by DOSY experiment in CDCl3 solution using TMS
ꢀ
ꢁ
3
M1
Mref
Dref
D1
¼
ð1Þ

182
G. Srinivasulu et al. / Journal of Molecular Structure 1006 (2011) 180–184
A
D
C
B
(a)
(b)
Fig. 4. Crystal structure and atom labeling of 2 (a). H-bonding pattern in crystal lattice (b), for the clarity, Phe side chain and methyl ester have been removed.
Fig. 5. Superposition of the molecular conformation of four independent molecules (a). H atoms were omitted for clarity. Types of conformations observed in crystal lattice
(b).
Single crystal X-ray diffraction studies corroborate these findings
very well. Compound 2 was crystallized in MeOH/water solution by
slow evaporation with monoclinic space group P21, with unit cell
dimensions: a = 13.0035(5) Å, b = 17.8752(7) Å, c = 32.4758(12) Å,
b = 91.241(1)°, V = 7546.9(5) Å3, Z = 8, R1 = 0.0895 and Rw = 0.2036.
This was a bit surprising as 3, crystallized from methanol–water sys-
tem, has a 3-fold symmetry in the hexagonal unit cell (space group
P63) [7a].
The asymmetric unit of (2) contains four crystallographically
independent molecules (A–D). Fig. 4a shows the atom labeling pat-
tern and H-bonding pattern in crystal lattice. A superposition of the
molecular conformation of the four molecules in the asymmetric
unit shows a difference in the orientation of the peripheral phenyl
rings. Two types of conformations were observed in the unit cell.
One with tripod like conformation such that the aromatic rings
of three Phe face each other in an orientation perpendicular to
the central aromatic TMA ring and another with the phenyl rings
and TMA in the same plane having a propeller like conformation
(Fig. 5). The crystal structure is stabilized by N–HꢀꢀꢀO hydrogen
bonds which (Table 2) connect the four molecules (Fig. 4b). The
N–HꢀꢀꢀO hydrogen bonds link the molecules into dimer and lead
to the formation of an infinite supramolecular one-dimensional
helical chain along the b-axis (Fig. 6). In addition to the N–HꢀꢀꢀO
H-bonding, aromatic
tions manifest a key role in assembling the supramolecular struc-
ture [10]. Stacking interactions are observed between
p
ꢀ ꢀ ꢀ
p
stacking and C–Hꢀ ꢀ ꢀX (
p, O, N) interac-
pꢀ ꢀ ꢀp
centroids of the rings defined by atoms C1–C6 of molecule B and
atoms C34–C39 of molecule C with centroid–centroid separation

G. Srinivasulu et al. / Journal of Molecular Structure 1006 (2011) 180–184
183
Table 2
self assembled into a supramolecular two-dimensional hydrogen-
bonded network along the (100) plane (Fig. 6). It is also interesting
to mention that atoms N1A and N2B do not act as donors for an NH
hydrogen bond.
In the ESI mass spectral analysis, the observation of larger
aggregate ions up to hexameric assembly, provide emphatic sup-
port for the strong self assembling nature of 2 even in the gaseous
state. (See experimental section and Supporting information).
Hydrogen bonds for 2 [distances in Å and angles in °].
D–Hꢀ ꢀ ꢀA
d(D–H)
d(Hꢀ ꢀ ꢀA)
d(Dꢀ ꢀ ꢀA)
<(DHA)
N2A–H2A1ꢀ ꢀ ꢀO3D
N3A–H3Aꢀ ꢀ ꢀO2D#1
N1B–H1Bꢀ ꢀ ꢀO3C
0.86
0.86
0.86
0.86
0.86
0.86
0.86
0.86
0.86
0.86
0.93
0.93
0.93
0.93
0.93
0.93
0.98
0.98
0.98
0.98
0.96
0.96
0.96
0.96
0.97
0.98
0.98
0.96
0.96
0.93
0.93
0.93
0.98
0.96
0.97
0.93
0.96
0.96
0.96
0.93
2.12
2.14
2.10
2.06
2.03
2.12
2.17
2.16
2.09
2.14
2.50
2.55
2.42
2.57
2.51
2.41
2.48
2.31
2.37
2.50
2.51
2.41
2.26
2.53
2.58
2.33
2.41
2.14
2.51
2.55
2.56
2.59
2.44
2.22
2.75
2.87
2.82
2.89
2.74
2.77
2.964(6)
2.917(6)
2.889(6)
2.911(6)
2.865(6)
2.931(6)
3.006(6)
2.992(6)
2.879(6)
2.946(6)
3.383(6)
3.244(7)
2.743(7)
3.340(6)
3.177(7)
2.737(6)
2.835(8)
3.201(9)
2.788(8)
3.208(8)
3.357(11)
3.04(2)
2.598(12)
2.965(13)
3.371(18)
2.757(7)
3.146(7)
2.55(2)
3.105(12)
3.378(12)
3.483(13)
3.165(9)
2.826(8)
2.577(17)
3.582(8)
3.644(17)
3.544(10)
3.677(10)
3.697(16)
3.585(18)
168
149
151
168
163
157
164
161
152
156
158
132
100
141
129
101
101
152
105
129
147
123
100
108
139
106
131
104
120
149
173
121
103
101
144
142
133
140
173
146
N3B–H3Bꢀ ꢀ ꢀO2C#2
N1C–H1Cꢀ ꢀ ꢀO3B
N2C–H2C1ꢀ ꢀ ꢀO2B#3
N3C–H3Cꢀ ꢀ ꢀO1D
N1D–H1Dꢀ ꢀ ꢀO1A
2. Conclusions
N2D–H2D1ꢀ ꢀ ꢀO2A#4
N3D–H3Dꢀ ꢀ ꢀO1C
In the present work we have studied the molecular self assem-
bly by 1H and DOSY NMR. In X-ray studies we observed self assem-
bly with N–Hꢀ ꢀ ꢀO hydrogen-bonding with edge to edge
C2D–H2Dꢀ ꢀ ꢀO1C
C4A–H4Aꢀ ꢀ ꢀO3D
C4B–H4Bꢀ ꢀ ꢀO1B
C4C–H4Cꢀ ꢀ ꢀO2B#3
C6B–H6Bꢀ ꢀ ꢀO2C#2
C6D–H6Dꢀ ꢀ ꢀO2D
supramolecular helical arrangement along with weak
p p, C–
ꢀ ꢀ ꢀ
Hꢀ ꢀ ꢀ , C–Hꢀ ꢀ ꢀO and C–Hꢀ ꢀ ꢀN interactions in phenylalanine contain-
p
ing analogue.
C8A–H8Aꢀ ꢀ ꢀO1A
C8A–H8Aꢀ ꢀ ꢀO4D
C8B–H8Bꢀ ꢀ ꢀO1B
3. Experimental section
C8B–H8Bꢀ ꢀ ꢀO6B#5
C10A–H10Aꢀ ꢀ ꢀO8A#4
C10C–H10Gꢀ ꢀ ꢀO4A
C10D–H10Jꢀ ꢀ ꢀO4D
C10D–H10Lꢀ ꢀ ꢀO4B#6
C11D–H11Gꢀ ꢀ ꢀO1A
C19A–H19Aꢀ ꢀ ꢀO3A
C19A–H19Aꢀ ꢀ ꢀO8A#6
C21C–H21Iꢀ ꢀ ꢀO6C
C21DC–H21Kꢀ ꢀ ꢀO8C#1
C24B–H24Bꢀ ꢀ ꢀO2C#2
C27C–H27Cꢀ ꢀ ꢀO8B#7
C28D–H28Dꢀ ꢀ ꢀN2D
C30B–H30Bꢀ ꢀ ꢀO2B
C32D–H32Jꢀ ꢀ ꢀO8D
C11A–H11Aꢀ ꢀ ꢀCg11#6
C16A–H16Aꢀ ꢀ ꢀCg4#6
C21D–H21J–Cg1
All the chemicals and reagents were obtained from commercial
sources. The solvents were purified and dried by standard proce-
dures. These compounds were synthesized by reacting methyl es-
ters of Phe and Val amino acid with trimesoylchloride at below
room temperature in DCM under N2 atmosphere. Chemical shifts
are mentioned in parts per million (d) with reference to TMS as
internal standard. All the NMR Spectra were recorded in CDCl3
solution. 1H NMR diffusion measurements were performed by
using stimulated echo sequence with bipolar gradient pulses. Dif-
fusion time (D) was set to 100 ms. The pulsed gradients were incre-
mented from 2% to 95% of the maximum strength 5.35 G/cm in 16
spaced steps with a duration (d/2) of 1.5 ms. Data were acquired at
600 MHz in CDCl3 solution without sample rotation at 30 °C.
Compound 2 was crystallized in methanol/water by slow evap-
oration and X-ray data was collected at room temperature using a
Bruker Smart Apex CCD diffractometer with graphite monochro-
C32C–H32G–Cg5#3
C32D–H32Kꢀ ꢀ ꢀCg10
C38B–H38Bꢀ ꢀ ꢀCg7#5
mated Mo K
a radiation (k = 0.71073 Å) by the x-scan method on
Symmetry transformations used to generate equivalent atoms: #1 ꢁx + 1, y + 1/2,
ꢁz + 1; #2 ꢁx + 1, y + 1/2, ꢁz; #3 ꢁx + 1, y ꢁ 1/2, ꢁz; #4 ꢁx + 1, y ꢁ 1/2, ꢁz + 1; #5
1 + x, y, z; #6 1 ꢁ x, y, z; #7 2 ꢁ x, y ꢁ 1/2, ꢁz; Cg1 – centroid of the C1A–C6A ring;
Cg4 – centroid of the C34A–C39A ring; Cg5 – centroid of the C1B–C6B ring; Cg7 –
centroid of the C23B–C28B ring; Cg10 – centroid of the C12C–C17C ring; Cg11 –
centroid of the C23C–C28C ring.
a crystal of 0.18 ꢃ 0.13 ꢃ 0.05 mm dimensions [11]. Preliminary
lattice parameters and orientation matrices were obtained from
four sets of frames. Unit cell dimensions were determined using
9333 reflections in the range of 2.20° < h < 19.48°.
Integration and scaling of intensity data were accomplished
using the program SAINT [11]. The structures were solved by direct
methods using SHELXS97 [12] and refinement was carried out by
full-matrix least-squares technique using SHELXL97 [12]. Aniso-
tropic displacement parameters were calculated for all non-hydro-
gen atoms. H atoms attached to C and N atoms were positioned
geometrically and treated as riding on their parent C and N atoms,
of 3.641(5) Å and also between the centroids of the rings defined
by atoms C1–C6 of molecule A and atoms C23–C28 of molecule
D at (1 ꢁ x, ½ + y, 1 ꢁ z) with a centroid–centroid distance of
3.647(4) Å. Weak C–Hꢀ ꢀ ꢀO, C–Hꢀ ꢀ ꢀN and C–Hꢀ ꢀ ꢀ
p interactions are
also noticed (Table 2). In the overall crystal packing the molecules
Fig. 6. Infinite one-dimensional helical chain along the b-axis (a) and supramolecular two dimensional H-bonding networks (b). For the clarity, Phe side chain and methyl
ester have been removed.

184
G. Srinivasulu et al. / Journal of Molecular Structure 1006 (2011) 180–184
with C–H = 0.93–0.98 Å and N–H = 0.86 Å and with Uiso(-
H) = 1.5Ueq(C) for methyl H and 1.2Ueq(C, N) for other H atoms.
The methyl groups were allowed to rotate but not to tip. A TWIN
[10001000ꢁ12] card was applied. The anisotropic displacement
parameters of atoms (C11C to C17C) were restrained to be similar
[SIMU instruction in SHELXL97 (Sheldrick, 2008)]. For Transmis-
sion Electron Microscope, samples were taken in MeOH/H2O and
sonicated for 5 min and dried on carbon coated copper grid
(300 mesh) at room temperature for 2 days.
Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.molstruc.2011.09.006.
References
[1] (a) L.J. Prins, D.N. Reinhoudt, P. Timmerman, Angew. Chem. 2446 (2001) 113;
(b) D.J. Hill, M.J. Mio, R.B. Prince, T.S. Hughes, J.S. Moore, Chem. Rev. 3893
(2001) 101;
Compound 2: 0.2 g (1.2 mmol) of H-D-Phe-OH was dissolved in
5 mL of MeOH and added 0.5 mL of SOCl2 at 0 °C and stirred for 6 h.
Solvent was removed under reduced pressure and added 10 mL of
DCM cooled to 0 °C under nitrogen atmosphere and neutralized
with Et3N and 0.08 g (0.3 mmol, 0.25 equiv) of trimesylchloride
was added portion wise and stirred for overnight. Reaction mixture
was diluted with 50 mL of ethyl acetate and washed with saturated
NH4Cl, NaHCO3 and NaCl solutions. The organic layer was dried
with Na2SO4 and solvent was removed under reduced pressure,
resulting residual was purified by column chromatography (ethyl
acetate/hexane) to afford 0.15 g (0.21 mmol, 84% Yield) of 2 as
white solid. 1H NMR (600 MHz, CDCl3): d 8.18 (s, 3H, Ar–H), 7.29
(t, J = 7.0 Hz, 6H, Phe-m), 7.23 (t, J = 7.0 Hz, 3H, Phe-p), 7.17 (d,
J = 7.0 Hz, 6H, Phe-o), 6.96 (d, J = 7.7 Hz, 3H, NH), 5.06 (dt, J = 7.7,
(c) L. Brunsveld, B.J.B. Folmer, E.W. Meijer, R.P. Sijbesma, Chem. Rev. 4071
(2001) 101;
(d) D.T. Bong, T.D. Clark, J.R. Granja, M.R. Ghadiri, Angew. Chem. 1016 (2001)
113; Angew. Chem. Int. Ed. 989 (2001) 40.;
(e) A. Ciferri, Macromol. Rapid Commun. 511 (2002) 23;
(f) L.M. Greig, D. Philp, Chem. Soc. Rev. 287 (2001) 30;
(g) H.M. Keizer, R.P. Sijbesma, Chem. Soc. Rev. 226 (2005) 34;
(h) A.L. Sisson, M.R. Shah, S. Bhosale, S. Matile, Chem. Soc. Rev. 1269 (2006) 35;
(i) K. Sada, M. Takeuchi, N. Fujita, M. Numata, S. Shinkai, Chem. Soc. Rev. 415
(2007) 36.
[2] (a) J.A. Zerkowski, C.T. Seto, D.A. Wierda, G.M. Whitesides, J. Am. Chem. Soc.
9025 (1990) 112;
(b) L.J. Prins, F. de Jong, P. Timmerman, D.N. Reinhoudt, Nature 181 (2000) 408;
(c) G. Gottarelli, G. Proni, G.P. Spada, S. Bonazzi, A. Garbesi, F. Ciuchi, P. Mariani,
Biopolymers 561 (1997) 42;
(d) F.H. Beijer, R.P. Sijbesma, H. Kooijman, A.L. Spek, E.W. Meijer, J. Am. Chem.
Soc. 6761 (1998) 120.
[3] (a) S.J. Lee, C.R. Park, J.Y. Chang, Langmuir 9513 (2004) 20;
(b) A. Sakamoto, D. Ogata, T. Shikata, K. Hanabusa, Macromolecules 8983
(2005) 38;
6.3 Hz, 3H, CaH), 3.76 (s, 9H, OMe), 3.28 (dd, J = 6.3, 13.9 Hz, 3H,
CbH), 3.19 (dd, J = 6.3, 13.9 Hz, 3H, CbH0); 13C NMR (100 MHz,
CDCl3): d 172.4, 165.2, 136.0, 134.5, 129.1, 128.6, 128.5, 127.2,
54.2, 52.5, 37.8; ESI MS m/z (%): 694.1 (8, [M + H]+), 1062.8 (12,
(c) P. Terech, R.G. Weiss, Chem. Rev. 3133 (1997) 97;
(d) M. de Loos, J.H. van Esch, R.M. Kellogg, B.L. Feringa, Tetrahedron 7285
(2007) 63.
[4] (a) Y. Matsunaga, Y. Nakayasu, S. Sakai, M. Yonenaga, Mol. Cryst. Liq. Cryst. 327
(1986) 141;
) )
[3 M + 2Na]2+ and 1409.1 (100, [2 M + Na]+); IR (KBr, cmꢁ1
3227, 3059, 3032, 2950, 2924, 2852, 1746, 1641, 1546, 1437,
1220, 744, 700; MP 198–203 °C.
(b) A.R.A. Palmans, J.A.J.M. Vekemans, H. Fischer, R.A. Hikmet, E.W. Meijer,
Chem. Eur. J. 300 (1997) 3;
(c) J.Y. Chang, J.R. Yeon, Y.S. Shin, M.J. Han, S.-K. Hong, Chem. Mater. 1076
(2000) 12;
(d) M.H.C.J. Van Houtem, R. Martín-Rapún, J.A.J.M. Vekemans, E.W. Meijer,
Chem. Eur. J. 2258 (2010) 16;
(e) C.F.C. Fitié, W.S.C. Roelofs, M. Kemerink, R.P. Sijbesma, J. Am. Chem. Soc.
6892 (2010) 132.
Compound 3: 0.12 g (1.02 mmol) of H-L-Val-OH was taken in
5 mL of MeOH, cooled to 0 °C and added 1 mL of SOCl2 slowly
and stirred for 6 h. Solvent was evaporated under vacuum. The
resulting H-Val-OMe. HCl salt was neutralized with DIPEA in
DCM at 0 °C and 0.065 g (0.25 mmol) of trimesoylchloride was
added slowly under nitrogen atmosphere and stirred for overnight.
Solvent was evaporated and residue dissolved in 100 mL ethyl ace-
tate and washed with saturated NH4Cl, NaHCO3 and NaCl solutions
each two times. Organic layer dried with Na2SO4 and evaporated.
Residue obtained was purified by column chromatography (ethyl
acetate/hexane) to afford 3 (0.09 g, 0.16 mmol, 64% Yield) as white
solid. 1H NMR (400 MHz, CDCl3): d 8.42 (s, 3H, Ar–H), 6.90 (d,
[5] N. Mohmeyer, N. Behrendt, X. Zhang, P. Smith, V. Altstdt, G.M. Sessler, H.-W.
Schmidt, Polymer 1612 (2007) 48.
[6] (a) J. Roosma, T. Mes, P. Leclre, A.R.A. Palmans, E.W. Meijer, J. Am. Chem. Soc.
1120 (2008) 130;
(b) C.F.C. Fitie, I. Tomatsu, D. Byelov, W.H. de Jeu, R.P. Sijbesma, Chem. Mater.
2394 (2008) 20;
(c) R.V. Ulijn, A.M. Smith, Chem. Soc. Rev. 664 (2008) 37;
(d) R. Fairman, K.S. Åkerfeldt, Curr. Opin. Struct. Biol. 453 (2005) 15.
[7] (a) P.P. Bose, M.G.B. Drew, A.K. Dasa, A. Banerjee, Chem. Commun. 3196
(2006);
(b) L. Rajput, V.V. Chernyshev, K. Bindra, Chem. Commun. 6530 (2010) 46;
(c) M.P. Lightfoot, F.S. Mair, R.G. Pritchard, J.E. Warren, Chem. Commun. 1945
(1999);
(d) P.J.M. Stals, M.M.J. Smulders, R.M. Rapún, A.R.A. Palmans, E.W. Meijer,
Chem. Eur. J. 2071 (2009) 15;
J = 8.6 Hz, 3H, NH), 4.78 (dd, J = 8.6, 5.0 Hz, 3H, C
OMe), 2.29 (m, 3H, CbH), 1.03 (d, J = 6.5 Hz, 9H, C
a
H), 3.79 (s, 9H,
c
Me), 1.01 (d,
J = 6.5 Hz, 9H, Cc0Me); 13C NMR (100 MHz, CDCl3): d 172.3, 165.5,
134.8, 128.7, 57.9, 52.3, 31.5, 19.0, 18.1; ESI MS m/z, (%): 550.1
(10, [M + H]+), 847.0 (5, [3 M + 2Na]2+), 1121.3 (100, [2 M + Na]+),
1137.1 (30, [6 M + 5Na]3+), 1669.7 (35, [6 M + 2Na]2+); IR (KBr,
cmꢁ1): 3236, 3056, 2964, 1748, 1642, 1548, 1463, 1440, 1310,
1270, 1202, 1152, 691; MP 277–282 °C.
(e) J.J. van Gorp, J.A.J.M. Vekemans, E.W. Meijer, J. Am. Chem. Soc. 14759 (2002)
124;
(f) R. Kannappan, D.M. Tooke, A.L. Spek, J. Reedijk, J. Mol. Struct. 55 (2005) 751;
(g) D. Ranganathan, S. Kurur, R. Gilardi, I.L. Karle, Biopolymers 289 (2000) 54.
[8] (a) E.S. Stevens, N. Sugavara, G.M. Bonora, C. Toniolo, J. Am. Chem. Soc. 7048
(1980) 102;
(b) M. Iqbal, P. Balaram, Biopolymers 1427 (1982) 21;
(c) A. Banerjee, S. Raghothama, P. Balaram, J. Chem. Soc., Perkin Trans. 2 2087
(1997).
Supporting information
[9] (a) E.J. Cabrita, S. Berger, Magn. Reson. Chem. S142 (2001) 39;
(b) L. Orosz, G. Batta, S. Kéki, M. Nagy, G. Deáka, M. Zsuga, Carbohydr. Res. 1323
(2007) 342;
(c) C.A. Christopher, D.J. Harris, J. Magn. Reson. 179 (2007) 185.
[10] G.R. Desiraju, Angew. Chem. Int. Ed. 2311 (1995) 34.
[11] Bruker, SAINT (Version 6.28a) & SMART (Version 5.625), Bruker AXS Inc.,
Madison, Wisconsin, USA, 2001.
CCDC 831653 contains the supplementary crystallographic data
for this paper. These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk./conts/retrieving.html (or from the Cam-
bridge Crystallographic Data Centre, 12, Union Road, Cambridge
CB2 1E2, UK; fax: +44 1223 336033). NMR spectra (1H, 13C and DO-
SEY), ESI MS spectra are also available in the supporting
information.
[12] G.M. Sheldrick, Acta Crystallogr. 112 (2008) A64.
Acknowledgements
G. Srinivasulu and V. Ramesh are thankful to CSIR, New Delhi,
for financial support.