Cu(OTf)2 catalyzed three component reaction: Efficient synthesis of spiro[indoline-3,4′-pyrano[3,2-b]pyran derivatives and their anticancer potency towards A549 human lung cancer cell lines

Article abstract of DOI:10.1016/j.bmcl.2013.02.086

Cu(OTf)₂ catalyzed efficient synthesis of spiropyrano[3,2-b] pyran-4(8H)-ones is accomplished via one-pot three component reaction between isatin, kojic acid and active methylenes. This synthetic protocol is operationally simple and affords product with good to excellent yields at a short reaction time. The synthesized compounds were evaluated for their tumor cell growth inhibitory activity against the human lung cancer cell line (A549) and found that 13 compounds exhibited moderate to good anticancer potency. Molecular docking studies were performed for all the synthesized compounds and the results showed that compound 4e showed greater affinity for anaplastic lymphoma kinase (ALK) receptor.

Full text of DOI:10.1016/j.bmcl.2013.02.086

Bioorganic & Medicinal Chemistry Letters 23 (2013) 2708–2713
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Cu(OTf)2 catalyzed three component reaction: Efficient synthesis
of spiro[indoline-3,40-pyrano[3,2-b]pyran derivatives and their
anticancer potency towards A549 human lung cancer cell lines
K. Parthasarathy a,b, C. Praveen a, C. Balachandran c, P. Senthil kumar d, S. Ignacimuthu c, P. T. Perumal a,
⇑
a Organic Chemistry Division, Central Leather Research Institute (CSIR), Adyar, Chennai 600 020, India
b Analytical Research & Development, Orchid Chemicals & Pharmaceuticals Ltd, Research & Development Centre, Shozanganallur, Chennai 600 119, India
c Division of Cancer Biology, Entomology Research Institute, Loyola College, Chennai 600 034, India
d Department of Bioinformatics, Orchid Chemicals & Pharmaceuticals Ltd, Research & Development Centre, Shozanganallur, Chennai 600 119, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Cu(OTf)2 catalyzed efficient synthesis of spiropyrano[3,2-b]pyran-4(8H)-ones is accomplished via one-
pot three component reaction between isatin, kojic acid and active methylenes. This synthetic protocol
is operationally simple and affords product with good to excellent yields at a short reaction time. The syn-
thesized compounds were evaluated for their tumor cell growth inhibitory activity against the human
lung cancer cell line (A549) and found that 13 compounds exhibited moderate to good anticancer
potency. Molecular docking studies were performed for all the synthesized compounds and the results
showed that compound 4e showed greater affinity for anaplastic lymphoma kinase (ALK) receptor.
Ó 2013 Elsevier Ltd. All rights reserved.
Received 18 January 2013
Revised 13 February 2013
Accepted 15 February 2013
Available online 27 February 2013
Keywords:
Three component reaction
Cu(OTf)2
Spiro-heterocycles
A549 lung cancer
Molecular docking
Lung cancer is the most frequent cause of cancer-related death
and accounts for more than a million deaths yearly worldwide
with non-small cell lung cancer (NSCLC) accounting for 75–85%
of lung cancer.1 Molecular studies of lung cancer have provided
new avenues for early diagnosis and therapeutic strategies, how-
ever, certain patients are still plagued by rapid disease recurrence
and progression and there has been no significant improvement in
their overall survival. Therefore, it remains a disease with poor
prognosis and the primary cause of cancer-related deaths in both
men and women despite recent advances made in drug develop-
ment.2 The development or presence of resistance to chemothera-
peutic agents is a major obstacle to the effective treatment of lung
cancer. Therefore, it seems necessary to identify and develop new
molecular entities of improved efficacy and resistance to comple-
ment the present chemotherapeutic strategies.
kojic acid exhibits free radical scavenging and tyrosinase inhibiting
activity.5 On the other hand, spiro-oxindole system is the core
structure of many bio-active natural alkaloids such as horsifiline,
spirotryprostatine, alstonisine, welwitindolinone A, coerulescine,
pteropodine and elacomine.6 They are also present as sub-struc-
ture in pharmacological agents and act as modulators of musca-
rinic M1 and 5-HT2 receptors and potent non peptide inhibitors
of p53-MDM2 interaction and microtubule assembly.7 Recently,
we have initiated a research program on the synthesis of a series
of novel spiro-oxindoles8 and/or screened them for their biocidal
profile.9 Inspired by the synthetic feasibility of spiro-oxindole10
and kojic acid derivatives11 it was thought worthwhile to fuse both
these scaffolds as a single molecular entity in view of enhanced
biological activity. We hypothesized such hybrid-heterocycles12
might lead to an interesting class of compounds useful for the
structure–activity relationship (SAR) studies. In 2004, Litvinov
et al. have reported the amine catalyzed synthesis of similar com-
pounds.13 The scope described in this protocol was very limited to
a specific substrate, which prompted us to investigate further this
kind of transformation with particular emphasis on performing
with a Lewis acid catalyst. Toward these ends, we herein report
the synthesis of kojic acid tethered spiro-oxindoles via Cu(OTf)2
catalyzed three component reaction and the anticancer potency
of these compounds against A549 human lung cancer cell lines.
5-Hydroxy-2-(hydroxymethyl)-4H-pyran-4-one
commonly
known as kojic acid is produced from carbohydrate sources in an
aerobic process by various fungi and bacteria, such as Aspergillus
and Pencillium.3 The derivatives of kojic acid are common
occurrence in a variety of natural and semi-synthetic products
with diverse and compelling pharmacological activities.4 Due to
its
c-pyranone structure that contains an enolic hydroxyl group,
⇑
Corresponding author. Tel.: +91 44 24913289; fax: +91 44 24911589.
E-mail address: ptperumal@gmail.com (P.T. Perumal).
0960-894X/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmcl.2013.02.086

K. Parthasarathy et al. / Bioorg. Med. Chem. Lett. 23 (2013) 2708–2713
2709
H2N
Z
Our study began with isatin 1a, malononitrile 2a and kojic acid
O
O
2
O
Z
CN
3. The choice of the catalyst played a crucial role and the use of late
transition metal catalysts was at the center of our study. In the
course of our work on the applications of copper and zinc catalysts
in various heterocycle syntheses,14 we thought they will be cata-
lytically effective for the preparation of targeted spiro-compounds.
Knowledge gained from our previous work allowed us to arrive
quickly at optimal reaction conditions (Table 1); in fact Cu(OTf)2
at a loading of 5 mol % in refluxing dichloroethane emerged as
the reaction conditions of choice, giving the product 4a in an 93%
yield (entry 6). The use of anhydrous CuCl, CuCl2, CuBr2, ZnCl2
and Zn(NTf)2 (entries 1–5) was much less effective in this transfor-
mation. Finally, Zn(OTf)2 resulted in product formation in moder-
ate yield (entry 7). Since 5 mol % of Cu(OTf)2 was optimal for the
preferred transformation, we set out to investigate the scope of
other substrates (Scheme 1, Table 2).15
Gratifyingly, isatins with electron-rich and electron-poor sub-
stituent underwent the desired reaction in good to excellent yield.
As seen from Table 2, there was a wide tolerance for several isatins
varying in C5 and N-substitution. Other reaction partners such as
malonitrile, ethyl cyanoacetate and methyl cyanoacetate per-
formed with equal aplomb. It is pertinent to note that, substrates
possessing alkynes did not undergo isomerization to the corre-
sponding allenyl product.16 Interestingly, this copper-catalyzed
transformation is not limited to mono-systems. As illustrated in
Scheme 2, we have been able to apply this chemistry to the synthe-
sis of complex bis-spiroxindole system. Thus, treatment of bis-isat-
in (1.0 mmoL) with malononitrile (2.0 mmoL) and kojic acid
(2.0 mmoL) under our standard reaction conditions produced the
corresponding product in 68% yield. The structures of all the prod-
ucts were confirmed by spectral data (FTIR, 1H NMR, 13C NMR and
MS) and elemental analyses. For an illustrative example, the IR
spectrum of compound 4k showed broad peaks at 3400–3300 cm
O
R1
R1
5 mol% Cu(OTf)2
(CH2)2Cl2 / reflux
OH
O
O
+
O
N
N
R
HO
4
O
R
1
3
OH
Scheme 1.
Table 2
Cu(OTf)2 catalyzed synthesis of spiroxindoles 4a–4s
Entry
R
R1
Z
Time (min)
Producta
Yieldb (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
H
H
H
H
H
F
Cl
Br
H
H
H
H
H
CN
CN
CN
CN
CN
CN
CN
CN
30
20
20
25
40
45
45
45
35
25
25
30
45
45
45
30
25
30
35
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
4n
4o
4p
4q
4r
4s
93
91
89
90
84
80
82
85
89
87
86
90
85
81
77
87
91
88
81
Me
Allyl
Propargyl
Bn
H
H
H
H
COOEt
COOEt
COOEt
COOEt
COOEt
COOEt
COOEt
COOMe
COOMe
COOMe
COOMe
F
Cl
Br
Me
H
H
Me
Allyl
H
H
H
H
H
Bn
NO2
Me
H
a
All products were characterized by IR, NMR and mass.
Isolated yield.
b
ꢀ1
revealed the presence of –NH2, –NH and –OH functionalities.
taken for granted at this juncture. The nitrophilic Cu(OTf)2 coordi-
nates with the cyano group of I leading to intermediate II. Subse-
quent C-alkylation of kojic acid 3 with electron deficient C@C
double bond leads to intermediate III and IV. Thorpe-Ziegler type
reaction of intermediate IV (nucleophilic attack of enolic hydroxyl
to the copper-activated cyano group)18 results in the cyclized oxo-
nium intermediate V. The later upon deprotonation leads to imin-
ium intermediate VI and finally proto-decupration of intermediate
VI affords the spiroxindole product 4.
Cytotoxicity of all the synthesized compounds against human
lung cancer cell lines (A549) was determined by MTT assay.
Growth of lung cancer cells was measured by the ability of living
cells to reduce the yellow MTT to purple formazan products.19
A549 cancer cell lines were cultivated at 37 °C in an atmosphere
of 5% CO2, 95% air and 100% relative humidity in Dulbecco’s
modified Eagle’s minimal medium (DMEM) supplemented with
The stretching bands at 1732 and 1643 cmꢀ1 correspond to ester
and amide carbonyl groups, respectively. The 1H NMR spectrum
of 4k recorded in DMSO-d6, showed fifteen protons. The broad sig-
nals at dH 8.16 ppm and dH 10.75 ppm were assigned to –NH2 and –
NH protons (D2O exchangeable), respectively. In 13C NMR spec-
trum, a less intense peak at dC 51.4 ppm indicates the presence
of a spiro-carbon and a peak at dC 177.1 ppm corresponds to an
amide carbonyl carbon. Also, DEPT-135 and 2D chemical shift cor-
relation experiments were used to support this observation. MS
data was acquired in the positive ionization FIA mode, exhibited
two isotopic peaks at m/z = 417 [35MCl+H]+, 419 [37MCl+H]+ in 3:1
ratio. Finally, single crystal X-ray diffraction studies unequivocally
confirmed the structure of the product 4k (Fig. 1).17
A tentative mechanistic description for this Cu-catalyzed three
component reaction was proposed (Scheme 3). Mechanistically,
the formation of isatylidene malononitrile I from isatin 1 and mal-
ononitrile 2 involves typical Knoevenagel condensation and can be
10% Fetal Bovine Serum (FBS) and 2.0 mM
antibiotics (about 100 IU/mL of penicillin, 100
L
-glutamine along with
g/mL of streptomy-
l
cin) with the pH adjusted to 7.2. Cells (5 ꢁ 105) were trypsinized
for the passage into the well plate and were seeded in 96 well
plates containing medium with different concentrations such as
Table 1
Screening of Lewis acidsab
12.5, 25, 50, 100, 150 and 200
to the surface of well plates. After various durations of cultivation,
the solution in the medium was removed. An aliquot of 100 L of
lg/mL and were allowed to adhere
Entry
Catalyst
Time (min)
Yieldc (%)
l
1
2
3
4
5
6
7
CuCl
CuCl2
CuBr2
ZnCl2
Zn(NTf)2
Cu(OTf)2
Zn(OTf)2
30
30
30
30
30
30
30
—
10
27
30
22
93
52
medium containing 1 mg/mL of 3-(4,5-dimethylthiazol-2-yl)-2,5-
diphenyl-tetrazolium bromide (MTT) was loaded to the plate. Incu-
bation at 37 °C for 4 h allowed reduction of MTT by mitochondrial
dehydrogenase to an insoluble formazan product. Well contents
were removed and the formazan product was solubilised by
addition of 100 lL of DMSO, which led to the formation of purple
a
Yields of 4a using different Lewis acids.
All reactions were carried out using 1.0 mmoL of isatin 1a, malononitrile 2a and
b
colour. The amount of formazan product is directly proportional
to the number of living cells. Absorbance of each well was read
on ELISA reader at 540 nm. From the absorbance % of inhibition
kojic acid 3, catalyst (5 mol %) and dichloroethane (2 mL).
c
Isolated yield.

2710
K. Parthasarathy et al. / Bioorg. Med. Chem. Lett. 23 (2013) 2708–2713
H2N
O
O
NC
O
O
O
O
OH
OH
HO
5 mol% Cu(OTf)2
N
O
O
NC
CN
+
+
OH
N
4
O
(CH2)2Cl2 / reflux
68 %
2a
(2.0 mmoL)
3
1
N
(2.0 mmoL)
O
NC
O
(1.0 mmoL)
N
O
H2N
O
O
Scheme 2.
Table 3
IC50 and FEB values of compounds 4a–s
Entry
Compounds
IC50
52.8
(l
M)
FEBa (kcal/mol)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
ꢀ16
17
18
19
20
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
4n
4o
ꢀ4.68
ꢀ5.12
ꢀ5.19
ꢀ4.91
ꢀ5.99
ꢀ4.84
ꢀ5.12
ꢀ4.18
ꢀ5.18
ꢀ4.09
ꢀ4.50
ꢀ5.17
ꢀ4.48
ꢀ4.96
ꢀ4.59
ꢀ5.23
ꢀ5.01
ꢀ5.04
ꢀ4.97
ꢀ7.58
>200
51.4
>200
51.1
59.4
>200
>200
>200
>200
53.1
52.8
52.9
55.8
54.6
56.2
55.9
62.8
55.1
—
4p
4q
4r
4s
Crizotinibb
a
Free energy of binding.
Reference drug.
b
Figure 1. ORTEP diagram of compound 4k.
half maximal inhibitory concentration (IC50 value) was determined
averaged from three replicate experiments using SPSS 11.5 soft-
ware. Analysis of the screening data (Table 3) revealed that com-
was calculated by using the formula, % of inhibition = Ac ꢀ At/
Ac ꢁ 100, where Ac is the mean absorbance of control and At is that
of test. From the results nonlinear regression graph was plotted be-
pounds 4e (IC50 = 51.1
l
M) and 4c (IC50 = 51.4 lM) possessing
tween % cell growth inhibition and log10 concentration (
lM). The
Cu(OTf)2
Z
Z
N
CN
O
R1
R1
R1
Cu(OTf)2
Z
O
O
OH
+
O
O
O
CN
N
N
R
N
R
Kojic acid
HO
3
II
I
2
R
1
Cu(OTf)2
Cu(OTf)2
OH
Z
Z
N
C
N
C
R1
R1
O
O
O
O
OH
O
HO
O
N
R
IV
N
R
O
H+
III
Cu(OTf)2
Cu(OTf)2
H+
H2N
Z
O
O
HN
N
O
O
O
O
H
Z
R1
Z
R1
R1
O
O
OH
-Cu(OTf)2
O
O
O
O
OH
OH
N
VI
N
R
N
R
4
R
V
Scheme 3.

K. Parthasarathy et al. / Bioorg. Med. Chem. Lett. 23 (2013) 2708–2713
2711
NꢀMe, 30-CN and 5-Cl, 30-CN groups, respectively, exhibited max-
imum cytotoxicity. A slight loss of activity was observed in com-
pounds 4a, 4k–m and appeared to be the second most active
series with IC50 values falling between 52.8 and 53.1 lM. A moder-
ate inhibitory potency was observed in compounds 4n–q and 4s
(IC50 = 54.6–55.9). A much reduced activity was exhibited by com-
pounds 4f and 4r with IC50 values of 59.4 and 62.8
tively. However, compounds 4b, 4d, 4g–j emerged as the least
active series, exhibiting IC50 values of >200 M.
lM, respec-
l
To investigate the potential binding mode of inhibitors, all the
compounds were subjected to molecular docking using the AUTO-
DOCK 1.5.4 docking program. Because of the critical roles of aberrant
signaling in cancer, anaplastic lymphoma kinase (ALK) receptor is
an attractive oncology target for therapeutic intervention. To this
end, the X-ray crystal structure of ALK in complex with crizotinib
was downloaded from the protein data bank (PDBID: 2XP2) and
was used for the docking study.20 Ligand 2D structures were drawn
using ChemDraw Ultra 7.0 (ChemOffice 2002). Chem3D Ultra 7.0
was used to convert 2D structure into 3D and the energy mini-
mized using semi-empirical AM1 method. Minimize energy to
minimum RMS gradient of 0.100 was set in each iteration. All
structures were saved as .pdb file format for input to AutoDock-
Tools (ADT) version 1.5.4.21a All the ligand structures were then
saved in PDBQT file format, for input into AUTODOCK version 1.5.4.21b
Figure 2. Molecular docking of bound and docked crizotinib in ALK, where the
docked ligand was discriminated by showing two hydrogen bond interactions.
Figure 3. Docking of the most active compound 4e (FEB = ꢀ5.99 kcal/mol) in ALK (dotted lines showing hydrogen bonding interactions).
Figure 4. Docking of the least active compound 4h (FEB = ꢀ4.18 kcal/mol) in ALK (dotted lines showing hydrogen bonding interactions).

2712
K. Parthasarathy et al. / Bioorg. Med. Chem. Lett. 23 (2013) 2708–2713
Figure 5. Docking of the intermediary active compound 4n (FEB = ꢀ4.96 kcal/mol) in ALK (dotted lines showing hydrogen bonding interactions).
For the molecular docking study, protein structure was ob-
with a calculated binding energy of ꢀ5.99 kcal/mol. The least bind-
ing energy was exhibited by compound 4h with a binding energy
of ꢀ4.18 kcal/mol. The intermediary active compound 4n showed
ꢀ4.96 kcal/mol of binding energy. The binding interactions of these
compounds were shown, respectively in Figures 3–5.
In conclusion, we have demonstrated the catalytic efficiency of
Cu(OTf)2 for the three component reaction between isatin, malon-
onitrile and kojic acid. This method utilizes catalytic quantity of
Cu(OTf)2 in comparision with harsh and stoichiometric amine
bases. Evaluation of in vitro anticancer properties towards A549
cancer cell lines revealed that thirteen compounds exhibited good
to moderate cytotoxicity, out of which, two compounds 4e and 4c
exhibited good anticancer potency with an IC50 value of 51.1 and
tained from the Protein Data Bank; the ALK structure PDB ID was
2XP2. The co crystallized ligand (crizotinib) in the ALK structure
was removed. For the protein structure, all hydrogen atoms were
added, lower occupancy residue structures were deleted, and any
incomplete side chains were replaced using the ADT version
1.5.4. Further ADT was used to remove crystal water, added Gagtei-
ger charges to each atom, and merged the non-polar hydrogen
atoms to the protein structure. The distance between donor and
acceptor atoms that form a hydrogen bond was defined as 1.9 Å
with a tolerance of 0.5 Å, and the acceptor–hydrogen-donor angle
was not less than 120°. The structures were then saved in PDBQT
file format, for input into AUTODOCK version 1.5.4. A grid box with
dimension of 40 ꢁ 40 ꢁ 40 Å3 and was centred on 29.608, 47.370,
9.753 was created around the binding site of crizotinib on ALK pro-
tein using AutoDockTools. The centre of the box was set at crizoti-
nib and grid energy calculations were carried out. For the AUTODOCK
docking calculation, default parameters were used and 50 docked
conformations were generated for each compound. In order to ver-
ify reproducibility of the docking calculations, the bound ligand
(crizotinib) was extracted from the complexes and submitted for
one-ligand run calculation. This reproduced top scoring conforma-
tions of 10 falling within root-mean-square deviation (rmsd) val-
ues of 0.696–1.064 Å from bound X-ray conformation for ALK,
suggesting this method is valid enough to be used for docking
studies of other compounds. The outputs were exported to VMD
and Pymol for visual inspection of the binding modes and interac-
tions of the compounds with amino acid residues in the active sites
(Fig. 2).
51.4 lM, respectively. The level of anticancer potential was studied
by automated docking of ligands to the binding sites of ALK. The
results revealed that compound 4e showed minimum binding en-
ergy (ꢀ5.99 kcal/mol), which indicates its strong affinity towards
ALK protein. Further investigation concerning an enantioselective
version of this reaction and the mechanism of apoptosis induced
by these compounds in A549 cancer cell lines is currently ongoing
and will be reported in due course.
Acknowledgments
One of the authors, K.P. is grateful to the management of Orchid
Chemicals and Pharmaceuticals Ltd. The authors acknowledge the
Department of Chemistry, IITM, Chennai, India for single crystal
XRD analysis.
Docking of different ligands to protein was performed using
AUTODOCK, same protocols used in as that of validation study. All
docking were taken into 2.5 million energy evaluations were per-
formed for each of the test molecules. Docked ligand conforma-
tions were analyzed in terms of energy, hydrogen bonding, and
hydrophobic interaction between ligand and receptor protein
ALK. Detailed analyses of the ligand–receptor interactions were
carried out, and final coordinates of the ligand and receptor were
saved as pdb files. For display of the receptor with the ligand bind-
ing site, VMD software was used. From the docking scores, the free
energy of binding (FEB) of all compounds were calculated (Table 3).
The results of which revealed that compound 4e as the most active
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.bmcl.2013.02.086.
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15. Representative procedure for the synthesis of 4k: To a stirred solution of 5-
chloroisatin (181 mg, 1.0 mmoL), ethylcyanoacetate (113 mg, 1.0 mmoL) and
Cu(OTf)2 (18.1 mg, 5 mol %) in 1,2-dichloroethane was added kojic acid
(142 mg, 1.0 mmoL) at room temperature (25 °C). After refluxing for 25 min,
the reaction mixture was cooled to room temperature and treated with 25 mL
of water and extracted with dichloromethane (3 ꢁ 25 mL). The combined
organic layers were dried over anhydrous sodium sulfate and concentrated
under reduced pressure and purified by column chromatography over silica gel
(100–200 mesh) to afford pure product of 4k as off-white solid; IR (KBr): 3306,
1732, 1643, 1476, 1299, 1220, 1037, 869 cmꢀ1.1H NMR (400 MHz, DMSO-d6):
dH 0.77 (t, J = 7.0 Hz, 3H), 3.73–3.84 (m, 2H), 4.00 (tdd, J = 15.9 and 5.7 Hz, 2H),
5.62 (t, J = 5.7 Hz, 1H), 6.35 (s, 1H), 6.86 (d, J = 8.2 Hz, 1H), 7.26 (d, J = 8.2 Hz,
1H), 7.29 (s, 1H), 8.16 (br s, 2H,), 10.75 (br s, 1H).13C NMR (100 MHz, DMSO-d6)
dC 13.2, 51.4, 59.1, 59.2, 73.2, 110.8, 111.5, 123.9, 125.8, 128.7, 135.6, 136.6,
141.6, 147.1, 160.0, 166.9, 168.3, 169.5, 177.1. MS (ESI): m/z = 417 [35MCl+H]+,
419 [37MCl+H]+. Anal. Calcd for C19H15ClN2O7: C, 54.49; H, 3.61; N, 6.69. Found
C, 54.43; H, 3.60; N, 6.72.
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17. Crystallographic data of the structure of compound 4k have been deposited
with the Cambridge Crystallographic Data Centre as supplementary
publication no. CCDC-919587. Copies of the data can be obtained, free of
charge on application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax:
+44 01223 336033 or email: deposit@ccdc.cam.ac.uk).
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