Exploration of [2 + 2 + 2] cyclotrimerisation methodology to prepare tetrahydroisoquinoline-based compounds with potential aldo-keto reductase 1C3 target affinity

Article abstract of DOI:10.1039/c9md00201d

Tetrahydroisoquinoline (THIQ) is a key structural component in many biologically active molecules including natural products and synthetic pharmaceuticals. Here, we report on the use of transition-metal mediated [2 + 2 + 2] cyclotrimerisation of alkynes to generate tricyclic THIQs with potential to selectively inhibit AKR1C3.

Full text of DOI:10.1039/c9md00201d

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DOI: 10.1039/C9MD00201D
ARTICLE
Exploration of [2+2+2] cyclotrimerisation methodology to prepare
tetrahydroisoquinoline-based compounds with potential aldo-
keto reductase 1C3 target affinity
Received 00th January 20xx,
Accepted 00th January 20xx
Ana R. N. Santos,a Helen M. Sheldrake,a Ali I.M. Ibrahim,a,b Chhanda Charan Danta,a Davide
Bonanni,c Martina Daga, Simonetta Oliaro-Bosso,c Donatella Boschi,c Marco L. Lollic and Klaus
Porsa,*
DOI: 10.1039/x0xx00000x
Tetrahydroisoquinoline (THIQ) is a key structural component in many biologically active molecules including natural
products and synthetic pharmaceuticals. Here, we report on the use of transition-metal mediated [2+2+2]
cyclotrimerisation of alkynes to generate tricyclic THIQs with potential to selectively inhibit AKR1C3.
be a plausible target.17 Interestingly, [2+2+2] cyclotrimerisation
methodology have been exploited to generate functionalised
phosphorus analogues of the THIQ pharmacophore18 and fused
1. Introduction
Prostate cancer is the most commonly diagnosed cancer and the
second leading cause of death in men.1 Patients that no longer
respond to radiation and androgen deprivation therapy (ADT)
develop castration-resistant prostate cancer (CRPC), which is a
lethal disease with no curative treatment options. In the steroid
biosynthesis pathway, the aldo-keto reductase family 1 member C3
(AKR1C3) is an enzyme that is known to catalyse transformation of
the hormone precursors androstenedione and androsterone to
highly active testosterone and dihydrotestosterone (DHT)
respectively, which is linked with prostate cancer cell proliferation.2
Much AKR1C3 inhibitor research has been focused on
indoloisoquinolines19 from diyne and terminal alkyne intermediates.
Indeed, [2+2+2] cyclotrimerisations have been shown to be useful
in the synthesis of a variety of molecular structures ranging from
intricate natural products to synthetically interesting small
molecules.20 Here we report on the synthesis of tricyclic THIQs using
a transition-metal mediated [2+2+2] cyclotrimerisation strategy to
generate novel compounds to target AKR1C3.
2. Results and discussion
medroxyprogesterone acetate (MPA), steroidal lactones, cinnamic 2.1 Chemical explorations
acids, flavonoids and nonsteroidal anti ‑ inflammatory drugs
Dialkyne 9 was prepared starting from 4 in three steps (Scheme 1A).
(NSAIDs)3 while new potent and selective 1,3,5-metasubstituted
retroinverted amides show promise for lead optimisation.4 Our
interest in novel drug design approaches5-7 has recently led to the
discovery of benzoisoxazole, hydroxytriazole and hydroxyfurazan
NSAIDs as potent and selective AKR1C3 inhibitors by application of
a bioisosteric scaffold hopping approach.8-11
Racemic alkyne
7
was obtained by the reaction of
allenyltributylstannane 6 with ethoxylactams 5.21 Dialkyne 9 was
obtained by treatment of 7 with NaH and propargyl bromide in 83
% yield.
The transition metal-mediated [2+2+2] cyclotrimerisation of
alkynes was investigated initially using dialkyne 9, Wilkinson's
catalyst (Rh(PPh3)3Cl, 5 mol %) and diethyl acetylenedicarboxylate
10a (‘a’ denotes specific alkyne used, see Table 2), in refluxing
toluene. The desired tricyclic product 14a was obtained in 30 %
yield along with the hexasubstituted benzene 11a resulting from
trimerisation of monoalkyne 10a (24 %), and pentasubstituted
benzenes 12a (21 %) and 13a (22 %), which resulted from the
intermolecular reaction of two molecules of monoalkyne 10a and
the individual alkyne branches of dialkyne 9 (Scheme 1B). The
optimisation of this reaction is further reported in Table S1.
Next, we decided to investigate the influence of the catalyst on
the product formation. Encouragingly, the yield of 14a could
be increased to 70 % with Cp*Ru(cod)Cl as the catalyst (entry
4, Table 1), indicating this was the most chemoselective of the
four catalysts used.
Tetrahydroisoquinoline (THIQ) is a key structural component of
many biologically active natural products and synthetic derivatives.
As a consequence, THIQ has been used as a strategic building block
for both synthetic explorations and for the generation of small
molecules of biological interest.12-16 Recently, Pictet-Spengler
chemistry and in silico studies were employed to generate a novel
series of THIQ-triazole based analogues, which showed AKR1C3 to
a. Institute of Cancer Therapeutics, Faculty of Life Sciences, University of Bradford,
West Yorkshire, BD7 1DP, UK..
b. Present address: Department of Pharmacy, Al-Zaytoonah University of Jordan,
Queen Alia Airport St 594, Amman, 11733, Jordan.
c. Department of Science and Drug Technology, University of Torino, Via Pietro
Giuria 9, 10125 Torino, Italy.
* Corresponding Author; Email: k.pors1@bradford.ac.uk
Electronic Supplementary Information (ESI) available: Synthetic protocols, [2+2+2]
cyclotrimerisation optimisation and binding mode of 14a in AKR1C2.
protocols.. See DOI: 10.1039/x0xx00000x
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docking score than berberine (Figure 1). Accordingly, only
A
View Article Online
compounds 14a, 14e and 15 were synthesised and selected for in
DOI: 10.1039/C9MD00201D
Bu3Sn
NaBH4
vitro screening using AKR1C2 and 1C3 purified enzymes. Starting
from compound 14a, the carboxylic acid 15 and the hydroxymethyl
analogue 14e were obtained by either acidic hydrolysis or reductive
conditions (see ESI).
6
O
N
O
O
OEt
EtOH/HCl
0 ºC, 4 h
41%
N
H
5
BF3.OEt2, DCM
-40 ºC, 7.5 h
70%
H
4
Table 2. Exploration of alkynes suitable for [2+2+2] cyclotri-
merisation chemistry.
1. NaH, DMF
0 ºC, 0.5 h
O
Yield (%)
N
O
N
H
7
2.
Mono
alkyne
Time
(h)
Br
Entry
R =
8
9
0.5 h, 0 ºC
83%
11ª
12
13
14
1
2
3
4
5
6
7
8
9
(10a)
(10b)
(10c)
(10d)
(10e)
(10e)
(10f)
(10g)
(10h)
EtO2C
MeO2C
CH3CH2
CH3(CH2)2
CH2OH
CH2OH
CH2Cl
2.5
1
12
22
trace
---
10
17
70
34
R
B
Rh(PPh3)3Cl (5 mol %)
Toluene, reflux
o/n
R
R
R
R
20
Degraded
Degraded
Degraded
Degraded
Degraded
20
+
9
+
R
R
4 days
3 daysb
24
10
R
R
R
11
R
C6H5
24
32
---
---
trace
R
TMS
24
Degraded
O
O
N
N
R
O
N
Reactions performed with 0.310 mmol of dialkyne 9, 5 eq. of
monoalkyne 10 in 2 mL of toluene under reflux with 10 mol % of
Cp*Ru(cod)Cl. ayield based on the amount of monoalkyne used,
breaction carried out in DMF at 110 ºC.
R
R
+
+
R
R
R
R
R
12
13
R
14
R
Compounds 14a, 14e and 15 were assayed at up 50 µM and
inhibitory effect was observed for all compounds against AKR1C3
(Table 3). Berberine was found to be the most potent compound,
but did not exhibit AKR isoform selectivity. In contrast, 14a was 8-
fold more potent in inhibiting AKR1C3 over 1C2. Given the lower
potency in inhibiting 14e and 15 these compounds were not
assayed against AKR1C2.
Scheme 1. Synthesis of key dialkyne 9 (A) and THIQ analysis of by-
products (B). See Table 2 for identity of R groups used.
Table 1. Exploration of catalysts to faciliate [2+2+2] cyclotri-
merisation of dialkynes.
Yield (%)
O
Entry
Catalyst
Time (h)
11ac
24
12a
21
13a
22
7
14a
30
44
18
70
R
N
1
2
3
4
Rh(PPh3)3Cla
18
4
N
N
N
R
b
CpCo(CO)2
11
3
O
O
O
16
poor affinity, binding
b, d
14a
14e
15
(R = COOCH2CH3) -11.76 kcal/mol
(R = CH2OH) -10.61 kcal/mol
(R = CO2H) -12.40 kcal/mol
[Ir(cod)Cl]2
Cp*Ru(cod)Clb
6.5
2.5
32
18
7
12
trace
10
energy not determined
Catalysts tested for the synthesis of tricyclic adduct 14a. Reactions
performed with 0.310 mmol of dialkyne 9, 5 eq. of diethyl
acetylenedicarboxylate 10a in refluxing toluene (2 mL). a5 mol %
O
O
N
b
c
catalyst, 10 mol % catalyst, yield based on the amount of diethyl
H3CO
N
N
acetylenedicarboxylate 10a used, dDIPHOS 10 mol %.
HO
O
17
18
-9.53 kcal/mol
Berberine (19)
-11.83 kcal/mol
H3CO
-9.86 kcal/mol
Fig. 1. 2,3-hybridised THIQs with calculated binding energies from
AKR1C3 molecular docking studies using GLIDE.
2.2 Biological evalution and computational analysis
The 2,3-functionalised THIQ 14a and a small panel of analogues
(14e, 15-18) with modified electronic properties, which could be
easily synthesised from 14a, were subjected to AKR1C3 molecular
docking studies using GLIDE Induced Fit protocol22 in order to
identify possible binding affinities. Calculated binding energies for
both the carboxyethyl (14a, -11.76 kcal/mol) and carboxylic (15,
12.40 kcal/mol) THIQs were shown to be comparable with
berberine (-11.56 kcal/mol), an isoquinoline alkaloid and known
AKR1C3 inhibitor.23 However, compound 14e showed a slightly
lower docking score (-10.61 kcal/mol) to berberine while
compounds 16-18 had at least two orders of magnitude smaller
Subsequently, we analyzed the predicted binding mode of 14a
(Figure 2). The compound was shown to extend into sub-pocket 3
(SP3) (Tyr24, Glu192, Ser217, Ser221, Gln222, Tyr305, Phe306),24
and link an H-bond into oxyanion site (OS) with Tyr55 and His117.
Furthermore, 14a shows a π-π stacking interaction with the Phe306
residue while still being able to protrude inside both SP1 (Ser118,
Asn167, Phe306, Phe311, Tyr319) and SP2 (Trp86, Ser129, Trp227,
Phe311) binding pockets with the ester groups and enabling H-bond
interaction with Ser118. Whilst berberine was not selective over
AKR1C2, 14a demonstrated encouraging selectivity that can
2 | J. Name., 2012, 00, 1-3
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possibly be correlated with the more restricted AKR1C2 binding introduced with relative ease, providing libraries of new small
View Article Online
pocket compared with AKR1C3.24
molecules with improved potency and selectivity for AKR1C3.
DOI: 10.1039/C9MD00201D
Table 3. Inhibitory effect on AKR1C3 and AKR1C2 recombinant
enzymes.
Experimental
AKR1C3 inhibitiona
IC50 (µM) ± SE
5.90 ± 0.19
AKR1C2 inhibition
IC50 (µM) ± SE
6.71 ± 2.17
Chemical synthesis
The detailed experimental procedures for all new compounds
can be found in the ESI.
Compound
Berberine
14a
11.69 ± 0.41
> 50
(25.04 % ± 3.95)b
96.20 ± 7.17
> 50
(26.90 % ± 1.56)b
Computational modelling
14e
The structures of compounds 14 - 18, as well as the structure of
berberine, were constructed using the 2D Sketcher tool
implemented in Maestro GUI. For each compound, an advanced
conformational search was performed using OPLS_2005 as Force
Field and setting 1000 maximum steps for each run. Molecular
docking was performed using Schrodinger Induced Fit Docking
protocol (IFD).22 For this purpose, the X-ray crystallographic
structure of AKR1C3 was retrieved from RCSB Database (PDB code:
1S2C)25 and the generated conformers were docked. Before
docking, the crystal structure of the protein underwent an
optimisation process using the Protein Preparation Wizard tool,
implemented in Maestro™ GUI. Missing hydrogen atoms were
added and bond orders were assigned. Then, DMS, non-structural
water molecules and impurities (such as solvent molecules) were
removed. Cofactor Acid NAP was maintained. Reorientation of
automatically optimised hydrogen bond network: hydroxyl and thiol
groups, amide groups of asparagine (Asn) and glutamine (Gln), and
the imidazole ring in histidine (His). Moreover, the prediction of
protonation states of His - aspartic acid (Asp), glutamic acid (Glu),
and tautomeric states of His – were accomplished using PROPKA™.
Standard IFD protocol was performed using the co-crystallised
ligand flufenamic acid to center the grid. Protein preparation
constrained refinement and Glide XP re-docking were settled, the
other parameters were kept by default.
23.11 ± 1.85
27.33 ± 4.34
15
a
b
Experiments performed with S-tetralol as substrate,
inhibition ± SE at 50 µM.
% of
Fig. 2. Compound 14a docking pose in the AKR1C3 binding site.
Dash lines represent H-bond, the bold arrow indicates sub-pocket 3.
Only the most significant amino acids are shown.
To better investigate this hypothesis,
a docking analysis of
Expression and purification of recombinant human AKR1C3 and
AKR1C2
compound 14a on AKR1C2 was conducted (Figure S3). Because of
the tighter binding pocket, compound 14a was found unable to
interact with SP1 and presented a completely different binding
mode in comparison with AKR1C3 illustrated above. The reduced
affinity for AKR1C2 is in agreement with a lower predicted binding
energy (-10.31 kcal/mol), indicating a non-optimal protein-ligand
interaction. Clearly, while further investigations are necessary to
fully understand the therapeutic potential of THIQs, the data
presented here suggest a useful starting point for design of more
potent and selective AKR1C3 inhibitors.
Escherichia coli BL21 (DE) Codon Plus RP cells expressing
recombinant AKR1C3 and AKR1C2 proteins were used. Protein
expression and purification were performed as previously
described.8 Briefly, bacteria cells were grown in YT2X media
supplemented with ampicillin at 37°C and at OD600 nm = 0.6 the
expression was induced by IPTG (0.5 mM) at 24°C for 2 h. Then,
bacteria were centrifuges and lysed with four freeze-thaw cycles in
presence of lysozyme and protease inhibitors. DNA was digested
with benzonase (25 U) in presence of MgCl2 5 mM. The lysate was
centrifuged for 30 min at 13,000 x g and the supernatant was
collected. AKR1C3 and AKR1C2 were affinity purified via N-terminal
GST-tag on glutathione (GT) sepharose (GE-Healthcare) and cleaved
of by thrombin according to the manufacturer’s protocol.
Expression and purification was monitored by SDS-PAGE.
Conclusions
In summary, dialkyne, 9 was prepared using amide reduction and
aminal substitution to introduce one propargyl sidechain, followed
by amide N-alkylation with propargyl bromide to introduce the
In vitro AKR1C3 and AKR1C2 inhibition assays
second
chain.
A
transition-metal
catalysed
[2+2+2]
The inhibition assays were performed on purified recombinant
enzymes as previously described.8 Briefly, the enzymatic reaction
was fluorimetrically (ex/em; 340 nm/ 460 nm) monitored by the
measurement of NADPH production on an “Ensight” plate reader
(Perkin Elmer) at 37°C. Assay mixture contained S-tetralol (in EtOH),
inhibitor (in EtOH), 100 mM phosphate buffer, pH 7, 200 µM NADP+,
and purified recombinant enzyme (30 µl) in a final volume of 200 µl
and 10 % EtOH was added in 96-well plate. The S-tetralol
concentration used in the AKR1C2 and AKR1C3 inhibition assays
cyclotrimerisation of a pyrrolidinone dialkyne was then used as a
new approach to synthesise 2,3-functionalised THIQ derivatives.
The best yield resulted from the reaction of dialkynes 9 with
diethylacetylene dicarboxylate 10a and Cp*Ru(cod)Cl in refluxing
toluene. This approach allows the aromatic part of the molecule to
be assembled at a late stage of the synthesis. An advantage of
diversifying the THIQ pharmacophore at this late point is that the
substituents around the aromatic ring of the THIQ can be
This journal is © The Royal Society of Chemistry 20xx
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were 15 µM and 160 µM, respectively; the same as the Km
described for the respective isoforms under the same experimental
conditions. Percent inhibition with respect to the controls 12.
containing the same amount of solvent, without inhibitor, was
calculated from the initial velocities, obtained by linear regression 13.
of the progress curve, at different concentrations of the inhibitor.
The IC50 values were obtained using PRISM 7.0, GraphPad Software. 14.
The values obtained were the means of two separate experiments
Grossert, R. L. White, D. Boschi and M. L. Lolli, J.
View Article Online
Heterocycl. Chem., 2019, 56, 501-D51O9I:.10.1039/C9MD00201D
J. D. Scott and R. M. Williams, Chem. Rev., 2002, 102,
1669-1730.
A. W. Kahsai, S. Zhu, D. J. Wardrop, W. S. Lane and G.
Fenteany, Chem. Biol., 2006, 13, 973-983.
N. T. Patil, H. Wu and Y. Yamamoto, J. Org. Chem., 2007,
72, 6577-6579.
A. B. J. Bracca and T. S. Kaufman, Tetrahedron, 2004, 60,
10575–10610.
each carried out in triplicate.
15.
16.
Y. D. Zhou, Y. P. Kim, K. A. Mohammed, D. K. Jones, I.
Muhammad, D. C. Dunbar and D. G. Nagle, J. Nat. Prod.,
2005, 68, 947-950.
Conflicts of interest
There are no conflicts to declare.
17.
18.
R. Pingaew, P. Mandi, C. Nantasenamat, S.
Prachayasittikul, S. Ruchirawat and V. Prachayasittikul,
Eur. J. Med. Chem., 2014, 81, 192-203.
M. A. Zotova, D. V. Vorobyeva, P. H. Dixneuf, C. Bruneau
and S. N. Osipov, Synlett, 2013, 24, 1517-1522.
A. Swami and C. V. Ramana, Synlett, 2015, 26, 604-608.
S. Kotha, E. Brahmachary and K. Lahiri, Eur. J. Org. Chem.,
2005, 4741-4767.
W. F. J. Karstens, F. P. J. T. Rutjes and H. Hiemstra,
Tetrahedron Lett., 1997, 38, 6275-6278.
Schrödinger Suite 2017-4, Glide, Schrödinger, 2017;
Prime, Schrödinger, LLC, New York, NY.
Y. T. Tian, L. J. Zhao, Y. Wang, H. T. Zhang, D. Xu, X. J.
Zhao, Y. Li and J. Li, Asian J. Androl., 2016, 18, 607-612.
M. C. Byrns, Y. Jin and T. M. Penning, J. Steroid. Biochem.
Mol. Biol., 2011, 125, 95-104.
A. L. Lovering, J. P. Ride, C. M. Bunce, J. C. Desmond, S. M.
Cummings and S. A. White, Cancer Res., 2004, 64, 1802-
1810.
Acknowledgements
This work was supported by Fundação para a Ciência, a
Tecnologia (PhD studentship ARNS SFRH/BD/46871/2008),
EPSRC (RCUK Academic Fellowship HMS), UniTO grant Ricerca
Locale 2015 (grant number LOLM_RILO_17_01) and
Fondazione Cassa di Risparmio di Torino (grant
BOSD_CRT_17_2). We would like to thank Ms Teresa Folino for
assistance with synthesis, Mr Andrew Healey for LRMS and the
EPSRC NMSSC for HRMS measurements.
19.
20.
21.
22.
23.
24.
25.
References
1.
2.
3.
4.
5.
6.
R. L. Siegel, K. D. Miller and A. Jemal, CA Cancer J. Clin.,
2016, 66, 7-30.
A. O. Adeniji, M. Chen and T. M. Penning, J. Steroid.
Biochem. Mol. Biol., 2013, 137, 136-149.
A. C. Pippione, D. Boschi, K. Pors, S. Oliaro-Bosso and M. L.
Lolli, J Cancer Metastasis Treat., 2017, 3, 328-361.
K. Verma, T. Z. Zang, T. M. Penning and P. C. Trippier, J.
Med. Chem., 2019, 62, 3590-3616.
M. Lolli, S. Narramore, C. W. G. Fishwick and K. Pors, Drug
Discov. Today, 2015, 20, 1018-1026.
K. Pors, InTech, Drug Discovery and Development - Present
and Future, Edited by Dr Izet Kapetanović, 2011, Chapter
4, 69-96.
7.
8.
K. Pors, F. W. Goldberg, C. P. Leamon, A. C. Rigby, S. A.
Snyder and R. A. Falconer, Drug Discov. Today, 2009, 14,
1045-1050.
A. C. Pippione, A. Giraudo, D. Bonanni, I. M. Carnovale, E.
Marini, C. Cena, A. Costale, D. Zonari, K. Pors, M. Sadiq, D.
Boschi, S. Oliaro-Bosso and M. L. Lolli, Eur. J. Med. Chem.,
2017, 139, 936-946.
9.
M. L. Lolli, I. M. Carnovale, A. C. Pippione, W. Y. Wahlgren,
D. Bonanni, E. Marini, D. Zonari, M. Gallicchio, V. Boscaro,
P. Goyal, R. Friemann, B. Rolando, R. Bagnati, S. Adinolfi,
S. Oliaro-Bosso and D. Boschi, ACS Med. Chem. Lett. 2019,
10, 437-443.
10.
11.
A. C. Pippione, I. M. Carnovale, D. Bonanni, M. Sini, P.
Goyal, E. Marini, K. Pors, S. Adinolfi, D. Zonari, C.
Festuccia, W. Y. Wahlgren, R. Friemann, R. Bagnati, D.
Boschi, S. Oliaro-Bosso and M. L. Lolli, Eur. J. Med. Chem.,
2018, 150, 930-945.
S. Sainas, A. C. Pippione, A. Giraudo, K. Martina, F. Bosca,
B. Rolando, A. Barge, A. Ducime, A. Federico, S. J.
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