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Inhibition of p53-Murine double minute 2 (MDM2) Interactions with 3,3’-Spirocyclopentene Oxindole Derivatives. Maxime Gicquel, Catherine Gomez, Maria Concepcion Garcia Alvarez, olivier pamlard, Vincent Guérineau, Eric Jacquet, Jérôme Bignon, Arnaud Voituriez, and Angela Marinetti J. Med. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jmedchem.8b01137 • Publication Date (Web): 17 Sep 2018 Downloaded from http://pubs.acs.org on September 17, 2018
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Journal of Medicinal Chemistry
Inhibition of p53-Murine double minute 2 (MDM2) Interactions with 3,3’-Spirocyclopentene Oxindole Derivatives. Maxime Gicquel, Catherine Gomez, Maria Concepcion Garcia Alvarez, Olivier Pamlard, Vincent Guérineau, Eric Jacquet, Jérôme Bignon,* Arnaud Voituriez,* Angela Marinetti* Institut de Chimie des Substances Naturelles, CNRS UPR 2301, Université Paris-Sud, Université Paris-Saclay, 1, av. de la Terrasse, 91198 Gif-sur-Yvette, France ABSTRACT: 3,3’-spirocyclopentene oxindoles structurally related to the Wang’s spiropyrrolidine oxindoles, have been highlighted as a new class of antiproliferative agents against cancer cell lines with wild-type p53 Status (IC50 up to 0.96 µM on SJSA-1 and 2.9 µM in HCT116 p53-wt). Inhibition of the MDM2-p53 interactions has been demonstrated through in vitro HTRF assays (IC50 up to 3.1 nM), while Western blot analysis showed activation of p53 selectively in HCT116 cancer cell lines with wild type p53.
INTRODUCTION The tumor suppressor protein p53 is known to be inhibited in many human cancers by the murine double minute 2 oncoprotein (MDM2). Accordingly, restoration of p53 activity has become an appealing therapeutic strategy for which several small molecules have been designed during the last fifteen years or so, notably in the nutlin family.1-5 The 2-oxospiro[indoline-3,3’-pyrrolidine] 1 ( Figure 1) typifies a well-known series of inhibitors of the MDM2-p53 interaction initially reported by Shaomeng Wang and co-workers and developed then by the same authors in collaboration with Sanofi.6-11 Compounds 1 bind to MDM2 with low nanomolar affinity, reactivates p53 in tumor cells and induce strong tumor growth inhibition. The Wang’s pioneering work on this class of compounds has founded an innovative strategy which ends up to early stage clinical trials for the treatment of human cancers retaining wild-type p53 with overexpressed MDM2, such as myeloid leukemia or solid tumors.12, 13 A known shortcoming of compounds 1 is that they isomerize via reversible ring-opening retro-Mannich reactions leading to equilibrium mixtures of less active stereoisomers ( Figure 1a).10, 14 Indeed, stereoisomers of 1 have been isolated and clear correlations have been established between the relative configurations of the stereogenic centers, the consequent geometry of the pyrrolidine unit and the binding affinity. The cis-cis stereoisomer (R,R,R,S) shown in Figure 1 proved to be the most active compound. To circumvent this stability issue, several strategies have been applied. Thus for instance, spirooxindoles with two identical substituents on the pyrrolidine C2 carbon have been designed that force the isomerization process toward a single, well-defined diastereomer. In this series, compound 2 (
Figure 1b) has entered clinical trials recently.15, 16 Alternatively, Gollner designed another series of spirooxindoles typified by 3 in Figure 1b, in which the C2 carbon of a pyrrolidine constitutes the quaternary center at the ring junction, instead of the C3 carbon. The 3,2’-spiropyrrolidinyl units ensure the configurational stability of these compounds since the retro-Mannich reaction cannot occur here. Compound 3 was tested in the SJSA-1 osteosarcoma xenograft model by oral administration. Findings confirmed on-target activity, i.e. MDM2 inhibition as the mode of action.17
Figure 1. (a) The Wang’s 2-oxospiro[indoline-3,3’pyrrolidine] 1 and its epimerization via retroMannich/Mannich reactions; (b) Compounds designed to prevent epimerization.
Herein we report on a new strategy to avoid the undesired epimerization process above, that is the use of spirooxindole derivatives, structurally related to 1, in which the
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pyrrolidine unit of the spiranic scaffold is replaced by a cyclopentene ring (Figure 2).
the reaction affords spirooxindoles III. With γsubstituted allenoates (R’≠H) the reaction takes place regioselectively via α-addition of the allenoate-phosphine zwitterionic adduct, and ends up to spirocyclopent-3-enes IV.25 With these efficient synthetic tools in hand, we have envisioned to access spirooxindole esters of the general formula IV (for R’=CH2tBu), as precursors for the target spirooxindole carboxamides 4.
Figure 2. Carbocyclic analogues of the MDM2-p53 inhibitors 1 (this work).
RESULTS AND DISCUSSION Structure-activity relationship studies have demonstrated that, in the spiro-pyrrolidine oxindoles 1, the NH group in the 3-position seems not to be crucial to their antitumor activity related to inhibition of the MDM2-p53 interaction. It has been shown, for instance, that analogues in which the NH function occupies the 2-position and a carbon atom takes the 3-position may be strong inhibitors as well.17 Also, analogues of 1 displaying bicyclic pyrrolidine units with substituted N-atoms, have demonstrated good activity.18 To the best of our knowledge however, analogues of 1 displaying an all-carbon ring as the spirocyclic component, instead of a pyrrolidinyl unit, haven’t been considered so far in the literature, although they will have the main advantage of being chemically and configurationally stable. In this context, the main aim of this study has been to establish if carbon-analogues of the spiro-pyrrolidine-oxindoles 1 might display analogous MDM2-p53 inhibition. For these initial studies we have targeted the spiro-3,3’cyclopenteneoxindoles 4 in Figure 2. For comparison purposes, the targeted carbocyclic analogues of 1 display the same substitution pattern on the oxindole (6chlorooxindole), as well as the same 3-chloro-2fluorophenyl substituent on the α-carbon. Compared to 1, compounds 4 lack the stereogenic centre in C4, which should rather simplify the synthetic approach and reduce the number of possible diastereomers. Synthesis For building the spirocyclic scaffold of 4, we will take advantage of the so-called Lu’s reaction, a phosphine promoted [3+2] cyclization between electron-poor allenes and electron-poor olefins leading to highly functionalized cyclopentenes.19, 20 We and others have demonstrated previously that this general method can be conveniently applied to the cyclization between 3-arylidene oxindoles I and allenoates II to afford spirooxindole derivatives III or IV, both in racemic and enantioenriched forms (Figure 3).21-24 Starting from non-substituted allenoates (R’=H),
Figure 3. Synthesis of spirocyclopenteneoxindoles via phosphine catalyzed [3+2] cyclizations.
In our preliminary study,25 the method has been illustrated notably by the synthesis of esters 7a from the Nacetyl 3-(3-chloro-2-fluorobenzylidene)oxindole (E)-5 and allenoate 6a (R = Et) in the presence of either PPh3 or PMe2Ph as the catalysts (Scheme 1, entries 1-2). Unfortunately, these [3+2] cyclization reactions produced the ciscis stereoisomer 7a’ as a minor product only (
