ABSTRACT
We explored a new isonitrile, namely 4-(N-phthalimido)phenyl isonitrile, with extraordinary features. The novel isocyanide has a pharmacophore, the phthalimido (Pht) group, that possesses promising pharmaceutical activities. We found that the novel isonitrile is unexpectedly odorless as an extra bonus which makes its handling easy in organic synthesis to serve as a scaffold for building several new amide derivatives through multicomponent reactions, overcoming the stink of common aromatic isonitriles such as phenyl isonitrile, benzyl isonitrile, p-nitrophenyl isonitrile, and ethyl 4-isocyano benzoate. The novel isonitrile 9 serves as a source of N-protected isonitrile with a Pht group, where the Pht group can be easily removed via hydrazinolysis, affording the corresponding primary amine/alcohol scaffold which could be used as a precursor to synthesize Passerini products via acylation directly to afford Passerini adducts 14 and 15 without carrying out the traditional Passerini three-component reaction; this new isonitrile is considered as a novel convertible isocyanide analogue.
ABSTRACT
The development of novel therapeutics promoting selective tumor elimination is the mainstay of clinical oncology. Emerging insights into tumor targeting reveal caspases activation, especially caspase-3, as a personalized anticancer strategy. Our on-going cancer research has exploited Passerini α-acyloxy carboxamides as caspase-3/7-dependent apoptotic inducers. Herein, we adopted scaffold hopping design to introduce new series of isoindole-based Passerini adducts as caspase-3/7 activators inspired by natural alkaloids from Lion's Mane mushroom promoting caspase-3-mediated apoptosis. Additional pharmacophoric motifs of lead caspase activators were merged into the tailored Passerini skeleton. The rationally designed adducts were synthesized utilizing one-pot reaction of the novel 4-(2'-phthalimido)phenylisonitrile 5, cyclohexanone and miscellaneous carboxylic acids under Passerini conditions. All derivatives were screened for their antiproliferative activities against lung A549, colorectal Caco-2 and breast MDA-MB 231 cancer cells compared to normal fibroblasts utilizing MTT assay. Most of the evaluated derivatives were superior to 5-fluorouracil. The 2-(1H-indol-3-yl)acetate derivative (8a) recorded the highest anticancer potency (IC50 = 0.04-0.11 µM) and selectivity (SI = 42.59-125.53), followed by the 3-(4-(trifluoromethyl)phenyl)acrylate (8m), the 2-(phenylsulfonyl)glycinate (8q), and the 2-(2-(3-phenyl-1,2,4-oxadiazol-5-yl)phenoxy)acetate (8c) derivatives, respectively. The four hits induced cancer cells apoptosis (up to 57.99%) via caspase-3/7 activation (up to 5.47 folds). Apoptosis-inducing factor1 (AIF1) quantification assay excluded their caspase-independent apoptosis induction potential via AIF1 signaling pathway. Docking simulations clarified the possible binding modes of the hit compounds with XIAP BIR2 domain; the specific receptor of caspase-3/7 activators, and aided identifying their structural determinants of activity. Finally, their practical LogP, efficiency metrics, in silico ADMET profiling were drug-like.
