An Enolate-Structure-Enabled Anionic Cascade Cyclization Reaction: Easy Access to Complex Scaffolds with Contiguous Six-, Five-, and Four-Membered Rings.

Catalyst-free addition of ketone enolate to non-activated multiple C-C bonds involves non-complementary reaction partners and typically requires super-basic conditions. On the other hand, highly aggregated or solvated enolates are not reactive enough to undergo direct addition to alkenes or alkynes. Herein, we report a new anionic cascade reaction for one-step assembly of intriguing molecular scaffolds possessing contiguous six-, five-, and four-membered rings, representing a formal [2+2] enol-allene cycloaddition. Reaction proceeds under very mild conditions and with excellent diastereoselectivity. Deeper mechanistic and computational studies revealed unusually slow proton transfer phenomenon in cyclic ketone intermediate and explained peculiar stereochemical outcome.

CKT0353, a novel microtubule targeting agent, overcomes paclitaxel induced resistance in cancer cells.

Microtubule targeting agents (MTAs) are extensively used in cancer treatment and many have achieved substantial clinical success. In recent years, targeting microtubules to inhibit cell division has become a widespread pharmaceutical approach for treatment of various cancer types. Nevertheless, the development of multidrug resistance (MDR) in cancer remains a major obstacle for successful application of these agents. Herein, we provided the evidence that CKT0353, α-branched α,ß-unsaturated ketone, possesses the capacity to successfully evade the MDR phenotype as an MTA. CKT0353 induced G2/M phase arrest, delayed cell division via spindle assembly checkpoint activation, disrupted the mitotic spindle formation and depolymerized microtubules in human breast, cervix, and colorectal carcinoma cells. Molecular docking analysis revealed that CKT0353 binds at the nocodazole binding domain of ß-tubulin. Furthermore, CKT0353 triggered apoptosis via caspase-dependent mechanism. In addition, P-glycoprotein overexpressing colorectal carcinoma cells showed higher sensitivity to this agent when compared to their sensitive counterpart, demonstrating the ability of CKT0353 to overcome this classic MDR mechanism involved in resistance to various MTAs. Taken together, these findings suggest that CKT0353 is an excellent candidate for further optimization as a therapeutic agent against tumors with MDR phenotype.

Synthesis and antiproliferative activity of α-branched α,ß-unsaturated ketones in human hematological and solid cancer cell lines.

A series of α-branched α,ß-unsaturated ketones were prepared via boron trifluoride etherate mediated reaction between arylalkynes and carboxaldehydes. The evaluation of the antiproliferative activity over hematological (NB4) and solid cancer (A549, MCF-7) cell lines provided a structure-activity relationship. 5-Parameter QSAR equations were built which were able to explain 80%-92% of the variance in activity. The resulting selective lead compound showed IC50 value 0.6 µM against the hematological cell line and did not cause apoptosis, but blocked cell cycle in G0/G1. Moreover, it was demonstrated that this compound enhances and accelerates retinoic acid induced granulocytic differentiation.

Divergent pathways and competitive mechanisms of metathesis reactions between 3-arylprop-2-ynyl esters and aldehydes: an experimental and theoretical study.

Mechanistic studies of the reaction between 3-arylprop-2-ynyl esters and aldehydes catalyzed by BF3 ⋅Et2 O were performed by isotopic labeling experiments and quantum chemical calculations. The reactions are shown to proceed by either a classical alkyne-carbonyl metathesis route or an unprecedented addition-rearrangement cascade. Depending on the structure of the starting materials and the reaction conditions, the products of these reactions can be Morita-Baylis-Hillman (MBH) adducts that are unavailable by traditional MBH reactions or E- and Z-α,ß-unsaturated ketones. (18) O-Labeling studies suggested the existence of two different reaction pathways to the products. These pathways were further examined by quantum chemical calculations that employed the DFT(wB97XD)/6-311+G(2d,p) method, together with the conductor-like screening model for realistic solvation (COSMO-RS). By using the wB97XD functional, the accuracy of the computed data is estimated to be 1-2 kcal mol(-1) , shown by the careful benchmarking of various DFT functionals against coupled cluster calculations at the CCSD(T)/aug-cc-pVTZ level of theory. Indeed, most of the experimental data were reproduced and explained by theory and it was convincingly shown that the branching point between the two distinct mechanisms is the formation of the first intermediate on the reaction pathway: either the four-membered oxete or the six-membered zwitterion. The deep mechanistic understanding of these reactions opens new synthetic avenues to chemically and biologically important α,ß-unsaturated ketones.

Synthesis and antiproliferative activity of α-branched α,ß-unsaturated ketones.

A series of α-branched α,ß-unsaturated ketones were prepared in a straightforward manner by the acid catalyzed coupling between arylalkynes and carbaldehydes. The method also allows producing as side product chalcone analogs bearing an additional α,ß-unsaturated arylketone in the molecular scaffold. The evaluation of the antiproliferative activity in the human solid tumor cell lines HBL-100 (breast), HeLa (cervix), SW1573 (non-small cell lung), T-47D (breast) and WiDr (colon) provided a structure-activity relationship. Overall, the compounds presented active against the resistant cancer cells T-47D. The resulting lead, displaying an unprecedented chalcone scaffold, showed GI50 values in the range 0.32-0.53 µM against all cell lines tested. The methoxy group present in the lead might play an important role in the activity.

A unique cascade reaction between 3-arylprop-2-inylcarboxylates and benzaldehydes leading to the formation of Morita-Baylis-Hillman adducts.

During an alkyne-carbonyl metathesis reaction between electron-rich 3-arylprop-2-inylcarboxylates and electron-poor benzaldehydes, a smooth migration of carboxylate groups takes place. This unique cascade reaction allows the formation of Morita-Baylis-Hillman (MBH) adducts unavailable via a traditional MBH reaction.