Enantioselective Total Synthesis of (+)-Conicol via Cascade Three-Component Organocatalysis

Synthesis of fused-pyran derivatives via a base-mediated annulation of bis-allenoates followed by auto-oxidation in air

We introduce, for the first time, an inorganic base-mediated cyclization and auto-oxidation of bisallenones/bisalkynones. This reaction is realized under mild conditions through precise control of the base and atmosphere, providing a wide range of structurally diverse fused-pyran derivatives with moderate to excellent yields. Utilizing KOH as the initiator under a nitrogen atmosphere, a series of novel cyclohexane-fused pyran derivatives was obtained as the primary product. In contrast, under aerobic conditions with Na2S as the catalyst, oxidative cyclization predominantly occurred, yielding cyclohexanone-fused pyran derivatives. The protocol also exhibits significant regioselectivity, particularly when asymmetric bisallenones/bisalkynones are selected as substrates.

Cancer-Stem-Cell Phenotype-Guided Discovery of a Microbiota-Inspired Synthetic Compound Targeting NPM1 for Leukemia

The human microbiota plays an important role in human health and disease, through the secretion of metabolites that regulate key biological functions. We propose that microbiota metabolites represent an unexplored chemical space of small drug-like molecules in the search of new hits for drug discovery. Here, we describe the generation of a set of complex chemotypes inspired on selected microbiota metabolites, which have been synthesized using asymmetric organocatalytic reactions. Following a primary screening in CSC models, we identified the novel compound UCM-13369 (4b) whose cytotoxicity was mediated by NPM1. This protein is one of the most frequent mutations of AML, and NPM1-mutated AML is recognized by the WHO as a distinct hematopoietic malignancy. UCM-13369 inhibits NPM1 expression, downregulates the pathway associated with mutant NPM1 C+, and specifically recognizes the C-end DNA-binding domain of NPM1 C+, avoiding the nucleus-cytoplasm translocation involved in the AML tumorological process. The new NPM1 inhibitor triggers apoptosis in AML cell lines and primary cells from AML patients and reduces tumor infiltration in a mouse model of AML with NPM1 C+ mutation. The disclosed phenotype-guided discovery of UCM-13369, a novel small molecule inspired on microbiota metabolites, confirms that CSC death induced by NPM1 inhibition represents a promising therapeutic opportunity for NPM1-mutated AML, a high-mortality disease.

Asymmetric synthesis of (R)-baclofen and (3S,4S)-tetflupyrolimet via "on water" organocatalytic addition reactions: a tip on catalyst screening

This work demonstrates asymmetric synthesis of the GABA derivative (R)-baclofen and a new herbicidal mode-of-action inhibitor (3S,4S)-tetflupyrolimet featuring low loading (0.5 mol%) organocatalytic addition reactions of dithiomalonates to nitrostyrenes under "on water" conditions. Importantly, we observed that increasing the hydrophobicity of the catalyst does not guarantee improved catalytic performance under "on water" conditions and the trends in the catalytic efficiency of different HBD catalysts under "on water" conditions (with hydrophobic additives) align more closely with those observed in pure hydrophobic organic solvents. These findings propose a valuable tip for screening organocatalysts in developing asymmetric hydrogen-bonding catalysis under "on water" conditions.

Enantioselective Total Synthesis of (-)-Cephalotanin B

Cephalotaxus diterpenoids are attractive natural products with intriguing molecular frameworks and promising biological features. As a structurally unusual member, (-)-cephalotanin B possesses an extraordinarily congested heptacyclic skeleton, three lactone units, and nine consecutive stereocenters. Herein, we report an enantioselective total synthesis of (-)-cephalotanin B based on a divergent asymmetric Michael addition reaction, a novel Pauson-Khand/deacyloxylation process discovered in the development of a second-generation stereoselective Pauson-Khand reaction protocol, and an epoxide-opening/elimination/dual-lactonization cascade to construct the challenging propeller-shaped A-B-C ring system as key transformations.

The chemistry of 2-hydroxy-β-nitrostyrenes: versatile intermediates in synthetic organic chemistry

The applications of 2-hydroxy-β-nitrostyrenes as efficient bifunctional intermediates in organic synthesis are investigated in this review. For this purpose, reactions of 2-hydroxy-β-nitrostyrenes with diverse molecules, including carbonyl compounds, 1,3-dicarbonyl compounds, α,β-unsaturated carbonyl compounds, hemiacetals, nitroalkenes, γ-butenolides, tetronic acid, azalactones, pyrazolones, enamines, malononitrile, methyleneindolinones, ylides, etc., were investigated to construct interesting biologically active scaffolds such as chromans, chromenes, coumarins, benzofurans and their fused and spiro rings, natural products, and other useful cyclic and acyclic compounds. The main focus is on the asymmetric synthesis of these compounds via cascade/domino/tandem reactions catalyzed by chiral organocatalysts. In this review, around 60 papers reported between the years 2000 and 2022 are presented.

Enantioselective Michael/Hemiketalization Cascade Reactions between Hydroxymaleimides and 2-Hydroxynitrostyrenes for the Construction of Chiral Chroman-Fused Pyrrolidinediones

In this paper, the organocatalytic asymmetric Michael addition/hemiketalization cascade reactions between hydroxymaleimides and 2-hydroxynitrostyrenes were developed, which provided a new protocol for building a chiral ring-fused chroman skeleton. This squaramide-catalyzed cascade reaction provided chiral chroman-fused pyrrolidinediones with three contiguous stereocenters in good to high yields (up to 88%), with excellent diastereoselectivities (up to >20:1 dr) and enantioselectivities (up to 96% ee) at −16 °C. Moreover, a scale-up synthesis was also carried out, and a possible reaction mechanism was proposed.

Highly diastereoselective annulation of 2-substituted 3-nitro-2H-chromenes with hemicurcuminoids and curcuminoids via a double and triple Michael reaction cascade

The K2CO3-catalysed double Michael addition of (E)-1,5-diaryl- and 1-alkyl-5-arylpent-4-ene-1,3-diones to 2-trifluoromethyl- and 2-phenyl-substituted 3-nitro-2H-chromenes in dichloromethane at room temperature for 48 h results in 10-aroyl(acyl)-7-aryl-6a-nitro-6,6a,7,8,10,10a-hexahydro-9H-benzo[c]chromen-9-ones in 75-98% yields as individual...

Recent Advance of Domino Michael Reaction in Natural Product Synthesis

Recent advances in the total syntheses of cyclic natural products and related compounds from 2005 to 2021, which employ domino Michael reactions as key steps, have been reviewed, focusing mainly on the domino Michael reactions catalyzed by organocatalysts.

Organocatalytic total synthesis of bioactive compounds based on one-pot methodologies

The combination of one-pot methodologies to asymmetric organocatalysis allow a green and direct access to many types of complex highly functionalized chiral products, including important key intermediates in total syntheses of important bioactive compounds. A series of chiral organocatalysts have already been successfully applied to such syntheses. This report collects major developments in the total synthesis of biologically active products based on the use of enantioselective organocatalytic domino/tandem reactions as key steps. It is divided into two parts dealing successively with reactions based on the use of proline-derived catalysts and other organocatalysts.

Oxa-Michael polyaddition of vinylsulfonylethanol for aliphatic polyethersulfones

The reactive AB-type monomer vinylsulfonylethanol polymerizes in the presence of common organic and inorganic bases forming a novel aliphatic polyethersulfone. A detailed analysis revealed different mechanisms for the organic and inorganic catalysts.

One-pot asymmetric synthesis of a hexahydrophenanthridine scaffold containing five stereocenters via an organocatalytic quadruple-cascade reaction

An organocatalytic enantioselective aza-Michael-Michael-Michael/aldol cyclization quadruple-cascade reaction of 2-amino-β-nitrostyrenes and α,β-unsaturated aldehydes has been developed for the construction of fully substituted hexahydrophenanthridine.

Advances in the Asymmetric Total Synthesis of Natural Products Using Chiral Secondary Amine Catalyzed Reactions of α,β-Unsaturated Aldehydes

Chirality is one of the most important attributes for its presence in a vast majority of bioactive natural products and pharmaceuticals. Asymmetric organocatalysis methods have emerged as a powerful methodology for the construction of highly enantioenriched structural skeletons of the target molecules. Due to their extensive application of organocatalysis in the total synthesis of bioactive molecules and some of them have been used in the industrial synthesis of drugs have attracted increasing interests from chemists. Among the chiral organocatalysts, chiral secondary amines (MacMillan's catalyst and Jorgensen's catalyst) have been especially considered attractive strategies because of their impressive efficiency. Herein, we outline advances in the asymmetric total synthesis of natural products and relevant drugs by using the strategy of chiral secondary amine catalyzed reactions of α,β-unsaturated aldehydes in the last eighteen years.

Organocatalysis: Trends of Drug Synthesis in Medicinal Chemistry

Background:

The continuous increase in challenges associated with the effective treatment of life threatening diseases influences the development of drug therapies with suitable physicochemical properties, efficiency and selectivity. So, organocatalysis is a potential synthetic tool which is accelerating the development of new drug molecules.

Methods:

Organocatalysis reactions can be carried out at lower temperatures and in milder pH conditions as compared to metal based catalysed reactions. Due to ready availability of catalysts, stability, purity, low toxicity and easy in handling of the chemical reactions, it has become an attractive technique to synthesise complex molecules with diverse structures. Here, the impact of various catalysts in organic synthesis with methods is discussed.

Results:

Organic catalysts are used widely in various chemical reactions such as Michael Addition, aldol reaction, Diels-Alder reactions and Knoevenagal reactions. It was observed that the use of organocatalyst results in the formation of stereo active molecules with diverse biological activities.

Conclusion:

This review also focuses on the various scopes and limitations of organocatalytic reactions in the production of medicinally useful drug molecules. Organocatalysts possess several advantages over traditional metal catalysts because they are non-toxic, readily available, stable, efficient, and easy to handle which involves environmentally friendly reaction.

Diastereodivergent Synthesis of Hexahydro-6H-benzo[c]chromen-6-one Derivatives Catalyzed by Modularly Designed Organocatalysts

The diastereodivergent synthesis of hexahydro-6H-benzo[c]chromen-6-one derivatives with good to high diastereoselectivities (up to 98:2 d.r.) and enantioselectivities (up to >99 % ee) has been achieved by using a domino Michael/Michael/hemiacetalization reaction between trans-2-hydroxy-β-nitrostyrenes and trans-7-oxo-5-heptenals followed by oxidation. With use of appropriate modularly designed organocatalysts (MDOs) that are self-assembled in situ from amino acid derivatives and cinchona alkaloid derivatives, two different diastereomers of the desired hexahydro-6H-benzo[c]chromen-6-ones are obtained from the same substrates.

Stereoselective synthesis of chromane derivatives via a domino reaction catalyzed by modularly designed organocatalysts

A highly enantio- and diastereoselective method for the synthesis of functionalized chroman-2-ones and chromanes was achieved by using an organocatalytic domino Michael/hemiacetalization reaction of aliphatic aldehydes and (E)-2-(2-nitrovinyl)phenols followed by a PCC oxidation and dehydroxylation, respectively. Using the modularly designed organocatalysts (MDOs) self-assembled from cinchona alkaloid derivatives and amino acids in the reaction media, the title products were obtained in good to high yields (up to 97%) and excellent diastereoselectivities (up to 99 : 1 dr) and enantioselectivities (up to 99% ee).

Tetrahydrobenzochromene Synthesis Enabled by a Deconjugative Alkylation/Tsuji-Saegusa-Ito Oxidation on Knoevenagel Adducts

A modular and practical route to versatile cyano-1,3-dienes by a sequence involving deconjugative alkylation and "Tsuji-Saegusa-Ito oxidation" is reported. In this letter, the versatility of the products is also explored, including a route to benzochromene scaffolds common to many natural products.

Catalytic enantioselective synthesis of carboxy-substituted 2-isoxazolines by cascade oxa-Michael-cyclization

An efficient quinidine-based phase-transfer-catalyzed enantioselective cascade oxa-Michael-cyclization reaction of hydroxylamine with various β-carboxy-substituted α,β-unsaturated ketones has been achieved for the preparation of chiral carboxy-substituted 2-isoxazolines. This cascade reaction provided the desired products in good yields (up to 98%) with excellent enantioselectivities (91-96% ee). In addition, the cascade reaction was effectively applied to the first catalytic asymmetric synthesis of the herbicide (S)-methiozolin.

Asymmetric synthesis of polysubstituted chiral chromans via an organocatalytic oxa-Michael-nitro-Michael domino reaction

A catalytic asymmetric method for the synthesis of polysubstituted chromans via an oxa-Michael-nitro-Michael reaction has been developed. The squaramide-catalyzed domino reaction of 2-hydroxynitrostyrenes with trans-β-nitroolefins produced chiral chromans with excellent enantioselectivities (up to 99% ee), diastereoselectivities (up to >20 : 1 dr), and moderate to good yields (up to 82%).

A distal vinyl shift (DVS) through quadruple domino reaction: synthesis of N-vinyl benzoheterocyclic scaffolds

An unprecedented Distal Vinyl Shift (DVS) through quadruple domino reaction has been disclosed via the synthesis of N-vinyl benzoheterocyclic scaffolds.

Organocatalytic asymmetric Michael/hemiacetalization/acyl transfer reaction of α-nitroketones with o-hydroxycinnamaldehydes: synthesis of 2,4-disubstituted chromans

An organocatalytic asymmetric synthesis of 2,4-disubstituted chroman compounds has been developed via a Michael/hemiketalization/acyl transfer reaction between o-hydroxycinnamaldehydes and α-nitroketones.

Divergent Strategy for the Diastereoselective Synthesis of the Tricyclic 6,7-Diaryltetrahydro-6H-benzo[c]chromene Core via Pt(IV)-Catalyzed Cycloaddition of o-Quinone Methides and Olefin Ring-Closing Metathesis

A divergent strategy for the synthesis of the tricyclic 6,7-diaryltetrahydro-6H-benzo[c]chromene core was successfully developed. The 2,3-trans, 2,4-cis trisubstituted chroman moiety was formed via highly efficient and stereoselective Pt(IV)-catalyzed cycloaddition reactions of the corresponding quinone methides with chalcones. Subsequent steps provided the common diene alcohol, which underwent BF₃·Et₂O-mediated Et₃SiH reduction and olefin ring-closing metathesis (RCM) using Ru(II) catalysts. The sequence of the final two steps provided a handle to diversify the stereochemical outcomes at C6 as well as C10a.

Heterogeneous enantioselective synthesis of chromans via the oxa-Michael–Michael cascade reaction synergically catalyzed by grafted chiral bases and inherent hydroxyls on mesoporous silica surface

A heterogeneous enantioselective oxa-Michael–Michael reaction for the synthesis of chromans has been developed on bifunctional catalysts, resulting in excellent catalytic performance.

Chiral phosphoric acid catalyzed enantioselective annulation of acyclic enecarbamates to in situ-generated ortho-quinone methides

The first organocatalytic asymmetric [4 + 2]-cycloaddition reaction between acyclic enecarbamates with in situ generated ortho-quinone methides has been developed using chiral phosphoric acids as catalysts.

Efficient construction of biologically important functionalized polycyclic spiro-fused carbocyclicoxindoles via an asymmetric organocatalytic quadruple-cascade reaction

A cascade organocatalysis has been developed for the asymmetric synthesis of a highly functionalized polycyclic spiro-fused carbocyclicoxindoles containing five contiguous stereogenic centers with good diastereoselectivity and high enantioselectivity.

A quadruple cascade protocol for the one-pot synthesis of fully-substituted hexahydroisoindolinones from simple substrates

A new and efficient synthetic method to obtain fully-substituted hexahydroisoindolinones was developed by using bifunctional tertiary amine-thioureas as powerful catalysts. As far as we know, there is no efficient synthetic method developed toward fully-substituted hexahydroisoindolinones. The products were obtained in good yield and diastereoselectivity. The one-pot cascade quadruple protocol features readily available starting materials, simple manipulation, mild conditions and good atom economy.

Rawal's catalyst as an effective stimulant for the highly asymmetric Michael addition of β-keto esters to functionally rich nitro-olefins

A general approach to the asymmetric synthesis of highly substituted dihydroquinolines was achieved through neighboring ortho-amino group engaged sequential Michael/amination/dehydration reactions.