Access to 12-Membered Cyclic ortho,meta-Diarylheptanoids: Total Synthesis of Actinidione via Isomyricanone

We describe herein the first access to 12-membered cyclic[7,0]ortho,meta-diarylheptanoids. The key features of the synthesis include both a Suzuki-Miyaura coupling and a ring closing metathesis. Actinidione, a promising natural product, along with a bioactive tetracyclic derivative were obtained in 14 steps for the first time from cheap commercially available substrates with an overall yield of 18-21%. Our modus operandi complies with the principles of the synthesis ideality by using notably strategic reactions.

Towards Atropoenantiopure N-C Axially Chiral Compounds via Stereoselective C-N Bond Formation

N-C axial chirality, although disregarded for decades, is an interesting type of chirality with appealing applications in medicinal chemistry and agrochemistry. However, atroposelective synthesis of optically pure compounds is extremely challenging and only a limited number of synthetic routes have been designed. In particular, asymmetric N-arylation reactions allowing atroposelective N-C bond forming events remain scarce, although great advances have been achieved recently. In this minireview we summarize the synthetic approaches towards synthesis of N-C axially chiral compounds via stereocontrolled N-C bond forming events. Both organo-catalyzed and metal-catalyzed transformations are described, thus illustrating the diversity and specificity of both strategies.

Challenging Atroposelective C–H Arylation

Atropisomeric molecules are privileged scaffolds, not only as ligands for asymmetric synthesis, but also as biologically active products and advanced materials. Although very attractive from a sustainability viewpoint, the direct construction of the stereogenic axis through asymmetric C–H arylation is very challenging and consequently only a few examples have been reported. This short review summarizes these very recent results on the atropo-enantio or diastereo­selective synthesis of atropisomeric (hetero)biaryl molecules; transformations during which the Ar–Ar atropisomeric axis is formed during the C–H activation process.

1 Introduction

2 Atropo-enantioselective Intermolecular Pd-Catalyzed C–H Arylation of Thiophene Derivatives

3 Atropodiastereoselective Intermolecular Pd-Catalyzed C–H Arylation towards Terphenyl Scaffolds Bearing Two Atropisomeric Axes

4 Atropo-enantioselective Intramolecular Pd-Catalyzed C–H Arylation towards Atropisomeric Benzodiazepinones

5 Atropo-enantioselective Intermolecular Pd-Catalyzed C–H Arylation of Heteroarenes

6 Rh-Catalyzed Atropo-enantioselective C–H Arylation of Diazonaphthoquinones

7 Conclusion

New synthesized polyoxygenated diarylheptanoids suppress lipopolysaccharide-induced neuroinflammation

In neurodegenerative diseases, such as Alzheimer's disease, Huntington's disease, Parkinson's disease and multiple sclerosis, neuroinflammation induced by the microglial activation plays a crucial role. In effort to develop effective anti-neuroinflammatory compounds, different new linear polyoxygenated diarylheptanoids were synthesized. In LPS-triggered BV-2 microglial cells their ability to reduce the concentration of IL-6 and TNF-α pro-inflammatory cytokines was evaluated. Moreover, their effect on NF-κB and ATP citrate lyase (ACLY), a recently emerged target of metabolic reprogramming in inflammation, was assessed. Finally, we turned our attention to inflammatory mediators derived from the cleavage of citrate catalyzed by ACLY: prostaglandin E₂, nitric oxide and reactive oxygen species. All compounds showed null or minimal cytotoxicity; most of them had a great anti-neuroinflammatory activity. Diarylheptanoids 6b and 6c, bearing a halide atom and benzyl ether protective groups, exhibited the best effect since they blocked the secretion of all inflammatory mediators analyzed and reduced NF-κB and ACLY protein levels.

Enantioselective Synthesis of N-C Axially Chiral Compounds by Cu-Catalyzed Atroposelective Aryl Amination

N-C axially chiral compounds have emerged recently as appealing motifs for drug design. However, the enantioselective synthesis of such molecules is still poorly developed and surprisingly no metal-catalyzed atroposelective N-arylations have been described. Herein, we disclose an unprecedented Cu-catalyzed atroposelective N-C coupling that proceeds at room temperature. Such mild reaction conditions, which are a crucial parameter for atropostability of the newly generated products, are operative thanks to the use of hypervalent iodine reagents as a highly reactive coupling partners. A large panel of the N-C axially chiral compounds was afforded with very high enantioselectivity (up to >99 % ee) and good yields (up to 76 %). Post-modifications of thus accessed atropisomeric compounds allows further expansion of the diversity of these appealing compounds.

Unintended Formation of a 26-Membered Cycle in the Course of a Novel Approach to Myricanol, a Strained [7,0]-Metacyclophane

A convergent approach for the synthesis of (±)-myricanol, a strained diarylheptanoid isolated from Myricacae, was undertaken using a Suzuki–Miyaura coupling followed by a ring-closing metathesis (RCM). Herein, we report the unintentional formation of a 26-membered macrocycle as RCM product resulting from a head-to-tail dimerization of the seco-precursor, even in relay ring-closing metathesis (RRCM) conditions.

Two Stereoinduction Events in One C-H Activation Step: A Route towards Terphenyl Ligands with Two Atropisomeric Axes

Herein we disclose the synthesis of original chiral scaffolds-ortho-orientated terphenyls presenting two atropisomeric Ar-Ar axes. These unusual structures were built up by using the C-H activation approach, and remarkably, both chiral axes were controlled with excellent stereoselectivity in a single transformation. During the reaction, not only does atroposelective functionalization of a biaryl precursor occur to establish one stereogenic axis, but an unprecedented atropo-stereoselective C-H arylation also takes place to generate the second stereogenic element. These enantiomerically pure ortho-terphenyls show an original tridimensional structure and thus constitute a unique foundation for building up a library of enantiomerically pure bidentate ligands, such as the new ligands S/N-Biax and diphosphine BiaxPhos.

Stereospecific C–H activation as a key step for the asymmetric synthesis of various biologically active cyclopropanes

A rapid and efficient synthesis of hoshinolatame, an enantiopure cyclopropane containing natural product, is described.

Convergent total synthesis of (±) myricanol, a cyclic natural diarylheptanoid

Third total synthesis of the meta, meta-bridged diarylheptanoid: myricanol with remarkable anti-tau properties.

Synthesis of an Advanced Fragment of (+)-Trienomycinol

The synthesis of the fully functionalized eastern fragment of trienomycins A–F, ansamycin antibiotics is described. A key step involves a peptidic coupling between a sulfonyl aniline and an enantiopure carboxylic acid obtained by a completely diastereoselective reduction of a β-ketosulfoxide to generate the stereogenic carbinol. Studies on the coupling with the western part were also performed, giving access to an advanced fragment of trienomycinol.

A remarkable solvent effect of fluorinated alcohols on transition metal catalysed C–H functionalizations

Fluorinated solvents like 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) and trifluoroethanol (TFE) have recently emerged as a remarkable synthetic hint allowing challenging C–H activation reactions.

Recent advances and new concepts for the synthesis of axially stereoenriched biaryls

Over the past decade the field of the synthesis of axially chiral compounds has been rapidly expanding. Not only key advances have been achieved concerning the already established strategies but also new synthetic routes have been devised. This review showcases the recent developments in this domain.

Unusual phosphine oxidation: new triazolopyridyl-quinolyl phosphine oxide fluorescent dyes

3-(2-Pyridyl)-[1,2,3]triazolo[1,5-a]quinolylphosphines suffer an unusual phosphine oxidation due to their special geometry that allows a σ-donation of the nitrogen (N1) lone pair to phosphorus.

Atroposelective synthesis of axially chiral P,S-ligands based on arynes

An unprecedented atropo-diastereoselective aryl–aryl coupling via arynes allows for the modular synthesis of enantiopure P,S-ligands.

Determination of the absolute configuration of phosphinic analogues of glutamate

Stereomers of LSP1-2111 have been separated, their absolute configuration and agonist activity at mGlu4R determined.

Isolation, structural determination and synthetic approaches toward amphidinol 3

This review highlights the isolation and the structural determination of amphidinol 3 (AM3), as well as the synthetic efforts to its preparation. The mechanism of action of AM3 will not be developed herein.