Palladium catalysts for highly selective Sonogashira reactions of aryl and heteroaryl bromides

Phenyl dialkynylcarbinols, a Bioinspired Series of Synthetic Antitumor Acetylenic Lipids

A series of 25 chiral anti-cancer lipidic alkynylcarbinols (LACs) were devised by introducing an (hetero)aromatic ring between the aliphatic chain and the dialkynylcarbinol warhead. The resulting phenyl-dialkynylcarbinols (PACs) exhibit enhanced stability, while retaining cytotoxicity against HCT116 and U2OS cell lines with IC50 down to 40 nM for resolved eutomers. A clickable probe was used to confirm the PAC prodrug behavior: upon enantiospecific bio-oxidation of the carbinol by the HSD17B11 short-chain dehydrogenase/reductase (SDR), the resulting ynones covalently modify cellular proteins, leading to endoplasmic reticulum stress, ubiquitin-proteasome system inhibition, and apoptosis. Insights into the design of LAC prodrugs specifically bioactivated by HSD17B11 vs its paralogue HSD17B13 were obtained. The HSD17B11/HSD17B13-dependent cytotoxicity of PACs was exploited to develop a cellular assay to identify specific inhibitors of these enzymes. A docking study was performed with the HSD17B11 AlphaFold model, providing a molecular basis of the SDR substrates mimicry by PACs. The safety profile of a representative PAC was established in mice.

Total Synthesis of (+)-Shearilicine

Herein we report the first total synthesis of the indole diterpenoid natural product shearilicine by an 11-step sequence via a generalizable precursor to the highly oxidized subclass of indole diterpenoids. A native chiral auxiliary strategy was employed to access the target molecule in an enantiospecific fashion. The formation of the key carbazole substructure was achieved through a mild intramolecular Heck cyclization, wherein a computational study revealed noncovalent substrate-ligand and ligand-ligand interactions that promoted migratory insertion.

Pd-Catalyzed decarboxylative alkynylation of alkynyl carboxylic acids with arylsulfonyl hydrazides via a desulfinative process

The decarboxylative alkynylation of alkynyl carboxylic acids and arylsulfonyl hydrazides by desulfinative coupling could provide aryl alkynes in satisfactory yields by either judiciously selecting palladium catalysts or modulating phosphine ligands under mild conditions.

Pd-tetrahydrosalan-type complexes as catalysts for sonogashira couplings in water: efficient greening of the procedure

New sulfonated tetrahydrosalen-type ligands and their water-soluble palladium(II) complexes have been synthesized. The palladium(II) complexes catalyze the Sonogashira coupling (23 examples) of various aryl halides (including chloroarenes) with terminal alkynes, with good to excellent conversions under mild conditions (80°C, air, no Cu(I) cocatalyst) in aqueous-organic mixtures and turnover frequencies of up to 2790 h(-1) . Under optimized reaction conditions to minimize environmental contamination, diphenylacetylenes can be isolated in 76-98% yield. The aqueous catalyst solution can be recycled four times with decreasing activity; however, yields between 93 and 98% can still be achieved with extended reaction times. Several water-insoluble products can be isolated in excellent yield by simple filtration and purification by washing with water; this method is used, for the first time, for this type of C-C coupling procedure.

Discovery of a potent and selective free fatty acid receptor 1 agonist with low lipophilicity and high oral bioavailability

The free fatty acid receptor 1 (FFA1, also known as GPR40) mediates enhancement of glucose-stimulated insulin secretion and is emerging as a new target for the treatment of type 2 diabetes. Several FFA1 agonists are known, but the majority of these suffer from high lipophilicity. We have previously reported the FFA1 agonist 3 (TUG-424). We here describe the continued structure-activity exploration and optimization of this compound series, leading to the discovery of the more potent agonist 40, a compound with low lipophilicity, excellent in vitro metabolic stability and permeability, complete oral bioavailability, and appreciable efficacy on glucose tolerance in mice.

Palladium-catalyzed carbonylative Heck reaction of aryl bromides with vinyl ethers to 3-alkoxy alkenones and pyrazoles

Three COming together: The first carbonylative Heck coupling reaction of aryl bromides and vinyl ethers leading to 1-aryl-3-alkoxy-2-propen-1-ones has been established (see scheme). Based on this coupling methodology, a novel one-pot synthesis of aryl-substituted pyrazoles was also realized.

Identification of a potent and selective free fatty acid receptor 1 (FFA1/GPR40) agonist with favorable physicochemical and in vitro ADME properties

The free fatty acid receptor 1 (FFA1, also known as GPR40) enhances glucose-stimulated insulin secretion from pancreatic β-cells and is recognized as an interesting new target for treatment of type 2 diabetes. Several series of selective FFA1 agonists are already known. Most of these are derived from free fatty acids (FFAs) or glitazones and are relatively lipophilic. Aiming for the development of potent, selective, and less lipophilic FFA1 agonists, the terminal phenyl of a known compound series was replaced by nitrogen containing heterocycles. This resulted in the identification of 37, a selective FFA1 agonist with potent activity on recombinant human FFA1 receptors and on the rat insulinoma cell line INS-1E, optimal lipophilicity, and excellent in vitro permeability and metabolic stability.

Ruthenium-catalyzed selective monoamination of vicinal diols

The monoamination of vicinal diols in the presence of in situ generated ruthenium catalysts has been investigated. Among the various phosphines tested in combination with [Ru(3)(CO)(12)], N-phenyl-2-(dicyclohexyl-phosphanyl)pyrrole showed the best performance. After optimization of the reaction conditions this system was applied to different secondary amines and anilines as well as a number of vicinal diols. With the exception of ethylene glycol, monoamination of the vicinal diols occurred selectively and the corresponding amino alcohols were obtained in good yields, producing water as the only side product.

Sequential and selective Buchwald-Hartwig amination reactions for the controlled functionalization of 6-bromo-2-chloroquinoline: synthesis of ligands for the Tec Src homology 3 domain

Src homology 3 (SH3) domains are highly conserved protein-protein interaction domains that mediate important biological processes and are considered valuable targets for the development of therapeutic agents. In this paper, we report the preparation of a range of new 6-heterocyclic substituted 2-aminoquinolines using Buchwald-Hartwig chemistry. 6-Heterocyclic substitution of the 2-aminoquinoline has provided ligands with increased binding affinity for the SH3 domain relative to the lead compound, 2-aminoquinoline, that are the highest affinity ligands prepared to date. The key step in the synthesis of these compounds required a selective Buchwald-Hartwig amination of an aryl bromide in the presence of an activated heteroaryl chloride. The optimization of reaction conditions to achieve the selective amination is discussed and has allowed for cross-coupling with a range of cyclic amines. Introduction of the amino functionality of the 6-heterocyclic 2-aminoquinolines involved additional Buchwald-Hartwig chemistry utilizing lithium bis(trimethylsilyl)amide as an ammonia equivalent.

Rh-catalyzed asymmetric hydrogenation of unsaturated lactate precursors in propylene carbonate

The asymmetric hydrogenation of alpha-acetoxy acrylates to O-acetyl lactates with Rh catalysts based on chiral bisphospholane ligands was investigated in propylene carbonate (PC) as "green" solvent. In contrast to DuPHOS-type ligands, catASium M ligands lead to full conversion of the substrate in PC and induce excellent enantioselectivities for ethyl ester and methyl ester substrates (>98 %). Moreover, the undesired opening of the maleic anhydride moiety of the catASium M ligand observed in MeOH can be prevented under these conditions. The chiral product can be easily separated from the carbonate solvent by distillation. In this way, an ecologically benign process for the production of enantiopure lactic acid derivatives was established which offers a highly efficient catalytic transformation in a green solvent under mild conditions (1-10 bar H(2)).