Miyaura borylation/Suzuki-Miyaura coupling (MBSC) sequence of 4-bromo-2,4'-bithiazoles with halides: straightforward access to a heterocylic cluster of d-series of thiopeptide GE2270.

Herein, palladium-catalyzed Miyaura borylation of 4-bromo-2,4'-bithiazoles followed by Suzuki-Miyaura cross-coupling reaction (named the MBSC process) with (hetero)aryl- and alkenyl halides is reported. This methodology offers rapid access to various 2',4-disubstituted 2,4'-bithiazole features including naturally-occurring 4-alkenylated and 4-pyridinylated 2,4'-bithiazoles. To prove its application, a concise approach for the synthesis of a heterocyclic cluster of the thiopeptide d-series antibiotic GE2270 is reported through a late-stage MBSC strategy.

Synthesis of the heterocyclic core of the D-series GE2270.

A straightforward enantiomerically pure synthesis of the heterocyclic core of the D-series GE2270 is reported. The synthetic strategy combines the Hantzsch thiazole's building condensation with a cross-coupling reaction including direct C-H hetarylation to build and connect step-by-step thiazolyl moieties to the 5-bromopicolinate as readily available starting material.

Dihydroquinoline Carbamate Derivatives as "Bio-oxidizable" Prodrugs for Brain Delivery of Acetylcholinesterase Inhibitors: [¹¹C] Radiosynthesis and Biological Evaluation.

With the aim of improving the efficiency of marketed acetylcholinesterase (AChE) inhibitors in the symptomatic treatment of Alzheimer's disease, plagued by adverse effects arising from peripheral cholinergic activation, this work reports a biological evaluation of new central AChE inhibitors based on an original "bio-oxidizable" prodrug strategy. After peripheral injection of the prodrug 1a [IC50 > 1 mM (hAChE)] in mice, monitoring markers of central and peripheral cholinergic activation provided in vivo proof-of-concept for brain delivery of the drug 2a [IC50 = 20 nM (hAChE)] through central redox activation of 1a. Interestingly, peripheral cholinergic activation has been shown to be limited in time, likely due to the presence of a permanent positive charge in 2a promoting rapid elimination of the AChE inhibitor from the circulation of mice.

Recent advances in direct C-H arylation: Methodology, selectivity and mechanism in oxazole series.

Catalytic direct (hetero)arylation of (hetero)arenes is an attractive alternative to traditional Kumada, Stille, Negishi and Suzuki-Miyaura cross-coupling reactions, notably as it avoids the prior preparation and isolation of (hetero)arylmetals. Developments of this methodology in the oxazole series are reviewed in this article. Methodologies, selectivity, mechanism and future aspects are presented.

DPO and POPOP carboxylate-analog sensors by sequential palladium-catalysed direct arylation of oxazole-4-carboxylates.

Sequential palladium-catalysed direct (het)arylation of oxazole-4-carboxylates is achieved to give rapid access to DPO and POPOP (di)carboxylate-analogs. Three novel DPO- and POPOP-type sensors with unusual Stokes shifts and high quantum yields are discovered.

Evidence of benzilic rearrangement during the electrochemical oxidation of D-glucose to D-glucaric acid.

During the course of the 2,2,6,6-tetramethyl-1-piperidinyloxy free radical-catalyzed electrochemical oxidation of D-glucose to D-glucaric acid a new side-product was observed. This compound was isolated and identified as a tricarboxylic acid of unique structure, which was named maribersonic acid. Its structure was proven by different experiments coupled with several analytical methods, and its appearance during the electrochemical oxidation of D-glucose was rationalized through a thorough study.

Ortho-directed functionalization of arenes using magnesate bases.

Ortho-directed functionalisation of arenes using lithium alkylmagnesate bases were achieved, demonstrating the potential use of arylmagnesates as suitable arylanions, without a further transmetallation step, for challenging functionalizations such as fluorination, hydroxylation, arylation, vinylation and alkylation through epoxide ring-opening.

Design of silicon-based misonidazole analogues and (18)F-radiolabelling.

Introduction: Development of new (18)F-labeled tracers for positron emission tomography (PET) imaging is increasingly important. Herein, we described the synthesis of silicon analogues of [(18)F]fluoromisonidazole in order to develop new radiolabelled compounds for the detection of tumour hypoxic domain. Their stabilities and their in vivo biodistribution were evaluated.

Synthesis, radiosynthesis and biological evaluation of 1,4-dihydroquinoline derivatives as new carriers for specific brain delivery.

In spite of numerous reports dealing with the use of 1,4-dihydropyridines as carriers to deliver biological active compounds to the brain, this chemical delivery system (CDS) suffers from poor stability of the 1,4-dihydropyridine derivatives towards oxidation and hydration reactions seriously limiting further investigations in vivo. In an attempt to overcome these limitations, we report herein the first biological evaluation of more stable annellated NADH models in the quinoline series as relevant neuroactive drug-carrier candidates. The radiolabeled 1,4-dihydroquinoline [(11)C] was prepared to be subsequently peripherally injected in rats.

TBD-organocatalysed synthesis of pyrazolines.

It was found that TBD, a cheap and commercially available guanidine, easily catalysed the synthesis of biologically important 3,5-diarylpyrazolines from chalcones and acylhydrazines via a selective secondary amine alkylation.

Highly efficient borylation Suzuki coupling process for 4-bromo-2-ketothiazoles: straightforward access to micrococcinate and saramycetate esters.

The first palladium-catalyzed borylation of 4-bromo-2-ketothiazoles followed by a Suzuki cross-coupling reaction with haloheteroaromatics using Buchwald's Cy-JohnPhos and XPhos ligands is reported. The methodology has allowed the fast preparation of highly valuable 4-pyridinyl- and 4-thiazolyl-2-ketothiazoles as common subunits of thiopeptide antibiotics. As direct applications, novel concise syntheses of a sulfomycinamate thio-analogue as well as micrococcinate and saramycetate esters are described.

Rational design of central selective acetylcholinesterase inhibitors by means of a "bio-oxidisable prodrug" strategy.

This work deals with the design of a bio-oxidisable prodrug strategy for the development of new central selective acetylcholinesterase inhibitors. This prodrug approach is expected to reduce peripheral anticholinesterase activity responsible for various side effects observed with presently marketed AChE inhibitors. The design of these new AChE inhibitors in quinoline series is roughly based on cyclic analogues of rivastigmine.

Product-catalyzed addition of alkyl nitriles to unactivated imines promoted by sodium aryloxide/ethyl(trimethylsilyl)acetate (ETSA) combination.

The first transition-metal-free addition of alkyl nitriles to unactivated imines was developed using a catalytic combination of 4-MeOC(6)H(4)ONa and TMSCH(2)CO(2)Et to promote the reaction. The corresponding beta-amino nitriles are obtained in good to almost quantitative isolated yields under mild conditions. A mechanism involving an autocatalytic pathway is proposed on the basis of experimental observations.

Direct palladium-catalyzed alkenylation, benzylation and alkylation of ethyl oxazole-4-carboxylate with alkenyl-, benzyl- and alkyl halides.

The ethyl oxazole-4-carboxylate was directly and regioselectively alkenylated, benzylated and alkylated with alkenyl-, benzyl-, allyl- and alkyl halides in the presence of catalytic amounts of palladium acetate with caesium carbonate using Buchwald's JohnPhos ligand.

Aminoacid-derived mercaptoimidazoles.

Starting from suitably protected amino acids, mercaptoimidazoles were synthesized either from the acid or including the amine nitrogen itself. A preliminary optimisation study led to efficient conditions for the obtention of the imidazole ring. These conditions are compatible with the presence of amino acid or dipeptide scaffolds.

Palladium-catalyzed direct (hetero)arylation of ethyl oxazole-4-carboxylate: an efficient access to (hetero)aryloxazoles.

A straightforward route toward 2-(hetero)arylated and 2,5-di(hetero)arylated oxazoles through regiocontrolled palladium-catalyzed direct (hetero)arylation of ethyl oxazole-4-carboxylate with iodo-, bromo-, and chloro(hetero)aromatics followed by a two-step hydrolysis/decarboxylation sequence was described. The method was applied here to a neat synthesis of two 2,5-di(hetero)aryloxazole natural products, balsoxin and texaline.

Direct C-2 arylation of alkyl 4-thiazolecarboxylates: new insights in synthesis of heterocyclic core of thiopeptide antibiotics.

The Pd(0)-catalyzed regioselective C-2 (hetero)arylation of tert-butyl 4-thiazolecarboxylate with a broad (hetero)aryl halide is reported, including the direct coupling of pyridinyl halides. The process has allowed the preparation of valuable 2-pyridynyl-4-thiazolecarboxylates which are components of the complex heterocyclic core of thiopeptides antibiotics. As a first application, a synthesis of a tert-butyl sulfomycinamate thio-analogue from tert-butyl 4-thiazolecarboxylate is here described through a three-step direct pyridinylation, halogenation, and Stille cross-coupling sequence.

A concise synthesis of lentiginosine derivatives using a pyridinium formation via the Mitsunobu reaction.

A four-step synthesis of (-)-lentiginosine and its epimers is described starting from 2-bromopyridine. The key step consisted of a quaternarization of a fully unprotected pyridinium-polyol unit using Mitsunobu methodology. Subsequent PtO(2)-catalyzed diastereoselective hydrogenation of the pyridinium ring proceeded smoothly and led to the expected dihydroxyindolizidines with excellent yields.

Preparation of new axially chiral bridged 2,2'-bipyridines and pyridyl monooxazolines (pymox). Evaluation in copper(I)-catalyzed enantioselective cyclopropanation.

This work reports the synthesis of new axially chiral bridged 2,2'-bipyridines 1 and pyridylmonooxazolines (pymox) 2. The potential of these new axially chiral N,N-ligands was evaluated in asymmetric catalytic cyclopropanation of styrene derivatives 22a-c with diazoesters 21a,b. While 2,2'-bipyridines 1a-c afforded the corresponding cyclopropanes 23a-f in up to 65% ee, pymoxs 2a-e gave somewhat lower enantioselectivities (up to 53% ee).

Anionic, in situ generation of formaldehyde: a very useful and versatile tool in synthesis.

A very simple, safe and powerful method for the in situ generation of formaldehyde at low temperature in anhydrous conditions is described. This new tool avoids the use of gaseous formaldehyde and is suitable for basic carbon nucleophiles which cannot be generated in aqueous reaction media. Various substrates, including organolithium reagents and enolates, underwent smooth hydroxymethylation showing the versatility of this process.

Unusual sterically controlled regioselective lithiation of 3-bromo-5-(4,4'-dimethyl)oxazolinylpyridine. Straightforward access to highly substituted nicotinic acid derivatives.

[Structure: see text] Lithiation of 5-bromonicotinic acid protected as secondary or tertiary amide as well as (4,4'-dimethyl)oxazoline with lithium amides is reported. The unusual C-2 and C-4 regioselective lithiation of 3-bromo-5-(4,4'-dimethyl)oxazolinylpyridine using LTMP versus LDA was observed, providing a new route to substituted nicotinic acid scaffolds. The methodology was applied to the synthesis of novel C-4 and C-6 arylated 5-bromonicotinic acids.

A new synthetic approach to biaryls of the rhazinilam type. Application to synthesis of three novel phenylpyridine-carbamate analogues.

The synthesis of three novel racemic phenylpyridine-carbamate analogues of rhazinilam and their biological evaluation as inhibitors of microtubule assembly and disassembly by interaction with tubulin are described. The sterically hindered ortho-disubstituted biaryl unit as the challenging key structural element is first obtained by a sequential regiocontrolled nucleophilic addition of a lithium ortho-lithiohomobenzylic alkoxide species to 3-bromo-5-oxazolyl pyridine as the electrophile and a subsequent oxidation step. The incorporation of the amino group by replacement of the bromide has been achieved using a Buchwald-Hartwig amination coupling.

One-pot synthesis of 2,3-dihydro-pyrrolopyridinones using in situ generated formimines.

A novel one-pot methodology is described for the synthesis of functionalized pyrrolopyridinones using in situ generated formimines and an ortho-lithiated pyridinecarboxamide species. Depending on the reaction conditions, this procedure allows versatile access to aminomethylated pyridinecarboxamides, 2,3-dihydro-pyrrolopyridinones, or 1,1-dialkylated 2,3-dihydro-pyrrolopyridinone derivatives. [reaction: see text]