The pluses and minuses of mefloquine: A highly enantioselective catalytic borylative isomerization/aldehyde allylboration method for the stereoselective synthesis of the antimalarial drug mefloquine was optimized, thus leading to an efficient synthesis of all four mefloquine stereoisomers and analogues (see scheme). The absolute configuration of these potent compounds was determined for the first time by using chemical synthesis.

Non-aromatic nitrogen-and oxygen-containing heterocycles such as piperidines and pyrans are prevalent components of natural products and pharmaceutical drugs. Although it has been a workhorse as a synthetic method for assembling unsaturated sp 2 -hybridized substrates, transition metal-catalysed cross-coupling chemistry is traditionally not a suitable approach to prepare chiral non-aromatic heterocycles. Several mechanistic issues hamper the coupling of stereogenic secondary sp 3 -hybridized carbon-metal centres. Moreover, use of unsymmetrical allylic boronates in the Suzuki Miyaura cross-coupling is further complicated by the possibility of forming two regioisomeric products. Here we address this two-pronged problem and demonstrate that chiral enantiomerically enriched heterocyclic allylic boronates can be coupled with high stereochemical retention with a wide variety of aryl and alkenyl halides to independently afford both regioisomeric 2-and 4-substituted dihydropyrans and dehydropiperidines in high selectivity. A divergent mechanism is proposed where regiochemistry is governed by the nature of the ligands on the palladium catalyst. This scalable method is applied to the efficient preparation of the neuroactive alkaloid anabasine and the antidepressant drug paroxetine.

A new methodology has been developed for the stereoselective preparation of β-aryl-β-boronyl α,β-unsaturated esters via Heck coupling, and their subsequent copper(I)-catalyzed enantioselective conjugate reduction. Various chiral secondary boronate derivatives can be accessed in excellent yields and good to high levels of enantioselectivity through the efficient copper-catalyzed process using polymethylhydrosiloxane (PMHS) as the hydride source.

Plus und Minus von Mefloquin: Die Optimierung einer hoch enantioselektiven Methode mit katalytischer borylierender Isomerisierung und Aldehyd‐Allylborierung für die stereoselektive Synthese von Mefloquin macht alle vier Stereoisomere des Antimalariawirkstoffs (siehe Schema) und seiner Analoga zugänglich. Die absolute Konfiguration dieser Verbindungen wurde erstmals über eine chemische Synthese bestimmt.

No abstract