We report a concise, enantio- and diastereoselective route to novel nonsymmetrically substituted N-protected β,β-diaryl-α-amino acids and esters, through the asymmetric hydrogenation of tetrasubstituted olefins, some of the most challenging examples in the field. Stereoselective generation of an E- or Z-enol tosylate, when combined with stereoretentive Suzuki-Miyaura cross-coupling and enantioselective hydrogenation catalyzed by (NBD)2RhBF4 and a Josiphos ligand, allows for full control over the two vicinal stereogenic centers. High yields and excellent enantioselectivities (up to 99% ee) were obtained for a variety of N-acetyl, N-methoxycarbonyl, and N-Boc β,β-diaryldehydroamino acids, containing a diverse and previously unreported series of heterocyclic and aryl substituted groups (24 examples) and allowing access to all four stereoisomers of these valuable building blocks.
The synthesis of diversely substituted 1,3,5-substituted pyrazoles from the reaction of acetylenic ketones with substituted hydrazines is reported. The reactions were shown to be highly regioselective regardless of the nature of the substituents in the substrates and afforded essentially single pyrazole isomers in excellent yields.
Vortioxetine is an orally administered small molecule developed by Lundbeck A/S for the once-daily treatment of major depressive disorder (MDD) and generalized anxiety disorder (GAD). Vortioxetine received its first global approval for MDD in the USA in September 2013 and regulatory approval for its use in this indication in the EU (where it has received a positive opinion) and Canada is awaited. The drug is a bis-aryl-sulphanyl amine compound that combines serotonin (5-HT) reuptake inhibition with other characteristics, including receptor activity modulation. In vitro studies indicate that vortioxetine is an inhibitor of the 5-HT transporter and is a 5-HT(1D), 5-HT₃ and 5-HT₇ receptor antagonist, a 5-HT(1A) receptor agonist and a 5-HT(1B) receptor partial agonist. Animal and in vitro studies indicate that several neurotransmitter systems may be impacted by vortioxetine, with the drug enhancing levels of 5-HT, noradrenaline, dopamine, acetylcholine and histamine in certain areas of the brain, as well as modulating γ-aminobutyric acid and glutamate neurotransmission. Phase III trials of vortioxetine in both MDD and GAD have been conducted worldwide. This article summarizes the milestones in the development of vortioxetine leading to this first approval for MDD.
A practical synthesis of a highly functionalized tetrahydropyran DPP-4 inhibitor is described. The asymmetric synthesis relies on three back-to-back Ru-catalyzed reactions. A Ru-catalyzed dynamic kinetic resolution (DKR) reduction establishes two contiguous stereogenic centers in one operation. A unique dihydropyran ring is efficiently constructed through a preferred Ru-catalyzed cycloisomerization. Hydroboration followed by a Ru-catalyzed oxidation affords the desired functionalized pyranone core scaffold. Finally, stereoselective reductive amination and subsequent acidic deprotection afford the desired, potent DPP-4 inhibitor in 25% overall yield.
A practical asymmetric synthesis of the estrogen receptor beta selective agonist (7β-9aβ)-1,4-dichloro-2-hydroxygibba-1(10a),2,4,4b-tetraen-6-one (1), proceeding by way of six isolated intermediates and without recourse to chromatography, is described. Highlights of the process route developed are two chemoselective chlorinations, a lithiated hydrazone alkylation and an asymmetric Michael addition of indanone 11 to methyl vinyl ketone (using 15 mol % of cinchonine-derived catalyst 20g) to set the all-carbon quaternary asymmetric stereocenter. The challenges addressed in scaling the latter heterogeneous biphasic phase transfer reaction to 44 mol (14 kg) scale are discussed in detail. Overall, the chemistry developed has been used to prepare >6 kg of drug candidate 1 in 18% overall yield and with >99% ee.
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