A New Enantioselective Synthesis of the Anticonvulsant Drug Pregabalin (Lyrica) Based on a Hydrolytic Kinetic Resolution Method: SYNTHESIS OF ANTICONVULSANT DRUG PREGABALIN

Catalytic enantioselective nitrone cycloadditions enabling collective syntheses of indole alkaloids

Tetrahydro-β-carboline skeletons are prominent and ubiquitous in an extraordinary range of indole alkaloid natural products and pharmaceutical compounds. Powerful synthetic approaches for stereoselective synthesis of tetrahydro-β-carboline skeletons have immense impacts and have attracted enormous attention. Here, we outline a general chiral phosphoric acid catalyzed asymmetric 1,3-dipolar cycloaddition of 3,4-dihydro-β-carboline-2-oxide type nitrone that enables access to three types of chiral tetrahydro-β-carbolines bearing continuous multi-chiral centers and quaternary chiral centers. The method displays different endo/exo selectivity from traditional nitrone chemistry. The distinct power of this strategy has been illustrated by application to collective and enantiodivergent total syntheses of 40 tetrahydro-β-carboline-type indole alkaloid natural products with divergent stereochemistry and varied architectures.

Growing Utilization of Radical Chemistry in the Synthesis of Pharmaceuticals

Our current unhealthy lifestyle and the exponential surge in the population getting affected by a variety of diseases have made pharmaceuticals or drugs an imperative part of life, making the development of innovative strategies for drug discovery or the introduction of refined, cost-effective and modern technologies for the synthesis of clinically used drugs, a need of the hour. Ever since their discovery, free radicals and radical cations or anions as reactive intermediates have captivated the chemists, resulting in an exceptional utilization of these moieties throughout the field of chemical synthesis, owing to their unprecedented and widespread reactivity. Sticking with the idea of not judging the book by its cover, despite the conventional thought process of radicals being unstable and difficult to control entities, scientists and academicians around the globe have done an appreciable amount of work utilizing both persistent as well as transient radicals for a variety of organic transformations, exemplifying them with the synthesis of significant biologically active pharmaceutical ingredients. This review truly accounts for the organic radical transformations including radical addition, radical cascade cyclization, radical/radical cross-coupling, coupling with metal-complexes and radical cations coupling with nucleophiles, that offers fascinating and unconventional approaches towards the construction of intricate structural frameworks of marketed APIs with high atom- and step-economy; complementing the otherwise employed traditional methods. This tutorial review presents a comprehensive package of diverse methods utilized for radical generation, featuring their reactivity to form critical bonds in pharmaceutical total synthesis or in building key starting materials or intermediates of their synthetic journey, acknowledging their excellence, downsides and underlying mechanisms, which are otherwise poorly highlighted in the literature. Despite great achievements over the past few decades in this area, many challenges and obstacles are yet to be unraveled to shorten the distance between the academics and the industry, which are all discussed in summary and outlook.

Enantioselective C(sp3)-C(sp3) cross-coupling of non-activated alkyl electrophiles via nickel hydride catalysis

Cross-coupling of two alkyl fragments is an efficient method to produce organic molecules rich in sp³-hybridized carbon centers, which are attractive candidate compounds in drug discovery. Enantioselective C(sp³)–C(sp³) coupling is challenging, especially of alkyl electrophiles without an activating group (aryl, vinyl, carbonyl). Here we report a strategy based on nickel hydride addition to internal olefins followed by nickel-catalyzed alkyl-alkyl coupling. This strategy enables enantioselective cross-coupling of non-activated alkyl halides with alkenyl boronates to produce chiral alkyl boronates. Employing readily available and stable olefins as pro-chiral nucleophiles, the coupling proceeds under mild conditions and exhibits broad scope and high functional group tolerance. Applications for the functionalization of natural products and drug molecules, as well as the synthesis of chiral building blocks and a key intermediate to (S)-(+)-Pregabalin, are demonstrated.

Total Synthesis of Marine Natural Products Serinolamide A and Columbamide D

In this report, an expeditious synthesis of two new biologically active marine natural products serinolamide A and columbamide D is documented. This convergent approach involves the key steps such as hydrolytic kinetic resolution, cross metathesis, Grignard reaction, Johnson-Claisen rearrangement, Mitsunobu, and so forth. Both of the target molecules were obtained from a common precursor (R)-7 with high enantioselectivity, less synthetic steps, and in good overall yields (serinolamide A 66% and columbamide D 62%).

A new and efficient enantioselective synthesis of both enantiomers of the calcium channel blocker bepridil

We report a simple enantioselective synthesis of bepridil enantiomers employing hydrolytic kinetic resolution and the Mitsunobu reaction as key steps.

Carboxylic acids as a traceless activation group for conjugate additions: a three-step synthesis of (±)-pregabalin

The direct application of carboxylic acids as a traceless activation group for radical Michael additions has been accomplished via visible light-mediated photoredox catalysis. Photon-induced oxidation of a broad series of carboxylic acids, including hydrocarbon-substituted, α-oxy, and α-amino acids, provides a versatile CO2-extrusion platform to generate Michael donors without the requirement for organometallic activation or propagation. A diverse array of Michael acceptors is amenable to this new conjugate addition strategy. An application of this technology to a three-step synthesis of the medicinal agent pregabalin (commercialized by Pfizer under the trade name Lyrica) is also presented.