Enantioselective Synthesis of a γ-Secretase Modulator via Vinylogous Dynamic Kinetic Resolution

Enantioselective Transformations in the Synthesis of Therapeutic Agents

The proportion of approved chiral drugs and drug candidates under medical studies has surged dramatically over the past two decades. As a consequence, the efficient synthesis of enantiopure pharmaceuticals or their synthetic intermediates poses a profound challenge to medicinal and process chemists. The significant advancement in asymmetric catalysis has provided an effective and reliable solution to this challenge. The successful application of transition metal catalysis, organocatalysis, and biocatalysis to the medicinal and pharmaceutical industries has promoted drug discovery by efficient and precise preparation of enantio-enriched therapeutic agents, and facilitated the industrial production of active pharmaceutical ingredient in an economic and environmentally friendly fashion. The present review summarizes the most recent applications (2008-2022) of asymmetric catalysis in the pharmaceutical industry ranging from process scales to pilot and industrial levels. It also showcases the latest achievements and trends in the asymmetric synthesis of therapeutic agents with state of the art technologies of asymmetric catalysis.

Asymmetric Transfer Hydrogenation of 2,3-Disubstituted Flavanones through Dynamic Kinetic Resolution Enabled by Retro-Oxa-Michael Addition: Construction of Three Contiguous Stereogenic Centers

A ruthenium-catalyzed asymmetric transfer hydrogenation of 2,3-disubstituted flavanones was developed for the construction of three contiguous stereocenters under basic conditions through a combination of dynamic kinetic resolution and retro-oxa-Michael addition, giving chiral flavanols with excellent enantioselectivities and diastereoselectivities. The reaction proceeded via a base-catalyzed retro-oxa-Michael addition to racemize two stereogenic centers simultaneously in concert with a highly enantioselective ketone transfer hydrogenation step. The asymmetric transfer hydrogenation could be achieved at gram scale without loss of the activity and enantioselectivity.

Ru-Catalyzed Enantioselective Hydrogenation of 2-Pyridyl-Substituted Alkenes and Substrate-Mediated H/D Exchange

A highly efficient and enantioselective asymmetric hydrogenation catalyzed by Ru-DTBM-segphos is reported for a broad range of pyridine-pyrroline tri-substituted alkenes. Kinetic, spectroscopic, and computational studies suggest that addition of H₂ is rate-determining and that alkene insertion is the enantio-determining step. These studies also reveal an intriguing Ru-catalyzed H/D exchange process that is facilitated by the substrate at room temperature and low pressure where hydrogenation activity is suppressed. These studies lead to a mechanistic proposal that further defines the roles of hydrogen gas, Ru-H species, and protic solvents in this catalytic system.

Synthesis of functionalized derivatives of the gamma-secretase modulator BMS-932481 and identification of its major metabolite

In an effort to improve physical properties by introducing polar functionality into the bicyclic pyrimidine gamma-secretase modulator (GSM) clinical candidate BMS-932481, we prepared several oxidative products of BMS-932481. Among the analogs that were prepared, the C-5 alcohol 3 was identified as the predominant metabolite of BMS-932481 found in rat and human liver microsomes. Alcohol 3 was determined to be chemically unstable, leading to the hypothesis that 3 may lead to the production of reactive species both in vitro and in vivo.

Escaping from Flatland: Stereoconvergent Synthesis of Three-Dimensional Scaffolds via Ruthenium(II)-Catalyzed Noyori-Ikariya Transfer Hydrogenation

Noyori-Ikariya-type ruthenium(II)-catalysts for asymmetric transfer hydrogenation (ATH) have been known for 25 years and have proved as a well-behaved and user-friendly platform for the synthesis of chiral secondary alcohols. A progress has been made in the past five years in understanding the asymmetric reduction of complex ketones, where up to four stereocenters can be controlled in a single chemical transformation. Intriguing multi-chiral molecular architectures are therefore available in few well understood and robust synthetic steps from commercially available building blocks and possess handles for additional functionalization. The aim of this Review is to showcase the availability of three-dimensional scaffolds and homochiral lead-like compounds via ATH and inspire their direct use in drug discovery endeavors. Basic mechanistic insights are provided to demystify the stereo-chemical outcomes, as well as examples of diastereoselective transformations of enantiopure alcohols to give a feeling of how these rigid non-planar molecules can be further elaborated.

Recent Progress and Applications of Transition-Metal-Catalyzed Asymmetric Hydrogenation and Transfer Hydrogenation of Ketones and Imines through Dynamic Kinetic Resolution

Based on the ever-increasing demand for enantiomerically pure compounds, the development of efficient, atom-economical, and sustainable methods to produce chiral alcohols and amines is a major concern. Homogeneous asymmetric catalysis with transition-metal complexes including asymmetric hydrogenation (AH) and transfer hydrogenation (ATH) of ketones and imines through dynamic kinetic resolution (DKR) allowing the construction of up to three stereogenic centers is the main focus of the present short review, emphasizing the development of new catalytic systems combined to new classes of substrates and their applications as well.

1 Introduction

2 Asymmetric Hydrogenation via Dynamic Kinetic Resolution

2.1 α-Substituted Ketones

2.2 α-Substituted β-Keto Esters and Amides

2.3 α-Substituted Esters

2.4 Imine Derivatives

3 Asymmetric Transfer Hydrogenation via Dynamic Kinetic Resolution

3.1 α-Substituted Ketones

3.2 α-Substituted β-Keto Esters, Amides, and Sulfonamides

3.3 α,β-Disubstituted Cyclic Ketones

3.4 β-Substituted Ketones

3.5 Imine Derivatives

4. Conclusion

Identification and Preclinical Evaluation of the Bicyclic Pyrimidine γ-Secretase Modulator BMS-932481

A triazine hit identified from a screen of the BMS compound collection was optimized for potency, in vivo activity, and off-target profile to produce the bicyclic pyrimidine γ-secretase modulator BMS-932481. The compound showed robust reductions of Aβ_1-42 and Aβ_1-40 in the plasma, brain, and cerebrospinal fluid of mice and rats. Consistent with the γ-secretase modulator mechanism, increases in Aβ_1-37 and Aβ_1-38 were observed, with no change in the total amount of Aβ_1-x produced. No Notch-based toxicity was observed, and the overall preclinical profile of BMS-932481 supported its further evaluation in human clinical trials.