The asymmetric transfer and pressure hydrogenation of various unsaturated substrates provides a succinct pathway to important chiral intermediates and products such as chiral alcohols, amines, and alkanes. The use of earth-abundant transition metals such as Fe, Co, Ni, and Cu in hydrogenation reactions provides an attractive alternative to traditionally used metals such as Ru, Rh, Ir, and Pd because they are comparatively inexpensive, less toxic, and as their name suggests, more abundant in nature. Earth-abundant transition metal-catalyzed asymmetric hydrogenation is rapidly becoming an important area of research. This review summarizes advances in the asymmetric hydrogenation of unsaturated bonds (ketones, imines, and alkenes) with earth-abundant transition metals.

Utilizing a chiral bicyclic imidazole organocatalyst and adopting a continuous injection process, an alternative route has been developed for the efficient synthesis of chiral phthalidyl ester prodrugs via dynamic kinetic resolution of 3hydroxyphthalides through enantioselective acylation (up to 99 % ee). The computational studies suggest a general base catalytic mechanism differing from the widely accepted nucleophilic catalytic mechanism. The structure analysis of the key transition states shows that the CH-p interactions and not the previously considered cation/p-p interactions between the catalyst and substrate is the dominant factor giving rise to the observed stereocontrol. Figure 1. Representative ester-based prodrugs.

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A new series of DPP-4 inhibitors with imidazo[1,2-a]pyridine scaffold were designed by exploiting scaffold hopping strategy and docking study. Based on docking binding model, structural modifications of 2-benzene ring and pyridine moieties of compound 5a led to the identification of compound 5d with 2, 4-dichlorophenyl group at the 2-position as a potent (IC50  = 0.13 μm), selective (DPP-8/DPP-4 = 215 and DPP-9/DPP-4 = 192) and in vivo efficacious DPP-4 inhibitor. Further, molecular docking revealed that compound 5d could retain key binding features of DPP-4 with the pyridine moiety of imidazo[1,2-a]pyridine ring providing an additional π-π interaction with Phe357 of DPP-4. Compound 5d might be a promising lead for further development of novel DPP-4 inhibitor treating T2DM.

A new chiral nucleophilic organocatalyst bearing a 5,6,7,8-tetrahydroimidazo[1,2-a]pyridine skeleton has been developed.

The first four-step sequential reaction for the synthesis of Cα-tetrasubstituted chiral α-amino acid derivatives via auto-tandem catalysis has been developed.

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Utilizing a chiral bicyclic imidazole organocatalyst and adopting a continuous injection process, an alternative route has been developed for the efficient synthesis of chiral phthalidyl ester prodrugs via dynamic kinetic resolution of 3hydroxyphthalides through enantioselective acylation (up to 99 % ee). The computational studies suggest a general base catalytic mechanism differing from the widely accepted nucleophilic catalytic mechanism. The structure analysis of the key transition states shows that the CH-p interactions and not the previously considered cation/p-p interactions between the catalyst and substrate is the dominant factor giving rise to the observed stereocontrol. Figure 1. Representative ester-based prodrugs.