Inventing and understanding catalytic, enantioselective reactions.

This review summarizes recent advances in the development of efficient routes based on enantioselective catalysis for the synthesis of optically active therapeutic agents. Particular emphasis is placed on research that has streamlined the large-scale production of therapeutics for the treatment of type 2 diabetes mellitus (T2DM). Progress in the catalytic asymmetric hydrogenation and amination of unprotected substrates has enabled the establishment of concise synthetic routes for the production of the potent dipeptidyl peptidase 4 inhibitor sitagliptin, and the aldose reductase inhibitor ranirestat (Dainippon Sumimoto Pharma Co Ltd/Eisai Co Ltd/ Kyorin Pharmaceutical Co Ltd), both of which have attracted particular attention for their potential to treat T2DM and diabetic complications, respectively.

Managing highly coordinative substrates in asymmetric catalysis: a catalytic asymmetric amination with a lanthanum-based ternary catalyst.

Full details of a catalytic asymmetric amination with a lanthanum/amide-based ligand catalyst system are described. A catalyst comprising La(NO(3))(3)*6H(2)O, (R)-3a and H-d-Val-O(t)Bu was identified to promote the catalytic asymmetric amination of nonprotected succinimide derivative 1 with as little as 1 mol % catalyst loading. Mechanistic studies by various spectroscopic analyses and several control and kinetic experiments suggested that the catalyst components were in equilibrium between the associated and dissociated forms, and that the reaction likely proceeded through a La(NO(3))(3)*6H(2)O/(R)-3a/H-d-Val-O(t)Bu ternary complex. This catalyst system was also effective for asymmetric amination of N-nonsubstituted alpha-alkoxycarbonyl amides 7, hitherto unprecedented substrates in asymmetric catalysis, probably due to their attenuated reactivity and difficult stereocontrol, affording the amination products in up to >99% yield and >99% ee. The high catalytic performance and enantiocontrol of the reaction with highly coordinative substrates were achieved by the activation/recognition of the substrates exerted by coordination to lanthanum and hydrogen bonding cooperatively in the transition state.

An improved lanthanum catalyst system for asymmetric amination: toward a practical asymmetric synthesis of AS-3201 (Ranirestat).

A catalytic asymmetric amination with a lanthanum/amide complex was significantly improved. The use of lanthanum nitrate hydrate in place of lanthanum triisopropoxide made the process reproducible, scalable, and cost-effective. The development of a ternary catalytic system of La/ligand/amine was a key to high ee and catalytic turnover. A 100 g scale reaction was performed to showcase a practical synthesis of a key intermediate for AS-3201, a highly potent aldose reductase inhibitor.