R. Scott Hoerrner

A highly enantioselective asymmetric hydrogenation route to β-(2R,3S)-methyltryptophan

Abstract Asymmetric hydrogenation of a protected (Z)-dehydro-β-methyltryptophan derivative 2 with (R,R)-Me-DuPHOS-Rh catalysis was achieved in 97 % ee. Deprotection then afforded (2R,3S)-β-methyltryptophan 1.

Asymmetric synthesis of cis-2,5-disubstituted pyrrolidine, the core scaffold of β3-AR agonists.

A practical, enantioselective synthesis of cis-2,5-disubstituted pyrrolidine is described. Application of an enzymatic DKR reduction of a keto ester, which is easily accessed through a novel intramolecular N→C benzoyl migration, yields syn-1,2-amino alcohol in >99% ee and >99:1 dr. Subsequent hydrogenation of cyclic imine affords the cis-pyrrolidine in high diastereoselectivity. By integrating biotechnology into organic synthesis and isolating only three intermediates over 11 steps, the core scaffold of β3-AR agonists is synthesized in 38% overall yield.