The development of new methods for the efficient and stereoselective preparation of amine-containing chemical building blocks is a compelling objective in organic synthesis as a large number of biologically active compounds contain an amino group bound to a stereogenic carbon. The chemical functionality that may flank the amine in these compounds is vast, including a number of commonly-encountered motifs, such as amino alcohols and diamines; additionally, the amine-bearing stereogenic center may be tri- or tetrasubstituted. Despite their frequency in targets of biological importance, methods for the stereoselective synthesis of 1,3- diamines, 1,3-amino alcohols, and amino-containing tetrasubstituted stereogenic centers are sparse, with the mode of their generation often labor intensive and/or circuitous. Several scaffolds within these frameworks have only rarely been produced. The long-term goal of this research program is to design and develop novel stereoselective C?C bond-forming methods for preparing difficult-to-access but highly sought-after chiral amines. Our strategy employs a polarity reversal of an imine (umpolung): rather than act as an N-substituted carbon electrophile, we transform the reagent to an N-substituted carbon nucleophile?a 2-azaallyl anion? that may be combined stereoselectively with a number of electrophilic partners to furnish alpha-substituted chiral amines. In these investigations, we will focus on C?C bond formations with 2-azaallyl anions for: 1) the stereoselective synthesis of challenging 1,3-diamine and amino alcohol functionality, 2) the enantioselective preparation of homoallylic amines with N-containing tetrasubstituted stereogenic centers, and 3) stereoselective three component coupling reactions with a silyl-substituted 2-azaallyl anion as a double alpha- amino anion equivalent. The new methods developed under the aegis of this project provide innovative solutions to long-standing challenges in the preparation of chiral amines that will permit streamlined synthesis of several biologically important complex molecules. The new chemical space that will be garnered might enable exploration of novel medicinal leads that may lead to active pharmaceutical ingredients to improve human health.
The ability to access new biologically active molecules that might be advanced to new medicines is hinged upon the facility by which these compounds may be prepared through efficient, selective, and cost-effective methods. The proposed work aims to develop new synthetic methods for the selective assembly of several amine-containing molecules, proven medicinally important motifs but many of which are difficult or cumbersome to access through existing technologies. The proposed research is critical to improving human health as it will enable biologically potent compounds to be generated more quickly or for the first time and assessed as medicinal candidates.
|Li, Kangnan; Shao, Xinxin; Tseng, Luke et al. (2018) 2-Azadienes as Reagents for Preparing Chiral Amines: Synthesis of 1,2-Amino Tertiary Alcohols by Cu-Catalyzed Enantioselective Reductive Couplings with Ketones. J Am Chem Soc 140:598-601|
|Shao, Xinxin; Li, Kangnan; Malcolmson, Steven J (2018) Enantioselective Synthesis of anti-1,2-Diamines by Cu-Catalyzed Reductive Couplings of Azadienes with Aldimines and Ketimines. J Am Chem Soc 140:7083-7087|