Defence of doctoral thesis: Kaiheng Zhang –Hiqhly enantioselective synthesis of lactam and sugar derivatives by chiral aminocatalysis and merging with transition metal catalysis

This thesis presented novel methodologies for enantioselective synthesis of highly functionalized lactam and sugar derivatives. Asymmetric organocatalysis, cooperative dual catalysis and one-pot multicomponent reaction strategies were applied for the construction of continuous and quaternary stereogenic center.

In Chapter II, a unique strategy for enantioselective synthesis of bicyclic lactam N,S-acetals scaffolds was developed. The reaction intiates from an aminocatalyzed transformation. Next, the addition of thiol amine leads to the construction of bicyclic lactams via a imine/N,S-acetal formation/lactamization cascade sequence.

Chapter III focuses on a stereodivergent synthesis of fluorinated lactams bearing two vicinal stereogenic centers by multicomponent reaction. The reaction proceeds via enantioselective Michael addition /imine formation/lactamization cascade process. The reaction solvent used in the lactamizarion step gives switchable diastereoselectivity to the fluorinated quaternary stereocenter. DFT calculation revealed a mechanistic insight into the unexpected diastereoselectivity.

The usefulness of fluorinated lactams was demonstrated in fluorinated drug analogue synthesis. Chapter IV illustrates a new enantioselective allylic alkylation of acetonide protected trioses and furanosides by merging enamine catalysis with transition metal catalysis. An intrinsic sugar-assisted kinetic resolution mechanism between aldehyde and aminocatalyst was proposed and monitored in NMR studies.

Chapter V is about a new chiral amine-catalyzed C4’ α-aminomethyl-ation of furanoside and nucleoside derived C5’ aldehydes. The C4’ aminomethyl functionalized furanoside precursors have potentials for new nucleoside analogue synthesis.

Link to thesis: http://miun.diva-portal.org/smash/record.jsf?pid=diva2%3A1742161&dswid=-2903