β-Lactams from Carbohydrates

Expanding the Chemical Space of Electrophilic β-Glycosyl β-Lactams through Photoinduced Diastereoselective Functionalization

Herein, we present a photoinduced diastereoselective C-3 functionalization of electrophilic β-glycosyl β-lactams. The developed protocol is simple, mild, and scalable and explores the use of 3-exomethylene β-lactams as reaction partners in a Giese type reaction. The key nucleophilic alkyl radical is generated by a photoinduced electron transfer process in the EDA complex formed by NHPI and Hantzsch esters. The diastereoselective hydrogen atom transfer to the β-lactam radical intermediate enables the synthesis of various N-phenyl β-glycosyl β-lactams.

A formal synthesis of ezetimibe via cycloaddition/rearrangement cascade reaction

A formal synthesis of a powerful cholesterol inhibitor, ezetymibe 1, is described. The crucial step of the synthesis is based on Cu(I)-mediated Kinugasa cycloaddition/rearrangement cascade reaction between terminal acetylene derived from acetonide of L-glyceraldehyde and suitable C,N-diarylnitrone. The adduct with (3R,4S) configuration at the azetidinone ring, obtained with high stereoselectivity, was subsequently subjected to deprotection of the diol side chain followed by glycolic cleavage and base-induced isomerization at the C3 carbon atom to afford the (3S,4S) aldehyde, which has been already transformed into ezetimibe by the Schering-Plough group.