Flow synthesis of cyclobutanones via [2 + 2] cycloaddition of keteneiminium salts and ethylene gas

A robust and safe flow method for the synthesis of mono-substituted cyclobutanones.

Conformational restriction: an effective tactic in 'follow-on'-based drug discovery

The conformational restriction (rigidification) of a flexible ligand has often been a commonly used strategy in drug design, as it can minimize the entropic loss associated with the ligand adopting a preferred conformation for binding, which leads to enhanced potency for a given physiological target, improved selectivity for isoforms and reduced the possibility of drug metabolism. Therefore, the application of conformational restriction strategy is a core aspect of drug discovery and development that is widely practiced by medicinal chemists either deliberately or subliminally. The present review will highlight current representative examples and a brief overview on the rational design of conformationally restricted agents as well as discuss its advantages over the flexible counterparts.

Diastereoselective multicomponent cascade reaction leading to [3.2.0]-heterobicyclic compounds

A general three-component triple cascade reaction through an iminium-enamine-iminium sequential activation initiated by a hetero-Michael addition to α,β-unsaturated aldehydes affords [3.2.0]heterobicycles in high diastereoselectivity. The rate and diastereoselectivity of the reaction depended on the (E)-4-heterocrotonate and size of the secondary amine. The enantiomers of the major diastereoisomer of oxa- and azabicyclo[3.2.0]heptane derivatives were separated by enzymatic kinetic resolution with immobilized Candida antarctica Lipase B (CALB), with E values up to 153. The absolute configuration of the nonacylated enantiomer of oxabicyclo[3.2.0]heptane was determined by single crystal X-ray analysis.