An expedient copper-catalysed asymmetric synthesis of γ-lactones and γ-lactams. Application to the synthesis of lucidulactone A

The parent Josiphos ligand gave excellent ee values (95-99%) and good yields (60-97%) in the copper-catalysed asymmetric conjugate reduction of β-aryl α,β-unsaturated lactones and lactams with PMHS. The substrates were obtained from stereospecific copper-catalysed addition of arylboronic acids to alkynoates followed by deprotection and cyclisation. The acyclic lactam precursors also underwent reduction with good ee values (83-85%) and yields (79-95%). Application of this asymmetric reduction methodology included the synthesis of natural product lucidulactone A.