SmI2-Mediated Coupling of Nitrones and tert-Butanesulfinyl Imines with Allenoates: Synthesis of β-Methylenyl-γ-lactams and Tetramic Acids
摘要:
Nitrones and tert-butanesulfinyl imines undergo conjugate addition to alkyl allenoates under SmI2-mediated reductive coupling conditions to produce novel beta-methylenyl-substituted gamma-amino esters. The latter were readily transformed into the corresponding beta-methylenyl-gamma-lactams by simple zinc reduction (N-hydroxy amines) or by acid hydrolysis (sulfinamides). The diastereoselective preparation of various beta-methylenyl-gamma-lactams offers a route to tetramic acids, the key structural features of an important class of bioactive natural products.