Dearomatizing anionic cyclization of phosphonamides.: A route to phosphonic acid derivatives with antitumor properties

Deprotonation of bis(N-benzyl-N-methyl)-P-arylphosphonic diamides with s-BuLi in THF at -90 degrees C takes place selectively at the benzylic position. The anions undergo intramolecular attack to the P-aryl ring leading to dearomatized species that were trapped with a series of electrophiles (MeOH, ArOH, BnBr, aliphatic and aromatic aldehydes, and benzophenone) in very high yield, and with high regio- and stereocontrol. The dearomatized products were smoothly transformed into gamma-aminophosphonic acids under acidic conditions. Preliminary screening for antitumor activity showed promising levels of activity.