Asymmetric synthesis of ketoprofen: a surprising base catalyst effect during asymmetric addition of pantolactone to methyl (3-benzoylphenyl) ketene

Article abstract of DOI:10.1016/S0040-4020(01)81339-9

The best diastereoselectivity of addition of a chiral alcohol to the ketene derived from ketoprofen was obtained with R or S pantolactone (ed=99percent).Depending on the tertiary amine used both for ketene formation and as catalyst during addition, the diastereoisomeric ratio of esters could be strongly modified and even inverted.Mild saponification afforded R or S ketoprofen in enantiomeric excess of up to 99percent.