Polymer-supported glyoxylate and alpha-imino acetates. Versatile reagents for the synthesis of alpha-hydroxycarboxylic acid and alpha-amino acid libraries

Polymer-supported glyoxylate monohydrate (3) and alpha -imino acetates (7) have been readily prepared from chloromethylated resin via two or three ste ps. The ene reactions of 3 with alkenes were successfully performed in the presence of Yb(OTf)(3) (50 mol %) to afford, after cleavage from the polyme r support, the corresponding alpha -hydroxycarboxylic acid esters in good y ields. The reactions of 7 with silyl enolates, Danishefsky's diene, and alk enes also proceeded smoothly in the presence of Sc(OTf)(3) (20 mol %) to gi ve the corresponding cl-amino acid, pyridone, and tetrahydroquinoline deriv atives, respectively, in good yields.