Enantiomerically enriched preparation of enolizable β-keto amides. Diastereoselective α-acylation and subsequent aminolysis of 2-acyl-3-phenyl-l-menthopyrazoles
After deprotonation with LDA, 2-acyl-3-phenyl-l-menthopyrazoles (13) were diastereomerically α-acylated to give N-(3-phenyl-l-menthopyrazolyl) β-ketoamides (14–19). The subsequentamides were converted into the corresponding N-alkyl amides (21–24) retaining their enantiomericenrichment on the α-position. These are the first examples of enolizableβ-keto acid derivatives having only one chiral center