Design and Synthesis of Optically Active Esters of γ-Amino-β-oxo Acids as Precursors for the Synthesis of Tetramic Acids Derived from L-Serine, L-Tyrosine, and L-Threonine

Tetramic acids bearing a hydroxyalkyl or hydroxybenzyl group at C‐5 of the heterocyclic ring were successfully prepared. α‐Amino acids appropriately protected and activated were used as acylating agents for the C‐acylation of active methylene compounds. These novel synthesized intermediates, substituted γ‐amino acids, were isolated in excellent yields and enantiomeric purities. Cyclization under basic conditions afforded the desired products in high yields and enantiomeric purity. An array of functionalized tetramic acids bearing a hydrophilic group on the side arm of the heterocyclic nucleus, as well as their intermediate β‐hydroxy‐γ‐amino acids, were synthesized from suitably protected and activated L‐serine, L‐tyrosine, and L‐threonine in two steps with good‐to‐excellent enantiomeric purities (up to 95 % ee) and high yields (up to 92 %).