Asymmetric Alkylations of a Sultam‐Derived Glycine Equivalent: Practical preparation of enantiomerically pure α‐amino acids

Alkylation of the chiral glycine derivative 2 with “activated” organohalides under ultrasound-assisted phasetransfer catalysis or with activated and nonactivated organohalides in anhydrous medium provides (mostly crystalline) alkylation products 3. Acidic hydrolysis of the pure products 3 gives (aminoacyl)sultams 4 which by mild saponification furnish pure α-amino acids 5 in good overall yields from 2, along with recovered auxiliary 1 (Scheme 1). Pure ω-protected α,ω-diamino acids and α-amino-ω-(hydroxyamino)acids 12–16 are readily accessible from (ω-haloacyl)sultams 3via reaction with N-nucleophiles followed by acidic and basic hydrolyses (Scheme 2). A reliable determination of the enantiomeric purity of α-amino acids using HPLC analysis of their N-(3,5-dinitrobenzoyl)prolyl derivatives 17 is presented.