Synthesis of homochiral l-(S)-tert-leucine via a lipase catalysed dynamic resolution process

Abstract Treatment of (±)-2-phenyl-4- tert -butyloxazolin-5(4 H )-one 8 with Lipozyme® ( Mucor miehei ) in toluene containing n -butanol and a catalytic amount of triethylamine resulted in a 94% yield of (S)- N -benzoyl tert -leucine butyl ester 9 (99.5% e.e.). Subsequent two step hydrolysis (Alcalase® followed by 6N HCl, reflux) yielded homochiral l -(S) -tert- leucine 1 .