Synthesis of Enantiopure Di( Tert ‐Butyl) (2 S ,4 S )‐4‐Hydroxy‐6‐Oxo‐1,2‐Piperidinedicarboxylate. A Useful Building Block for the Preparation of 4‐Hydroxypipecolate Derivatives

Abstract N ‐alpha‐ tert ‐Butoxycarbonyl‐L‐aspartic acid alpha‐ tert ‐butyl ester 2,2‐Dimethyl‐1,3‐dioxane‐4,6‐dione N ‐(3‐Dimethylaminopropyl)‐ N ′‐ethylcarbodimide hydrochloride 2‐ tert ‐ Butoxycarbonylamino‐4‐(2,2‐dimethyl‐4,6‐dioxo‐[1,3]dioxin‐5‐yl)‐4‐oxo‐butyric acid tert ‐butyl ester Di( tert ‐butyl)(2 S )‐4,6‐dioxo‐1,2‐piperidinedicarboxylate Sodium borohydride Di( tert ‐butyl)(2 S ,4 S )‐4‐hydroxy‐6‐oxo‐1,2‐piperidinedicarboxylate