Aminoalcohols V [1]: A Methodfor the Synthesis of EnantiomericallyPure Ring-Chlorinated Epinephrinesand Norepinephrines

Abstract

The synthesis of enantiomerically pure 5-and 6-chloroepinephrine hydrochloride, resp., as well as 6-chloronorepinephrine hydrochloride is described starting from ring chlorinated O-benzylated dihydroxybenzaldehyde cyanohydrins, which are O-protected using an enantiomerically pure acetal-type protecting group (MBE). After lithium aluminum hydride reduction, followed ± if necessary ± by N-protection and methylation, removal of the chiral auxiliar and deprotection by hydrogenation furnished the target compounds with enantiomeric purities above 96% ee in high chemical yield, if well de®ned reaction conditions during the hydrogenation process were closely observed.