Stereoselective dihydroxylation reactions of (gamma)-amino-(alpha),(beta)-unsaturated esters via their aryl ketimine derivatives

OsO4-catalysed dihydroxylation reactions of the aryl ketimine derivatives of (E)-(gamma)-amino-(alpha),(beta)unsaturated esters gave anti selectivity ranging from 6.7 :1 to 19 :1, whereas the opposite syn selectivity was consistently observed with those of (Z)-(gamma)-amino-(alpha),(beta)-unsaturated esters (5.4 :1 to >100 :1).