Enantioselective Synthesis of Both Enantiomers of a Isoproterenol Analogue and of Di-O-pivaloylepinephrine

An asymmetric synthesis of the analogue 4a of isoproterenol and of di-o-pyvaloylepinephrine 3 which provides both enantiomers in optically pure state is reported. The key step of the method is the highly diastereo-selective reduction (using DIBAL or DIBAL/ZnCl₂) of a β-ketosulfoxide 7 which leads, as desired, to the (S)- or the (R)-configuration at C(1) (Schemes 4 and 5).