1: 82 percent / (R,R)-diethyl tartrate, titanium tetra iso-propoxide, tert-butyl hydroperoxide / CH2Cl2 / 24 h / -23 °C 2: 100 percent / hydrogen / 5 percent Pd/C / ethanol / 19 h / 20 °C 3: 87 percent / pyridine / 14.5 h / 0 °C 4: 8 percent / lithium aluminum hydride / diethyl ether / 3 h / 21 °C View Scheme

manganese(IV) oxide in dichloromethane T=20°C; Oxidation; 2 h;

With  diisobutylaluminium hydride in  dichloromethane; toluene T=-78 - 0°C; 1.5 h;  Inert atmosphere;   

With  titanium(IV) isopropylate; tert.-butylhydroperoxide; diethyl (2R,3R)-tartrate in  dichloromethane T=-23°C; 24 h;