Multi-step reaction with 5 steps 1: collidinium tosylate2: triisobutylaluminium, / aq. NaOH3: ZnEt2 / 1,2-dimethoxy-ethane; hexane / 1.) 0 deg C, 4 h, 2.) 20 deg C, 16 h, d.e.= 95.2percent, var. solv. and temp; var. reag.: Zn, Cu(OAc)2, var. solv. and temp.4: 67 percent / PCC5: K2CO3 / methanol