1: DIBAL / tetrahydrofuran / 2 h / ice bath 2: 73 percent / tBuOOH, VO(acac)2 / benzene / under standard Sharpless conditions 3: CrO3-pyridine / CH2Cl2 / Ambient temperature 4: silica gel / eluted the column with hexane-ether View Scheme

diisobutylaluminium hydride in tetrahydrofuran 2 h; ice bath; Yield given;