1: methanol; (4S,2Z)-4-methyl-5-trityloxypent-2-ene With toluene-4-sulfonic acid T=20°C; 4 h; 2: (2S,3Z)-2-methylpent-3-ene-1-ol With oxalyl dichloride; dimethyl sulfoxide in dichloromethane T=-78°C; Swern oxidation; 0.583333 h; 3: With triethylamine in dichloromethane T=-78 - 0°C; 1.16667 h;