1: (phenylsulfonyl)methane With n-butyllithium in tetrahydrofuran; hexane T=0°C; Inert atmosphere; 2: With diethyl chlorophosphate in tetrahydrofuran; hexane Inert atmosphere; 3: oxetan-3-one in tetrahydrofuran; diethyl ether; hexane T=-78°C; Horner-Wadsworth-Emmons olefination; Inert atmosphere;