1: MeSCF2P(O)(Oi-Pr)2 With tert.-butyl lithium in tetrahydrofuran; pentane T=-78°C; 2: 4-(chloromethyl)-1,3,2-dioxathiolane-2,2-dioxide in tetrahydrofuran; pentane T=-78°C; 0.25 h; 3: With sulfuric acid; water in tetrahydrofuran; pentane T=-78 - 20°C;