magnesium sulfate in diethyl ether T=20°C; 14 h;

1: With boric acid trimethyl ester in diethyl ether T=-78 - 0°C; 5 h; 2: With hydrogenchloride in diethyl ether 1 h;

sulfuric acid; water in diethyl ether B(OCH3)3 and org. compd. added to Et2O during a period of 1 h at -78°C, mixture stirred at -78°C for 20 min and at 0°C for10 min, hydrolyzed with H2O for 5 min, aq. H2SO4 for 10 min; separaition of ether layre, extn. (Et2O) of aq. layer, drying of combined org. layres over Na2SO4, concg. in vac., dissolving in Et2O, washing with hexane, recrystn. (Et2O-hexane);