in ethanol Sn-compound reacted with Na2Se2 in EtOH at 0°C;

sodium tetrahydroborate in tetrahydrofuran; ethanol (under Ar); mixt. of Sn-compounds added dropwise to suspn. of NaBH4 in EtOH-THF with stirring at room temp., stirred for 10 min; concd. in vacuo, poured into H2O, extd. with CH2Cl2, extract washed withH2O, dried, concd. in vacuo, chromd. on silica gel with 1:7 CH2Cl2:C6H1 4;