phosphoric acid in tetrahydrofuran Ru-compd., NaBH4 and (18)crown-6 in THF stirred for 2.5 h at room temp., addn. of H3PO4, stirred for 5 min; excess H3PO4 neutralized with NaHCO3, dried with MgSO4, filtered, removal of solvent in vac., dissolved in CH2Cl2, TLC (hexane/CH2Cl2 7:3);