boron trichloride; sodium cyanoborohydride 1.) -78 deg C, 1.5 h, CHCl3; RT, 16 h, CHCl3, 2.) MeOH/H2O(1:1), pH=(6-7) (with 0.1 mol/l hydrochloric acid), RT, 24 h; Yield given. Multistep reaction;