in tetrahydrofuran; diethyl ether in vac. or under N2 or Ar, addn. of xylylmagnesium bromide in Et2O to a stirred soln. of OsO4 in THF at -78°C, allowed to warm to room temp., 1 h at room temp.; removal of solvent, addn. of hexane, stirred overnight, filtered, concd., cooled to -20°C; elem. anal.;