[en] MgB₂ related compounds such as the borocarbides LiBC and MgB₂C₂, and the nominal compound of 'BeB₂' were synthesized and existence of superconductivity investigated by low field magnetic susceptibility measurements. Superconductivity was observed not to occur in all of the compounds down to a temperature of 2 K which agrees with recent calculations on the borocarbides. Hole doping of MgB₂C₂ has been predicted to be favorable for superconductivity due to the flat band (in the T-Y direction) similar to one in MgB₂. Attempts to substitutionally hole dope MgB₂C₂ with alkali metals were carried out for the first time, with Li doping demonstrated to appear to be feasible, but in the present samples superconductivity was not observed. (author)