documentclass[12pt,border=1mm,preview]{standalone}

newcommandmcbf[2]{multicolumn{1}{#1}{textbf{#2}}}
    begin{document}
begin{tabular}{lr}
    hline
mcbf{|c|}{AAA}  &   mcbf{c|}{BBB}   \ hline
end{tabular}
    end{document}

documentclass[12pt,border=1mm,preview]{standalone}

newcommandxmcbf[2][c|]{multicolumn{1}{#1}{textbf{#2}}}

    begin{document}
begin{tabular}{lr}
xmcbf[|c|]{AAA} &   mcbf{BBB}  \ hline
C                &   D           \ hline
end{tabular}
    end{document}

multispan ->omit
                  @multispan