\definesubmol{acetyl}{(=[::60]O)-[::-60]H_3C}
\definesubmol{benzoate}{*6(-=-=-(-(=[::60]O)-[::-60]OH)=)}%

\chemfig{
    {\color{red}O}            % the oxygen in the middle
         (-[:210]!{acetyl})   % treat one submol as a branch,
    -[:-30]!{benzoate}        % the other one as the main chain
}