$\begin{array}{*{20}{c}}
{\,\,\,\,\,\,CHO} \\
{|\,\,\,} \\
{H - C - OH} \\
{|\,\,\,\,} \\
{\,\,\,\,\,\,\,\,\,C{H_2}OH}
\end{array}$
$' A ^{\prime} \stackrel{ HNO _3}{\longrightarrow} X ^{\prime} \stackrel{ NaBH _4}{\longrightarrow} \underset{\text { Chiral compound }}{\text { } B ^{}}$