An organic compound $[\mathrm{A}]\left(\mathrm{C}_{4} \mathrm{H}_{11} \mathrm{~N}\right)$, shows optical activity and gives $\mathrm{N}_{2}$ gas on treatment with $\mathrm{HNO}_{2}$. The compound $[\mathrm{A}]$ reacts with $\mathrm{PhSO}_{2} \mathrm{Cl}$ producing a compound which is soluble in $\mathrm{KOH}$. The structure of $\mathrm{A}$ is :