Cellulose, upon acetylation with excess acetic anhydride/ ${\mathrm{H}}_2{\mathrm{SO}}_4$ (catalytic), gives cellulose triacetate, whose structure is

The correct structure of product $\text{'}\mathrm{P}\text{'}$ in the following reaction is:

$\mathrm{Asn}+\mathrm{Ser}+{\underset{\left(\mathrm{Excess}\right)}{\left({\mathrm{CH}}_3\mathrm{CO}\right)}}_2\mathrm{O}\stackrel{{\mathrm{NEt}}_3}{⟶}\mathrm{P}$

${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6\underset{373\mathrm{K}}{\overset{\mathrm{HI}/\mathrm{Red} \mathrm{P}}{\to }}\mathrm{A}+\mathrm{B}$

The products $\mathrm{A}$ and $\mathrm{B}$ respectively are

Mutarotation is the change of specific rotation of aqueous solution of:

$\left(\mathrm{a}\right)$ $\mathrm{\beta }$- glucose from $+19.2°$ to $+52.5°$.

$\left(\mathrm{b}\right)$ $\mathrm{\alpha }$- glucose from $+111°$ to $+52.5^{°}$.

$\left(\mathrm{c}\right)$ a sucrose from dextrorotatory to laevorotatory.

${\mathrm{CH}}_2\mathrm{OH}(\mathrm{CHOH}{)}_4\mathrm{CHO}+\mathrm{HCN}\to \mathrm{X}$

Identify the compound $\mathrm{X}$ in the above reaction?