Identify A–E in the following reaction sequence.

Reaction means the atoms/molecules of two/more compounds are rearranged and reacted with each other to form a new compound. Areaction can be carried out either forward or backward.

DIBAL-H is used as a mild reaction for preparation of $-\mathrm{CHO}$. $-{\mathrm{Ph}}_3={\mathrm{CHCo}}_2\mathrm{Et}$ is used as a Wittig reagent for conversion of carbonyl to an alkene. $-{\mathrm{H}}_2$, $\mathrm{Pd}-\mathrm{C}$is used for the hydrogenation of alkene. $-\mathrm{KOH},{\mathrm{H}}_2\mathrm{O}$ is used for base hydrolysis of the ester.

-BOC_p protected amine is used for the peptide bond.

Cyanide is treated with DIBAL-H to form aldehyde. Then on reaction with $-{\mathrm{Ph}}_3\mathrm{P}={\mathrm{CHCo}}_2\mathrm{Et}$, it forms an alkene compound.

Alkene ester is then treated with ${\mathrm{H}}_2,\mathrm{PdC}$. Hydrogenation takes place and forms alkane, which forms a hydrolysis acidic compound on further reaction with potassium hydroxide. Finally, the acidic compound is treated with $-\mathrm{BOC}$form amine.

Formation of amine