a$.,N-$Protected phenylalanine $F$ is formed from alanine $D$ and compound $E$ as shown in Figure $3.$

$($i$)$ Identify the structure of compound $E.$

$($ii$)$ Draw the mechanism for the formation of compound $F$ from compounds $D$ and $E$ suggesting a suitable base for this reaction.

$($iii$)$ Suggest suitable reaction conditions to remove the protecting group from compound $F.$

$($iv$)$ Draw the mechanism for the deprotection of compound $F$ using the conditions you have suggested in part $($iii$)$ above.