Propose a possible retrosynthesis for the following three $(3)$ target molecules $($I$,$ II and III$)$ at the indicated site of disconnection. Only show the approach $($retrons$/$synthons and synthetic equivalents$)$ that is likely to result in a successful reaction. A final synthesis is not required.

$[34$ marks$]$

Consider the compound IV below with eight $(8)$ indicated protecting groups and answer the questions below.

i$.$ Indicate by letter the group$($s$)$ that will likely cleave upon treatment of compound IV with TBAF in THF$.$

ii$.$ Provide the reagents and conditions $($solvents etc.$)$ necessary to protect amine $H$ as a $t-$benzyl carbamate $(R_{2}NCBz).$

iii. Protecting group B is an example of a cyclic dithioketal. Provide an alternative name for this functional group.

$1$

iv$.$ Indicate by letter the group that can be selectively cleaved with $BB{r}_3,THF.$

v$.$ Draw the product of reaction of IV with $AgN{O}_3,$EtOH.

$[3+2+1+1+2$ marks $]$

In each of the following three cases, draw the products $x,Y$ and $Z,$ you would expect to be formed when compound shown below is separately treated with EACH of the following reagents.

$[32$ marks$]$

Give the reagent$($s$),$ conditions etc. needed to selectively protect the substrates below to the desired product.