$(15$ pts$)($a$)$ Saquinavir is an antiviral agent that acts against HIV$-$protease. Assess the structure in terms of

Lipinski's rules and Veber's parameters $(logP=4\mathrm{.}2$; polar surface area $=167).($b$)$ Suggest five possible

regions in saquinavir that might be susceptible to metabolism and identify the possible metabolite formed.