Radicalised by the light

Consider the following radical equations:

$O_{3} \longrightarrow O_{2} + Z$

$H_{2}O + Z \longrightarrow Y$

$Z + Y \longrightarrow W$

W , Y and Z are radicals. The radical W radical can be thought of as an electron excess protonation of an anion: X

Y and X are dangerous species in biological systems. Y reacts with DNA. This reaction mutates DNA into a carcinogen: (P denotes the unchanged portion of the molecule)

Aware of the dangers these species present, the body produces an enzyme M-S that converts these species into useful products. M is a d-metal and S is the enzyme substrate.

We denote $\alpha = {Cu}^{2+}-S$ and $\beta = {Cu}^{+}-S$ :

$\alpha + X \rightleftharpoons \beta + V$

$2{H}^{+} + \alpha + X \rightleftharpoons U + \beta$

Without this enzyme, these species would accumulate in the cells which leads to autophagy resulting in cell death.

The hydrated isomer of D is used to treat cancer as it allows the radicals to accumulate in cancer cells resulting in their death but just like all medicine, "sola dosis facit venenum" .

Compound D is prepared through the following scheme: We start with the precursor E ,

• We expose it to light to form an equal amount of regio-isomers A and B .

• In the presence of $Br_{2}$ both regio-isomers form C

• C reacts with $Bu_{3}SnH$ and later is later heated with $N_{2}H_{4}$ in a basic medium to form D whose formula is $C_{15}H_{24}$

If the mass of X is $a$ and the number of rings in A is $b$ ,

Calculate the value of $a-b$

BONUS

• Provide an electron pushing mechanism for DNA degradation.

• Identify compounds U - Z .

• Identify compounds A - D .

• Provide an electron pushing mechanism for the transformation of E to A and B and explain why equal amounts are obtained.