Please look at Problem $15,$ Ch$.8$ in Silverman and Holladay.$$

PLEASE HELP ANSWER ALL OF THE PARTS

a$)$ Predict the structure of the toxic metabolite produced via an enzymatic reaction with the thiazole ring in $12.$

b$)$ Why is this metabolite likely to be toxic?$$

c$)$ What enzyme is likely responsible for the enzymatic transformation?

d$)$ Explain how modifications suggested in the answers in the back of the book would be beneficial.