larized light?

$27.($Chemical Connections $14$A$)$ When a successful drug is discovered, there often follows an effort to synthesize compounds closely related in structure to the original, in hopes of discovering new drugs that are even more effective. Following are structural formulas for capto. pril and three related angiotensin converting enzyme $($ACE$)$ inhibitors, which are used to treat hypertension. Which of these three are chiral, and how many stereoisomers are possible for each? Compare these three structures with that of captopril and determine the similarities in structure among the four drugs.