Chapter 26, Problem 51IP

(a)

Interpretation Introduction

Interpretation:

Diastereomeric epoxides formed from cholesterol when treated with $\text{MCPBA}$ need to be drawn and the epoxide which will be formed in experimental conditions need to be found out.

Concept introduction:

A three atom ring of cyclic ether is known as epoxide.  An epoxide is formed when an unsaturated (double bond) compound is treated with oxidizing agents such as $\text{MCPBA}$.  Simply to say oxidation of alkene to form cyclic ether is known as epoxidation.  The general structure of epoxide can be shown as given below,

To draw: the diastereomeric species when cholesterol undergoes epoxidation.

(b)

Interpretation Introduction

Interpretation:

Diastereomeric epoxides formed from cholesterol when treated with $\text{MCPBA}$ need to be drawn and the epoxide which will be formed in experimental conditions need to be found out.

Concept introduction:

The epoxidation reaction is influenced by the groups present above and below the ring.  If any substituent is present above the ring the epoxide cannot be formed above the ring due to steric hindrance and vice-versa.

To draw: the one diastereomeric species formed when cholesterol undergoes epoxidation.