Chapter 30, Problem 30.27P

Interpretation Introduction

(a)

Interpretation: The stereogenic center at $\text{C15}$ is to be labeled as $R$ or $S$.

Concept introduction: The stereochemistry of the compound is determined by prioritizing the groups attached to its stereogenic center. The groups are prioritized on the basis of atomic number of their atoms. The group that contain atom with higher atomic number is given higher priority. Complete the circle in decreasing order of priority from $1\to 2\to 3$. The configuration of the compound is R and S when circle rotates in clockwise and anticlockwise direction.

Interpretation Introduction

(b)

Interpretation: The two isomeric products formed on reaction of A with $\text{Zn}{\left({\text{BH}}_{\text{4}}\right)}_{\text{2}}$ is to be drawn.

Concept introduction: Zincborohydride is a metal hydride reagent. It is a mild reducing agent which reduces ketones to alcohol. Diastereomers of a compound have at least one stereogenic centre with same configuration and at least one with opposite configuration.

Interpretation Introduction

(c)

Interpretation: The reagent used to convert the A to the single stereoisomer X is to be predicted.

Concept introduction: The chiral oxazaborolidine catalysts are enantiomeric selective reducing reagent. The carbonyl group of ketones are reduced to form one stereoisomer in the enantiomeric excess.