Chapter 27.1, Problem 1P

Interpretation Introduction

Interpretation: The other three stereoisomers of l-isoleucine is to be drawn and the stereogenic centers are to be labeled as $R$ or $S$.

Concept introduction: The stereogenic centers with $R,S$ configuration are assigned according to Cahn-Ingold-Prelog rules. According to these rules, the substituents attached to stereogenic centers are given priority. On moving from higher priority to lower priority substituent in clockwise direction, the compound is assigned with $R$ configuration. On moving from higher priority to lower priority substituent in anticlockwise direction, the compound is assigned with $S$ configuration.