Chapter 25.4, Problem 28CC

(a)

Interpretation Introduction

Interpretation:

Bond-line structure of aspartame and its three stereoisomers need to be drawn.

Concept introduction:

Bond-line structure is the representation of organic structural formulas in a shorthand manner.  In this case only the bond between carbon and other atoms are shown except hydrogen.  It is understood that all the remaining valency to be filled by hydrogen.  Apart from carbon atoms the other atoms are shown along with hydrogen.  For drawing a peptide sequence in bond-line structure the steps need to be followed are,

• Draw the peptide with correct number of residues
• The side chain associated with the residue has to be identified
• Assign proper configuration for the residues

To draw: bond-line structure of aspartame

(b)

Interpretation Introduction

Interpretation:

Bond-line structure of aspartame and its three stereoisomers need to be drawn.

Concept introduction:

Stereoisomers are the compounds which have the same structural entry but differ in the configuration at the chiral centers.  If a compound has only one stereo center then that compound has one stereoisomer.  If it has two stereocenters then that compound has four stereoisomers.  The number of stereoisomers possible can be found out by a formula,

${\text{Number of stereoisomers = (2)}}^{\text{number of stereocenters}}$

To draw: all the three stereoisomers of aspartame