Question

Saquinavir (trade name Invirase) is a protease inhibitor, used to treat HIV (human immunodeficiency virus).

1. Locate all stereogenic centers in saquinavir, and label each stereogenic center as R and S.
2. Draw the enantiomer of saquinavir.
3. Draw a diastereomer of saquinavir.
4. Draw a constitutional isomer that contains at least one different functional group.

Short answer

a.

b.

c.

d.

Step-by-step solution

Stereogenic center

The stereogenic center is the carbon atom which is bonded to four different groups. Some large biomolecules may have hundreds of stereocenters.

Enantiomer, diastereomer, and constitutional isomers

The molecules which have one tetrahedral stereogenic center are chiral in nature. They will always have a pair of enantiomers.

The enantiomers are the compounds that are the non-superimposable mirror images of each other. Diastereomers are a kind of stereoisomers that are not mirror images of each other.

Constitutional isomers are the type of isomers that have the same molecular formula but differ from each other in terms of structures.

The different isomers of saquinavir

a. The given structure of the saquinavir molecule has a total of six stereogenic centers, as shown in the structure below:

Representation of stereogenic centers

b. Following is the structure of the enantiomer of saquinavir:

Representation of enantiomers

c. Following is the structure of the diastereomer of saquinavir:

Representation of diastereomers

d. Following is the structure of the constitutional isomer of saquinavir, having a new amine and a new aldehyde group.

Representation of constitutional isomers