Question

Question: Quinapril (trade name Accupril) is used to treat high blood pressure and congestive heart failure. One step in the synthesis of quinapril involves the reaction of the racemic alkyl bromide A with a single enantiomer of the amino ester B. (a) What two products are formed in this reaction? (b) Given the structure of quinapril, which one of these two products is needed to synthesize the drug?

quinapril

Short answer

Answer

a. Two isomers with different R and S configurations at the two stereocenters are formed by this reaction.

The isomer [A] with (S) configuration

The isomer [B] with one R and one S configuration

b. The isomer [A] is needed to synthesize the drug.

Synthesis of quinapril

Step-by-step solution

Synthesis of quinapril

The synthesis of quinapril requires the use of racemic alkyl bromide with a single amino ester in the presence of a tertiary amine. The reaction leads to the formation of two isomers with different R and S configurations.

The isomer in which both the stereocenters have the same (S) configuration is further used in the next step for the synthesis of quinapril.

Synthesis of quinapril

• In the first step, the reaction of racemic A with the single enantiomer of the amino ester takes place in the following manner:

Two products are formed with (S), (S) and (R), (S) configuration

The isomer which is further used in the next step for the synthesis of quinapril is given below:

Isomer [A] with (S) configuration

In the next step, the isomer [A] is used for the synthesis of quinapril, as shown in the following reaction:

Quinapril synthesis