Serotonin antagonists are a group of drugs majorly used as anti-depressants. They also are used as hypnotics and anxiolytics. Their action is antagonistic to that of the receptors of serotonin, particularly the alpha 1 andregenic receptors.
The strategy of extension is commonly used for optimization of drugs. It usually involves addition of a substituent or functional group to the main compound in order to provide extra sites for binding of the target molecule.
The structure VII contains the lead compound. It is capable of fitting into the binding site, and also has the functional groups that are required for interaction with some of the significant binding sites.
The addition of the methyl group in analogue VIII helps in finding the access hydrophobic regions by the addition of the methyl group. The strategies of extension are utilized to strengthen the binding interactions and receptor antagonist activity. This analogue is an andregenic agent more active as compared to serotonin because of addition of the methyl group.