Carbazoles and Tetrahydro carbazoles as Potential Therapeutic Agents- A Review on Its Chemistry, Synthesis and Biological Evaluation

Carbazoles and their partially saturated analogues, tetrahydrocarbazoles, have attracted considerable interest in medicinal chemistry owing to their broad spectrum of pharmacological activities and structural versatility. These heteroaromatic compounds exhibit significant anticancer, antimicrobial, antiviral, anti-inflammatory, and neuroprotective properties. The rigid tricyclic core of carbazoles supports extensive chemical modifications, while tetrahydrocarbazoles provide enhanced molecular flexibility and metabolic stability, making them valuable scaffolds for therapeutic development. This review aims to summarize recent developments in the synthesis, chemical modifications, and biological applications of carbazoles and tetrahydro carbazoles, emphasizing their potential in drug discovery. Relevant literature was systematically analyzed to evaluate synthetic strategies for carbazole derivatives. Classical methods such as Fischer indole synthesis, Borsche-Drechsel method, and oxidative cyclization were reviewed alongside modern catalytic techniques. Structure-Activity Relationship (SAR) studies were also examined to understand the impact of substitution patterns on biological activity. Various synthetic approaches have enabled the preparation of structurally diverse carbazole derivatives with significant biological activities. SAR studies revealed that substitution at specific positions on the carbazole nucleus strongly influences pharmacological potency, selectivity, and therapeutic efficacy. Carbazoles and tetrahydro carbazoles remain promising scaffolds in medicinal chemistry. Continued advancements in synthetic methodologies and SAR-driven optimization may support the development of novel derivatives with improved pharmacological performance and clinical potential.