A new synthetic strategy to the ABCD ring system of the anticancer agent fredericamycin A (NSC-305263) was realized by the Diels–Alder reaction and olefin metathesis as key steps. The tactics developed here for the construction of the ABCD ring system also involve double Claisen rearrangement followed by a retro-Diels–Alder reaction and ring-closing metathesis. The metathesis approach performs a key role in the construction of A and D rings of the ABCD core unit. More importantly, ABCD fragment synthesis was accomplished without the involvement of protecting groups.

The preparation of a variety of structurally interesting oxygenated cage compounds involving atom-economic processes such as Claisen rearrangement, Diels–Alder reaction, [2+2] photocycloaddition, and ring-closing metathesis (RCM) as key steps is reported. For the first time, oxepane ring system is introduced in cage framework using olefin metathesis as a key step. These cage systems assembled here are difficult to prepare by traditional methods. The synthetic sequence described here opens up new routes to higher order polycycles containing heteroatoms without the involvement of protecting groups. Transannular cyclization observed during Grignard addition and the RCM protocol used here may be applicable to generate unknown oxygenated cage systems.

Benzothiazole derivatives have emerged as being highly significant in drug discovery due to their versatile biological activities and structural adaptability. Incorporating nitrogen and sulfur, this fused heterocyclic scaffold exhibits wide-ranging pharmacological properties, including anticancer, antimicrobial, anti-inflammatory, antidiabetic, neuroprotective, and diagnostic applications. A diverse set of clinically approved and investigational compounds, such as flutemetamol for Alzheimer’s diagnosis, riluzole for ALS, and quizartinib for AML, illustrates the scaffold’s therapeutic potential in varied applications. These agents act via mechanisms such as enzyme inhibition, receptor modulation, and amyloid imaging, demonstrating the scaffold’s high binding affinity and target specificity. Advances in synthetic strategies and our understanding of structure–activity relationships (SARs) continue to drive the development of novel benzothiazole-based therapeutics with improved potency, selectivity, and safety profiles. We also emphasize recent in vitro and in vivo studies, including drug candidates in clinical trials, to provide a comprehensive perspective on the therapeutic potential of benzothiazole-based compounds in modern drug discovery. This review brings together recent progress to help guide the development of new benzothiazole-based compounds for future therapeutic applications.