The Doctoral Thesis focuses on the development of novel phosphoruscontaining carbonic anhydrase inhibitors, which show potential as anticancer drug candidates. In this study, a synthetic route to previously unreported benzoxaphosphepine derivatives was established using ring-closing metathesis. As a result, a series of selective carbonic anhydrase inhibitors possessing nanomolar activity in enzymatic assays was obtained. Information on the structure–activity relationships of the synthesised compounds, in vitro cytotoxicity data, and aqueous solubility is presented. The Thesis has been prepared as a collection of thematically unified scientific publications.