Abstract
This article reviews studies regarding the total synthesis of phaeosphaerides A and B, nitrogen-containing bicyclic natural products isolated from an endophytic fungus. Numerous synthetic efforts and an X-ray crystal structure analysis of phaeosphaeride A have enabled revision of its originally proposed structure. In addition, a successful protic acid-mediated transformation of phaeosphaeride A to phaeosphaeride B revealed the hypothetical biosynthesis of phaeosphaeride B from phaeosphaeride A. Structure–activity relationship studies of phaeosphaeride derivatives are also discussed.
Highlights
Signal transducer and activator of transcription 3 (STAT3), which belongs to the STAT family of proteins [1], regulates cell proliferation, differentiation, and survival [2]
Unusual activation of STAT3 is frequently found in various types of tumor cells, leading to apoptosis resistance and tumor cell proliferation via enhanced expression of gene encoding proteins such as Bcl-2, Bcl-xL, and cyclin D1 [5,6]
Various STAT3 inhibitors including synthetic small molecules and natural products have been evaluated as prospective anticancer chemotherapeutic agents [7]
Summary
Signal transducer and activator of transcription 3 (STAT3), which belongs to the STAT family of proteins [1], regulates cell proliferation, differentiation, and survival [2]. Once phosphorylated at Tyr705 in the Janus kinase (JAK)/STAT signaling pathway, STAT3 dimerizes, translocates to the nucleus, and binds to a target DNA sequence to induce transcriptional activation [3,4]. STAT3 has gained considerable interest as a potential target for anticancer therapy. The promising biological activity of phaeosphaeride A as well as its simple and unique The promising biological activity of phaeosphaeride A as well as its simple and unique molecular structurebiological has attracted attention from the synthetic community. A as well as its simple and unique molecularpromising structure has attracted much attention from the synthetic community. Studies of STAT3 inhibitory activity should be of significant structure has attracted much attention from theofsynthetic community. STAT3 inhibitory activity shouldstructure–activity be of significant importance for potential anticancer therapy. STAT3 inhibitory importance for potential anticancer therapy
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