Xanthochrysanthones A−C, Novel Lobster‐Shape Cinnamoyltriketone Dimers with Antiviral Activities from <i>Xanthostemon chrysanthus</i>

Three pairs of enantiomeric cinnamoyltriketone dimers, (+)- and (-)-xanthochrysanthones A-C [(+)- and (-)-1-3)], were recognized and obtained from Xanthostemon chrysanthus by employing the building blocks-based molecular network (BBMN) strategy. Compounds 1-3 featured two new types of lobster-shape carbon skeletons with unprecedented spiro[cyclohexane-1,2'-xanthene] or benzo[7,8]oxocino[4,5-b]chromene tetracyclic ring systems. Their structures with absolute configurations were established by comprehensive spectroscopic analyses, X-ray crystallography, and ECD calculations. Compounds 1-3 represent the first example of phloroglucinol derivatives that are biogenetically constructed by a De Mayo reaction followed by Michael addition. Additionally, compounds 1-3 exhibited significant antiviral activity against respiratory syncytial virus (RSV). Time-of-addition assays indicated that compound 3 specifically acts on the early stages of the virus replication process in RSV.