Xanthochrysanthones A−C, Novel Lobster‐shape Cinnamoyltriketone Dimers with Antiviral Activities from Xanthostemon chrysanthus

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.