Discovery and Biomimetic Synthesis of a Polycyclic Polymethylated Phloroglucinol Collection from Rhodomyrtus tomentosa

Inspired by a previously reported biomimetic synthesis study, four new naturally occurring phloroglucinol trimers 1–4with unusual 6/5/5/6/6/6-fused hexacyclic ring systems, along with two known analogues (5and 6) and two known biogenetically related dimers (10and 11), were isolated from Rhodomyrtus tomentosa. Their structures and absolute configurations were unambiguously elucidated by spectroscopic analysis, X-ray diffraction, and electronic circular dichroism calculation. By mimicking two potentially alternative biosynthetic pathways, the first asymmetric syntheses of 1–4and the racemic syntheses of 5and 6were achieved in only five to six steps without the need for protecting groups. Furthermore, phloroglucinol dimers 10and 11exhibited significant in vitro antiviral activity against the respiratory syncytial virus.