Isolation and biomimetic total synthesis of tomentodiones A–B, terpenoid-conjugated phloroglucinols from the leaves of Rhodomyrtus tomentosa

Abstract

Tomentodiones A (1) and B (2), a pair of C-11′ epimers of caryophyllene-conjugated phloroglucinols with an unprecedented skeleton, were isolated from the leaves of Rhodomyrtus tomentosa. Their structures were elucidated through the application of extensive spectroscopic measurements with the absolute configuration of 1 determined by single-crystal X-ray diffraction analysis and electronic circular dichroism (ECD) calculations. The biogenetic pathways of 1 and 2 were proposed to involve an intermolecular, inverse electron demand Diels–Alder cycloaddition reaction as the key step, and their biomimetic total synthesis was accomplished.