Convergent Biomimetic Semisynthesis of Disesquiterpenoid Rumphellolide J ; Semisynthesis of Linariophyllenes A–C and Rumphellolide H, Structure Revisions and Proposed Biosynthesis Pathways ; Bridgehead Epoxide Iso-Euphoranin E from β-Caryophyllene Oxide via Sequential Cationic Formation and Scission of [4.3.2]Propellane ; Bioinspired Semisynthesis and Structure Revisions of Chlorinated Norsesquiterpenoids Rumphellatins A‒C.