Quorumolides A-C, Three Cembranoids from Euphorbia antiquorum.

Three highly modified cembranoids, quorumolides A-C (1-3), were isolated from Euphorbia antiquorum. Compound 1 is the first example of a cembranoid embedding an α,β-unsaturated-γ-lactone and a tetrahydro-2H-pyran motif within the 14-membered ring. Biosynthetically, it is particularly noteworthy that the stereochemistries of C-2 and C-12 in the pyran ring of 1-3 were opposite to those of marine-derived rare cembranoids.