Labdane-type diterpenoids from Croton laevigatus

Abstract

Sixteen new labdane-type diterpenoids (1–9, 11–17) were isolated from the twigs and leaves of Croton laevigatus, along with 15-hydroxylabda-7,13(E)-diene-17,12-olide (10), which is reported here as a natural product for the first time. Their structures were elucidated on the basis of extensive spectroscopic data interpretation, including UV, IR, NMR, and MS, and comparison with literature data. The structures of compounds 7, 8, 10, 14, 15, 16, and 17 were further confirmed by single-crystal X-ray diffraction analysis. The absolute configurations of 10–17 were determined by the CD exciton chirality method and supported by the single-crystal X-ray diffraction analysis of 10, 14, and 15. Crotonlaevins A (1) and B (2) are the reported first labda-type diterpenoids with a dodecahydronaphtho [1,2-c] furan moiety, and compounds 10–17 are the first reported labda-17,12-olide derivatives isolated from nature.