Crystal and molecular structure of 13-diethanolamino-deacetyllaurenobiolide. Macrocycle conformation in linear germacrolides

ChemInform Abstract: Germacrane‐Type Sesquiterpenes from Curcuma wenyujin.

“…The IR spectrum of 1 indicated the presence of an a,b-unsaturated g-lactone ring (1741 cm À1 ) and a ketone (1715 cm À1 ). The HMBC correlations of Me (13) to C(7), C(11), C(12), C(8), C(5), and C(6) confirmed that an a,b-unsaturated g-lactone ring (d(C) 156.7, 108.3, 130.5, and 173.7) was located at C(7), C(8), C(11), and C(12) with a Me group (d(H) 1.83; d(C) 9.4) attached to C (11). The 13 C-NMR spectrum (recorded in CD 3 OD; Table 1) displayed 15 C-atom resonances comprising three Me, four CH 2 , and two CH groups (thereof one olefinic CH), as well as six quaternary C-atoms (one O-bearing, three olefinic C-atoms, one ketone CO, and one ester CO group).…”

“…These functionalities accounted for four degrees of unsaturation. The ten-membered ring is conformationally flexible [12], while the H-atom signals in the 1 H-NMR of 1 ( Table 2) are not broadened, which indicated the positioning of the ketone CO at C(5) and the OH group on C(8) in 1 favor formation of an OÀH ··· O intramolecular H-bond [13]. The aforementioned spectroscopic features implied that compound 1 might be a germacrane-type sesquiterpene [10].…”