title: 6α-Acetoxy-gedunin.
abstract: THE TITLE COMPOUND [SYSTEMATIC NAME: (1S,3aS,4aR,4bS,5S,6R,6aR,10aR,10bR,12aS)-5,6-bis-(acet-yloxy)-1-(3-fur-yl)-1,5,6,6a,7,10a,10b,11,12,12a-deca-hydro-4b,7,7,10a,12a-penta-methyl-oxireno[c]phenanthro[1,2-d]pyran-3,8(3aH,4bH)-dione], C(30)H(36)O(9), is a limonoid-type triterpene isolated from Aglaia elaeagnoidea (A. Juss.) Benth. (Meliaceae) from Queensland, northern Australia. It contains the gedunin core of four trans-fused six-membered rings with an oxirane ring annelated to the fourth ring. A terminal 3-furyl unity and two acet-oxy groups in a mutual cis-disposition supplement the mol-ecule. A comparison between the gedunin cores of the title compound, the parent compound gedunin, and three further gedunin derivatives revealed considerable variations in their conformation stemming from the conformational lability of the first screw-boat ring and the third twist-boat ring. A sensitive measure for the third ring is one C-C-C-C torsion angle, which is 14.2 (2)° in the title compound, but varies in other cases from ca 20 to ca -40°. In the crystalline state, 6α-acetoxy-gedunin shows ten comparatively weak C-H⋯O inter-actions, with H⋯O distances in the range of 2.33-2.69 Å.
authors.forename: Margit
authors.initials: M
authors.lastname: Hofer
authors.forename: Harald
authors.initials: H
authors.lastname: Greger
authors.forename: Kurt
authors.initials: K
authors.lastname: Mereiter