| Abstract
| - From the aerial parts of Jaborosa runcinata six newwithanolides were isolated and namedjaborosalactones 1−6 (1−6). All containa side chain with a carbon−carbon bond between C-12of the intact steroid nucleus and C-23 and a spiranoid γ-lactone atthe latter position. Theadditional ring thus formed has a 17(20)-ene-22-keto system.Jaborosalactones 4−6 (4−6)alsocontain a hydroxyl group at C-21. From the aerial parts ofJaborosa araucana were isolatedthe known withanolides trechonolide A (8), its5α,6β-dihydroxy analogue jaborosotetrol(9),and the spiranoid withanolide jaborosalactone 2 (2), alsoisolated from J. runcinata. Thestereochemistry of the spiranoid center at C-23 was determined as23R based on NOESY NMRspectra and molecular modeling using the AM1 semiempiricalmethod.
|
