Regioselective cleavage of 22-oxo-23-spiroketals. Novel cholestanic frameworks with pyranone and cyclopentenone E rings on the side chain

Synthesis and crystal structures of D-annulated pentacyclic steroids: looking within and beyond AR signalling in prostate cancer

Carbocyclic steroids D-annulated at 16α and 17α positions with a 5-membered ring E are easily accessible via the interrupted Nazarov cyclization. Three steroid series have been structurally studied: chlorine-containing D-annulated...

TiCl4 catalyzed cleavage of (25R)-22-oxo-23-spiroketals. Synthesis of sapogenins with furostanol and pyranone E rings on the side chain

The regioselective opening of the F ring of 22-oxo-23-spiroketals 7a-d using TiCl₄ in acetic anhydride yielded the novel furostanols 11a-d along with cholestanic derivatives 8a-d with pyranone E ring. The structures of the new derivatives thus obtained were established using one- (DEPT) and two-dimensional ¹H, ¹³C NMR experiments (COSY, HSQC, HMBC, NOESY). The 22α-hydroxyl orientation in compounds 11a-d was proposed by comparison of the ¹³C chemical shifts with those of other aglycone members of this family, and confirmed by combined NOESY and X-ray diffraction analysis of compound 11a.

Regio- and stereoselective cleavage of steroidal 22-oxo-23-spiroketals catalyzed by BF3·Et2O

The regioselective opening of the F ring of 22-oxo-23-spiroketals using BF3·OEt2 in acetic anhydride yielded novel cholestanic frameworks with pyranone E ring 20-23. The structures of the new derivatives of botogenin, diosgenin, hecogenin and tigogenin thus obtained were established using one and two dimensional (1)H, (13)C experiments (DEPT, COSY, HETCOR, HMBC). The X-ray diffraction analysis unequivocally confirmed the R configuration at C-23 in the starting 22-oxo-23-spiroketal 18 and the Z configuration of the C23-C24 double bond in the reaction product 20.

Steroidal saponins from dragon's blood of Dracaena cambodiana

Six new steroidal saponins, cambodianosides A-F (1-6), together with seven known ones, were isolated from the dragon's blood of Dracaena cambodiana. The structures of 1-6 were elucidated on the basis of detailed spectroscopic analysis, including 1D and 2D NMR techniques and chemical methods. The cytotoxicities of all the isolated compounds were evaluated in vitro against three human cancer cell lines, and compounds 7, 8, and 11 showed significant inhibitory activities.