Polish J. Chem. 80 (2006) 667-671.pdf (original) (raw)
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Polish J. Chem. 80 (2006) 667-
Spirostane sapogenins have served for a long time as starting materials for the synthesis of different steroidal drugs . Recently, the sapogenins have been used in the synthesis of brassinosteroids [2] and cephalostatins . All synthetic procedures rely on the degradation or modification of the spiroketal moiet. The chemistry of spirostanes has been intensively studied during the mid part of the last century. However, the discovery of new natural products of interesting biological profile (such as cephalostatins) has stimulated further progress in the field.
On reactions of spirostane sapogenins with benzeneseleninic anhydride
Tetrahedron, 2010
a b s t r a c t Direct dehydrogenation of spirostane sapogenins with benzeneseleninic anhydride/iodoxybenzene afforded the D 22 derivatives in low yields. The reactions catalyzed by BF 3 /Et 2 O produced the 23-oxo-sapogenins in addition to their 22-oxo-23-spiro-isomers. The reactions of sapogenins with benzeneseleninic anhydride carried out in the presence of TiCl 4 afforded products chlorinated at C23.
Tetrahedron Letters, 2007
The reaction of steroid sapogenins of both the 25R and 25S series with diacetoxyiodobenzene and BF 3 AEEt 2 O in formic acid produced a mixture of an equatorial 23-formyloxysapogenin, a 16b,23:23,26-diepoxy-22-one and a bisnorcholanic lactone. The outcome of this reaction, that drastically differs from the same reaction in acetic acid, opens up new possibilities for the transformation of the side chain of steroid sapogenins.
Regio- and stereoselective cleavage of steroidal 22-oxo-23-spiroketals catalyzed by BF3·Et2O
Steroids, 2015
The regioselective opening of the F ring of 22-oxo-23-spiroketals using BF 3 •OEt 2 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 C 23-C 24 double bond in the reaction product 20.
Synthesis and radical scavenger properties of novel spirochromenes derived from steroid sapogenins
Tandem aldol condensation between steroid sapogenins and hydroxylated benzaldehydes afforded steroidal spirochromenes. Compounds that bear a phenolic hydroxyl group at position C-6 0 , obtained by a reaction with 2,5-dihydroxybenzaldehyde, showed approximately 80% of maximal radical scavenging activity in the 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) assay at 288 nM. In contrast, the starting steroid sapogenins and the spirochromenes without a phenolic group in the side chain proved to be inactive.