RESUMO
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.
Assuntos
Furanos/química , Glicosídeos/química , Sapogeninas/síntese química , Compostos de Espiro/química , Esteróis/química , Titânio/química , Catálise , Modelos Moleculares , Conformação Molecular , Sapogeninas/químicaRESUMO
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.
Assuntos
Boranos/química , Éter/química , Furanos/química , Compostos de Espiro/química , Catálise , Cristalografia por Raios X , Conformação Molecular , EstereoisomerismoRESUMO
The regioselective opening of the F ring of 22-oxo-23-spiroketals using a saturated solution of HCl in acetic anhydride yielded novel cholestanic frameworks with pyranone or cyclopentenone E rings. The structures of the new derivatives of sarsasapogenin, diosgenin and hecogenin thus obtained were established using one and two dimensional (1)H, (13)C experiments (DEPT, COSY, HETCOR, HMBC, ROESY, and NOESY). The X-ray analysis for compound 11b confirmed the 23R configuration for the new stereogenic center.
Assuntos
Colestanos/química , Ciclopentanos/química , Furanos/química , Pironas/química , Compostos de Espiro/química , Anidridos Acéticos/química , Cristalografia por Raios X , Diosgenina/química , Ácido Clorídrico/química , Espectroscopia de Ressonância Magnética/métodos , Modelos Químicos , Estrutura Molecular , Sapogeninas/química , Espirostanos/química , EstereoisomerismoRESUMO
During reactions of 23-oxosapogenins and the corresponding isomeric 22-oxo-23-spiroketals with MCPBA in the presence of BF(3)·Et(2)O, equilibration occurs between the ketones. The Baeyer-Villiger type oxidation is followed by fragmentation to the dinorcholanic lactones and 3-methylbutyrolactone. The mechanistic aspects of these reactions in the 25R and 25S series are discussed.