RESUMO
The stereoselective cyclization of a C-16 acetylated 22,26-dioxocholestene derivative to give the spirostane E and F rings, under alkaline conditions, yields exclusively the (26R)-26-hydroxydiosgenin. Both experimental and computational data support the formation of a single diastereoisomer. The effect of diosgenin and (26R)-26-hydroxydiosgenin on rat ovary is also investigated.
Assuntos
Diosgenina/análogos & derivados , Diosgenina/farmacologia , Ovário/efeitos dos fármacos , Animais , Ciclização , Diosgenina/síntese química , Feminino , Modelos Moleculares , Ovário/fisiologia , Ratos , EstereoisomerismoRESUMO
Herein, we report for the first time a "trans-hydroboration-oxidation product" isolated and characterized under traditional hydroboration-oxidation conditions using cholesterol and diosgenin as substrates. These substrates are excellent starting materials because of the rigidity and different structural environments around the double bond. Further investigations based on experimental evidence, in conjunction with theoretical studies, indicate that the formation of this trans-species occurs via a retro-hydroboration of the major product to generate the corresponding Δ6-structure and the subsequent hydroboration by the ß-face. Besides, the corresponding Markovnikov type products have been isolated in synthetically useful yields. The behavior of the reaction under a range of temperatures is also investigated.
RESUMO
26-Hydroxycholestan-22-one derivatives with oxygenated functions in the rings A and/or B were successfully synthesized from diosgenin. After the modifications of rings A and B, the spiroketal side chain was selectively opened through a Lewis acid mediated acetolysis to afford the cholestane derivatives. These compounds incorporate pharmacophores, which mimic the activity of natural phytohormones and show high growth promoting activity in Mexican rice cultivars using the rice lamina inclination test.
Assuntos
Materiais Biomiméticos/química , Materiais Biomiméticos/farmacologia , Colestanóis/química , Reguladores de Crescimento de Plantas/química , Reguladores de Crescimento de Plantas/farmacologia , Materiais Biomiméticos/síntese química , Relação Dose-Resposta a Droga , Oryza/efeitos dos fármacos , Oryza/crescimento & desenvolvimento , Reguladores de Crescimento de Plantas/síntese químicaRESUMO
The regioselective opening of the ring E in spirostan sapogenins provides new dihydropyran derivatives. This novel side chain is obtained after a Lewis acid mediated acetolysis followed by an alkaline workup. The reaction mechanism is analyzed via density functional theory computations, and both experimental and computational data support the formation of an oxacarbenium intermediate. The behavior of the title skeletons under acidic conditions is also investigated.
Assuntos
Piranos/química , Espirostanos/química , Ácidos de Lewis/química , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Estereoisomerismo , Esteroides/químicaRESUMO
The spirostanic steroidal side-chain of diosgenin and hecogenin was modified to produce 22-oxocholestane derivatives. This type of side-chain was obtained in good yields through a straightforward four-step pathway. These compounds show potent brassinosteroid-like growth promoting activity evaluated via the rice lamina joint inclination bioassay. This is the first report of steroidal skeletons bearing the 22-oxocholestane side-chain and preserving the basic structure (A-D rings) from their corresponding parent compounds acting as plant growth promoters.