RESUMEN
N-Heterocyclic carbene catalysis for the aerobic oxidation and esterification of aromatic aldehydes was monitored by ESI-MS (MS/MS) and the key intermediates were intercepted and characterized using the charge-tag strategy.
Asunto(s)
Aldehídos/química , Ácidos Carboxílicos/síntesis química , Compuestos Heterocíclicos/química , Metano/análogos & derivados , Ácidos Carboxílicos/química , Catálisis , Metano/química , Estructura Molecular , Oxidación-ReducciónRESUMEN
Regioselectivity in the anodic electrochemical oxidation of cholic acid with different anodes is described. The oxidation with PbO(2) anode affords the dehydrocholic acid in quantitative yield after 22 h. 3alpha,12alpha-Dihydroxy-7-oxo-5beta-cholan-24-oic acid (59%) and 3alpha-hydroxy-7,12-dioxo-5beta-cholan-24-oic acid (51%) are obtained stopping the reaction at lower time. The rate of the OH-oxidation is C7 > C12 > C3. The electro-oxidation with platinum foil anode gives selectively the 7-ketocholic acid in 40% yield. On the other hand, the graphite plate anode, varying the reaction conditions, produces selectively the dehydrocholic acid in quantitative yield or the 3alpha,12alpha-dihydroxy-7-oxo-5beta-cholan-24-oic acid (96%) while the 3alpha,7alpha-dihydroxy-12-oxo-5beta-cholan-24-oic acid (34%) is obtained together with the other oxo acids.
Asunto(s)
Ácido Cólico/química , Cromatografía de Gases , Electroquímica , Electrodos , Oxidación-ReducciónRESUMEN
The solid phase synthesis, based on the Fmoc chemical protocol, was used to prepare ten deltorphin C (Del-C; H-Tyr-D-Ala-Phe-Asp-Val-Val-Gly-NH2) analogues containing cis- and trans- 2 or 3- or 4- aminocyclohexanecarboxylic acid (ACCA) residues at position 2. ACCA-peptides showed high resistance to degradation by plasma or brain enzymes, negligible affinity for the kappa-binding site and modest delta- and/or mu-receptor affinities. Both [cis-3-ACCA2]Del-C analogues and one trans isomer are the only deltorphin analogues of this series exhibiting an appreciable delta-affinity and selectivity. These data suggest that the presence of a conformationally constrained ACCA residue in position 2 of the "message" sequence of deltorphin C is slightly tolerated.
Asunto(s)
Aminoácidos Cíclicos , Aminoácidos/química , Analgésicos Opioides/síntesis química , Ácidos Ciclohexanocarboxílicos/química , Ciclohexilaminas/química , Oligopéptidos/síntesis química , Receptores Opioides/efectos de los fármacos , Analgésicos Opioides/química , Analgésicos Opioides/farmacología , Animales , Encéfalo/enzimología , Encéfalo/metabolismo , Cobayas , Íleon/efectos de los fármacos , Técnicas In Vitro , Masculino , Ratones , Conformación Molecular , Oligopéptidos/química , Oligopéptidos/farmacología , Ratas , Ratas Sprague-Dawley , Receptores Opioides delta/efectos de los fármacos , Receptores Opioides kappa/efectos de los fármacos , Receptores Opioides mu/efectos de los fármacos , Espectrofotometría Ultravioleta , Estereoisomerismo , Conducto Deferente/efectos de los fármacosRESUMEN
7 alpha-, 12 alpha-, 12 beta-Hydroxy and 7 alpha,12 alpha- and 7 alpha,12 beta-dihydroxy-3-ketocholanoic acids were prepared in satisfactory yields protecting the 3-keto group as dimethyl ketal and subsequent reduction with sodium borohydride of the corresponding 7- and 12-oxo functionalities. The same procedure gave also 3,12-diketo-7 alpha-hydroxy-cholanoic acid.