ABSTRACT
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.
Subject(s)
Aldehydes/chemistry , Carboxylic Acids/chemical synthesis , Heterocyclic Compounds/chemistry , Methane/analogs & derivatives , Carboxylic Acids/chemistry , Catalysis , Methane/chemistry , Molecular Structure , Oxidation-ReductionABSTRACT
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.
Subject(s)
Cholic Acid/chemistry , Chromatography, Gas , Electrochemistry , Electrodes , Oxidation-ReductionABSTRACT
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.
Subject(s)
Amino Acids, Cyclic , Amino Acids/chemistry , Analgesics, Opioid/chemical synthesis , Cyclohexanecarboxylic Acids/chemistry , Cyclohexylamines/chemistry , Oligopeptides/chemical synthesis , Receptors, Opioid/drug effects , Analgesics, Opioid/chemistry , Analgesics, Opioid/pharmacology , Animals , Brain/enzymology , Brain/metabolism , Guinea Pigs , Ileum/drug effects , In Vitro Techniques , Male , Mice , Molecular Conformation , Oligopeptides/chemistry , Oligopeptides/pharmacology , Rats , Rats, Sprague-Dawley , Receptors, Opioid, delta/drug effects , Receptors, Opioid, kappa/drug effects , Receptors, Opioid, mu/drug effects , Spectrophotometry, Ultraviolet , Stereoisomerism , Vas Deferens/drug effectsABSTRACT
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.
