Production of glucose and bioactive aglycone by chemical and enzymatic hydrolysis of purified oleuropein fromOlea Europea

Pure-grade oleuropein, a bitter, hypotensive, phenolic glucoside, was obtained from organic extracts of olive plant leaves by two Chromatographic steps. The purified compound was characterized by spectroscopic NMR and FAB-MS methods. The glucoside underwent chemical and enzymatic hydrolysis. Aglycone was characterized by spectroscopic methods (¹H-NMR and FAB-MS). Glucose was measured by enzymatic methods. The enzymatic hydrolysis of oleuropein was carried out by a soluble β-glucosidase. The reaction was characterized in terms of kinetic parameters, optimal pH value, activation energy, inhibition constant by glucose, and thermal stability. Preliminary experiments were also performed in a continuousflow ultrafiltration membrane reactor. The cut-off of the membrane was lower than the molecular-weight of the enzyme, thus determining β-glucosidase confinement within the reactor. Under these conditions, β-glucosidase had a good long-term stability. This is an encouraging result in view of possible industrial applications.     

The structure of tetronolide,the aglycone of antitumor antibiotic tetrocarcin

X-ray analysis has determined the structure of tetronolide, which has a unique spiro γ-lactone group.     

The biotransformation of oleuropein in rats

A highly sensitive and specific LC‐MS/MS method was developed to investigate the in vivo bio‐transformation of oleuropein in rat. Rat feces and urine samples collected after oral administration were determined by liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in the negative‐ion mode. The assay procedure involves a simple liquid–liquid extraction of parent oleuropein and the metabolite from rat feces and urine with ethyl acetate. Chromatographic separation was operated with 0.1% formic acid aqueous and methanol in gradient program at a flow rate of 0.50 mL/min on an RP‐C₁₈ column with a total run time of 31 min. This method was successfully applied to simultaneous determination of oleuropein and its metabolites in rat feces and urine. De‐glucosylation, hydrolysis, oxygenation and methylation were found to comprise the major metabolic pathway of oleuropein in rat gastrointestinal tract and three metabolites were absorbed into the blood circulatory system within 24 h after oral administration. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis of the glivocarcin-M aglycone

The synthesis of the agylcone of the antibiotic Gilvocardin-M by a sequential Meerwein Diels-Alder route is reported. The D-ring of the agylcone is attached by a halogen atom directed Meerwein arylation reaction and the A-ring is attached by a halogen atom directed Diels-Alder reaction. In the key step the directing chlorine atom is removed by a new thiophenylation reduction sequence.     

Structure of the cardiac aglycone syriogenin

Summary The results of a study of the mass spectra of syriogenin and its D-analog confirm that this cardiac aglycone has the structure of 3,12,14-trihydroxy-5,14-card-20(22)-enolide.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 615–617, September–October, 1974.     

Synthesis of elaiolide and halichoblelide aglycone

A synthesis of two structurally related macrodiolides representing the aglycone of natural products elaiophylin and halichoblelide is described. The key transformation for both is a Ti(II)-mediated (silyloxy)enyne cyclization, generating a new methyl stereocenter and providing a diene that can be selectively cross metathesized with crotonic acid.     

Evaluation and comparison of a methylated teicoplanin aglycone to teicoplanin aglycone and natural teicoplanin chiral stationary phases

HPLC enantiomeric separations of a wide variety of racemic analytes was evaluated using chiral stationary phases (CSPs) based on the macrocyclic glycopeptides teicoplanin (T), teicoplanin aglycone (TAG), and methylated teicoplanin aglycone (Me-TAG) in two different mobile phase modes, i.e., the RP mode and the polar organic (PO) mode. Comparison of the enantiomeric separations using Chirobiotic T, Chirobiotic TAG, and the methylated form of TAG were conducted in order to gain a better understanding of the roles of the polar functional groups on the CSP. Substantial effects due to the cleavage of saccharides and/or methylation on chiral separations were observed in both separation modes. Improved separation efficiencies for many acidic analytes were obtained by methylating the H-bonding groups of TAG. These groups were believed to be a contributing factor to band broadening on TAG due to their negative effect on mass transfer between the stationary phase and mobile phase. Ionic/dipolar interactions between the carboxylate group of the analytes and the amine groups on T, TAG, or Me-TAG are important for chiral discrimination. Therefore, analytes possessing a carboxyl group are good candidates for successful separations on these CSPs. Hydrophobic interactions are important for enantiomeric separations in the RP mode where the H-bonding interactions between analytes and the chiral selectors are relatively weak. Me-TAG offers higher hydrophobicity, which can accentuate the interactions of analytes with hydrophobic moieties, but these interactions are not necessarily stereoselective. In the PO mobile phase, electrostatic/dipolar interactions between polar functional groups are the dominating interactions in chiral recognition. Another important factor is steric fit, which could be changed with every modification of the T structure. Therefore, substantial changes of enantioseparations were obtained within this studied group of CSPs. The PO mode was shown to be the most powerful mobile phase mode for enantiomeric separations on T-based stationary phases, mainly due to the improved efficiency. Methylation of the TAG proved to be a very useful tool for investigating the chiral recognition mechanism for this group of chiral selectors.     

The isolation and structure determination of the fern glycoside osmundalin and the synthesis of its aglycone osmundalactone

From the Japanese foodstuff Akaboshi zenmai, consisting of dried leaves of Osmunda japonica Thunberg and from the Vermont royal fern Osmunda regalis var. spectabilis (Wilid.) Gray a new hydroxypentenolide glucoside, osmundalin (1), was isolated in addition to β-sitosterol and methyl and ethyl palmitate. The structure and absolute stereochemistry of osmundalin were established by spectroscopic and degradation methods and its aglycone, osmundalactone, was synthesized.     

亮点介绍

手性双氮氧化物-La(OTf)3络合物高对映选择性催化硝基烷烃对硝基烯的Michael加成反应研究Angew.Chem.Int.Ed.2008,47,7079～7081手性1,3-二硝基化学物的合成已引起化学家极大的兴趣,主要因为它衍生形成的1,3-二胺是合成药物的重要中间体,但是合成该化合物的不对称催化反应在近几年才兴起.四川大学化学学院冯小明等基于他们课题组的手性氮