"Activated Borane": A Porous Borane Cluster Polymer as an Efficient Lewis Acid-Based Catalyst

Borane cluster-based porous covalent networks, named activated borane (ActB), were prepared by cothermolysis of decaborane(14) (nido-B10H14) and selected hydrocarbons (toluene, ActB-Tol; cyclohexane, ActB-cyHx; and n-hexane, ActB-nHx) under anaerobic conditions. These amorphous solid powders exhibit different textural and Lewis acid (LA) properties that vary depending on the nature of the constituent organic linker. For ActB-Tol, its LA strength even approaches that of the commonly used molecular LA, B(C6F5)3. Most notably, ActBs can act as heterogeneous LA catalysts in hydrosilylation/deoxygenation reactions with various carbonyl substrates as well as in the gas-phase dehydration of ethanol. These studies reveal the potential of ActBs in catalytic applications, showing (a) the possibility for tuning catalytic reaction outcomes (selectivity) in hydrosilylation/deoxygenation reactions by changing the material's composition and (b) the very high activity toward ethanol dehydration that exceeds the commonly used γ-Al2O3 by achieving a stable conversion of ∼93% with a selectivity for ethylene production of ∼78% during a 17 h continuous period on stream at 240 °C.

Palladium nanoparticles on a pyridinium supported ionic liquid phase: a recyclable and low-leaching palladium catalyst for aminocarbonylation reactions

SILP catalyst with grafted pyridinium ions was used for either mono- or double carbonylation depending on the reaction conditions. Good recyclability and low palladium loss were observed during the synthesis of pharmaceutically active compounds.

Plasma levels of acylated ghrelin during an oral glucose tolerance test in obese children

OBJECTIVE

Ghrelin is an acylated peptide with octanoyl modification, which is essential for its GH-releasing ability. Coexpression of GH secretagogue receptor (GHS-R) and ghrelin in the pancreas suggests that this peptide is involved in glucose metabolism. The other form of the molecule, the non-acylated ghrelin, has been reported to be devoid of any pituitaric endocrine activities. Previous reports demonstrated that plasma total ghrelin levels decrease after oral glucose administration in obese children, but no data are available about the plasma levels of acylated ghrelin. Therefore, in the present study the plasma levels of acylated ghrelin were measured in obese and control children during oral glucose tolerance test (OGTT).

MATERIALS AND METHODS

Acylated ghrelin response to OGTT was evaluated in 11 obese and 9 age-matched control children. All subjects received 0.75 g/kg (maximum 75 g) glucose solution orally after an overnight fast. Acylated ghrelin, insulin, glucose, and GH were determined at 0, 30, 60 and 120 min, and leptin at 0 min of the OGTT.

RESULTS

Plasma basal levels of acylated ghrelin were significantly lower in the obese children than in the controls (66.3+/-6.7 vs 97.2+/-14.4 pg/ml, p<0.05). The plasma acylated ghrelin concentration decreased significantly at 30 and 60 min in the control group (53.3+/-9.9 and 57.4+/-7.0 pg/ml, p<0.05), but not in the obese group (64.7+/-9.6 and 49.3+/-4.6 pg/ml) as compared to the basal value. In the obese group the acylated ghrelin level was significantly higher at 120 min, than at 0 min (91.6+/-9.8 vs 66.3+/-6.7 pg/ml, p<0.05).

CONCLUSIONS

There was no rapid fall in plasma levels of acylated ghrelin in obese children after OGTT at 30 min, but there was an increase at 120 min, suggesting that the dynamic of the response to OGTT is slower and there is an upregulation of active ghrelin in the second half of OGTT in obese children.