Determination of growth hormone secretagogue pralmorelin (GHRP‐2) and its metabolite in human urine by liquid chromatography/electrospray ionization tandem mass spectrometry

GHRP‐2 (pralmorelin, D‐Ala‐D‐(β‐naphthyl)‐Ala‐Ala‐Trp‐D‐Phe‐Lys‐NH₂), which belongs to a class of growth hormone secretagogue (GHS), is intravenously used to diagnose growth hormone (GH) deficiency. Because it may be misused in expectation of a growth‐promoting effect by athletes, the illicit use of GHS by athletes has been prohibited by the World Anti‐Doping Agency (WADA). Therefore, the mass spectrometric identification of urinary GHRP‐2 and its metabolite D‐Ala‐D‐(β‐naphthyl)‐Ala‐Ala‐OH (AA‐3) was studied using liquid chromatography/electrospray ionization tandem mass spectrometry for doping control purposes. The method consists of solid‐phase extraction using stable‐isotope‐labeled GHRP‐2 as an internal standard and subsequent ultra‐performance liquid chromatography/tandem mass spectrometry, and the two target peptides were determined at urinary concentrations of 0.5–10 ng/mL. The recoveries ranged from 84 to 101%, and the assay precisions were calculated as 1.6–3.8% (intra‐day) and 1.9–4.3% (inter‐day). Intravenous administration of GHRP‐2 in ten male volunteers was studied to demonstrate the applicability of the method. In all ten cases, unchanged GHRP‐2 and its specific metabolite AA‐3 were detected in urine. Copyright © 2010 John Wiley & Sons, Ltd.     

Study on liquid crystallinity in 2,9‐dialkylpentacenes

A series of semiconducting and symmetrical 2,9‐dialkylpentacenes was successfully synthesized via a five‐step process and their structures confirmed by ¹H NMR, IR and elemental analyses. Their liquid crystallinity was investigated by differential scanning calorimetry and polarizing optical microscopy. The introduction of alkyl chains also improved their solubility. For alkyl chains longer than butyl, focal conic or baton texture was observed, indicating the existence of an ordered smectic phase. Thermal analyses revealed that the both melting and smectic–isotropic transition temperatures show an odd–even effect when the alkyl chain is larger than heptyl or octyl. The synthesized compounds are promising candidates for semiconductors in organic field‐effect transistors because their liquid crystallinity allows easy molecular alignment in the device fabrication process.     

Pronounced rate enhancements in condensation reactions attributed to the fluorous tag in modified Mukaiyama reagents

The observed rate enhancement for the condensation reaction between 2-phenyl benzoic acid and isopropanol mediated by fluorous Mukaiyama reagents is described. It is shown that Mukaiyama reagents bearing a fluorous tag increase the reaction rate considerably when compared to their non-fluorous tagged counterpart. Furthermore, it is observed that the longer the fluorous chain, the higher the activity of the Mukaiyama reagent.     

On the Davis inequality in Banach function spaces

We give a characterization of those Banach function spaces in which the Davis inequality for martingales is valid. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A Convenient,Highly Efficient One-Pot Preparation of Peracetylated Glycals From Reducing Sugars

ABSTRACT

A convenient, highly efficient, one-pot, three-step procedure has been developed for the synthesis of peracetylated glycal derivatives from various reducing sugars including D-glucose, D-galactose, L-rhamnose, L-arabinose, D-maltose, D-lactose, and maltotriose. This procedure involves peracetylation of the reducing sugars with acetic anhydride and HBr/acetic acid followed by the transformation of the anomeric acetates to the corresponding bromides with additional HBr/acetic acid and finally reductive elimination of the 1-bromo and 2-acetoxy groups with Zn/CuSO₄·5H₂O in acetic acid/water containing sodium acetate. The overall yields of purified peracetylated glycals from the corresponding sugars range from 50 - 98%.

     

Temperature and pH stability of cellouronic acid

Cellouronic acid (CUA), (1 → 4)-β-d-polyglucuronate sodium salt, was prepared from regenerated cellulose by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated oxidation in water at pH 10. Changes in chemical structure and degree of polymerization (DP) of CUA by treatment in water under various pH and temperature conditions were studied to evaluate the stability of CUA. No depolymerization occurred on CUA in water at pH 1.0–7.0 and room temperature, while clear depolymerization took place at pH 10 and 13 by β-elimination. When heated in water at >50 °C, CUA was depolymerized by hydrolysis at pH 1.0 and 4.8, and by both hydrolysis and β-elimination at pH 7.0. Kinetic studies showed that CUA depolymerization rate constant was roughly increased with increasing the pH or temperature. Especially, the depolymerization rate constant at pH 13 was approximately 128 and 55 times greater than those at pH 1.0 and 10, respectively, at 60 °C. Activation energies of hydrolysis and β-elimination of CUA were approximately 100 and 20 kJ mol⁻¹, respectively.     

Cyclization of 1-benzyl-1,2-dihydro-2-(substituted methylene)quinolines to pyrrolo[1,2-a]quinoline derivatives

1-Alkyl-2-alkylthioquinolinium salts were prepared from 1-alkyl-2(1H)-quinolones via 1-alkyl-2(1H)-thioquinolones in two steps. Under mild conditions, the reaction of 1-alkyl-2-alkylthioquinolinium iodides with active methylene compounds in the presence of sodium hydride afforded 1-alkyl-1,2-dihydro-2-(substituted methylene)quinolines in good yields. The cyclization of 1-benzylquinolines using acetic anhydride produced the corresponding pyrrolo[1,2-a]quinoline derivatives.