Christian Becu

New synthesis of pipecolic acid and analogs

Abstract Pipecolic acid congeners are synthesised from α-cyanoamides, obtained by substitution of α-methoxyamides with trimethylsilyl cyanide in an alternative route via oxidation of amidoalkylationproducts of the α-methoxyamides.

Considerations concerning interaction characterization of oligopeptide mixtures with vancomycin using affinity capillary electrophoresis-electrospray mass spectrometry

In the past few years affinity capillary electrophoresis (ACE) has proven to be a powerful tool to study molecular interactions. In ACE the change in electrophoretic mobility between a free and a complexed ligand with a receptor dissolved in the background electrolyte is observed. It provides an accurate way to calculate binding or dissociation constants and, when coupled to mass spectrometry, it forms a promising method to analyze solution‐based combinatorial libraries. We report a model study on the macrocyclic antibiotic vancomycin using a 36‐component library of tetrapeptides of the type 9‐fluorenylmethoxycarbonyl (Fmoc)‐L‐Asp‐L‐Asp‐D‐Xaa‐D‐Xaa. The mass spectrometry conditions were optimized by fine‐tuning the background electrolyte and sheath flow composition to achieve optimal sensitivity in the negative ionization mode. Different types of capillaries were also evaluated on their potential to screen combinatorial libraries. The library components that show the strongest interaction were identified. The dissociation constants of a mixture of six compounds with a broad affinity range were simultaneously established by Scatchard analysis on ACE‐MS.

The mechanism of the rearrangement of the neurotoxin β-odap to α-odap

Abstract The diketopiperazine suggested to be the intermediate during the spontaneous isomerization of β-ODAP and α-ODAP was synthesized. Its behaviour was studied at selected pH values and provided evidence that its natural occurrence is unlikely. 2-Hydroxy-imidazolidine-2,4-dicarboxylic acid (for the rearrangement β-ODAP↔α-ODAP) or 2-hydroxy-pyrimidine-2,4-dicarboxylic acid (for the rearrangement Yγ-ODAB↔α-ODAB) are suggested to be the unstable intermediates.

2 Characterization of γ-glutamyl-β-(isoxazolinonyl)-alanine from lathyrus sativus and its decarboxylation product from lathyrus odoratus

Abstract The γ-glutamyl derivative of β-(isoxazolin-5-on-2-yl)-alanine was found in seedlings of Lens culinaris and Lathyrus sativus . The chemical and spectroscopic properties are compared with its decarboxylation product previously found in seedlings of Lathyrus odoratus . NMR studies of the two derivatives indicate the absence of cyclization and the probability of cis-trans isomers. Some biochemical implications related to potential ways to detoxify Lathyrus sativus are discussed.