Leszek Siergiejczyk

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Syntheses of "glycospirostanes" from 3beta-hydroxy-23,24-dinor-5alpha-cholano-22,16-lactone and 3alpha-hydroxy-23,24-dinor-5beta-cholano-22,16-lactone were performed. The key step of these syntheses was ring-closing metathesis of the corresponding C,O-diallyl derivative. Further elaboration of the six-membered ring F consisted of allylic hydroxylation with(More)
BACKGROUND The aim of this study was to evaluate the relationship between N-acetylaspartate (NAA) levels in selected brain regions and cognitive performance in patients with first-episode schizophrenia. MATERIAL/METHODS Thirty patients (20 male, 10 female; mean age: 22.5 years) with the diagnosis of first-episode schizophrenia and 19 comparable healthy(More)
PURPOSE To evaluate proton magnetic resonance spectroscopy (1H MRS) features in order to assess hepatocellular activation in chronic hepatitis C and human immunodeficiency virus/hepatitis C (HIV/HCV) co-infected patients. MATERIAL AND METHODS Liver in vivo 1H MR spectra were obtained in 14 patients with hepatitis C virus infection (HCV), 20 HIV/HCV(More)
A group of biologically active 4-azasteroids was studied by 13C-NMR spectroscopy in solution and in the solid phase. A full assignment of signals in the spectra of samples in chloroform was performed for thirteen 4-azasteroids using two-dimensional techniques. Substituent and steric effects of a nitrogen atom, and their influence on chemical shifts of the(More)
The condensation of 16-dehydropregnenolone acetate with 2-aminobenzimidazole was studied. The polycyclic aromatic product was formed as a single regioisomer in a cascade reaction comprising addition, cyclization, autoxidation, and aromatization, in addition to the rearranged D-homo product. The reaction mechanism based on DFT calculations is proposed.
The reaction of 23-oxotigogenin acetate with TMSOTf in THF afforded the corresponding bisnorcholanic lactone in 60% yield. The analogous reactions carried out in dichloromethane or benzene gave the rearranged products--the isomeric spirostanic ketone (10-15%) and bisfuran (40-42%). Similar products were also obtained upon treatment of 23,24-epoxysapogenins(More)
Electrochemical cholesterylation of various sugars with cholesteryl diphenylphosphate was studied. The reaction afforded mono-, di-, tri-, and tetra-cholesterylated products using equivalent amounts of the reagent. The reactions turned out to be completely stereoselective with respect to both sugar and steroid but only partially regioselective - primary and(More)
UNLABELLED MR proton spectroscopy (1H MRS) has been widely applied in characterisation and differentiation of brain tumors, staging, recurrence of pathologic process, post radiotherapy changes and other lesions mimicking neoplasm like abscesses. Despite of many studies performed over last 3 years in many countries spectroscopic pattern (phenotype) of brain(More)
Several derivatives of cholesterol and other 3β-hydroxy-Δ(5)-steroids were prepared and tested as sterol donors in electrochemical reactions with sugar alcohols. The reactions afforded glycoconjugates with sugar linked to a steroid moiety by an ether bond. Readily available sterol diphenylphosphates yielding up to 54% of the desired glycoconjugate were(More)