Solvent-Dependent Changes in the Ene Reaction of RTAD with Alkenes:0.167em The Cyclopropyl Group as a Mechanistic Probe

(Chemical Equation Presented) The vinylcyclopropyl moiety was used as an efficient probe to test mechanistic possibilities of the triazolinedione-alkene ene reaction. In non-hydroxylic solvents, this reaction afforded only the ene adducts via a closed three-membered aziridinium imide (Al) intermediate, whereas in hydroxylic solvents a dipolar intermediate is favored and trapped by the cyclopropyl moiety to form the corresponding cyclopropyl-rearranged solvent-trapped adducts. © 2006 American Chemical Society

[60]Fullerene supported on silica and γ-alumina sensitized photooxidation of olefins: Chemical evidence for singlet oxygen and electron transfer mechanism

Fullerene C60 supported on silica and γ-alumina (2% w/w C60/SiO2 and C60/Al2O3) sensitizes the photooxidation of alkenes via singlet oxygen and/or electron transfer mechanism, depending on the solvent and the substrate

Investigations into the elimination profiles and metabolite ratios of micro-dosed selective androgen receptor modulator LGD-4033 for doping control purposes

LGD-4033 (ligandrol) is a selective androgen receptor modulator (SARM), which is prohibited in sports by the World Anti-Doping Agency (WADA) and led to 62 adverse analytical findings (AAFs) in 2019. But not only deliberate doping with LGD-4033 constitutes a problem. In the past years, some AAFs that concerned SARMs can be attributed to contaminated dietary supplements (DS). Thus, the urgency to develop methods to differentiate between inadvertent doping and abuse of SARMs to benefit from the performance-enhancing effect of the compound in sports is growing. To gain a better understanding of the metabolism and excretion patterns of LGD-4033, human micro-dose excretion studies at 1, 10, and 50 mu g LGD-4033 were conducted. Collected urine samples were prepared for analysis using enzymatic hydrolysis followed by solid-phase extraction and analyzed via LC-HRMS/MS. Including isomers, a total of 15 phase I metabolites were detected in the urine samples. The LC-HRMS/MS method was validated for qualitative detection of LGD-4033, allowing for a limit of detection (LOD) of 8 pg/mL. The metabolite M1, representing the epimer of LGD-4033, was synthesized and the structure elucidated by NMR spectroscopy. As the M1/LGD-4033 ratio changes over time, the ratio and the approximate LGD-4033 concentration can contribute to estimating the time point of drug intake and dose of LGD-4033 in doping control urine samples, which is particularly relevant in anti-doping result management

High resolution full scan liquid chromatography mass spectrometry comprehensive screening in sports antidoping urine analysis

The aim of this paper is to present the development and validation of a high-resolution full scan (HR-FS) electrospray ionization (ESI) liquid chromatography coupled to quadrupole Orbitrap mass spectrometer (LC/Q/Orbitrap MS) platform for the screening of prohibited substances in human urine according to World Antidoping Agency (WADA) requirements. The method was also validated for quantitative analysis of six endogenous steroids (epitestosterone, testosterone, 5α-dihydrotestosterone, dehydroepiandrosterone, androsterone and etiocholanolone) in their intact sulfates form. The sample preparation comprised a combination of a hydrolyzed urine liquid–liquid extraction and the dilute & shoot addition of original urine in the extracted aliquot. The HR-FS MS acquisition mode with Polarity Switching was applied in combination of the Quadrupole-Orbitrap mass filter. The HR-FS acquisition of analytical signal, for known and unknown small molecules, allows the inclusion of all analytes detectable with LC–MS for antidoping investigations to identify the use of known or novel prohibited substances and metabolites after electronic data files’ reprocessing. The method has been validated to be fit-for-purpose for the antidoping analysis