Influence of D-Amino Acids in Beer on Formation of Uric Acid

Prekomjerna konzumacija piva može dovesti do povećanja koncentracije mokraćne kiseline u serumu, čime se povećava rizik nastanka uričnog artritisa (gihta), što se prethodno dovodilo u vezu s velikim udjelom purina u pivu. Međutim, novija istraživanja pokazuju da konzumacija povrća bogatog purinima i grahorica ne povećava koncentraciju mokraćne kiseline, što opovrgava tu tvrdnju. Još uvijek nije objašnjeno zašto povećana konzumacija piva može povećati rizik nastanka gihta, pa su ispitani drugi uzročnici nakupljanja mokraćne kiseline u krvi. Pivo sadržava relativno velike koncentracije D-aminokiselina koje nastaju racemizacijom L-aminokiselina tijekom prerade hrane. Katalizom pomoću D-aminokiselinske oksidaze iz D-aminokiselina nastaje H2O2, čijom oksidacijom u prisutnosti Fe2+ nastaju hidroksilni radikali. Pritom dolazi do oštećenja DNA i nastanka purinskih baza u većoj količini, iz kojih djelovanjem različitih enzima nastaje mokraćna kiselina. Neki dodaci hrani, kao što su vitamini i ioni joda, potiču nastanak mokraćne kiseline iz D-aminokiselina. D-aminokiseline u pivu imaju ključnu ulogu u povećanju koncentracije mokraćne kiseline. Biološka uloga D-aminokiselina može objasniti pojavu gihta kod osoba koje učestalo konzumiraju pivo.Excessive intake of beer could increase serum uric acid levels, leading to high risk of gout, which was previously attributed to high purine content in beer. Recent reports that purine-rich vegetables and bean products do not cause higher uric acid levels do not support this theory. Why excessive intake of beer could increase a high risk of gout has been unclear. Other factors affecting the accumulation of uric acid in the blood have been explored. Beer contains relatively high levels of D-amino acids due to the racemization of l-amino acids induced by food processing. D-amino acid was catalyzed by D-amino acid oxidase to produce H2O2, which is further oxidized in the presence of Fe2+ to produce hydroxyl radicals, resulting in DNA damage and formation of a large amount of purine bases, which are oxidized to uric acid by a series of enzymes. Some food ingredients, such as vitamins and I–, prompt D-amino acids to form uric acid. D-amino acids in beer are one of the key factors responsible for the increase in uric acid levels. The biological response of D-amino acids could explain gout occurrence in beer drinkers

Naphthotetrathiophene-Based Helicene-Like Molecules: Synthesis and Photophysical Properties

Two novel helicene-like molecules based on naphthotetrathiophene are successfully synthesized. All target molecules and intermediates are characterized by ¹H NMR, ¹³C NMR, IR, and HRMS. Their electrochemical and photophysical properties are studied. The configurations of the molecules are optimized by DFT quantum calculations and UV–vis behaviors are also predicted to further understand the origin of different absorption bands. We believe the current work illustrated an efficient way for the design and synthesis of sophisticated structures with naphthotetrathiophene as building blocks

Synthesis and Characterization of Cyclooctatetrathiophenes with Different Connection Sequences

Based on the selectivity of deprotonation of 5,5′-bistrimethylsilyl-2,3′-bithiophene (<b>4</b>) in the presence of <i>n</i>-BuLi, three new cyclooctatetrathiophenes (<b>COTh</b>s), <b>COTh-1</b>, <b>COTh-2</b>, and <b>COTh-3</b> have been efficiently developed via intermolecular or intramolecular cyclizations. Their crystal structures clearly show that the different connectivity sequence of the thiophene rings in the molecules. The CV data and UV–vis absorbance spectra of <b>COTh</b>s are also described. In addition, the time-dependent density functional theory (TDDFT) calculations accurately reproduce experimental observations and afford band assignment

Synthesis of Pyrrole via a Silver-Catalyzed 1,3-Dipolar Cycloaddition/Oxidative Dehydrogenative Aromatization Tandem Reaction

Pyrroles are an important group of heterocyclic compounds with a wide range of interesting properties, which have resulted in numerous applications in a variety of fields. Despite the importance of these compounds, there have been few reports in the literature pertaining to the synthesis of pyrroles from simple alkenes using a one-pot sequential 1,3-dipolar cycloaddition/​aromatization reaction sequence. Herein, we report the development of a benzoyl peroxide-mediated oxidative dehydrogenative aromatization reaction for the construction of pyrroles. We subsequently developed a one-pot tandem reaction that combined this new method with a well-defined silver-catalyzed 1,3-dipolar cycloaddition reaction, thereby providing a practical method for the synthesis of multisubstituted pyrroles from easy available alkenes. The mechanism of this oxidative dehydrogenative aromatization reaction was also examined in detail

Small Molecules of Cyclopentadithiophene Derivatives: Effect of Sulfur Atom Position and Substituted Groups on Their UV–Abs Properties

Thiophene-based organic semiconductors used as the active components have received much attention. Their photoelectric properties can be easily tuned with various substitutions at different positions on molecular structures. Here, we synthesized series cyclopentadithiophene (CDT) derivatives with sulfur atoms at <i>ortho</i>- (<i>o</i>-CDT), <i>meta</i>- (<i>m</i>-CDT), and <i>para</i>-positions (<i>p</i>-CDT) of the bridge carbon. These CDT derivatives were substituted by carbonyl/dicyanomethylene at the bridge position and/or by phenyl groups at the α position, respectively. Due to the different conjugation extent and the variation of donor–acceptor (D–A) interaction originating from the change of sulfur atom position, diverse absorption spectra were observed. Especially for dicyanomethylene substituted <i>o</i>-CDT with phenyl as substitution group (DPCN-<i>o</i>-CDT), its absorption spectrum covers the whole region of visible light. Combining with the electrochemical behaviors and theoretical calculations, it was found that the sulfur atoms mainly contribute to the molecular conjugation in these CDT derivatives, especially for <i>o</i>-CDT derivatives. For phenyl groups, they primarily act as electron donor in <i>m</i>-CDT derivatives, and chiefly contribute to molecular conjugation in <i>p</i>-CDT derivatives, and simultaneously work as electron donor and conjugation component in <i>o</i>-CDT derivatives, respectively

Synthesis of Pyrrolo[2,1,5-<i>cd</i>]indolizines through Dehydrogenative Heck Annelation of Indolizines with Diaryl Acetylenes Using Dioxygen as an Oxidant

A dehydrogenative Heck annelation reaction of indolizine with diaryl acetylene via dual C–H bond cleavage was developed. Oxygen gas was employed as a clean oxidant in this catalysis under base-free conditions. Diarylpyrrolo­[2,1,5-<i>cd</i>]­indolizines were synthesized with high atom economy. In addition, kinetic isotope experiments provided evidence for C–H bond metalation of the 5-position of the indolizine as the rate-limiting step

Silicon Spiro Double Helicene-like Compounds Based on Dithieno­[2,3‑<i>b</i>:3′,2′‑<i>d</i>]­thio­phene: Syntheses and Crystal Structures

Silicon spiro carbon–sulfur double helicene-like compounds <b>1</b> and <i>rac-</i><b>2</b> were synthesized from 2,5-bis-trimethyl­silanyl­dithieno­[2,3-<i>b</i>:3′,2′-<i>d</i>]­thio­phene, with total yields of 17% and 7%, respectively. ¹H and ¹³C NMR spectra and X-ray crystallographic analysis showed the predicted 4-fold symmetry for <b>1</b> and <i>rac-</i><b>2</b> and confirmed their spiro double helicene-like spatial configurations. The absorption behavior of compounds <b>1</b> and <i>rac-</i><b>2</b> was also investigated