We presented the first metal-catalyzed asymmetric reduction towards alpha-CF3-1,3-glycols in excellent stereopurity. Our new access route to gamma-hydroxy-alpha-CF3-methanols possessing up to three contiguous stereogenic centers relies on an enantio- and diastereoselective double dynamic kinetic resolution during an efficient and practical ansa-ruthenium(II)-catalyzed asymmetric transfer hydrogenation in formic acid/triethylamine. Most importantly, this concept of double ATH-DKR is unprecedented in the literature. This article was selected by The Editorial Board of Synfacts-Thieme Verlag KG for its important insights as “Synfact of the month” (Synfacts 2016,6,589). The aim of Synfacts is to inform readers on a monthly basis and in a concise manner of the most significant recent developments and future trends in synthetic chemistry in order to stimulate the own research and the development of exciting new ideas.
Guanine-rich DNA sequences can fold into four-stranded DNA structures called G-quadruplexes. They have been shown to form in telomere regions of a genome, in the regulatory regions as well as in the genomes of viruses. Formation of G-quadruplexes in vitro has been unambiguously demonstrated, while their detection inside living cells is still a challenging task. A small-molecule optical probe DAOTA-M2 provides means to monitor G-quadruplexes in cells. A key feature of DAOTA-M2 is its significantly longer fluorescence lifetime upon binding to G-quadruplexes in comparison to free probe in solution or bound to single- or double-stranded DNA. Using NMR spectroscopy we characterized the interactions between DAOTA-M2 and the G-quadruplex formed by promoter region of c-myc gene. NMR data indicate formation of a well-defined complex between G-quadruplex and DAOTA-M2 with 1:2 binding stoichiometry (pdb id: 5LIG5). The obtained structural information allows in depth understanding on how triangulenium probes interact with G-quadruplexes and stimulates further development of novel fluorescence probes with improved selectivity and affinity. Results of our study were published in the journal Angew. Chem. Int. Ed. (2016, 55, 12508–12511).
Human telomere sequences at the 3'-ends of linear chromosomes are comprised of hexanucleotide TTAGGG repeats that are associated with cellular aging and are promising targets for anticancer drug development. Diverse topologies adopted by telomere G-rich sequences are highly sensitive to chemical environment and are involved in complex structural equilibria. Due to intrinsic difficulties in studying and detecting structures in equilibrium we applied different stimuli with the goal to shift the equilibrium thus enabling determination of high resolution structures. Better structural characterization would lead to advancements in understanding of fundamental G-quadruplex folding mechanisms. Oligonucleotide d[TAGGG(TTAGGG)2TTAGG] originating from human telomere sequence has been shown to fold into diverse secondary structures in the presence of K+ ions. Populations of TD and KDH+ forms that are dominant at pH 7 and pH 5 can be controlled and switched by pH changes in a reversible fashion. Moreover, NMR studies revealed that (de)protonation of the specific adenine residue is key for pH driven structural transformation. Most noticeable benefits of the system are long-term reversibility and rapid response which could be utilized as a conformational switch within different compartments of a living cell enabling specific ligand and protein interactions. The results of this study were published in Angew. Chem. Int. Ed. (2016, 55, 1993-1997).
Biosimilar substances are drugs that are increasingly used to treat cancer, infectious, autoimmune, cardiovascular, neurological and other diseases. Properties and advantages of biological drugs rely on the fact that they represent natural molecules for organism which reduces risk of side effects during treatment. The patents for the originator formulations have either already expired or are about to expire in the near future, opening the market for biosimilars. Biosimilar formulations from various vendors are cheaper, equally effective and more accessible for a wider range of patients. From the point of health safety, it is necessary to develop new and sophisticated comparative methods of individual samples as well as to control production. Biosimilar substances are very complex biological macromolecules which makes their comparative studies on the level of structure, function and clinical safety very demanding. In collaboration with researchers from Lek, Mengeš we have developed new methods based on nuclear magnetic resonance (NMR) and mathematically-based biosimilarity metrics analysis of spectra. For the purpose of comparative studies, we have chosen 2D NMR experiments in which the intensities or chemical shift of cross-peaks are related to protein structure. Signals in NMR spectra thus represent unique protein's fingerprint at the atomic level of resolution. NMR results were further analysed using mathematical methods based on matrices to quickly and accurately compare individual fingerprints of samples and determine the index of similarity at the structural level between samples. The proposed method was successfully applied to a small protein filgrastim (neutropenia treatment) and a relatively large monoclonal antibody rituximab (lymphoma treatment). Development of the proposed method was published in the Scientific Reports journal (2016, 6: 32201).
In the study, we verified the authenticity and geographical origin of pumpkin seed oil with chemical analysis of fatty acid composition and isotopic characterization in combination with chemometric analysis. Work was carried out on 38 samples of pumpkin seed oil collected from different parts of the world. Pumpkin seed oil is important because of its nutritional properties (high poliunsuturated fatty acids, vitamin E, carotenoids and phytosterols) and favorable effects on health in cases of prostate cancer, macular degeneration, and high levels of cholesterol. Because of its high price it is a target of counterfeiting and in our study, we have managed to develop a methodology that allows determination of geographic origin and level of botanical purity at 1% foreign oil.