A new approach to 6-deoxy-D-allofuranose- and 6-deoxy-L-talofuranose derivatives from 1,2:5,6-di-O-isopropylidene α-D-glucofuranose

3-O-Acetyl-1,2-O-isopropylidene--D-allofuranose (2 b) was prepared from 1,2:5,6-di-O-isopropylidene--D-allofuranose (1 b). Treatment of2 b with triphenylphosphine-diethyl azodicarboxylate afforded regio- and stereospecifically the 5,6-epoxy--D-allo derivative (3). The other diastereomeric compound, 5,6-epoxy-1,2-O-isopropylidene--L-talofuranose (6) was also prepared stereoselectively from2 b via the intermediates5 a and5 b. The epoxy sugars3 and6 were converted with lithium aluminum hydride to the corresponding 6-deoxy-1,2-O-isopropylidene--D-allofuranose (4 a) and --L-talofuranose (7 a) derivatives. Hydrolysis of4 a and7 a afforded 6-deoxy-D-allose and 6-deoxy-L-talose, respectively. The corresponding 3,5-di-O-acetyl- (4 b and7 b) and the 3,5-O-(tetraisopropyldisiloxane-1,3-diyl) derivatives (4 c and7 c) are also described. Selective removal of the isopropylidene group and subsequent acetylation offers a convenient route to prepare sugar derivatives containing furanose ring, like8 b, as a suitable precursor for nucleoside analogs.Herrn Prof. Dr.K. Komarek mit den besten Wünschen zum 60. Geburtstag gewidmet.     

Potentiometric and antimicrobial studies on the asymmetric Schiff bases and their binuclear Ni(II) and Fe(III) complexes; synthesis and characterization of the complexes

The protonation constants of two nitro-Schiff bases SB¹, SB² and three asymmetric tetradentate diimines H₂L¹, H₂L² and H₂L³ and the stability constants of their ML type binuclear Ni(II) and Fe(III) complexes have been determined potentiometrically. The asymmetric diimines are (2OH) RCHNC₆H₄CHNR′ (2OH) type compounds [where R = R′ = phenyl for H₂L¹; R = naphthyl, R′ = phenyl for H₂L² and R = R′ = naphthyl for H₂L³]. The effect of tautomeric forms on the acid-base properties of the diimines has been investigated and discussed. In addition, dimeric and binuclear Ni(II) and Fe(III) complexes of the diimines have been synthesized and characterized by physical and spectroscopic techniques. Also, in vitro antimicrobial activities of the diimines and the complexes have been evaluated against three bacteria: Micrococcus luteus (NRLL B-4375), Bacillus cereus (RSKK 863), Escherichia coli (ATCC 11230) and the fungus: Candida albicans (ATCC 10239).     

N-glycosylation and ubiquitinylation of PD-L1 do not restrict interaction with BMS-202: A molecular modeling study

The Programmed cell Death protein-1/Ligand 1 (PD-1/L1) checkpoint is a major target in oncology. Monoclonal antibodies targeting PD-1 or PD-L1 are used to treat different types of solid tumors and lymphoma. PD-L1-binding small molecules are also actively searched. The lead compound is the biphenyl drug BMS-202 which stabilizes PD-L1 protein dimers and displays a potent antitumor activity in experimental models. Here we have investigated the effect of N-glycosylation (at N35, N192, N200 and N219) and mono-ubiquitination (at K178) of PD-L1 on the interaction with BMS-202 by molecular modeling. Two complementary tridimensional models of PD-L1, based on available crystallographic structures, were constructed with BMS-202 bound. The structures were glycosylated, with a fucosylated bi-antennary N-glycan and ubiquitinated. Model 1 refers to glycoPD-L1 bearing 16 N-glycans, with or without 4 ubiquitin residues. Model 2 presents 8 N-glycans and 2 ubiquitin residues. In both cases, BMS-202 was bound to the protein interface, stabilizing a PD-L1 dimer. The incorporation of the N-glycans or the ubiquitins did not significantly alter the drug-protein recognition. The interface of the drug-stabilized protein dimer is unaffected by the glycosylation or ubiquitination. Calculations of the binding energies indicated that the glycosylation slightly reduces the stability of the drug-protein complexes but does not prevent the drug binding process. Our modeling study suggests that the drug can target efficiently the different forms of PD-L1 in cells, glycosylated, ubiquitinated or not. These models of N-glycosylated and ubiquitinated PD-L1 will be useful to study other PD-L1 protein complexes.     

Evaluation of recurrence relationships and numerical solutions for finite rotation matrix elements by using auxiliary functions

In this article, we derived several new recurrence relations of the rotation matrix elements by using Gauss’ recurrence formulas for hypergeometric functions and auxiliary functions , and . The aim of this contribution is to obtain general algorithm to compute the rotation matrix elements, paying attention to the use recurrence relationships of the auxiliary functions that allow the treatment of the functions with high angular momentum quantum numbers.     

Amine over-alkylation side products in the synthesis of BMS-955176

Over-alkylation side products are common in the alkylation of amines by substitution. In the synthesis of the novel HIV Maturation inhibitor BMS-955176, two over-alkylation byproducts were routinely observed at the penultimate synthetic step, in which a thiomorpholine dioxide side chain was added to the core molecule by alkylation of a primary amine. These two byproducts had drastically different HPLC relative retention times, despite both containing only one additional side chain. Adding complexity to the challenge of solving their structures was the proclivity of the two byproducts to interconvert. Positive- and negative-ion HRMS, as well as isolation and 1D and 2D NMR were utilized to determine their structures. These byproducts were additionally problematic in that they led to daughter impurities at the API step.     

Horseradish peroxidase-mediated oxidation of carcinogenic non-aminoazo dyes

Fifteen non-aminoazo dyes were oxidized when catalyzed by horseradish peroxidase (HRP) in the presence of H2O2. Aromaticdiazonium ions, the ultimate carcinogen, were detected in the reaction with all of azo compounds as the substrates for HRP. The rates of oxidative cleavage fairly depended on pH. Relative enzymatic activities were compared among 15 non-aminoazo dyes, and the structural requirements of the substrates for HRP were discussed in detail.     

Bioanalysis of dried saliva spot (DSS) samples using detergent-assisted sample extraction with UHPLC-MS/MS detection

Dried saliva spot (DSS) sampling is a non-invasive sample collection technique for bioanalysis that can be potentially implemented at the patient's home. A UHPLC-MS/MS assay was developed using detergent-assisted sample extraction to quantify BMS-927711, a drug candidate in development for the treatment of migraines, in human DSS. By implementing DSS sampling at the patients' home, the bioanalytical sample collection for pharmacokinetic evaluation can be done at the time of the acute migraine attack without the need for clinical visits. DSS samples were prepared by spotting 15 μL of liquid saliva onto regular Whatman FTA™ DMPK-C cards and verified with a UV lamp (at λ 254 nm or 365 nm) during DSS punching. The 4-mm DSS punches in a 96-well plate were sonicated with 200 μL of [¹³C₂, D₄]-BMS-927711 internal standard (IS) solution in 20/80 MeOH/water for 10 min, followed by sonication with 50 μL of 100 mM NH₄OAc with 1.0% Triton-X-100 (as detergent) prior to liquid-liquid extraction with 600 μL EtOAc/Hexane (90:10). UHPLC-MS/MS was performed with an Aquity^® UPLC BEH C18 Column (2.1 × 50 mm, 1.7 μm) on a Triple Quad™ 5500 mass spectrometer. The assay was linear with a concentration range from 2.00 to 1000 ng mL⁻¹ for BMS-927711 in human saliva. The intra- and inter-assay precision was within 8.8% CV, and the accuracy was within ±6.7% Dev of the nominal concentration values. This UHPLC–MS/MS assay has been successfully applied to determine the drug's pharmacokinetics within a clinical study. For the first time, we observed BMS-927711 exposure in human DSS, confirming the suitability of this sampling technique for migraine patients to use at home. Detergent-assisted extraction with Triton-X-100 could be very useful in DSS or other dried matrix spot (DMS) assays to overcome low or inconsistent analyte recovery issues.     

Lycium barbarum polysaccharide with potential anti-gastric cancer effects mediated by regulation of miR-202-5p/PIK3CA

Lycium barbarum polysaccharide (LBP) in addition to modifying inorganic nanoparticles shows different biological functions such as anti-cancer, antibacterial, and anti-aging performances. However, the potential mechanism of LBP on inhibition of cancer cell proliferation, particularly gastric cancer (GC), remains unknown. The goal of this study was to show how LBP induces its anti-cancer effects through regulation of the miR-202-5p/PIK3CA axis in GC. The MTT assay was used to assess the viability of AGT and GES-1 cells. Using quantitative real-time PCR we assessed miR-202-5p expression in AGS, BCG-823, GES-1, MKN-45, and SGC-790a cells. AGS cells were transfected with miR-202-5p, an inhibitor, and a small interfering RNA (siRNA) targeting PIK3CA. To show whether miR-202-5p directly targets PIK3CA, the luciferase reporter assay was used. Also, to assess protein levels of PIK3CA/AKT/mTOR, Bax/Bcl-2, Cleaved Caspase-3, and MMP9 and GC cell migration ability, western blot and transwell assays were used, respectively. The results showed that LBP decreased GC cell viability in a dose- and time-dependent manner. Furthermore, GC cell treatment with LBP substantially decreased cell proliferation and migration, while increased GC cell apoptosis. LBP induced the upregulation of caspase-3/7 and miR-202-5p in GC cells and directly and functionally targets PIK3CA, as verified by luciferase assay and anti-miR-202-5p’s capability to reverse the inhibitory effects of LBP on PIK3CA. LBP was also shown to decrease the expression of PIK3CA downstream members such as AKT and mTOR through miR-202-5p up-regulation. Anti-cancer properties of LBP in GC cells are possibly due to the up-regulation of miR-202, which inhibits the PIK3CA/AKT/mTOR axis.