Hünlich Base: (Re)Discovery, Synthesis, and Structure Elucidation after a Century

After almost 100 years, the structure of the product of the reaction between 2,4-diaminotoluene and formaldehyde was elucidated: derivative <b>3</b>, which we call the Hünlich base, was synthesized on a multigram scale and its enantiomers were easily separated in preparative amounts. Furthermore, transformation of the NH₂ groups to the corresponding bis-iodides and bis-azides is presented. The latter was also used for desymmetrization by click chemistry

Hünlich Base: (Re)Discovery, Synthesis, and Structure Elucidation after a Century

After almost 100 years, the structure of the product of the reaction between 2,4-diaminotoluene and formaldehyde was elucidated: derivative <b>3</b>, which we call the Hünlich base, was synthesized on a multigram scale and its enantiomers were easily separated in preparative amounts. Furthermore, transformation of the NH₂ groups to the corresponding bis-iodides and bis-azides is presented. The latter was also used for desymmetrization by click chemistry

Sensitive and Site-Specific Identification of Carboxymethylated and Carboxyethylated Peptides in Tryptic Digests of Proteins and Human Plasma

Glycation refers to a nonenzymatic post-translational modification formed by the reaction of amino groups and reducing sugars. Consecutive oxidation and degradation can produce advanced glycation end products (AGEs), such as <i>N</i>^ε-(carboxyethyl)­lysine (CEL) and <i>N</i>^ε-(carboxymethyl)­lysine (CML). Although CEL and CML are considered to be markers of arteriosclerosis, diabetes mellitus, and aging, the modified proteins and the exact modification sites are mostly unknown due to their low frequency and a lack of enrichment strategies. Here, we report characteristic fragmentation patterns of CML- and CEL-containing peptides and two modification-specific reporter ions for each modification (CML, <i>m</i>/<i>z</i> 142.1 and 187.1; CEL, <i>m</i>/<i>z</i> 156.1 and 201.1). The protocol allowed sensitive and selective precursor ion scans to detect the modified peptides in complex sample mixtures. The corresponding <i>m</i>/<i>z</i> values identified eight CEL/CML-modification sites in glycated human serum albumin (HSA) by targeted nano-RPC–MS/MS. The same strategy revealed 21 CML sites in 17 different proteins, including modified lysine residues 88 and 396 of human serum albumin, in a pooled plasma sample that was obtained from patients with type 2 diabetes mellitus

A Fast Entry to Furanoditerpenoid-Based Hedgehog Signaling Inhibitors: Identifying Essential Structural Features

New, small molecule Hedgehog (Hh) pathway inhibitors, such as the furanoditerpenoid taepeenin D, are of high medicinal importance. To establish key structure–activity relationships (SARs) for this lead, a synthetic sequence has been developed for the expedient preparation of several derivatives and their evaluation as Hh inhibitors exploiting its structural similarity to abietic acid. While C(14) substitution is not essential for biological activity, the presence of a hydrogen bond acceptor at C(6) and an intact benzofuran moiety are

Curare Alkaloids: Constituents of a Matis Dart Poison

A phytochemical study of dart and arrow poison from the Matis tribe led to the identification of d-(−)-quinic acid, l-malic acid, ethyldimethylamine, magnoflorine, and five new bisbenzyltetrahydroisoquinoline alkaloids (BBIQAs), <b>1</b>–<b>5</b>. <i>d</i>-Tubocurarine could not be identified among these products. BBIQA (<b>3</b>) contains a unique linkage at C-8 and C-11′. All structures were characterized by a combination of NMR and HRESIMS data. The effects of Matis poison and individual BBIQAs (<b>1</b>–<b>3</b>) on rat muscle nAChR expressed in <i>Xenopus</i> oocytes have been investigated using the two-electrode voltage clamp technique

Chemical structure of Tripolin A and Tripolin B.

<p>Chemical structure of Tripolin A and Tripolin B.</p

Tripolin A selectively inhibits Aurora A over Aurora B in cultured tumor cells.

<p>(A) Representative immunofluorescence images of HeLa cells in metaphase treated with solvent control (DMSO), 20 µM Tripolin A or Tripolin B for 5 h and 24 h. In the merged images Aurora A is pseudocolored red, pAurora T288 green, DNA blue. (Scale bars, 5 µm). (B) Fluorescence intensity (% percentage) of pAurora A T288 on centrosomes and total Aurora A on spindles were quantified in control metaphase cells or cells treated with Tripolin A or Tripolin B (n≥20 cells for each group, from at least two independent experiments). **: 0.0010.05; (Mann-Whitney test, two-tailed). Error bars represent SEM. (C) Western Blot analysis for Aurora A, Aurora B and pHistone H3 Ser10 in Tripolin A and Tripolin B-treated mitotic cells. α-tubulin was used as a loading control. (D) Representative immunofluorescence images of bipolar metaphase HeLa cells treated with solvent control (DMSO), 20 µM Tripolin A or Tripolin B for 24 h. In the merged images pHistone H3 Ser10 is pseudocolored red, Aurora B green, DNA blue. (Scale bars, 5 µm).</p

Tripolin A treatment results in spindle and centrosomal defects.

<p>(A) Representative immunofluorescence images of mitotic HeLa cells treated with DMSO, 20 µM Tripolin A for 24 h, 100 nM MLN8237 for 24 h or Aurora A siRNAs. In the merged images α-tubulin is pseudocolored red, DNA blue. (Scale bars, 5 µm). (B) Graph showing the percentage of normal, multipolar, misaligned, disorganized and monopolar figures in control mitotic cells (DMSO or control siRNAs) and mitotic cells treated with Tripolin A, MLN8237 or Aurora A siRNA (n = 300 cells for each group, from three independent experiments). (C) Western Blot analysis for Aurora A levels in Aurora A siRNA treated cells. α-tubulin was used as a loading control. (D) Images of mitotic HeLa cells treated with DMSO, 20 µM Tripolin A for 5 h and 24 h or Aurora A siRNA. In the merged images Aurora A is pseudocolored red, pericentrin green, DNA blue. (Scale bar 5 µm). (E) Graph showing the percentage of mitotic cells with fragmented centrosomes (up), or acentrosomal poles (down) in control mitotic cells (DMSO or control siRNA) and mitotic cells treated with Tripolin A, or Aurora A siRNA (n = 150 cells for each group, from three independent experiments).</p

Tripolins inhibit Aurora kinase activity <i>in vitro</i>.

<p><i>(</i>A) Chemical structure of Tripolin A and Tripolin B. (B) Graph showing IC₅₀ values (in µM) of Tripolin A (red) and Tripolin B (green) in the presence of different ATP concentrations, using an <i>in vitro</i> kinase assay. (C) Differential Scanning Fluorimetry results for Aurora A in the presence and absence of the inhibitors. Blue curve determines the melting temperature of Aurora A alone (45°C), red in the presence of Tripolin A (47°C) and green in the presence of Tripolin B (53°C).</p

Selectivity of Tripolins against a panel of kinases.

<p>IC₅₀ values of Tripolin A and Tripolin B against Aurora A, Aurora B and a panel of other selected kinases.</p