Nucleotides Bearing Red Viscosity-Sensitive Dimethoxy-Bodipy Fluorophore for Enzymatic Incorporation and DNA Labeling

Nucleosides and 2'-deoxyribonucleoside triphosphates (dNTPs) bearing 3,3'-dimethoxy-2,2'-diphenyl-6-(4-hydroxyphenyl)-bodipy fluorophore attached through a propargyl or propargyl-triethylene glycol linker to position 5 of 2'-deoxycytidine were designed and synthesized. They exerted bright red fluorescence and good sensitivity to viscosity changing their lifetime from 1.6 to 4.5 ns. The modifed dNTPs were substrates for DNA polymerases and were used in enzymatic synthesis of labeled DNA through primer extension. The modified DNA probes served as viscosity sensors responding to protein binding by changes of lifetime. The nucleotide with longer linker (dC^pegMOBTP) was transported to live cells and incorporated into the genomic DNA, which can be useful for staining of DNA and imaging of DNA synthesis.

Metal-mediated synthesis of pyrrolines

The five-membered, nitrogen-containing pyrroline ring is a privileged structure. This ring is present in many bioactive compounds from natural sources. Pyrrolines-the dihydro derivatives of pyrroles-have three structural isomer classes, depending on the location of the double bond: 1-pyrrolines (3,4-dihydro-2H-pyrroles), 2-pyrrolines (2,3-dihydro-1H-pyrroles) and 3-pyrrolines (2,5-dihydro-1H-pyrroles). This review aims to describe the latest advances for the synthesis of pyrrolines by transition metal-catalyzed cyclizations. Only reactions in which the pyrroline ring is formed by metal promotion are described. Transformations of the pyrroline ring in other heterocycles, and the structural manipulations of the pyrroline itself are not discussed. The review is organized into three parts, each covering the metal-mediated synthesis of the three pyrroline isomers. Each part is subdivided according to the metal involved, and concludes with a brief description of notable biological activities within the class.

Alkoxyallene-based syntheses of preussin and its analogs and their cytotoxicity

Short syntheses of oxa-preussin, racemic preussin and (-)-preussin are reported. Starting from a racemic 3-nonyl-substituted methoxyallene derivative, its lithiation and addition to phenylethanal provided the corresponding allenyl alcohol that was converted into two diastereomeric dihydrofuran derivatives by silver nitrate-catalyzed 5-endo-trig cyclization. The acid hydrolysis of the enol ether moiety gave heterocyclic ketones and subsequent highly stereoselective reductions with l-selectride furnished 2-benzyl-5-nonylfuran-3-ol derivatives in good overall yield. The major all-cis-diastereomer has the skeleton and relative configuration of preussin and is hence called oxa-preussin. An analogous sequence with the same allene, but an N-sulfonyl imine as the electrophile, finally led to racemic preussin. The stereoselectivities of the individual steps are discussed in detail. With an enantiopure 2-benzyl-5-nonylpyrrolidin-3-one intermediate the preparation of (-)-preussin with an enantiomeric ratio of >95 : 5 could be accomplished in a few steps. The sign of the optical rotation of this product finally proved the absolute configurations of its precursors and demonstrated that our chiral auxiliary-based route led to the antipode of the natural product. The cytotoxicity of several of the prepared heterocycles against MCF-7 tumor cells was investigated and five compounds, including racemic and enantiopure (-)-preussin, were identified as highly cytotoxic with IC50 values in the range of 3-6 μM.

Novel Alkoxy-Substituted Dipyrrins and Near-IR BODIPY Dyes-Preparation and Photophysical Properties

Starting from 3-alkoxy-2-aryl-substituted pyrroles and aromatic aldehydes, a collection of new dipyrrins was prepared. Under the standard conditions of Treibs, these were converted into the corresponding boron dipyrrins (BODIPYs). Compounds of this type with alkoxy groups at C-3 position of both pyrrole subunits are new and hence the photophysical properties of this collection of novel dipyrrins and BODIPY dyes were investigated. The dipyrrins show absorption maxima up to 596 nm and emissions of up to 677 nm. For the BODIPY series a remarkable effect of the alkoxy groups was identified, resulting in red shifts for absorptions and emissions. The compound substituted with two 2-thien-2-yl groups and a meso-C₆ F₅ substituent shows an absorption maximum at 725 nm and emits at 754 nm and thus is a new representative of a near-IR BODIPY dye related to certain aza-BODIPYs. Our results demonstrate the influence of the alkoxy groups on the spectroscopic data and reveal the potential of 3-alkoxy-2-aryl-substituted pyrroles for the design of new fluorophores.