Thiophenol-Mediated 1,5-Hydrogen Transfer for the Preparation of Pyrrolizidines, Indolizidines, and Related Compounds

1523-706

Preparation of 5-Membered Rings via Translocation-Cyclization of Vinyl Radicals

Vinyl radicals have a propensity to rearrange via intramolccular 1,5-hydrogen transfer to the more-stable alkyl radicals, which themselves possess a suitable structure to undergo rapid 5-exo-trig cyclizations. This tandem radical translocation-cyclization process represents a useful tool for the preparation of a wide range of five-membered rings. Moreover, this reaction is highly selective and, due to its radical nature, tolerates a variety of functional groups. During the last decade, tin-free procedures have emerged, rendering this process very attractive for the synthesis of natural products and their analogues. Selected examples of this strategy illustrating the scope of the method are described. 1 Introduction 2 Vinyl Radicals from Vinyl Halides 3 Vinyl Radicals Generated by Addition to Alkynes and Allenes 3.1 Addition of Carbon-Centered Radicals 3.1.1 Intermolecular Addition of Carbon-Centered Radicals 3.1.2 Intramolecular Addition of Carbon-Centered Radicals 3.2 Addition of Tin-Centered Radicals 3.3 Addition of Oxygen-Centered Radicals 3.4 Addition of Nitrogen-Centered Radicals 3.5 Addition of Sulfur-Centered Radicals 3.6 Addition of Phosphorus-Centered Radicals 4 Translocation-Cyclization Processes Involving a Stereoselective Hydrogen Atom Transfer 5 Conclusio

Diastereoselective Radical-Mediated Hydrogen-Atom Abstraction

International audienc

Diastereoselective Radical-Mediated Hydrogen-Atom Abstraction.

International audienc

Labelling of Fusion Proteins with Synthetic Probes

The invention relates to new proteins called alkylcytosine transferases (ACTs) derived from O6-alkylguanine-DNA alkyltransferase, and to substrates for ACTs specifically transferring a label to these ACTs and to fusion proteins comprising these. The substrates according of the invention are substituted cytosines of formula (I) wherein R1 is an aromatic or a heteroaromatic group, or an optionally substituted unsaturated alkyl, cycloalkyl or heterocyclyl group with the double bond connected to OCH2-; R2 is a linker; and L is a label or a plurality of same or different labels. The invention further relates to methods of transferring label L from these substrates of formula (I) to ACTs and ACT fusion proteins. The system of ACT-compound of formula (I) is particularly suitable for double labelling studies together with the known system O6-alkylguanine-DNA alkyltransferase (AGT)-benzylguanines

Labelling of fusion proteins with synthetic probes

The invention relates to new proteins called alkylcytosine transferases (ACTs) derived from O-alkylguanine-DNA alkyltransferase, and to substrates for ACTs specifically transferring a label to these ACTs and to fusion proteins comprising these. The substrates according of the invention are substituted cytosines of formula (I) wherein R1 is an aromatic or a heteroaromatic group, or an optionally substituted unsaturated alkyl, cycloalkyl or heterocyclyl group with the double bond connected to OCH2- R2 is a linker and L is a label or a plurality of same or different labels. The invention further relates to methods of transferring label L from these substrates of formula (I) to ACTs and ACT fusion proteins. The system of ACT-compound of formula (I) is particularly suitable for double labelling studies together with the known system O6-alkylguanine-DNA alkyltransferase (AGT)-benzylguanines

Cell-Permeant and photocleavable chemical inducer of dimerization

Chemical inducers of dimerization (CIDs) have been developed to orchestrate protein dimerization and translocation. Here we present a novel photocleavable HaloTag- and SNAP-tag-reactive CID (MeNV-HaXS) with excellent selectivity and intracellular reactivity. Excitation at 360 nm cleaves the methyl-6-nitroveratryl core of MeNV-HaXS. MeNV-HaXS covalently links HaloTag- and SNAP-tag fusion proteins, and enables targeting of selected membranes and intracellular organelles. MeNV-HaXS-mediated translocation has been validated for plasma membrane, late endosomes, lysosomes, Golgi, mitochondria, and the actin cytoskeleton. Photocleavage of MeNV-HaXS liberates target proteins and provides access to optical manipulation of protein relocation with high spatiotemporal and subcellular precision. MeNV-HaXS supports kinetic studies of protein dynamics and the manipulation of subcellular enzyme activities, which is exemplified for Golgi-targeted cargo and the assessment of nuclear import kinetics

Stereoselective Radical Translocation

The stereochemical outcome of intramolecular radical mediated hydrogen transfer (= radical translocation) is discussed. Low to excellent levels of stereocontrol are observed making such processes attractive for applications in target-oriented synthesis

An engineered protein tag for multi-protein labeling in living cells

The visualization of complex cellular processes involving multiple proteins requires the use of spectroscopically distinguishable fluorescent reporters. We have previously introduced the SNAP-tag as a general tool for the specific labeling of SNAP-tag fusion proteins in living cells. The SNAP-tag is derived from the human DNA repair protein O6- alkylguanine-DNA alkyltransferase (AGT) and can be covalently labeled in living cells using O6-benzylguanine derivatives bearing a chemical probe. Here we report the generation of an AGT-based tag, named CLIP-tag, which reacts specifically with O2-benzylcytosine derivatives. Because SNAP-tag and CLIP-tag possess orthogonal substrate specificities, SNAP and CLIP fusion proteins can be labeled simultaneously and specifically with different molecular probes in living cells. We furthermore show simultaneous pulse-chase experiments to visualize different generations of two different proteins in one sample