Di- and triguanidinylation of trehalose, sucrose, and melizitose has been achieved via a Huisgen-cycloaddition approach. They can serve as aminoglycoside–arginine conjugate mimics, which has been demonstrated by their biological profiles in assays against Bacillus subtilis. For comparative studies, tetraguanidinylated neamine and kanamycin derivatives have also been synthesized and evaluated

Multidimensional high-performance liquid chromatography (HPLC) is a key method in shotgun proteomics approaches for analyzing highly complex protein mixtures by complementary chromatographic separation principles. Here, we describe an integrated 3D-nano-HPLC/nano-electrospray ionization quadrupole time-of-flight mass spectrometry system that allows an enzymatic digestion of proteins followed by an enrichment and subsequent separation of the created peptide mixtures. The online 3D-nano-HPLC system is composed of a monolithic trypsin reactor in the first dimension, a monolithic affinity column with immobilized monomeric avidin in the second dimension, and a reversed phase C18 HPLC-Chip in the third dimension that is coupled to a nano-ESI-Q-TOF mass spectrometer. The 3D-LC/MS setup is exemplified for the identification of biotinylated proteins from a simple protein mixture. Additionally, we describe an online 2D-nano-HPLC/nano-ESI-LTQ-Orbitrap-MS/MS setup for the enrichment, separation, and identification of cross-linked, biotinylated species from chemical cross-linking of cytochrome c and a calmodulin/peptide complex using a novel trifunctional cross-linker with two amine-reactive groups and a biotin label.

Multicomponent reactions (MCRs) are by far the most successful class of reactions leading to high structural diversity and molecular complexity through a single transformation. As part of the ongoing search for pharmacologically active lead structures, the obtained structural diversity allows for the fast exploration of a large chemical space. Not surprisingly, the development of MCRs, leading to new structural frameworks or serving as key transformations in the total synthesis of natural products, has expanded rapidly over the last few decades. To date a multitude of new three- and four-component reactions have already been described; however, examples of “higher-order” MCRs where five or even more components are combined in a single reaction vessel are remarkably scarce. This tutorial review aims to critically describe the developments achieved in recent years, charting the ideas, challenges, and milestone reactions that were essential for the progress of this field.

Protein profiling probes are important tools for studying the composition of the proteome and as such have contributed greatly to the understanding of various complex biological processes in higher organisms. For this purpose the application of fluorescently labeled activity or affinity probes is highly desirable. Especially for in vivodetection of low abundant target proteins, otherwise difficult to analyse by standard blotting techniques, fluorescently labeled profiling probes are of high value. Here, a one-pot protocol for the synthesis of activated fluorescent labels (i.e.azide, alkynyl or NHS), based on the Ugi-4-component reaction (Ugi-4CR), is presented. As a result of the peptoidic structure formed, the fluorescent properties of the products are pH insensitive. Moreover, the applicability of these probes, as exemplified by the labeling of model protein BSA, will be discussed.

Durch Reaktion primärer Amine mit funktionalisierten α,α‐Dichlortosylhydrazonen unter milden Bedingungen gelingt eine „spurlose“ Tosylhydrazon‐basierte Triazolsynthese, die ausschließlich zur Bildung 1,4‐substituierter Triazol‐„Klick‐Produkte“ unter vollständigem Konfigurationserhalt am Stereozentrum führt. Primäre Amine, die in vielen Naturstoffen vorkommen, können chemoselektiv ohne die Notwendigkeit einer umfassenden Schutzgruppenstrategie modifiziert werden.

Triple‐T trick! Traceless tosylhydrazone‐based triazole formation is readily achieved by reacting primary amines with functional α,α‐dichlorotosylhydrozones under ambient conditions. This fast and efficient alternative affords exclusively 1,4‐substituted triazole “click products” with complete retention of configuration. Primary amines, inherent to many natural products, can be modified in this way without protecting group manipulations.

Photoaffinity tags can be incorporated easily into peptoids and congeners by the Ugi and Passerini multicomponent reactions. Products related to photo-methionine and photo-leucine can be accomplished by diazirine-containing building blocks. The same protocols can be used to synthesize derivatives with benzophenone photo cross-linkers.

A seven-component reaction was accomplished by utilizing the different chemoselectivities of the Ugi–Mumm and the Ugi–Smiles reaction. The sequential multicomponent reactions led to highly diverse peptide and glycopeptide like structures.