Project description:A highly efficient and step-economical synthesis of zincophorin methyl ester has been achieved. The unprecedented step economy of this zincophorin synthesis is principally due to an application of the tandem silylformylation-crotylsilylation/Tamao oxidation-diastereoselective tautomerization reaction, which achieves in a single step what would typically require a significant multistep sequence.
Project description:In microbiome research, phylogenetic and functional marker gene amplicon sequencing is the most commonly-used community profiling approach. Consequently, a plethora of protocols for the preparation and multiplexing of samples for amplicon sequencing have been developed. Here, we present two economical high-throughput gene amplification and sequencing workflows that are implemented as standard operating procedures at the Joint Microbiome Facility of the Medical University of Vienna and the University of Vienna. These workflows are based on a previously-published two-step PCR approach, but have been updated to either increase the accuracy of results, or alternatively to achieve orders of magnitude higher numbers of samples to be multiplexed in a single sequencing run. The high-accuracy workflow relies on unique dual sample barcoding. It allows the same level of sample multiplexing as the previously-published two-step PCR approach, but effectively eliminates residual read missasignments between samples (crosstalk) which are inherent to single barcoding approaches. The high-multiplexing workflow is based on combinatorial dual sample barcoding, which theoretically allows for multiplexing up to 299,756 amplicon libraries of the same target gene in a single massively-parallelized amplicon sequencing run. Both workflows presented here are highly economical, easy to implement, and can, without significant modifications or cost, be applied to any target gene of interest.
Project description:The application of sequence-defined macromolecules in material science remains largely unexplored due to their challenging, low yielding and time-consuming synthesis. This work first describes a step-economical method for synthesizing unnatural sequence-defined oligoamides through fluorenylmethyloxycarbonyl chemistry. The use of a monodisperse soluble support enables homogeneous reactions at elevated temperature (up to 65 °C), leading to rapid coupling times (<10 min) and improved synthesis protocols. Moreover, a one-pot procedure for the two involved iterative steps is demonstrated via an intermediate quenching step, eliminating the need for in-between purification. The protocol is optimized using γ-aminobutyric acid (GABA) as initial amino acid, and the unique ability of the resulting oligomers to depolymerize, with the formation of cyclic γ-butyrolactame, is evidenced. Furthermore, in order to demonstrate the versatility of the present protocol, a library of 17 unnatural amino acid monomers is synthesized, starting from the readily available GABA-derivative 4-amino-2-hydroxybutanoic acid, and then used to create multifunctional tetramers. Notably, the obtained tetramers show higher thermal stability than a similar thiolactone-based sequence-defined macromolecule, which enables its exploration within a material context. To that end, a bidirectional growth approach is proposed as a greener alternative that reduces the number of synthetic steps to obtain telechelic sequence-defined oligoamides. The latter are finally used as macromers for the preparation of polymer networks. We expect this strategy to pave the way for the further exploration of sequence-defined macromolecules in material science.
Project description:Total syntheses of (-)-dictyostatin, 6,16-bis-epi-dictyostatin, 6,14,19-tris-epi-dictyostatin and a number of other isomers and analogs are reported. Three main fragments-top, middle and bottom-were first assembled and then joined by olefination or anionic addition reactions. After appending the two dienes at either end of the molecule, macrolactonization and deprotection completed the syntheses. The work proves both the relative and absolute configurations of (-)-dictyostatin. The compounds were evaluated by cell-based measurements of increased microtubule mass and antiproliferative activity, and in vitro tubulin polymerization assays as well as competitive assays with paclitaxel for its binding site on microtubules. These assays showed dictyostatin to be the most potent of the agents and further showed that the structural alterations caused from 20- to >1000-fold decreases in activity.
Project description:An efficient, step-economical, and scalable synthesis of a diene-bearing AB spiroketal fragment of spongistatin 1, and a demonstration of its efficient coupling to an aldehyde derived from silylformylation of a homopropargyl alcohol to produce the entire complex C(13)-C(17) linker region are described. The scalability of the synthesis of the AB spiroketal fragment was demonstrated by the preparation of 34.5 grams by one chemist in ~60 workdays, and more than 40 grams overall. With this material in hand and having established a method for its efficient coupling to the CD fragment, we have set the stage for the rapid synthesis and evaluation of a series of analogs of the CD spiroketal.
Project description:The bottom-up design and construction of functional metalloproteins remains a formidable task in biomolecular design. Although numerous strategies have been used to create new metalloproteins, pre-existing knowledge of the tertiary and quaternary protein structure is often required to generate suitable platforms for robust metal coordination and activity. Here we report an alternative and easily implemented approach (metal active sites by covalent tethering or MASCoT) in which folded protein building blocks are linked by a single disulfide bond to create diverse metal coordination environments within evolutionarily naive protein-protein interfaces. Metalloproteins generated using this strategy uniformly bind a wide array of first-row transition metal ions (MnII, FeII, CoII, NiII, CuII, ZnII and vanadyl) with physiologically relevant thermodynamic affinities (dissociation constants ranging from 700 nM for MnII to 50 fM for CuII). MASCoT readily affords coordinatively unsaturated metal centres-including a penta-His-coordinated non-haem Fe site-and well-defined binding pockets that can accommodate modifications and enable coordination of exogenous ligands such as nitric oxide to the interfacial metal centre.
Project description:A Na2HPO4-catalyzed four-component reaction between a ketone, malononitrile, S8 and formamide has been realized for the first time. This reaction provides a concise approach to thieno[2,3-d]pyrimidin-4-amines, previously requiring 5 steps. The utility of this reaction was validated by preparing a multi-targeted kinase inhibitor and an inhibitor of the NRF2 pathway with excellent atom- and step-economy.
Project description:The synthesis of highly diverse libraries has become of paramount importance for obtaining novel leads for drug and agrochemical discovery. Herein, the step-economical diversity-oriented synthesis of a library of various pyrimidine-N-heterocycle hybrids was developed, in which a 4,6-dimethoxypyrimidine core was incorporated into nine kinds of N-heterocycles. A total of 34 structurally diverse compounds were synthesized via a two-step process from very simple and commercially available starting materials. Further, in vivo biological screening of this library identified 11 active compounds that exhibited good post-emergence herbicidal activity against D. sanguinalis at 750 g ai per ha. More importantly, pyrimidine-tetrahydrocarbazole hybrid 5q showed good to excellent herbicidal activity against five test weeds at the same dosage. Pyrimidine-tetrahydrocarbazole hybrids represent a novel class of herbicidal agents that may become promising lead compounds in the herbicidal discovery process.
Project description:Quaternary benzylic centers are accessed with high atom and step economy by Ir-catalyzed alkene hydroarylation. These studies provide unique examples of the use of non-polarized 1,1-disubstituted alkenes in branch selective Murai-type hydro(hetero)arylations. Detailed mechanistic studies have been undertaken, and these indicate that the first irreversible step is the demanding alkene carbometallation process. Structure-reactivity studies show that the efficiency of this is critically dependent on key structural features of the ligand. Computational studies have been undertaken to rationalize this experimental data, showing how more sterically demanding ligands reduce the reaction barrier via predistortion of the reacting intermediate. The key insight disclosed here will underpin the ongoing development of increasingly sophisticated branch selective Murai hydroarylations.
Project description:An atom- and step-economical strategy for the synthesis of bisphosphinoylaminomethanes is reported. This metal-free bisphosphinylation reaction proceeded smoothly through a base-mediated direct 1,1-bisphosphonation of phosphine oxides and isocyanides under mild conditions. The present method offers a facile, efficient, and general approach to a broad range of bisphosphinoylaminomethane derivatives in moderate to good yields.