A5051127559- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Asymmetric Synthesis and Catalysis
- Oxidative Organic Chemistry Reactions
- Chemical synthesis and alkaloids
- Chemical Synthesis and Analysis
- Catalytic C–H Functionalization Methods
- Synthetic Organic Chemistry Methods
- Asymmetric Hydrogenation and Catalysis
- Crystallography and molecular interactions
- Vanadium and Halogenation Chemistry
- Chemical Synthesis and Reactions
- Lipid Membrane Structure and Behavior
- Marine Sponges and Natural Products
- Microbial Natural Products and Biosynthesis
- Traditional and Medicinal Uses of Annonaceae
- Synthesis and Catalytic Reactions
- Chemical Reactions and Isotopes
- Force Microscopy Techniques and Applications
- Genomics and Phylogenetic Studies
- Computational Drug Discovery Methods
- Organic Chemistry Cycloaddition Reactions
- Advanced Synthetic Organic Chemistry
- Carbohydrate Chemistry and Synthesis
- RNA and protein synthesis mechanisms
Stanford University
2015-2024
Stanford Medicine
2017-2021
Harvard University
2011-2012
Scripps Research Institute
2006-2012
Philipps University of Marburg
2009
Columbia University
2006
"Economy" is referred to as the thrifty and efficient use of material resources, principle "minimum effort reach a goal." More illuminating is: "the aim portion one's forces in order little possible them Such statements certainly apply when goal synthesize complex target molecule. Redox economy then implies few redox steps synthetic conquest compound. While any sort will help streamline total synthesis, addresses particularly weak area present-day synthesis. It not enough point out present...
Forcing polymers to be semiconductors In mechanochemistry, the application of force a polymer is used pry open specific chemical bonds. Chen et al. leveraged this technique produce semiconducting blocks polyacetylene in an insulating precursor. Ring-opening metathesis polymerization tethered together series fused four-carbon rings, reminiscent unusual ladderane membrane lipids anaerobic ammonium-oxidizing bacteria. Subsequently, sonication unzipped these strained rings into alternating C=C...
A longstanding challenge in fundamental functional group interconversion has been the direct transformation of benzene into pyridine via nitrogen insertion and carbon deletion. Herein, we report a protocol for aryl azides, easily accessible from their corresponding anilines, to 2-aminopyridines using blue light oxygen. Mechanistic studies corroborate that arene conversion is achieved by ring followed oxidative extrusion.
A new method for effecting catalytic enantioselective intramolecular [5 + 2] cycloadditions based on oxidopyrylium intermediates is reported. The dual catalyst system consists of a chiral primary aminothiourea and second achiral thiourea. Experimental evidence points to type cooperative catalysis with each species being necessary generate reactive pyrylium ion pair that undergoes subsequent cycloaddition high enantioselectivity.
Abstract Anregungen für die organische Synthese : Stufen‐ und Atomökonomie haben sich als nützliche Kriterien erwiesen, an denen Effizienz einer festmachen lässt. Dieser Aufsatz weist auf eine weitere Form der Ökonomie hin, bei Planung Bewertung mehrstufigen berücksichtigt werden sollte: Redoxökonomie. Etliche Beispiele Leitfäden vorgestellt, das Konzept illustrieren Syntheseplanung geben. magnified image “Ökonomie” bezeichnet den sparsamen effizienten Umgang mit materiellen Ressourcen,...
Herein we describe a highly chemo-, regio-, and enantioselective bromochlorination reaction of allylic alcohols, employing readily available halogen sources simple Schiff base as the chiral catalyst. The application this interhalogenation to variety substrates, rapid synthesis bromochlorinated natural product, preliminary extension chemistry dibromination dichlorination are reported.
A new dibromination reaction involving the combination of dibromomalonate as bromonium source and a titanium bromide species has been developed. Enantioselective catalysis achieved through apparent ligand acceleration by tartaric acid-derived diol.
A titanium-based catalytic enantioselective dichlorination of simple allylic alcohols is described. This reaction provides stereoselective access to all common dichloroalcohol building blocks used in syntheses chlorosulfolipid natural products. An synthesis ent-(-)-deschloromytilipin and a concise, eight-step ent-(-)-danicalipin are executed employ the as first step. Extension this system dibromination its use pentabromide stereoarrays relevant bromosulfolipids reported. The described...
Ladderane lipids produced by anammox bacteria constitute some of the most structurally fascinating yet poorly studied molecules among biological membrane lipids. Slow growth producing organism and inherent difficulty purifying complex lipid mixtures have prohibited isolation useful amounts natural ladderane We devised a highly selective total synthesis tails full phosphatidylcholine to enable biophysical studies on chemically homogeneous samples these molecules. Additionally, we report first...
Photochemical reactions are widely used by academia and industry to construct complex molecular architectures<italic>via</italic>mechanisms that often inaccessible other means.
The first total synthesis of the highly complex and potent anticancer agent haouamine A is reported through an eight-step sequence. Brevity sequence complete control chemo-, position-, stereoselectivity (both planar axial chirality) were possible invention chemistry specifically tailored for problems at hand, namely a cascade annulation proceeding via hitherto unknown chemical entity indeno-tetrahydropyridine ring system as well pyrone-assisted stitching daunting bent-aromatic ring.
A total synthesis of the complex, bent aromatic ring-containing marine alkaloid haouamine is achieved through a route in which every step (with exception final deprotection) performed on gram-scale. This accomplished development method for dehydrogenation cyclohexenones that allows point-to-planar chirality transfer. strategy makes it possible to program desired atropisomeric outcome from simple chiral cyclohexenone. By synthesizing atrop-haouamine A, this work has firmly established natural...
Ladderane lipids are unique to anaerobic ammonium-oxidizing (anammox) bacteria and enriched in the membrane of anammoxosome, an organelle thought compartmentalize anammox process, which involves toxic intermediate hydrazine (N2H4). Due slow growth rate difficulty isolating pure ladderane lipids, experimental evidence biological function ladderanes is lacking. We have synthesized two natural one unnatural phosphatidylcholine compared their thermotropic properties self-assembled bilayers...
Over 160 chiral vicinal bromochlorinated natural products have been identified; however, a lack of synthetic methods for the selective incorporation halogens into organic molecules has hindered their synthesis. Here we disclose first total synthesis and structural confirmation isoplocamenone plocamenone, as well scalable preclinical anticancer product halomon. The these inter-halogenated compounds enabled by our recently developed chemo-, regio-, enantioselective dihalogenation reaction.
A method for converting sp<sup>3</sup> C–H to C–Br bonds using an <italic>N</italic>-methyl sulfamate directing group is described. For all sulfamates examined, bromination occurs with high selectivity at the γ-carbon, affording a predictable bond halogenation.
Pursuing polymers that can transform from a nonconjugated to conjugated state under mechanical stress significantly change their properties, we developed new generation of ladder-type mechanophore monomers, bicyclo[2.2.0]hex-5-ene-peri-naphthalene (BCH-Naph), be directly and efficiently polymerized by ring-opening metathesis polymerization (ROMP). BCH-Naphs synthesized in multigram quantities functionalized with wide range electron-rich electron-poor substituents, allowing tuning the...
Herein we report a highly regio- and stereoselective haloazidation of allylic alcohols. This enantioselective reaction uses readily available materials can be performed on variety alkyl-substituted alkenes incorporate either bromine or chlorine as the electrophilic halogen component. Both halide azido groups resulting products transformed into valuable building blocks with complete stereospecificity. The first example an 1,4-haloazidation conjugated diene is reported well its application to...
Abstract Archaea possess characteristic membrane-spanning lipids that are thought to contribute the adaptation extreme environments. However, biosynthesis of these is poorly understood. Here, we identify a radical S -adenosyl-L-methionine (SAM) enzyme synthesizes glycerol monoalkyl tetraethers (GMGTs). The enzyme, which name GMGT synthase (Gms), catalyzes formation C(sp 3 )–C(sp ) linkage between two isoprenoid chains dialkyl (GDGTs). This conclusion supported by heterologous expression gene...
We have recently reported a polymechanophore system, polyladderene (PLDE), which dramatically transforms into polyacetylene (PA) upon mechanical stimulation. Herein, we optimized conditions to synthesize unprecedented block copolymers (BCPs) containing force-responsive by sequential ring-opening metathesis polymerization of different norbornenes and bromoladderene. Successful extension from PLDE other blocks required careful timing low temperatures preserve the reactivity PLDE-appended...
The Kochi–Salomon reaction is the only photochemical [2+2] cycloaddition capable of combining two electronically unactivated olefins into a cyclobutane. Yet, has remained largely unexplored and suffers many drawbacks, most notably an intolerance to Lewis/Brønsted basic amines amides. Since these groups are ubiquitous in biologically active pharmaceuticals, amine-tolerant would greatly facilitate rapid exploration novel drug scaffolds. Herein, we disclose transformation that run water with...