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Organic & Biomolecular Chemistry

Brandon R Smith, Jon T Njardarson
Synthetic approaches toward the complex natural product diterpenoid maoecrystal V are reviewed, including successful total syntheses, published synthetic efforts, and efforts compiled from dissertations. The review focuses on general synthetic strategies and chronicles efforts toward the molecule since its isolation in 2004, summarizing key contributions of these efforts to the broader synthetic community.
May 18, 2018: Organic & Biomolecular Chemistry
Abdullah Alzahrani, Styliana I Mirallai, Benjamin A Chalmers, Patrick McArdle, Fawaz Aldabbagh
The traditional thermal Mannich reaction is unsuitable for preparing polymerizable N-methylene amino substituted acrylamides and methacrylamides. Herein we provide a facile multi-gram high yield synthesis of these monomeric precursors to stimuli-responsive polymers by the addition of acrylamides and methacrylamides onto in situ generated or freshly isolated methylene Schiff base (iminium) salts. The X-ray crystal structure of the hydrated iminium salt, 1-(hydroxymethyl)azocan-1-ium chloride and monomer·HCl salt (N-[(azocan-1-yl)methyl]prop-2-enamide hydrochloride) is described...
May 18, 2018: Organic & Biomolecular Chemistry
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May 18, 2018: Organic & Biomolecular Chemistry
Yao Peng, Jian Lei, Renhua Qiu, Lingteng Peng, Chak-Tong Au, Shuang-Feng Yin
A protocol for the chelation-assisted C-N cross-coupling of phosphinamides and aryl boronic acids with copper powder under an oxygen atmosphere is reported. This reaction proceeds efficiently to afford fully substituted unsymmetrical N-arylation phosphinamides at room temperature in excellent yields. Diverse unstable functional groups on the benzene ring of aryl boronic acids such as vinyl, formyl, acetyl, sulfonyl, acetylamino, cyano, nitro, and trifluoromethyl can be accommodated.
May 18, 2018: Organic & Biomolecular Chemistry
Man-Yi Han, Hong Pan, Jing Lin, Wei Li, Pinhua Li, Lei Wang
A catalyst-controlled switchable reaction of β-keto acids to silyl glyoxylates was developed under mild conditions, providing two distinct products in good yields. Compared to decarboxylative addition-Brook rearrangement, the decarboxylative addition products could be controlled by using a simple bifunctional organocatalyst thiourea derivative instead of DABCO. This new reaction model of silyl glyoxylates offered a facile and alternative route to organosilicon compounds.
May 18, 2018: Organic & Biomolecular Chemistry
Takayoshi Awakawa, Ikuro Abe
Teleocidin B is a terpenoid indole alkaloid with unique structures including indolactam and cyclic terpenoid, and is a strong protein kinase C activator. Its unique structure and bioactivity have drawn vast interest from chemists and biologists, and numerous isolation and bioactivity studies on this molecule have been performed. Recently, its biosynthetic enzymes were identified, and some of their crystal structures were reported. In this review, we describe the isolation of teleocidin derivatives, biosynthetic studies, and detailed analyses of biosynthetic enzymes, to clarify their biosynthetic reactions toward the enzymatic synthesis of bioactive teleocidin compounds...
May 18, 2018: Organic & Biomolecular Chemistry
Fabien Thoreau, Laetitia Vanwonterghem, Maxime Henry, Jean-Luc Coll, Didier Boturyn
Targeting the tumour microenvironment is a promising strategy to detect and/or treat cancer. The design of selective compounds that co-target several receptors frequently overexpressed in solid tumours may allow a reliable and selective detection of tumours. Here we report the modular synthesis of compounds encompassing ligands of αVβ3 integrin and neuropilin-1 that are overexpressed in the tumour microenvironment. These compounds were then evaluated through cellular experiments and imaging of tumours in mice...
May 18, 2018: Organic & Biomolecular Chemistry
S Shishodia, D Zhang, A H El-Sagheer, T Brown, T D W Claridge, C J Schofield, R J Hopkinson
Formaldehyde is produced in cells by enzyme-catalysed demethylation reactions, including those occurring on N-methylated nucleic acids. Formaldehyde reacts with nucleobases to form N-hydroxymethylated adducts that may contribute to its toxicity/carcinogenicity when added exogenously, but the chemistry of these reactions has been incompletely defined. We report NMR studies on the reactions of formaldehyde with canonical/modified nucleobases. The results reveal that hydroxymethyl hemiaminals on endocyclic nitrogens, as observed with thymidine and uridine monophosphates, are faster to form than equivalent hemiaminals on exocyclic nitrogens; however, the exocyclic adducts, as formed with adenine, guanine and cytosine, are more stable in solution...
May 16, 2018: Organic & Biomolecular Chemistry
Akinari Sumita, Jinhee Lee, Yuko Otani, Tomohiko Ohwada
Here, we report new methodology for synthesizing 2,3-benzodiazepines and their analogues by means of phosphate-assisted acylation reaction of 1-arylpropan-2-ones with a carboxylic acid followed by hydrazine cyclization in a one-pot two-step manner. An unprotected amino group is tolerated in this reaction. This method provides a direct access to 2,3-benzodiazepines containing aromatic 7,8-dimethoxy and 1-p-aminophenyl groups, which are generally considered important for bioactivity. The presence of 3,4-dimethoxy or 3-methoxy substitution on the benzene ring of the 1-arylpropan-2-one is important for high regioselectivity in the acylation reaction...
May 16, 2018: Organic & Biomolecular Chemistry
Wenzeng Duan, Qingsong Liu, Yanmin Huo, Jichun Cui, Shuwen Gong, Zhipeng Liu
A new family of aggregation-induced emission (AIE)-active monoboron and bisboron complexes based on benzothiazole-hydrazone chelates was synthesized. These complexes showed very weak fluorescence in fluid solution due to active intramolecular rotation and were emissive in high-viscosity solvents or in the aggregation state. Single crystal X-ray diffraction analyses and theoretical calculations were carried out to explain AIE behavior. The large Stokes shifts (3590-7400 cm-1) and relatively highly efficient solid-state emission make these complexes valuable AIE luminophores for further potential applications...
May 16, 2018: Organic & Biomolecular Chemistry
Emilio Lence, Marc W van der Kamp, Concepción González-Bello, Adrian J Mulholland
Type II dehydroquinase enzymes (DHQ2), recognized targets for antibiotic drug discovery, show significantly different activities dependent on the species: DHQ2 from Mycobacterium tuberculosis (MtDHQ2) and Helicobacter pylori (HpDHQ2) show a 50-fold difference in catalytic efficiency. Revealing the determinants of this activity difference is important for our understanding of biological catalysis and further offers the potential to contribute to tailoring specificity in drug design. Molecular dynamics simulations using a quantum mechanics/molecular mechanics potential, with correlated ab initio single point corrections, identify and quantify the subtle determinants of the experimentally observed difference in efficiency...
May 16, 2018: Organic & Biomolecular Chemistry
Zheng Wang, Ming-Hua Xu
By employing an easily available, exceptionally simple sulfur-olefin ligand, a highly enantioselective rhodium-catalyzed arylation of cyclic N-sulfonyl α-ketimino esters with arylboronic acids has been developed. The reaction allows facile access to a wide range of α,α-gem-diaryl substituted chiral amino esters in excellent yields with extremely high enantioselectivities (uniformly 98-99% ee). The synthetic utility of this approach was highlighted by the efficient synthesis of a series of interesting molecules including unique chiral spirocycles bearing 2,3-dihydrobenzofuran and 1H-isoindole skeletons...
May 16, 2018: Organic & Biomolecular Chemistry
Nivedita S Mahajani, John D Chisholm
1,1'-Diarylbutyl groups are a common pharmacophore found in many biologically active small molecules. To access these systems under mild conditions, the reaction of diarylmethyl trichloroacetimidates with allyltributylstannanes was explored. Simply heating allyltributylstannane with the trichloroacetimidate resulted in substitution of the imidate with an allyl group. Unlike other methods used to access these systems, no strong base, transition metal catalyst, Brønsted acid or Lewis acid promoter was required to affect the transformation...
May 16, 2018: Organic & Biomolecular Chemistry
Wenzheng Zhang, Guangyang Xu, Lin Qiu, Jiangtao Sun
A novel protocol for the synthesis of C5-alkylated indole derivatives via a gold-catalyzed reaction of indolines with diazo compounds and subsequent oxidative aromatization has been developed. C-H bond functionalization selectively occurs at the C5-position of indolines without a directing group. The experimental operation is simple and the whole process can be manipulated in one-pot.
May 16, 2018: Organic & Biomolecular Chemistry
Hongwei Sun, Shi Tang, Dengke Li, Yali Zhou, Jinbo Huang, Qiang Zhu
A palladium-catalyzed double isocyanide insertion using 2-iodo-2'-isocyano-1,1'-biphenyls followed by copper-catalyzed intramolecular C-N coupling, delivering a unique heterocyclic structure containing both phenanthridine and carbazole scaffolds, has been developed. In this cascade process, four chemical bonds, including two C-C, one C-O, and one C-N bonds are formed consecutively without isolating an intermediate. The strategy of using a functionalized isocyanide in double insertion provides a quick approach for constructing heterocyclic systems with high bond-forming efficiency...
May 16, 2018: Organic & Biomolecular Chemistry
Takuya Sakai, Takuma Kumoi, Tatsuro Ishikawa, Takahiro Nitta, Hiroki Iida
A series of flavinium salts, 5-ethylisoalloxazinium, 5-ethylalloxazinium, and 1,10-ethylene-bridged alloxazinium triflates, were prepared from commercially available riboflavin. This study presents a comparison between their optical and redox properties, and their catalytic activity in H2O2 oxidations of sulfide, tertiary amine, and cyclobutanone. Reflecting the difference between the π-conjugated ring structures, the flavinium salts displayed very different redox properties, with reduction potentials in the order of: 5-ethylisoalloxazinium > 5-ethylalloxazinium > 1,10-ethylene-bridged alloxazinium...
May 16, 2018: Organic & Biomolecular Chemistry
Olga Bakulina, Dmitry Dar'in, Mikhail Krasavin
The first example of employing a mixed carboxylic-sulfonic anhydride in reaction with imines is reported. Unlike its well-studied isostere homophthalic anhydride, benzo[c][1,2]oxathiin-3(4H)-one 1,1-dioxide gave no product of a formal [4 + 2] cycloaddition and only followed an alternative reaction pathway toward β-lactams, presumably, via a formal [2 + 2] cycloaddition (a Staudinger-type reaction). Optimized reaction conditions involve the use of triethylamine as a base promoter, which also allows isolating the product β-lactam benzene sulfonic acids as respective triethylammonium salts by conventional column chromatography...
May 16, 2018: Organic & Biomolecular Chemistry
Muhammad Jbara, Emad Eid, Ashraf Brik
An efficient native chemical ligation approach at Asp and Glu sites is reported applying a hydrazide precursor, as a peptide thioester, and allyl protection at the side chain of Asp and Glu. The allyl protection was efficiently removed, after the ligation step, using the water-soluble palladium complex [Pd(allyl)Cl]2 and glutathione within a few minutes under fully aqueous conditions.
May 16, 2018: Organic & Biomolecular Chemistry
Verena Klaus, Stéphane Wittmann, Hans M Senn, J Stephen Clark
A novel method for the stereoselective construction of hexahydroazuleno[4,5-b]furans from simple precursors has been developed. The route involves the use of our recently developed Brønsted acid catalysed cyclisation reaction of acyclic ynenones to prepare fused 1-furanyl-2-alkenylcyclopropanes that undergo highly stereoselective thermal Cope rearrangement to produce fused tricyclic products. Substrates possessing an E-alkene undergo smooth Cope rearrangement at 40 °C, whereas the corresponding Z-isomers do not react at this temperature...
May 15, 2018: Organic & Biomolecular Chemistry
Wei-Zhi Weng, Jian Xie, Bo Zhang
A simple and efficient approach for the preparation of substituted indoles and isoquinolones via a nickel-catalyzed Larock-type heteroannulation reaction is reported. This transformation employed air-stable and inexpensive Ni(dppp)Cl2 as a precatalyst and Et3N as a mild base. Moreover, the reaction occurs efficiently under mild conditions, and a wide range of substituted indoles and isoquinolones bearing various functional groups are obtained in moderate to excellent yields.
May 15, 2018: Organic & Biomolecular Chemistry
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