Read by QxMD icon Read

Acid ring closure

Nastaran Salehi Marzijarani, Roozbeh Yousefi, Arvind Jaganathan, Kumar Dilip Ashtekar, James E Jackson, Babak Borhan
Though (DHQD)2 PHAL-catalyzed chlorocyclizations of 1,1-disubstituted olefins show useful (and in some cases, reversible) asymmetric induction, stereochemically complete descriptions of these alkene additions have remained largely unknown. Herein, based on a combination of NMR, derivative, isotope labeling, and computational studies, we present detailed stereochemical analyses of chlorocyclizations of nucleophile-tethered 1,1-disubstituted styryl systems. The selectivities of the two asymmetric bond-forming processes, namely electrophilic chlorine attack and nucleophilic ring closure, are thus mapped out independently...
March 21, 2018: Chemical Science
C Koutserimpas, A Ioannidis, M Demonakou, P Siaperas, A Skarpas, G Velimezis, I Karanikas
Malakoplakia is a rare inflammatory disease, most commonly found in the urinary tract. It appears be related to a functional deficiency of macrophages, resulting in an inability to destroy digested bacteria and it is associated with various conditions that cause immunodeficiency. A rare case of malakoplakia of the colon in a healthy 68-year old male is presented. The patient underwent emergency surgery with colon resection and an end stoma with closure of the distal bowel (Hartmann's procedure), due to incarcerated ventral hernia and sigmoid-colon rupture...
March 2018: Il Giornale di Chirurgia
Francisco Martínez-Peña, Sonia Infante-Tadeo, Abraha Habtemariam, Ana M Pizarro
Five complexes of formula [Ru(η6 -C6 H5 CH2 COOH)(XY)Cl]Cl/Na (XY = ethylenediamine (1), o-phenylenediamine (2), phenanthroline (3), and oxalato (4)) and [Ru(η6 :κ1 -C6 H5 CH2 COO)(tmen)]Cl (tmen = N, N, N', N'-tetramethylethylenediamine, 5C) have been synthesized and fully characterized. Five new X-ray crystal structures ([Ru(η6 -C6 H5 CH2 COOH)(μ-Cl)Cl]2 , 1, 3, 4, and 5C·PF6 ) have been determined, which are the first examples of ruthenium(II) structures with phenylacetic acid as arene ligand. Furthermore, 5C·PF6 is the first example of a five-membered tether ring with a Ru(η6 :κ1 -arene:O) bond...
April 24, 2018: Inorganic Chemistry
Majid M Heravi, Vahideh Zadsirjan, Masumeh Malmir
Tetrahydroisoquinolines are the framework of numerous natural products predominantly alkaloids, an important and one of the most wide spread families of naturally occurring compounds in the plant kingdom. Tetrahydroisoquinolines are commonly constructed through an old reaction, the so-called Pictet–Spengler Reaction (PSR). In this reaction, a β-aryl ethylamine undergoes an acid mediated condensation with a suitable aldehyde or ketone, followed by ring closure. In this review, we aim to highlight the applications of the asymmetric variant of this old name reaction in the total synthesis of natural products, chiefly, alkaloids, which exhibit significant biological properties...
April 18, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Poramate Songthammawat, Sirilak Wangngae, Koki Matsumoto, Chuthamat Duangkamol, Somsak Ruchirawat, Poonsakdi Ploypradith
The cyclohexene moiety of the tricyclic 6,7-diaryl-tetrahydro-6H-benzo[c]chromene core of palodesangrens could be assembled in a biomimetic and step-economical fashion by the Diels-Alder reaction between the electron-rich (E)-1,3-butadienylarenes as the diene and the electron-deficient chalcones as the dienophile. During the reduction of ketone to the corresponding alcohol by LiAlH4, the mixture of endo and exo isomers underwent a novel diastereoconvergent LiAlH4-mediated isomerization to install the desired stereochemistry at C10a...
April 16, 2018: Journal of Organic Chemistry
Og-Geum Woo, Soon-Hee Kim, Seok Keun Cho, Sang-Hoon Kim, Han Nim Lee, Taijoon Chung, Seong Wook Yang, Jae-Hoon Lee
BPH1 acts as a substrate receptor of CRL3 complex and negatively regulates ABA-mediated cellular responses. The study on its function provides information that helps further understand the relationship between ABA signaling and UPS. Abscisic acid (ABA) plays a crucial role in a variety of cellular processes, including seed dormancy, inhibition of seedling growth, and drought resistance in plants. Cullin3-RING E3 ligase (CRL3) complex is a type of multi-subunit E3 ligase, and BTB/POZ protein, a component of CRL3 complex, functions as a receptor to determine a specific substrate...
March 21, 2018: Plant Molecular Biology
Johannes Gurke, Šimon Budzák, Bernd M Schmidt, Denis Jacquemin, Stefan Hecht
Photoswitchable acid-base pairs, whose pKa values can be reversibly altered, are attractive molecular tools to control chemical and biological processes with light. A significant, light-induced pKa change of three units in aqueous medium has been realized for two thermally stable states, which can be interconverted using UV and green light. The light-induced pKa modulation is based on incorporating a 3-H-thiazol-2-one moiety into the framework of a diarylethene photoswitch, which loses the heteroaromatic stabilization of the negatively charged conjugate base upon photochemical ring closure, and hence becomes significantly less acidic...
April 16, 2018: Angewandte Chemie
Yong Chan Park, Sandeep Chapagain, Cheol Seong Jang
RING (Really Interesting New Gene) finger proteins play crucial roles in abiotic stress responses in plants. We report the RING finger E3 ligase gene, an Oryza sativa salt, ABA and drought stress-induced RING finger protein 1 gene (OsSADR1). We demonstrated that although OsSAR1 possesses E3 ligase activity, a single amino acid substitution (OsSADR1C168A) in the RING domain resulted in no E3 ligase activity, suggesting that the activity of most E3s is specified by the RING domain. Additional assays substantiated that OsSADR1 interacts with three substrates-no E3 ligase acti and OsPIRIN, and mediates their proteolysis via the 26S proteasome pathway...
March 1, 2018: Plant & Cell Physiology
Tímea Gonda, Péter Bérdi, István Zupkó, Ferenc Fülöp, Zsolt Szakonyi
Stereoselective synthesis of monoterpene-based 1,2,4- and 1,3,4-oxadiazole derivatives was accomplished starting from α,β-unsaturated carboxylic acids, obtained by the oxidation of (-)-2-carene-3-aldehyde and commercially available (-)-myrtenal. 1,2,4-Oxadiazoles were prepared in two steps via the corresponding O -acylamidoxime intermediates, which then underwent cyclisation induced by tetrabutylammonium fluoride (TBAF) under mild reaction conditions. Stereoselective dihydroxylation in highly stereospecific reactions with the OsO₄/NMO ( N -methylmorpholine N -oxide) system produced α,β-dihydroxy 1,2,4-oxadiazoles...
December 28, 2017: International Journal of Molecular Sciences
Daniel Polyak, Ngan Phung, Jian Liu, Robert Barrows, Thomas J Emge, Spencer Knapp
Homophthalic anhydride (HPA) typically reacts rapidly with benzalimines to afford the formal [4+2] adduct, a 1,2,3,4-tetrahydroisoquinolin-1-one-4-carboxylic acid. The stereochemical outcome of this reaction is consistent with an open transition state comprising an iminium species and enolized HPA, leading to a short-lived amino-anhydride intermediate. In the case of N - tert -butylbenzalimine, this Mannich-type intermediate, which would normally cyclize at low temperature to a single isomer of the delta -lactam, is intercepted by base treatment to afford beta -lactam products...
October 4, 2017: Tetrahedron Letters
Elham Jafari, Najmeh Taghi Jarah-Najafabadi, Ali Jahanian-Najafabadi, Safoora Poorirani, Farshid Hassanzadeh, Sedighe Sadeghian-Rizi
Cyclic imides are a group of compounds which have valuable biological properties including cytotoxic, anti-inflammatory, antibacterial and antifungal activities. In this study, succinic and phthalic anhydrides were treated with glycinamide in pyridine to yield the corresponding amic acids. These amic acids underwent ring closure with acetic anhydride and anhydrous sodium acetate to form cyclic imides. In another procedure, succinic and phthalic anhydrides upon reaction with 2-amino-benzylamine in pyridine gave the corresponding cyclic imides...
December 2017: Research in Pharmaceutical Sciences
Marco Mottinelli, Mathew P Leese, Barry V L Potter
Background: 1,2,3,4-Tetrahydroisoquinolines (THIQs) are common motifs in alkaloids and in medicinal chemistry. Synthetic access to THIQs via the Pomeranz-Fritsch-Bobbit (PFB) methodology using mineral acids for deactivated, electron-poor aromatic systems, is scarcely represented in the literature. Here, the factors controlling the regiochemical outcome of cyclization are evaluated. Results: A double reductive alkylation was telescoped into a one-pot reaction delivering good to excellent yields of desired aminoacetals for cyclization...
2017: Beilstein Journal of Organic Chemistry
S Mirabella, G Fibbi, C Matassini, C Faggi, A Goti, F Cardona
A dual synthetic strategy to afford 2-substituted trihydroxypiperidines is disclosed. The procedure involved Grignard addition either to a carbohydrate-derived aldehyde or to a nitrone derived thereof, and took advantage of an efficient ring-closure reductive amination strategy in the final cyclization step. An opposite diastereofacial preference was demonstrated in the nucleophilic attack to the two electrophiles, which would finally produce the same piperidine diastereoisomer as the major product. However, use of a suitable Lewis acid in the Grignard addition to the nitrone allowed reversing the selectivity, giving access to 2-substituted piperidines with the opposite configuration at C-2...
November 7, 2017: Organic & Biomolecular Chemistry
Rezvan Rezaee Nasab, Farshid Hassanzadeh, Ghadam Ali Khodarahmi, Mahboubeh Rostami, Mahmoud Mirzaei, Ali Jahanian-Najafabadi, Mahboubeh Mansourian
A series of novel 4-anilinoquinazoline derivatives were designed and synthesized from benzoic acid through ring closure, chlorination or nucleophilic substitution. The structures of compounds were characterized by IR, (1)H-NMR and mass spectroscopy. All synthesized derivatives were screened for their antimicrobial activities against Gram-positive (Staphylococcus aurous, Bacillus subtilis, Listeria monocitogenes) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa, Salmonella entritidis) bacteria and also for antifungal activities against Candida albicans using the conventional micro dilution method...
October 2017: Research in Pharmaceutical Sciences
Furong Lin, Yunjun Shen, Yuanbin Zhang, Yuji Sun, Jiyong Liu, Simon Duttwyler
An iridium-catalyzed alkenylation/annulation sequence between monocarba-closo-dodecaborate carboxylic acids and diarylacetylenes is reported. Regioselective activation of the B2 position, followed by B-C bond formation and ring closure, affords 3D bora-analogues of isocoumarins. The reaction tolerates a variety of functional groups on the aromatic rings and can be extended to B12-substituted derivatives. Furthermore, subsequent alkenylation of the B4 vertex has been achieved in high yields.
January 12, 2018: Chemistry: a European Journal
Hui-Hong Wang, Tao Shi, Wei-Wei Gao, Hong-Hua Zhang, Yong-Qiang Wang, Jun-Fang Li, Yong-Sheng Hou, Jin-Hong Chen, Xue Peng, Zhen Wang
A simple and practical ring-closure procedure to prepare a range of diverse heterocycles has been developed. In this transformation, a variety of substituted (thio)salicylamides and thiosalicylic acids undergo a double 1,4-addition reaction with propiolate derivatives in the presence of an inorganic base (K3 PO4 ), as a result benzothiazinones, benzoxazinones and benzoxathiinones were prepared in good to excellent yields, respectively, even in gram scales. In addition, further transformation towards more complex structures and oxicam drug analogues has also been successfully carried out...
October 4, 2017: Organic & Biomolecular Chemistry
Wataru Matsuoka, Hideto Ito, Kenichiro Itami
Efficient and rapid access to nanographenes and π-extended fused heteroaromatics is important in materials science. Herein, we report a palladium-catalyzed efficient one-step annulative π-extension (APEX) reaction of polycyclic aromatic hydrocarbons (PAHs) and heteroaromatics, producing various π-extended aromatics. In the presence of a cationic Pd complex, triflic acid, silver pivalate, and diiodobiaryls, diverse unfunctionalized PAHs and heteroaromatics were directly transformed into larger PAHs, nanographenes, and π-extended fused heteroaromatics in a single step...
August 11, 2017: Angewandte Chemie
Junya Suzuki, Natsumi Miyano, Shunpei Yashiro, Taiki Umezawa, Fuyuhiko Matsuda
A 3,4-disubstituted pyrrolidine ring was effectively cyclized through SmI2 -mediated reductive coupling between allyl chloride and an α,β-unsaturated ester, although little has been reported about SmI2 -promoted C-C bond formation of an allyl chloride with an α,β-unsaturated ester. Selection of either the 3,4-cis- or 3,4-trans-selective cyclization can be accomplished simply by changing the additives from NiI2 to HMPA during reductive cyclization conducted in H2 O-THF. Total synthesis of (-)-kainic acid and (+)-allo-kainic acid, which are pyrrolidine alkaloids used in neuroscience and neuropharmacology as useful molecular probes, was successfully achieved by using the stereo-complementary ring closure reactions promoted by SmI2 for the construction of the 2,3,4-trisubsituted pyrrolidine scaffold of kainoids...
August 9, 2017: Organic & Biomolecular Chemistry
Francisco Martínez-Peña, Ana M Pizarro
The potential use of organoruthenium complexes as anticancer drugs is well known. Herein, a family of activatable tethered ruthenium(II) arene complexes of general formula [Ru{η6 :κ1 -C6 H5 (C6 H4 )NH2 }(XY)]n+ (closed tether ring) bearing different chelating XY ligands (XY=aliphatic diamine, phenylenediamine, oxalato, bis(phosphino)ethane) is reported. The activation of these complexes (closed- to open-tether conversion) occurs in methanol and DMSO at different rates and to different reaction extents at equilibrium...
November 16, 2017: Chemistry: a European Journal
Ruixiao Gao, Deyaa I AbuSalim, Timothy D Lash
The first examples of porphyrin analogues incorporating pyrene units are reported. Acid-catalyzed condensation of a pyrene dialdehyde with a tripyrrane, followed by oxidation with DDQ, afforded a polycyclic aromatic hydrocarbon (PAH)-porphyrin hybrid in 38% yield. Pyreniporphyrin proved to be devoid of global aromatic character, but upon protonation aromatic mono- and dicationic species were generated. In the proton NMR spectrum for the dication, the internal CH was shifted upfield to approximately +3 ppm. NICS calculations and ACID plots confirmed the diatropic nature of these structures...
June 15, 2017: Journal of Organic Chemistry
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"