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Organic Letters

Yuanjin Chen, Yangyang Ma, Liangkui Li, Hao Jiang, Zhiping Li
Nitration-peroxidation of alkenes for the synthesis of β-peroxyl nitroalkanes has been developed by using tert-butyl nitrite and tert-butyl hydroperoxide. The method presents a new and selective difunctionalization of alkenes to introduce a nitro group and a peroxyl group across the double bonds of alkenes under mild conditions. A radical reaction pathway is proposed by experimental and theoretical studies.
February 13, 2019: Organic Letters
Xueling Meng, Binmiao Yang, Linxing Zhang, Guangyao Pan, Xinhao Zhang, Zhihui Shao
The first metal/organo cooperatively catalyzed asymmetric reaction of C-alkynyl N-Boc-protected N,O-acetals with in situ generated oxonium ylides has been developed. This new type of propargylation allows for the efficient synthesis of structurally diverse unreported chiral propargylamines bearing oxa-quaternary stereocenters. The reaction features unprecedented substrate scope and high diastereo- and enantioselectivity. Theoretical studies suggest a novel cooperative catalysis model and the unique transfer of R2 OH...
February 13, 2019: Organic Letters
Xu-Xin Zhu, Yao-Yue Fan, Lei Xu, Qun-Fang Liu, Jiang-Ping Wu, Jing-Ya Li, Jia Li, Kun Gao, Jian-Min Yue
Four indole alkaloids, alstonlarsines A-D (1-4), were isolated from Alstonia scholaris and structurally characterized. Compound 1 possesses a new carbon skeleton with a cage-shaped 9-azatricyclo[,8 ]decane motif, and compounds 2-4 feature a rare carbon skeleton that was found in nature for the first time. Plausible biosynthetic routes for 1-4 are proposed. Compound 1 showed DRAK2 inhibitory activity with an IC50 value of 11.65 ± 0.63 μΜ.
February 13, 2019: Organic Letters
Xiaosheng An, Qinghong Zha, Yikang Wu
Ketones, ketals, and epoxides were converted into corresponding hydroperoxides in high yields by reaction with ethereal H2 O2 in the presence of a catalytic amount of MoO2 (acac)2 with distinct (to date unattainable) chemoselectivity.
February 12, 2019: Organic Letters
Rui Guo, Xueling Mo, Guozhu Zhang
A rhodium-catalyzed tandem reaction of alkynyl cyclobutanols with salicylaldehydes has been developed. The reaction offers a new and atom-economical approach for the selective preparation of multisubstituted 2-(2-oxo-2-phenylethyl)cyclopentanone in high yields under mild reaction conditions with tolerance of a broad range of substituted alkynyl cyclobutanols and salicylaldehyes. The isolation of intermediate suggests that the reaction proceeds through a sequential process of intermolecular hydroacylation and semipinacol rearrangement...
February 12, 2019: Organic Letters
Kim N Tu, Scott Kim, Suzanne A Blum
Herein we report an aminoboration reaction that employs inexpensive, Earth-abundant, and commercially available Cu(OTf)2 as an effective catalyst in the direct addition of B-N σ bonds to C-C π bonds, generating borylated pyrazoles, which are useful building blocks for drug discovery. By nature of the mechanism, the reaction produces exclusively one regioisomer and tolerates groups incompatible with alternative lithiation/borylation and iridium-catalyzed C-H activation/borylation methods. The reaction can be scaled up, and the resulting isolable pyrazole pinacol boronates can be further functionalized through palladium-catalyzed Suzuki cross-coupling reactions...
February 12, 2019: Organic Letters
Yan Zhang, Haiqian Zhu, Yuting Huang, Qi Hu, Yu He, Yihang Wen, Gangguo Zhu
A practical one-pot isoindolinone synthesis enabled by RhIII catalysis was developed. The advantage of this protocol is that it does not require pre-preparation of amide substrates, because RhIII participates in two reactions independently. This mild, operationally multicomponent process transforms a wide variety of commercially available aldehydes into the corresponding γ-lactams in good yields, thereby demonstrating that N-pyridin-2-yl benzamide is an effective directing group. Notably, the anxiolytic drugs pagoclone and pazinaclone can be directly prepared by this methodology...
February 12, 2019: Organic Letters
Guoli Shen, Jingchao Chen, Dandan Xu, Xia Zhang, Yongyun Zhou, Baomin Fan
The asymmetric transfer hydrogenation of heterobicyclic alkenes was accomplished by using water as the sole hydrogen source. The transformation was co-catalyzed by Pd(OAc)2 /Zn(OTf)2 dual catalyst with metallic zinc as reducing agent. Various azabenzonorbornadienes and oxabenzonorbornadienes were transformed to the corresponding chiral 1,2-dihydronaphthalenes by the asymmetric reductive ring-opening reactions with good to excellent enantioselectivities.
February 12, 2019: Organic Letters
Kevin A Juárez-Ornelas, J Oscar C Jiménez-Halla, Terumasa Kato, César R Solorio-Alvarado, Keiji Maruoka
The first catalytic procedure for the electrophilic nitration of phenols was developed using iodosylbenzene as an organocatalyst based on iodine(III) and aluminum nitrate as a nitro group source. This atom-economic protocol occurs under mild, non-Brønsted acidic and open-flask reaction conditions with a broad functional-group tolerance including several heterocycles. Density functional theory (DFT) calculations at the (SMD:MeCN)Mo8-HX/(LANLo8+f,6-311+G*) level indicated that the reaction proceeds through a cationic pathway that efficiently generates the NO2 + ion, which is the nitrating species under neutral conditions...
February 12, 2019: Organic Letters
Anna Skrzyńska, Sebastian Frankowski, Marek Moczulski, Piotr Drelich, Łukasz Albrecht
A new strategy for a direct α,β,γ-functionalization of the γ-lactone framework in the corresponding 5-alkylidenefuran-2(5 H)-ones is reported. The developed approach is based on a stereocontrolled cascade reaction with 2-mercaptocarbonyl compounds proceeding in a sequence of thia-Michael/aldol/oxa-Michael reactions. Such a synthetic strategy allows for a construction of a unique polycyclic architecture containing γ-lactone, tetrahydrofuran, and tetrahydrothiophene ring systems. Excellent enantioselectivities and diastereoselectivities have been obtained in the presence of bifunctional catalyst derived from cinchona alkaloids...
February 12, 2019: Organic Letters
Changli Sun, Zhijie Yang, Chunyan Zhang, Zhiyong Liu, Jianqiao He, Qing Liu, Tianyu Zhang, Jianhua Ju, Junying Ma
Genome mining of the deep sea-derived Streptomyces atratus SCSIO ZH16 enabled the activation of a cyclodepsipeptide gene cluster and isolation of its cinnamic acid-bearing product, atratumycin (1). Atratumycin's structure was elucidated on the basis of extensive spectroscopic experiments, X-ray data, and Marfey's method; a plausible biosynthesis and tailoring modification of 1 are also proposed and investigated. Additionally, atratumycin is active against Mycobacteria tuberculosis H37Ra and H37Rv with MICs of 3...
February 12, 2019: Organic Letters
Xiaofang Lei, Yuanyuan Wang, Erkang Fan, Zhihua Sun
Activation of disulfides with N-halogen succinimide in the presence of TEMPO allows insertion reaction by an isocyanide, the product of which can further accept a wide range of nucleophiles for the generation of isothioureas and related molecular moieties. This new procedure overcomes previous methods that accept essentially only aryl amines as the third nucleophilic component. The diverse nucleophiles usable in our new protocol make this approach a general method for de novo synthesis of many S-containing heterocycles...
February 11, 2019: Organic Letters
Jingyi Zhang, Meichao Guo, Yajuan Chen, Shuangshuang Zhang, Xiao-Na Wang, Junbiao Chang
A metal-free [2 + 2 + 2] cycloaddition of alkyne-cyanamides or ynamide-nitriles with ynamides is described for the efficient synthesis of amino-substituted α- and δ-carbolines. This novel methodology is environmentally friendly and allows for highly regioselective access to carboline derivatives in good to excellent yields with wide functional group tolerance.
February 8, 2019: Organic Letters
Ronan Rocaboy, Olivier Baudoin
1, n-Metal shift is an elegant alternative approach enabling the functionalization of remote C-H bonds from simple precursors. In this work, we report a novel and simple Pd0 -catalyzed domino reaction involving 1,4-palladium shift and C(sp3 )-H activation and leading to (fused) five-membered rings. This method allowed access to a broad range of valuable arylidene γ-lactams and indanones and was applied to the formal synthesis of (-)-pyrrolam.
February 8, 2019: Organic Letters
Therese Planke, María Moreno, Stephan Hüttel, Jörg Fohrer, Franziska Gille, Matthew D Norris, Maik Siebke, Liangliang Wang, Rolf Müller, Andreas Kirschning
Total synthesis of cystobactamid 920-1 and its epimer has allowed an unambiguous assignment of the relative and absolute configuration of the natural product. A careful structural analysis of each isomer using both NMR and computational techniques also prompted a constitutional revision of the structures originally reported for cystobactamids 920-1 and 920-2, and has provided further insight into the unique conformational preferences of the cystobactamid family.
February 8, 2019: Organic Letters
Huiying Zeng, Qian Dou, Chao-Jun Li
Photoinduced transition-metal- and photosensitizer-free cross-coupling of aryl halides (including Ar-Cl, Ar-Br, and Ar-I) with H-phosphonates (including dialkyl phosphonates and diarylphosphine oxides) is reported. Various functional groups were tolerated, including ester, methoxy, dimethoxy, alkyl, phenyl, trifluoromethyl, and heterocyclic compounds. This simple and green strategy provides a practical pathway to synthesize arylphosphine oxides.
February 8, 2019: Organic Letters
Jie Wang, Takeru Torigoe, Yoichiro Kuninobu
The meta-selective introduction of functional groups into aromatic substrates was successfully achieved by hydrogen-bond-controlled meta-selective C-H borylation and successive conversion of the boryl group to other functional groups. By this method a wide range of functional groups could be introduced without isolation of the borylated intermediates. The desired meta-functionalized aromatic products were obtained in a one-pot manner even on a gram scale. Regioselective synthesis of multisubstituted aromatic compounds was also achieved...
February 8, 2019: Organic Letters
Hang Li, Cameron L M Gilchrist, Heather J Lacey, Andrew Crombie, Daniel Vuong, John I Pitt, Ernest Lacey, Yit-Heng Chooi, Andrew M Piggott
The burnettramic acids are a new class of antibiotics from an Australian fungus Aspergillus burnettii. The rare bolaamphiphilic scaffold consists of β-d-mannose linked to a pyrrolizidinedione unit via a 26-carbon chain. The most abundant metabolite displayed potent in vitro antifungal activity. Comparative genomics identified the hybrid PKS-NRPS bua gene cluster, which was verified by heterologous pathway reconstitution in Aspergillus nidulans.
February 8, 2019: Organic Letters
Li Sun, Yong Yuan, Min Yao, Han Wang, Daoxin Wang, Meng Gao, Yi-Hung Chen, Aiwen Lei
The use of additive-free conditions is an ideal approach to prepare organoselenium reagents from readily available unsaturated substrates. Thus, we report the electro-induced aminoselenation and oxyselenation of styrenes without any acids or oxidants as additives. This transformation is compatible with various functional groups, which leads to vicinal difunctionalized organoselenium compounds. Our strategy improves the potential of this protocol for use in the pharmaceutical industry. Based upon the preliminary mechanism studies, we propose two possible pathways...
February 8, 2019: Organic Letters
Shimpei Sumimoto, Masayuki Kobayashi, Rio Sato, Seiichi Shinomiya, Arihiro Iwasaki, Shoichiro Suda, Toshiaki Teruya, Toshiyasu Inuzuka, Osamu Ohno, Kiyotake Suenaga
Minnamide A is a lipopeptide with a unique repeating structure consisting of hydroxy and proposed β-branched methyl groups. The absolute configuration of minnamide A was determined by a combination of chemical degradation, chiral HPLC analyses, and synthetic methods. Minnamide A showed growth-inhibitory activity toward HeLa cells with an IC50 value of 0.17 μM and rapidly induced cell death at a concentration of 2 μM. Minnamide A induced the copper-mediated accumulation of reactive oxygen species.
February 7, 2019: Organic Letters
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