571-60-8Relevant articles and documents
Palladium-Catalyzed Dearomative syn-1,4-Carboamination
Okumura, Mikiko,Shved, Alexander S.,Sarlah, David
, p. 17787 - 17790 (2017)
A dearomative 1,4-carboamination of arenes has been achieved using arenophile cycloaddition and subsequent palladium-catalyzed substitution with nonstabilized lithium enolates. This protocol delivers products with exclusive syn-1,4-selectivity and can be also conducted in an asymmetric fashion. The method allows rapid dearomative difunctionalization of simple aromatic compounds into functional small molecules amenable to further diversification.
An Improved Synthesis of Balsaminone A
Daley, Sharna-Kay A.,Downer-Riley, Nadale K.
, p. 325 - 328 (2019)
A short and efficient synthesis of balsaminone A, a dinaphthofuran-1,4-dione, is described. The eight-step synthesis features two alternate pathways including a base-induced coupling reaction of 4-methoxy-1-naphthol and 2,3-dichloro-1,4-naphthoquinone, as well as a light-mediated cyclization of 1,1'-binaphthoquinone to afford the dinaphthofurandione core. Subsequent ortho formylation yielded a known precursor to balsaminone A, affording the natural product in 20-27% yield. This represents a moderate increase from the previous synthesis of 7.4% yield.
Synthesis of new vitamin K analogues as steroid and xenobiotic receptor (SXR) agonists: Insights into the biological role of the side chain part of vitamin K
Suhara, Yoshitomo,Watanabe, Masato,Motoyoshi, Sayaka,Nakagawa, Kimie,Wada, Akimori,Takeda, Kazuyoshi,Takahashi, Kazuhiko,Tokiwa, Hiroaki,Okano, Toshio
, p. 4918 - 4922 (2011)
Vitamin K2 has been demonstrated to induce gene expression related to bone formation through a nuclear steroid and xenobiotic receptor (SXR). We synthesized new vitamin K analogues with the same isoprene side chains symmetrically introduced at the 2 and 3 positions of 1,4-naphthoquinone and evaluated the transcriptional activity of the target gene. The transcriptional activity was related to the length of the side chain which allowed optimal interaction with ligand-binding domain of SXR.
Stereoselective [4+2] cycloaddition of singlet oxygen to naphthalenes controlled by carbohydrates
Bauch, Marcel,Fudickar, Werner,Linker, Torsten
, (2021/06/12)
Stereoselective reactions of singlet oxygen are of current interest. Since enantioselective photooxygenations have not been realized efficiently, auxiliary control is an attractive alternative. However, the obtained peroxides are often too labile for isolation or further transformations into enantiomerically pure products. Herein, we describe the oxidation of naphthalenes by singlet oxygen, where the face selectivity is controlled by carbohydrates for the first time. The synthesis of the precursors is easily achieved starting from naphthoquinone and a protected glucose derivative in only two steps. Photooxygenations proceed smoothly at low temperature, and we detected the corresponding endoperoxides as sole products by NMR. They are labile and can thermally react back to the parent naphthalenes and singlet oxygen. However, we could isolate and characterize two enantiomerically pure peroxides, which are sufficiently stable at room temperature. An interesting influence of substituents on the stereoselectivities of the photooxygenations has been found, ranging from 51:49 to up to 91:9 dr (diastereomeric ratio). We explain this by a hindered rotation of the carbohydrate substituents, substantiated by a combination of NOESY measurements and theoretical calculations. Finally, we could transfer the chiral information from a pure endoperoxide to an epoxide, which was isolated after cleavage of the sugar chiral auxiliary in enantiomerically pure form.
Single-atom cobalt-fused biomolecule-derived nitrogen-doped carbon nanosheets for selective oxidation reactions
Huang, Haitao,Wei, Qiao-Hua,Xia, Miao,Xie, Zailai,Zhang, Xuefei
, p. 14276 - 14283 (2021/07/13)
Non-noble metal single-atom catalysts hold great promise in selective oxidation reactions, although the progress is still unsatisfactory because of the synthesis challenge and the lack of mechanistic interpretations. Herein, we develop a biomolecule-based strategy to synthesize isolated Co single atom site catalysts by one-step pyrolysis of guanosine and Co precursors. Due to the abundant hydrogen bonding and π-π interaction of guanosine, the as-synthesized Co-N-C catalysts present a hierarchical porous two-dimensional (2D) nanostructure with an ultrahigh specific surface area, large pore volume, and high density of cobalt single atoms. Aberration-corrected electron microscopy and X-ray photoelectron spectroscopy reveal that Co species are present as isolated single sites and stabilized by nitrogen-doped carbon nanosheets. These characteristics make Co-GS-900 suitable as an efficient catalyst for selective oxidation of aromatic alkanes. For oxidation of ethylbenzene, Co-GS-900 exhibits a superior performancefwith 91% conversion and 98% selectivity of acetophenone.
Mechanistic and crystallographic studies of azoreductase azoa from bacillus wakoensis a01
Fraaije, Marco W.,Lon?ar, Nikola,Romero, Elvira,Savino, Simone
, p. 504 - 512 (2020/03/11)
The azoreductase AzoA from the alkali-tolerant Bacillus wakoensis A01 has been studied to reveal its structural and mechanistic details. For this, a recombinant expression system was developed which yields impressive amounts of fully active enzyme. The purified holo enzyme is remarkably solvent-tolerant and thermostable with an apparent melting temperature of 71 °C. The dimeric enzyme contains FMN as a prosthetic group and is strictly NADH dependent. While AzoA shows a negligible ability to use molecular oxygen as an electron acceptor, it is efficient in reducing various azo dyes and quinones. The kinetic and catalytic mechanism has been studied in detail using steady state kinetic analyses and stopped-flow studies. The data show that AzoA performs quinone and azo dye reductions via a two-electron transfer. Moreover, quinones were shown to be much better substrates (kcat values of 100-400 s-1 for several naphtoquinones) when compared with azo dyes. This suggests that the physiological role of AzoA and sequence-related microbial reductases is linked to quinone reductions and that they can better be annotated as quinone reductases. The structure of AzoA has been determined in complex with FMN at 1.8 ? resolution. AzoA displays unique features in the active site providing clues for explaining its catalytic and thermostability features. An uncommon loop, when compared with sequence-related reductases, forms an active site lid with Trp60 acting as an anchor. Several Trp60 mutants have been analyzed disclosing an important role of this residue in the stability of AzoA, while they retained activity. Structural details are discussed in relation to other azo and quinone reductases. This study provides new insights into the molecular functioning of AzoA and sequence-related reductases.