69841-15-2Relevant academic research and scientific papers
Identification of crucial bottlenecks in engineered polyketide biosynthesis
Grote, Marius,Kushnir, Susanna,Pryk, Niclas,M?ller, David,Erver, Julian,Ismail-Ali, Ahmed,Schulz, Frank
supporting information, p. 6374 - 6385 (2019/07/10)
The concept of combinatorial biosynthesis promises access to compound libraries based on privileged natural scaffolds. Ever since the elucidation of the biosynthetic pathway towards the antibiotic erythromycin A in 1990, the predictable manipulation of type I polyketide synthase megaenzymes was investigated. However, this goal was rarely reached beyond simplified model systems. In this study, we identify the intermediates in the biosynthesis of the polyether monensin and numerous mutated variants using a targeted metabolomics approach. We investigate the biosynthetic flow of intermediates and use the experimental setup to reveal the presence of selectivity filters in polyketide synthases. These obstruct the processing of non-native intermediates in the enzymatic assembly line. Thereby we question the concept of a truly modular organization of polyketide synthases and highlight obstacles in substrate channeling along the cascade. In the search for the molecular origin of a selectivity filter, we investigate the role of different thioesterases in the monensin gene cluster and the connection between ketosynthase sequence motifs and incoming substrate structures. Furthermore, we demonstrate that the selectivity filters do not apply to new-to-nature side-chains in nascent polyketides, showing that the acceptance of these is not generally limited by downstream modules.
Control of the Chemoselectivity of Metal N-Aryl Nitrene Reactivity: C-H Bond Amination versus Electrocyclization
Kong, Chen,Jana, Navendu,Jones, Crystalann,Driver, Tom G.
supporting information, p. 13271 - 13280 (2016/10/22)
A mechanism study to identify the elements that control the chemoselectivity of metal-catalyzed N-atom transfer reactions of styryl azides is presented. Our studies show that the proclivity of the metal N-aryl nitrene to participate in sp3-C-H bond amination or electrocyclization reactions can be controlled by either the substrate or the catalyst. Electrocyclization is favored for mono-β-substituted and sterically noncongested styryl azides, whereas sp3-C-H bond amination through an H-atom abstraction-radical recombination mechanism is preferred when a tertiary allylic reaction center is present. Even when a weakened allylic C-H bond is present, our data suggest that the indole is still formed through an electrocyclization instead of a common allyl radical intermediate. The site selectivity of metal N-aryl nitrenes was found to be controlled by the choice of catalyst: Ir(I)-alkene complexes trigger electrocyclization processes while Fe(III) porphyrin complexes catalyze sp3-C-H bond amination in substrates where Rh2(II) carboxylate catalysts provide both products.
Divergent enantioselective total synthesis of siphonarienal, siphonarienone, and pectinatone
Yadav, Jhillu Singh,Chary, D. Narasimha,Yadav, Nagendra Nath,Sengupta, Sandip,Subba Reddy, Basi V.
, p. 1968 - 1977 (2013/11/06)
A divergent synthesis of siphonarienal, siphonarienone, and pectinatone has been achieved from a common precursor 4, which was synthesized by using an enzymatic desymmetrization approach. The major key steps involved were Grignard reaction, Wittig reactio
Revisiting [3 + 3] route to 1,3-cyclohexanedione frameworks: Hidden aspect of thermodynamically controlled enolates
Ishikawa, Teruhiko,Kadoya, Ryuichiro,Arai, Masaki,Takahashi, Haruka,Kaisi, Yumi,Mizuta, Tomohiro,Yoshikai, Kazusa,Saito, Seiki
, p. 8000 - 8009 (2007/10/03)
We have revisited the traditional consecutive Michael-Claisen [3 + 3] process (MC-[3+3]) promising the synthesis of a cyclohexane-1,3-dione derivatives from nonactivated simple ketones and enoates and evaluated its potential in modern organic synthesis. Twenty to thirty examples were demonstrated to be effective. The reactions exhibited remarkable regioselectivity with the Michael addition proceeding through nucleophilic attack by the more hindered site of the ketones without exception. The subsequent Claisen condensation resulted in the formation of carbon-carbon bonds between less hindered site of the ketones and acyl carbon of the enoates. The MC-[3+3] process described is useful for the synthesis of Taxol A-ring synthons in multigram quantities and for the synthesis of other six-membered carbocyclic compounds. A number of control experiments have been conducted to provide strong support for the mechanism of this MC-[3+3].
SEQUENCE OF ALKYLATION OF CYCLOHEXANE-1,3-DIONE. ALTERNATIVE SYNTHESIS OF (+/-)-ANGUSTIONE
Zenyuk, A. A.,Lis, L. G.,Ukhova, L. I.
, p. 400 - 403 (2007/10/02)
A method is proposed for introducing one, two, or three alkyl substituents into positions 4 and 6 of the cyclohexane-1,3-dione molecule by successive alkylation under the action of strong bases. (+/-)-Angustione (a natural β-diketone) has been synthesized.
