58801-71-1Relevant academic research and scientific papers
Total synthesis of (+)-gregatin B and e
Kusakabe, Taichi,Kawai, Yasuko,Kato, Keisuke
, p. 5102 - 5105 (2013)
The first total synthesis of (+)-gregatin E and a new total synthesis of (+)-gregatin B are described. Key features of our synthetic approach involve a palladium-catalyzed cyclization-methoxycarbonylation of optically active propargylic acetate and a Suzuki-Miyaura coupling or CuTC-mediated coupling reaction. The absolute configuration of (+)-gregatin E (5R,5′S) is proposed.
Total Synthesis of (-)-Graminin A Based on Asymmetric Cyclization Carbonylation of Propargyl Acetate
Ito, Yoichi,Kusakabe, Taichi,Dhage, Yogesh Daulat,Takahashi, Keisuke,Sakata, Ken,Sasai, Hiroaki,Kato, Keisuke
, p. 16268 - 16277 (2019/12/27)
The first total synthesis of (-)-graminin A is described. Key features of our synthetic approach involve a palladium-catalyzed asymmetric cyclization carbonylation of prochiral propargylic acetate, conversion of the orthoester product into methyl 4-oxo-3-furancarboxylate, and copper complex-mediated aldol condensation of (+)-gregatin B bearing a diene moiety. A new synthesis of (+)-gregatin B and the first synthesis of (-)-graminin A were achieved.
Total syntheses of the dihydrofuranonecarboxylate natural products gregatin b and e: Gram-scale synthesis of (+)-gregatin b and unambiguous assignment of the stereostructure of (+)-gregatin e
Weber, Fabian,Brückner, Reinhard
, p. 6428 - 6431 (2015/02/05)
We synthesized the dextrorotatory enantiomers of gregatin B (1.3 g scale) and E, establishing their diene side chains in the last step by Heck coupling with variable iodoolefins. Their counterpart was synthesized in 30% overall yield and with high enantio
Total syntheses of the gregatins A-D and aspertetronin A: Structure revisions of these compounds and of aspertetronin B, together with plausible structure revisions of gregatin E, cyclogregatin, graminin A, the penicilliols A and B, and the huaspenones A and B
Burghart-Stoll, Heike,Brueckner, Reinhard
experimental part, p. 3978 - 4017 (2012/10/18)
Comprehensive comparisons of 1H and 13C NMR chemical shift values in the furanone cores a, b, and c provide plausible support for a reassessment of the furanone nuclei of the title compounds from b to c. Total syntheses via enantiomerically pure lactic esters were based on the Seebach-Frater "self-reproduction of stereocenters" methodology. Attachment of the hexadienyl side-chain in a trans,trans-selective manner was achieved by addition of the Seebach-Frater enolate to trans-hex-4-en-1-al rather than to trans-hex-3-en-1-al. The type-c furanone cores of the synthetic materials were reached by single or double acylation of a model γ-hydroxy-β-oxo ester (compound 50) and its hexadiene-containing counterpart 29. Our syntheses confirmed the novel connectivities in six compounds. In addition, they required revision of the configuration of a quaternary carbon atom in five cases. Moreover, they allowed elucidation of the configurations of four previously unassigned stereocenters. Hindsight analyses of why the furanone cores of the title compounds had been misinterpreted as a and/or b instead of c are given. Why the stereocenters in the heterocycles had been incorrectly configured, on the bases (a) of relay studies in the 1960s, and (b) of a 1984 total synthesis of gregatin B, is also discussed.
A serendipitous synthesis of (+)-gregatin B, second structure revisions of the aspertetronins, gregatins, and graminin A, structure revision of the penicilliols
Burghart-Stoll, Heike,Brueckner, Reinhard
supporting information; experimental part, p. 2730 - 2733 (2011/07/30)
A (DHQN)2AQN-promoted asymmetric dihydroxylation (92% ee) of the allyl chloride derived from enynol (E)-13 and an 8-step sequence provided access to the hydroxyethylated furanone (R)-21. Oxidation with MnO2 furnished 50% furanone (+)
Synthesis and Absolute Configuration of Natural Gregatin B
Takaiwa, Akihiro,Yamashita, Kyohei
, p. 2061 - 2066 (2007/10/02)
(S)-(+)-Gregatin B and racemic gregatin B were synthesized from tetrahydro-2-methyl-5-oxo-2-furancarboxylic acid and the absolute configuration of natural gregatin B was determined as (S).
