Burghart-Stoll, Heike; Brueckner, Reinhard published an article in 2012, the title of the article was 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.Category: esters-buliding-blocks And the article contains the following content:
Comprehensive comparisons of 1H and 13C NMR chem. 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” methodol. 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 model γ-hydroxy-β-oxo ester I and its hexadiene-containing counterpart II. 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. The experimental process involved the reaction of (R)-Methyl 3-hydroxybutanoate(cas: 3976-69-0).Category: esters-buliding-blocks
The Article related to synthesis lactic ester gregatin aspertetronin, mol structure revision gregatin graminin aspertetronin penicilliol huaspenone cyclogregatin, nmr chem shift mol structure revision furanone derivative, seebach frater self reproduction stereocenters methodol synthesis gregatin aspertetronin, hexadienyl side chain addition trans selective manner and other aspects.Category: esters-buliding-blocks
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