Stereoselective synthesis of the ABCD ring framework of azaspiracids |
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Authors: | JS Yadav Sipak Joyasawal AC Kunwar |
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Affiliation: | a Division of Organic Chemistry, Indian Institute of Chemical Technology, Hyderabad 500 007, India b Centre for Nuclear Magnetic Resonance, Indian Institute of Chemical Technology, Hyderabad 500 007, India |
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Abstract: | A stereoselective synthesis of the ABCD ring framework of azaspiracid-1 and azaspiracid-3 has been achieved using a tandem bis-spiroketalization protocol in the presence of a mild proton source from 1,4-diketone precursor. A tetrahydrofuran intermediate with the correct stereochemistry for the D ring of azaspiracids-1 and 3 was then taken through a linear sequence of reactions to afford the desired diketone precursor. The D-ring of azaspiracid-1 was then constructed by employing a Sharpless asymmetric dihydroxylation followed by etherification using a homoallyl derivative. The structure of the ABCD ring framework with four contiguous rings was established by extensive NMR analysis. |
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Keywords: | Substituted tetrahydrofuran ring 7-Membered acetonide Radical cyclization Acetylenic alcohol |
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