Total synthesis and proof of relative stereochemistry of (-)-aureonitol |
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Authors: | Jervis Peter J Cox Liam R |
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Affiliation: | School of Chemistry, The University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom. |
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Abstract: | Two trisubstituted epimeric tetrahydrofurans, 1 and 2, have been synthesized in order to confirm the relative stereochemistry in the natural product aureonitol. The key step in the synthesis of 1 and 2 involved a stereoselective intramolecular allylation of an allylsilane with an aldehyde, which introduced the stereotriad in the five-membered ring. The major tetrahydrofuran diastereoisomer 18 from this cyclization reaction was subsequently elaborated to tetrahydrofuran 1. Its 3-epimer (2) was then prepared from 1 via an oxidation-reduction sequence. Compound 1 exhibits identical (1)H NMR data to those reported for aureonitol, which was isolated from Helichrysum aureonitons by Bohlmann in 1979, whereas the (1)H NMR data for 2 are markedly different. The (1)H NMR data (in CDCl3, CD3OD, and C6D6) and (13)C NMR data (in CDCl3) for 1 are also identical with those reported for a natural product isolated from various Chaetomium sp. by Abraham, Seto, and Teuscher. These findings support Abraham's conclusion that the structure of aureonitol should be revised from 2 to 1. The enantioselective synthesis of 1 has also confirmed that (-)-aureonitol isolated by Abraham contains the (2S,3R,4S) absolute configuration of stereocenters on the tetrahydrofuran ring. |
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