Total synthesis and proof of relative stereochemistry of (-)-aureonitol.
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.
Jervis
Peter J
PJ
School of Chemistry, The University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom.
Cox
Liam R
LR
D000900:Anti-Bacterial Agents / Q000138:chemical synthesis; D001688:Biological Products / Q000138:chemical synthesis; D003500:Cyclization; D005658:Fungi / Q000737:chemistry; D005663:Furans / Q000138:chemical synthesis*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D010084:Oxidation-Reduction; D013237:Stereoisomerism
D000900:Anti-Bacterial Agents; D001688:Biological Products; D005663:Furans; C533114:aureonitol