Stereochemical assignment of 2,3-epoxy-2-methylbutanoate esters in natural products

✍ Scribed by J. Martín Torres-Valencia; Carlos M. Cerda-García-Rojas; Pedro Joseph-Nathan

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 213 KB
• Volume: 10
• Category: Article
• ISSN: 0958-0344
• DOI: 10.1002/(sici)1099-1565(199909/10)10:5<221::aid-pca458>3.0.co;2-l

✦ Synopsis

Inspection of the 182 known natural products containing 2,3-epoxy-2-methylbutanoate ester residues revealed a very high tendency in nature for the preferential epoxidation of (Z)-2-methyl-2-butenoate esters (angelates) over (E)-2-methyl-2-butenoate esters (tiglates), since 177 compounds contain epoxyangelate and only five have epoxytiglate ester residues. The absolute configuration of the epoxde group has been determined for 22 compounds, again showing a very high natural stereoselectivity, since 20 compounds have the (2R,3R) and only two the (2S,3S) absolute configuration. In contrast, unconfirmed stereochemical predictions for an additional 21 compounds suggest that 12 have the (2S,3S) and 9 the (2R,3R) configuration. Botanical sources, 1 H-NMR data of the epoxide-containing ester residue and molecular structures were compiled, and methodologies are presented to determine or to further support the absolute configuration of the 2,3-epoxy-2-methylbutanoate ester residues, based on a chemical correlation with (R)-or (S)-2-methyl-1,2-butanediol or on partial synthesis.