title: Triple shifts and thioether assistance in rearrangements associated with an unusual biomethylation of the sterol side chain.
abstract: Quantum chemical calculations (B3LYP and MP2) are described for the formation and rearrangements of carbocations derived from the biological methylation reaction that produces 24-propyl sterols in pelagophyte algae. Previous mechanistic proposals are discussed in light of the results of these calculations. Of particular note is the prediction of a new triple-shift rearrangement that is inherently preferred for the biosynthetically relevant carbocations. Our calculations also reveal how these reactions may be affected by intermolecular interactions with S-adenosylmethionine.
authors.affiliation: Department of Chemistry, University of California-Davis, 1 Shields Avenue, Davis, California 95616, USA.
authors.forename: Young J
authors.initials: YJ
authors.lastname: Hong
authors.forename: José-Luis
authors.initials: JL
authors.lastname: Giner
authors.forename: Dean J
authors.initials: DJ
authors.lastname: Tantillo
mesh_terms: D008745:Methylation; D015394:Molecular Structure; D011789:Quantum Theory; D012436:S-Adenosylmethionine; D013261:Sterols / Q000737:chemistry*; D013440:Sulfides / Q000737:chemistry*
chemical_list: D013261:Sterols; D013440:Sulfides; D012436:S-Adenosylmethionine