title: Stereochemical investigations of the Tetrahymena cyclase, a model system for euphane/tirucallane biosynthesis.
abstract: The squalene cyclase of Tetrahymena pyriformis cyclizes 2,3-dihydrosqualene to euph-7-ene. This was used as a model for euphane biosynthesis. D-ring formation was demonstrated to involve pre-chair folding through an experiment with 2,3-dihydro-5-oxasqualene. This requires that a non-least motion rotation (120°) of the C17-20 bond in the intermediate deoxydammaranyl cation occurs before the first 1,2-hydride shift. Truncated substrates relieved the hindrance associated with this rotation and permitted a least motion pathway. Several triterpenes were found to be minor products of the Tetrahymena cyclase.
authors.affiliation: Department of Chemistry, State University of New York, College of Environmental Science and Forestry, Syracuse, NY 13210, USA. jlginer@syr.edu.
authors.forename: José-Luis
authors.identifier: http://orcid.org/0000-0002-8092-5139
authors.initials: JL
authors.lastname: Giner
authors.affiliation: Department of Chemistry, State University of New York, College of Environmental Science and Forestry, Syracuse, NY 13210, USA. jlginer@syr.edu.
authors.forename: Ju
authors.initials: J
authors.lastname: Feng
mesh_terms: D008190:Lyases / Q000737:chemistry / Q000378:metabolism*; D008954:Models, Biological; D008968:Molecular Conformation; D013185:Squalene / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D013237:Stereoisomerism; D013769:Tetrahymena pyriformis / Q000201:enzymology*; D014315:Triterpenes / Q000737:chemistry / Q000378:metabolism*
chemical_list: D014315:Triterpenes; C517934:euph-7-ene; C514393:tirucallane; D013185:Squalene; D008190:Lyases; C022651:squalene cyclase