title: Concerted nature of AB ring formation in the enzymatic cyclization of squalene to hopenes.
abstract: The cyclization of the A-B rings of squalene to hopene is studied computationally (DFT). A transition structure is found for a concerted, asynchronous pathway for the formation of chair-chair decalin carbocation. The computationally derived conformer leading to this asynchronous transition structure is remarkably similar to the analogous region of 2-azasqualene encapsulated by squalene-hopene cyclase recently reported by Schulz. A concerted A-B ring closure is likely to occur in the cyclization of squalene to hopene. [structure--see text]
authors.affiliation: Department of Chemistry, Vanderbilt University, Nashville, TN 37235, USA. bahessjr@aol.com
authors.forename: B Andes
authors.initials: BA
authors.lastname: Hess
authors.forename: Lidia
authors.initials: L
authors.lastname: Smentek
mesh_terms: D018360:Crystallography, X-Ray; D003500:Cyclization; D019751:Intramolecular Transferases / Q000378:metabolism*; D008958:Models, Molecular; D008968:Molecular Conformation; D013185:Squalene / Q000737:chemistry* / Q000378:metabolism*; D014315:Triterpenes / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D014315:Triterpenes; C028765:diploptene; D013185:Squalene; D019751:Intramolecular Transferases; C066630:squalene-hopene cyclase