title: Direct access to 6/5/7/5- and 6/7/5/5-fused tetracyclic triterpenoids via divergent transannular aldol reaction of lanosterol-derived diketone.
abstract: In an effort to access biologically relevant chemical space, a complex natural product derived nonsymmetrical diketone was prepared as a substrate for divergent transannular aldol reactions. The use of common aldol conditions resulted in predominant syn-addition via pathway a, while the use of alumina provided access to the anti-adduct. Screening of a range of Lewis acids of varying strength unexpectedly resulted in the formation of aldol products with 6/7/5/5-fused molecular skeleton via pathway b.
authors.affiliation: Department of Chemistry, Case Western Reserve University , 10900 Euclid Avenue, Cleveland, Ohio 44106, United States.
authors.forename: Vasily A
authors.initials: VA
authors.lastname: Ignatenko
authors.forename: Yong
authors.initials: Y
authors.lastname: Han
authors.forename: Gregory P
authors.initials: GP
authors.lastname: Tochtrop
mesh_terms: D007659:Ketones / Q000737:chemistry*; D007810:Lanosterol / Q000737:chemistry*; D008968:Molecular Conformation; D013237:Stereoisomerism; D014315:Triterpenes / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D007659:Ketones; D014315:Triterpenes; D007810:Lanosterol