title: Bismuth triflate-catalyzed Wagner-Meerwein rearrangement in terpenes. Application to the synthesis of the 18alpha-oleanane core and A-neo-18alpha-oleanene compounds from lupanes.
abstract: The use of bismuth(III) salts as catalysts for the Wagner-Meerwein rearrangement of lupane derivatives with expansion of ring E and formation of an additional O-containing ring is reported. This process has also been extended to other terpenes, such as the sesquiterpene (-)-caryophyllene oxide. When the reaction was performed with oleanonic acid, 28,13beta-lactonization occurred, without Wagner-Meerwein rearrangement. Under more vigorous reaction conditions, dehydration of the 3beta-hydroxyl group and subsequent additional Wagner-Meerwein rearrangement led to the selective synthesis of A-neo-18alpha-oleanene compounds, in very high yields.
authors.affiliation: Laboratório de Química Farmacêutica, Faculdade de Farmácia, Universidade de Coimbra, 3000-295 Coimbra, Portugal. salvador@ci.uc.pt
authors.forename: Jorge A R
authors.initials: JA
authors.lastname: Salvador
authors.forename: Rui M A
authors.initials: RM
authors.lastname: Pinto
authors.forename: Rita C
authors.initials: RC
authors.lastname: Santos
authors.forename: Christophe
authors.initials: C
authors.lastname: Le Roux
authors.forename: Ana Matos
authors.initials: AM
authors.lastname: Beja
authors.forename: José A
authors.initials: JA
authors.lastname: Paixão
mesh_terms: D002384:Catalysis; D008698:Mesylates / Q000737:chemistry*; D009828:Oleanolic Acid / Q000031:analogs & derivatives* / Q000737:chemistry; D012997:Solvents / Q000737:chemistry; D013379:Substrate Specificity; D013729:Terpenes / Q000737:chemistry*; D014315:Triterpenes / Q000737:chemistry*; D053978:Pentacyclic Triterpenes
chemical_list: D008698:Mesylates; D009828:Oleanolic Acid; D012997:Solvents; D013729:Terpenes; D014315:Triterpenes; C413246:oleanane; C480546:lupane; D053978:Pentacyclic Triterpenes; C445789:Bi(OTf)3