title: Rational synthesis of contra-thermodynamic spiroacetals by reductive cyclizations.
abstract: A synthesis of spiroacetals was developed using a reductive cyclization strategy that leads stereoselectively to spiroacetals with a single anomeric stabilization. The method begins with the synthesis of spiro ortho esters. The ortho ester is converted to a cyano acetal. Reductive lithiation of the cyano acetal generates an axial dialkoxylithium reagent, and intramolecular cyclization produces a new ring with retention of configuration. The strategy is convergent and produces complex spiro acetals in only a few steps. The method will be useful in the synthesis of natural products and will facilitate the synthesis of previously inaccessible contra-thermodynamic acetals.
authors.affiliation: Department of Chemistry, 516 Rowland Hall, University of California-Irvine, Irvine, California 92697, USA.
authors.forename: Leo R
authors.initials: LR
authors.lastname: Takaoka
authors.forename: Alexandre J
authors.initials: AJ
authors.lastname: Buckmelter
authors.forename: Thomas E
authors.initials: TE
authors.lastname: LaCruz
authors.forename: Scott D
authors.initials: SD
authors.lastname: Rychnovsky
mesh_terms: D000080:Acetals / Q000138:chemical synthesis* / Q000737:chemistry; D003500:Cyclization; D010084:Oxidation-Reduction; D013141:Spiro Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism; D013816:Thermodynamics
chemical_list: D000080:Acetals; D013141:Spiro Compounds