Rational synthesis of contra-thermodynamic spiroacetals by reductive cyclizations.
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.
Takaoka
Leo R
LR
Department of Chemistry, 516 Rowland Hall, University of California-Irvine, Irvine, California 92697, USA.
Buckmelter
Alexandre J
AJ
LaCruz
Thomas E
TE
Rychnovsky
Scott D
SD
D000080:Acetals / Q000138:chemical synthesis* / Q000737:chemistry; D003500:Cyclization; D010084:Oxidation-Reduction; D013141:Spiro Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism; D013816:Thermodynamics
D000080:Acetals; D013141:Spiro Compounds