Evaluation of (+)-Sparteine-like Diamines for Asymmetric Synthesis
摘要:
Three new (+)-sparteine-like diamines were prepared from (-)-cytisine and evaluated as sparteine surrogates in the alpha-lithiation rearrangement of cyclooctene oxide and the palladium(II)/diamine catalyzed oxidative kinetic resolution of I-indanol. The new diamines exhibited opposite enantioselectivity to that observed with (-)-sparteine but increasing the steric hindrance of the N-alkyl group beyond N-Et had a detrimental effect on enantioselectivity. The optimal N-Me diamine was evaluated with much success in five other (-)-sparteine-mediated processes involving different metals (lithium, magnesium, and copper) and different types of reaction mechanisms.
Synthesis of the Azaphilones (+)-Sclerotiorin and (+)-8-O-Methylsclerotiorinamine Utilizing (+)-Sparteine Surrogates in Copper-Mediated Oxidative Dearomatization
摘要:
Enantioselective syntheses of the azaphilone natural products (+)-sclerotiorin and (+)-8-O-methylsclerotiorinamine that possess the natural R-configuration at the quaternary center are reported. The syntheses were accomplished using copper-mediated asymmetric dearomatization employing bis-y-oxo copper complexes prepared from readily available (+)-sparteine surrogates. Of note, site-selective O-methylation of a vinylogous pyridone was used to access the isoquinolin-6(7H)-one core of (+)-8-O-methylsclerotiorinamine.
New chiral amine ligands in the desymmetrization of prochiral phosphine boranes
作者:Magnus J. Johansson、Lennart Schwartz、Mohamed Amedjkouh、Nina Kann
DOI:10.1016/j.tetasy.2004.09.023
日期:2004.11
phosphine ligands can be prepared via desymmetrization of prochiral phosphine boranes using s-BuLi·(−)-sparteine complexes. One limitation of this method, however, has been that (+)-sparteine is not easily accessible. Herein, we show that derivatives of another alkaloid, (−)-cytisine, are useful surrogates for (+)-sparteine in the desymmetrization of prochiral phenyl-, cyclohexyl- and tert-butyl dimethyl