Studies On The Asymmetric Synthesis Of Bitungolides A-F

This dissertation aims at the studies on the asymmetric syntheses of dihydropyrone natural product bitungolides A-F;a mild and efficient method of cleavage of tert-butyldimethylsilyl(TBS)and tetrahydropyranyl(THP)ethers using a catalytic amount of TBPA^+·SbCl₆^- in methanol also was studied.It consisted of the following four parts:Chapter 1.The applications of chiral auxiliaries in organic syntheses(Riview)Described the introduction and applications of chiral auxiliaries in organic syntheses.Chapter 2.Studties on the asymmetrie synthesis of bitungolides A-ESynthesis of the core segment of bitungolides A-E has been achieved in 17 steps and 4.7%overall yield.Six stereogenic center of bitungolides A-E were established via allylation,dihydroxylation,Myers' alkylation and Evans aldol reaction, which give foundation for further diversity of the total synthesis of this type of natural products and its derivatives.Chapter 3.Studties on the asymmetric synthesis of bitnngolide FThe efficient asymmetric synthesis of precursor of bitungolide F has been achieved via hydroxy-directed reduction,Myers' alkylation,Evans aldol reaction, Julia coupling reaction,in which the commercially available natural product(s)- malic acid was used as starting material.Chapter 4.A mild and efficient cleavage of tert-butyldimethylsilyl(TBS)and tetrahydropyranyl(THP)ethers using a eatalytie amount of TBPA^+·SbCl₆^-The development of deprotection of tert-butyldimethylsilyl(TBS)ether was introduced briefly. A mild and efficient method for the deprotection of the TBS and THP ethers by TBPA^+·SbCl₆^- was described.The reaction conditions was optimized and the mechanism of the reaction was proposed.