The total synthesis of the dienoyl tetramic acid antibiotic (+/-)-tirandamycin B is described. The key transformations of the strategy include (1) cyclization of pyranone 14 with fluorosilicic acid to provide the 2,6-dioxabicyclo[3.3.1]nonane system of the natural product, (2) reductive removal of the benzyl ether from enone 15, and (3) attachment of the tetramic acid moiety by using the Schlessinger phosphonate protocol. Protection of the primary hydroxyl function of tirandamycin B as the triisopropylsilyl (TIPS) ether was crucial to the success of the strategy.
Total synthesis of the polyether antibiotic ionomycin
作者:David A. Evans、Robert L. Dow、Thomas L. Shih、James M. Takacs、Robert Zahler
DOI:10.1021/ja00169a042
日期:1990.6
A convergent asymmetric synthesis of the calcium ionophore ionomycin has been achieved through a route that is outlined below. The four illustrated subunits, which comprise the c,-C,,-,, CI)-&r cI&22, and C=-C32 portions of ionomycin,
An expeditious total synthesis of kalkitoxins: determination of the absolute stereostructure of natural kalkitoxin
作者:Fumiaki Yokokawa、Toshinobu Asano、Tatsufumi Okino、William H. Gerwick、Takayuki Shioiri
DOI:10.1016/j.tet.2004.06.014
日期:2004.8
Kalkitoxin, a potent neurotoxin isolated from the marine cyanobacteria Lyngbyamajuscula, and its congeners (1–7) were efficiently synthesized utilizing Hruby's diastereoselective 1,4-addition and the Wipf's oxazoline-thiazoline conversion as key steps. These synthetic efforts in combination with spectral studies of natural kalkitoxin clearly determined the absolute stereostructure of kalkitoxin to
Hydroformylation as a simple and efficient one carbon homologation of homoallylic alcohols. Synthesis of prelog-djerassi lactone.
作者:P.G.M. Wuts、M.L. Obrzut、P.A. Thompson
DOI:10.1016/s0040-4039(01)90179-0
日期:1984.1
A hydroformylation oxidation sequence is described for the efficient conversion of homoallylic alcohols to δ-lactones. The methodology is applied to the synthesis of Prelog-Djerassilactone.
Effects of Olefin Geometry on the Stereochemistry of Lewis Acid Mediated Additions of Crotylstannanes to Aldehydes
作者:Gary E. Keck、Kenneth A. Savin、Erik N. K. Cressman、Duane E. Abbott
DOI:10.1021/jo00104a054
日期:1994.12
The role of the double bond geometry (E/Z stereochemistry) in reactions of crotylstannanes with aldehydes has been examined for representative ''simple'', alpha-alkoxy, and beta-alkoxy aldehydes. For the reaction of crotylstannane with simple achiral aliphatic, aromatic, or alpha,beta unsaturated aldehydes mediated by BF3.Et(2)O, use of the E crotylstannane gives much enhanced syn selectivity over that obtained with Z (e.g., 43:1 vs 4:1 with benzaldehyde). A synclinal transition state in which the CH(2)SnBu(3) group is gauche to oxygen is proposed to explain these results. For alpha-alkoxy aldehydes, use of the E stannane with MgBr2 gives the highest syn selectivity, while the Z stannane gives slightly better stereoselectivity with beta-alkoxy substrates. In contrast, the use of TiCl4 gives anti products preferentially from the E stannane and either alpha or beta-alkoxy substrates.
Crotylzirconium derivatives as a new reagent for the threo selective synthesis of β-methylhomoallyl alcohols