Complementary diastereoselectivity in the intermolecular addition of titanium and magnesium naphtholates to asymmetric lactaldehydes
作者:Robin G. F. Giles、Cynthia A. Joll、Melvyn V. Sargent、D. Matthew G. Tilbrook
DOI:10.1039/a901456j
日期:——
S)-2-(1′-ethoxyethoxy)propanal 4 afforded solely (1S, 2R, 1″R or S)-1-(7′-benzyloxy-4′,5′-dimethoxy-1′-hydroxy-2′-naphthyl)-2-(1″-ethoxyethoxy)propan-1-ol 5, being the erythro product arising from anti addition. Complementary reaction of the naphthol 3 as its bromomagnesium naphtholate with aldehyde 4 gave rise solely to the alternative (1R, 2R, 1″R or S) diastereomer 6 . The naphthol 3 was prepared through the completely
A novel synthesis of (3R,4R)-4-acetoxy-3-[(R)-1-(t-butyldimethylsilyloxy)ethyl]-2-azetidinone, the versatile key intermediate of carbapenem synthesis, from (S)-ethyl lactate
作者:Yoshio Ito、Takeo Kawabata、Shiro Terashima
DOI:10.1016/s0040-4039(00)85317-4
日期:——
A highly efficient synthesis of the title compound was accomplished employing the addition of diketene to chiral imine as a key stereoselective reaction and using inexpensive ()-ethy1 lactate as a starting material.
The first nonracemic synthesis of (+)-geranyllinaloisocyanide, starting with (–)-lactic acid methyl ester, has been accomplished by exploiting a [3.3] sigmatropic rearrangement of allyl cyanate. The synthesis enables assignment of the S configuration of the C(3) isocyano substituted, quaternary stereogenic center in natural geranyllinaloisocyanide.
Alkanoate esters are found to couple with various nitriles to give (Z)-3-amino-2-alkenoates in good yields with the aid of a magnesium amide prepared by the reaction of ethylmagnesium bromide and diisopropylamine. The C–C bond forming reaction was applied to (2S,3S)-2,3-(cyclohexylidenedioxy)butanenitrile and the resulting adduct was successfully converted into N-benzoyl-L-daunosamine in 41% overall
A metal-mediated diastereoselective synthesis of precursors to the aphid pigment derivatives
作者:Robin G.F. Giles、Cynthia A. Joll、Melvyn V. Sargent、D.Matthew G. Tilbrook
DOI:10.1016/0040-4039(96)01748-0
日期:1996.10
Chiral compounds 16 and 17, precursors to the aphid insect pigmentderivatives, have been prepared in good to high yield, with complete control of the diastereoselectivity at the newly-created chiral centre C-1, through the use of metal phenolates derived from naphthol 3.