Nucleophilic addition of dialkylzincs to aldehydes in hydrocarbon solvents is markedly accelerated by the presence of a catalytic amount of a β-dialkylamino alcohol. Use of certain sterically constrained chiral amino alcohols such as 3-exo-(dimethylamino)isoborneol or 1-t-butyl-2-piperidinoethanol effects highly enantioselective catalysis giving secondary alcohols in up to 99% ee. Dimethyl-, diethyl-
The present invention relates to the chemical synthesis of vittatalactone, the aggregation pheromone of the striped cucumber beetle,
Acalymma vittatum.
Iterative Deoxypropionate Synthesis Based on a Copper-Mediated Directed Allylic Substitution: Formal Total Synthesis of Borrelidin (C3–C11 Fragment)
作者:Christian Herber、Bernhard Breit
DOI:10.1002/chem.200600343
日期:2006.8.25
alkylation strategies such as enolate reactivity as well as costs and problems associated with the chiral auxiliary. Practicability of this new method is demonstrated through application in natural product syntheses. Thus, an efficient synthesis of the northern part of the angiogenesis inhibitor borrelidin (28), the deoxypropionate building block 27, could be devised, representing a formal total synthesis
Engineering Catalysts for Enantioselective Addition of Diethylzinc to Aldehydes with Racemic Amino Alcohols: Nonlinear Effects in Asymmetric Deactivation of Racemic Catalysts
Correct additions make a difference: Asymmetric deactivation and asymmetric amplification concepts coupled with a high-throughput screening technique provided a successful strategy for designing a highly enantioselective catalytic system by simple combination of a racemic aminoalcohol (rac-DB) and a nonracemic additive (AA). The example in the scheme shows the conversion of 1 into 2 with up to 92
Synthesis of Unit A of Cryptophycin via a [2,3]-Wittig Rearrangement
作者:Jian Liang、David W. Hoard、Vien Van Khau、Michael J. Martinelli、Eric D. Moher、Richard E. Moore、Marcus A. Tius
DOI:10.1021/jo9815958
日期:1999.3.1
cryptophycins from (S)-trans-3-penten-2-ol and from (S)-trans-4-hexen-3-ol has been completed. The key stereodetermining step is a [2,3]-Wittig rearrangement of a propargyl ether. Elaboration of the rearrangement product was accomplished by means of a selective hydroboration-oxidation of a terminal alkyne, Horner-Emmons homologation of the derived aldehyde, followed by selective ozonolytic cleavage and Wittig