Substrate-Controlled and Organocatalytic Asymmetric Synthesis of Carbocyclic Amino Acid Dipeptide Mimetics
摘要:
The asymmetric synthesis of a carbocyclic delta-amino acid representing the P-2/P-3 subunit of a nonpeptidic truncated peptidomimetic molecule is described relying on two independent approaches.
Michael Additions Catalysed by N,N-dimethyl-3-aminopropyl - Derivatised Amorphous Silica and Hexagonal Mesoporous Silica (HMS)
作者:James E. G. Mdoe、James H. Clark、Duncan J. Macquarrie
DOI:10.1055/s-1998-1731
日期:1998.6
Solid bases prepared by derivatisation of amorphous silica and hexagonal mesoporous silica with dimethylaminopropyl groups are good catalysts for Michael addition reactions. Of the prepared catalysts, those based on hexagonal mesoporous silica show particularly high activities. The sol-gel method used in preparing the catalysts based on hexagonal mesoporous silica enables loading to be increased to more than twice that of those based on amorphous silica which are prepared by the post-modification method.
作者:Philip B. Kisanga、Palanichamy Ilankumaran、Brandon M. Fetterly、John G. Verkade
DOI:10.1021/jo010228k
日期:2002.5.1
The 1,4-addition of primary alcohols, higher nitroalkanes, and a Schiff's base of an alpha-amino ester to alpha,beta-unsaturated substrates produces the corresponding products in moderate to excellent yields when carried out at -63 to 70 degreesC in the presence of catalytic amounts of the nonionic strong bases P(RNCH2CH2)(3)N (R = Me, i-Pr, i-Bu) in isobutyronitrile. Diastereoselectivity for the anti form of the product is high in the case of the Schiff's base in the absence of lithium ion. These catalysts are easily removed from the product by either column filtration through silica gel or via aqueous workup.
Asymmetric conjugate addition of nitroalkanes to enones with a chiral α-aminophosphonate catalyst
Chiral diethyl (2R)-tetrahydropyrro-2-ylphosphonate is an effective catalyst for the Michael addition of nitroalkanes to alpha,beta-unsaturated ketones. This Study revealed that the hydrate salt of this alpha-aminophosphonate was found to be a better catalytic species. Moderate to high enantioselectivities were achieved in reactions that tolerate various nitroalkanes and enones in the presence of low loading of both catalyst ( 10 mol %) and bulk base (25 mol %). (C) 2008 Published by Elsevier Ltd.
Cetyltrimethylammonium hydroxide (CTAOH) as a general, ecofriendly catalyst for the formation of carbon–carbon bond through nitroalkanes
作者:Roberto Ballini、Dennis Fiorini、Maria Victoria Gil、Alessandro Palmieri
DOI:10.1016/j.tet.2004.01.067
日期:2004.3
Nitroalkanes have been found to give good yields in Michael and nitroaldol (Henry) reactions by the use of a catalytic amount (10 mol%) of CTAOH. at room temperature and under solvent free conditions and in very short reaction times. The methods do not need a large excess of the nitroalkanes and show good chemoselectivity toward further functionalities. (C) 2004 Elsevier Ltd. All rights reserved.
KOZLOV N. S.; GLADKIX L. V., VESTSI AN BSSR. CEP. XIM. N., IZV. AN BSSR. CEP. XIM. N., 1979, HO 4, 127+