Direct diastereoselective synthesis of (±)-cis- and (±)-trans-4-methylpipecolic acid and derivatives
(±)-cis- or (±)-trans-4-Methylpipecolic acid and ester derivatives can be obtained directly by addition of electrophiles to α-lithiated N-Boc 4-methylpiperidine.
Cossy, Janine,Belotti, Damien
p. 2119 - 2120
(2007/10/03)
An Improved Synthesis of Homoproline and Derivatives
An improved, general synthesis of substituted homoprolines has been developed by using readily available substituted pyridines (1).A key step in this synthetic procedure involves the known conversion of pyridine-N-oxides to 2-cyanopyridines (3) in nearly quantitative yields.The resulting nitriles are hydrolyzed to the corresponding pyridine-2-carboxylic acids (4).Subsequent reduction of the aromatic ring with PtO2/H2 gives the homoprolines (5) in good yields as racemic cis isomers.This procedure also can be utilized for the preparation of 5,6-benzohomoprolines fromthe appropriate quinoline precursors.The N-tert-butyloxycarbonyl (Boc) derivatives of these amino acids (useful intermediates for peptide synthesis) were also prepared in good yields.
Shuman, Robert T.,Ornstein, Paul L.,Paschal, Jonathan W.,Gesellchen, Paul D.
p. 738 - 741
(2007/10/02)
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