W. Maison et al., Synthesis of novel pipecolic acid derivatives: a multicomponent approach from 3,4,5,6-tetrahydropyridines, J CHEM S P1, (23), 1999, pp. 3515-3525
A simple approach to several derivatives of pipecolic acid is via a multico
mponent reaction starting from cyclic imines 2, which are synthesized on a
large scale and with different substitution patterns. The protected amino a
cids 3 are formed in high yields. In cases where chiral imines are used the
target compounds are obtained with remarkable diastereoselectivity. Bisami
des 3 serve as versatile precursors for the preparation of a wide range of
amino acid derivatives. Different methods of hydrolysis of 3 lead to the fr
ee pipecolic acids or its derivatives. Employment of methanol or ethanethio
l as a nucleophile in the acid-mediated conversion of enamides 3 results in
N-acylated amino acid esters 5. Furthermore a method for the resolution of
the obtained racemic alpha-amino acids via diastereomeric salt formation i
s described.