Upon treatment with base, N-acylated alpha-amino acids loaded on Wang
resin undergo cyclative Claisen-type condensation to release the tetra
mic acid in high yield and purity. The use of tetrabutylammonium hydro
xide as base simplifies product purification, as it can be scavenged b
y acidic Amberlyst A-15 ion exchange resin. The diversity of the tetra
mic acids can be further increased by reductive alkylation of the star
ting amino acid. (C) 1998 Elsevier Science Ltd. All rights reserved.