Publication Details (including relevant citation information):
Carlier, P. R.; Lam, P. C.-H.; Wong, D. M. Catalytic asymmetric synthesis of protected tryptophan regioisomers.
Journal of Organic Chemistry 2002, 67, 6256 -6259.
PMID: 12182675. http://dx.doi.org/10.1021/jo025964i
Tryptophan 1 (Trp) is superior to all other naturally occurring peptide residues in its ability to bind cations (the cation- interaction). In an effort to expand the toolbox of Trp-like amino acids, in this note we report catalytic asymmetric syntheses of Trp regioisomers 2a-e, where the alanine unit is attached not to C-3 of indole but to C-2, C-4, C-5, C-6, or C-7. Excellent asymmetric induction is obtained in each case (generally >97% ee). Ab initio calculations suggest that the indole nuclei of 2a-e will bind Na+ with the same affinity as that of Trp.
Address (URL): http://dx.doi.org/10.1021/jo025964i