An important method for the N-tert-butoxycarbonyl protection of the amino functionality of α-alkylated prolines and other sterically hindered α,α-disubstituted amino acids has been developed in which the lipophilic base tetramethylammonium hydroxide is used to solubilize the otherwise insoluble zwitterionic amino acid in acetonitrile, thereby obviating the need for an aqueous medium.
Bibliographical noteFunding Information:
This work was supportebdyan NIH grant( NS20036t)o R.L.J. We thankP .W. Banresf or providings amples of compoundlsa and ld.