Deprotection of t-butyl esters of amino acid derivatives by nitric acid in dichloromethane

The extension of the deprotection procedure of t-butylated carboxyl function using HNO3 in CH2Cl2 to a number of appropriately selected N-Z-derivatives of natural amino acid esters was investigated. The method was found to work effectively with alanine, phenylalanine, serine and the dipeptide aspartame, but the reagent brought about a number of unwanted transformations with tyrosine, methionine and tryptophan. Suitable protection of functions present in the latter ones allowed selective ester dealkylation, but tyrosine underwent unavoidable fast preliminary ring nitration. (C) 2000 Elsevier Science Ltd. All rights reserved.