Site-Selective Methylation of Nβ-Nosyl Hydrazides of N-Nosyl Protected α-Amino Acids

The methylation reaction of Nβ-nosyl hydrazides of N-nosyl protected α-amino acids by using diazomethane shows a controlled regiochemical trend and makes it possible to obtain the corresponding products methylated at specific positions depending on the amount of diazomethane used. The observed selectivity is closely connected with the different acidity of sulfonyl hydrazide, sulfonamide, and acyl hydrazine protons present in the analyzed substrates. The reactivity order of these three diverse reactive sites is supported by theoretical calculations. The hydrazine derivatives considered in this work belong to a class of compounds with interesting biological activity and of great interest in organic synthesis.