Synthesis of [1,2-C-13]- and [2,3-C-13]-labelled delta-aminolevulinic acid

[1,2-C-13]- and [2,3-C-13]-labeled delta-aminolevulinic acids (delta-ALAs) have been prepared by a four-step sequence. [1,2-C-13]-ethyl bromoacetate was used to introduce the labels in the 1,2-labeled delta-ALA while [2-C-13]-ethyl bromoacetate and [5-C-13]-Meldrum's acid were used to introduce the labels in the 2,3-labeled derivative. These amino acid building blocks can, be used to prepare heme-containing proteins with labeled hemes according to a previously reported biosynthetic method.