Abstract

Recently the synthesis of [3-13C]-, [4-13C]-, and [11-13C]- porphobilinogen, [15N,13C4]-1H - pyrrole-2,3,5 - tricar - boxylic acid, [1-15N]-3-cyano-4-methyl-1H-pyrrole and [2-13C]- and [3-13C]-cyano-4- methyl-3-pyrrolin-2-one have been published. Incorporation of 13C and 15N in these systems at any position and combination of positions has become accessible. Also mild alkylations of active methylene compounds with α-halo carbonyl compounds open up many 3-pyrrolin-2- ones and pyrrole systems based on stable isotope building blocks that have been published. This gives the access to a whole new library of stable isotope enriched pyrroles in any stable isotope enriched form. This is also the case for biliverdin IXα which after enzymatic treatment has been