Amino Acids as Substrates in the Synthesis of Substituted Organocobalamins

Abstract

Abstract The amino acids alanine, valine, leucine, isoleucine, norvaline, α-amino butyric acid, and β -methyl aspartic acid are utilized as substrates for organocobalamin syntheses under “oxidizing/reducing” conditions. In the presence of V+3 as the reducing agent, free radicals are generated by the reaction of oxygen radicals with the amino acids through hydrogen atom abstraction. These amino acid radicals then combine with the cobalt atom of vitamin B12r to yield the respective organocobalamins. The cobalamin obtained from the reaction of β-methyl aspartic acid is a possible intermediate in the coenzyme B12 dependent skeletal rearrangement of β-methyl aspartic acid to glutamic acid. HPLC analysis of the cobal-amins prepared from D, L-alanine indicates that the corrin ligand is relatively ineffective at promoting asymmetric syntheses under these conditions.