Thiamine pyrophosphate is a vitamin B-1 derivative that acts as a coenzyme of transketolase. Thiamine pyrophosphate is used in studies to assess decarboxylation mechanisms in biological systems.

3-Methylhistidine belongs to the class of organic compounds known as histidine and derivatives. Histidine and derivatives are compounds containing cysteine or a derivative thereof resulting from reaction of cysteine at the amino group or the carboxy group or from the replacement of any hydrogen of glycine by a heteroatom.

It is an isomer of cresotinic acid (2-hydroxy-3-methylbenzoic acid) and oxymethylbenzoic acid (2-methoxybenzoic acid). Derivatives of mandelic acid are formed as a result of metabolism of adrenaline and noradrenaline by monoamine oxidase and catechol-o-methyl transferase.