Diethyl oxalpropionate also known as methyloxalacetic acid diethyl ester or diethyl methyloxalacetate is a member of the class of compounds known as beta-keto acids and derivatives. These compounds are organic compounds containing an aldehyde substituted with a keto group on the C3 carbon atom.

1-Methylhistamine dihydrochloride is a major metabolite of histamine by histamine N-methyltransferase in the pathway of histidine metabolism.?It has been used as a biomarker of histaminergic system activity in the brains of Alzheimer's disease patients as well as those with hypersomnia and other neurological conditions.

2'-O-Methyladenosine, a methylated adenine residue is found in the urine of normals and adenosine deaminase deficient patients. It shows unique hypotensive activities.