(4-acetyl-2-ethoxycarbonyl-5-methyl-pyrrol-3-yl)-acetic acid ethyl ester

2,2’-(1,3-dioxane-2,2-diyl)diethanol

7-(carboxymethyl)-1,4-dioxaspiro[4.5]dec-7-ene-8-carboxylic acid

2-(carboxymethyl)furan-3-carboxylic acid