Most of the phthalates are contamination as a plastisizer from the plastic vessel of organic solvents. By the way, there is some especially para derivatives of phthalate as natural products. The ortho ones mostly from the plastisizers!!!
I tend to think that phthalates and related compounds are the contaminants derived from plastic vessels and equipment used in experimental work. The levels of phtalates in my samples (fatty acid methyl esters) were always lower when I used only glass vessels. Anyway, why don't we imagine the ways of natural synthesys of this compound? Any thoughts? :)