Partial synthesis of C-ring derivatives from oleanolic and maslinic acids. Formation of several triene systems by chemical and photochemical isomerization processes

Some triterpenic compounds modified in C-ring were semi-synthesised from oleanolic acid contained in the solid waste of olive-oil pressing. The corresponding esters of oleanolic and maslinic acids rendered products with a diene system, which led to oleantrienes resembling previtamin D2 by an electrocyclic reaction. Chemical and photochemical isomerization of these compounds yielded two different trienes with similar structure to tachysterol and vitamin D2.