[Isomerization of levorin. The structure of isolevorin A2].

The products of retroaldol splitting and azonolysis of isolevorin A2 resulting from UV irradiation of levorin A2 solutions were studied in comparison with the products of the same chemical transformations of the initial levorin A2. The findings enabled to classify isolevorin A2 as a transheptaen. Investigation of the products of retroaldol splitting of isolevorin resulting from chemical isomerization suggested that along with cys- and trans-conversions during chemical isomerization there took place chloroform transference with formation of a branched polyen. NMR spectroscopy revealed 2 free carbonyls in the isolevorin A2 molecule. The other 2 formed the hemiketal rings.