Determination of the conformation of E and Z zearalenone and their 7α- and 7β-hydroxy congeners

Article abstract of DOI:10.1016/S0957-4166(00)86149-2

The CD spectra of some resorcylic acid macrocyclic lactones (RAL) are reported. The spectra of the E,Z-isomeric ketones 1,6 are very similar in shape and magnitude. The Cotton effects of the 7α-alcohols 2 and 7 are also of the same shape, but the Δε values of 7 are only ca. 50% of those of the others. The E-7β-ol 3 gives a completely different CD, whereas in the Z-series 8 shows a similar CD curve as 6 and 7, but with again reduced magnitude. The CDs of the acetates 4 and 5 are very similar to those of the corresponding alcohols 2 and 3, resp. The effect of the 7α- and 7β-hydroxy or acetoxy group on the absolute conformation of the 'chain' from C(5) to C(10) is thus transmitted to the absolute value of the torsional angle of the inherently chiral chromophore C(11)-C(12)-C(12a)-C(1a)-C(=O)O in 2,3 and 4,5, resp. The CD spectra of the E,Z-isomers do not exhibit straightforward correlation with the configuration around the C=C double bond.