DETERMINATION OF THE CONFORMATION OF E AND Z ZEARALENONE AND THEIR 7-ALPHA-HYDROXY AND 7-BETA-HYDROXY CONGENERS

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 7-alpha-alcohols 2 and 7 are also of the same shape, but the DELTA-epsilon-values of 7 are only ca. 50% of those of the others. The E-7-beta-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 7-alpha- and 7-beta-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.