Circular dichroism—LXIV

The 1 B 2u -band CD of siccanin ( 3 ) and some of its derivatives obeys the known rules for the benzene chromophore with the appropriate substitution pattern. The CD spectrum of the chromanone 8 is better resolved than that of related flavanones, the band between 300–320 nm is most probably the 1 B 2u -band of this chromophore. The non-planar styrenes 10–12 symmetrically substituted in the benzene ring with respect to the “pivot” bond follow Crabbe's rule, and the absolute configuration of siccanochromene-A ( 13 ) in the chromene ring follows from its CD to be S .