Structures of two dimers formed from lomatin(9,10-dihydro-9-hydroxy-8,8-dimethyl-8H-benzo[1,2-b:3,4-b′]dipyran-2-one)

Abstract

Treatment of lomatin (Ia) with toluene-p-sulphonic acid in xylene gives, along with dihydro-oroselone (II), two minor epimeric dimers, identified on the basis of spectral evidence, in which one of the benzodipyran units has rearranged. A nearly quantitative yield of dihydro-oroselone(II) was obtained from lomatin(Ia) by treatment with perchloric acid. Esters of lomatin (Ib and c) also yielded dihydro-oroselone (II), but the dehydration product seselin (IV) did not undergo this reaction. Mechanisms are discussed.