Irradiation of a series of 3-acylestrones under a nitrogen atmosphere in cyclohexane, acetonitrile (MeCN), and methanol (MeOH) was investigated under steady-state conditions. The molecules underwent the photo-Fries rearrangement, with concomitant homolytic fragmentation of the ester group and [1;3]-acyl migration. This pathway afforded the ortho-acyl estrone derivatives, the main photoproducts, together with estrone. During the irradiation of 3-benzoyl estrone, epimerization of estrone through the Norrish type I reaction occurred, providing lumiestrone as the photoproduct. This photoreaction involves the fragmentation of the C-α at the carbonyl group (C-17) of the steroid. On the other hand, epimerization of ortho-regioisomer 2-acetyl estrone occurred during the irradiation of 3-acetyl estrone. Photosensitization with acetone and chemical quenching with N,N,N,N-tetramethyldiazetinedioxide of the photo-Fries reaction confirmed that the photoreaction took place from the singlet excited state while the Norrish type I reaction proceeds efficiently from the triplet excited state. Solvent effects, as well as the nature of the acyl group on the photoreactions, were also studied.

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Dedicated to Prof. Rosa M. de Lederkremer on her 70th anniversary AbsractThe synthesis of 2,3,5,6-tetra-O-benzyl-D-galactofuranose, a useful compound for α-glycosylation studies, is described. Direct anomeric O-alkylation of galactose was employed for alpha-allylation to yield pure allyl α-D-galactofuranoside, which is a versatile precursor for the synthesis of galactofuranose-containing oligosaccharides. Allyl removal of the benzylated galactofuranosyl derivative was performed using palladium (II) chloride as catalyst.