Photoreactions of fructose 6-phosphate in oxygenated and deoxygenated aqueous solutions

Abstract

The photoreactions of fructose 6-phosphate in water, irradiated at 254 nm in the presence and in the absence of oxygen (ϕ 0.60 and 0.50. respectively), were studied. The most abundant photoproducts were carbon monoxide and orthophosphate; the other main products were identified by g.l.c.–mass spectrometry of the trimethylsilyl derivatives as 2-deoxyerythrose 4-phosphate, 2,4-dihydroxycyclobutyl phosphate, and glycoraldehyde phosphate, with glyceraldehyde 3-phosphate in the presence of oxygen. These results can be explained by assuming the free carbonyl function of the sugar phosphate to be excited. Carbon monoxide is obtained in the primary process via a Norrish type I reaction. The resulting phosphorylated radical undergoes elimination of water leading to 2-deoxyerythrose 4-phosphate, which gives further important Norrish type II reactions. Orthophosphate is the result of secondary degradation processes, and also probably arises from hydrolysis of labile organic phosphates. This photochemical behaviour is in contrast with the hydrogen abstraction occurring generally with carbohydrates, in particular glucose 6-phosphate (ϕ 0.8 × 10^–2).