Photolysis of 2-azi-2-deoxy-D-arabino-hexitol and analogous hexitols; the ineffectiveness of certain carbohydrate diazirines as photoaffinity labels

Article abstract of DOI:10.1016/0008-6215(93)84209-O

Three diazirines 2-azi-2-deoxy-D-arabino-hexitol (4), its 1-deoxy analogue (5), and 3-azi-3,6-dideoxy-L-xylo-hexitol (9) were synthesised and their products of photolysis analysed by TLC.Diazirine 4 gave exclusively 2-deoxy-D-arabino-hexose (12), 5 gave predominantly 1,2-dideoxy-D-erythro-3-hexulose (10) and 1-deoxy-D-glucitol (11), and 9 did not yield any main product.Carrying out the irradiation of 4 in D2O gave selectively (2S)-2-deoxy-D-arabino-(2-2H)hexose (12a).The results indicate that photolysis of a diazirine flanked by a hydroxymethyl group, as in compound 4, leads to a rapid and stereoselective intramolecular reaction of the intermediate.This may be an explanation of why compound 4 is ineffective as a photoaffinity reagent for mannitol permease (D-mannitol-specific enzyme II) of the E. coli phosphotransferase system for which it is a substrate.A secondary hydroxymethylene group has a less pronounced effect and still allows some reaction with the medium.