Pentitols 1,4-anhydro-, preparation

Attempts to prepare esterified glycals by the reduction of glycofuranosly halides with zinc in acetic acid failed, because of the reactivity of this class of compound (see p. 92). When, however, 3,5-di-0-benzoyl-2-0-(p-nitrophenylsulfonyl)-/3-D-ribofuranosyl bromide (8) in acetone is treated at 5° with sodium iodide, a facile elimination takes place and 3,5-di-O-benzoyl-1,2-dideoxy-D-er2/i/iro-pent-l-enofuranose (9) is obtained crystalline, in 72% yield. The product was characterized by identifying its hydrogenation product as the known l,4-anhydro-3,5-di-0-benzoyl-2-deoxy-D-er2/nuclear magnetic resonance spectrum, which showed clearly that the glycal structure was present. 

Deoxy-5-seleno-D-arabino-, D-ribo- and D-xylo-selenoformates 8, 9 and 10 have been prepared from D-arabinose and known 2,3,4-tri-O-benzyl-D-ribose and -D-xylose diethyl dithioacetals, respectively/ The thermolysis of these compounds to afford l,5-anhydro-5-deoxy-5-seleno-D-pentitols is covered in Chapter 11. 

Anhvdro-Alditols. - The synthesis of a whole range of 1,5- and 1,4-anhydro-alditols and their inhibitory effects against glycosidases have been reported. The preparation of 2,5-anhydro-3-deoxy-D-araWno-hexitol by hydrogenation of 2,5 3,4-dianhydro-D-allitol over Pearlman s catalyst has been described. The selective chlorination of pentitols to afford l,5-dichloro-l,5-dideoxy derivatives as well as mono- and di-chloro-l,4-anhydro derivatives has been reported. ... 

Di-anhydro-pentitols (14) and (15) have been prepared from 1,4-anhydro-5-chloro-5-deoxy-D-arabinitol and -D-xylitol respectively, and another paper has described a similar synthesis of the L-enant-iomer of (15) together v ith oxetans of 2,5-anhydro-hexitols and the dioxetans (16) and (17), ... 

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