Pentitols 1.5- anhydro

However, if the reasons already given for the differences in ease of anhydridation of the pentitols are valid, 1,4-anhydro-D-arabinitol (8) should be the chief product, because, in 7, not only would there be a transannular, nonbonded interaction between the hydroxymethyl group and the 2-hydroxyl group, but the (bulky) hydroxymethyl group and the 3-hydroxyl group would be in eclipse. 

On heating pentitols with acid under more drastic conditions, derivatives of 1,4-anhydrides may be produced. Thus, on treating molten xylitol with dry hydrogen chloride at 100°, or in concentrated hydrochloric acid at 106-108°, a moderate yield of syrupy 1,4-anhydro-5-chloro-5-deoxy-DL-xylitol was obtained.16... 

In a detailed study of the deamination of the four 1-amino-1-deoxy-D-pentitols (109-112), the products were analyzed by g.l.c. It was found that each aminodeoxypentitol gives three products in differing ratios.202 In addition to the pentitol and the corresponding 1,4-anhydropentitol, there is formed a second 1,4-anhydropentitol. The latter was found to be formed by ring closure between the 5-hydroxyl group and C-2, with inversion at C-2. For example, 1-amino-1-deoxy-D-lyxitol gives 1,4-anhydro-D-lyxitol, 2,5-anhydro-D-xylitol (= 1,4-anhydro-L-xylitol), and D-lyxitol. Because the second 1,4-... 

With the aid of these rules, we have predicted the structures of the acetals which would be expected to result from the benzylidenation, ethylidenation and methylenation of all the tetritols, pentitols and hexi-tols. As will be seen from Table IV, the predicted structures agree very well with the accepted structures of the compounds. The rules explain, too, the syntheses of 3,5-benzylidene- and 3,5-methylene-gluco-[Pg.180]

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. 

Pentitols, for example D-arabinitol, reacted with thionyl chloride in pyridine at — 30 °C and gave the corresponding l,2 4,5-di-0-cyclic sulfites which reacted further with sodium azide in dimethyformamide affording a small quantity of anhydro derivative 17 together with the expected 1,5-diazido-dideoxy-D-arabi-nitol as major product. ... 

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. 

Anhydro-2-deoxy-pentitol 26 was synthesized in four steps from 5-ben-zyloxy-pent-2-en-l-ol as an intermediate in the synthesis of a y-amino-p-hydroxy acid component of the cyclic depsipeptide, hapalosin. ... 

Condensation of thiodiglycolaldehyde and diglycolaldehyde with t-butyl cyanoacetate gave corresponding anhydro-pentitol derivatives, e.R.. (54), together with the 1 2 adducts, e.g., (55) ... 

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