Xylose diethyl dithioacetal

Enzymic syntheses are considered next. Xylitol is a substrate for sheep-liver L-iditol dehydrogenase, a NAD-linked enzyme. 1-Deoxy-D-xylitol, prepared by Raney nickel reduction of D-xylose diethyl dithioacetal in a 27% overall yield from D-xylose, was also reported31 to be a substrate, although with a higher Km and lower Vmax. The product was assumed to be l-deoxy-D-f/ireo-pentulose because of the appearance of a yellowish fluorescent spot when a chromatogram was sprayed with acidic 3,5-aminobenzoic acid, resembling that formed from 1 -deoxyfructose. There was no more-rigorous characterization. 

Dithioacetal derivatives have also been employed56 in reactions with 23. The primary hydroxyl group in 2,3 4,5-di-0-isopropylidene-D-galactose diethyl and dibenzyl dithioacetals is readily replaced by iodine, to give the expected 6-deoxy-6-iodo derivatives in almost quantitative yields. The secondary hydroxyl group in 5-0-benzoyl-2,3-0-isopropylidene-L-arabinose diethyl dithioacetal (32) was similarly replaced by iodine to give 5-0-benzoyl-4-deoxy-4-iodo-2,3-O-isopropylidene-D-xylose diethyl dithioacetal (33) however, a rearranged product, namely, 4-0-benzoyl-5-deoxy-5-iodo-2,3-0-iso-propylidene-L-arabinose diethyl dithioacetal (34) was also produced. 

Acid hydrolysis of 2,4 3,5-di-0-isopropylidene-D-xylose diethyl dithioacetal to give63 the 2,4-acetal afforded a rare opportunity to establish that, in isopropylidene acetals, as with acetals derived from aldehydes, f3-erythro rings are more stable than /3 rings. 

O-isopropylidene-D-xylose diethyl dithioacetal.7 The same reaction was observed for 2-deoxy-D-arafoino-hexopyranose and 4,6-dichloro-4,6-dideoxy-D-galactopyranose, giving acetals 16 and 17, respectively. 

H. Zinner, G. Rembarz, and H. Klocking, Isopropyliden-verbindungen der D-arabinose-mercaptale, Chem. Ber. 90 2688 (1957) P. A. J. Gorin, Acetonation of aldose diethyl dithio-acetals. Can. J. Chem. 43 21X18 (1965) D. G. Lance and J. K. N. Jones, Acetonation of D-xylose diethyl dithioacetal, Can. J. Chem. 45 1533 (1967). 

The same diamino sugar was also prepared through treatment of 5-azido-5-deoxy-2,3-0-isopropylidene-4-0-(mediylsulfonyl)-D-arabi-nose diethyl dithioacetal with sodium azide. Besides the normal reaction product of Sjv2 substitution, namely 4,5-diazido-4,5-dideoxy-2,3-0-isopropylidene-L-xylose diethyl dithioacetal, there was obtained a small proportion of 4,5-diazido-4,5-dideoxy-2,3-0-isopropyli-... 

Tri-O-benzoyl-D-xylose diethyl dithioacetal reacts with eth-anethiol plus acid to form a 2-S-ethyl-2-thio-D-pentose diethyl dithioacetal137 of undetermined stereochemistry in view of the common stereochemical arrangements about C-l-C-4 in the D-gluco and D-xylo structures, this product probably has the D-lyxo arrangement. 

Location of substituents is often facilitated by the occurrence of a series of ions arising by scission, in turn, of each of the carbon-carbon bonds that do not involve a methylene group along the chain the differences in mass number of these fragments identify the substituents of each atom in turn. Thus, 4,5-bis(acetamido)-4,5-dideoxy-L-xylose diethyl dithioacetal (202) exhibits a molecular ion at m/e... 

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. 

Scheme 58. Cleavage patterns of 4-acetamido-4,5-dideoxy-D-xylose diethyl dithioacetal, 51, 4,5-diacetamido>4,5-dideoxy-L-xylose diethyl dithioacetal, 52, and 3,6-diacetamido-3,6-dideoxy-D-altrose diethyl dithioacetal, 53.

Tetra-Ac 2,3,4,5-Tetra-O-acetyl-o-xylose diethyl dithioacetal [7226-49-5]... 

Isopropylidene 2,5-O-Isopropylidene-D-xylose diethyl dithioacetal C12H24O4S2 296.451... 

Cyclohexylidene 2,5-O-Cyclohexyli-dene-D-xylose diethyl dithioacetal C15H28O4S2 336.516... 

Cyclohexylidene-D-xylose diethyl dithioacetal, X-83 2-[(Cyclohexylmethylene)hydrazino]adenosine, B-33 Cycloinulohexaose, C-180... 

Di-0-benzoyl-2-0-metbyl-p-D-xylopyranosyl fluoride, X-16 l,2 3,5-Di-0-benzylidene-a-D-xylofuranose, X-81 2,4 3,5-Di-0-benzylidene-D-xylose diethyl dithioacetal, X-83... 

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