3- Deoxy-D-arabino-hexose

On applying the Kiliani cyanohydrin synthesis to 2 deoxy-i>-erythro-pentose, Wood and Fletcher127 obtained crystalline 3-deoxy-D-ribo-hexose and 3-deoxy-D-arabino-hexose (as the dithioacetal). Interesting comments concerning the course of the Kiliani synthesis were made by these authors. Condensation127 of 2-deoxy-D-erj/(Aro-pentose with nitromethane gave epimeric 1,3-didcoxy-l-nitrohexitols which, after hydrolysis under Nef... 

For example, it was possible to demonstrate formation of the modified polysaccharides of S. anatum in which a D-galactose residue is replaced by D-fucose, D-gluc-ose, D-talose, or 4-deoxy-D-xylo-hexose residues. 3-Deoxy-D-arabino-hexose or P-glucose residues may substitute for a P-mannose residue. 

Not unexpectedly, a-eliminations are also observed with sugar lactones (Section 6.2). Thus treatment of D-glucono-l,5-lactone 6.32 with an excess of benzoyl chloride and pyridine for 16 h at room temperature gives the crystalline elimination product 6.33 in quantitative yield. Catalytic hydrogenation then led to the benzoylated 3-deoxy-D-ara6i>io-hexono-l,5-lactone 634 ftom which 3-deoxy-D-arabino-hexose was obtained in two steps (de Lederkremer and Varela 1994). 

The importance of the presence of the OH group at C-4 for an unambiguous course of the molybdate-catalyzed epimerization was further shown in studies with trioses [19,20], 4-deoxy-D-lyxo-hexose and several other 4-0-substituted derivatives of aldoses [20]. Much more important is the OH group at C-3 which is essential for the Bflik reaction. Its absence causes a quite different structural change in both 3-deoxy-D-arabino-hexose (1) and 3-deoxy-D-n fco-hexose (2) under otherwise the same reaction conditions both sugars on treatment with molybdic acid are irreversibly transformed to 3-deoxy-D-eryf/zro-hex-2-ulose (3, Scheme 2) [21]. 

The reaction of 2-deoxy-D-arabino-hexose (26) and Cr(VI) results in the formation of two oxo-Cr(V) species with giso= 1.9781 and 1.9754 in 2 6 ratio, independently of the pH and concentration of 26.85The two species disappear at comparable rates, meaning that these Cr(V) intermediates are in rapid equilibrium compared to the timescale of their subsequent reduction to Cr(III). The analysis of the EPR parameters indicates that the signals can be assigned to Cr(V)-bis- and monochelates formed with the substrate, namely [Cr0(03,04-26)(01-26)(H20)] and [Cr0(01-26)(H20)3]2+.50... 

Deoxy-D-arabino-hexose 3% HiEff8-BP 200 synthesis of 2-deoxy-L-erythro-and -D-fhreo-pentose 390... 

Deoxy-D-arafnno-hexose (55) was treated in methanol with hydrogen chloride according to a procedure79 which was purported to yield almost exclusively a mixture of the anomers of methyl 2-deoxy-D-arabino-hexofur anoside. It has now been shown78 that the latter consists, in fact, of an anomerically pure methyl 2-deoxy-D-arabino-hexofuranoside (77), plus substantial proportions of an approximately 1 1 mixture of methyl 2-deoxy-a- and jS-D-orabmo-hexopyranosides (78) and (79), and unreacted 2-deoxy-D-arabino-hexose (55). p-Nitrobenzoylation of the sirupy, quadripartite mixture led to a mixture of p-nitrobenzoic esters from which, by fractional recrystallization, there was obtained in pure form a methyl 2-deoxy-3,5,6-tri-O-p-nitrobenzoyl-D-arabino-hexoside (80). Attempts to replace, directly, the severely hindered methoxyl group at C-l of (80) by halide failed. 

Selective oxidation at C-2 of 3-deoxyaldonic acids by the action of sodium perchlorate in the presence of vanadium pentaoxide has been used for the preparation of deoxyketoaldonic acids, although low yields of pure compounds are obtained. The necessary 3-deoxyaldonic acids may be prepared by a cyanohydrin chain-extension reaction. Several syntheses have been reported for 3-deoxy-D-araZu rao-hept-2-ulosonic acid starting from 2-deoxy-D-arabino hexose 310,311 DAHP (122) has also been similarly prepared.312... 

SYNS 2-DEOXY-d-ARABINO-HEXOSE 2-DEOXY-3-ARABINO-HEXOSE d-2-DEOXYGLUCOSE 2-DEOXY-d-GLUCOSE 2-DEOXY-d-GLUCOSE (FRENCH) 2-DG NSC-15193... 

From the results of an investigation of certain glycosides of 2-deoxy-D-arabino-hexose and 2,3-dideoxy-D-er2/<)iro-hexose, Stacey and coworkers concluded that (o) pyranosides of 2-deoxyhexoses are more stable than those of the corresponding 2-deoxypentoses, (5) the 2-deoxyglycofurano-sides are much more labile than the 2-deoxyglycopyranosides, and (c) an increase in the number of methylene carbon atoms in the glycose residue increases the ease of hydrolysis. 

In a study of the deacetylation of acetylated sugar osazones it has been shown that under alkaline conditions and depending upon the substrate, either an external nucleophile fe.a.. Na, MeO , NH3) can be incorporated at C-3 or a 3,6-anhydride can be formed. The 3-methoxy-epimers (49) were thus formed from the L-ervthro-pentose osazone triacetate presumably by formation and 1,4-addition to a phenylazo-ene intermediate." The 2-acetoxy group of aldose diphenylformazan peracetates is also readily displaced. 2-Deoxy-D-arabino-hexose diphenylformazan (50) was thus formed when penta-Q-acetyl-D-glucose or -D-mannose H H diphenylformazan was treated with sodium borohydride." ... 

Several features of the rearrangement have been elucidated. Although in the treatment of the ester 26 with acetic acid the products were isolated in only 64% yield, evidence was obtained (22) that finally no 1,2-unsaturated compounds remained, since the noncrystalline portion on hydrogenation and deacetylation afforded only 3-deoxy-D-ribo and -d-arabino-hexose and no 1,5-anhydrohexitols. That the components of the final mixture were in equilibrium was indicated by the observation that the main component 27 underwent reaction in boiling acetic acid to give a solution with the same optical activity as that of the original reaction mixture. Thus the 2,3-unsaturated compounds are more stable than the hydroxyglycal derivatives and the a isomer 27 is more stable than its anomer 28. 

The 3-deoxyhexoses were obtained crystalline after separation on a column of cellulose, a rather tedious operation recently separation of these sugars by fractional crystallization has been reported (41). From the major unsaturated ester 27, 3-deoxy-D-ribo- and -arabino-hexose were shown to have been produced respectively in the ratio 66 34, and from ester 28 in the ratio 24 76. Saturation of the enol grouping of the esters 27 and 28 gives, therefore, the 1,2-cis products preferentially. However, some hydrogenolysis of the anomeric acetate group accompanies simple saturation of the double bond and poses another separation problem. 

Catalytic hydrogenation of methyl (methyl 4-deoxy-/3-L-lAreo-hex-4-eno-pyranosid) uronate afforded methyl (methyl 4-deoxy-0-i<-ara Mio-hexo-pyranosid) uronate as the main product.136 Reduction of this compound gave a mixture of 4-deoxy-n-arabino-hexose and its 1,6-anhydride. Thus, the tendency of deoxy-ara trao-hexopyranoses to give 1,6-anhydrides10 extends to the 4-deoxy sugars as well. A minor product of the hydrogenation136 was assumed to be the epimeric (at C-5) methyl (methyl 4-deoxy-a-D-xylo-hexopyranosid) uronate. 

---