Arabino

Thiazole disulfides are reported to yield quantitatively A-4-thiazoline-2-thiones under treatment with zinc powder in acetic acid (326). The disulfide bond can be broken on heating at 100 to 260°C and (or) by alkali. This property has been used for photographic emulsions (327). The disulfide (136) (R = 4-(D-arabmo-tetrahydroxybutyD can be cleaved readily by aqueous sodium hydroxyde. carbonate, or hydrogen carbonate (149) to give 135 a by-product, 4-(D-arabino-ietrahydroxybutyl) thiazole... 

Fig. 9. Partial structural formulas and shorthand notations for principal hemiceUuloses found in wood, where the sugar units ate noted as P-D-xylopyranose (Xylp), 4-Omethyl-a-D-glucopyranosyluronic acid (GlupU), a-L-arabinofuranose (Araf), P-D-glucopyranose (Glup), P-D-mannopyranose (Manp), and P-D-galactopyranose (Galp) for (a) arabino-4-O-methylglucuronoxylan from softwood, (b) 0-acetyl-galactoglucomannan from softwood, and...

The L-arabino-(4-0-methyl-D-glucurono)xylans are found in softwoods and annual plants. The L-arabinose is present primarily as a-L-arabinofuranosyl units, although P-L-arabinopyranosyl units may also be present. In either case, the arabinosyl units are often, but not always, present as single-unit side chains, as are the uronic acid units. 

Cytarabine, 4-amino-l-/3-D-arabinofuranosylpyrimidin-2(lif)-one or cytosine arabino-side (1033 R = H, X = NH2), is an established drug for the treatment of acute leukaemias of childhood and adult granulocytic leukaemia. It must be given intravenously and much of the drug becomes the corresponding inactive uracil derivative in vivo by virtue of a deaminase in the liver it interferes with DNA but not RNA synthesis, and it has incidental... 

In extending this direct method of synthesis, we next investigated the possibility of preparing similarly constituted halides from 2-deoxy-D-arabino-hexose (2-deoxy-D-glucose) (21). The hexose was subjected to a partial anomerization procedure described by Bergmann and co-workers (1). The solid material obtained by this procedure is a mixture of the anomeric forms of 2-deoxy-D-arabino-hexose low temperature p-nitro-benzoylation of the latter in pyridine resulted in a mixture of crystalline, anomeric tetrakis-p-nitrobenzoates in a ratio of approximately 1 1. They were readily separable by fractional recrystallization, and treatment of either with an excess of hydrogen bromide in dichloromethane, or with... 

The bromide (2a) reacted smoothly with 2,4-diethoxy-5-methylpyrimi-dine to give, after de-ethylation and deacylation, l-(2-deoxy-/ -D-arabino-hexopyranosyl)thymine (3) (15). The new nucleoside (3) is the first truly competitive inhibitor of a pyrimidine phosphorylase (7), that is, it inhibits the phosphorylase, yet is not a substrate for the enzyme. It was recently shown that 3 enhances the incorporation of 2 -deoxy-5-iodouridine in vivo in cats (8). 

The bromide (2a) reacted also with chloromercuri-N-benzoyladenine to give, after debenzoylation, 9- (2-deoxy-/ -D-arabino-hexopyranosyl) -adenine (15). A later paper reported (18) on the coupling of 2a with... 

Acetyl-5-deoxy-5-iodo-l, 2-O-isopropylidene-p - l - arabinofuranose (38). Acetylation of 5-deoxy-5-iodo-l,2-0-isopropylidene-/ -L-arabino-furanose (37) (27) in pyridine as described above for the D-xylo-isomer afforded the 3-acetate (38) as a colorless sirup which did not crystallize. [ ]D24 + 13.7° (c, 3.5). Anal Calcd. for C10H15IO5 C, 35.1 H, 4.4. Found C, 35.0 H, 4.5. 

From 1,2-0-isopropylidene-3,5-di-0-tosyl-/ -d-xylofuranose (21) (29). Treating 29 with silver fluoride in pyridine and isolating as described above for the l-arabino isomer gave a 40% yield of 32 after a reaction time of 48 hours. The product had [ ]D25 — 14.9° and had an infrared spectrum identical with material prepared as above. 

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. 

Deoxyhex-5-enose derivatives. 120 2-Deoxy-D-arabino-hexopyranose,... 

Deoxy-2,3-0-isopropylidene-/ -D-fhreo-hexulo-5-enofuranose 130, 6-Deoxy-2,3-0-isopropylidene-/ -D-arabino-hexuto furanose. . 131, 6-Deoxy kanamycin. ... 

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