L-Arabinal

Also, di-O-acetyl-L-arabinal was converted into the corresponding anhydro-L-ribitol derivative (see also, pp. 195-197). 

An aldonic acid dehydratase was partially purified,290 and found to convert D-fuconate into 3-deoxy-D-t/ reo-2-hexulosonate, and L-arabin-onate into the corresponding 3-deoxy-L-gZi/cero-2-pentulosonate. It did not act on L-fuconate or on D-galactonate. 

Fio, 1.—Curves for Light-absorption in the Dische Test (o) 2-Desoxy-D-ribose (61) D-Arabinal (i2) L-Arabinal (c) Furfuryl alcohol (d) w-Methoxylevulinaldehyde Dimethyl Acetal (e) Sodium Thymonucleate (/) Methyl 2-desoxy-/3-n-ribopyrano-side (g) Methyl 3,4-Dimethyl-2-desoxy-/3-L-ribopyranoside. 

If the glycal is treated with a 2-3 percent solution of hydrogen chloride in methanol instead of with dilute aqueous acid, then the methyl glycoside of the 2-desoxysugar is obtained. In this way L-arabinal was converted into methyl 2-desoxy-/3-L-ribopyranoside,141 D-glucal into methyl... 

Since deacetylation of LXXXII and subsequent ozonization and treatment with water afforded glyoxal (isolated as the phenylosazone) it followed that the ethylenic linkage must be between carbon atoms 2 and 3.204 Reduction of LXXXII, followed by deacetylation, yields ethyl 2,3-didesoxy-D-alloside (LXXXIII). Alternatively, LXXXI could be converted into 4,6-diacetyl-2,3-didesoxy-D-allose, which on glycosidation as above yielded ethyl 4,6-diacetyl-2,3-didesoxy-D-alloside. In this instance the product was a mixture of isomers, since on deacetylation, two forms (m. p. 72-72.5° and 90°, respectively) were isolated. Derivatives of 2,3-didesoxy-L-ribose81 have been prepared from 3,4-diacetyl-L-arabinal,... 

Diacetyl-L-arabinal adds two atoms of chlorine easily. By the use of moist silver oxide one of the chlorine atoms is readily replaced by a hydroxyl group. The resulting 2-chloro-2-desoxy-3,4-diacetylpentose (XLI), when treated with lead oxide (PbO), isomerizes with simultaneous deacetylation to 2-desoxy-L-arabonic acid (XLII).36... 

Standard Solution Transfer about 25 mg each of L-arabin-itol, galactitol, mannitol, and sorbitol, accurately weighed, into a 100-mL volumetric flask, dilute to volume with water, and mix. Add an accurately weighed amount of USP Xylitol Reference Standard to an accurately measured volume of this solution to obtain a solution with a known concentration of Xylitol of about 49 mg/mL. 

Klaflfke developed a scaleable three step synthetic method to prepare uridine diphospho-D-xylose and UDP-L-arabinose from D-xylal and L-arabinal respectively and The synthesis of ADP- h-glycero- and T>-glycero-... 

Synthetic 2-desoxy-L-ribose (-L-arabinose), prepared by the action of dilute sulfuric acid on L-arabinal (L-ribal), had the same numerical values of initial and equilibrium specific rotation (but opposite sign) as had the sugar of thymus nucleic acid. Hence the sugar was identified as 2-desoxy-D-ribose. On treatment with dilute sul-... 

The observation that L-arabinal adopted the conformation exclusively and that the and conformations of o-glucal were comparably populated led Curran and Suh" to propose a vinylogous anomeric effect , similar to the anomeric effect. Additional stabilisation of an electronegative substituent in an axial orientation was available from a p-type lone pair on oxygen, separated by a double bond, via overlap of the C X a orbital and v /2 of the enol ether (Figure 6.70). No experimental estimates of its magnitude are available, but it is likely to be smaller than the anomeric effect itself, not least because any electrostatic component is much smaller. 

As reported earlier,1 acetylated glycals can give unsaturated nucleoside derivatives when condensed with bases. Examples of related compounds were obtained when di-O-acetyl-D-xylal or -L-arabinal were treated with benzotriazole and its 5,6-dimethyl derivative in... 

By his efficient, mild, rapid eco-friendly method, Das et al. [44] treated different per-O-acetylglycals (49a,b and i-rhamnal, 49c, and L-arabinal, 49d) with aliphatic primary alcohols, in the presence of indium(III) chloride in acetonitrile solution in an open vessel, to afford the corresponding 2,3-unsaturated products 53 in good to excellent yields in a few seconds (Scheme 12.24). 

The protected 2-formyl-L-arabinal reacted with thiourea and cyanamide in the presence of sodium hydride to afford, via ring transformations, the 5- [ lR,2S-l,2-bis(benzyloxy)-3-hydroxypropyl]- 1,2-dihydropyrimidines. Similarly, treatment with 3-amino-2H-1,2,4-triazole yielded 6-[lR,2S-l,2-bis(benzyloxy)-3-hydroxypropyl][l,2,4]-triazolo[l,5-a]pyrimidine [151]. Reaction of 27 with 2-aminoimidazole and 2-aminobenzimidazole gave 96 and its bezo-analogues [64]. 

L-Rhamnal, L-Arabinal, D-Xylal, L-Fucal, D-Allal Scheme 29... 

A variety of methods have been used for the preparation of 2-amlno-2-deoxypentose derivatives of different configurations. Products with the D-xylo- and L-arabljTO-configurations were derived by azldonltratlon of D-xylal and L-arabinal esters, respectively. The D-xylo-product was converted into its D-rlbo- and D-lyxo-isoraers by C-3 oxidation-reduction, and formation and opening of a... 

D. The Effect of Mutations in Genes araA, araB, and araC on L-Arabin-... 

Di-O-acetyl-L-arabinal, A-790 A iV-Diacetyl-D-arabinosylamine, A-854 A iV-Diacetyl-L-arabinosylamine, A-854... 

The oxidation of the double bonds of glycals by ozone furnishes an additional method for shortening the carbon chains of the sugars 208), The oxidation of L-arabinal to L-erythrose provides an example 209),... 

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