Pentose 5-amino-5-deoxy

The furoisoxazoline (8) has been used for the total synthesis of amino-deoxy pentose and pentitol derivatives, synthesis of the latter being outlined in Scheme 5. ... 

Calcium bis(2-amino-2,3,4-trideoxy-L-gZycero-pentarate) (calcium di-L-glutamate), tetrahydrate D-Arabinono-1,4-lactone Calcium L-arabinonate, pentahydrate Strontium L-arabinonate, pentahydrate Barium D-ribose 5-phosphate, pentahydrate 2-Deoxy-D-en/thro-pentose j8-DL-Arabinopyranose... 

Tables V-LVII detail H and F shift and coupling information, and Tables LVIII to LXXI incorporate the C-n.m.r. data. The data within this compilation are arranged according to the following outline hexoses prior to pentoses, followed by anhydro sugars, sugar acids and lactones, amino sugars (and their synthetic, A -containing precursors), mono-, di-, and tri-deoxy sugars, branched derivatives, ketoses, polyfluorinated monosaccharides, and, finally, difluorinated amino sugars. Within this compilation, and even within each table, pyranoid derivatives are listed prior to their furanoid counterparts, hexoses prior to pentoses, functionalized prior to deoxy compounds the arrangement within each sub-table is made alphabetically.

Piperidines are obtained from 5-amino-5-deoxy sugars by cycliza-tion with C-l their preparation therefore follows the general methods of preparation of such amino sugars. The 5-O-p-tolylsulfonyl- or 5-0-(methylsulfonyl)-pentoses constitute excellent starting-materials, as these sulfonyloxy groups can be replaced by azide, and the azides can be reduced to the 5-amino derivatives, which are capable of cyclization.240-251 The formation of piperidine 178 from 5-O-p-tolyI-sulfonyl-L-arabinose diethyl dithioacetal240 (176) and 177, and of 181 from benzyl 2,3-0-isopropylidene-5-0-(methylsulfonyl)-a-D-lyxofuranoside250 (179) and 180, are examples of this reaction sequence. 

It is possible to degrade 2-amino-2-deoxyhexoses to 2-amino-2-deoxy-pentoses by means of chain-shortening reactions from the nonreducing end of the molecule. Thus, Wolfrom and Anno38 converted ethyl 2-acetamido-2-deoxy-1 -thio-a-d-glucofuranoside (XV) into 2-amino-2-deoxy-a-D-xylose hydrochloride (XVI) by sequential application of periodate oxidation, borohydride reduction, and hydrolysis, as in the following reaction scheme. 

Mode of synthesis A. cyanohydrin, by way of 2-nmino-2-deoxy-aldonic acid B. scission of sugar derivative epoxide with ammonia C. interconversion of hexosamine series D. hemihydrogenation of a-amino nitrile466 E. rearrangement of ketosyl-amine F. Removal of last carbon atom of hexosamine G. Hydrazinolysis (with inversion) of 2-0-tosyl-pentose. 6 Physical constants taken from this reference. c Derivatives (only) isolated. 

In a very imaginative piece of research Frost and coworkers have developed a plasmid-based method for synthesizing aromatic amino acids, by incorporating the genes that code for the enzymes that perform the series of conversions from D-fructose-6-phosphate to D-erythrose-4-phosphate to 3-deoxy-D-arabinoheptulosonic acid-7-phos-phate (DAHP) near each other on a plasmid that can be transformed in E. coli. The enzymes are the thiamin diphosphate-dependent enzyme transketolase in the nonoxida-tive pentose shunt and DAHP synthase. The DAHP is then converted to the cyclic dehydroquinate, a precursor to all aromatic amino acids L-Tyr, L-Phe and L-Trp165,166 (equation 27). 

The 5-acetamido-5-deoxypyranoses obviously cannot be obtained from the equilibrium mixture without loss, as a part disappears because of furanose formation. Especially with the riho and arabino compounds, where the proportion of pyranose is very small, the possibility remains of proceeding from the nonacetylated 5-amino-5-deoxy-pentoses. This procedure is based on the essentially higher nucleo-philicity of the amino group, in alkaline solution, and this effect strongly favors the pyranose form (see Section II, 1 p. 130). The compound can be fixed in the pyranose form by N-acetylation under controlled conditions. In this way, a higher content can be obtained of 5-acetamido-5-deoxypentose for example, about 75% with 5-acetamido-5-deoxy-D-ribopyranose and 60% with 5-acetamido-5-deoxy-D-arabinopyranose. Care must, indeed, be taken that the reaction conditions are such as to cause the least equilibration possible. 

Pentose, 5-amino-5-deoxy-, 119 —, 5-amino-3,5-dideoxy-D-en/thro-, 130 —, 2-deoxy-5-thio-D-eri/t/iro-, oxidation of, 214... 

The first question concerns the nature and relative proportions of constituent monosaccharides. In principle, this is obtained by acidic hydrolysis (Biermann 1988) but, in practice, it must be carefully applied as there are a certain number of important specific cases. Hydrochloric, sulfuric, and trifluoroacetic acids are used whose 1 N solutions have a pH of 0.1, 0.3, and 0.7, respectively. When hydrolysis liberates monosaccharides fragile in an acidic medium, a delicate balance between the risk of incomplete hydrolysis and partial destruction of the hydrolysis product must be maintained. The fragile sugars are pentoses, deoxy sugars, and uronic and aldonic acids. When sialic acid is kept for 30 min at 90°C in 0.01 M HCl, 20% decomposition occurs. With neutral polysaccharides, decomposition can be limited to less than 9%. The acetyl groups of acetamides are hydrolysed and relatively stable protonated amino sugars are obtained. 

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