Synthesis of Deoxysugars

The synthesis of 6-deoxy-D-glucose (see D-Quinovose, p, 99) is carried out from 2,3,4-tri-0-acetyl-6-bromo-6-deoxy-a-D-glucosyl bromide. The dihalide is converted to the methyl 2,3,4-tri-0-acetyl-6-bromo-6-deoxy-i -D-glucoside by treatment with silver carbonate and methyl alcohol, and the bromine is exchanged for a hydrogen atom by reduction with zinc and acetic acid 227). 

A method of more general application depends on the reduction of iodo derivatives in which the iodine has replaced the hydroxyl of a primary alcoholic group. These are easily obtained by treatment of the tosyl derivatives with sodium iodide in acetone solution (sealed tube) or in refluxing acetonyl-acetone 228) or acetic anhydride 229). The reduction is often carried out by catalytic methods. The 5-deoxy-n-xylose is synthesized from D-xylose by this method, and by application of the cyanohydrin synthesis 6-deoxy-n-gulose is prepared 230). 

5-deoxy -5-iodo -mono -0 -isopropy lidene -d -xylose 

5-deoxy-mono-O-isopropylidene-D-xylose —5— 5-deoxy-D-xylose  

The tosyloxy group also may be replaced by the thiocyanate group and the latter then removed reductively to give the deoxysugar ( 5f). 

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Z. Pakulski and A. Zamojski, The reaction of acetyliron ((i 5-C5H5)Fe(CO)(PPh3) (COCH3)) with sugar aldehydes. New synthesis of deoxysugars, Tetrahedron, 51 (1995) 871-908. 

The synthesis of deoxysugars, both terminal and nonterminal, has been widely studied and applied by Reichstein and his associates in connection with their studies of the sugar components of the cardiac glycosides (Chapter X). 

Other advances in methodology fcr synthesis of deoxysugars include the reduction of triflatc esters with tetrabutylammonium borohydiide, and the same reagent was also used for reductive... 

Figure 10.25 Inverted approach for aldose synthesis using FruA catalysis, and application ofthe strategy for deoxysugar synthesis based on a phosphorothioate analog synthesis of 1-deoxysugars by FSA catalyzed addition of hydroxyacetone.

Schurmann, M., Schurmann, M. and Sprenger, G.A. (2002) Fructose 6-phosphate aldolase and 1-deoxy-D-xy lulose 5-phosphate synthase from Escherichia coli as tools in enzymatic synthesis of 1-deoxysugars. Journal of Molecular Catalysis B, Enzymatic, 19, 247-252. 

Special topics (synthesis of P-mannosides, furanosides, sialosides, glycosides of aminosugars and deoxysugars, if applicable)... 

For the synthesis of glycans containing 2-amino-2-deoxysugars, the regioselective azidophenylselenation of glycals is popular [524—528]. This methodology follows on from the classic azidonitration work of Lemieux and Ratdiffe, first reported in the... 

Asymmetric synthesis of 1-deoxysugars and sugar phosphates using DXS and/or FSA enzymes a) Me. Schtirmann, Ma. Schtirmann, G. A. Sprenger,/. Mol. 

V. Costantino, C. Imperatore, E. Fattorusso, and A. Mangoni, A mild and easy one-pot procedure for the synthesis of 2-deoxysugars from glycals, Tetrahedron Lett., 41 (2000) 9177-9180. 

J. S. Yadav, B. V. S. Reddy, K. Bhaskar Reddy, and M. Satyanarayana, CeCl3 7HzO A novel reagent for the synthesis of 2-deoxysugars from D-glycals, Tetrahedron Lett., 43 (2002) 7009-7012. 

Z. Zhao and H.-w. Liu, Synthesis of a deoxysugar dinucleotide containing an exo-difluoro-methylene moiety as a mechanistic probe for studying enzymes involved in unusual sugar biosynthesis, J. Org. Chem., 66 (2001) 6810-6815. 

The Synthesis of 2-Amino-2-deoxysugars from Acetylated Glycals, R. U. Lemieux and T. L. Nagabhushan, Tetrahedron Lett., No. 26 (1965) 2143-2147. 

T. D. Inch and G. J. Lewis, The synthesis of branched-chain, deoxysugars by sugar epoxide-Grignard reagent reactions, Carbohydr. Res., 15 (1970) 1-10. 

However, nucleoside diphosphates (NDP) are still expensive substrates, which can be obtained from much more cheaper nucleoside monophosphates (NMP). In this respect we have combined the SuSy-catalyzed cleavage of sucrose with the enzymatic formation of NDPs from NMPs catalyzed by nucleoside monophosphate kinase (NMPK, EC 2.7.4.4) or myokinase (MK, EC 2.7.4.3), including in situ regeneration of ATP with pyruvate kinase (PK, EC 2.7.1.40) (Fig. 20) [272]. Testing the substrate spectrum of four different kinases disclosed that none of them accepted dTMP as substrate [272], However, dUMP was well accepted by NMPK and dUDP-activated glucose could also substitute dTDP-activated glucose as precursor for the synthesis of activated deoxysugars (see below). The excellent enzyme stabilities under synthesis... 

Fig. 23. Enzymatic synthesis of dTDP-activated deoxysugars with dTDP-Glc 4,6 dehydratase (EC 4.2.1.46) [331]...

Scheme 5.36. Synthesis of higher 2-deoxysugars via /Je-face attack, utilizing KDO aldolase.

Diphenylphosphanyl radicals, Ph2P , generated from diphenylphosphane in the presence of a radical initiator were used to cyclize the alkynyl-substituted carbohydrate derivative 195 in a radical addition/S-exo cyclization sequence to give the bicyclic deoxysugar derivative 196 (Scheme 2.36). Ph2p have also been used as promoters for the cyclization of alkynyl p-lactam 181 for a highly efficient, diaster-eoselective synthesis of bicyclic p-lactams (see Scheme 2.33). ... 

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