C-Glycosyl phosphonates

Stereoelectronic effects can be invoked for the radical reaction at anomeric centre of carbohydrates. The high stereoselective preparation of a-substituted C-glycosyl phosphonates in a a p ratio of 98 2 was achieved by reductive addition of bromide 2 to a-phosphonoacrylate (Reaction 7.5) [10]. Yields (in parentheses) depend on the sugar configuration D-galacto (80%), D-manno (47 %), D-gluco (30 %) and L-fuco (62 %). 

C-glycosyl phosphonates are important inhibitors of enzymes [87]. An interesting approach to such derivatives was proposed recently [88],... 

Junker, H.-D., Phung, N., and Fessner, W.-D., Diastereoselective free-radical synthesis of a-siibsliliilcd C-glycosyl phosphonates, and their use as building blocks in the HWE reaction. Tetrahedron l tt., 40, 7063, 1999. 

The phase transfer-catalysed synthesis of carbohydrate 1,2-epoxyphosphonates (e.g. 2) has been achieved, and the C-glycoside phosphonate 3 has been described. The related phosphonate 4 has been synthesized from D-mannose as an analogue of L-/nyo-inositol 1,4,5-trisphosphate and the glycosyl phosphonate 5 has been prepared as an analogue of KDO. Some glycal methylphosphonates (e.g, 6) have been synthesized as precursors to potential glycosyltransferase inhibitors (see Chapter 13 for details of synthesis), and some 2, 3 -dideoxy-3 -C-phosphononucleosides are mentioned in Chapter 20. 

Behr, J.-B., Evina. C.M.. Phung, N., and Guillerm, G., Synthesis of (difluoromethyl)phosphonate azasugars designed as inhibitors for glycosyl transferases, J. Chem. Soc., Perkin Trans. 1, 1597. 1997. 

The hetero-Diels-Alder reactions of acyl phosphonates with c-rich dienes, such as Danishefsky s diene and Brassard s diene, produced glycosyl-type phosphonates in moderate to good yields. The indium(III)-catalysed hetero-Diels—Alder reaction of a Brassard-type diene with aliphatic aldehydes produced /l-methoxy-y-methyl-a, -unsaturated (5-lactones in good yields (86%) and with high diastereo- and enantio- 0 selectivities. ... 

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