Carbohydrates chain extension

Ketose (Section 25 1) A carbohydrate that contains a ketone carbonyl group in its open chain form Kiliam-Fischer synthesis (Section 25 20) A synthetic method for carbohydrate chain extension The new carbon-carbon bond IS formed by converting an aldose to its cyanohydnn Reduction of the cyano group to an aldehyde function com pletes the synthesis... 

Specific degradation of the carbohydrate chain has been extensively discussed in a few articles (for reviews, see Refs. 5, 7, 8,35, and 58). In the following discussion, we shall briefly present some applications that have been valuable in the sequence study of glycoprotein and glycolipid saccharides. 

The naphtho[2,3-d]-l,3-dioxole was oxidized using recombinant E. coli whole cells overexpressing the gene for the naphthalene dioxygenase from Pseudomonas putida G7. The linear carbohydrate fragment was enzymatically formed after ozon-ization of the diol, by chain extension with a dihydroxyacetone fragment in an... 

S. Czemecki, A. Dieulesaint, and J.-M. Valery, Chain-extension of carbohydrates. I. Cyano-... 

The methods often used for the branching of carbon chain are also suitable for the chain extension of sugars at both ends (e.g., C-l and C-5/C-6). Several developments of chain extension have recently culminated in the synthesis of long-chain carbohydrates of biological interest. 

S. Hanessian and P. Dcxtraze, Preparative and exploratory carbohydrate chemistry. Carbanions in carbohydrate chemistry. Novel methods for chain extension and branching, Can. J. jChem. 50 226 (1972). 

Chain extension of aldoses takes place at the aldehyde end of the chain. The aldehyde function of an aldopentose becomes C-2 of an aldohexose, which normally results in two carbohydrates diastereomeric at C-2. Thus, (-l-)-glucose and (-r)-mannose have the same configuration at C-3, C-4, and C-5 they have opposite configurations at C-2. The configuration at C-2, C-3, and C-4 of (-)-arabinose is the same as that at C-3, C-4, and C-5 of (+)-glucose and (-r)-mannose. 

C. J. Railton and D. L. J. Clive, Wittig chain extension of unprotected carbohydrate-derived a,/S-unsaturatcd esters, Carbohydr. Res., 281 (1996) 69-77. 

S. Czernecki, S. Horns, and J. M. Valery, Chain-extension of carbohydrates. 5. Synthesis of C-glycosyl amino acid moiety of miharamycins involving stereocontrolled ethynylation of methyl 2,3,4-tri-0-benzyl-a-D-g/nco-hexadialdo-l,4-pyranoside, J. Org. Chem., 60 (1995) 650-655. 

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