Isocyano-sugars

The structure of dehydro-L-ascorbic acid bisphenylhydrazide has been shown to be (36) by i.r. and u.v. studies. The rate of acid-catalysed elimination ofp-nitro-aniline from p-nitrophenylhydrazones in aqueous and non-aqueous media has been studied in connection with osazone formation. The rate of reaction is proportional to the concentration of acid and the p-nitro-group tends to retard the reaction. Higher yields of osazones are obtained in non-aqueous media.  

Gomez Guillen, J. A. Galbis Perez, J. I. Remon Alvarez-Arenas, and J. L. Jimenez 

Delgado, and H. Simon, Indian J. Chem., Sect. B., 1978, 16B, 469 (Chem. 

Oxidation of the p-nitrophenylhydrazine (38) derived from 1,2 5,6-di-O-isopropylidene-0i-D-n/)0-hex-3-ulose with lead tetra-acetate gave the 3-C-(p-nitrophenyldiazo)glucofuranose (39) exclusively, with none of the a//o-isomer. A number of other hydrazones were similarly oxidized, the reactions in most cases showing a high degree of stereoselectivity.  

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Photochemical a-addition of a nitrene to 1-isocyano sugars leads to the carbodiimide which adds water yielding glycosylurea or malonic acid to form potential glycosyl-barbiturate synthons [57] (Scheme 29). 

A novel method for the reductive deamination of amino-sugars has been published by Barton s group. The process involves sequential iV-formylation, dehydration to the isocyano-derivative, and reduction with tributylstannane. Application of the reaction to l,3,4,6-tetra-C>-acetyl-2-amino-2-deoxy-/3-D-gluco-pyranose afforded 2-deoxy-D-glucose tetra-acetate in 72% yield. 

Condensation of pentodialdo-l,4-furanose derivatives with ethyl isocyano-acetate has been used to prepare 6-amino-6-deoxyhepturonic acid derivatives, illustrated in Scheme 7 corresponding 5,6-unsaturated and 6-deoxy sugars were also synthesized conventionally. ... 

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