Glycosyl cyanide

Several other studies concerning tetrazole-containing compounds were leptorted. The 1-bromo-glycosyl cyanide 15 was converted to the tetrazole derivative 16 in 72% yield by treatment with 2 eq LiNs/DMF/S d <96T9121>. Shorter reaction times led to formation of the 1-azido-pyranosyl cyanide. (Hydroxyphenyl) carbenes could be formed by thermal decomposition of the appropriate 5-substituted tetrazoles 17 <96JOC4462>. 

Glycosyl cyanides have been thoroughly used as starting materials in the preparation of 1-formyl, and 1-cyano-glycals, mainly through base-induced elimination procedures (Scheme 10). 

Scheme 10 Synthetic routes to 1-formyl and 1-cyano glycals from glycosyl cyanides.

Fig. 30 Synthesis of 2,3-unsaturated allyl glycosides or glycosyl cyanides...

As outlined in CHEC-II(1996) <1996CHEC-II(7)89>, furo[2,3- j-l,3,2-dioxathioles are used mainly in the synthesis of glycosides. Position ia of these systems is susceptible to nucleophilic attack. Ytterbium-catalyzed cyanation of sulfite 53 using NaCN and Yb(OTf)3 in hexamethylphosphoramide (HMPA) at 90 °C produced glycosyl cyanide 54 (Equation 7) <20040L3913>. 

Tri-0-acetyl-/ -D-ribopyranosyl and -xylopyranosyl cyanides give — 2 1 mixtures of 1 -bromo-/ - and -a-D-glycosyl cyanides, the anomers being of comparable stabilities in these cases.54 55... 

Because the aromatic rings of compounds of this class render the anomeric centers benzylic, and also conceivably subject to captodative radical stabilization, photobromination results might be expected to correlate with those observed for the glycosyl cyanides (see Section 11,6). 

Kini, G D, Petrie, C R, Hennen, W J, DaUey, N K, Wilson, B E, Robbins, R K, Improved and large-scale synthesis of certain glycosyl cyanides. Synthesis of 2,5-anhydro-5-thio-D-allonitrile, Carbohydr. Res., 159, 81-94, 1987. 

Araki, Y, Kobayashi, N, Watanabe, K, Ishido, Y, Synthetic studies by the use of fluorinated intermediates. Part 2. Synthesis of glycosyl cyanides and C-allyl glycosides by the use of glycosyl fluoride derivatives, J. Carbohydr. Chem., 4, 565-585, 1985. 

Drew, K N, Gross, P H, C-glycoside syntheses. 1. Glycosyl cyanides and isocyanides from glycosyl fluorides with full acetal protection, J. Org. Chem., 56, 509-513, 1991. 

Somsak, L, Batta, G, Farkas, I, Preparation of 1,2-cis-glycosyl cyanides by the stereoselective reduction of acetylated 1-bromo-D-glycosyl cyanides. Tetrahedron Lett., 27, 5877-5880, 1986. 

Toth, M., Somsak, L. exo-Glycals from glycosyl cyanides. Eirst generation of C-glycosylmethylene carbenes from 2,5- and 2,6-anhydroaldose tosyihydrazones. J. Chem. Soc., Perkin Trans. 1 2001, 942-943. 

Thioglycosides have received some attention over the last few years. The ethyl thio-glycoside 435 has been found to be a good substrate for the selective formation of the a-glycosyl cyanide 436 (Scheme 76) [127],... 

Nitriles by substitution. Glycosyl cyanides are formed from glycal esters (Pd-catalyzed reaction), whereas 8 2 reaction of alkyl halides requires fluoride ion to activate Me SiCN (hypervalent silicate). ... 

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