Synthesis of C-glycosyl derivatives

The go5 of this project has been to develop a general approach to the synthesis of C-glycosyl derivatives based upon an extension of our previous studies into the chemistry of aikylmanganese pentacarbonyl complexes (8-16). As summarized in Scheme 1, it has been demonstrate that simple alkyl complexes such as methylman-ganese pentacarbonyl (6) can be transformed into a variety of carbonyl derivatives with formation of either one, two, or three carbon-carbon bonds (9,10,12). 

Azidonitration of D-glycal triacetates was the first step in a synthesis of C-glycosyl derivatives of 2-amino-2-deoxy sugars which is covered in Chapter 9. yJ-o-Glucopyranoside tetranitrate and -cellobiose octanitrate are referred to In Chapter 21. 

In connection with the synthesis of C-glycosyl compounds, Moffatt and coworkers182 developed the selective debenzoylation of 2,3,5-tri-0-benzoyl-/3-D-ribofuranosyl cyanide, which had been reported earlier163 reaction in methanolic ammonia-chloroform at 0° gave the crystalline 5 -0-benzoyl derivative in 83% yield, without recourse to chromatography. 

Lakhrissi, Y, Taillefumier, C, Lakhrissi, M, Chapleur, Y, Efficient conditions for the synthesis of C-glycosylidenes derivatives a direct and stereoselective route to C-glycosyl compounds. Tetrahedron Asymmetry, 9, 417-421, 2000. 

This procedure provides a fast synthesis of C-glycosyl disaccharides with the anomeric sul-fones derived from the D-gluco, D-galacto and L-fuco series and this is presented using aldehyde 175, obtained by the five-step sequence of reactions shown in O Scheme 36. 

Tronchet, J.M.J., and Bonenfant, A.P., C-Glycosyl derivatives. Part 42. Synthesis of novel types of C-glycosyl-derivatives from acetylenic sugars or their partial synthetic equivalents. Preliminary communication, Helv. Chim. Acta, 64, 2322, 1981. 

Franck et al. [109] suggested a strategy for the synthesis of C-glycosyl benzaldehyde derivatives to be used in porphyrin preparations. They started by condensing 2,3,4,6-tetra-0-acetyl-l-thio-j6-D-glucopyranose with a,a -dibromo-p-xylene to afford thioglucoside 159 (Scheme 29). The latter, by... 

Standard methods involving glycosyl halide or ester derivatives in reaction with protected heterocycles have been applied to the synthesis of various glycosyl derivatives of 5-fluoro-uracil and -cytosine, a number of nitro-imidazoles and -pyrazoles, thiadiazines and oxadiazolo-thiadiazines, and 5-methylthio derivatives of -uracil, -4-thiouracil, and -cytosine,/3-D-ribofuranosyl derivatives of 2-thio-6-azauracil, diethyl 4-hydroxypyrazole-3,5-dicarboxylate, 5-acetyl-uraeil, 2,4- and 2,5-thiazolidinediones, 4-thiomethyl-2-azapurine, 2-hydroxypurine, 3-deaza-adenine-8- C, l-deaza-8-azaguanine, imidazo-(l,2- )l,3,5-triazenes, e.g., (5), //n-benzo-guanosine, -inosine, and -xanthosine (6), and a derivative of lV-2-(i3-D-ribopyranosyl)benzotriazoie. Likewise 2-0-... 

In a series of recent contributions, Liu and coworkers have evaluated the potential of the palladium-catalyzed decarbo)q lative reaction in the synthesis of allylic glycosyl derivatives. In this context, they described a palladium-catalyzed stereo- and regioselective C-glycosylation process based on an intramolecular decarboiq lative coupling. Initial studies with glycal derived p-ketoesters, e.g. 4, allowed the authors to identify... 

Vinyl phosphates are electron-deficient alkenes sufficiently reactive to anomeric glycosyl radicals. Fessner et al. has applied this type of reaction to the synthesis of C-glycosyl phosphate derivatives (Scheme 5). Bromoglycoside 1 undergoes C-glycosylation with diethyl vinylphosphonate in the presence of tributyltin hydride to give 9 with high a-selectivity. The use of tris(trimethylsilyl)silane, which is an... 

Bednarski has reported that this allylation reaction has been used for the key step in the synthesis of C-glycoside derivatives of sialic acids, which are the carbohydrate groups found at the terminal sites of cell-surface glycoproteins and glycolipids. Thus, the allylation of glycosyl chloride 16 with allyltributyltin under photo irradiation in the presence of hexabutylditin followed by hydrolysis gives an approximate 1 1 mixture of the a- and P-isomers. It is worth mentioning that while several synthetic approaches by... 

Fig. 40 Synthesis of a-C-glycosyl derivative of nojirimycin and its analogues. Reagents and conditions (a) BnNH2, PTSA (b) CH2=CHCH2MgBr, Et20 (c) FmocCl, Na2C03 (d) PCC (e) piperidine, DMF (f) NaHB(OAc)3, AcOH, Na2S04, 1,2-dichloroethane, -35 °C.

H. Kessler, V. Wittmann, M. Kock, and M. Kottenhahn, Synthesis of C-glycopeptides via radical addition of glycosyl bromides to dehydroalanine derivatives, Angew. Chem. Int. Ed. Engl. 3/ 902 (1992). 

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