Aryl-C-glycosides synthesis

AFP. See Antifreeze proteins (AFPs) Aglycones and aglycone reactions. See Natural C-glycosides Ramberg-Backlund reaction Reverse polarity (umpolung) approach to aryl C-glycoside synthesis Sialyl Lewis X (sLex)... 

Friedel-Crafts alkylation has been used in an important synthesis of aryl C-glycosides, which are potent anti-tumor agents, from glycosyl fluorides (equation 99)65 661. The reaction takes place rapidly in dichloromethane, at room temperature using a novel zirconium complex and silver perchlorate combination catalyst. A similar alkylation has been performed by replacing the aromatic compound with either a silyl enol ether or an allylic compound using silver triflate as the catalyst662,663. 

The synthesis of a variety of stable carbohydrate mimetics using a RCM approach is discussed. An esterification-ring-closing metathesis (RCM) approach has been utilized for the preparation of a variety of alkyl and aryl C-glycosides. The synthesis of a number of C-saccharides will also be addressed. Yield optimization studies and the synthesis of the substrates will also be discussed. 

Glycal-substituted quinols and quinol ketals, derived from the 1,2-addition of lithiated glycals to quinones or quinone monoketals, are versatile intermediates for the synthesis of aryl C-glycosides, providing access to all four substitution patterns found in the natural products. For example, reduction of a quinol provides a p-hydroxyaryl glycal (8 9,11 -> 12). On... 

Seeking to demonstrate the merits of the reverse polarity approach to aryl C-glycosides in a total synthesis, we have tested it in the context of the antifungal papulacandin / chaetiacandin class (group 1 substitution pattern) and also in the context of the antibiotic Cl04 (group 2 substitution pattern). These applications are shown below (Scheme 8). 

For an outline of an alternative unified strategy for the synthesis of aryl C-glycosides, see Martin, S. F. Pure AddI. Chem. 2003. 75, 63. 

Scheme 45. C-glycoside synthesis by reaction of sugar lactones with lithium aryls [ 137]...

Suzuki K, Matsumoto T (1993) Total synthesis of Aryl C-glycoside antibiotics. In G Lukacs (ed) Recent progress in the chemical synthesis of antibiotics and related microbial products. Springer, Berlin, Heidelberg, New York, p 353... 

Wellington KW, Benner SA. A review synthesis of aryl C-glycosides via the Heck coupling reaction. Nucleosides Nucleotides Nucleic Acids 2006 25 1309-1333. 

Yamaguchi, M, Horiguchi, A, Ikegura, C, Minami, T, A synthesis of aryl C-glycosides via polyketides, J. Chem. Soc., Chem. Commun., 434-436, 1992. 

C-aryl glycosides, 528 C-glycosides, 528 C-glycoside synthesis, 505 fronj enol ethers, 505 by free-radical methods, 507 from ketene acetals, 505 from malonate anion, 505 from 2-pyridylthio glycosides, 385... 

Synthesis of aryl-C-glycoside has been reported by the same methodologies. One recent example is shown in O Scheme 12. 2-Deoxysugar reacts with napthtyl lithium to give the corresponding hemiacetal, which was reduced with NaBH3CN in an acidic aqueous medium to afford Qf-C-glycoside exclusively [24]. 

Stereoselective formation of the aryl-C-glycosidic linkage has been developed for synthesis of biologically important antibiotics and plant constituents. The most direct and widely used synthetic method is the Friedel-Crafts type reaction between electrophilic carbohydrate... 

---