Oxidative glycosylations

A conceptually new direct oxidative glycosylation with glycal donors, employing a reagent combination of triflic anhydride and diphenyl sulfoxide, has recently been reported by Gin [83], This new 3-glycosylation method works very well with hindered hydroxy nucleophiles, including sterically shielded carbohydrate hydroxy systems, and can be run on large scales. 

D-Ribonolactone is a convenient source of chiral cyclopentenones, acyclic structures, and oxacyclic systems, useful intermediates for the synthesis of biologically important molecules. Cyclopentenones derived from ribono-lactone have been employed for the synthesis of prostanoids and carbocyclic nucleosides. The cyclopentenone 280 was synthesized (265) from 2,3-0-cyclohexylidene-D-ribono-1,4-lactone (16b) by a threestep synthesis that involves successive periodate oxidation, glycosylation of the lactol with 2-propanol to give 279, and treatment of 279 with lithium dimethyl methyl-phosphonate. The enantiomer of 280 was prepared from D-mannose by converting it to the corresponding lactone, which was selectively protected at HO-2, HO-3 by acetalization. Likewise, the isopropylidene derivative 282 was obtained (266) via the intermediate unsaturated lactone 281, prepared from 16a. Reduction of 281 with di-tert-butoxy lithium aluminum hydride, followed by mesylation, gave 282. 

K. Mitsudo, T. Kawaguchi, S. Miyahara, W. Matsuda, M. Kuroboshi, and H. Tanaka, Electro-oxidative glycosylation through C-S bond cleavage of l-arylthio-2,3-dideoxyglycosides. Synthesis of 2, 3 -dideoxynucleosides, Org. Lett., 7 (2005) 4649-4652. 

The Wolff pathway of oxidative glycosylation,400 initiated by the autoxidation of glucose to form reactive intermediates, such as arabinose and glyoxal.401... 

Chen, M.-Y., Patkar, L. N., Chen, H.-T., Lin, C.-C. An efficient and selective method for preparing glycosyl sulfoxides by oxidizing glycosyl sulfides with OXONE ort-BuOOH on SI02. Carbohydr. Res. 2003, 338, 1327-1332. 

The following section describes the versatility of the usual glycosidases in providing thio(S)-glycosides [6,7]. Thiol (SH) compounds have general problems such as characteristic smell, high volatility, low solubility, and liability to oxidation. Glycosylation is... 

Valeria DB, Kim Y, Gin DY. Direct oxidative glycosylations with glycal donors. J Am Chem Soc 1998 120 13515-13516. 

Yamamoto and coworkers proposed that iridodial (15) then undergoes oxidation, glycosylation, and methylation to provide 7-deoxyloganin (24). Finally, hydroxylation by 7-deoxyloganin 7-hydroxylase, a cytochrome P450 monooxygenase, affords loganin (16). ... 

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