Glycosylations sulfoxide method

The glycosyl sulfoxide method has proven very efficient and flexible in constructing a variety of glycosidic linkages on the solid support. Combinatorial carbohydrate libraries prepared by this strategy hold great potential for the identification... 

Scheme 8 Solid phase synthesis of a trisaccharide by the glycosyl sulfoxide method.

The a-(l- 4)-linked pentamer of the daunosamine derivative 2,3,6-trideoxy-3-JV-[(guanidino)acetamido]-L-/yx o-hexose 22 has been produced by a glycosyl sulfoxide method and shown to bind to the minor groove of DNA. ... 

The problem of the nucleophilicity of amides in glycosylation reactions is not limited to the sulfoxide method and has been shown to result in the formation of glycosyl imidates from intermolecular reaction with activated donors. It appears that this problem may be suppressed by the prior silylation of the amide [348,349]. Accordingly, it may be sufficient to operate the sulfoxide method with an excess of triflic anhydride when amides are present so as to convert all amides into O-triflyl imidates, which are then hydrolyzed on work-up. Despite these problems, several examples have been published of successful sulfoxide glycosylation reactions with acceptors carrying remote peptide bonds [344,345] and with donors coupled to resins via amide-based linkages [346,347], with no apparent problems reported. Sulfonamides and tertiary amides appear to be well tolerated by the sulfoxide method [340,350],... 

The sulfoxide method was employed in the direct synthesis of a P-l,2-man-nooctaose (Scheme 4.60) [362-364]. The synthesis of a p-mannosyl phosphoiso-prenoid illustrates the possibility of employing even such weak nucleophiles as phosphates (Scheme 4.61) [365]. Both syntheses rely on the presence of 4,6-0-benzylidene acetal, and its effect on the covalent triflate-contact ion-pair equilibrium [366,367], to influence the stereochemistry of the glycosylation process [295,323],... 

A soluble aminomethylated polyethylene glycol and a succinoyl linker were used to support a 9-fluorenylmethyl group for solution-phase glycosylation by the sulfoxide method. With the help of temporary protection by a 6-O-triphenylmethyl ether, the method could be carried out iteratively to form disaccharides (Scheme 4.69) [379],... 

The sulfoxide method was introduced by Kahne and coworkers,1 and was heralded as a new method for rapid glycosylation of unreactive substrates in high yield under mild conditions. The reaction involves the sulfoxide donor [sulfoxide (I)], an activating agent (usually triflic anhydride), a hindered, nonnucleophilic base (2,6-di-tert-butyl-4-mcthylpyridine, DTBMP) and a nucleophilic acceptor (most often an alcohol) (Scheme 3.1). The glycosylation of sterically hindered steroidal alcohols, phenols and the /V-glycosylation of an acetamide was reported (Table 3.1). 

The practicahty of direct glycosylation methodology was demonstrated in the context of the synthesis of -mannan [55,56] and )6-rhamnoside (6-deoxy-)6-mannoside) [57,58,59]. In the latter case, a construction of the )6-mannoside by the sulfoxide method was followed by... 

It has been observed that the incorporation of lipophilic chains into vancomycin can increase the potency of the dmg [159,160,161,162]. This is best exemplified by the observation that teicoplanin retains activity against some vancomycin-resistant bacterial strains. In one early study directed at improving the efficacy of these antibiotics, Ge et al. investigated the mechanism of action of a chloro-biphenyl derivative of vancomycin that showed activity against resistant bacteria [163]. The sulfoxide method of glycosylation was utilized to achieve the desired modification of the gluco-vancomycin precursor (O Scheme 28). 

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. 

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