Oligosaccharide macrocycles

SCHEME 6.11 Synthesis of Cj- and C2-symmetric oligosaccharide macrocycles starting from anomeric azide with 4-propargyl ether at the opposing terminus. 

SCHEME 9.6 A macrocyclic oligosaccharide cyclodextrin forming a torus-shaped structure of cyclodextrin with rigid lipophilic cavities. (Adapted from Polyakov, N.E., Free Rad. Biol. Med., 36, 872, 2004. With permission.)... 

Many chiral compounds can be used as selectors, for example, chiral metal complexes, native and modified cyclodextrins, crown ethers, macrocyclic antibiotics, noncyclic oligosaccharides, and polysaccharides all have been shown to be useful for efficient separation of different types of compounds. 

The most frequently used CSPs for biological applications in the reversed-phase mode are based on macrocyclic antibiotics, proteins, or oligosaccharides, but some of the applications utilize phases based on polysaccharides, low-molecular-weight selectors, crown ethers, or columns based on immunoaffinity techniques (Table 17.5). 

Omori T (1996) Substitution Reactions of Technetium Compounds. 176 253-274 Oscarson S (1997) Synthesis of Oligosaccharides of Bacterial Origin Containing Heptoses, Uronic Acids and Fructofuranoses as Synthetic Challengers. 186 171-202 Ostrowicky A, Koepp E, Vogtle F (1991) The Vesium Effect Synthesis of Medio- and Macrocyclic Compounds. 161 37-68 Otsuji Y,see Mizuno K (1994) 169 301-346 Pdlinkd I, see Tasi G (1995) 174 45-72... 

Cyclodextrins are doughnut-shaped, macrocyclic oligosaccharides constructed of glucose units linked by a a(l - 4) bond. Hexamer, heptamer, and octamer are the most common, often called the a-, / -, and y-cyclodextrins, respectively (Fig. 1). Although cyclodextrin has been known as one of the oligoglucoses produced by Bacillus macerans since 1891 (2), its spectacular behavior as the possible enzyme model was first observed by Cramer and his co-worker (J). 

CDs are macrocyclic oligosaccharides built of a-D-g/wcopyranoside units interconnected by a-(M) bonds. They are obtained by enzymatic degradation of dextrins (Figure 7.4.2). The most important in this group of compounds 278a with n = 6, 7 and 8 bear the... 

Cyclodextrins (sometimes called cycloamyloses) make up a family of cyclic oligosaccharides composed of 5 or more a-D-glucopyranoside units linked 1 —> 4, as in amylose (a fragment of starch), and have been used as activating macrocyclic excipients in nonaqueous biocatalysis. Griebenow et al. observed that lyophilization of methyl-[3-cyclodextrin with subtilisin Carlsberg in a 6 1 weight ratio resulted in a 164-fold rate enhancement in THF for the transesterification rate of sec-phenethyl alcohol with vinyl butyrate (Scheme 3.3) [98]. 

Takahashi et al.45 used a 4-hydroxybenzenesulfonate linker on Syn-Phase polystyrene Crowns to prepare glucose derivatives and macrocycles (Scheme 20). Displacement of the monosaccharide-supported Crowns 70 with nucleophiles such as azide, iodide, and acetate gave the respective 6-substituted glucose derivatives 71, 72, and 73 in excellent purities and yields. The authors suggest that this methodology could be utilized for the preparation of oligosaccharide libraries. 

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