Alkyl sugar

Generally, the reactions are carried out in refluxing benzene solution, since the yield in benzene is better than that in other solvents. Probably, the radicals formed may be somewhat stabilized by the weak orbital-orbital interaction between the radicals and benzene. However, from the environmental point of view, toluene or dioxane is recently used. As substrates, alkyl bromides or alkyl iodides are used, and the reactivity increases in the order prim-alkyl < seoalkyl < te/t-alkyl. Sugar anomeric bromide (3) is generally not so stable, so the reaction is carried out under irradiation conditions with a mercury lamp at room temperature (eqs. 4.2 and 4.3). There are two types of anomeric glycosyl radicals as shown in Figure 4.1. One is the axial radical [I], and the other is the equatorial radical [I ]. The axial radical is more nucleophilic than the equatorial radical due to the stereoelectronic effect, where this effect comes... 

An unusual nucleoside, kumusine (85), has been reported from the Indonesian marine sponge Theonella sp. [92]. Kumusine (85) represents the first natural occurring halogenated purine nucleoside containing an alkylated sugar, 2-methyl-5-deoxy ribose, that also represents a new... 

Synthesis of nucleosides. Reaction of shylated heterocycles with a protected 1-0-acyl or 1-0-alkyl sugar in 1,2-dichloroethane with either trimethylsilyl perchlorate or trimethylsilyl trifluoromethanesulfonate, (013)3810802-CF3, as catalyst gives nucleosides in high yield. The reaction is formulated for the reaction of silylated uracil (1) with l-0-acetyl-2,3,5-tri-0-benzoyl- 3-D-ribofuranose (2) either at 22 for a prolonged period or for 4 hr. at reflux temperature. The function of the catalyst is to convert the sugar into the glycosyl... 

An Italian group [110] obtained another useful anthracyclinone ring A precursor, the alkylated sugar cyanide 92, from 1,2 5,6-di-O-isopropylidene-a-D-glucofuranose (84). Cyanide 91 was prepared in six steps from the readily available furanose 84 [111]. Alkylation of the carbanion generated from... 

Amphotropic behavior can be found for a large number of different chemical structures. Additional information is given in other chapters of this Handbook. Typical classes of amphotropic materials are for instance classical soaps (see lyotropics), transition metal soaps (see metallomesogens), viologens, quartemary amines and other ionic surfactants (see lyotropics), block copolymers (see polymer liquid crystals), cellulose derivatives (see cellulose liquid crystals) and partially fluorinated paraffines, diols, peptide surfactants, lecithins, lipids, alkylated sugars and inositols, naturally occurring glycosides and silanols, which are discussed in this chapter. 

Alkyl sugars have at least one hydroxyl group etherated with an alkyl group. In acyl sugars, the hydroxyl groups are esterified. Sulfuric acid semiesters are also called sulfates (Table 31-4). 

Similar to ionic surfactants, nonionic surfactants such as alkyl ethoxylates, CmE , and alkyl sugars form micelles and microemulsions above their cmcs. CmE surfactants contain hydrocarbon chains of variable lengths... 

Figure 8 Structure of a dendrocleft and three alkylated sugar derivatives. ...

Sugars are a commonly used source for amphiphilic liquid crystals [10]. These materials show lamellar, columnar, and cubic phases, but chiral phases are very rarely observed. Thermotropic cholesteric phases are never observed and lyotropic cholesteric phases based on asymmetric micelles only in a few cases [11]. The bicontinuous cubic phase of these glycolipids may have macroscopic chiral ordering, but this has not been resolved hitherto [12], [13]. Thus, alkylated sugars are chiral compounds, but not effective... 

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