Maltose and derivs

Maltose and cellobiose (Section 25.14) are examples of disaccharides derived from D-glucopyranosyl units. 

The two primary hydroxyl groups in maltose and its derivatives show a large difference in reactivity. On selective tritylation, /3-maltose,238 benzyl /3-maltoside,239 and methyl 3-0-(methylsulfonyl)-/3-maltoside127 all gave mainly 6 -0-trityl compounds. Tritylation of cyclohexaamylose130 and amylose132,240 yielded the expected 6-0-trityl derivatives. 

Figure 4.19 The structures of the disaccharides maltose and cellobiose, derived from the hydrolysis of starch and cellulose, respectively.

Maltose is another important disaccharide. It can be produced on a large scale from starch, but its potential as a raw material for chemical industry needs to be explored. In order to achieve this objective, an understanding of the fundamental chemistry of maltose is essential. The purpose of this article is, therefore, to collate information on the reactions of maltose, and to illustrate some of the physical methods that have contributed to the characterization of maltose derivatives. 

The importance of sugar sulfonates as synthetic intermediates has been widely recognized.77,78 Selective methanesulfonylation and p-toluenesulfonylation of maltose and its derivatives has been studied. Umezawa and coworkers used sequential p-toluenesulfonylation and acetylation to obtain crystalline l,2,3,2, 3, 4 -hexa-0-acetyl-6,6 -di-0-p-tolylsulfonyl-/3-maltose in 45% yield.79 Dimolar methanesulfonylation of methyl /3-maltoside followed by acetylation afforded crystalline methyl 2,3,2, 3, 4 -penta-0-acetyl-6,6 -di-0-(methylsulfonyl)-/3-maltoside. The mother liquor also yielded a small proportion of a... 

A large number of sulfonate derivatives of maltose and its derivatives has been synthesized from l,6-anhydro-/3-maltose,32,46-47-67 1,6-anhydro-4, 6 -0-benzylidene-/3-maltose,82 methyl 4, 6 -0-benzylidene-/3-malt-... 

High-resolution, H-n.m.r. spectra of trityl ethers of maltose and its derivatives have been described.45,68 166 In the H-n.m.r. spectrum of methyl 2,2, 3, 4 -tetra-0-acetyl-3-0-(methylsulfonyl)-6,6 -di-0-trityl-/3-maltoside (68), the chemical shifts of methine protons (H-2, H-2, H-... 

Importantly, this halogenation process can be extended to members of the disaccharide series, and the lactose, maltose, and cellobiose derivatives 61, 62, and 63 afford the crystalline a-glycosyl bromides 64,65, and 66 in almost quantitative yields (see Scheme 10).51 As these O-benzoylated oximes are... 

---