Disaccharides furanoid

Heterogeneous catalysts, particularly zeolites, have been found suitable for performing transformations of biomass carbohydrates for the production of fine and specialty chemicals.123 From these catalytic routes, the hydrolysis of abundant biomass saccharides, such as cellulose or sucrose, is of particular interest. The latter disaccharide constitutes one of the main renewable raw materials employed for the production of biobased products, notably food additives and pharmaceuticals.124 Hydrolysis of sucrose leads to a 1 1 mixture of glucose and fructose, termed invert sugar and, depending on the reaction conditions, the subsequent formation of 5-hydroxymethylfurfural (HMF) as a by-product resulting from dehydration of fructose. HMF is a versatile intermediate used in industry, and can be derivatized to yield a number of polymerizable furanoid monomers. In particular, HMF has been used in the manufacture of special phenolic resins.125... 

The reaction of sulfuryl chloride with furanoid derivatives has been studied [51,52], and the reaction has been applied to disaccharides, for example, methyl p-maltoside [53] and sucrose [54,55], to yield chlorodeoxy derivatives. 

The use of partially protected aldono-1,4-lactones as glycosyl acceptors led to glycosylaldono-1,4-lactones, which are useful precursors of disaccharides containing furanoid reducing units.97... 

In common with other reducing disaccharides, lactose undergoes the usual reactions of aldoses, although precautions must be taken to prevent hydrolysis of the glycosidic bond. Furanoid structures cannot be formed, however, because of the presence of the (1 —> 4)-linkage. 

A novel type of C=C linked disaccharide derivative (34) has been produced in good yield by condensation of a phosphorus ylide derived from 6-deoxy-6-iodo-1,2 3,4-di-0-isopropylidene-o -D-galactopyranose with the aldehyde corresponding to the furanoid moiety. Likewise, an alkene was obtained using this... 

The fact that stabilized bicylic cation corresponding to the anchimeric assistance can be less reactive than the opened oxocarbenium ion is supported by another example (Scheme 5.38) [88]. Reactions of acceptors 145 and 147 with furanoid sulfonium salt 144 gave only a moderate preponderance of the a-anomers of disaccharides 146 and 148, although the structure of 144 is preorganized for the selective a-attack. 

A conformational analysis of furanoid - pyranoid non-reducing disaccharides, based on crystallographic data, has been published, and the conformation of trehalose incorporated in a micelle has been studied by H-n.m.r, spectroscopy. Conformational analysis by use of various and C-n.m.r. techniques in combination with theoretical calculations has been achieved for the two galactobiosides (18) and (19), for the eight-membered 3,2 -O-isopropylidene acetals (20) and (21) of methyl / -cellobioside and benzyl -D-lactoside, respectively. 

Syntheses of amino-sugar glycosides and disaccharides, including chromogenic substrates for A -acetyl-p-D-glucosaminidase, are covered in Chapter 3. Synthesis of protected 2-amino-2-deoxy-glycosyl azides is covered in Chapter 10. 2,3,6-Trideoxy-5-0-(4-nitrobenzoyl)-3-trifluoroacetamido-L-riho-hexofuranosyl bromide, a furanoid ristosamine derivative, was synthesized from L-rhamnal via intermediates reported previously (Vol.25, p.253) to effect glycosylations. ... 

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