Chemistry Reference
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turned out to be the most ecient one in terms of selectivity. As an
alternative, enzymatic catalysis can also provide highly selective
esterification at O-1
0
(by proteases) or at O-6
0
(by lipases). For sequential
selective diesterification, combination of both the chemical and
enzymatic methods where also used. This permitted to study the solution
and the thermotropic behaviors or sucrose esters, within the context of a
more global investigation of the liquid crystalline behavior of glycolipids
(this field is covered in this topic in the chapter by Goodby and
colleagues). After sucrose esters,
63,64,69
and sucrose ethers,
70
a full family
of new methyl glucoside hydroxyalkyl ethers
71
and more complex gly-
costeroid compounds
72,73
were also investigated (Fig. 4), providing some
new insights on the effect of the position of the chain on the sugar
backbone in the way such amphiphilic compounds self-assemble.
Using carboxymethyl glycoside lactones (CMGLs) as a new type of
carbohydrate ligation reagent, several new sugar conjugates were pre-
pared, many of them in the idea of providing water solubility, polarity,
amphiphilicity to a non-polar counterpart.
74
We identified this type of
lactone 31 when studying the hydrogen peroxide oxidation of iso-
maltulose to carboxymethyl glucoside 30 and its further acetylation
(Scheme 12).
75,76
The lactone was found to easily react with various
nucleophilic species. The reaction proved to be particularly ecient in the
case of amines, which give amides upon lactone opening. The resulting
amides being very stable, further elaboration of the products was easily
achieved. The scope of application of the strategy was further extended by
designing alternative routes towards similar lactones from any sugars,
77,78
which allowed to prepare diverse types of pseudoglyconjugates, such as
sugar-amino acid hybrids, pseudodisaccharides, glycosylated prophyrins,
etc.
79,80
The same strategy was also use to prepare the first example of non
ionic carbohydrate based membrane imaging probes with two photon
fluorescence and second harmonic generation properties.
81,82
An inter-
esting aspect of the CMGL synthons is the straightforward second sub-
stitution possible at O-2 after the lactone opening offering an easy access
to 1,2-bisfunctionalised carbohydrate derivatives.
83-85
This was used for
preparing two new families of glycomonomers (Scheme 13), either azi-
doalkyne AB type monomers, or systems having one acrylamide moiety
and one azido group, which were then used in the synthesis of new
glycopolymers.
Fig. 4 Examples of compounds for which the thermotropic behavior has been studied.
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