Chemistry Reference
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either by direct reaction of a monosaccharide (
D
-glucose) with an alcohol
(Fig. 3) through reversed hydrolysis, which requires to select carefully the
optimal water content of the reaction medium, or by transglycosylation of
a disaccharide that acts as glucosyl donor. This latter pathway is not
preferred for the preparation of b-alkylglucosides because glucosyl
donors are more expensive than glucose.
43
Despite it is attractive in view
of the high selectivity and limited side-products generation, the use of
enzymes is not yet mature for production of APG at the industrial scale
because of low yields and high production costs mainly due to the
isolation, purification and stabilization of the enzymes.
44
In September 2013, the French specialty chemicals manufacturer
SEPPIC received the Pierre Potier award for chemistry innovations
promoting sustainable development for its 100%-biobased hydrotrope
heptylglucoside. This biodegradable hydrotrope is prepared from glucose
and heptanol that is obtained from castor oil, using a process that
complies with the 12 principles of green chemistry (Fig. 4).
45
Pentose-based hydrotropes can also be prepared from agricultural-
waste material, such as wheat straw or corn stover, through glycosylation
of the pentoses (
D
-xylose,
L
-arabinose) produced after extraction and hy-
drolysis of the hemicelluloses (Fig. 5).
46
Amylxylosides are produced from
xyloses and amyl alcohols, which are obtained from fusel oil, a by-
product of the ethanol production, and thus they are also 100% bio-based
hydrotropes. A direct conversion of xylans into alkylpentosides by
reaction with short- and long-chain alcohols under acidic conditions was
also described by Bouxin et al.
38
Alternatively, Ochs et al.
47
prepared
various alkyl b-
D
-oligoxylosides from xylans by transglycosylation using a
xylanase.
Finally, Ranoux et al. have prepared and evaluated C-glycosyl com-
pounds as hydrotropes.
48,49
They are advantageously more stable towards
acid and enzymatic hydrolysis than their O-glycoside counterparts, which
may decrease their biodegradability in return. The Horner-Wadsworth-
Emmons (HWE)
reaction was used to prepare various C-glycosyl
Fig. 4 Route to the Seppic heptylpolyglucoside, a 100% bio-based sustainable hydro-
trope that received the 2013 Pierre Potier price.
45
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