Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Patent
1994-09-21
1996-03-12
Rollins, John W.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C07H 1700
Patent
active
054987040
DESCRIPTION:
BRIEF SUMMARY
The invention relates to the preparation of alkyl glycosides by alkylation of reducing saccharides by means of dialkyl sulfates in the presence of a base and a solvent.
Surface-active compounds based on renewable raw materials are becoming increasingly important. In this connection fatty alcohol sulfates and methyl esters of .alpha.-sulfofatty acids may be mentioned as examples of anionic surfactants, while carbohydrate fatty acid esters, fatty alkyl glucamides and, in particular, alkyl glycosides may be mentioned as examples of nonionic surfactants. Alkyl glycosides have been known for a long time as carbohydrate surfactants, but on account of their relatively complicated preparation have hitherto been used only to a limited extent in detergents and cleaning agents. Alkyl glycosides may be prepared from the corresponding halides and long-chain alcohols by the conventional Konigs-Knorr method via activation of the C-1 position. A whole range of further, generally complicated glycosylation variants are described in the literature, cf. P. Sinay, Pure & Appl. Chem., Vol. 63 (1991), 519 and R. R. Schmidt, Angew. Chem. Vol. 98 (1986), 213.
Alkyl glycosides are in principle prepared industrially by two different methods. In the transacetalation method, a hydrophilic monosaccharide unit is reacted in a first process stage with a short-chain alcohol (generally n-butanol or glycol) under acid catalysis to form a short-chain alkyl glycoside, which is then converted to the surface-active alkyl glycoside in a second stage by reaction with a long-chain alcohol (transacetalation). In another common method a monosaccharide unit is reacted directly with the long-chain, hydrophobic alcohol under acid catalysis. Many variants of the two preparation methods are described in the patent literature, e.g. in U.S. Pat. No. 3,547,828, U.S. Pat. NO. 3,598,865, U.S. Pat. No. 3,839,318, EP-A-0 362 671 and EP-A-0 252 241.
Since both aforedescribed glycosylation processes involve an equilibrium reaction, the alcohol component is in each case used in excess, and the excess alcohol has to be removed from the reaction product after the reaction. The distillative separation of long-chain alcohols from the reaction mixture is technically complicated and expensive. Moreover, on account of the thermal instability of the alkyl glycosides, the reaction product is seriously discolored. The alkyl glycosides obtainable in this way are mixtures of alkyl monoglycosides and alkyl oligoglycosides and polyglycosides.
It is known from U.S. Pat. No. 4,663,444 that glycosides which are alkylated or arylated in the C-6 position can be prepared by reacting 1-alkyl glycosides with methyl mesylates of the formula R'--O--SO.sub.2 CH.sub.3 (R'=aryl, aralkyl, alkyl or alkenyl of 1 to 20 carbon atoms) in the presence of bases such as KOH and of solvents such as dimethyl sulfoxide.
The peralkylation of carbohydrates by means of dimethyl sulfate has been known for a long time, cf. Houben-Weyl, Vol. 6/3, 35f (1965). Also, the selective methylation of glucose in the C-1 position by means of dimethyl sulfate is described in the literature, cf. D. M. Hall and O. A. Stamm, Carbohydr. Res., Vol. 12 (1970), 412.
It is an object of the present invention to provide an improved process for preparing alkyl glycosides that are suitable for use in detergents.
We have found that this object is achieved by a process for preparing alkyl glycosides by alkylation of reducing saccharides in the presence of a base and a solvent using, as alkylating agent, a dialkyl sulfate whose alkyl groups contain at least 6 carbon atoms, the molar ratio of saccharides to dialkyl sulfate being from 1:1 to 1:5. The reaction mixture obtainable in this way is used as a surfactant, preferably in detergents and cleaning agents.
The reaction of reducing saccharides with dialkyl sulfates proceeds according to the following reaction scheme: ##STR1## where GlyOH is a reducing saccharide and R is alkyl.
As long as the reducing saccharides and the dialkyl sulfate are used in a molar ratio of 1:1, practically e
REFERENCES:
patent: 3547828 (1970-12-01), Mansfield et al.
patent: 3598865 (1971-08-01), Lew
patent: 3839318 (1974-10-01), Mansfield
Angew. Chem. Int. Ed. Engl., vol. 25, pp. 212-235, 1986, Richard R. Schmidt, "New Methods for the Synthesis of Glycosides and Oligosaccharides-Are There Alternatives to the Koenigs-Knorr Method?".
Pure & Appl. Chem., vol. 63, No. 4, pp. 519-528, 1991, Pierre Sinay, "Recent Advances in Glycosylation Reactions".
Carbohydrate Research, vol. 12, pp. 421-428, 1970, David M. Hall, et al., "4,6-O-Alkylidene Derivatives of D-Glucose and its Methyl Pyranosides. An Improved Acetalation Procedure".
Houben-Weyl, vol. 6/3, pp. 33-36, 1965.
Klotz Wolfgang
Oetter Guenter
Oftring Alfred
Schmidt Richard R.
Wolf Gerhard
BASF - Aktiengesellschaft
Rollins John W.
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