Bio-renewable surfactants based on fructose and fatty acid esters.

Abstract

The invention relates to the fields of surfactants and green chemistry, more in particular to means and methods for the synthesis of novel surfactants based on readily available and biorenewable building blocks. Provided is a method for the synthesis of a carbohydrate surfactant molecule, comprising the steps of: (i) reacting a fructose-containing saccharide with 3-hydroxy propionitrile under acid conditions to obtain the cyano-intermediate compound cyanoethyl β-fructopyranoside; (ii) hydrogenating the cyano-intermediate compound in the presence of a catalyst to obtain an amine-intermediate compound; and (iii) amidating said amine moiety by contacting the amine-intermediate compound with at least one alkyl ester or glycerol ester of a saturated or unsaturated, optionally substituted, aliphatic C4-C22 carboxylic acid in the presence of a base to obtain a fructose-based surfactant molecule.

Description

[0001]P135204PC00 Title: Bio-renewable surfactants based on fructose and fatty acid esters. The invention relates to the fields of surfactants and green chemistry. More in particular, it relates to means and methods for the synthesis of novel surfactants based on readily available and biorenewable building blocks, and to compositions comprising the same. Surfactants are amphiphilic compounds composed of a hydrophilic head and hydrophobic tail. Due to their surface tension-active properties, surfactants are essential compounds in the chemical industry and daily commodities. There are four major types of surfactants: non-ionic, anionic, cationic, and zwitterionic surfactants. The application of surfactants is widespread: for personal use like cleaning and cosmetics, household use (dishwashers, laundry), industrial cleaning, (anti)-foaming in chemical and biotechnological processes, and emulsifiers in the oil industry. The synthesis of surfactants conventionally includes sulfonation, sulfation, ethoxylation, alkylation, and esterification. Many of the commonly employed reactions in the synthesis of surfactants are not sustainable. The synthesis of surfactants is mainly based on petrochemicals and harsh acidic conditions contribute to environmental pollutants and hazards. Using alkyl or alkylphenyl substituents as the hydrophobic tail usually requires a petrochemical source, reducing the sustainability of the synthesis. The production of linear alkylphenyl substituents also results in environmental pollutants. Furthermore, some types of surfactants have a negative impact on living organisms. For example, linear alkyl sulfonates can change the physiological and biochemical activities of aquatic organisms by delaying their metabolism and growth, damaging cell membranes, resulting in the breakdown of the chlorophyll protein complex. Quaternary ammonium substituents such as cetrimonium chloride are toxic compounds for the environment. Alkylphenol ethoxylates, utilized as a detergent, emulsifier, and wetting agent, degrade into toxic compounds that are persistent in the environment. Most currently available commercial surfactants are produced from petrochemicals. The current petrochemical-based surfactants are low- cost mature products, reasonably effective, but industry is under constant pressure to replace these currently used surfactants with "bio-based" surfactants. The latter have the advantage of being renewable, and biodegradable. Biobased surfactants have been developed to improve the sustainability of the production of surfactants. There are two types of biobased surfactants. The first generation of biobased surfactants is synthesized chemically from renewable sources (Biobased Surfactants, Synthesis, Properties and Applications, 2ndedition, D. G. Hayes et al. Academic Press 2019, ISBN 978-0-12-812705-6 ). Examples include sugar esters, alkyl glycosides, and alkanolamines (S. Warwel et al. Eur. J. Lipid Sci. Technol.2001, 103, 645-654). The second generation of biobased surfactants originates from biotechnology (B. Fridrich, PhD thesis University of Groningen, 2022, https: / / doi.org / 10.33612 / diss.195831380). The main examples of second generation bio-based surfactants are glycolipids (C. Wang et al. Microb. Cell Fact.2019, 18, 90) and lipopeptides (B. H. Rehm et al. Appl. Environm. Microbiol.2001, 67, 3102) Esterification is an attractive method to yield sustainable surfactants due to its simplicity. Esters result from direct condensation of glucose or glycosides with a fatty acid, or transesterification with FAME. Sucrose esters, for example, can be obtained by a transesterification with triglycerides in DMF at 120-130 ºC. Drawbacks of this method are the use of toxic solvents and the high temperature that leads to partial decomposition of the sugars (D. K. Allen et al. J. Surfactants Deterg.1999, 2, 383-390) Carbohydrates are undeniably versatile building blocks for the development of new surfactants. Glucose so far is predominantly used. Apart from glucose, also sucrose, (E. Fanton et al., Carbohydr. Res, 1997, 298, 85-92) lactose (V. Langlois et al. J. Chem. Soc. Perkin Trans.1, 1994, 2103-2106), xylose (S. Bouquillon, Comptes Rendus Chim.2011, 14, 716- 725), and furfural, a dehydrated sugar, (L. Kipshagen et al. Green Chemistry, 2019, 21, 3882-3890) are utilized for the synthesis of renewable surfactants. However, from an industrial perspective, only a few carbohydrates meet the criteria of price, quality, and availability to be an interesting raw material source. The major sources are sucrose from sugar cane or sugar beet, glucose derived from starch, and sorbitol (hydrogenated glucose). (K. Hill, in: Surfactants from Renewable Resources, Wiley-VCH 2010, 64-84). Esterification involving Fischer glycosidation is usually used to convert those sugars into the corresponding esters. Unfortunately, these reactions predominantly result in a complex mixture of mono-, di-, tri-, tetra-, and pentaesters which necessitates laborious (e.g. column chromatography) steps to obtain a single desired product. The present inventors, recognizing the need for further alternatives to petrochemical-based surfactants, aimed at providing a novel approach for the preparation of surfactants based on readily available bio- renewables. In particular, they sought to develop a synthetic process that can be performed at moderate temperatures and does not rely on using toxic or dangerous materials. Ideally, the synthetic process is readily scalable and does not involve tedious steps such as protection-deprotection reactions, extractions, and / or column chromatography. Furthermore, the resulting surfactants and their degradation products should not be toxic or hazardous to the environment. It was surprisingly found that at least some, if not all, of the above goals can be met by reacting fructose or a polymer thereof such as inulin, a polymer of fructose, with acidified hydroxy propionitrile. This leads to the formation and precipitation of cyanopropyl fructopyranoside as a unique intermediate compound. Unexpectedly, it was observed that from all possible isomers, only one form precipitates. Because of this selective precipitation, the intermediate cyano-compound is easily isolated e.g. by filtration, followed by hydrogenation at ambient pressure and temperature to produce aminopropyl fructopyranoside in near quantitative yield. Amidation of the amino moiety of this amine-intermediate by an esterified long chain carboxylic acid then yields a pure, single-component amphipathic molecule having surface active properties. Accordingly, the invention relates to a method for the synthesis of a carbohydrate surfactant molecule, comprising the steps of: (i) reacting a fructose-containing saccharide with 3-hydroxy propionitrile under acid conditions to obtain the cyano-intermediate compound cyanoethyl β-fructopyranoside; (ii) hydrogenating the cyano-intermediate compound in the presence of a catalyst to obtain an amine-intermediate compound; and (iii) amidating said amine moiety by contacting the amine-intermediate compound with at least one alkyl ester or glycerol ester of an aliphatic C4- C22 carboxylic acid in the presence of a base to obtain a fructose-based surfactant molecule. Also provided are beta-fructopyranosides (for use as intermediate compounds) of the formula and fructose-based surfactant molecules of the general formula I wherein R1is CH2-OH, C(=O)OH or C(=O)O-M+, and M is a metal cation, preferably an alkali metal cation, or an ammonium cation; R2is H, C1-C8alkyl or benzyl; and A is an aliphatic C3-C21 moiety. Fructose-based surfactants and the intermediate compounds according to the invention and methods for providing them have not been disclosed or suggested in the art. Direct exploitation of fructose for glycosidation is not trivial since it usually results in a complicated mixture of α / β-furanosides and pyranosides (F. Lichtenthaler et al. Liebigs Annalen 1995, 2069-2080) US 6,369,014 discloses glycoside-based surfactants including fructosyl- based carbohydrate linked to an alkyl moiety via several linkers, including an amido moiety (cf. claim 1, definition of X being inter alia C(O)-N(Z)-). GB 1072655 discloses several surfactants based upon alkyl-glucosyl derivatives encompassing ethoxy spacers, including derivatives wherein the glucosyl derivative is linked to an amidoalkyl moiety via an ethylene linker. It also describes the preparation of an amido derivative by reacting a glucosyl moiety with hydroxyethyl lauramide (cf. example VIII). However, GB 1072655 is silent about the use of fructose-based carbohydrate or the use of 3-hydroxypropionitrile as reactant. Neither US 6,369,014 nor GB 1072655 discloses or even suggests the propylene moiety as a suitable spacer linking the carbohydrate moiety - let alone a fructose-based moiety - to the alkylamido moiety. In connection with studies on new non-ionic carbohydrate-based surfactants and mesogens, Raaijmakers et al. reported on acid-catalysed reactions of D- fructose, sucrose and inulin with ω-halogenoalkyl alcohols to yield the corresponding β-D-fructopyranosides. The glycosidation of fructose and the fructose sources was quite efficient with 2-chloroethanol, 2-bromoethanol or 3-chloropropanol. However, the yield dropped considerably when 4- chlorobutanol was used (H. W. C. Raaijmakers et al. Carbohydr. Res.1994, 257, 293 and references cited therein) Hence, according to this trend, the prior art suggests that halogenated alcohols with longer alkyl chains are not applicable to form crystalline β-fructopyranosides. The applicability of various other alcohols, including 2-butoxyethanol, 3-hydroxypropionitrile and 1-octanol, was studied as well but failed to yield the crystalline β- fructopyranosides (Raaijmakers et al. Rec. Trav. Chim. Pays Bas.1993, 112, 511-514.) Hence, the advantageous use of 3-hydroxypropionitrile to selectively obtain cyanoethyl-β-fructopyranoside according to the present invention was unpredictable and against all expectations. Fructose glycosidation Step (i) of a method as provided herein comprises reacting a fructose- containing saccharide with 3-hydroxy propionitrile under acid conditions to obtain cyanoethyl β-fructopyranoside as cyano- intermediate compound. Suitable fructose-containing saccharides include fructose, sucrose, inulin and high-fructose corn syrup (HFCS). Mixtures of two or more fructose- containing saccharides can be used as well. In a preferred embodiment, step (i) comprises reacting D-fructose, oligofructose, inulin, HFCS, or a mixture thereof with 3-hydroxy propionitrile. Sucrose is a disaccharide composed of one glucose and one fructofuranose moiety. Inulin is a heterogeneous collection of fructose polymers. It consists of chain-terminating glucosyl moieties and a repetitive fructosyl moiety, which are linked by β(2,1) bonds. The degree of polymerization (DP) of standard inulin ranges from 2 to 60. The fractions with DP ≤10 are referred to in the art as short-chained fructo-oligosaccharides or ‘’oligofructose’’. Scheme 1. Synthesis of cyanoethyl-fructopyranoside 1 from D-fructose or inulin The acidification of 3-hydroxy propionitrile is readily achieved by the addition of acetyl chloride to form HCl. However, other acids such as phosphoric acid, and sulfuric acid can also be used. In one embodiment, about 0.5 to 2 vol%, e.g.1 vol%, of acetyl chloride is added to 3-hydroxy propionitrile followed by stirring for about 15-20 minutes at room temperature, after which fructose-containing sugar is added and stirring is continued to allow for the glycosidation reaction to proceed. Suitably, the glycosidation reaction is performed for at least 3 h at room temperature, preferably for 4 h, to ensure fructose is entirely dissolved. A higher yield may be obtained when the reaction is performed at a higher fructose-alcohol ratio. Preferably, the initial D-fructose concentration is at least 0.4 g / mL. For example, glycosidation of fructose at 0.5 to about 1 g / mL at 5 g scale led to 68% and 61% yields, respectively. The routine synthesis of compound 1 from D-fructose gave a 55-65% yield, i.e. a band width of 10%. The mixture turned thicker at higher fructose-alcohol ratios, and magnetic stirring may become difficult. Therefore, at a ratio of 1 g / mL or more, the reaction is suitably performed with overhead stirring. Whereas inulin has approx.90% fructose content, sucrose is composed of 50% glucose and 50% fructose. With the same loading of D-fructose and sucrose in the reaction, the fructose concentration is only half in the case of sucrose, resulting in a low fructose-alcohol ratio and therefore a lower yield. It was observed that 5 g inulin entirely dissolved in 20 mL acidified 3- hydroxypropionitrile, but only afforded 9% yield of intermediate compound 1 in 4 d. By adding more inulin to a given volume of alcohol, a larger amount of product is formed, which induces precipitation. The product yield increased from 9% to 46% when the inulin-alcohol ratio increased from 0.25 to 0.5 g / mL. No further improvement was observed when the ratio further increased to 1 g / mL. Accordingly, in one embodiment step (i) comprises reacting at least 0.4 gram, of a fructose-containing saccharide per mL acidified 3-hydroxy propionitrile, preferably at least 0.5 g / mL inulin, or at least 1.0 g D-fructose per mL 3-hydroxy propionitrile. Hydrogenation reaction Step (ii) of a method as herein disclosed comprises converting the nitrile moiety of the cyano-intermediate compound 1 in the presence of a hydrogenation catalyst to obtain an amine-intermediate compound 2 comprising a (primary or secondary) amine moiety. This amine moiety is then used in step (iii) to prepare an amide-based surfactant. Suitable hydrogenation catalysts are known in the art. Typically, iridium, nickel, palladium, platinum, rhodium, or ruthenium are used to activate the chemical reaction between hydrogen and another compound. Common catalysts used for hydrogenation are insoluble metals such as palladium in the form Pd-C, platinum in the form PtO2, and nickel in the form Ra-Ni (Raney nickel). Hydrogenation using a heterogeneous catalyst is preferred because this allows removal of the catalyst by filtration. For example, the catalyst is PtO2(Adam’s catalyst), or Raney nickel. In one embodiment, step (ii) utilizes PtO2 to perform hydrogenation at the conditions of e.g.20 mol% catalyst, 50 bar H2, in MeOH at 50 ºC. In a preferred embodiment, Raney nickel is used. For example, step (ii) comprises a hydrogenation reaction with an aqueous suspension of commercially available Raney nickel. It was found that at 15 wt% catalyst loading (including the water) of the Raney nickel suspension and 50 ºC, Raney nickel was sufficiently active to fully hydrogenate cyanoethyl- fructopyranoside at 1 atm of H2. See Scheme 2. As hydrogenations at atmospheric pressure are highly convenient, Raney nickel-catalyzed hydrogenation is preferred. Accordingly, hydrogenation step (ii) is advantageously performed at atmospheric pressure, preferably in the presence of catalytic Raney nickel. Scheme 2. Hydrogenation of cyano-compound 1 to primary amine-compound 2. a) PtO2 (10 mol%) for 18 h, or b) Raney nickel suspension (15 wt%), for 18 h. The hydrogenation of nitriles to primary amines often suffers from a side reaction in which the intermediate imine (formed after the first hydrogenation step) reacts with an equivalent of the already formed primary amine. This trans-imination reaction is followed by hydrogenation and leads to formation of the undesired secondary amine and ammonia. In this way, even a tertiary amine can be formed. Therefore, the hydrogenation reaction is advantageously carried out in the presence of at least 1 equivalent of an amine compound of the formula NH2R2, wherein R2is H or C1-C8alkyl or benzyl. In one embodiment, a method of the invention comprises the synthesis of a primary amine compound wherein hydrogenation is performed in the presence of ammonia (NH3). In another embodiment, a method of the invention comprises the synthesis of a secondary amine compound wherein hydrogenation is performed in the presence of a primary amine additive of the formula NH2R2, wherein R2is C1-C8 alkyl or benzyl. Preferably, R2is C1-C4 alkyl. For example, the primary amine additive is ethylamine. Amidation reaction Step (iii) comprises amidating the amine moiety obtained in step (ii) by contacting the amine-intermediate compound with one or more ester(s) of an aliphatic C4-C22carboxylic acid (herein also referred to as ‘’A-ester’’), to obtain a fructose-based surfactant molecule. Hence, the non-polar hydrophobic tail of a fructose-based amphipathic surfactant is provided by the medium to long chain hydrocarbon moiety of an esterified aliphatic carboxylic acid. Suitably, the aliphatic C4-C22 carboxylic acid is esterified to an alkyl or glycerol. The aliphatic carboxylic acid may comprise a linear or branched aliphatic chain, which may be saturated or unsaturated. The aliphatic chain may be unsubstituted or substituted. The carboxylic acid used will generally be a C6to C22, typically a C6to C18carboxylic acid. The carboxylic acid may be linear or branched, saturated or unsaturated, and suitable examples include lauric, myristic, palmitic, palmitoleic, stearic, iso-stearic (a mixture of mainly branched adds with a range of chain lengths averaging about C18), oleic, linoleic, linolenic, behenic, erucic or omega 3-, 6- or 9- fatty, acids. Mixtures of carboxylic adds may be used if desired. In one embodiment, the amine-intermediate compound is contacted with an aliphatic C4-C22carboxylic acid esterified to an alkyl. The alkyl ester may be a C1-C4 alkyl ester, preferably a methyl or ethyl ester. Preferably, it is a methyl ester of a C6-C22carboxylic acid, more preferably a C1-C4ester of a C6-C18carboxylic acid, most preferably a C1-C4ester of a C8-C12carboxylic acid. In one aspect, amidation is performed using a single type of alkyl ester of an aliphatic C4-C22carboxylic acid. In another embodiment, a mixture of two or more different alkyl esters of an aliphatic C4-C22 carboxylic acid is used. The difference may reside in the chain length of the alkyl ester and / or of the aliphatic carboxylic acid. Accordingly, in one embodiment a method of the invention comprises (i) reacting a fructose-containing saccharide with 3-hydroxy propionitrile under acid conditions to obtain cyanoethyl β-fructopyranoside as intermediate compound; (ii) hydrogenating the intermediate compound in the presence of a catalyst to convert the nitrile moiety to an amine moiety; and (iii) amidating said amine moiety by contacting the hydrogenated intermediate compound with an alkyl ester of an aliphatic C4-C22carboxylic acid to obtain a fructose-based surfactant molecule. In a specific aspect, a fatty acid methyl ester (FAME) or a mixture of FAMEs is used. The choice of the FAME is virtually non-restricted which allows a plethora of surfactants to be produced. The FAME may be obtained on industrial scale or by methanolysis of plant-based oils. In another embodiment, the hydrophobic moiety of the amphipathic surfactant is provided by a glycerol ester. Glycerol esters belong to the glycerolipids. One to three fatty acids (aliphatic carboxylic acids) are ester- linked to it. The number of fatty acids is reflected in the name of glycerol ester lipid classes: triglycerides contain three fatty acids, diglycerides two fatty acids, and monoglycerides one fatty acid. Hence, also provided is a method wherein an amine-intermediate compound is contacted with a glycerol ester comprising one or more aliphatic C4-C22 carboxylic acid(s). In one embodiment, a mono-glyceride is used to provide the aliphatic C4-C22 carboxylic acid for the amidation reaction. In another embodiment, a di- or triglyceride is used to provide the aliphatic C4-C22 carboxylic acids for the amidation reaction. The carboxylic acids esterified to the glycerol backbone of diacylglycerol (DAG) or triacylglycerol (TAG) for use in the present invention may be the same or different. Preferred glycerol esters are those obtained from renewable sources or plant origin, such as linseed oil, jojoba oil, jatropha oil, crude tall oil (CTO), rapeseed oil, and soybean oil. Accordingly, the invention provides a method wherein amidation step (iii) comprises reacting the amine-intermediate compound with at least one glycerol ester of a C4-C22carboxylic acid, preferably with glycerol esterified to one, two or three C4-C22carboxylic acid(s), more preferably mono-, di- or triacylglycerol comprising C6-C22 carboxylic acid(s), most preferably C8-C18 carboxylic acid(s). Amidation is performed in the presence of a strong base. Suitable amidation reactions can be determined using routine optimization. Exemplary strong bases include sodium and potassium alkoxides, such as NaOMe, NaOEt or KOtBu. Good results were obtained when amidation step (iii) is performed in the presence of sodium methoxide (NaOMe), preferably in an alcoholic solvent, such as methanol or 1,2-propanediol. In one embodiment, step (iii) comprises contacting the amine-intermediate compound with at least one (alkyl / glycerol) ester of an aliphatic C4-C22 carboxylic acid, in the presence of about 1 eq NaOMe per eq ester of carboxylic acid. See scheme 3. Scheme 3. Synthesis of a fructose-based surfactant by amidation with alkyl ester. In order to reduce or avoid hydrolysis of the alkyl ester of an aliphatic C4-C22carboxylic acid during the reaction, the use of anhydrous reagents and the careful removal of water from amino-fructoside 2 is preferred. To that end, the amino-fructoside 2 starting material is preferably exposed to reduced pressure and elevated temperature, such as < 5 mbar and 50 ºC. The NaOMe is preferably freshly prepared from sodium and anhydrous methanol under nitrogen. By performing the amidation at these optimized conditions, a series of fructose-based surfactants was obtained up to 77% yield. An example of the three steps is provided in scheme 4. Step (i) Step (ii) Step (iii) Scheme 4. Synthetic route to prepare fructose-based surfactants It was surprisingly found that steps (ii) and (iii) of the method of the invention can be readily performed in a step-wise process wherein a solid hydrogenation catalyst is removed by simple filtration, thus obviating the need to isolate the amine-intermediate compound prior to its amidation. See Example 6. Precipitation of the resulting surfactant is readily induced by adding an anti-solvent such as acetone to the reaction mixture. The product can be conveniently collected by filtration and the collected solid may be washed e.g. with acetone. Oxidation The steps described herein above give rise to unique non-ionic surfactant molecules. In general, the solubility of non-ionic surfactants is lower than that of ionic surfactants, which can be a downside in certain applications. It was found that a method of the invention is suitably adapted to provide an anionic surfactant by oxidizing the primary hydroxyl of the fructose- moiety to a carboxylic acid and converting the carboxylic acid to a carboxylic acid salt. See Example 3 herein below. Accordingly, in one embodiment a method of the invention comprises an additional step of oxidizing the primary hydroxyl of the fructose-moiety to a carboxylic acid and converting the carboxylic acid to a carboxylic acid salt. Oxidation can be carried out using a catalyst conventional used in organic oxidation reactions. In one embodiment, TEMPO (2,2,6,6- Tetramethylpiperidinyloxy or 2,2,6,6-Tetramethylpiperidine 1-oxyl) or a derivative or functional equivalent thereof is used. The thus obtained carboxylic acid is readily converted to a carboxylic acid salt using methods known in the art. Because of their enhanced acidity, carboxylic acids react with bases to form ionic salts. In the case of alkali metal hydroxides and simple amines (or ammonia) the resulting salts have pronounced ionic character and are usually soluble in water. Suitable salts include alkali metal salts e.g. Li, Na and K, and ammonium salt. The optional oxidation reaction is suitably carried out on the cyano- intermediate compound (i.e. following step (i)), which oxidized cyano- intermediate compound is subsequently subjected to the hydrogenation and amidation reactions as described herein above. Alternatively, conversion of the primary hydroxyl of the fructose-moiety to a carboxylic acid salt is performed following hydrogenation step (ii), i.e. on the amine-intermediate compound, or following amidation step (iii) i.e. converting a non-ionic surfactant molecule to an anionic surfactant molecule. Fructose-based compounds and uses thereof. The invention also relates to fructose-based compounds obtainable by one or more steps of a method provided herein and to the uses thereof. In one aspect, it provides a cyano-β-fructopyranoside compound of the formula wherein R1is CH2-OH, C(=O)OH or C(=O)O-M+, and M is a metal cation, preferably an alkali metal cation, or an ammonium cation. These compounds are suitably used as intermediate in the synthesis of a fructose-based surfactant as herein disclosed. In a specific aspect, R1is CH2-OH and the cyanoethyl β-fructopyranoside is of the formula It is readily obtained by the unique reaction of a fructose-containing saccharide with 3-hydroxy propionitrile under acid conditions (see herein above). This compound is advantageously used as intermediate compound in the synthesis of a fructose-based surfactant as herein disclosed. In another embodiment, R1is C(=O)OH or C(=O)O-M+, wherein M is a metal cation, preferably an alkali metal cation, or an ammonium cation. This oxidized intermediary compound can be obtained as described herein above. A further embodiment relates to an amine-β-fructopyranoside compound of the formula wherein R1is CH2-OH, C(=O)OH or C(=O)O-M+, and M is a metal cation, preferably an alkali metal cation such as Na, K, Li, or an ammonium cation; R2is H, C1-C8 alkyl or benzyl. Also provided is amine-intermediate compound In one aspect, R1is CH2-OH. In another aspect, R1is C(=O)OH or C(=O)O- M+, and M is a metal cation, preferably an alkali metal cation, or an ammonium cation. The amine-intermediate compound may comprise a primary amine moiety (R2is H) or a secondary amine moiety (R2is C1-C8 alkyl or benzyl). A primary amine moiety is readily obtained by the catalytic hydrogenation of the cyano-intermediate compound, preferably in the presence of ammonia. A secondary amine moiety wherein R2is C1-C8alkyl or benzyl is readily obtained by the catalytic hydrogenation of the cyano-intermediate compound in the presence of an amine additive of the formula NH2R2wherein R2, is C1-C8alkyl or benzyl. In one aspect, R2is C1-C3alkyl, C1-C6alkyl, C2-C4 alkyl, C4-C6 alkyl, C5-C8 alkyl. In another aspect, R2is benzyl. In one embodiment, R1is CH2-OH and R2is H, C1-C8 alkyl or benzyl, preferably H. In a specific aspect, the invention provides the compound (2R,3S,4R,5R)-2- (2-aminopropoxy)-2-(hydroxymethyl)tetrahydro-2H-pyran-3,4,5-triol (compound 2 herein below). In another embodiment, R1is C(=O)OH or C(=O)O-M+, and R2is H, C1-C8 alkyl or benzyl. In yet another embodiment, R1is CH2-OH, C(=O)OH or C(=O)O-M+, and R2is H. In yet another embodiment, R1is CH2-OH, C(=O)OH or C(=O)O-M+, and R2is C1-C8 alkyl or benzyl. Also provided is a fructose-based surfactant molecule obtainable by a method according steps (i)-(iii) or (i)-(iv) according to the invention, or by any other method using a beta-fructopyranoside cyano- or amine- intermediate compound as provided herein. In a preferred aspect, the invention provides a fructose-based surfactant molecule of the general formula I wherein R1is CH2-OH, C(=O)OH or C(=O)O-M+, and M is a metal cation, preferably an alkali metal cation, or an ammonium cation; R2is H, C1-C8 alkyl or benzyl; and A is an aliphatic C3-C21 moiety. Preferred R1and R2groups are defined herein above for the intermediate compounds. The aliphatic moiety A may be linear or branched, preferably linear. It may be saturated or unsaturated, preferably saturated or mono- unsaturated. Suitable examples include hydrocarbon chains comprising 3 to 9, 5 to 21, 5 to 17, 7 to 15, 7 to 17, 9 to 17, 11 to 21 or 13 to 17 C-atoms. In one aspect, the invention provides a fructose-based surfactant molecule of the formula wherein n is 2 to 20. Some preferred surfactant molecules have a combined total of no more than 20 carbon atoms counted in the hydrophobic R1and A moieties. Suitably, the number of such hydrophobic group carbon atoms totals from about 6 to 20, especially from about 8 to 18, with the A moiety providing at least 6 of the carbon atoms. These hydrophobicity limitations can provide optimal grease detergency effectiveness e.g. in detergent compositions. In one aspect, the invention provides a fructose-based surfactant molecule wherein R1is H, R2is CH2-OHand / orA is an aliphatic C5-C17 moiety. For example, provided is a fructose-based surfactant molecule of the formula Specific exemplary surfactants include: N-(3-(((2R,3S,4R,5R)-3,4,5-trihydroxy-2-(hydroxymethyl)tetrahydro-2H- pyran-2-yl)oxy)propyl)octanamide 12 N-(3-(((2R,3S,4R,5R)-3,4,5-trihydroxy-2-(hydroxymethyl)tetrahydro-2H- pyran-2-yl)oxy)propyl)decanamide 13 N-(3-(((2R,3S,4R,5R)-3,4,5-trihydroxy-2-(hydroxymethyl)tetrahydro-2H- pyran-2-yl)oxy)propyl)dodecanamide 14 N-(3-(((2R,3S,4R,5R)-3,4,5-trihydroxy-2-(hydroxymethyl)tetrahydro-2H- pyran-2-yl)oxy)propyl)palmitamide 15 N-(3-(((2R,3S,4R,5R)-3,4,5-trihydroxy-2-(hydroxymethyl)tetrahydro-2H- pyran-2-yl)oxy)propyl)oleamide 16 Surfactant products and applications Still further, the invention provides the use of a fructose-based surfactant molecule as herein disclosed as surface-activating agent, foaming or foam control agent, emulsifier or stabilizer. The fructose-based surfactant(s) may be non-ionic or anionic. They are suitably used in combination with one or more known surfactant types, e.g. in a (detergent) composition comprising a mixtures of anionic, cationic and nonionic surfactants. Suitable applications include industrial cleaning, oil recovery, foam inhibitors, personal care or household products. Hence, in one embodiment the invention provides a personal care or household product comprising one or more fructose-based surfactants as herein disclosed. For example, the product is a cleansing composition such as a soap, shampoo, liquid or powdered laundry detergent, toilet bowl cleaner or dishwashing detergent. Specific examples of the cleansing composition for hair include a hair shampoo. Specific examples of the cleansing composition for skin include a body shampoo, a facial cleanser, a makeup remover, or a hand soap. The cleansing composition may further comprise an adjunct cleaning additive selected from the group consisting of a builder, an organic polymeric compound, an enzyme, an enzyme stabilizer, a bleach system, a brightener, a hueing agent, a chelating agent, a suds suppressor, a conditioning agent, a humectant, a perfume, a filler or carrier, an alkalinity system, a pH control system, and a buffer, and mixtures thereof. Enzymes relevant in this field are proteases, cellulases, amylases and lipases. Preferred enzyme stabilizer include boron-free protease stabilizers, e.g. those described in EP2220204, US2010 / 0210502 or US 7,968,508. The cleaning / detergent compositions may comprise an additional surfactant (e.g., a second surfactant, a third surfactant) selected from the group consisting of anionic surfactants, nonionic surfactants, cationic surfactants, zwitterionic surfactants, amphoteric surfactants, ampholytic surfactants, and mixtures thereof. The additional surfactant may be a detersive surfactant, which those of ordinary skill in the art will understand to encompass any surfactant or mixture of surfactants that provide cleaning, stain removing, or laundering benefit to soiled material. The additional surfactant may comprise one or more anionic surfactants. Specific, non-limiting examples of suitable anionic surfactants include any conventional anionic surfactant. This may include a sulfate detersive surfactant, for e.g., alkoxylated and / or non-alkoxylated alkyl sulfate materials, and / or sulfonic detersive surfactants, e.g., alkyl benzene sulfonates. Suitable nonionic surfactants useful herein can comprise any conventional nonionic surfactant. These can include, for e.g., alkoxylated fatty alcohols and amine oxide surfactants. Non-limiting examples of cationic surfactants include: the quaternary ammonium surfactants, which can have up to 26 carbon atoms include: alkoxylate quaternary ammonium (AQA) surfactants; dimethyl hydroxyethyl quaternary ammonium; dimethyl hydroxyethyl lauryl ammonium chloride; polyamine cationic surfactants; cationic ester surfactants; and amino surfactants, e.g., amido propyldimethyl amine (APA). In one embodiment, from 0.1% to 100% of the carbon content of surfactant(s) in the product is derived from renewable sources. As used herein, a renewable sources is a feedstock that contains renewable carbon content, which may be assessed through ASTM D6866, which allows the determination of the renewable carbon content of materials using radiocarbon analysis by accelerator mass spectrometry, liquid scintillation counting, and isotope mass spectrometry. The detergent composition may be in a form selected from the group consisting of a granular detergent, a bar-form detergent, a liquid laundry detergent, a gel detergent, a single-phase or multi-phase unit dose detergent, a detergent contained in a single-phase or multi-phase or multi- compartment water soluble pouch, a liquid hand dishwashing composition, a laundry pretreat product, a detergent contained on or in a porous substrate or nonwoven sheet, an automatic dish-washing detergent, a hard surface cleaner, a fabric softener composition, and mixtures thereof. In a specific aspect, a non-ionic fructose-based surfactant as herein disclosed finds its use in powdered detergents for laundry washing machines, for example powdered detergents having a high cleansing capacity against dirt of the fatty type, and particularly for washing at low temperature. Usually, detergents for washing machines utilize mixtures of surfactants which have beside a good cleansing power also a good foam-control capacity during washing and rinsing. The foam-control is necessary to avoid that foam, by escaping out of the drum, may damage the washing machine. Moreover, the excess of foam hinders the mechanical flapping of linen within the washing machines, thus reducing the cleansing action of the detergent. LEGEND TO THE FIGURES Figure 1: (A)1H-NMR and (B)13C-NMR spectra of cyano-ethyl-β- fructopyranoside compound 1. Figure 2.1H-NMR of (2R,3S,4R,5R)-2-(2-aminopropoxy)-2- (hydroxymethyl)tetrahydro-2H-pyran-3,4,5-triol compound 2’. Figure 3.13C-NMR of (2R,3S,4R,5R)-2-(2-aminopropoxy)-2- (hydroxymethyl)tetrahydro-2H-pyran-3,4,5-triol compound 2. Figure 4.1H-NMR of N-(3-(((2R,3S,4R,5R)-3,4,5-trihydroxy-2- (hydroxymethyl)tetrahydro-2H-pyran-2-yl)oxy)propyl)octanamide surfactant 12. Figure 5.13C-NMR of N-(3-(((2R,3S,4R,5R)-3,4,5-trihydroxy-2- (hydroxymethyl)tetrahydro-2H-pyran-2-yl)oxy)propyl)octanamide surfactant 12. Figure 6. Surface tension versus surfactant concentration (log) measured in a pentane / water system. Figure 7. Foaming activity of exemplary surfactants 12 (panel A) and 13 (panel B) in water. Sample 1 shows water control. Sample 2 shows foaming at 1.5% (w / v) surfactant and sample 3 at 3% (w / v) surfactant. EXPERIMENTAL SECTION Materials and Methods Solvents and reagents All solvents and carbohydrates used for synthesis were commercially available, and used without further purification: 3-hydroxypropionitrile (Sigma-Aldrich), D-(−)-fructose (Sigma-Aldrich), inulin (Carbosynth), sucrose (Sigma-Aldrich), acetyl chloride (Sigma-Aldrich). Analysis1H-,13C-, COSY-, HSQC- and HMBC-NMR were recorded on a Varian AMX400 spectrometer (400, 100 MHz, respectively) using DMSO-d6 as solvent. Chemical shift values are reported in ppm with the solvent resonance as the internal standard (DMSO-d6: δ 2.50 for 1H, δ 39.52 for13C). Data are reported as follows: chemical shifts (δ), multiplicity (s = singlet, d = doublet, dd = double doublet, ddd = double double doublet, t = triplet, appt = apparent triplet, q =quartet, m = multiplet), coupling constants J (Hz), and integration. High-Resolution Mass spectrometry measurements were performed using a ThermoScientific LTQ OrbitrapXL spectrometer. A single crystal of compound 1 was mounted on top of a cryoloop and transferred into the cold nitrogen stream (100 K) of a Bruker- AXS D8 Venture diffractometer. Data collection and reduction was done using the Bruker software suite APEX3. The final unit cell was obtained from the xyz centroids of 8613 reflections after integration. A multiscan absorption correction was applied, based on the intensities of symmetry- related reflections measured at different angular settings (SADABS). The structures were solved by direct methods using SHELXT and refinement of the structure was performed using SHLELXL. The hydrogen atoms were generated by geometrical considerations, constrained to idealised geometries and allowed to ride on their carrier atoms with an isotropic displacement parameter related to the equivalent displacement parameter of their carrier atoms. EXAMPLE 1: Synthesis of cyanoethyl-β-fructopyranoside from D- Fructose This example describes the glycosidation of fructose or inulin in 3- hydroxypropionitrile, leading to the formation of the fructose-based surfactant precursor cyanoethyl-fructopyranoside. Preparation of cyanoethyl- ^-fructopyranoside 1 In a 250 mL round bottom flask, 0.3 mL of acetyl chloride was added to 30 mL 3-hydroxypropionitrile. This acidified solution was stirred for 15 min at rt with an overhead stirrer.30 g of D-(−)-fructose was added to the solution and stirring was continued for 4 h. During the reaction, D-(−)-fructose gradually dissolved in 10-30 min (not entirely dissolved). After 30 min, precipitation started and the mixture became a slurry. Subsequently, the slurry mixture was suspended in isopropanol. The suspended solid was collected by filtration under reduced pressure (using a fritted funnel with porosity 2, at 800 mbar). The collected solid was washed with isopropanol and dried in vacuum.66% yield of 1 was It is well-known that the crystallization of organic compounds can be unpredictable in terms of crystallization rate and small differences in the conditions. We recrystallized β-fructopyranoside 1 and analyzed it by X-ray diffraction. According to the X-ray structure (data not shown), the stereochemistry of 1 (and conceivably its conformation) was indeed as proposed the β-form, and the elemental composition of 1 is the same as expected. We also investigated whether the fructose-alcohol ratio was important to obtain an optimal yield of cyano-fructoside 1. Upon varying the fructose- alcohol ratio, precipitation started within 30 min after the start of the reaction, while the fructose was still dissolving. Therefore, we performed the glycosidation reaction for 4 h to ensure that fructose was entirely dissolved. As expected, a higher yield was obtained when the reaction was performed at a higher fructose-alcohol ratio. On the other hand, the results with 0.5 and 1 g / mL at 5 g scale led to 68% and 61%, respectively (Table 1, Entry 3 and 4). We considered these results comparable since the washing step after filtration caused a considerable experimental variation. The routine synthesis of 1 gives 55-65% yield, so has a band width of 10%. As the mixture turned thicker when the fructose-alcohol ratio increased, we noticed that magnetic stirring became difficult. Therefore, at a ratio 1 g / mL, the reactions were performed again with overhead stirring. According to the results (Table 1, Entry 5 and 6), the optimal ratio was indeed 1 g / mL. Table 1. Investigation of the fructose-alcohol ratio for an optimum yield of 1 Entry Fructose Fructose / Alcohol ratio Stirring Yield (g) (g / mL) Method 2 5 g 0.25 Magnetic 38% 3 5 g 0.5 Magnetic 68% 4 5 g 1 Magnetic 61% 5 10 g 0.5 Overhead 43% stirring 6 10 g 1 Overhead 54% stirring 1% HCl was made in situ by adding acetyl chloride to 3- hydroxypropionitrile (volume ratio = 1:40) EXAMPLE 2: Synthesis of Cyanoethyl-β-fructopyranoside from other fructose sources. Inulin is an oligo- or polysaccharide composed of fructofuranose and one terminal glucose. Sucrose is a disaccharide composed of one glucose unit and one fructofuranose unit. This example demonstrates that both inulin and sucrose can be alternative sources of fructose for the synthesis of 1. Synthesis of 1 from inulin In a 250 mL round bottom flask, 0.5 mL of acetyl chloride was added to 20 mL of 3-hydroxypropionitrile. The solution was stirred for 15 min at rt with an overhead stirrer.10 g of inulin was added to the solution and left stirring at rt for 4 d. Subsequently, the resulting slurry was mixed with isopropanol to give a suspension. The suspended solid was collected by filtration with reduced pressure (using a fritted funnel with porosity 2 and 800 mbar). The collected solid was washed with isopropanol and dried under vacuum.46% yield of 1 was obtained as a white solid. Synthesis of 1 from sucrose In a 250 mL round bottom flask, 2.5 mL of acetyl chloride was added to 100 mL 3-hydroxypropionitrile. The solution was stirred for 15 min at r.t. with an overhead stirrer.25 g of sucrose was added to the solution and left stirring at rt for 4 d. The remaining solid (undissolved sucrose) was collected by filtration and the filtrate was left stirring at r.t. for another 2 d. A small amount of precipitate was observed. The solid was collected by filtration to give a mixture of D-glucose and fructoside 1 in a 24% yield (combined yield). Whereas inulin has approx.90% fructose content, sucrose is composed of 50% glucose and 50% fructose. With the same loading of D-fructose and sucrose in the reaction, the fructose concentration is only half in the case of sucrose, resulting in a low fructose-alcohol ratio and therefore a low yield. In practice the situation is even worse as the solubility of sucrose in 3- hydroxypropionitrile is very low, slowing down the reaction considerably. We noted that 5 g inulin entirely dissolved in 20 mL acidified 3- hydroxypropionitrile, but only afforded 9% yield of 1 in 4 d. By adding more inulin to a given amount of alcohol a larger amount of product is formed, which induces precipitation. As expected, the yield indeed improved by increasing the amount of inulin although the effect seemed to level off when the inulin-alcohol ratio was higher than 0.5 (g / mL). The obtained yield increased from 9% to 46% when the inulin-alcohol ratio increased from 0.25 to 0.5 (g / mL), but the yield stayed at 42% when the ratio further increased to 1 (g / mL). Synthesis of 1 from High Fructose Corn Syrup 10 mL of 3-hydroxypropionitrile followed by the addition of 0.25 mL of acetyl chloride were placed in a 100 mL round bottom flask,. The solution was stirred for 15 min at rt upon which 4.5 g HFCS (High fructose corn syrup) consisting of a 9 : 1 mixture of D-fructose and D-glucose was added. After 10 min precipitation started. After 4 h the slurry mixture was suspended in isopropanol. The suspended solid was collected by filtration under reduced pressure (using a fritted funnel with porosity 2, at 800 mbar). The collected solid was washed with isopropanol and dried in vacuum. A white solid was obtained. NMR analysis indicated that 1 was the only product formed containing a tiny amount of unreacted D-glucose (around 4%).3.2 g of white solid was obtained, 56% yield. Scheme 5. Synthesis of 1 from High fructose corn syrup EXAMPLE 3: Oxidation of 1 to the corresponding carboxylic acid To a 5 mL electrasyn vial equipped with a stirring bar intermediate compound 1 (175 mg, 0.75 mmol) and TEMPO (23.6 mg, 0.2 mmol, 0.2 equiv) were added. Demi water was added and the mixture was stirred for a few seconds. Ammonia (0.1 mL, 1.5 mmol, 2 equiv, 25% in water) was added and the vial was capped with the Teflon electrode bracket equipped with 2 graphite electrodes. The oxidation reaction was performed at 10 mA at 10 F / mol. Upon completion, the reaction mixture was concentrated in vacuo to obtain an off-white foam which essentially is the desired ammonium carboxylate of the cyano-intermediate compound. EXAMPLE 4: Hydrogenation of cyanoethyl-fructopyranoside This example describes the second step of the synthesis of a fructose-based surfactant, involving the hydrogenation of cyanoethyl-fructopyranoside 1 using two different catalysts. To a 300 mL autoclave, 5 g of fructose, 487 mg of PtO2 (10 mol%), and 60 mL MeOH were added. The autoclave was sealed and flushed with N2three times. Subsequently, the autoclaved was flushed with H2three times, and H2 was charged to the autoclave to a pressure of 50 bar. The reaction mixture was left stirring at 50ºC overnight. Afterward, the mixture was filtered through celite, and the filtrate was concentrated to yield a quantitative yield of 2 as a colorless syrup. The resulting syrup was directly used for amidation without further purification. Hydrogenation with Raney Nickel To a 100 mL three-neck flask, 1.2 g of fructose, 57 mg of Raney nickel (15 wt%, suspension in water), and 40 mL MeOH were added under N2. The system was attached to a H2balloon, and flushed with H2three times. The reaction mixture was left stirring at 50ºC overnight. Afterward, the mixture was filtered through celite, and the filtrate was concentrated including co- evaporation with 1-methoxy-2-propanol to yield a quantitative yield of 2 as a colorless syrup. The resulting syrup was directly used for amidation without further purification. Scheme 6. Hydrogenation of 1 to 2. a) PtO2 (10 mol%), H2 (50 bar), 50ºC for 18 h, and b) Raney nickel suspension (15 wt%), H2(1 bar), 50ºC for 18 h. (2R,3S,4R,5R)-2-(2-aminopropoxy)-2-(hydroxymethyl)tetrahydro-2H-pyran- 3,4,5-triol 2 Hydrogenation of nitriles to primary amines often suffers from a side reaction in which the intermediate imine reacts with an equivalent of the already formed primary amine. This trans-imination reaction is followed by hydrogenation and leads to formation of the undesired secondary amine and ammonia. This example demonstrates that addition of ammonia improves the selectivity of hydrogenation to the primary amine. Hydrogenation with Raney Nickel in the presence of ammonia To a 100 mL three-neck flask, 1 g of fructose, 50 mg of Raney nickel (15 wt%, suspension in water), and 30 mL MeOH were added under N2. The system was attached to a H2 balloon, and flushed with H2 three times.11 mL of NH3 (7 M in MeOH, 19 eq.) was added. The reaction mixture was left stirring at 50ºC overnight. Afterward, the mixture was filtered through celite, and the filtrate was concentrated including co-evaporation with 1- methoxy-2-propanol to yield a quantitative yield of 2 as a colorless syrup. The resulting syrup was directly used for amidation without further purification. In order to monitor the level of side products formed, a proper analysis method was required. We performed GC analysis of the reaction mixture to compare the hydrogenation reaction with and without NH3(data not shown). A reaction aliquot was treated with N-methyl- bis(trifluoroacetamide) (MBTFA) and analyzed on a DB-5 column. The retention time of per-trifluoroacetylated amino-fructoside 2 was 11.9 min with the indicated temperature program. In the chromatogram of the reaction without NH3, two additional peaks were observed at 15.5 and 15.8 min. According to GC-MS (data not shown) their mass corresponded to dimers. Based on the GC-analysis, it is concluded that the addition of ammonium improves the selectivity of hydrogenation to the primary amine. Next, it was recognized that the hydrogenation / amine additive approach can also be used to introduce a secondary amine moiety in the surfactant molecule. To that end, cyano-intermediate 1 is reduced in the presence of a primary amine additive of the formula NH2R2, such as ethylamine, to convert the nitrile group into a secondary amine group wherein the R2group is attached directly to the nitrogen atom. The secondary amine can then be subjected to the amidation reaction. To a 100 mL two-neck flask, 150 mg of Raney Nickel was washed with MeOH under N2to remove water.30 mL of MeOH was added and the system was bubbled with H2 for 5 min.1 g of 1 was added, the mixture was bubbled again with H2 for 5 min upon which amine additive EtNH2 (2 M in MeOH, 7 eq.) was added and the mixture was stirred at 50 ºC overnight. The mixture was filtered over celite, washed with MeOH. NMR analysis indicated a mixture of the primary amine (2) and the secondary amine (2a). EXAMPLE 6: Amidation reaction to form a fructose-based surfactant. This example describes the amidation reaction of a method according to the invention. Herein, the amine-intermediate compound is reacted in the presence of a strong base with at least one (alkyl or glycerol) ester of an aliphatic C6-C22 carboxylic acid to obtain a fructose-based amphipathic molecule. Under an inert atmosphere, 5 g compound 2 was dissolved in 20 mL anhydrous MeOH. A freshly prepared solution of NaOMe was added (1.26 M in MeOH, 1 eq.), the mixture was stirred at 60 ºC for 10 min, upon which 1.2 eq. of FAME (C8-C18) was added and the mixture was stirred at that temperature for 6 h. The mixture was diluted with MeOH and neutralized by Amberlyst® 15 hydrogen form until pH~7. The liquid phase was collected and partly removed under reduced pressure. Heptane or acetone was added to the resulting mixture to yield an off-white precipitate. The precipitate was collected by filtration and washed with pentane under reduced pressure (800 mbar). The precipitate was the fructose-based surfactant as an off- white solid (60%-80% yield depending on the FAME used). For methyl octanoate:1H NMR (400 MHz, CD3OD) δ 3.91 (d, J = 9.8 Hz, 1H), 3.86 – 3.83 (m, 1H), 3.81 – 3.77 (m, 1H), 3.77 – 3.74 (m, 1H), 3.74 – 3.69 (m, 2H), 3.66 (dd, J = 12.3, 1.9 Hz, 1H), 3.62 – 3.51 (m, 2H), 3.31 – 3.25 (m, 2H), 2.18 (t, J = 7.5 Hz, 2H), 1.76 (td, J = 6.3, 3.3 Hz, 2H), 1.60 (t, J = 7.3 Hz, 2H), 1.39 – 1.26 (m, 8H), 0.94 – 0.86 (m, 3H).13C NMR (101 MHz, CD3OD) δ 176.3, 101.6, 71.5, 71.0, 70.8, 65.3, 63.6, 59.6, 37.8, 37.2, 32.9, 30.6, 30.3, 30.2, 27.1, 23.7, 14.4 m.p. = 101oC [α] = -86.0oHRMS (ESI) calculated for C17H33NO7([M+H]+): 364.2330, found: 364.2330. For methyl decanoate:1H NMR (400 MHz, CD3OD) δ 3.91 (d, J = 9.8 Hz, 1H), 3.87 – 3.83 (m, 1H), 3.79 (dd, J = 9.8, 3.5 Hz, 1H), 3.77 – 3.74 (m, 1H), 3.74 – 3.69 (m, 2H), 3.68 – 3.62 (m, 1H), 3.62 – 3.50 (m, 2H), 3.31 – 3.25 (m, 2H), 2.18 (t, J = 7.6 Hz, 2H), 1.76 (td, J = 6.5, 3.4 Hz, 2H), 1.60 (t, J = 7.2 Hz, 2H), 1.40 – 1.20 (m, 12H), 0.90 (t, J = 6.6 Hz, 3H).13C NMR (101 MHz, CD3OD) δ 176.3, 101.6, 71.5, 71.0, 70.8, 65.3, 63.5, 59.6, 37.8, 37.2, 33.0, 30.61, 30.57, 30.5, 30.4, 30.3, 27.1, 23.7, 14.4 m.p. = 81oC [α] = -74.8oHRMS (ESI) calculated for C19H37NO7([M+H]+): 392.26428, found: 392.2644. For methyl dodecanoate:1H NMR (400 MHz, CD3OD) δ 3.91 (d, J = 9.8 Hz, 1H), 3.87 – 3.83 (m, 1H), 3.79 (dd, J = 9.9, 3.4 Hz, 1H), 3.77 – 3.74 (m, 1H), 3.74 – 3.69 (m, 2H), 3.66 (dd, J = 12.3, 1.9 Hz, 1H), 3.60 – 3.53 (m, 2H), 3.32 – 3.25 (m, 2H), 2.18 (t, J = 7.5 Hz, 2H), 1.76 (td, J = 6.4, 3.4 Hz, 2H), 1.60 (t, J = 6.9 Hz, 2H), 1.37 – 1.23 (m, 16H), 0.90 (t, J = 6.8 Hz, 3H).13C NMR (101 MHz, CD3OD) δ 176.3, 101.6, 71.5, 71.0, 70.8, 65.3, 63.6, 59.6, 37.8, 37.2, 33.1, 30.73, 30.72, 30.63, 30.57, 30.46, 30.45, 30.3, 27.1, 23.7, 14.4 m.p. = 104oC [α] = -75.2oHRMS (ESI) calculated for C21H41NO7 ([M+H]+):420.29558, found: 420.29543. For methyl stearate:1H NMR (400 MHz, DMSO-d6) δ 7.66 (t, J = 5.5 Hz, 1H), 4.54 – 4.35 (m, 3H), 4.34 – 4.25 (m, 1H), 3.70 (d, J = 9.8 Hz, 1H), 3.66 – 3.62 (m, 1H), 3.56 (dd, J = 9.9, 3.5 Hz, 1H), 3.54 – 3.43 (m, 4H), 3.38 (td, J = 6.3, 3.8 Hz, 2H), 3.08 (q, J = 6.5 Hz, 2H), 2.00 (t, J = 7.4 Hz, 2H), 1.57 (p, J = 6.5 Hz, 2H), 1.44 (p, J = 7.0 Hz, 2H), 1.21 (bs, 24H), 0.87 – 0.79 (m, 3H).13C NMR (101 MHz, DMSO-d6) δ 172.0, 100.2, 69.4, 69.1, 69.0, 63.9, 62.0, 57.8, 35.9, 35.4, 31.3, 29.6, 29.03 (three overlapping signals), 29.01 (two overlapped signals), 28.98, 28.9, 28.8, 28.68, 28.66, 25.3, 22.1, 13.9 m.p. = 110oC HRMS (ESI) calculated for C25H49NO7 ([M+H]+):476.35787, found: 476.3582. For methyl oleate: NMR (400 MHz, CD3OD) δ 5.34 (td, J = 4.4, 2.2 Hz, 2H), 3.91 (dd, J = 9.8, 1.0 Hz, 1H), 3.86 – 3.83 (m, 1H), 3.79 (ddd, J = 9.9, 3.5, 1.0 Hz, 1H), 3.76 – 3.74 (m, 1H), 3.74 – 3.68 (m, 2H), 3.68 – 3.63 (m, 1H), 3.57 (td, J = 6.0, 4.2 Hz, 2H), 3.29 (t, J = 5.6 Hz, 2H), 2.18 (t, J = 7.5 Hz, 2H), 2.03 (q, J = 6.1 Hz, 4H), 1.76 (td, J = 6.5, 3.5 Hz, 2H), 1.60 (p, J = 7.2 Hz, 2H), 1.33 (bs, 11H), 1.30 (bs, 9H), 0.94 – 0.86 MHz, CD3OD) δ 176.3, 130.9, 130.8, 101.6, 71.5, 71.0, 70.8, 65.3, 63.6, 59.6, 37.8, 37.2, 33.1, 30.8 (two overlapped signals), 30.61, 30.58, 30.44, 30.37, 30.34, 30.32, 30.25, 28.14, 28.13, 27.1, 23.7, 14.5 m.p. = 107oC [α] = -66.4oHRMS (ESI) calculated for C27H51NO7 ([M+H]+):502.37383, found: 502.3733. EXAMPLE 7: Amidation performed on hydrogenation reaction product. This example describes that the amidation reaction can be performed directly on the product of the hydrogenation reaction, i.e. without celite filtration and solvent removal of the hydrogenated intermediate compound. Upon completion of the hydrogenation reaction, the reaction mixture was filtered to remove the solid catalyst whereby the filtrate was collected in a second flask. The volume of methanol was reduced by evaporation under reduced pressure to obtain the desired concentration of compound 2 (see example above). Subsequently, the amidation reaction was initiated by addition of the required amount of strong base (e.g. NaOMe) and A-ester, e.g. FAME. The remainder of the procedure was identical to that of the amidation reaction described above. EXAMPLE 8: Surface active properties of the fructose-based surfactants. The critical micelle concentration (CMC) is an important characteristic of surfactants since it indicates the minimum required amount of a surfactant to maximally reduce the surface tension of water. This example describes CMC measurements conducted on a series of representative fructose-based surfactants according to the invention. To perform CMC measurements, we utilized the pendant drop method in a water-pentane system. The reported interfacial tension of that system is 48.7 mN / m at 26 ºC, and this value decreases with increasing temperature (H. Matsubara et al. Int. J. Thermophys.1988, 9, 409-424). According to our measurements at ambient temperature, the C8, C10, and C12-surfactants (12, 13, and 14) reached their CMC at 61.9, 6.4, and 0.6 mM, respectively (Figure 6). With 12, the interfacial tension was reduced to 7.7 mN / m when the concentration reached the CMC. For 13 and 14 this resulted in values of 4.7 and 2.4 mN / m at their CMC. These results show that the CMC reduces with increasing chain length (roughly one order of magnitude per “ethyl unit”), as expected, while surfactants with longer tails provide a somewhat lower surface tension. Decyl β-glucopyranoside was selected in order to compare the novel surfactants to existing surfactants. Decyl β-glucopyranoside (C10-glucoside) is a glucose-based surfactant which is commonly used as a solubilizer, emulsifier, and foaming detergent. It is synthesized by the glycosidation of glucose, and it is a good example of a renewable surfactant. An important difference with the surfactants of the present invention is that it does not contain an amide (or an ester). The CMC and interfacial tension of the C10-surfactant 13 was compared with those of decyl glucopyranoside. The choice for 13 is somewhat arbitrary; although both surfactants have a C10 hydrocarbon chain, 13 has in addition a C3 “spacer” and an amide function. According to measurement at ambient temperature, decyl glucopyranoside has a CMC of 2.5 mM, and the interfacial tension between water and pentane is 0.7 mN / m. (reported CMC = 2.2 mM, K. Shinoda et al. Bull. Chem. Soc. Jpn 1961, 34, 237-241). On the other hand, C10-surfactant 13 has a CMC of 6.4 mM and a surface tension of 4.7 mN / m. Exemplary surfactants 12 and 13 were also evaluated with respect to their foaming properties. To that end, three glass vials containing either water (control) or 0.5 or 1% (w / v) of surfactant in water were prepared. Foam formation was induced by vigorously shaking the vials for 25 s. After approx.1 min a photo was taken to show foaming behavior. As shown in Figure 7, both the C8 and C10 surfactants gave a stable foam layer (indicated by single braces). In view of the above, it is concluded that fructose-based surfactants as herein disclosed have bona fide surface-active / foaming properties.

Claims

Claims 1. A method for the synthesis of a carbohydrate surfactant molecule, comprising the steps of: (i) reacting a fructose-containing saccharide with 3-hydroxy propionitrile under acid conditions to obtain the cyano-intermediate compound cyanoethyl β-fructopyranoside; (ii) hydrogenating the cyano-intermediate compound in the presence of a catalyst to obtain an amine-intermediate compound; and (iii) amidating said amine moiety by contacting the amine- intermediate compound with at least one alkyl ester or glycerol ester of a saturated or unsaturated, optionally substituted, aliphatic C4-C22carboxylic acid in the presence of a base to obtain a fructose-based surfactant molecule.

2. The method according to claim 1, wherein said fructose-containing saccharide is D-fructose, sucrose, inulin, high fructose corn syrup, or a mixture thereof.

3. The method according to claim 1 or 2, wherein hydrogenation step (ii) is performed at atmospheric pressure, preferably in the presence of catalytic Raney Nickel.

4. The method according to any one of the preceding claims, wherein hydrogenation step (ii) is performed in the presence of at least 1 equivalent of an amine additive of the formula NH2R2, wherein R2is H, C1-C8 alkyl or benzyl.

5. The method according to claim 4, wherein the amine additive is a primary amine additive NH2R2wherein R2is C1-C8alkyl or benzyl, preferably wherein the primary amine additive is ethylamine, to obtain an amine-intermediate compound comprising a secondary amine moiety.

6. The method according to any one of the preceding claims, wherein amidation step (iii) comprises reacting the amine-intermediate compound with at least one alkyl ester of a C4-C22carboxylic acid, preferably a C1-C4alkyl ester of a C4-C22 carboxylic acid, more preferably a C1-C4 alkyl ester of a C6-C22carboxylic acid, most preferably a methyl ester of a C8-C18carboxylic acid.

7. The method according to any one of the preceding claims, wherein amidation step (iii) comprises reacting the amine-intermediate compound with at least one glycerol ester of a C4-C22 carboxylic acid, preferably with glycerol esterified to one, two or three C4-C22carboxylic acid(s), more preferably mono-, di- or triacylglycerol comprising C6-C22 carboxylic acid(s), most preferably C8-C18carboxylic acid(s).

8. The method according to any one of the preceding claims, further comprising the step of oxidizing the primary hydroxyl of the fructose-moiety to a carboxylic acid and converting the carboxylic acid to a carboxylic acid salt, preferably wherein said oxidation step is performed on the cyano- intermediate compound.

9. A beta-fructopyranoside compound of the formulawherein R1is CH2-OH, C(=O)OH or C(=O)O-M+, and M is a metal cation, preferably an alkali metal cation, or an ammonium cation;R2is H, C1-C8 alkyl or benzyl.

10. The beta-fructopyranoside compound according to claim 9, being11. A fructose-based surfactant molecule obtainable by any one of steps (i) to (iii) of a method according to any one of claims 1-8, or by any synthetic reaction using a beta-fructopyranoside compound according to claim 9 or 10 as reaction intermediate.

12. A fructose-based surfactant molecule of the general formula Iwherein R1is CH2-OH, C(=O)OH or C(=O)O-M+, and M is a metal cation, preferably an alkali metal cation, or an ammonium cation; R2is H, C1-C8alkyl or benzyl;A is a saturated or unsaturated, optionally substituted, aliphatic C3-C21 moiety.

13. The fructose-based surfactant molecule according to claim 12, wherein R1is H, R2is CH2-OH,and / orA is an aliphatic C5-C17 moiety.

14. The fructose-based surfactant molecule according to claim 12 having the formulawherein n is 2 to 20.

15. The fructose-based surfactant molecule according to claim 14, wherein the surfactant molecule is16. A personal care or a household product comprising one or more fructose-based surfactant(s) according to any one of claims 11-15.

17. The personal care or a household product according to claim 16, selected from the group consisting of a cleansing composition, a soap, shampoo, cosmetic product, laundry detergent, toilet bowl cleaner and a dishwashing detergent.

18. Use of a fructose-based surfactant molecule according to any one of claims 11-15 as surface-activating agent, foaming agent, foam control agent, emulsifier and / or stabilizer.

19. The use according to claim 18 as surface-activating agent, foaming agent, foam control agent, emulsifier and / or stabilizer in a personal care or household product.

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