CA1095075A - Sulfoalkylated flavanone sweeteners - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A group of novel dihydrochalcone compounds represented by the formula

Description

~5075 This is a division of our Canadian patent application, Serial No.
248,600, filed March 23, 1976.
This invention relates to new ionic dihydrochalcone and flavanone compounds and to consumable materials such as foods sweetened by the addition of these compounds.
There is a trend toward the use of more and more sweetening by the world's population. Primarily, this sweetening is obtained from sucrose.
Sucrose has several medical disadvantages, including high caloric content, which promotes obesity; ability to cause dental caries; and nontolerance by diabetics. Nonetheless, it is the consumer's sweetener of choice, the stan-dard to which any synthetic alternative must compare. In sum, the ideal syn-thetic sweetener will taste like sucrose without any extra accompanying tastes or aftertastes.
Another required characteristic of a synthetic sucrose substitute is nontoxicity. It was the suspicion of carcinogenicity which led to banning in the United States of the cyclamates, a once-popular group of sweeteners.
A class of sweeteners which has received good marks for nontoxicity are the dihydrochalcones. Initially, these materials were made by isomerizing and opening certain bitter flavanone components of several citrus fruits such as is exemplified by the conversion of the naturally occurring flavanone, nar-ingin, to naringin dihydrochalcone:
(R=~-neohesperidosyl) H OH ~ R-O ~ OH ~ 9H

Naringin (Bitter) Naringin chalcone ~Ji~

lO~S0~5 R-O ~ OU ~ OH

OH

Naringin dihydrochalcone (Sweet).
Now, a variety of synthetically-derived materials have been proposed as well.
These materials share a basic structure.

o 3~C-CIl -C}l -with a great variety of groups substituted into the two aromatic rings. As pointed out in Horowitz and Gentili's United States Patents 3,087,821, issued April 30, 1963, and 3,583,&94j issued June 8, 1971 and in their chapter in the book Sweetness and Sweeteners, Birch, Green, and Coulson, Eds., Applied Science Publ., Ltd., London, pp. 69-79 (1971), the exact nature of the substituents and their placement on the molecule are critical to the taste properties of the dihydrochalcone. ~any dihydrochalcones prepared heretofore have menthol-like aftertastes and prolonged sweet aftertastes. Some dihydrochalcones hav-ing a R ~ ~-CH -CH ~ 2 R ~ ~ structure OH

are known wherein R is hydrogen, hydroxyl, alkoxyl, or substituted alkoxyl, Rl is hydrogen or a "hydrophylous" group such as carboxyl, sulfonyl, or phosphonyl, and R2 and R3 are hydrogen or alkoxyls, which are chemically related to the present invention, have been evaluated and found to have unpleasant aftertastes.

~0~5~75 They pose a second problem, as well, in that their sweetness, relative to sucrose, is not immense. Since the dihydrochalcones are likely expensive materials it is desirable that a dihydrochalcone have a very high sweetening power so that the amount used may be reduced. Another failing of many dihy-drochalcone materials disclosed heretofore has been insufficient solubility in aqueous media.
While in a few cases yielding sweet dihydrochalcones, dihydrochal-cone precursor flavanones in the art themselves are generally bitter or taste-less. Horowitz, in Chapter 14 of Biochemistry of Phenolic Compounds, Harborne Ed., (Academic Press, lg64) pp. 555-556 reports that, aside from one material, hesperetin, which has slight sweetness, flavanones useful as dihydrochalcone sweetener precursors which he examined were tasteless or bi~ter. Similar results are reported by Horowitz and Gentile at Agr. and Food Chem. Volume 17, No. 4 pp. 696 (1969) and by Kamiya et al at Agr. Biol. Chem. Volume 39, pp.
1757 (1975).
A group of high solubility dihydrochalcones which have particularly desirable taste properties has now been discovered. These materials have the chemical structure represented by General Structural Formula I, H \ OH ll OH
~ ~ ~
MO- -(CH2)n-o- ~ ~-CH -CH ~ OR (I) H OH H OH
wherein M is a physiologically acceptable cation, or hydrogen n is 1, 2 or 3 and R is methyl, ethyl or propyl. These compounds have tastes characterized by sweetness and no appreciable aftertaste or companion taste. Compared to many dihydrochalcones proposed heretofore, they are very water-soluble so that intense sweet flavors can be generated. The compounds can be formed from new flavanones represented by General Structural Formula II, ~IO~S07~

H OR
~< ;
H ~ C ~ OH

H O ~ H (II) M-O-~-(CH2)n H OH

In this Detailed Description, references will repeatedly be made to the positions of various substituents on the dihydrochalcone and flavanone molecules. These positions are numbered and will be referenced in accordance with General Formulae ~I) and (II~.
The dihydrochalcones of this invention contain three hydroxyl groups at the 2, 6 and 3' positions. The dihydrochalcones contain hydrogens at the 3, 5, 2', 5', and 6' positions. At the 4' position they contain a lower sat-urated alkoxy group of from one to three carbon atoms, that is one selected from the group of methoxy, ethoxy and the propoxies; preferably the 4'-substi-tuent is a methoxy or n-propoxy, and most preferably a methoxy. At the 4 position they contain a substituted oxy group. This oxygen atom is substi-tuted with an alkyl sulfonate anion to yield an oxyalkylsulfonate anion of from one to three carbon atoms inclusive. The alkyl sulfonate anion is pres-ent as the acid or a salt with a physiologically acceptable metal cation. As used herein, a "physiologically acceptable metal cation" is defined to include Li and the cations of the third and fourth period metals which are nontoxic, i.e., Na , K , Mg 2, Ca 2, Al 3, Mn 2, Fe 3, Cu 2 and Zn 2. Preferred metal cations are the cations of the third and fourth period group I and II metals, i.e., Na , K , Mg and Ca . -- 4 --~0~5075 Preparation The dihydrochalcones of General Formula I can be prepared by isomer-izing with base and hydrogenating the flavanones of General Formula II.
The flavanone materials are conveniently formed, in a general sense, by the mechanism of alkylating the 4-hydroxyl group of the natural product hesperetin H

~r OH
(or a 4'-ethoxy or propoxy equivalent of hesperet m) with a one to three car-bon alkyl sulfonate group.
The 4-ethoxy or propoxy equivalent of hesperetin can be conveniently prepared by the Aldol condensation of phloroacetophenone with the appropriate 4-alkoxy-3-hydroxy-benzaldehyde, followed by acid catalyzed cyclization of the result-ing chalcone.
In the case when n in General Formulae I and II equals 1, sodium iodomethanesulfonate or the pyrrolidine amide of chloromethylsulfonic acid are suitable agents with which to effect alkylation. More specifically, by the first route hesperetin or a 4'-ethoxy or methoxy equivalent can be reacted with the sodium salt of iodomethanesulfonic acid in the presence of potassium car-bonate in DMF at reflux for several hours to yield at the 4 position of the hesperetin (or its equivalent) a sulfo-substituted methoxy. In the second route, chloromethylsulfenyl chloride is first prepared by contacting trithiane, r S
S ~, with molecular chlorine. The chloromethylsulfenyl chloride can then ~0~50~5 . ~ ~
be reacted with pyrrolidine, ~ NH, to form ClCH2S-N ~ , which will facilely alkylate hesperetin ~or the 4' ethoxy or propoxy equivalent) in the 4 position and, after S oxidation and sulfonamide hydrolysis, yields the desired sulfomethoxy flavanone.
In the case where n in General Formulae I and II equals 2, the alky-lating agent can be Br-CH2-CH2-S03 Na , or the like. This material, when con-tacted with an equimolar amount of hesperetin (or a 4' ethoxy or propoxy equivalent) in the presenc0 of potassium carbonate or a similar weak base, in DMF, DMS0, or the like preferentially alkylates the 4-hydroxyl. There is, of course, as with all these reactions, some alkylation of other hydroxyls. The various materials may be separated and the desired 4-alkylate recovered by fractional crystallization or chromatography techniques.
In the case where n in General Formulae I and II equals 3, propane sultone is the alkylating agent of choice, as it directly attaches the required three carbon alkyl group and the S03 in one step. This alkylation is carried out in DMF or DMS0 or an equivalent dipolar aprotic solvent in the presence of sodium carbonate or a like weak base.
All of these alkylations can be carried out under relatively mild conditions, such as about room temperature for 24 to 72 hours. It is also possible to use elevated temperatures, such as up to about 100C with corre-sponding shorter reaction times such as as short as about 1 hour.
As above noted, in one use the flavanones are converted to the dihy-drochalcones by ring opening and reduction.
The ring opening and reduction may be carried out in two steps -opening and then hydrogenating. The opening is brought about by contacting the alkylation product with a relatively strong base such as an aqueous alkali metal hydroxide solution for 0.2 to 4 hours at 10C to 100C. The hydrogena-~9507~

tion can be carried out with hydrogen gas and a hydrogenation catalyst suchas a supported noble metal (e.g., platinum or palladium) catalyst or a nickel catalyst or the like at a temperature of from 10C to 100C for from 0.5 to 24 hours. Preferably the reduction and opening are carried out simultaneously with base, catalyst and hydrogen being present at once.
In an alte-rnate preparative scheme, the dihydrochalcones are pre-pared by condensing an appropriate ~,6-dihydroxy-4-sulfo-alkyloxy-acetophenone with an appropriate 3-hydroxy-4-alkoxy-benzaldehyde in the presence of base and then reducing. A typical reaction scheme is as follows:

OH

o ~-(CH2) - ~ 3 C ~ O-(CH2)2-CH~ OH >

OH OH

OH

0-3-(CH2)z-O ~ ~ t~ V~t OH 0}l OH OH
0-~-(CH2)2-0 ~ C-CH -CH - ~ ( 2)2 3 OH OH

The condensation is effected under moderate conditions (10-100C for 24 to 1 hour~ in the presence of strong base, such as alcoholic alkali metal hydroxide.
The products of any of these reactions can be purified and isolated by fractional crystallization, thin layer chromatography and the like, as O~S

desired.
The preparative schemes set forth above depict sodium as the cation.
~y varying starting materials among potassium, calcium and the like salts, or, in the case of the dihydrochalcones, varying the base used to effect opening, a variety of metal cations can be incorporated. Treatment with H can yield the acid. Also, it is possible to change cations by passage of a solution of flavanone over an appropriately charged ion exchange resin or often by merely adding an excess of the desired cation to a solution of flavanone or dihydro-chalcone and precipitating the desired salt.
Use of the Compounds The flavanones are useful as chemical intermediates in the prepara-tion of the new sweet and water soluble 4-sulfonate-alkoxy-substituted dihy-drochalcones. (The term "water soluble" as used throughout this application is defined to mean a solubility in neutral room temperature water of not less than 100 parts per million by weight.) The dihydrochalcones find application as sweeteners of consumable materials. In this use they are admixed with edible materials such as foods, beverages, medicines, and the like, in amounts effective for affording the degree of sweetness desired.
The compounds represented by Formulae I can be prepared in a variety of forms suitable for the utilization of sweetening agents. Typical forms which can be employed are: solid forms such as powders, tablets, and granules;
and liquid forms such as solutions, suspensions, syrups, and emulsions. These forms can consist of the compounds of Formula I apart from or in association with nontoxic sweetening agent carriers, i.e., nontoxic substances commonly employed in association with sweetening agents. Such suitable carriers in-clude liquids such as water, ethanol, sorbitol, glycerol, citric acid, corn oil, peanut oil, soybean oil, sesame oil, propylene glycol, corn syrup, maple .

syrup, and liquid paraffin; and solids such as lactose, cellulose, starch, dextrin and other modified starches, calcium phosphate and calcium sulfate.
Obviously incompatible for use wi~h the sweetening agents of Formula I would be toxic carriers such as methanol and dimethyl sulfoxide.
The compounds are added to the edible composition by mixing methods known in the art. They may be used alone or as the primary or secondary sweetener in the final composition; with a natural sweetener such as sucrose, or another synthetic sweetener such as saccharin or cyclamate also being added. Combinations of two or more of the present materials may be used, if desired.
Examples of specific edible materials which can be sweetened by the addition of a material of Formula I or II or by a novel combination of the material of Formula I or II with a known sweetening agent include: fruits, vegetables, and juices; meat products such as bacon and sausage; egg products, fruit concentrates; gelatins and gelatin-like products such as jelly and pre-serves; milk products such as ice cream,sour cream and sherbet; icings;
syrups; grain products such as bread, cereals, pasta and cake mixes; fish;
cheese products; nut products; beverages such as coffee, tea, noncarbonated and carbonated soft drinks, beers, wines and liquors; and confections such as candy and chewing gums.
Additional illustrations of the type of commercial products in which the sweetening agents or combinations thereof with known sweetening agents can be used are granulated mixes which upon reconstitution with water provide non-carbonated drinks; instant pudding mixes; instant coffee and tea; pet foods;
livestock feed; tobacco and consumable toiletries such as mouth washes and toothpastes, as well as proprietary and nonproprietary pharmaceutical prepara-tions.
The amount of dihydrochalcone employed can vary widely, just as the _ g _ ~0950~5 amount of natural sugar sweetene-r employed varies from person to person and food application to food application. As a general rule, the weight of dihy-drochalcone added will be about l/lOO-l/lOOOth the weight of sucrose required to yield the same sweetness. Thus, additions of from about 0.001% up to about 0.50% by weight (basis edible substance) of dihydrochalcone may be usefully employed. The present materials offer the advantage that their substantial water solubility permits such addition to most food systems.
These dihydrochalcones, their preparation and their use are further described in the following Examples. These are to illustrate the invention and are not to be construed as limitations on this invention, which is instead defined by the appended claims.

EXAMPLE I
H ~ OCH3 A. Preparation of ~ ~ OH

K O-S-(CH2)3 0 ~ H

H OH
To a solution of 3.02 g (10.0 mmoles) of hesperetin and 2.44 g (20 20 mmoles) of propane sultone in 40 ml DMF is added 1.38 g (10.0 mmoles) of anhy-drous K2C03. The resulting reaction mixture is stirred at ambient temperature for about 20 hrs. The reaction is then checked by tlc (Eastman Chromagram 13254 Cellulose,* HOAc-H20-i-BuOH 1:1:2) and found to contain mainly one prod-uct (I2 staining and uv visualization) having Rf=0.68 along with a small amount of starting material. The DMF is then removed at reduced pressure and the residue taken up in 25 ml water. This mixture is then extracted with EtOAc (4 x 15 ml) to remove unreacted hesperetin and propane sultone. The aqueous solution is then concentrated to yield the desired flavanone alkyla-*Trade Mark - 10 -.:

~0~07~

tion product as an off-white solid which can be purified by recrystallization from water.
B. Use of the Flavanone. A portion of the product of Part A is dissolved in 100 ml of 5% KOH and transferred to a hydrogenation vessel. Then 1 g of 5% palladium on charcoal is added, the mixture is flushed with argon, and then with hydrogen. Finally, it is pressured to 24 psig with hydrogen and shaken overnight. The mixture is filtered through Celite* and brought to about pH 7-8 with dilute hydrochloric acid.
The resultant solution is concentrated to a volume of ca. 150 ml and allowed to stand overnight, whereupon 1.46 g of white clusters separates.
Concentrates of the mother liquor yield an additional 1.17 g of material for a total yield of 2.63 g (55%). Tlc analysis (as above~ of this product indi-cates only one component having a Rf=0.67 and which has spectra and elemental analyses consistent with the product OH

2 C 2 CH2 0 ~ -~-CH2-CH2 ~ ~ ~ o CH3 OH OH

An additional portion of the product made in accordance with Part A
is dissolved in water at a 400 ppm concentration. It is tasted by a group of volunteers who report that it has sweetness equivalent to that of a 85,000 ppm sucrose solution and that in flavor character it is very sugar-like. This would indicate a sweetening power of 200-300 times sucrose. The dihydrochal-cone of Part B is dissolved in water and rigorously evaluated. It is found to be over 450 times as sweet as sucrose with a very good taste.

*Trade Mark ~0~5~

EXAMPLE II
H ~ OCH3 A. Preparation of H ~ ~ OH

O ~ H
>~ ~
Na o-S-(CH2) - ~ ~ ~

~ollowing ~he general teachings of Douglass et al, J. Org. Chem. 15, 795-9 (1950), purified trithiane, ~ ~ 28 grams, and methylene chloride reaction solvent are placed in a vessel and chilled to 0C. Chlorine gas (16 grams) is slowly passed into the vessel with stirring while maintaining the 0C temperature. After three hours, the vessel is permitted to warm to room temperature and unreacted chlorine is removed.
The reaction mixture is warmed to about 50C and vacuum is applied, causing chloromethylsulfenyl chloride (ClCH2SCl) to distill overhead.
Chloromethylsulfenyl chloride ~one equivalent) is dissolved in ben-zene and two equivalents of pyrrolidine is gradually added with stirring. The mixture is stirred at room temperature for one hour. Benzene is stripped and a product ~

Cl-CH2-S-N ~ , (A), is isolated by distillation.
A solution of 3.0 g of hesperetin (Sigma Chemical Co.) in 20 ml of dimethylformamide is prepared. 0.7 Grams of anhydrous potassium bicarbonate is added followed by 4.6 g of (A). The mixture is stirred overnight, at which time excess peracetic acid is added in acetic acid solvent and stirred for 12 hours to form 0~

OH

Water is then added and the mixture is stirred at room temperature for an hour to oxidatively hydrolyze and convert the sulfonamide to the flavanone sulfon-ate, IO 5O3-CH2O ~ 3 OH
Sodium bisulfite is added to consume unreacted peracetic acid. Following evaporation of volatile materialsJ the flavanone sulfonate as the sodium salt is obtained pure by crystallization from water.
B. Use of the Flavanone. In a first use, an aqueous solution of the flavanone (400 ppm) is prepared and tasted and found to be sweet. The flavanone is then added (400 ppm) to a soft drink baseJ to a chewîng gum and a toothpaste. It sweetens these materials.
In a second use, the sulfonate (1.5 grams) is dissolved in 30 ml of 5% aqueous KOH and placed in a 250 ml reaction flask with 250 mg of 5% palla-dium on charcoal. The reaction flask is flushed with hydrogen and the mixture is stirred at room temperature and about atmospheric pressure for about 35 hours. Thin layer chromatography analysis of the mixture before and after reaction indicates that there has been essentially quantitative reduction and opening of the flavanone ring to yield the dihydrochalcone ~:)95~75 H OH H H

-O-S~CH2-0 ~ ~-CH2 CH2 ~ ~ 0-CH3 H H H OH

as the potassium salt.
This material is isolated following neutralization to pH 7-8 with HCl by concentration of the resultant solution in vacuo. After purification by recrystallization, analysis by NMR indicates that the product is the dihy-drochalcone.
EXAMPLE III

A. Preparation of H ~ OCH3 H ~ OH

H O ~ H

K O-S-(CH2)2 0 H OH

72 Milligrams of 50% sodium hydride is washed with hexane. Seven milliliters of anhydrous dimethylsulfoxide is added under an argon cap. Next, 302 mg of hesperetin is slowly added in about one ml of dimethylsulfoxide.
The mixture is reacted at room temperature and then at 50C for about an hour.
Then Br-CH2-CH2-S03Na (253 mg) in dimethylsulfoxide is added and the mixture is stirred overnight under argon at room temperature. Solvent is then stripped off and the product is extracted with ethylacetate. The desired flavanone is crystallized from water to purify.

- - . ' ' ~0~5~5 B. Use of the Flavanone. The material of Part A is dissolved in a cola beverage base, dispensed in a gelatin dessert mix and added to fruit pre-serves. In each application it increases the sweetness of the edible material.
Additional material of Part A is dissolved in 10 ml of 5% aqueous potassium hydroxide, 100 mg of palladium on charcoal and hydrogen (atmospheric pressure) are added and stirred overnight. The reaction product is filtered through Celite*, brought to pH 7-8 with HCl and washed with ethyl-acetate. Water is stripped under vacuum to yield the dihydrochalcone.

H OH H H
O-~-CH2-CH2-O- ~ 2 2 ~ O-CH3 H OH H H
as the potassium salt.
Aqueous solutions of the flavanone and dihydrochalcone potassium salts prepared in Example I are prepared. A saturated solution of calcium chloride is added. The solutions are evaporated until crystals form. These are the calcium salts of the flavanone and dihydrochalcone prepared in Exam-ple I.
EXAMPLE VI
-This example deals with the preparation of the free acids of the flavanones and dihydrochalcones (i.e., when M equals hydrogen).
Solutions of the potassium salt of the two products of Example I
are prepared and placed on a strongly acidic cation exchange resin column such as Rohm and Haas Amberlite IR-120* strongly acidic sulfonated polystyrene.
Aqueous hydrochloric acid is passed over the column and the eluents are col-lected. The eluents are freeze-dried to remove all water and residual hydro-chloric acid and to yield the desired free acids as solid products.
*Trade Mark s EXAMPLE VII
This example sets forth the preparation of 4'-ethoxy and propoxy equivalents of the flavanone of Example I. These materials are formed by con-densing the appropriate benzaldehydes and acetophenones to chalcones and then cyclyzing under acidic conditions to flavanones.
A. Preparation of the acetophenone. To a solution of 1.68 g of phloroacetophenone and 12.7 g of benzyl chloride in 20 ml of DMF is added 5.53 g of anhydrous K2CO3. The mixture is stirred for 16 hours at 65 under argon.
The mixture is diluted with 100 ml of 5% NaCl and extracted with ethyl acetate (2 x 50 ml). The extracts are washed with 5% NaCl and 2% NaO}l, dried over MgSO4 and concentrated to a red oil which is purified on a dry 250 g silica gel columning CC14 as eluent. This yields 2,4,6-tribenzyloxyacetophenone as a yellow oil.
B. Preparation of aldehydes. To a solution of 14.2 g of 3,4-dihy-droxybenzaldehyde, 10.9 g of ethyl bromide, and 14.98 g sodium iodide in 150 ml DMF is added 13.82 g of anhydrous K2CO3. After 16 hours at R.T., tlc and VPC analyses indicate substantial completion of reaction.
The reaction mixture is then diluted with 500 ml 5% NaC1 solution and extracted with ether (2 x 250 ml). The combined ether extracts are washed with 5% NaCl solution and then with 5% NaOH solution. The combined base ex-tracts are acidified with concentrated HCl while cooling in an ice bath.
After standing overnight at 0, a brown precipitate is filtered and washed with water. Recrystallization from EtOH-H20 yields 3-hydroxy-4-ethoxy-benzal-dehyde as off-white needles.
To a solution of 1.66 g of 3-hydroxy-4-ethoxy-benzaldehyde and 2.53 g of benzyl chloride in 20 ml DMF is added 2.76 g (20 mmoles) of anhydrous K2CO3. After stirring under argon for 21 hours, the reaction is checked by tlc and found to be complete. The reaction mixture is diluted with 60 ml 5%

. .

..;

~5~75 NaCl solution and extracted with EtOAc 50 ml. The combined extracts arewashed with 5% NaCl solution, 1% NaOH solution, dried over MgS04 and concen-trated yielding a yellow oil. After removal of volatile components at re-duced pressure, the residue is recrystallized from aqueous ethanol yielding white needles of 3-benzyloxy-4-ethoxybenzaldehyde.
This aldehyde preparation is essentially repea~ed substituting n-propyl iodide for ethyl iodide in the starting materials. This results in 3-benzyloxy-4-n-propoxy-benzaldehyde as a second aldehyde product.
C. Preparation of chalcones. To a solution of 2.19 g of 2,4,6-tri-10 benzyloxyacetophenone and 1.28 g of 3-benzyloxy-4-ethoxybenzaldehyde in 5.0 ml warm absolute ethanol is added 7.5 ml of 60% KOH. The resùlting reaction mix-ture is stirred at ambient temperature overnight resulting in the formation of a gummy precipitate. The reaction mixture is then dumped into 30 ml of water and extracted with ether (2 x 25 ml), the combined portions of which are dried over MgSO4 and concentrated yielding a yellow solid. Tlc analysis indicates the formation of a sole product and complete consumption of both starting materials. Recrystallization from EtOAc-MeOH yields yellow needles of 2,4,6,

3'-tetrabenzyloxy-4'-ethoxychalcone, i.e., C6H5-CH2-O ~ ~-CH=CH ~ -C2H5 \ 2 C6H5 This reaction is repeated using the propoxy aldehyde in place of the ethoxy aldehyde. The product with results is the corresponding 4'-propoxy-chalcone.

D. Cyclization to flavanones. To a solution of 1.35 g of the eth-oxy chalcone of Part C in 20 ml of acetic acid is added 5.45 g of 47% (w) ~0~50~'S

hydroiodic acid. The mixture is stirred at room temperature for 24 hours andthen dumped into 45 ml of water and extracted with EtOAc (3 x 25 ml). The combined extracts are washed with water ~6 x 100 ml) and concentrated to dry-ness. The resulting flavanone product, ~ 2 5 H ~ OH

Il O ~ ~1 , is recovered and purified by HO ~ ~
\

H OH

recrystallization from ethanol-water.

When this reaction is repeated using the 4'-propoxy chalcone of Part C the corresponding 4'-propoxy flavanone results.
E. Alkylation. The two flavanones of Part D are serially subsit-tuted for hesperetin in the reaction and work-up of Part A of Example I. This results in the formation and recovery of first the 4'-ethoxy equivalent of the product of Example I and second the 4'-n-propoxy equivalent of the product of Example I, i.e., /5' ~
H ~ OH

S ( 2~3 H OH

0~5075 and H \ O-C3H7 2 ~
~ ~ . It will be apparent to K _o-~-~CH2)3 H' OH

those skilled in the art to likewise substitute the two flavanones of Part D
of this example in the preparations of Examples II and III and the reactions of Examples IV, V and VI.
EXAMPLE VIII
Preparation of }I OH H H
,o, ~ R ~
-O-~-CH -O- ~ ~-CH2-CH ~ 2 3 H' H H O}-l and O-~-CH2-O ~ ~-CH2 CH2 ~ O-CH2-CH2-CH3 H OH H OH
These products are prepared by condensing the appropriate benzalde-hydes and acetophones as follows:
A. Preparation of aldehyde reac~ants.
A solution of 2.76 g (20.0 mmoles) of 3,4-dihydroxybenzaldehyde and 2.76 g (20.0 mmoles~ of anhydrous potassium carbonate and 3.45 g (22.0 mmoles) - ~0~507~

of ethyl iodide is prepared in 15 ml of dry DMF and stirred under argon for 24 hours at room temperature. The reaction mixture is poured into 50 ml of water, saturated with sodium chloride and extracted thrice with diethyl ether.
The ether extracts are washed with water, and brine, dried and concentrated to yield the ethoxy aldehyde, ~ CH2CH3 as dark crystals.
OH
CHO
The reaction is repeated using 3.74 g (22.0 mmoles) of n-propyl iodide in place of ethyl iodide to yield the propoxy aldehyde, O-CH2CH2CH3 ~OH
B. Coupling CHO
1.5 Milliliters of 50% aqueous potassium hydroxide is added to a solution of 166 mg (1.0 mmole) of the ethoxy aldehyde of part a of this ~xam-ple and 301 mg (1.0 mmole) of 2,6-dihydroxy-4-(sulfomethoxy) acetophenone.

OH

-O-~-CH2-0-(~fC~ -CH3, OH
in 1.0 ml of absolute ethanol. The resultant mixture is stirred under argon at room temperature for 9 hours and then poured into 20 ml of 9% hydrochloric acid (ice cold) with stirring. A colored substance is extracted with this mixture when it is extracted twice with ether. The ether extracts are dis-carded. The aqueous solution was concentrated where upon off-white crystals were observed to form. This product has an NMR spectrum consistent with the ethoxychalcone structure OH

O-~-CH2-0-~ C-CH=CH ~) -CH2-CH3 OH OH

_ 20 -~L0~5~7~

The process of this section b is repeated using the propoxy aldehyde part a in place of the ethoxy aldehyde. The product which results has an NMR
spectrum consistent with the propoxy-chalcone structure OH

O-~-CH2-0 ~ C-CH=CH ~ O-CHz-CHz-cH3 OH OH
C. Reduction.
A solution of 0.10 mmole of the ethoxychalcone in 1.0 ml of 5% KOH
also containing 50 mg of 5% Pd on charcoal is placed in a flask and purged with hydrogen. The flask is capped and attached to a low pressure hydrogen source. The mixture is stirred for four hours at room temperature, filtered, and extracted with ethylacetate. The extract is dried and evaporated to give a material which crystallizes yielding a solid product consistent with the dihydrochalcone structure OH

K+~~S~CH ~ ~ 2 2 ~ 2 3 OH OH
A portion of this material is dissolved in a solution of CaC12. The solution is evaporated and a precipitate forms. This precipitate is the calcium dihy-drochalcone salt.
The reactions of this part are repeated with the propoxy material of part a and yield the propoxy-substituted dihydrochalcone product. This mate-rial is converted to the Ca II, Mg II, Na I, Fe III, and Zn II salts by the method set forth earlier in this section of this Example.
It would be possible to repeat this Example using methyl iodide, e~c.
to yield the methoxy substituted dihydrochalcone, . ~
-'~ :. ~:, ''- ~

; :
:

~0~50~S

OH

~- -CH -o_ ~ 2 2 ~ O-CH3.

OH OH
However, in view of the ready availability of the natural product, hesperetin, as a route to methoxy dihydrochalcone, this route is generally not preferred.
EXAMPLE IX

Preparation of OH

2 2 ~ 2 2 ~ 2 3 OH OH

and OH

O-~-CH2-CH2-O- ~ 2 2 ~ O-CH~-CH2-CH3 OH OH
The process of Example VIII is repeated twice. The ethoxy and pro-poxy aldehydes of Part A of Example VIII are prepared. They are in turn reacted in accordance with step B of Example VIII but with 2,6-dihydroxy-4-sulfo-ethoxy-acetophenone instead of the methoxy material employed in Example VIII. The products are reduced as in step C of Example VIII to yield the desired products. These materials are converted to a variety of physiolog-ically acceptable metal salts by the process of step C of Example VIII. As before, the methoxy equivalents of the ethoxy and propoxy materials could also _~
be produced by this process, if desired.

~o~;o~s EXAMPLE X
_ Preparation of OH

-O-~-CH -CH -CH -O ~

OH OH
and OH

10 0-~-CHz-CH2-C1~2-o <~ -CH -CH ~ ~ O-CH2-CH2-CH3 OH OH
The process of Example VIII is repeated twice more. The aldehydes of part A of Example VIII are prepared and reacted in accordance with step B
of Example VIII but with 2,6-dihydroxy-4-sulfopropoxy-acetophenone instead of

4-methoxy material employed in Example VIII. The products are reduced as in step C of Example VIII to yield the desired products. These materials are converted to a variety of physiologically acceptable metal salts by the method set forth in Example VIII.
EXAMPLE XI
This example shows an alternate preparation of 1-(2,3',6-trihydroxy-4'-methoxy-dihydrochalcone-4-oxy) ethane-2-sulfonate salts OH

2 2 ~ 2 2 C ~ o CH3 OH OH
A. Preparation of 3',5-Dihydroxy-4'-Methoxy-7-Bromoethoxy-Flavanone.
A solution-suspension of 1.73 g (12.5 mmoles) of anhydrous potas-sium carbonate, 3.02 g (10.0 mmoles) hesperetin and 18.8 g (100 mmoles) dibro-~ 23 ' . .
, .

~o.~

methane in 100 ml DMF is stirred vigorously under argon at 42C for 15 hours.
The reaction mixture is then poured into 600 ml of water and extracted with ethyl acetate (3 x 75 ml), the combined portions of which are washed with water ~3 x 75 ml), brine (1 x 75 ml), then dried over MgS04 and concentrated yielding 8.74 g of an oily yellow solid. Tlc (silica gel F-254, CH2C12-CH30H
95:5) indicates a rough ratio of product (Rf=0.58) to starting material (Rf=
0.10) of 2:1 as well as at least five other unknown minor impurities. The crude product is then heated to boiling with 50 ml ether. After cooling, the mixture is filtered yielding 1.01 g of product (homogeneous on tlc) as an off-white solid. The filtrate is concentrated and recycled. After three cycles, 2Ø g (50%) of the pure bromoethyl derivative is obtained. Recrystallization from hexane-chloroform gives white clusters having a mp of ]53-4C and in-fr~ied and NMR spectra consistent with the desired compound.
B. Preparation of 2,3'-6-Trihydroxy-4-Bromoethoxy-4'-Methoxy-Chalcone.
Ten ml of 5% KOH is added to 400 mg (1,00 mmole) of 3',5-dihydroxy-4'-methoxy-7-bromoethoxy-flavanone giving a bright yellow solution which is stirred under argon at ambient temperature for 2 hours. The reaction mixture is then poured into 100 ml of water, acidified with 10% HCl, and extracted immediately with ethyl acetate (2 x 25 ml). The combined extracts are washed 20 with dilute NaHC03 (1 x 25 ml), dried over MgS04 and concentrated yielding 0.51 g of a partially crystalline orange oil Tlc (silica gel F-254*, CH2C12-CH30H 95:5), indicates the reaction to have proceeded nearly quantitatively showing only the product (Rf=0.28) and a barely observable spot for starting material (~f=0~73)~ Preparative tlc on silica gel PF-254, eluting with CH2C12-CH30H 95:5, yielded 302 mg (75%) of the chalcone as a yellow solid. Recrystal-lization from hexane-ethyl acetate gives orange clusters having mp 158-162C
and spectra consistent with the desired compound.
C. Preparation of 2,3',6-Trihydroxy-4-Bromoethoxy-4'-Methoxy-Dihydrochalcone.
* Trade Mark ~ 24 ~

~OS3S075 Sixty mg of 10% Pd-C is added to a degassed solution of 88 mg (0.22 mmole) of 2,3',6-trihydroxy-4-bromoethoxy-4'-methoxy-chalcone in 30 ml of ethyl acetate. The resultant mixture is shaken on a Parr hydrogenation appa-ratus at an initial H2 pressure of 31 lb. After one hour, the reaction mix-ture is filtered through Celite* and concentrated yielding 92 mg ~100%) of an off-white oil. Tlc (silica gel F-254, CH2C12-CH30H 95:5) indicates the reduc-tion to be quantitative showing only one spot having Rf=0.28. The crude pro-duct solidifies into a hard foam under vacuum, but resists several attempted recrystallizations. Infrared and NMR spectra are consistent with the sought product.
D. Preparation of Potassium 1(2,3'-,6-Trihydroxy-4'-methoxy-dihydrochalcone-4-oxy) Ethane-2-Sulfonate.
To a solution of 0.90 g (2.24 mmoles) 2,3',6-trihydroxy-4-bromoeth-oxy-4'-methoxy-dihydrochalcone in 10 ml of methanol is added a solution of 396 mg (2.50 mmoles) K2S03 in 10 ml water. On brief heating, a homogeneous reac-tion mixture is obtained that is refluxed overnight. The hot solution is then filtered through Celite and concentrated giving 1.54 g of a slightly wet white solid. Tlc on silica gel F-254* (saturated with water), eluting with n-buta-nol (saturated with water) shows one main spot (Rf=0.41) in addition to six minor impurities. Recrystallization of the crude product from either water or methanol-water mixtures ls difficult, although a 28 mg sample of pure sulfon-ate is obtained in this way. This material had mp of 178-185C without decom-position and a sweetness over 700 times that of sucrose. A portion of this material is contacted with aqueous Ca II to yield the equivalent Ca II salt which is also isolated and found to be about 550 times as sweet as sucrose.

* Trade Mark _ 25 -

Claims (11)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A dihydrochalcone compound represented by the structural formula , wherein R is a lower alkyl of from one to three carbon atoms inclusive, n is an integer of from one to three inclusive and M is a physiologically accept-able metal cation, or hydrogen.

2. The compound of Claim 1, wherein n has a value of 1 and R is methyl or n-propyl.

3. The compound of Claim 2 wherein M is calcium or potassium cation.

4. The compound of Claim 1, wherein n has a value of 2 and R is methyl or n-propyl.

5. The compound of Claim 4, wherein M is calcium or potassium cation.

6. The compound of Claim 1, wherein n has a value of 3 and R is methyl or n-propyl.

7. The compound of Claim 6, wherein M is calcium or potassium cation.

8. A process for preparing a dihydrochalcone of the formula wherein: R represents a lower alkyl group of 1 to 3 carbon atoms inclusive;
M represents hydrogen or a physiologically acceptable cation; and n represents an integer of 1 to 3 inclusive, which process comprises:
(a) opening with a base and hydrogenating a flavanone of the formula wherein R, M and n are as defined above, or (b) condensing a 2,6-dihydroxy-4-sulfoalkyloxyacetophenone of the formula with a 3-hydroxy-4-alkoxybenzaldehyde of the formula wherein R, M and n are ax defined above, in the presence of a base to provide a chalcone, and thereafter hydrogenating the thus-obtained chalcone.

9. Process according to claim 8(a) wherein the flavanone is prepared by alkylating a hesperetin analog of the formula wherein R represents an alkyl group of 1 to 3 carbon atoms inclusive, with a one to three carbon alkylsulfonate group in the presence of a weak base.

10. Process according to Claim 9 wherein R is CH3 and the alkylsulfonate group is propane sulfone.

11. A sweetened consumable material comprising an edible material and, as a sweetening agent, a dihydrochalcone compound of Claim 1 in the amount which will afford the degree of sweetness desired.