TECHNICAL FIELD The present invention relates to processes for preparing sunscreen complexes, and more particularly to sunscreen metal complexes, having enhanced UVA absorption. These complexes comprise a dibenzoylmethane UVA-absorbing sunscreen complexed to a cationic species, preferably a metal cation. These complexes are useful for protecting the skin from the harmful effects of ultraviolet radiation. This invention also relates to methods for preparing compositions containing these complexes. BACKGROUND OF THE INVENTION

The damaging effects of sunlight on skin are well documented. The major short term hazard of prolonged exposure to sunlight is erythema (i.e. sunburn). The 290 to 320 nanometer wavelength ultraviolet radiation range, designated as the "UVB" wavelength range, tends to be the primary cause of erythema. The 320 to 400 nanometer wavelength ultraviolet radiation range, designated as the "UVA" wavelength range, also produces erythema.

In addition to the short term hazard of erythema, there are also long term hazards associated with UV radiation exposure. One of these long term hazards is malignant changes in the skin surface. Numerous epidemiologic studies demonstrate a strong relationship between sunlight exposure and human skin cancer.

Another long term hazard of ultraviolet radiation is premature aging of the skin. This condition is characterized by wrinkling and yellowing of the skin, along with other physical changes such as cracking, telangiectasis (spider vessels), solar keratoses (growths), ecchymoses (subcutaneous hemorrhagic lesions), and loss of elasticity (sagging). The adverse effects associated with exposure to UVA and UVB wavelength radiation are more fully discussed in DeSimone, "Sunscreen and Suntan Products", Handbook of Nonprescription Drugs. 7th Ed., Chapter 26, pp. 499-511 (American Pharmaceutical Association, Washington, D.C.; 1982); Grove and

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Forbes, "A Method for Evaluating the Photoprotection Action of Sunscreen Agents Against UV-A Radiation", International Journal of Cosmetic Science. 4, pp. 15-24 (1982); and U.S. Patent 4,387,089, DePolo, issued June 7, 1983; the disclosures of all of which are incorporated herein by reference.

Both sunscreen agents and physical sunblocks are commercially available to protect the skin from UV radiation. Physical sunblocks scatter, reflect, and absorb ultrabiolet radiation. See, Sayre, R.M. et al., "Physical Sunscreens", J. Soc. Cos et. Chem.. vol. 41, no. 2, pp. 103-109 (1990). Examples of physical sunblocks include titanium dioxide and zinc oxide. However, compositions containing a high level of these agents are opaque, generally unattractive in color, and are viewed as unacceptable for usage on more than just the nose or tops of the ears. Furthermore, these agents are very susceptible to rub-off or wear-off resulting in little or no protection.

In contrast, sunscreen agents exert their effects through chemical means, i.e., they absorb ultraviolet radiation so that it cannot penetrate the skin. Sunscreens present the user with several problems. For example, they must be on the surface of the skin at the time of exposure to be effective. Sunscreens are preventative so one must anticipate being in the sun. To be most effective, sunscreens must be on the skin as a continuous uniform film. Delivering such a film to the surface of the skin is very difficult. Most commercially-avaible sunscreen agents are primarily UVB absorbers. The number of UVA absorbers is more limited with benzophenones and dibenzoylmethanes being the most well-known. U.S. Patent No. 4,489,057, to Welters et al., issued December 18, 1984, and U.S. Patent No. 4,387,089, to DePolo, issued June 7, 1983, both of which are incorporated herein by reference, disclose dibenzoylmethane sunscreen agents.

It has been found in the present invention that the UVA absorption of the dibenzoylmethane chromophore is significantly enhanced when it is complexed to certain cationic species such as metal cations. Thus, it is possible to prepare sunscreen agents having enhanced UVA absorption for protecting the skin from the harmful effects of UV radiation.

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It is therefore an object of the present invention to provide processes for the preparation of sunscreen complexes which provide enhanced UVA absorption.

It is another object of the present invention to provide processes for the preparation of sunscreen metal complexes which provide enhanced UVA absorption.

It is a further object of the present invention to provide processes for the preparation of topical sunscreen compositions containing sunscreen metal complexes. These and other objects will become readily apparent from the detailed description which follows.

SUMMARY OF THE INVENTION The present invention relates to a process for preparing a sunscreen complex which comprises combining a sunscreen compound of general formula

with a salt in a suitable solvent, wherein A is a substituent selected from H, -OR or -NR where each R is independently H, straight or branched chain alkyl having from about 1 to about 20 carbon atoms, (CH2CH2θ) _q -H, or (CH2CH(CH3)0) _q -H, wherein q is an integer from 1 to about 8; B is a substituent selected from H, straight or branched chain alkyl having from about 1 to about 20 carbon atoms, (CH2CH2θ) _q -H, or (CH2CH(CH3)0) _q -H, wherein q is an integer from 1 to about 8; and said salt is selected from salts of aluminum, zinc, calcium, magnesium, copper, iron, barium, strontium,, zirconium, titanium, tin, berylium, gallium, indium, lanthanum, manganese, antimony, bismuth, cerium, thorium, niobium, tantalum, antimony, molybdenum, tungsten, lithium, sodium, potassium, ammonium, substituted ammonium, and mixtures thereof. The present invention further relates to methods for preparing compositions containing these complexes, and to methods for

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providing enhanced protection to the skin of humans or lower animals from the effects of ultraviolet radiation.

All percentages and ratios used herein are by weight and all measurements are at 25°C, unless otherwise indicated. DETAILED DESCRIPTION OF THE INVENTION

Sunscreen Complexes

The sunscreen metal complexes useful in the present invention are those having the general structure:

(S)n (H)n (Dp- (S) _m represents a dibenzoylmethane sunscreen moiety, where m designates the number of moieties present in the complex.

(M) _n represents a cationic species such as a metal, or alternatively ammonium or substituted ammonium, where n designates the number of species present in the complex. (L)p represents a ligand, which is optionally present in the complex, where p designates the number of ligands present in the complex.

The sunscreen metal complexes of the present invention preferably absorb light in the visible wavelength range (i.e. above about 400 nm) only weakly or not at all. The complexes are therefore either only lightly colored (e.g., light yellow or cream colored) or are essentially white. This is desirable for cosmetic reasons. Thus, the sunscreen metal complexes preferably do not have a £ of greater than about 500 for any wavelength above about 400 nm, and most preferably the 6 is essentially zero for any wavelength above about 400 nm. (Sl _m Sunscreen Moietv

The sunscreen moieties which comprise the sunscreen complexes of the present invention are those containing the dibenzoylmethane chromophore. This chromophore is characterized as being effective for strongly absorbing radiation in the UVA range. These dibenzoyl methane sunscreen moieties which comprise the complexes of the instant invention are fully disclosed in U.S. Patent Nos. 4,489,057 and 4,387,089, which have already been incorporated by reference, supra.

In the sunscreen complexes of the present invention, the number of sunscreen moieties present is designated by m, wherein m is an

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integer selected from 1 through 8, more preferably m is an integer selected from 1 through 4, even more preferably is an integer selected from 1 through 3, and most preferably is 2. Furthermore, it is realized that the complexes of the instant invention can exist as a mixture of different species in which the m value varies. Thus, it is possible to obtain a complex in which the average m value is a noninteger average of the m values for the species present.

Examples of the UVA-absorbing dibenzoylmethane sunscreen moieties useful in the sunscreen compounds of the present invention include those of the following general structure:

In the preceding structure, A is a substituent of variable position on the aromatic ring selected from H, -OR or -NR2 where each R is independently H, straight or branched chain alkyl having from about 1 to about 20 carbon atoms, (CH CH2θ) _q -H, or (CH2CH(CH3)0) _q -H, wherein q is an integer from 1 to about 8; and B is a substituent of variable position on the aromatic ring selected from H, straight or branched chain alkyl having from about 1 to about 20 carbon atoms, (CH2CH2θ) _q -H, or (CH2CH(CH3)0) _q -H, wherein q is an integer from 1 to about 8. In the instant invention A is preferably para -OCH3 and B is para t-butyl, i.e. 4,4\'-methoxy-t-butyldibenzoylmethane (CTFA adopted name: butyl dibenzoylmethane, which is commercially available under the trademark Parsol ^R 1789 from Givaudan), or alternatively A is H and B is para isopropyl, i.e. 4-isopropyl- dibenzoylmethane (CTFA adopted name: isopropyl dibenzoylmethane, which is commercially abailable under the trademark Eusolex ^R 8020 from Merck) .

In the sunscreen moiety, even though the dibenzoylmethane chromophore is represented as a 1,3-diketone it should be understood that this representation in no way excludes other tautomeric forms of the functional group such as the enol form. Thus whenever the 1,3-diketone form is designated, it is understood that all

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appropriate enol tautomers are also contemplated and included herein. These tautomeric enol forms of the dibenzoylmethane chromophore can be represented by the following tautomeric structures.

Furthermore, it is also realized that the dibenzoylmethane chromophore can lose a hydrogen atom to form the corresponding anionic species. This phenonenon is more likely at higher pH values (i.e. alkaline pH values) and when the dibenzoylmethane chromophore is complexed to a cationic species such as a metal. Thus, whenever the 1,3-diketone form is designated, it is understood that all appropriate anionic forms are also contemplated and included herein. These anionic forms of the dibenzoylmethane chromophore can be represented by the following resonance structures.

The term "molar absorptivity value", as used herein, is a quantitative measure of the ability of a molecule to absorb ultra¬ violet light at a specified wavelength. The molar absorptivity alue is expressed at a particular wavelength of light as the molar absorption coefficient (represented herein by " e " which is expressed in units of liter/mole cm), which is calculated by the equation:

A =_= lc wherein "1 " is the path length (in centimeters) of the absorbing media through which the l ight passes ; "c" is the concentration of

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the chromophore molecule (in moles per liter); and "A" is the "absorbance". The absorbance is calculated from the observed difference in the intensity of the particular wavelength of light before and after passing through the chromophore-molecule-containing absorbing media. Thus, the absorbance is calculated by the equation:

A = log ₁₀ _Jl I wherein "I ₀ " is the intensity of a particular wavelength of incident radiation on an absorbing path; and "I" is the intensity of the same particular wavelength of transmitted radiation which has passed through the absorbing path.

The calculation of the molar absorptivity value for a par¬ ticular wavelength of light is well-known in the art, and is taught in more detail in Atlas of Spectral Data and Physical Constants for Organic Compounds. 2nd Ed., Vol. I, pp. 399-408 (Grasselli and Ritchey, Editors; CRC Press, Inc., Cleveland, Ohio, 1975), the disclosures of which are incorporated herein by reference. Instru¬ ments useful for making the intensity measurements for the calcu- lation of the molar absorptivity value are also well-known in the art (eg., Varion DMS-100, Beckman DU-7, and Philips PU8800). Molar absorptivity values for representative compounds of the present invention are provided in the Examples hereinafter.

The term "absorption maximum", as used herein, means a wavelength of radiation at which the chro ophore-containing molecule has the greatest molar absorptivity value relative to wavelengths immediately above and below the absorption maximum wavelength. Thus, in the typical spectrum of UV-radiation absorption, an absorption maximum is easily identified as a peak in the graph of the spectrum generated by the instrument measuring the UV absorption. Absorption maximum (designated herein as λ max) are provided for representative sunscreen compounds of the present invention in the Examples hereinafter.

IMiα The sunscreen complexes of the present invention comprise a cationic species, preferably a metal, or alternatively ammonium or substituted ammonium, represented by the general structure (M) _n .

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Examples of metal cations useful in the complexes of the present invention include alkali metal (e.g., sodium and potassium), alkaline earth metal (e.g., calcium and magnesium), and transition and heavy metals (e.g., aluminum and strontium). Preferred for use in the complexes of the instant invention are the metals selected from the group consisting of aluminum, zinc, calcium, magnesium, copper, iron, barium, strontium, zirconium, titanium, tin, beryllium, gallium, indium, lanthanum, manganese, antimony, bismuth, cerium, thorium, niobium, tantalum, antimony, molybdenum, tungsten, lithium, sodium, potassium and mixtures thereof. These metal cations are useful in any of their possible valence states and in combinations of these states (i.e. where for example some of the metal cations are in one of the cation\'s allowable valence states, and some of the metal cations are in another of the metal cation\'s allowable valence states, etc.).

Alternatively, the sunscreen complexes of the instant invention can also comprise complexes with other cationic species such as ammonium, substituted ammonium (e.g., mono-, di-, tri- and tetra- alkyl and alkoxy substituted), and cations of diamines (e.g., tetra- alkyl and alkoxy substituted ethylene diamines).

In the sunscreen complexes of the present invention preferred cation species include metals selected from the group consisting of aluminum, titanium, copper, iron, and zinc.

In the sunscreen complexes of the present invention, aluminum cations having a valence of 3+ are most preferred.

In the sunscreen complexes of the present invention, the number of M species present in the complex is designated by n, wherein n is an integer selected from 1 through 4, more preferably n is an integer selected from 1 through 3, even more preferably n is an integer selected from 1 and 2, and most preferably n is 1. Furthermore, it is realized that the complexes of the instant invention can exist as a mixture of different species having different n values. Thus, it is possible to obtain a complex in which the average n value is a noninteger weighted average of the n values for the species present.

In the compositions of the present invention the M species can be derived from any suitable sources. For example, when the M

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species of the complexes is a metal cation, the cation can be derived from a wide variety of salts. Examples of salts include metal oxides, hydroxides, fluorides, chlorides, bromides, iodides, carbonates, bicarbonates, phosphates, hydrogen phosphates, dihydrogen phosphates, alkoxides (e.g., isopropxide) sulfates, hydrogensulfates, nitrates, sulfites, nitrites, borates, chlorates, bro ates, perchlorates, perbromates, diphosphates, polyphosphates, thiocyanates, carboxylates (preferably, acetates and stearates), and mixtures thereof. Alternatively, when the M species is ammonium or substituted ammonium, the ammonium or substituted ammonium species can be derived from a wide variety of ammonium and substituted ammonium sources such as salts (e.g., chlorides, bromides, hydroxides, and the like).

For the compositions of the instant invention preferred sources of the cationic species include aluminum monoacetate, aluminum diacetate, aluminum stearate, and mixtures thereof. Expecially preferred is aluminum monoacetate. (Dp Ligand

The sunscreen complexes of the present invention optionally comprise an organic or inorganic ligand represented by the general structure (L) _p . Both neutral and anionic ligands are useful in the complexes of the present invention. Useful organic ligands include, but are not limited to, those selected from the group consisting of carboxylic acids, dicarboxylic acids, and polycarboxylic acids and their anions; amines, diamines, and polya ines; alcohols, diols, and polyols and their anions; thiols, dithiols, and polythiols and their anions; a ino acids and their anions; any other pharmaceutically-acceptable organic ligands, and mixtures thereof. Useful inorganic ligands include, but are not limited to, water and hydroxide anion, halide (e.g., fluoride, chloride, bromide, and iodide), carbonate, bicarbonate, phosphate, hydrogen phosphate, dihydrogen phosphate, sulfate, hydrogen sulfate, nitrate, sulfite, nitrite, borate, chlorate, bromate, perchlorate, perbromate, diphosphate, polyphsophate, thiocyanate, any other pharmaceutically-acceptable inorganic ligands, and mixtures thereof. By the term "pharmaceutically-acceptable" organic and inorganic

SUBSTITUTE SHEET

ligands as used herein is meant those organic and inorganic ligands which are acceptable from a toxicity viewpoint.

For the sunscreen complexes of the present invention, ligands selected from water, hydroxide anion, and carboxylic acids having from about 2 to about 22 carbon atoms and their anions are preferred. Other preferred ligands include ethoxide and isopropoxide. Especially preferred among the carboxylic acids and their anions are acetic acid and the acetate anion, octanoic acid and the octanoate anion, and stearic acid and the stearate anion. In the sunscreen complexes of the present invention, the number of ligands present in the complex is designated by p, wherein p is an integer selected from 0 through 4, more preferably p is an integer selected from 0 through 3, even more preferably p is an integer selected from 0 through 2, even more preferably p is an integer selected from 0 and 1, and most preferably p is 0. Furthermore, it is realized that the complexes of the instant invention can exist as a mixture of different species having different p values. Thus, it is possible to obtain a complex in which the average p value is a noninteger weighted average of the p values of the species present.

Preferred examples of sunscreen metal complexes of the present invention include, for example:

Aluminum (III) Complex of 4,4\'-methoxy-t-butyldibenzoylmethane; Aluminum (III) Complex of 4-isopropyldibenzoylmethane; Iron (III) Complex of 4,4\'-methoxy-t-butyldibenzoylmethane; Iron (III) Complex of 4-isopropyldi enzoyl ethane; Copper (II) Complex of 4,4\'-methoxy-t-butyldibenzoylmethane; Copper (II) Complex of 4-isopropyldibenzoyl ethane; Titanium (IV) Complex of 4,4\'-methoxy-t-butyldibenzoylmethane; Titanium (IV) Complex of 4-isopropyldibenzoylmethane; and mixtures thereof. Preparation of Sunscreen Complexes

The sunscreen metal complexes of the present invention can be prepared as described in the Examples below. In further embodiments, these complexes can then be directly formulated into a desired carrier. Alternatively, these sunscreen complexes can be isolated before being formulated into the desired carrier. In yet

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another alternative, these sunscreen complexes can be prepared directly in the desired carrier.

In general, the sunscreen metal complex is prepared by combining a sunscreen compound and a metal salt in a suitable solvent selected from the group consisting of water, acetone, ethyl acetate, methyl t-butyl ether, C1-C5 alcohols, diols, triols, C12-15 alcohols benzoate, dimethyl isosorbide, chlorinated solvents (e.g., methylene chloride), isodecyl neopentanoate, diisopropyl adipate, and mixtures thereof. Preferred solvents include water, acetone, ethanol, and mixtures thereof. Preferred metal salts include those selected from the group consisting of salts of aluminum, zinc, calcium, magnesium, copper, iron, barium, strontium, zirconium, titanium, tin, beryllium, gallium, indium, lanthanum, manganese, antimony, bismuth, cerium, thorium, niobium, tantalum, antimony, molybdenum, tungsten, lithium, sodium, potassium, and mixtures thereof. More preferred are salts of aluminum, titanium, copper, iron, zinc, and mixtures thereof. Especially preferred are salts of aluminum, with those selected from the group consisting of aluminum acetate, aluminum diacetate, aluminum stearate, aluminum distearate, aluminum octanoate, aluminum ethoxide, aluminum isopropoxide, and mixtures thereof, being more preferred, and aluminum monoacetate being most preferred. Alternatively ammonium and substituted ammonium chlorides, bromides, and hydroxides can be employed.

Additionally, at least one equivalent of a base can be added in order to facilitate the dissolution of the sunscreen compound. Preferably, the sunscreen compound and the base are prereacted in the solvent system before the metal salt is added. Preferred bases include sodium hydroxide, potassium hydroxide, ammonium hydroxide, sodium bicarbonate, sodium carbonate, and mixtures thereof. Additionally, the solvent system can be heated to its boiling point if required. Where the sunscreen metal complex is isolated and purified, this is preferably accomplished by filtration, washing, drying, and evaporation of the filtrate. Additionally, the complex can be further purified by recrystallization from a suitable solvent. The Examples given below provide representative preparations of the sunscreen metal complexes and compositions containing them.

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Co positions Containing Sunscreen Metal Complexes

One or more of the sunscreen complexes of the present invention can be incorporated into a variety of carriers, including pharmaceutical and cosmetic carriers, paints, coatings, polymeric maxtrices, fiber matrices, and the like. Preferably, the complexes are incorporated into pharmaceutical and cosmetic carriers.

The sunscreen metal complexes of the present invention typically comprise from about 0.1% to about 30.0% by weight of the sunscreen compositions of the present invention, preferably from about 1% to about 20%, and most preferably from about 5% to about 15%. The compositions of the instant invention can comprise the following components. Pharmaceutical1v-Acceotable Carriers

The compositions of the instant invention can comprise a safe and effective amount of a topical pharmaceutically-acceptable carrier or diluent which can be of a variety of different forms. By "safe and effective" is meant an amount sufficient to act as a suitable vehicle for the sunscreen metal complexes and any other components, but not so much as to cause any side effects or skin reactions. "Pharmaceutically-acceptable" means that the carrier is suitable for topical application to the skin without causing any untoward safety or toxicity concerns. In other words, these carriers are suitable for use on humans and lower animals. The topical carrier can be in the form of an emulsion including, but not limited to, oil-in-water, water-in-oil, water-in-oil-in-water, and oil-in-water-in-silicone emulsions. These emulsions can cover a broad range of consistencies including thin lotions (which can also be suitable for spray or aerosol delivery), creamy lotions, light creams, heavy creams, and the like. Other suitable opical carriers include anhydrous liquid solvents such as oils and alcohols; aqueous-based single phase liquid solvents (e.g. hydro-alcoholic solvent systems); anhydrous solids and semisolids (such as gels and sticks); and aqueous based gel and mousse systems. Examples of topical carrier systems useful in the present invention are described in the following four references all of which are incorporated herein by reference in their entirety: "Sun Products Formulary" Cosmetics & Toiletries, vol. 105, pp. 122-139 (December

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1990); "Sun Products Formulary", Cosmetics & Toiletries- vol. 102, pp. 117-136 (March 1987); U.S. Patent No. 4,960,764 to Figueroa et al., issued October 2, 1990; and U.S. Patent No. 4,254,105 to Fukuda et al., issued March 3, 1981. The pharmaceutically-acceptable topical carriers, in total, typically comprise from about 0.1% to about 99.8% by weight of the sunscreen compositions of the present invention, preferably from about 80% to about 99%, and most preferably from about 85% to about 95%. A preferred topical carrier of the compositions of the instant invention is an oil-in-water type emulsion. The pH of these oil-in- water emulsion compositions herein is preferably in the range of from about 3.5 to about 9. Additionally, the mean particle size of the dispersed oil phase materials can be in the range of from about 1 to about 10 microns with greater than about 75% of the particles being less than about 12 microns. Additional Sunscreens

A wide variety of one or more additional sunscreening agents are suitable for use in the present invention. Segarin, et al . , at Chapter VIII, pages 189 et seq., of Cosmetics Science and Technology, disclose numerous suitable agents. Specific suitable sunscreening agents include, but are not limited to, for example: Ethylhexyl-p-methoxycinnamate (available as Parsol MCX from Givaudan Corporation), p-Aminobenzoic acid, its salts and its derivatives (ethyl, isobutyl, glyceryl esters; p-dimethylamino- benzoic acid; 2-ethylhexyl N,N-dimethylaminobenzoate; p-Methoxy- cinnamic Acid Diethanolamine Salt (available as Bernel Hydro from Bernel Chemical Co.); Anthranilates (i.e., o-aminobenzoates; methyl, octyl, amyl, menthyl, phenyl, benzyl, phenylethyl, linalyl, terpinyl, and cyclo- hexenyl esters); Salicylates (octyl, amyl, phenyl, benzyl, menthyl, glyceryl, and dipropyleneglycol esters); Cinnamic acid derivatives (menthyl and benzyl esters, -phenyl cinnamonitrile; butyl cinnamoyl pyruvate); Dihydroxy- cinnamic acid derivatives (umbelliferone, methylumbel1iferone, methylaceto-umbel1iferone) ; Trihydroxycinna ic acid derivatives (esculetin, methylesculetin, daphnetin, and the glucosides, esculin and daphnin); Hydrocarbons (diphenylbutadiene, stilbene); Dibenzalacetone and benzalacetophenone;

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2-Phenylbenzimidazole-5-sulfonic acid and its salts; Naphtholsulfonates (sodium salts of 2-naphthol 3,6-disulfonic and of 2-naphthol-6,8-disulfonic acids); Dihydroxy-naphthoic acid and its salts; o- and p-Hydroxybiphenyl- disulfonates; Cou arin derivatives (7-hydroxy, 7-methyl, 3-phenyl); Diazoles (2-acetyl-3-bromoindazole, phenyl benzoxazole, methyl naphthoxazole, various aryl benzothi- azoles); Quinine salts (bisulfate, sulfate, chloride, oleate, and tannate); Quinoline derivatives (8-hydroxyquinoline salts, 2-phenyl- quinoline); Hydroxy- or methoxy-substituted benzophenones; Uric and vilouric acids; Tannic acid and its derivatives (e.g., hexaethyl- ether); (Butyl carbityl) (6-propyl piperonyl) ether; Hydroquinone; Benzophenones (Oxybenzene, Sulisobenzone, Dioxybenzone, Benzo- resorcinol, 2,2\',4,4\'-Tetrahydroxybenzophenone, 2,2\'-Dihy- droxy-4,4\'-dimethoxybenzophenone, Octabenzone; 4-Isopropyldiben- zoylmethane; Butylmethoxydibenzoylmethane; Octocrylene; 4-isopropyl- dibenzoylmethane; and camphor derivatives such as methyl benzylidene or benzyl dene camphor; triethanolamine salicylate; and mixtures thereof. Other sunscreens include the solid physical sunblocks such as titanium dioxide (micronized titanium dioxide, 0.03 microns, 0.035 microns, 0.050 microns, and other suitable sizes), zinc oxide, silica, iron oxide and the like. Without being limited by theory, it is believed that these inorganic materials provide a sunscreening benefit through reflecting, scattering, and absorbing harmful UV, visible, and infrared radiation. Other useful sunscreens are those having both a UVA and a UVB absorbing chromophore in the same molecule as disclosed in U.S. Patent Nos. 5,041,282, 4,999,186 and 4,937,370, and European Patent Application No. 416,837, which have already been incorporated by reference herein. Generally, these additional sunscreens can comprise from zero to about 20% of the composition, preferably from about 0.5% to about 10%. Exact amounts will vary depending upon the sunscreen chosen and the desired Sun Protection Factor (SPF). SPF is a commonly used measure of photoprotection of a sunscreen against erythema. See Federal Register. Vol. 43, No. 166, pp. 38206-38269, August 25, 1978.

In addition to these sunscreen agents, the compositions can also contain one or more artificial tanning ingredients such as dihydroxyacetone, tyrosine, a ino acids, and amino acid derivatives. Typically, artificial tanning ingredients can be incorporated into the compositions of the instant invention at levels from about 0.1% to about 10%, and preferably at levels from about 0.1% to about 5%. Thickeners

Another optional component of the compositions of the instant invention is a thickener. Examples of such thickeners which can be employed include, but are not limited to, xanthan gum, magnesium aluminum silicate, guar gum, cationic guar gum, Rhamsan Gum (available from Kelco Chemical Co.), kelp, algin and alginate salts, starch and starch derivatives, hydroxypropylcellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, ethylcellulose, smectite clay thickeners such as hectorite and bentonite, sodium magnesium silicate and mixtures thereof. Examples of suitable thickeners are disclosed in Lochhead, R.Y., "Encyclopedia of Polymers and Thickeners", Cosmetics & Toiletries, vol. 103, no. 12, pp. 99-129 (1988); Meer, G., "Natural Gum Polymers as Ingredients in Cosmetics", Cosmetics & Toiletries, vol. 99, no. 6, pp. 61-64 (1984); and Freeland, M.S. "Cationic Guar Gum", Cosmetics & Toiletries, vol. 99, no. 6, pp. 83-87 (1984); these three references are incorporated herein by reference in their entirety. Preferred thickeners include magnesium aluminum silicate and xanthan gum and mixtures thereof. The compositions of the instant invention comprise from about 0.1% to about 5% thickener, preferably from about 0.25% to about 2%, and most preferably from about 0.5% to about 1%. Humectants/Moisturizers The compositions of the instant invention can also optionally contain one or more humectants/moisturizers. A variety of humectants/moisturizers can be employed and can be present at a level of from about 0.5% to about 30%, more preferably from about 2% to about 8% and most preferably from about 3% to about 5%. These materials include urea; guanidine; glycolic acid and glycolate salts (e.g. ammonium and quaternary alkyl ammonium); lactic acid and lactate salts (e.g. ammonium and quaternary alkyl ammonium);

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polyhydroxy alcohols such as sorbitol, glycerin, hexanetriol, propylene glycol, hexylene glycol and the like; polyethylene glycol; sugars and starches; sugar and starch derivatives (e.g. alkoxylated glucose); panthenol ; hyaluronic acid; lactamide monoethanolamine; acetamide monoethanolamine; and mixtures thereof.

Preferred humectants/moisturizers for use in the compositions of the present invention are the C3-C5 diols and triols. Especially preferred is the triol, glycerin.

Emollients The compositions of the present invention can also optionally comprise at least one emollient. Examples of suitable emollients include, but are not limited to, volatile and non-volatile silicone oils, highly branched hydrocarbons, and non-polar fatty acid and fatty alcohol esters, and mixtures thereof. Emollients useful in the instant invention are further described in U.S. Patent No. 4,919,934, to Deckner et al., issued April 24 1990, which is incorporated herein by reference in its entirety.

The emollients can typically comprise in total from about 1% to about 50%, preferably from about 1% to about 25%, and more preferably from about 1% to about 10% by weight of the compositions of the present invention. Emulsi iers

Another optional component of the compositions of the instant invention is at least one emulsifier. Suitable emulsifiers can include any of a wide variety of nonionic, cationic, anionic, and zwitterionic emulsifiers disclosed in the prior patents and other references. See McCutcheon\'s, Detergents and Emulsifiers. North American Edition (1986), published by Allured Publishing Corpor¬ ation; U.S. Patent No. 5,011,681, to Ciotti et al, issued April 30, 1991; U.S. Patent No. 4,421,769, to Dixon et al., issued December 20, 1983; and U.S. Patent No. 3,755,560, to Dickert et al., issued August 28, 1973; these four references are incorporated herein by reference in their entirety.

Suitable emulsifier types include esters of glycerin, esters of propylene glycol, fatty acid esters of polyethylene glycol, fatty acid esters of polypropylene glycol, esters of sorbitol, esters of sorbitan anhydrides, carboxylic acid copolymers, esters and ethers of glucose, ethoxylated ethers, ethoxylated alcohols, alkyl

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phosphates, polyoxyethylene fatty ether phosphates, fatty acid amides, acyl lactylates, soaps and mixtures thereof.

Suitable emulsifiers can include, but are not limited to, poly¬ ethylene glycol 20 sorbitan monolaurate (Polysorbate 20), polyethylene glycol 5 soya sterol, Steareth-20, Ceteareth-20, PPG-2 methyl glucose ether distearate, Ceteth-10, Polysorbate 80, cetyl phosphate, potassium cetyl phosphate, diethanola ine cetyl phosphate, Polysorbate 60, glyceryl stearate, PEG-100 stearate, and mixtures thereof. The emulsifiers can be used individually or as a mixture of two or more and comprise from about 0.1% to about 10%, preferably from about 1% to about 7%, and most preferably from about 1% to about 5% of the compositions of the present invention. Vitamins Optionally, various vitamins can also be included in the compositions of the present invention. Non-limiting examples include Vitamin A, and derivatives thereof, ascorbic acid, Vitamin B, biotin, Vitamin D, Vitamin E and derivatives thereof such as tocopheryl acetate, panthothenic acid, and mixtures thereof can also be used.

Carboxylic Acid Copolymers

Another optional component of the compositions of the instant invention is a carboxylic copolymer (acrylic acid copolymer). Most preferred is Carbomer 1342 (available as Carbopol 1342 from B.F. Goodrich). These polymers are more fully described in U.S. Patent No. 4,509,949, to Huang et al., issued April 5, 1985, and U.S. Patent No. 2,798,053, to Brown, issued July 2, 1957, these patents being incorporated herein by reference. Also useful are the acrylate/alkyl acrylate crosspolymers such as Acrylates/C10-C30 Alkyl Acrylate Crosspolymer (available as Pemulen TR-1 and Pemulen TR-2 from Goodrich). Reference to Include Pemulens.

These polymers comprise from about 0.025% to about 0.75%, preferably from about 0.05% to about 0.25% and most preferably from about 0.075% to about 0.175%. Other Optional Components

A variety of additional ingredients can be incorporated into the emulsion compositions of the present invention. Non-limiting

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examples of these additional ingredients include various polymers for aiding the film-forming properties and substantivity of the composition (such as a copolymer of eicosene and vinyl pyrrolidone, an example of which is available from GAF Chemical Corporation as Ganex V-220R); gums, resins, and thickeners; preservatives for maintaining the antimicrobial integrity of the compositions; antioxidants; chelators and sequestrants; anti-acne agents; keratolyic agents;and agents suitable for aesthetic purposes such as fragrances, pigments, and colorings. Other useful materials include acidic materials such as salicylic acid, lactic acid, glycolic acid, benzoic acid, citric acid and the like. Without being limited by theory, it is believed that these acid materials are useful for maintaining the pH of the composition and enhancing product performance. Method for Preventing Sunburn

The present invention further relates to a method for pro¬ tecting the skin of humans or lower animals from the effects of UVA and UVB wavelength radiation, such as sunburn and premature aging of the skin. Such a method comprises topically applying to the human or lower animal an effective coating of a sunscreen agent or composition of the present invention. The term "effective coating", as used herein, means a film of sunscreen agent sufficient to substantially reduce the amount of UVA and UVB wavelength light which reaches the skin\'s surface. Typically, an effective coating of the skin is from about 0.5 mg sunscreen agent or composition of the present invention/cm ² skin to about 5 mg sunscreen agent or composition of the present invention/cm ² skin. See Federal Register. Vol. 43, No. 166, pp. 38206-38269, August 25, 1978.

The following examples further describe and demonstrate the preferred embodiments within the scope of the present invention. The examples are given solely for the purpose of illustration, and are not to be construed as limitations of the present invention since many variations thereof are possible without departing from its spirit and scope. EXAMPLE I

Preparation of the Aluminum (III) Complex of 4,4\'-methoxy-t-butyl- dibenzoylmethane using Aluminum Diacetate.

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In a 1000-mL flask, 3.5 grams (0.0216 moles) of aluminum diacetate (Aldrich Chemical Co., Milwaukee, WI), is added to approximately 500 L of absolute ethanol and heated to boiling for approximately 10 minutes. In a separate 500-mL flask, 11.78 grams (0.038 moles) of 4,4\'-methoxy-t-butyldibenzoylmethane is added to approximately 100 L of acetone and heated to boiling for approximately 10 minutes. Next, a solution of 10 mL of an 11% (w/w) aqueous solution of sodium hydroxide is added to the acetone solution of the sunscreen, and the mixture is vigorously agitated until miscible. The sunscreen solution is then slowly added to the aluminum diacetate solution with stirring, and the mixture is refluxed for approximately 10 minutes. Next, the solvents are removed by rotary evaporation to yield the crude sunscreen aluminum complex. This crude complex is redissolved in approximately 150 L of methylene chloride with heating and is then vacuum filtered using a coarse, sintered glass funnel to remove any undissolved materials, which are washed with methylene chloride (approximately 2 X 20 L). (Alternatively, other suitable solvents such as chloroform, ethyl acetate or methyl t-butyl ether can be used for this redissolving step.) The pooled filtrates are extracted with water (approximately 2 X 100 mL), dried over sodium sulphate, and evaporated by rotary evaporation to yield the sunscreen aluminum complex as a light yellow, glassy solid. This solid is suitable for incoporation into a sunscreen composition. Characterization:

UV-Vis Spectrum: ^λ max 366 nm, A = 1.3502 (10 ppm in 50:50 DMSO:Chloroform)

EXAMPLE 2 Preparation of the Aluminum (III) Complex of 4,4\'-methoxy-t-butyi- dibenzoylmethane using Aluminum Monoacetate.

In a 1000-mL flask, 33.75 grams (0.240 moles) of aluminum monoacetate (basic, stabilized with boric acid: Aldrich Chemical Co., Milwaukee, WI) is added to approximately 300 mL of absolute ethanol and heated to boiling for approximately 10 minutes. In a separate 500-mL flask, 106.33 grams (0.343 moles) of 4,4\'-methoxy- t-butyl-dibenzoylmethane acid ester with 4-hydroxydibenzoylmethane is added to approximately 200 L of acetone and heated to boiling

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for approximately 10 minutes. Next, a solution of 80 mL of an 11%

(w/w) aqueous solution of sodium hydroxide is added to the acetone solution of the sunscreen, and the mixture is vigorously agitated until miscible. The sunscreen solution is then slowly added to the aluminum monoacetate solution with stirring, and the mixture is refluxed for approximately 10 minutes. Next, the solvents are removed by rotary evaporation to yield the crude sunscreen aluminum complex. This crude complex is redissolved in approximately 300 L of methylene chloride with heating, and is then vacuum filtered using a coarse, sintered glass funnel to remove any undissolved materials, which are washed with methylene chloride (approximately 2

X 50 mL). The pooled filtrates are extracted with water, dried over sodium sulphate, and evaporated by rotary evaporation to yield the sunscreen aluminum complex as a light yellow, glassy solid. This solid is suitable for incorporation into a sunscreen composition.

EXAMPLE 3 Preparation of the Aluminum (III) Complex of 4,4\'-methoxy-t-butyl- d benzoylmethane using Aluminum Distearate.

In a 500-mL flask 2.0 grams (3.28 mmoles) of aluminum distearate (Aldrich Chemical Co., Milwaukee, WI) is added to 100-ml of Ci -15 alcohols benzoate and the mixture is heated to 90°C until dissolved. Next, 1.17 grams (3.78 mmoles) of 4,4\'-methoxy-t-butyl- dibenzoylmethane is added with stirring to form the sunscreen aluminum complex. This oil phase solution of the sunscreen metal complex is suitable for incorporation into an emulsion or gel composition. (Alternatively, other solvents useful in this preparation include dimethyl isosorbide, isodecyl neopentanoate, and diisopropyl adipate.)

EXAMPLE 4 Preparation of the Aluminum (III) Complex of 4,4\'-methoxy-t-butyl- dibenzoylmethane using Aluminum Dioctanoate.

Using the procedue given in Example 3, this sunscreen aluminum complex is prepared starting with 1.0 gram of aluminum dioctanoate

(Aldrich Chemical Co., Milwaukee, WI). The resulting oil phase solution of the complex is suitable for incorporation into an emulsion or gel composition.

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EXAMPLE 5 Preparation of the Aluminum (III) Complex of 4-isopropyldibenzoyl - methane using Aluminum Monoacetate.

Using the procedure of Example 2 this sunscreen aluminum complex is prepared using 33.75 grams (0.240 moles) of aluminum monoacetate and 91.24 grams (0.343 moles) of 4-isopropyldibenzoyl- methane. A light yellow solid is obtained suitable for incorporation into a sunscreen composition.

EXAMPLE 6 Oil based gel composition containing Aluminum (III) Complex of 4,4\'-methoxy-1-butyldibenzoylmethane.

4.0 grams of the sunscreen aluminum complex prepared in Example 1 is added to 100 grams of Cχ2-15 Alcohols Benzoate by heating to 90°C. The mixture is cooled to 80°C and 1 gram of dibutyllaurolyl glutamide (available as Coagulen GP-1 from Ajinomoto Co., Inc., Tokyo, Japan) is added to gel the mixture upon cooling. This gel composition is useful for topical application to the skin to provide protection from the harmful effects of ultraviolet radiation.

Alternatively, analogous gel compositions can be prepared using the other sunscreen metal complexes of the instant invention and with other solvents such as isodecylneopentanote, diisopropyl adipate, and dimethylisosorbide.

EXAMPLE 7 Sunscreen emulsion prepared via the in situ preparation of the Aluminum (III) Complex of 4,4\'-methoxy-t-butyldibenzoylmethane.

An emulsion composition is prepared from the following ingredients using standard methods.

Ingredient Percent (w/w)

Phase A Ci2-15 Alcohols Benzoate 9.00

Aluminum Stearate 1.00

4,4\'-methoxy-t-butyldibenzoylmethane 1.00

Phase B

Isodecyl Noepentanoate 3.00 Isohexadecane 2.00

DEA-Cetyl Phosphate 1.80

Dimethicone 0.75

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Cyclomethicone 0.50

Aluminum Starch Octenylsuccinate 1.00

Cetyl Alcohol 1.40

Stearic Acid 1.00 Ethylparaben 0.15

Titanium dioxide 0.50

Phase C Water QS100

Acrylates/C10-30 Alkyl Acrylate Crosspolymer 0.075

Carbomer 951 0.050

Carbomer 954 0.050

Methylparaben 0.30

Hexylene Glycol 0.50 Glycerol 1.00

Disodium EDTA 0.05

Phase D Fragrance 0.14

Fragrance 0.21 Benzyl Alcohol 0.30

Triethanolamine 0.175

Water 1.40

The Phase A ingredients are combined and heated to 90°C and then cooled to 80°C. Next, the Phase B ingredients are added with mixing at 80°C to form the oil phase. In another vessel, the Phase C ingredients are combined and heated to 80°C. The oil phase is added to Phase C with homogenization to form the emulsion. The emulsion is cooled with stirring to 40°C. Next, the Phase D ingredients are combined and added to the emulsion with mixing. The emulsion is then cooled to room temperature with stirring.

This emulsion composition is useful for topical application to the skin to provide protection from the harmful effects of ultraviolet radiation.

Alternatively, the above sunscreen emulsion is prepared using 0.50 grams of aluminum dioctoate in place of the aluminum distearate.

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EXAMPLE 8 Sunscreen emulsion prepared with the isolated Aluminum (III) Complex of 4,4\'-methoxy-1-butyldibenzoylmethane.

An emulsion composition is prepared from the following ingredients using standard methods.

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The Phase A ingredients are combined and heated with mixing to 90°C and then cooled to 80°C. In a separate vessel, the Phase B ingredients are combined and heated wtih mixing to 80OC. The Phase A mixture is added to the Phase B mixture with homogenization to form the emulsion. The emulsion is cooled with stirring to 40°C. Next, the Phase C ingredients are combined and added to the emulsion with mixing. The emulsion is then cooled to room temperature with stirring.

This emulsion composition is useful for topical application to the skin to provide protection from the harmful effects of ultraviolet radiation.

Alternatively, analogous emulsions are prepared using other isolated sunscreen metal complexes of the instant invention.

EXAMPLE 9 Sunscreen emulsion prepared with the isolated Aluminum (III) Complex of 4,4\'-methoxy-t-butyldibenzoylmethane.

Ingredient Percent (w/w)

Phase A Isosteareth-20 3.00 Cetyl Alcohol 1.50

Stearic Acid 1.50

Ci -15 Alcohols Benzoate 7.00

Dimethyl Isosorbide 7.00

Aluminum Complex of 4,4\'-methoxy- t-butyldibenzoylmethane

(Prepared as in Example 1) 6.00

Phase B Water QS100

Methylchioroisothiazolinone (and) Methylisothiazolinone 0.100

The Phase A ingredients are combined and heated with stirring to

80°C to form the oil phase. Next, the Phase B ingredients are combined and heated with stirring to 80°C. Phase A is added to

Phase B with homogenization to form the emulsion which is then cooled to room temperature with stirring.

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This emulsion composition is useful for topical application to the skin to provide protection from the harmful effects of ultraviolet radiation.

Alternatively, analogous emulsions are prepared using other isolated sunscreen metal complexes of the instant invention.

WHAT IS CLAIMED IS:

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