Use of cyclic enamines as light protection agents

Details Use of cyclic enamines as light protection agents Use of cyclic enamines as light protection agents

2000-05-31

2002-07-02

Dodson, Shelley A. (Department: 1616)

Drug, bio-affecting and body treating compositions

Topical sun or radiation screening, or tanning preparations

C424S060000, C424S400000, C424S401000

Reexamination Certificate

active

06413503

ABSTRACT:

The invention relates to the use of bicyclic and tricyclic enamines which carry electron-withdrawing substituents on the-ene double bond as light protection agents in cosmetic and pharmaceutical preparations and as light protection additives (light stabilizers) in plastics. The invention further relates to novel compounds of said type which have a light protection action.
The light protection agents used in cosmetic and pharmaceutical preparations have the task of preventing, or at least diminishing the consequences of, harmful effects of sunlight on the human skin. However, these light protection agents also serve to protect other ingredients from decomposition or breakdown by UV radiation. In hair cosmetic formulations, the aim is to reduce damage to the keratin fibers by UV rays.
The sunlight reaching the surface of the earth contains UV-B radiation (280 to 320 nm) and UV-A radiation (>320 nm), which are directly adjacent to the visible light region. The effect on the human skin is manifested, particularly in the case of UV-B radiation, by sunburn. Accordingly, the industry offers a relatively large number of substances which absorb UV-B radiation and thus prevent sunburn.
Dermatological investigations have now shown that UV-A radiation is also perfectly capable of causing skin damage and allergies by, for example, damaging the keratin or elastin. This reduces the elasticity and water storage capacity of the skin, i.e. the skin becomes less supple and tends to form wrinkles. The noticeably high incidence of skin cancers in areas of strong solar radiation shows that damage to the genetic information in the cells is evidently also caused by sunlight, specifically by UV-A radiation. All these findings would therefore suggest that it is necessary to develop efficient filter substances for the UV-A region.
There is a growing demand for light protection agents for cosmetic and pharmaceutical preparations which can be used in particular as UV-A filters and whose absorption maxima ought therefore to be in the range from about 320 to 380 nm. In order to achieve the desired effect using the minimum amount, light protection agents of this type should additionally have a high specific absorbance. Light protection agents for cosmetic preparations must also meet a large number of other requirements, for example good solubility in cosmetic oils, high stability of the emulsions prepared therewith, toxicological acceptability and low intrinsic odor and low intrinsic color.
Another requirement which light protection agents must meet is adequate photostability. However, this requirement is met only inadequately, if at all, by the UV-A-absorbing light protection agents available hitherto.
French Patent No. 2 440 933 describes 4-(1,1-dimethylethyl)-4′-methoxydibenzoylmethane as a UV-A filter. It is proposed to combine this particular UV-A filter, which is sold by GIVAUDAN under the name “PARSOL 1789”, with various UV-B filters in order to absorb all UV rays having a wavelength from 280 to 380 nm.
However, this UV-A filter does not have sufficient photochemical stability, when used alone or in combination with UV-B filters, to ensure sustained protection of the skin during sunbathing for extended periods, which means that repeated applications at regular and short intervals are required if effective protection of the skin from all UV rays is desired.
For this reason, EP-A-0 514 491 discloses the stabilization of the insufficiently photostable UV-A filters by adding 2-cyano-3,3-diphenylacrylic esters, which themselves act as filters in the UV-B region.
Furthermore, it has already been proposed in EP-A-0 251 398 to combine chromophores which absorb UV-A radiation and UV-B radiation into a molecule via a linker. This has the disadvantage that firstly it is no longer possible to freely combine UV-A and UV-B filters in the cosmetic preparation, and that difficulties in the chemical linkage of the chromophores permit only certain combinations.
U.S. Pat. No. 4,950,467 describes the use of 2,4-pentadienoic acid derivatives as UV absorbers in cosmetic preparations. The monoaryl-substituted compounds specified in this patent specification as being preferable likewise have the disadvantage that their photostability is insufficient.
It is an object of the present invention to propose light protection agents for cosmetic and pharmaceutical purposes which absorb predominantly in the UV-A region (and optionally alternatively in the UV-B region) with high absorbance, are photostable, have low intrinsic color, i.e. a sharp band structure, and are soluble in oil or water depending on the substituent.
We have found that this object is achieved according to the invention by the use of compounds of the formula I
in which
R
1
and R
2
are identical or different, electron-withdrawing radicals chosen from the group consisting of cyano, alkyl- or arylcarbonyl, alkyloxy- or aryloxycarbonyl and optionally substituted aminocarbonyl,
R
3
is a hydrogen atom, a C
1
-C
20
-alkyl radical or a C
3
-C
20
-cycloalkyl radical or a radical of the formula —CH
2
—CH
2
—SO
3
—M
+
, where M
+
is a cation,
X is the divalent radical of oxygen, sulfur or the radical
 where R
3
is as defined above,
Z is the divalent radical of the formula II or III, which forms a fused system with the radical of the formula I
 where R
4
can be bonded one or more times to the benzylidene ring I or naphthylidene ring II, and is hydrogen, alkyl, cycloalkyl, alkyloxy, cycloalkyloxy, alkoxycarbonyl, mono- or dialkylaminocarbonyl, alkylamino, dialkylamino, each having up to 20 carbon atoms, and also cyano, amino and SO
3
—M
+
, where M
+
is a metal cation,
 as photostable UV filters in cosmetic and pharmaceutical preparations to protect human skin and human hair against solar rays, alone or together with compounds which absorb in the UV region and are known per se for cosmetic and pharmaceutical preparations.
Preferred compounds are those in which Z is the radical of the formula II.
With regard to the substituents, preference is given to compounds in which R
1
is cyano or alkyloxycarbonyl having from 2 to 12 carbon atoms, R
2
is hydrogen, R
3
is hydrogen or methyl, and R
4
is C
1
-C
8
-alkyl, C
1
-C
8
-alkoxy or SO
3
—M
+
, where M
+
is a cation chosen from the group consisting of
where R
5
, R
6
and R
7
are hydrogen or low molecular weight alkyl or hydroxyalkyl, and metal cations.
The alkyl radicals in the substituents R
1
to R
4
preferably have from 1 to 8 carbon atoms and are, in particular, low molecular weight alkyl radicals having from 1 to 5 carbon atoms and, preferably, methyl radicals.
The alkyl radicals in the substituents R
4
are isocyclic or heterocyclic radicals having from 5 to 10 ring atoms and from 3 to 5 carbon atoms which can be further substituted.
In the radicals —SO
3
—M
+
and —CH
2
—CH
2
—SO
3
—M
+
, M
+
is usually an alkali metal, alkaline earth metal or ammonium cation, in particular Na
+
, K
+
, NH
4
+
,
+
NH(C
2
H
5
)
3
and
+
NH(—CH
2
—CH
2
OH)
3
. Generally speaking, only cations which are physiologically compatible at the use concentrations are suitable.
Of the compounds of the formula I, the compounds of the formula IV are novel
in which R
1
, R
2
, R
3
and R
4
are as defined above.
Equally novel are the compounds of the formula V
which X is the divalent radical of oxygen, sulfur or the radical
and R
1
and R
2
independently of one another are CN or alkoxycarbonyl having from 2 to 10 carbon atoms which can be substituted by a radical —(CH
2
)
n
—SO
3
—M
+
, R
3
is hydrogen, methyl or —(CH
2
)
n
—SO
3
—M
+
, and R
4
is hydrogen or one or more identical or different radicals C
1
- to C
8
-alkyl, C
1
- to C
8
-alkoxy or the radical —SO
3
—M
+
, where in each case n is the number 2 or 3 and M
+
is a cation chosen from the group consisting of
in which R
5
, R
6
and R
7
are hydrogen or low molecular weight alkyl or hydroxyalkyl, and metal cations,
with the proviso that the compound of the fo

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