WO1989012080A1

WO1989012080A1 - Novel merocyanine dyes

Info

Publication number: WO1989012080A1
Application number: PCT/US1989/002303
Authority: WO
Inventors: Wolfgang Hans Heinrich Gunther; Frederick Joseph Sauter
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1988-06-08
Filing date: 1989-05-30
Publication date: 1989-12-14
Anticipated expiration: 1990-12-08
Also published as: EP0418291A1

Abstract

A merocyanine dye having formula (I) wherein X=O, Se or S; R1 and R2 independently are H, alkyl, alkoxy or carbocyclic aryl, with the stipulation that if X=S, then R1 and R2 are independently selected from a group consisting essentially of alkyl, alkoxy and aryl and if X=O, then only one of R1 and R2 are H; R7 and R8 are H and any of R1 and R2, R1 and R7, and R2 and R8 can together comprise the atoms necessary to form a fused 6-membered carbocyclic aromatic ring on the benzene radical to which they are attached; R5 and R6 are selected independently from a group consisting essentially of benzyl and alkyl of from 1-18 carbon atoms, provided that the sum of the carbon atoms in R5 and R6 together is at least 8; R9 is an alkylene group of 2-9 nuclear carbon atoms and CONH-groups; and Z+ is a cation. This dye is useful in a method for inactivating viruses comprising contacting the viruses with the compound and exposing the resulting mixture to visible light to excite and inactivate the viruses. The compounds are also useful in the irradiation-induced inactivation of leukemia cells.

Description

NOVEL MEROCYANINE DYES

Viruses can cause human or animal diseases.

The inability to effectively inactivate pathogenic viruses without adversely affecting their antigenic properties has made it difficult to make safe, effective vaccines for viral diseases. In addition, the presence of viruses can destroy the utility of valuable food and industrial products.

Heat treatments, the extraction of virus with solvents and detergents, and the treatment with high doses of gamma radiation can be effective means of inactivating viruses. However, those procedures are rigorous and nonspecific and their applicability is limited. As a result, there is a need for a simple, effective method for inactivating viruses. A merocyanine dye MC540 is a useful agent which preferentially binds to the lipids in enveloped viruses or virus-infected cells and does not or binds only minimally to the other components of the cells to inactivate the viruses and virus-infected ce.lls. The MC540 dye and its use in eliminating tumor cells from bone marrow grafts is described in "Elimination of Residual Tumor Cells from Autologous Bone Marrow Grafts by Dye-Mediated Photolysis: Preclinical Data", by Dr. Fritz Sieber in Photo- chemistry and Photobiologv. Vol. 46, No. 1, pages 71-76, (1987). There is a need for more effective compounds suitable for use with photosensitization for inactivating viruses and for removing tumor cells.

Thus, the problem to be solved by the present invention is to provide new compounds which are useful as antiviral agents. In accordance with the present invention, there are provided novel merocyanine dyes that can be brought into contact with an effective amount of a photosensitizing agent and exposed to visible light until the viruses and virus-infected cells have been inactivated. It has been found that these novel dyes are also useful for selectively killing leukemic cells in bone marrow by photosensitization.

A merocyanine dye having the formula:

wherein:

X=0, Se or S

R, and R₂ independently are H, alkyl, alkoxy or carbocyclic aryl, and with the stipulation that, if X=S or 0, R, and R~ are selected independently from a group consisting essentially of alkyl, alkoxy or carbocyclic aryl;

R-, and g are H; and any of R^ and R«> i, Ry. and R₂ and Rg can together comprise the atoms necessary to form a fused 6-membered carbocyclic ring on the benzene radical to which they are attached;

Re and R, are selected independently from a group consisting essentially of alkyl and benzyl of from 1—18 carbon atoms, provided that the sum of the carbon atoms in R₅ and Rg together is at least 8; Ro is an alkylene group of 2-9 nuclear carbon and hetero atoms and CONH-groups ; and Z⁺ is a cation.

The novel compounds useful as anti-viral agents and in the inactivation of leukemia cells have the formula:

X is selected for the group consisting of 0, Se and S

R, and R₂ can each independently comprise H, alkyl of about 1 to 10 carbon atoms such as methyl, ethyl, propyl, butyl, and hexyl; alkoxy such as ethoxy, ethoxy, and the like, wherein the alkyl group contains from 1 to 3 carbon atoms and carbocyclic aryl, such as phenyl, including substituted phenyl, such as tolyl, and the like with the stipulation that if X=S or 0, R, and R₂ are selected independently from a group consisting essentially of alkyl, alkoxy and carbocyclic aryl. R-, and R_g are H and any pair of R, and R,, R, and R₂ or

R₂ and R_g can comprise the atoms necessary to form together with the atoms on the benzene radical to which they are attached, a fused 6-membered carbocyclic aromatic ring, such as a benzo ring, including a substituted benzo ring, such as a methyl-substi- tuted benzo ring and the like. R₅ and R₆ are independently selected from groups consisting essentially of alkyl or benzyl groups containing from about 1 to about 18 carbon atoms provided that the sum of the carbon atoms in R_e and R, is at least 8 such as methyl, ethyl, propyl, butyl, heptyl, and including branched and substituted alkyl, such as chloropropyl, methoxymethyl, iso- propyl, benzyl, JL—butyl, sec-butyl, neopentyl, and the like. g is a straight or branched alkylene group of 2 to 9 nuclear carbon atoms and CONH-groups forming the alkylene chain including alkylene chains comprising hetero atoms, or hetero atom-containing groups in the linear alkylene chain or nucleus in the case of branched chains, for example, ethylene, ethylidene, tri— methylene, propylene, propylidene, benzylidene, 3-oxo-4-imino-5,5-dimethyl—1,6-hexylene, and the like, preferably R_Q is a trimethylene group.

Z + is any cation such as Na+, l/2Ba2+,

(C₂H₅)₃NH⁺, ⁺, NH+, and Li⁺.

Preferred merocyanine dyes of the invention include: Compound 1

Compound 2

Compound

15 Compound 4

and

Compound 5

Compound 6

35 Compound 7

Compound

The compounds of the invention can be synthesized by condensation of a 2-methyl-3-sulfo- alkyloxazolium hydroxide or a 2-methyl—3—sulfo— alkylselenazolium hydroxide or a 2—ethyl—S— alkylthiazolium hydroxide or a 3,3-disubstituted- 2-methyl—1-sulfoalkyl—3H-indolium hydroxide, inner- salt with a 1,3—di— substituted

5-(3—alkoxy—2-propen-l—ylidene)—2—thio- barbituric acid in the presence of a tertiary amine such as triethylamine and a solvent such as aceto— nitrile or ethanol, with warming or gentle heating to form the ammonium sulfonate salt followed by cation exchange if desired (for example, treatment with sodium iodide to produce the sodium salt of the merocyanine dye or with barium acetate to form the barium salt), and finally treatment with a nonsolvent if necessary to precipitate the dye.

Alternatively, a 5-unsubstituted barbituric acid can be condensed with the hydroxide, inner salt under similar conditions. The starting oxazolium hydroxide, inner salt is most conveniently prepared by an addition reaction of a sultone such as propane sultone, butane sultone, etc., to a parent oxazole such as 2—methyl[1,2—d]- naphthoxazole.

Alternatively, such inner salts can be prepared by an addition reaction between a parent oxazole such as I above and an unsaturated sulfonic acid such as 2-acrylamido-2-methylpropanesulfonic acid as follows:

The starting thiazolium hydroxide, inner salt is most conveniently prepared by an addition reaction of a sultone such as propane sultone, butane sultone, etc., to a parent thiazole such as a 2-methylbenzothiazole.

Alternatively, such inner salts can be prepared by an addition reaction between a parent thiazole such as I above and an unsaturated sulfonic acid such as 2— acrylamido— 2— methylpropanesulfonic acid as follows :

heaz∑t>

The starting selenazolium hydroxide, inner salt is most conveniently prepared by an addition reaction of a sultone such as propane sultone, butane sultone, etc., to a parent benzoselenazole such as a 2-methylbenzo[d]selenazole.

(CH₂)₃S0₃

Alternatively, such inner salts can be prepared by an addition reaction between a parent selenazole such as I above and an unsaturated sulfonic acid such as 2—acrylamido—2—methylpropane— sulfonic acid as follows:

The 1,3-disubstituted-5-(3-alkoxy-2-pro- pen-l-ylidene)-2-thiobarbituric acid derivatives are prepared by the condensation of 1,3,3-trimethoxy-l- propene with the parent 1,3-disubstituted thiobarbi- turic acid. The product is formed spontaneously as the reactants are mixed in acetone. The disubsti- tuted thiobarbituric acid is obtained by condensation of an N,N'—disubstituted thiourea with diethyl malonate. The N,N'-disubstituted thioureas can be purchased commercially or prepared by conventional alkylation of the nitrogen atoms on the thiourea. The hydroxide, inner salt used in the alternative procedure is prepared by reaction of the parent hydroxide, inner salt with 1—anilino—3—phenylimino—1—propene hydrochloride available from Aldrich Chemical Co. These compounds have been found to be useful as agents to destroy or inactivate viruses with the aid of photosensitization. The toxicity of these compounds is relatively low.

The compounds are normally used with light of suitable wavelength in an amount of about 5 to about 25 micrograms per milliliter of product.

The effective wavelengths of visible light that can be used vary greatly depending upon the absorption spectrum of the individual dyes; however, it is generally desired that the light be of a wavelength in the green to orange range. It appears, as expected, that light that is not absorbed, i.e., blue light and long wavelength red light, is not particularly effective with these compounds. Tests have shown that:

1) Suspensions of Friend virus, Friend virus-transformed cells, Herpes simplex, HTLV-I and HTLV-I infected cells and Human Cytomegalovirus (CMV) are rapidly inactivated by photosensitization with these compounds.

2) The small amounts of dye that are trans- ferred with the photosensitized products or plasma/- serum components are not toxic to mice. The effective amount of some of these compounds is about

100,000 times less than the LD,_Q of the compound in mice.

The ability of these compounds to react with enveloped (i.e., lipid—containing) viruses was tested with the Friend erythroleukemia virus complex, the human T cell leukemia virus, HTLV-I and Herpes simplex 1. Friend virus was obtained from cell—free supernatants of cultured erythroleukemia cells or as a cell—free extract from infected animals. Simul— taneous exposure to the compounds (15 ug/ml) and

2 light (40 J/cm ) reduced the virus titer regardless of the origin of the virus preparation. Virus- infected spleen cells, bone marrow cells, and cultured Friend erythroleukemia cells were inacti- vated at about the same rate as cell-free virus ' preparations.

HTLV—I was also susceptible to the com¬ pound-mediated photosensitization. The amount-of virus that could be sedimented by centrifugation was reduced after treatment with the compounds and light. The remainder of the virus were probably lysed. The small fraction that was sedimented was visibly stained by the compound. It is conceivable that the sedimented virus fraction, although not lysed, had sustained enough photodynamic damages to make it noninfectious. For example, when the virus is Herpes simplex 1, the order of magnitude reduction is from 45 to 100 times.

The demonstrated effectiveness of this method in inactivating Herpes simplex 1 makes it possible to treat herpes lesions by applying or injecting the compound-containing preparations onto or into the lesions. The ability of the compounds to photo¬ sensitize in such low concentrations should make it possible to use the dyes in dermatological products which can be painted on or injected into viral- containing lesions prior to exposure to visible light The compounds which we have labeled Compound

3, 6 and 7 above reduce illumination times about six-fold in comparison to Merocyanine 540 when used in equimolar concentrations.

The compound-mediated photolysis of viruses appears to be primarily mediated by singlet oxygen. An additional two-fold reduction in illumination time can therefore be achieved by performing the photo¬ sensitization step in the presence of deuterium oxide (D₂0). Unlike heat or high doses of ionizing irradiation, this compound-mediated photolysis is more selective in its toxicity. Dye-mediated photosensitization may be the preferred anti-viral treatment in situations where critical components are temperature- or radiation-sensitive. In addition, the acute systemic toxicity of these dyes is very low. Also, the amount of dye that is injected with a typical mouse bone marrow graft is more than 100,000 times less than the L _IQ n the same species. Surprisingly, tests have shown that inactivated viruses retain their antigenic proper¬ ties. Thus, it should be possible to make vaccines using the viruses inactivated by the method of the present invention. Representative of the viruses which can be inactivated by the compounds of the present invention are those previously described as well as the viruses which cause human and animal diseases, such as bovine viral diarrhea, the human immunodeficiency viruses (HIV, HTLV-III, LAV) and viruses which infect bacterial products, such as the Epstein Barr virus.

These novel compounds are also useful in eliminating residual tumor cells from bone marrow grafts by treatment with photolysis. These compounds bind to the lipid portion of the plasma membrane and the photolysis with these compounds is effective against a broad range of leukemias and solid tumors, including drug-resistant tumors. The advantageous use of these compounds is that normal circulating leukocytes, coagulation proteins and red cells have a low affinity to them and light in the presence of serum appears to have little or no acute cytotoxic effects. This invention is further illustrated by the following examples. Example 1

Preparation of

To a reactor was added 0.61 g (2 mmole) of

prepared from the parent 2—methylnaphthoxazole and propane sultone and 0.65 g (2 mmole)

obtained from the condensation of the disubstituted thiobarbituric acid with 1,3,3—trimethoxy-1-propene

The former compound was added in 25 ml of ethyl alcohol.

To this mixture was added 0.3 ml triethyl- amine (TEA). The mixture was boiled for five minutes, allowed to cool and filtered. 50 ml of ethyl alcohol was added and the mixture was again filtered.

The product (0.7 gram) had a calculated molecular weight of 698.95, γ-max of 565 nm in methanol, an extinction coefficient ε = 13.1 X 10 , and a fluorescence emission maximum at 594 nm. The UV visible spectrum is consistent with the assigned structure and the compound was shown to be pure by both electrophoresis and thin layer chroma- tography.

Example 2

Preparation of

To a reactor was added 0.67 g (2 mmole)

prepared from the parent 2-methyl-5-phenylbenzoxazole and propane sultone, and 25 ml ethanol. The mixture was boiled for a few minutes and 0.65 g (2 mmole)

was added. To this mixture was added 0.5 ml TEA. The mixture was refluxed for five minutes and allowed to cool. It was then filtered through filter paper and 0.5 g Nal was added. This was stirred for five minutes and the product was filtered off and recrystallized from 100 ml methanol.

The resulting product (0.41 g) had a., calculated molecular weight of 645.78, approximate λ-max of 560 nm in methanol, and an extinction coefficient ε = 17.3 X 10⁴. The UV visible spectrum is consistent with the assigned structure and the compound was shown to be pure by both electrophoresis and thin layer chromatography. Example 3

Preparation of

To a reactor was added 0.57 g (2 mmole) of

prepared from the parent 2-methyl-5-methoxybenzoxa- zole and propane sultone, in 25 ml of ethanol. The mixture was refluxed and 0.65 (mmole)

was added. To this mixture was added 0.5 ml TEA and the resultant mixture was refluxed for five minutes. The mixture was cooled for one hour, filtered, and taken up in 20 ml hot ethanol. The mixture was refluxed, filtered, and chilled to produce crystals. The resulting product (0.52 g) had a calculated molecular weight of 662.92, a λ-max of 560 nm in methanol, a fluorescence emission maximum at 586 nm, and an extinction coefficient ε = 11.9 X 10 . The UV visible spectrum is consistent with the assigned structure and the compound was shown to be pure by both electrophoresis and thin layer chromatography. Example 4 Preparation of

To a reactor was added 0.61 gram (2 mmole)

prepared from the parent 2—raethylnaphthoxazole and propane sultone, in 25 ml ethanol. The mixture was refluxed and 0.65 gram (2 mmole)

was added. To this mixture was added 0.5 ml TEA.

The resulting mixture was refluxed for five minutes, filtered hot and 0.5 g Nal was added and the product filtered after stirring for 15 minutes. The product was obtained after recrystallization in 100 ml methanol.

The resulting product (0.5 gram) had a calculated molecular weight of 619.74, λ-max of 566 nm in methanol, an extinction coefficient ε = 12.6 X 10 , and a fluorescence emission maximum at 595 nm. The UV visible spectrum is consistent with the assigned structure and the compound was shown to be pure by both electrophoresis and thin layer chroma— tography.

Example 5

Preparation of

Part A

Preparation of

A mixture of 10 g of 2-methylnaphth[3,2-d]- oxazole and 7.5 g of propane sultone was prepared in 50 ml of acetonitrile and refluxed for about 70 hours. After cooling, the solid was collected, washed with acetone, then with diethyl ether, and dried to produce 8.4 g. The mother liquors were refluxed another 4.5 days and worked up the same way to produce another 2.7 g. Part P

Preparation of

The inner _rsalt prepared in Part A (6.0 g) was combined with 5.2 g of l-anilino-3-phenylimino- 1-propene hydrochloride in 50 ml of acetic anhydride and heated at reflux for 2 hours. At this time, a sample diluted with acetonitrile and treated with triethylamine showed no evidence of dye formation indicating that all of the starting inner salt had been converted. The mixture was cooled and added to about 350 ml of diethyl ether, stirred, the solid collected by filtration, washed first with diethyl ether and then with acetone. The cake was resu- spended in acetone, collected again and washed with acetone, then with diethyl ether, and dried. Yield = 9.7 g. Part C

Preparation of the Merocyanine Dye A mixture of the acetanilide from Part B (1.6 g) and l,3-dibutyl-2-thiobituric acid (0.85 g) was suspended in about 150 ml of ethanol, heated to a boil, and treated with 1 g of diethylamine. The solution was seeded with a few crystals prepared by scratching a sample in a test tube and allowed to cool. The crystals were collected by filtration, washed with ethanol and with acetone, and dried to produce 1.43 g of dark crystals. These were recrystallized from 200 ml of boiling ethanol. Yield of dark blue crystals = 1.17^"g.

The product had a calculated molecular weight of 698.94, λ-max of 571 nm in ethanol, and an extinction coefficient ε = 25.4 X 10 . A solution of 1.171 mg in 287.1 ml of ethanol had an optical density of 1.484. The UV visible spectrum was consistent with the assigned structure. Example 6 Preparation of

To a reactor was added 1.27 g (4 mmole) of

prepared from the parent 2-methylnaphthoxazole and propane sultone in 50 ml of methanol. To this mixture was added 1.29 g (4 mmole)

obtained from the condensation of the disubstituted thiobarbituric acid with 1,3,3-trimethoxy-l-propene and 1 ml triethylamine (TEA). The mixture was stirred for 20 minutes, filtered, and 1 g Nal was added to the filtrate and stirred for 30 minutes.

The filtered product recrystallized from methanol had a calculated molecular weight of 632.64, a λ-max of 596 nm in methanol, an extinction

4 coefficient ε = 16.9 X 10 , and a fluorescence emission maximum at 622 nm. The UV visible spectrum is consistent with the assigned structure and the compound was shown to be pure by both electrophoresis and thin layer chromatography.

Example 7

Preparation of

Part A

Preparation of

To a reactor was added 20 gram of

available from Aldrich Chemical Co., 13 g of propane sultone, available from Eastman Kodak Co., and 100 ml of acetonitrile. The mixture was heated at reflux for about 20 hours, cooled and filtered to produce a first crop of crystals which were washed with acetone and with ether and dried to yield 10.0 g of white powder. The mother liquors were refluxed for about another 2.5 days. The mixture was diluted with an equal volume of acetone, chilled and filtered, and the solid washed with acetone and with diethyl ether to produce, after drying, 10.0 g of tan powder. The first crop of material was used in Part B. Pfrrt B

Preparation of the Merocyanine Dye A solution of 1.6 g of

prepared from the condensation of the disubstituted thiobarbituric acid with 1,3,3-trimethoxy—1-propene in 150 ml of hot acetonitrile was treated with 1.6 g of the inner salt from Part A, then dropwise with a solution of 0.70 g of triethylamine in acetonitrile. The deep blue solution was cooled to crystallize the dye, the crystals were collected by filtration, washed with acetonitrile, with acetone, and with diethyl ether, and dried to yield 3.1 g of crude material. The crude product was taken up in about 300 ml of hot ethanol and chilled overnight in an ice box, collected and dried to produce 2.1 g of dye having a λ-max in ethanol of 610 nm, an extinction coefficient ε = 16.4 X 10 and a solution of

1.644 mg in 232.0 ml of ethanol had an optical density of 1.622. The UV visible spectrum was consistent with the assigned structure.

Example 8

Preparation of

Part A

Preparation of

A mixture of 20 g of 2-methylnaphth[l,2-d]- thiazole and 13 g of propane sultone (available from Aldrich Chemical Co. and Eastman Kodak Co., respec¬ tively) was melted and immersed in an oil bath at 160-180^βC for about 15 hours. The mixture was cooled, rinsed with acetone, and the solid lump remaining dissolved in about 200 ml of boiling water. The mixture was filtered hot from the melted starting material and about 500 ml of acetone was added to the hot filtrate with stirring to precipi- tate the product. The solid was collected by filtration and dried to yield 24 g of off-white powder. Part B

Prepartion of the Merocyanine Dye A mixture of 1.6 g of the inner salt prepared in Part A and 1.62 g of

prepared from the condensation of the disubstituted thiobarbituric acid with 1,3,3—trimethoxy—1— ropene, and 300 ml of ethanol was treated with 0.75 g of triethylamine, the mixture was boiled for about 5 minutes, cooled, seeded with crystals generated from a sample in a test tube, chilled in an ice box, and the solid collected on a filter, washed with acetone, then with diethyl ether, and dried to yield 2.4 g. Recrystallization from ethanol produced 1.97 g. The spectrum had a small peak at 700 nm which was removed by recrystallizing three more times from minimum amounts of fresh ethanol. The final yield of material having a clear spectrum was 590 mg.

The dye, having a calculated molecular weight of 715.00, had a λ-max in ethanol at 613 nm,

4 and an extinction coefficient ε = 15.1 X 10 .

The UV visible spectrum was consistent with the assigned structure.

Example 9 When cultured F4-6 erythroleukemia cells, spleen, or marrow cells from diseased animals, cell—free extracts of cultured cells, spleen cells, or marrow cells, or cell—free supernatants of F—6 cultures were injected into healthy B6D2F1 mice, the spleen weights increased from about 60-70 mg to about 1500 mg within days. The animals became polycythemic and, eventually, died. When cell suspensions, cell-free extracts, or culture supernatants were photosensitized and exposed to light prior to injection, spleen weights remained normal, hematocrits remained normal, and the animals survived. Normal pluripotent hematopoietic stem cells (as determined by the ability of photosensitized marrow cells to rescue lethally irradiated syngeneic hosts) were spared by the photosensitization treatment. Virus preparations that were exposed to dye or light alone caused splenomegaly, polycythemia, and death. A series of experiments thus showed that the compounds of

Examples 1-4 with photolysis inactivates free Friend virus, intracellular Friend virus, and Friend virus-infected cells.

The result of the experiments with treated and untreated mice with (30 minutes at 70 Watts/m ) and without (ambient daylight only) light treatment are shown in spleen weights in Table I below.

TABLE I

Spleen Compound Light Weight (mg) Normal Spleen

(no virus) 59.6 Spleen With Virus (no compound) Daylight 1460 Example 1 Daylight 1484 Example 1 70 Watts/m² for 30 minutes 56.8

Example 2 Daylight 1332 Example 2 70 Watts/m² for 30 minutes 53.8

Example 3 Daylight 1488 Example 3 70 Watts/m² for 30 minutes 64.6

Example 4 Daylight 363.8 Example 4 70 Watts/m² for 30 minutes 67.4

Example 6 Daylight 1372 Example 6 70 Watts/m² for 30 minutes 68.2 Example 7 Daylight 1470 Example 7 70 Watts/m² for 30 minutes 61.2

It can be seen from the above data that light treatment with the compounds of this invention effectively inactivated the virus cells as evidenced by the resulting spleen weight after treatment.

Claims

WHAT IS CLAIMED IS

1. A compound having the following formula:

10 wherein :

X is selected for the group consisting of 0, Se and S

,c R_]^ and R₂ independently are H, alkyl, alkoxy, or carbocyclic aryl, with the stipulation that if X=S or 0, R, and R₂ are selected independently from a group consisting essentially of alkyl, alkoxy or carbocyclic aryl; _Q R-, and R_g are H and any of R, and R-,, R, and R-,, and R₂ and Rg can together comprise the atoms necessary to form a fused 6-membered carbocyclic aromatic ring on the benzene radical to which they ₅ are attached;

R_e and R, are independently selected from among the group essentially consisting of alkyl and benzyl of from 1-18 carbon atoms provided that the sum of the carbon atoms in R_ς and R_& is at _Q least 8;

R₉ is an alkylene group of 2-9 nuclear carbon atoms and CONH-groups; and Z⁺ is a cation.

2. The compound of claim 1 wherein one of ₅ R, and R,, R^, and R₂ or R₂ and R_g together comprise the atoms necessary to form a fused 6—membered carbocyclic aromatic ring on the benzene ring to which they are attached.

3. A compound selected from those having the formula:

and