BACKGROUND OF THE INVENTION

The present invention relates to the treatment of glaucoma and ocular hypertension. In particular, the present invention relates to the use of cloprostenol and fluprostenol analogues for the treatment of glaucoma and ocular hypertension.

Cloprostenol and fluprostenol, both known compounds, are synthetic analogues of PGF.sub.2.alpha., a naturally-occurring F-series prostaglandin (PG). Structures for PGF.sub.2.alpha. (I), cloprostenol (II), and fluprostenol (III), are shown below: ##STR1##

The chemical name for cloprostenol is 16-(3-chlorophenoxy)-17,18,19,20-tetranor PGF.sub.2.alpha.. Monograph No. 2397 (page 375) of The Merck Index, 11th Edition (1989) is incorporated herein by reference to the extent that it describes the preparation and known pharmacological profiles of cloprostenol. Fluprostenol has the chemical name 16-(3-trifluoromethylphenoxy)-17,18,19,20-tetranor PGF.sub.2.alpha.. Monograph No. 4121 (pages 656-657) of The Merck Index, 11th Edition (1989) is incorporated herein by reference to the extent that it describes the preparation and known pharmacological profiles of fluprostenol. Cloprostenol and fluprostenol are 16-aryloxy PGs and, in addition to the substituted aromatic ring, differ from the natural product PGF.sub.2.alpha., in that an oxygen atom is embedded within the lower (omega) chain. This oxygen interruption forms an ether functionality.

Naturally-occurring prostaglandins are known to lower intraocular pressure (IOP) after topical ocular instillation, but generally cause inflammation, as well as surface irritation characterized by conjunctival hyperemia and edema. Many synthetic prostaglandins have been observed to lower intraocular pressure, but such compounds also produce the aforementioned side effects which severely restrict clinical utility.

SUMMARY OF THE INVENTION

It has now been unexpectedly found that certain novel cloprostenol and fluprostenol analogues are useful in treating glaucoma and ocular hypertension. In particular, topical application of ophthalmic compositions comprising these novel cloprostenol and fluprostenol analogues result in significant IOP reduction.

DETAILED DESCRIPTION OF THE INVENTION

The compounds useful in the present invention have the following general formula: ##STR2## wherein: R.sub.1 =H; C.sub.1 -C.sub.12 straight-chain or branched alkyl; C.sub.1 -C.sub.12 straight-chain or branched acyl; C.sub.3 -C.sub.8 cycloalkyl; or a cationic salt moiety;

R.sub.2, R.sub.3 =H, or C.sub.1 -C.sub.5 straight-chain or branched alkyl; or R.sub.2 and R.sub.3 taken together may represent O;

X=O, S, or CH.sub.2 ;

represents any combination of a single bond, or a cis or trans double bond for the alpha (upper) chain; and a single bond or trans double bond for the omega (lower) chain;

R.sub.9 =H, C.sub.1 -C.sub.10 straight-chain or branched alkyl, or C.sub.1 -C.sub.10 straight-chain or branched acyl;

R.sub.11 =H, C.sub.1 -C.sub.10 straight-chain or branched alkyl, or C.sub.1 -C.sub.10 straight-chain or branched acyl;

Y=O; or H and OR.sub.15 in either configuration wherein R.sub.15 =H. C.sub.1 -C.sub.10 straight-chain or branched alkyl, or C.sub.1 -C.sub.10 straight-chain or branched acyl; and

Z=Cl or CF.sub.3 ;

with the proviso that when R.sub.2 and R.sub.3 taken together represent O, then R.sub.1 .noteq.C.sub.1 -C.sub.12 straight-chain or branched acyl; and when R.sub.2 =R.sub.3 =H, then R.sub.1 .noteq.a cationic salt moiety.

As used herein, the term "cationic salt moiety" includes alkali and alkaline earth metal salts as well as ammonium salts.

Preferred compounds include the 3-oxa form of cloprostenol isopropyl ester (Table, 1, compound 5), 13,14-dihydrofluprostenol isopropyl ester (compound 6), cloprostenol-1-ol (compound 7), and 13,14-dihydrocloprostenol-1-ol pivaloate (compound 8).

The compounds of formula (IV) are useful in lowering intraocular pressure and thus are useful in the treatment of glaucoma. The preferred route of administration is topical. The dosage range for topical administration is generally between about 0.01 and about 1000 micrograms per eye (.mu.g/eye), preferably between about 0.1 and about 100 .mu.g/eye, and most preferably between about 1 and 10 .mu.g/eye. The compounds of the present invention can be administered as solutions, suspensions, or emulsions (dispersions) in a suitable ophthalmic vehicle.

In forming compositions for topical administration, the compounds of the present invention are generally formulated as between about 0.00003 to about 3 percent by weight (wt %) solutions in water at a pH between 4.5 to 8.0. The compounds are preferably formulated as between about 0.0003 to about 0.3 wt % and, most preferably, between about 0.003 and about 0.03 wt %. While the precise regimen is left to the discretion of the clinician, it is recommended that the resulting solution be topically applied by placing one drop in each eye one or two times a day.

Other ingredients which may be desirable to use in the ophthalmic preparations of the present invention include preservatives, co-solvents and viscosity building agents.

Antimicrobial Preservatives:

Ophthalmic products are typically packaged in multidose form, which generally require the addition of preservatives to prevent microbial contamination during use. Suitable preservatives include: benzalkonium chloride, thimerosal, chlorobutanol, methyl paraben, propyl paraben, phenylethyl alcohol, edetate disodium, sorbic acid, ONAMER M.RTM., or other agents known to those skilled in the art. Such preservatives are typically employed at a concentration between about 0.001% and about 1.0% by weight.

Co-Solvents:

Prostaglandins, and particularly ester derivatives, typically have limited solubility in water and therefore may require a surfactant or other appropriate co-solvent in the composition. Such co-solvents include: Polysorbate 20, 60 and 80; Pluronic F-68, F-84 and P-103; Tyloxapol.RTM.; Cremophor.RTM. EL; sodium dodecyl sulfate; glycerol; PEG 400; propylene glycol; cyclodextrins; or other agents known to those skilled in the art. Such co-solvents are typically employed at a concentration between about 0.01% and about 2% by weight.

Viscosity Agents:

Viscosity greater than that of simple aqueous solutions may be desirable to increase ocular absorption of the active compound, to decrease variability in dispensing the formulations, to decrease physical separation of components of a suspension or emulsion of formulation and/or otherwise to improve the ophthalmic formulation. Such viscosity building agents include, for example, polyvinyl alcohol, polyvinyl pyrrolidone, methyl cellulose, hydroxy propyl methylcellulose, hydroxyethyl cellulose, carboxymethyl cellulose, hydroxy propyl cellulose or other agents known to those skilled in the art. Such agents are typically employed at a concentration between about 0.01% and about 2% by weight.

The following Examples 1-4 describe the synthesis of compounds 5-8 (Table 1). These syntheses are representative in nature and are not intended to be limiting. Other compounds of formula (IV) may be prepared using analogous techniques known to those skilled in the art.

                                      TABLE 1
    __________________________________________________________________________
    COMPOUND NAME   COMPOUND STRUCTURE
    __________________________________________________________________________
    5 3-oxacloprostenol isopropyl ester
                     ##STR3##
    6 13,14-dihydrofluprostenol isopropyl ester
                     ##STR4##
    7 cloprostenol-1-ol
                     ##STR5##
    8 13,14-dihydrocloprostenol-1-ol pivaloate
                     ##STR6##
    __________________________________________________________________________

A mixture of 1.2 g (3.2 mmol) of diol 25 (for synthesis of diol 25, see U.S. Pat. No. 4,321,275) and 0.05 g of 10% (wt/wt) Pd/C in 20 mL of methanol was hydrogenated at 30 psi for 1.5 hours. After filtration through a short pad of Celite.RTM. concentration afforded 1.2 g (100%)of 26 as a colorless oil. .sup.1 H NMR (CDCl.sub.3) .delta. 7.44 (m, 2 H), 7.12 (m, 2 H), 4.95 (dt, 1 H), 4.15-3.80 (m, 4 H), 2.82 (dd, J=10.8, 1 H), 2.55 (m, 2 H), 2.3 (m, 1 H), 2.1-1.3 (m, 6 H).

B: (3aR, 4R, 5R, 6aS)-5-(Tetrahydropyran-2-yloxy)-4-›(3R)-4-(3-trifluoromethylphenoxy)-3-(t etrahydropyran-2-yloxy)-1-butyl!-hexahydro-2H-cyclopenta›b!furan-2-one (27)

A mixture of 1.2 g (3.2 mmol) of diol 26 and 0.05 g of ptoluenesulfonic acid monohydrate in 100 mL of CH.sub.2 Cl.sub.2 at 0.degree. C. was treated with 3,4-dihydro-2H-pyran (1.1 ml, 12 mmol) and the solution was stirred for 2 h at 0.degree. C. After pouring into saturated NaHCO.sub.3, phases were separated and the organic layer was dried over MgSO.sub.4, filtered, concentrated, and purified by chromatography on silica gel (1/1, hexanes/EtOAc) to afford 1.1 g of 27 as a clear, colorless oil. .sup.1 H NMR (CDCl.sub.3) .delta. 8.04 (dd, J=7.0, 1.6, 1 H), 7.44 (m, 2 H), 7.12 (m, 1 H), 4.95 (dt, 1 H), 4.8 (m, 1 H), 4.7 (m, 2 H), 4.15-3.80 (m, 4 H), 3.5 (m, 2 H), 2.82 (dd, J=10.8,1 H), 2.55 (m, 2 H), 2.3 (m, 1 H), 2.1-1.3 (m, 6 H).

C: (5Z)-(9S, 11R, 15R)-11,15-Bis(tetrahydropyran-2-yloxy)-9-hydroxy-17,18,19,20-tetranor-16- (3-trifluoromethylphenoxy)-5-prostenoic Acid Isopropyl Ester (31)

To a solution of 2.1 g (3.9 mmol) of 27 in 100 mL of THF at -78.degree. C. was added 3.9 mL (5.8 mmol) of a 1.5M solution of diisobutyaluminum hydride in toluene. The solution was stirred for 2 h, then quenched by the sequential addition of 0.4 mL of isopropanol at -78.degree. C. followed by 0.4 mL of water at 23.degree. C. Volatiles were removed under reduced pressure and the aqueous solution was extracted with Et.sub.2 O/EtOAc (1/1). Organic extracts were dried over MgSO.sub.4, filtered, and concentrated to furnish 1.9 g of lactol 28.

To a 250 mL 3-necked round bottom flask equipped with a mechanical stirrer and a thermometer were added anhydrous DMSO (100 mL) and NaH (80% dispersion in mineral oil; 0.48 g, 16 mmol). The mixture was heated to 75.degree. C. (internal) for 30 min, after which it was allowed to cool to room temperature for 1 h. Phosphonium bromide 29 (3.5 g, 8 mmol) was then added. After stirring for 30 minutes, 1.9 g (3.5 mmol) of lactol 28 in 50 mL of DMSO was added, and the resulting solution was heated to 50.degree. C. for 2 h and then brought to room temperature for 16 h. The solution was poured into 100 mL of water and approximately 2 mL of 50% NaOH added. The aqueous phase was extracted with ether (3.times.100 mL), then made acidic (pH=5.5) by the addition of a 10% citric acid solution, and extracted with EtO/hexanes, 2/1 (3.times.100 mL). The combined organic extracts were dried over MgSO.sub.4, filtered, and concentrated to afford 1.9 g of 30 as a colorless oil.

To 1.9 g of carboxylic acid 30 dissolved in 10 mL acetone was added 0.95 g (6.0 mmol) of DBU and 1.0 g (6.1 mmol) of isopropyl iodide at 23.degree. C. After 16 h, the solution was poured into 100 mL of water and extracted with 100 mL of EtOAc. The organic extract was dried over MgSO.sub.4, filtered, concentrated, and purified by silica gel chromatography (3/2, hexanes/EtOAc) to afford 1.9 g of isopropyl ester 31 as a colorless oil. .sup.1 H NMR (CDCl.sub.3) .delta. 7.44 (t, 1 H), 7.12 (d, 1 H), 7.12 (dd, 2 H), 5.5-5.3 (m, 2 H), 4.99 (heptet, 1 H), 4.15-3.80 (m, 4 H), 2.82 (dd, J=10.8, 1 H), 2.55 (m, 2 H), 2.3 (m, 1 H), 2.1-1.3 (m, 24 H), 1.23 (s, 3 H), 1.20 (s, 3 H).

D: (5Z)-(9S, 11R, 15R)-17,18,19,20-Tetranor-16-(3-trifluoromethylphenoxy)-9,11,15-trihydroxy -5-prostenoic Acid Isopropyl Ester (6)

Ester 31 (1.9 g, 2.8 mmol) was dissolved in 14 mL of a mixture of AcOH/THF/H.sub.2 O (4/2/1) and the solution was heated to 50.degree. C. for 1 h, allowed to cool to 23.degree. C., poured into a saturated solution of NaHCO.sub.3, and extracted with Et.sub.2 O (2.times.100 mL) and EtOAc (100 mL). The combined organic extracts were dried over MgSO.sub.4, filtered, concentrated, and purified by silica gel chromatography (1/1, hexanes/EtOAc) to furnish 0.5 g of triol 6 as a clear, colorless oil. .sup.1 H NMR (CDCl.sub.3) .delta. 7.44 (t, J=7.8,1 H), 7.12 (dd, J=7.8, 2.0, 1 H), 7.12 (ddd, J=15.6, 7.2, 2.0, 2 H), 5.5-5.3 (m, 2 H), 4.99 (heptet, J=6.3, 1 H), 4.15-3.80 (m, 4 H), 3.2 (d, 1 H), 2.95 (s, 1 H), 2.82 (dd, J=10.8, 1 H), 2.75 (d, J=5.9, 1 H), 2.55 (m, 2 H), 2.3 (m, 1 H), 2.1-1.3 (m, 24 H), 1.23 (s, 3 H), 1.20 (s, 3 H). .sup.13 C NMR (CDCl.sub.3) .delta. 173.5, 158.7, 132.1, 131.5,130.0, 129.5, 129.2, 123.3, 120.8, 117.7, 117.6, 111.4, 111.4, 78.6, 74.4, 72.4, 69.9, 67.6, 52.6, 51.7, 42.5, 34.0, 31.5, 29.4, 26.8, 26.6, 24.9, 21.7.

EXAMPLE 3: Synthesis of Cloprostenol-1-ol (7) ##STR9##

A: (5Z, 13E)-(9S, 11R, 15R)-11,15-Bis(tetrahydropyran-2-yloxy)-16-(3chlorophenoxy)-9-hydroxy-17,1 8,19,20-tetranor-5,13-prostadienoic Acid Isopropyl Ester (34)

A 1.5M solution of diisobutylaluminum hydride in toluene (10 mL, 15 mmol) was added dropwise to a solution of 5.8 g (11.4 mmol) of lactone 16 in 55 mL of THF at -78.degree. C. After 1 h, 10 mL of methanol was added dropwise, and the mixture was stirred for 10 min at -78.degree. C. before being warmed to room temperature. The mixture was then poured into 100 mL of a 1/1 solution of saturated aqueous potassium sodium tartrate/ethyl acetate and stirred. After separating layers, the aqueous phase was extracted with ethyl acetate (2.times.40 mL). Combined organic layers were dried over MgSO.sub.4, filtered, concentrated, and purified by silica gel chromatography (3/2, ethyl acetate/hexane), to afford 4.4 g (76%) of lactol 33, which was used immediately in the next step.

A 1M solution of potassium t-butoxide in THF (50.0 ml) was added dropwise to 12.1 g (27.3 mmol) of phosphonium salt 29 in 100 mL of THF at 0.degree. C. After 30 min, a solution of 4.4 g (8.6 mmol) of lactol 33 in 20 mL of THF was added dropwise, and the mixture was stirred at room temperature overnight. The solution was then poured into 150 mL of a 1/1 mixture of ethyl acetate/saturated NH.sub.4 Cl. Layers were separated and the aqueous layer was extracted with ethyl acetate (2.times.100 mL). Combined organic layers were dried over MgSO.sub.4, filtered, concentrated, and the residue was redissolved in 80 mL of acetone. To this was added 6.5 g (45 mmol) of DBU followed by 7.3 g (43 mmol) of isopropyl iodide. After stirring overnight, the reaction was poured into 100 mL of a 1/1 mixture of ethyl acetate/saturated NH.sub.4 Cl. Layers were then separated and the aqueous phase was further extracted with ethyl acetate (2.times.100 mL). The combined organic layers were dried over MgSO.sub.4, filtered, concentrated, and purified by silica gel chromatography (40% ethyl acetate in hexane) to afford 2.92 g (53% from lactone 16) of ester 34.

B: (5Z, 13E)-(9S, 11R, 15R)-16-(3-Chlorophenoxy)-17,18,19,20-tetranor-9,11,15-trihydroxy-5,13-pro stadienol (7)

A solution of 500 mg (0.79 mmol) of 34 in 10 mL of THF was added dropwise to 61 mg (1.60 mmol) of lithium aluminum hydride in 20 mL of THF at 0.degree. C. After 40 min, the reaction was carefully poured into 15 mL of saturated NH.sub.4 Cl, and the mixture was then extracted with ethyl acetate (3.times.40 mL). Combined organic layers were dried over MgSO4 , filtered, and concentrated to afford 500 mg of crude 35.

To a solution of 500 mg of 35 in 20 mL of methanol was added 0.5 mL of 2M HCl. After 1 h, the reaction was quenched with 20 mL of saturated NaHCO.sub.3 and the mixture was extracted with ethyl acetate (4.times.30 mL). The combined organic layers were dried over MgSO.sub.4, filtered, and concentrated. Silica gel s chromatography (EtOAc) provided 101 mg (31% from 34) of 7. .sup.13 C NMR (CDCl.sub.3) .delta. 159.27 (C), 135.44 (CH), 134.82 (C), 130.64 (CH), 130.26 (CH), 128.23 (CH), 121.25 (CH), 115.07 (CH), 113.08 (CH), 77.35 (CH), 72.35 (CH), 71.90 (CH.sub.2), 70.89 (CH), 62.22 (CH.sub.2), 55.40 (CH), 49.87 (CH), 42.79 (CH.sub.2), 31.83 (CH.sub.2), 26.77 (CH.sub.2), 25.60 (CH.sub.2), 25.33 (CH.sub.2). Cl MS m/z calcd for C.sub.22 H.sub.32 O.sub.5 Cl.sub.1 (MH.sup.+) 411.1938, found 411.1938.

EXAMPLE 4: Synthesis of 13,14-Dihydrocloprostenol-1-ol Pivaloate (8) ##STR10##

A: (3aR, 4R, 5R, 6aS)-4-›(3R)-4-(3-Chlorophenoxy)-3-hydroxybutyl!-5-hydroxy-hexahydro-2H-cy clopenta›b!furan-2-one (37):

A mixture of 2.4 g (5.4 mmol) of 14 and 250 mg of 10% (wt/wt) Pd/C in 35 mL of ethyl acetate was hydrogenated at 40 psi for 1 h. After filtration through a short pad of Celite.RTM., the filtrate was evaporated down to 2.3 g (100%) of hydrogenated product 36.

The crude benzoate 36 was dissolved in 25 mL of methanol, and 610 mg (4.4 mmol) of K.sub.2 CO.sub.3 was added. After 3.5 h, the mixture was poured into 100 mL of water/ethyl acetate (1/1). Layers were separated, and the aqueous phase was further extracted with ethyl acetate (2.times.50 mL). The combined organic layers were dried over MgSO.sub.4, filtered and concentrated. Silica gel chromatography (EtoAc) provided 1.50 g (82%) of 37 as a white solid, m.p.=102.0.degree.-103.5.degree. C. .sup.1 H NMR .delta. 7.22 (t, J=8.2 Hz, 1 H), 7.0-6.94 (m, 1 H), 6.91-6.88 (t, J=2.1 Hz, 1 H), 6.83-6.77 (m, 1 H), 4.97 (dt, J=3.0, 8.3 Hz, 1 H), 4.12-3.91 (m, 3 H), 3.82 (dd, J=7.4, 9.0 Hz, 1 H), 2.85 (dd, J=8.0, 16.5 Hz, 1 H), 2.6-1.4 (m, 11 H).

B: (3aR, 4R, 5R, 6aS)-4-›(3R)-4-(3-Chlorophenoxy)-3-(tetrahydropyran-2-yloxy)bulyl!-5-(tetr ahydropyran-2-yloxy)-hexahydro-2H-cyclogenta›b!furan-2-one (38)

Diol 37 (3.4 g, 10 mmol) and 2.2 g (26 mmol) of 3,4-dihydro-2H-pyran were dissolved in 80 mL of CH.sub.2 Cl.sub.2, and 240 mg (1.3 mmol) of p-toluenesulfonic acid monohydrate was added at 0.degree. C. After 1 h, the reaction was poured into 50 mL of saturated NaHCO.sub.3 and the mixture was extracted with CH.sub.2 Cl.sub.2 (3.times.40 mL). The combined organic layers were dried over MgSO.sub.4, filtered, concentrated, and the residue was chromatographed on silica gel (hexane/ethyl acetate, 1/1) to afford 4.5 g (87%) of bis-THP ether 38.

C: (5Z)-(9S, 11R, 15R)-11,15-Bis(tetrahydropyran-2-yloxy)-16-(3-chlorophenoxy)-9-hydroxy-17, 18,19,20-tetranor-5-prostenoic Acid IsoproDVl Ester (41)

A 1.5M solution of diisobutylaluminum hydride in toluene (1.8 mL, 2.7 mmol) was added to the solution 1.05 g (2.06 mmol) of 38 in 10 mL of THF at -78.degree. C. After 1 h, 4 mL of methanol was added and the mixture was warmed to 25.degree. C., then poured into 40 mL of ethyl acetate/saturated aqueous potassium sodium tartrate (1/1). Layers were separated and the aqueous phase was further extracted with ethyl acetate (3.times.30 mL). The combined organic layers were then dried over MgSO.sub.4, filtered, concentrated, and the residue was chromatographed on silica gel (ethyl acetate) to afford 740 mg (70%) of lactol 39.

A 1.5M solution of potassium t-butoxide in THF (8.6 mL, 8.6 mmol) was added dropwise to a mixture of 15 mL of THF and 1.92 g (4.33 mmol) of phosphonium salt 29 at 0.degree. C. After stirring for 1 h, a solution of 740 mg (1.45 mmol) of lactol 39 in 5 mL of THF was added dropwise, and the reaction was allowed to warm to 25.degree. C. overnight. The mixture was then poured into 100 mL of ethyl acetate/saturated NH.sub.4 Cl (1/1). Layers were separated, and the aqueous phase was further extracted with ethyl acetate (2.times.70 mL). Combined organic layers were dried over MgSO.sub.4, filtered, and concentrated to afford 1.6 g of crude acid 40.

Crude acid 40 (1.6 g) was dissolved in 11 mL of acetone and cooled to 0.degree. C., then 850 mg (5.6 mmol) of DBU was added dropwise to the solution. The resulting mixture was stirred for 15 min at 0.degree. C. and 30 min at 25.degree. C., after which 850 mg (5.0 mmol) of isopropyl iodide was added. The reaction was stirred overnight and poured into 100 mL of ethyl acetate/saturated NH.sub.4 Cl (1/1). Layers were separated, and the aqueous phase was further extracted with ethyl acetate (2.times.50 mL). Combined organic layers were dried over MgSO.sub.4, filtered and concentrated. The resulting residue was purified by silica gel chromatography (ethyl acetate/hexanes, 3/2) to afford 560 mg (61 % from lactol 39) of isopropyl ester 41.

D: (5Z)-(9S, 11R, 15R)-16-(3-Chlorophenoxy)-17,18,19,20-tetranor-9,11,15-trihydroxy-5-proste nol Pivaloate (8)

A solution of 400 mg (0.63 mmol) of 41 in 5 mL of THF was added dropwise to a suspension of 35 mg (0.92 mmol) of lithium aluminum hydride in 5 mL of THF at 0.degree. C. After 2 h, the reaction was poured into 50 mL of a 1/1 mixture of ethyl acetate/saturated NaHCO.sub.3. The layers were then separated, and the aqueous phase was extracted with ethyl acetate (2.times.2 mL). Combined organic layers were dried over MgSO.sub.41 filtered, and concentrated. The resulting residue was purified by silica gel chromatography (ethyl acetate) to afford 350 mg (95%) of diol 42.

Pivaloyl chloride (90 mg, 0.75 mmol) was added to a mixture of 350 mg (0.60 mmol) of 42, 60 mg (0.76 mmol) of pyridine, 22 mg (0.18 mmol) of 4(dimethylamino)pyridine, and 7 mL of CH.sub.2 Cl.sub.2. After 1.5 h, the mixture was poured into 30 mL of saturated NH.sub.4 Cl/ethyl acetate (1/1). Layers were then separated and the aqueous phase was extracted with ethyl acetate (2.times.20 mL). The combined organic layers were dried over MgSO.sub.4, filtered, concentrated, and purified by silica gel chromatography (ethyl acetate/hexane, 3/2) to afford 370 mg (93%) of pivaloate 43.

Water (approximately 10 drops) and concentrated HCl (approximately 3 drops) were added to a solution of 370 mg (0.56 mmol) of 43 in 5 mL of methanol. After stirring overnight, the reaction was quenched by the addition of 20 mL of saturated NaHCO.sub.3, and the mixture was extracted with ethyl acetate (3.times.20 mL). The combined organic layers were dried over MgSO.sub.4, filtered, and concentrated. The residue was chromatographed on silica gel (ethyl acetate/hexane, 3/2), to afford 165 mg (59%) of triol 8. .sup.13 C NMR (CDCl.sub.3) .delta. 178.77 (C), 159.27 (C), 134.80 (C), 130.20 (CH), 128.62 (CH), 121.19 (CH), 114.97 (CH), 112.97 (CH), 78.50 (CH), 74.46 (CH), 72.31 (CH.sub.2), 69.86 (CH), 64.16 (CH.sub.2), 52.53 (CH), 51.67 (CH), 42.50 (CH.sub.2), 31.51 (CH.sub.2), 29.40 (OH.sub.2), 28.10 (OH.sub.2), 27.12 (OH.sub.3), 26.77 (CH.sub.2), 26.65 (CH.sub.2), 25.77 (CH.sub.2). Cl MS, m/z calcd for C.sub.27 H.sub.41 O.sub.6 Cl.sub.1 (MH.sup.+), 497.2670, found 497.2656

EXAMPLE 5

PGF.sub.2.alpha. analogues are known to contract the iris sphincter of cats and this assay is a generally accepted reference for activity. For this reason, the pupil diameter of cats may be used to define the activity of PGF.sub.2.alpha. analogues and, as demonstrated by Stjernschantz and Resul (Drugs Future, 17:691-704 (1992)), predict the IOP-lowering potency.

Compounds of the present invention were therefore screened for pupillary constriction in the cat. Data for compounds 6, 7, and 8 are presented in Table 2, below. The response is quantitated as Area.sub.1-5 values (area under the pupil diameter versus time curve from 1-5 hours), and the equivalent response dose (ED.sub.5) is estimated from its dose response relationship.

                  TABLE 2
    ______________________________________
    Cat Pupil Diameter Response
    Compound           ED.sub.5 (.mu.g)
    ______________________________________
    PGF.sub.2.alpha. Isopropyl Ester
                       0.02
    Cloprostenol Isopropyl Ester
                       0.01
    6                  0.2
    7                  0.02
    8                  0.06
    ______________________________________

                  TABLE 3
    ______________________________________
    Monkey IOP Response
    Compound         ED.sub.20 (.mu.g)
    ______________________________________
    PGF.sub.2.alpha. Isopropyl Ester
                     0.4
    6                0.3
    ______________________________________

    ______________________________________
    FORMULATION 1
    Ingredient         Amount (wt %)
    ______________________________________
    Compound 5 (Table 1)
                        0.002
    Dextran 70         0.1
    Hydroxypropyl methylcellulose
                       0.3
    Sodium chloride    0.77
    Potassium chloride 0.12
    Disodium EDTA      0.05
    Benzalkonium chloride
                       0.01
    HCl and/or NaOH    pH 7.2-7.5
    Purified water     q.s. to 100%
    ______________________________________


______________________________________
    FORMULATION 2
    Ingredient         Amount (wt %)
    ______________________________________
    Compound 6 (Table 1)
                       0.01
    Monobasic sodium phosphate
                       0.05
    Dibasic sodium phosphate
                       0.15
    (anhydrous)
    Sodium chloride    0.75
    Disodium EDTA      0.01
    Benzalkonium chloride
                       0.02
    Polysorbate 80     0.15
    HCl and/or NaOH    pH 7.3-7.4
    Purified water     q.s.to 100%
    ______________________________________


______________________________________
    FORMULATION 3
    Ingredient         Amount (wt %)
    ______________________________________
    Compound 7 (Table 1)
                        0.001
    Dextran 70         0.1
    Hydroxypropyl methylcellulose
                       0.5
    Monobasic sodium phosphate
                       0.05
    Dibasic sodium phosphate
                       0.15
    (anhydrous)
    Sodium chloride    0.75
    Disodium EDTA      0.05
    Benzalkonium chloride
                       0.01
    NaOH and/or HCl    pH 7.3-7.4
    Purified water     q.s. to 100%
    ______________________________________


______________________________________
    FORMULATION 4
    Ingredient         Amount (wt %)
    ______________________________________
    Compound 8 (Table 1)
                        0.003
    Monobasic sodium phosphate
                       0.05
    Dibasic sodium phosphate
                       0.15
    (anhydrous)
    Sodium chloride    0.75
    Disodium EDTA      0.05
    Benzalkonium chloride
                       0.01
    HCl and/or NaOH    pH 7.3-7.4
    Purified water     q.s. to 100%
    ______________________________________