IL133871A - Prostaglandin derivatives devoid of side-effects for the treatment of glaucoma - Google Patents

Abstract

An ophthalmological composition for treating glaucoma or ocular hypertension without increased or with reduced melanogenesis side effect, comprising a therapeutically active and physiologically acceptable amount of a compound of the formula: wherein: the wavy bonds represent the a or b configuration, and the dashed bonds represent a single bond, a triple bond or a double bond in the cis or trans configuration; R is hydrogen, saturated or unsaturated alkyl, preferably C1-10 alkyl, cycloalkyl, preferably C3-8 cycloalkyl, aryl, arylalkyl, preferably aryl-C2-5 alkyl, or heteroaryl; R1 is a saturated or unsaturated alkyl group having 2-5 carbon atoms, optionally interrupted by heteroatoms selected from oxygen, sulfur and nitrogen, cycloalkyl, 2659 י" ב בתשרי התשס" ה - September 27, 2004 preferably C3-7 cycloalkyl, cycloalkenyl, preferably C3-7 cycloalkenyl, aryl or heteroaryl; X is C-OH or C=O; R2 is hydrogen, hydroxy, methyl, ethyl, methoxy or OCOR4, where R4 is a straight or branched chain saturated or unsaturated alkyl group, preferably C1-10 alkyl, especially C1-6 alkyl, or a cycloalkyl, preferably, C3-8 cycloalkyl, or aryl group; R3 is a straight or branched chain saturated or unsaturated alkyl group, preferably having 3-8 carbon atoms, especially 3-5 carbon atoms, optionally interrupted by one or more heteroatoms selected from oxygen, sulfur and nitrogen, each carbon atom optionally being substituted with a substituent selected from C1-5 alkyl, hydroxy and carbonyl groups, hydroxy and carbonyl preferentially being attached to carbon 15 of the prostaglandin structure, and said alkyl group optionally containing a cycloalkyl, preferably C3-8 cycloalkyl, aryl or heteroaryl group, which may be mono- or independently multi-substituted with C1-3 alkyl, C1-3 alkoxy, hydroxy, nitro, trifluoromethyl or halogen; or a pharmaceutically acceptable salt or ester thereof, which is a selective agonist for EP1 prostanoid receptors, and an ophthalmologically compatible carrier.

Description

PROSTAGLANDIN DERIVATIVES DEVOID OF SIDE-EFFECTS FOR THE TREATMENT OF GLAUCOMA -5A- According to a first embodiment of the present invention there is provided an ophthalmological composition for treating glaucoma or ocular hypertension without increased or with reduced melanogenesis side effect, comprising a therapeutically active and physiologically acceptable amount of a compound of the general formula: wherein: the wavy bonds represent the or β configuration, and the dashed bonds represent a single bond, a triple bond or a double bond in the cis or trans configuration; R is hydrogen, saturated or unsaturated alkyl, preferably CMO alkyl, cycloalkyl, preferably C3-8 cycloalkyl, aryl, arylalkyl, preferably aryl-C2_5 alkyl, or heteroaryl; Rl is a saturated or unsaturated alkyl group having 2-5 carbon atoms, optionally interrupted by heteroatoms selected from oxygen, sulfur and nitrogen, cycloalkyl, preferably C3-7 cycloalkyl, cycloalkenyl, preferably C3-7 cycloalkenyl, aryl or heteroaryl; X is C-OH or C=0; R2 is hydrogen, hydroxy, methyl, ethyl, methoxy or OCOR4, where R4 is a straight or branched chain saturated or unsaturated alkyl group, preferably Cno alkyl, especially Ci_6 alkyl, or a cycloalkyl, preferably C3-8 cycloalkyl, or aryl group; R3 is a straight or branched chain saturated or unsaturated alkyl group, preferably having 3-8 carbon atoms, especially 3-5 carbon atoms, optionally interrupted by one or more heteroatoms selected from oxygen, sulfur and nitrogen, each carbon atom optionally being substituted with a substituent selected from C 1-5 alkyl, hydroxy and carbonyl groups, hydroxy and carbonyl preferentially being attached to carbon 15 of the prostaglandin structure, and said alkyl group optionally containing a cycloalkyl, preferably C3-8. -5B- cycloalkyl, aryl or heteroaryl group, which may be mono- or independently multi-substituted with Ci-3 alkyl, Ci-3 alkoxy, hydroxy, nitro, trifluoromethyl or halogen; or a pharmaceutically acceptable salt or ester thereof, which is a selective agonist for EPi prostanoid receptors, and an ophthalmologically compatible carrier.

According to a second embodiment of the present invention there is provided a method of treating glaucoma or ocular hypertension without increased or with reduced melanogenesis side effect, in a subject's eye, which method comprises contacting the surface of the eye with an effective intraocular pressure reducing amount of a therapeutically active and physiologically acceptable prostaglandin analogue which is a selective agonist for EPi prostanoid receptors, or a pharmaceutically acceptable salt or ester thereof.

According to a third embodiment of the present invention there is provided use of a prostaglandin analogue that is a selective agonist for EPi prostanoid receptors as defined in any one of claims 1 to 4 for the preparation of a medicament for treatment of glaucoma and ocular hypertension without increased or with reduced melanogenesis side-effect. 6 The specific prostaglandin analogues that we have used for exemplifying and proving this invention were PGF2p (1), PGF2p isopropyl ester (2), 17-phenyl-18,19,20-trinor-PGE2 (3), 17-phenyl-18,19,20-trinor-PGE2 isopropyl ester (4), 15(R,S)-16,16-trimethylene-PGE2 (5), 15(R,S)-16,16-trimethylene-PGE2 methyl ester (6), and 13,14-dihydro-17-(3-fluorophenyl)-18, 19, 20 trinor-PGE2-isopropyl ester (7). All these analogues are relatively selective EPi receptor agonists. The receptor profiles of the test compounds are presented in Table I.

Table I. Receptor profile of prostaglandin analogues tested (EC-50 values expressed as moles/1 in functional receptor assays).

Prostaglandin FP EPi EP2 EP3 DP/ΊΡ TP 1 5xl0-6 10'6 lo-5 >10 >w3 >103 3 10-7 2 l0'8 >i0A >\0A >10'4 2xl0"5 6xl0"9 2xl0'7 3xl0-8# >\0 >10" 7 6xl0-7 4xl0"8 5x10'5 io-6# >10-4 >10"4 # estimated based on difference in receptor assay between guinea pig vas deferens and chick ileum.

In one aspect, the invention relates to the use of selective prostaglandin EPi receptor agonists devoid of melanogenic effect for the treatment of glaucoma or ocular hypertension. The method for treating glaucoma or ocular hypertension comprises contacting the surface of the eye with an effective intraocular pressure reducing amount of a composition, containing an EPi selective prostaglandin as aforesaid, in order to reduce the intraocular pressure and to maintain said pressure at a reduced level. The composition usually contains about 0.1-100 g, especially 1-30 μξ per application of the active substance. The composition is applied topically on the eye 1- 3 times daily. 7 The prostaglandin derivative is mixed with an ophthalmologically compatible vehicle known per se. The vehicle which may be employed for preparing compositions of this invention comprises aqueous solutions, e.g. physiological saline, oil solutions, or ointments. The vehicle may furthermore contain ophthalmologically compatible preservatives such as e.g. benzalkonium chloride, surfactants, such as polysorbate 80, liposomes or polymers, for example methyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone and hyaluronic acid; these may be used for increasing the viscosity. Furthermore it is also possible to use soluble or insoluble drug inserts.

In another aspect, the invention relates to ophthalmological compositions for medical treatment of glaucoma or ocular hypertension which comprise an effective intraocular pressure reducing amount of a prostaglandin analogue which is a selective agonist of EPi receptors as defined above and an ophthalmologically compatible carrier. The effective amount usually comprises a dose of about 0.1-100 μg in about 10-50 μΐ of the composition. The compositions according to the present invention are clear improvements over the prior art prostaglandin compositions due to the selectivity of the active compound for EPI receptors compared to other prostaglandin receptors with the risk for pigmentation eliminated or at least substantially reduced.

In still another aspect, the invention relates to the use of the prostaglandin analogue for the preparation of a medicament for treatment of glaucoma and ocular hypertension.

Preferably, the prostaglandin analogue is derived from PGF or PGE type prostaglandins. Particularly, the prostaglandin analogue is a compound of the general formula: wherein: the wavy bonds represent the a or β configuration, and the dashed bonds represent a single bond, a triple bond or a double bond in the cis or trans configuration; R is hydrogen, saturated or unsaturated alkyl, preferably Q.io alkyl, cycloalkyl, preferably C3-8 cycloalkyl, aryl, arylalkyl, preferably aryl-C2-5 alkyl, or heteroaryl; Rl is a saturated or unsaturated alkyl group having 2-5 carbon atoms, optionally interrupted by heteroatoms selected from oxygen, sulfur and nitrogen, cycloalkyl, preferably C3-7 cycloalkyl, cycloalkenyl, preferably C3-7 cycloalkenyl, aryl or heteroaryl; X is C-OH or C=0; R2 is hydrogen, hydroxy, methyl, ethyl, methoxy or OCOR4, where R4 is a straight or branched chain saturated or unsaturated alkyl group, preferably Q.io alkyl, especially C|_6 alkyl, or a cycloalkyl, preferably C3.g cycloalkyl, or aryl group; R3 is a straight or branched chain saturated or unsaturated alkyl group, preferably having 3-8 carbon atoms, especially 3-5 carbon atoms, optionally interrupted by one or more heteroatoms selected from oxygen, sulfur and nitrogen, each carbon atom optionally being substituted with a substituent selected from Ci-s alkyl, hydroxy and carbonyl groups, hydroxy and carbonyl preferentially being attached to carbon 15 of the prostaglandin structure, and said alkyl group optionally containing a cycloalkyl, preferably C3.8 cycloalkyl, aryl or heteroaryl group, which may be mono- or independently multi-substituted with C|.3 alkyl, C1.3 alkoxy, hydroxy, nitro, trifluoromethyl or halogen; or a pharmaceutically acceptable salt or ester thereof.

Aryl is preferably substituted or unsubstituted phenyl. 9 Exemplary heteroaryl groups are thiophene, furan, thiazole, isothiazole, oxazole, isoxazole, pyridine, pyrazine, pyrimidine, pyridazine.

Aryl, heteroaryl and cycloalkyl may be mono- or independently di- or multi-substituted by C1.3 alkyl, C|-3 alkoxy, hydroxy, nitro, trifluoromethyl or halogen.

Unsaturated alkyl may contain one or more double and/or triple bonds.

Halogen is fluorine, chlorine, bromine or iodine, especially fluorine, chlorine or bromine.

The prostaglandins may be in epimeric mixtures as well as in the form of the individual epimers.

The invention is illustrated by means of the following non-limiting examples: Identification of prostaglandin receptors. The prostaglandin receptors were identified using the reversed transcriptase polymerase chain reaction (RT-PCR) technique. Specific primers were designed for the FP, EP|, EP2, EP3, and TP receptors. The primers used in the assays are presented in Table II. RT-PCR was performed on mRNA isolated from human iridial melanocytes in culture. The cultured cells were used for preparing mRNA. The RT-PCR mix was analysed on agarose gel and bands of expected size were cloned and sequenced. The deduced sequences were analysed for similarity to each prostaglandin receptor sequence.

Methods. Human iridial melanocytes were isolated and cultured according to Hu et al. (1993) and used in early passages. Cells were grown to confluence and harvested for the mRNA enrichment. mRNA was isolated using Dynals mRNA Direct System (Dynal A/S, Norway) according to the manufacturer's instructions. 100.000-200.000 human melanocyte cells were used in the enrichment. mRNA is covalently bound to an oligo-dT labeled Dynabead. Using reverse transcriptase the first strand cDNA is synthesized directly on the Dynabeads with the oligo-dT as a reverse transcriptase primer. The second strand cDNA is synthesized using a known 3' sequence primer from respective prostaglandin receptor, resulting in double stranded cDNA. The same set of Dynabeads was used for each receptor RT-PCR. Receptor specific primers were used for PCR amplifying DNA from Dynabead bound cDNA according to the manufacturer's instructions. For the FP and EP3 receptor reactions the PCR was performed in 50 μΐ final volume with 5% DMSO, 200 μΜ dNTPs and 20 pmoles of each primer. For the other receptors hot start with AmpliWax pellets (Perkin Elmer, USA) was used in a final volume of 75 μΐ with 5% DMSO, 200 μΜ dNTPs and 20 pmoles of each primer.

Table II. Prostaglandin receptor specific primers.

FP primers: Primary primers; CAC AAC CTG CCA GAC GGA AAA C and CCA GTC TTT GAT GTC TTC TGT G Secondary primers; CAG TAA TCT TCA TGA CAG TGG G and TTG TAG AAA CAC CAG GTC CTG G EP| primers: primary primers; TGT GGC ATG GCC GTG GAG and ACC AAC ACC AGC ATT GGG C secondary primers; CTG CAG GGA GGT AGA GCT C and GGC ACG TGG TGC TTC ATC G 1 1 EP2 primers: primary primers; CAA CCA TGC CTA TTT CTA CAG C and TCT CGC TCC AAA CTT GGC TG secondary primers; CTA CGT GGA CAA GCG ATT GGC and TGG TTG ACG AAC ACT CGC AC EP3 primers: primary primers; GGG ATC CAA GAT CTG GTT CAG and GCC TTC CCG ATC ACC ATG CTG secondary primers; CGC AAG AAG TCG TTC CTG CTG and CAC CAA GTC CCG GGC CAC TG TP primers: primary primers; CTG GTG ACC GGT ACC ATC GTG GTG T and GTA GAT CTA CTG CAG CCC GGA GCG C secondary primers; TCG CTA CAC CGT GCA ATA CC and GGC TGG AGG GAC AGC GAC The PCR mix from these reactions was analyzed on a 1% LMP agarose gel (BioRad Laboratories, USA). DNA fragments of the expected size were TA-cloned using a TA-cloning kit according to the manufacturer's instructions (Invitrogen Inc., USA), and sequenced on an Applied Biosystem Model 373A DNA sequencing system (Applied Biosystems Inc., USA) according to Applied Biosystems' protocol for their Taq Dye Dioxy Terminator cycle sequencing kit. The generated primary data were processed on a VAX computer using the sequence analysis programs from Genetics Computer Group Inc., Madison, USA (Devereux, J., et al., Nucleic Acids Research 12 (1): 387-395 (1984).

Results: In human iridial melanocytes based on our RT-PCR we could show an expression of FP, EP2 and EP3 receptors. However, we were not able to show the presence of the EPi and TP receptors (Table ΕΠ). As positive controls we amplified the expected EPj and TP fragments with the same primers from a human kidney 12 cDNA library. We enriched poly A mRNA from human iridial melanocytes isolated at two different times and performed the PCR reactions several times with identical result.

Table ΠΙ. RT-PCR (secondary PCR primers) of human iridial melanocyte mRNA using prostaglandin receptor specific primers (see Table II).

Gene Correct fragment size (bp) Sequence analysis Observed Expected FP + 489 Identity with FP EPi - 397 ■ - EP2 + 501 Identity with EP2 EP3 + 372 Identity with EP3 TP - 484 - ' SYNTHESIS OF PROSTAGLANDIN DERIVATIVES The structures of the end compounds prepared in the Examples are shown in Scheme 1 provided at the end of the description.

Example 1: PGF2p(compound 1) The title compound was purchased from Cayman Chemicals Company, Ann Arbor Michigan, USA.

Example 2: PGF2 isopropyl ester (compound 2) DBU (163.5 mg, 1.01 mmol) was added to a stirred solution of PGF2p (Cayman Chemicals) (60 mg, 0.169 mmol) in acetone (20 ml) at 0 °C. The mixture was allowed 13 to warm to room temperature, when isopropyl iodide (222.6 mg, 1.34 mmol) was added dropwise. After 48 h (TLC monitoring), the mixture was diluted with ethyl acetate (40 ml), washed with brine (30 ml), citric acid 3% (2x40 ml) and sodium hydrogen carbonate 5% (2x30 ml) and dried over anhydrous sodium sulfate. The solvent was removed in vacuo and the residue was chromatographed on silica gel using ethyl acetate : acetone 3: 1 as eluent. This afforded a colorless oil, yield 46 mg (68%). Ή NMR (CDC13) d 1.3 (d, 6H), 1.6-1.7 (dm, 4H), 2.0-2.2 (dm, 6H), 2.3 (t, 2H), 4.0-4.1 (m, 3H), 5.0 (sept, 1H), 5.5 (m, 2H), 5.6 (m, 2H). 13C NMR (CDCI3) d 135.9, 132.2, 130.5, 128.0, 75.3, 74.8, 72.85, 67.6, 56.23, 52.25, 51.59, 42.32, 37.35, 33.44, 31.74, 29.14, 26.66, 24.79, 22.6, 21.8, 14.03.

Example 3: 17-Phenyl- 18,19,20-trinor-PGE, (compound 3) The title compound was purchased from Cayman Chemicals Company, Ann Arbor Michigan, USA.

Example 4: 17-Phenyl-18,19,20-trinor-PGE2 isopropyl ester (compound 4) DBU (43.5 mg, 0.29 mmol) in acetonitrile (1 ml) was added dropwise to a stirred solution of compound 3 (22.1 mg, 0.057 mmol) in acetonitrile (3 ml) at 0 °C. The mixture was allowed to warm to room temperature whereupon isopropyl iodide (78.0 mg, 0.46 mmol) in acetonitrile (2 ml) was added dropwise. After being stirred for 12 h (TLC monitoring), the reaction mixture was quenched with water (8 ml), the mixture was extracted with ethyl acetate (2x50ml), and the extract was washed with brine (10 ml), citric acid 3% (10 ml), and finally sodium hydrogen carbonate 5% (10 ml). After drying with anhydrous sodium sulfate, the solvent was removed in vacuo and the residual oil was chromatographed on silica gel using ethyl acetate as eluent. This afforded 230 mg of the product (69%) of the title compound as a colorless oil: /?/= 0.516 (ethyl acetate : acetone : HO Ac 1 : 1 :0.02); Ή NMR (CDCI3) d 0.89 (m, 3H), 1.3 (d, 6H), 2.6-2.8 (m, 2H), 4.1 (m, 2H), 5.0 (m, 1H), 5.3-5.7 (dm, 4H), 7.2 (m, 5H). 13C NMR (CDCI3) d 10.9, 13.9, 21.8, 22.9, 23.8, 24.49, 24.8, 25.17, 25.6, 26.68, 28.93, 30.45, 31.77, 33.90, 34.01, 34.07, 38.8, 46.22, 53.3, 54.48, 66.83, 67.62, 68.18, 71.77, 72.21, 76.35, 77.00, 77.2, 14 77.64, 125.93, 126.46, 128.39, 128.44, 128.79, 130.63, 130.81, 131.04, 137.79, 213.88.

Example 5: 15RS- 16,16-trimethylene-PGE2 (compound 5) To a stirred solution of 15RS-l6,16-trimethylene-PGE2 methyl ester (52 mg, 0.13 mmol) in acetone (0.4 ml) and phosphate buffer pH 7 (4 ml) was added lipase VII (40 mg). The mixture was stirred at room temperature for 24 h (TLC monitoring). The mixture was quenched with ethanol (3 ml) and extracted with ethyl acetate (2x10 ml). The organic layer was washed with brine, dried (sodium sulfate), and concentrated in vacuo furnishing 46 mg of the product as an oil.

Example 6: 15RS- 16, 16-trimethy lene-PGE2 methyl ester (compound 6) The synthesis of 15RS-16,16-trimehyleneprostaglandin E2 (Skotnicki, S. et al. 1977) is schematically shown in Scheme 2. Bold figures in the following refer to respective structures in Scheme 2.

Ethyl 2,2-trimethyllenehexanoate (9) To a stirred solution of N-isopropylcyclohexylamine (56.2 g, 398 mmol) in THF (400 ml) at -78 °C was added rapidly n-BuLi (159 ml, 398 mmol of 2.5 M in hexane). To the resulting solution was added dropwise ethyl cyclobutanecarboxylate (8) (50 g, 390 mmol) and stirred for 30 min, then warmed to 0 °C and dropped into a solution of n-butyl iodide (159 ml, 398 mmol of 2.5 mol in hexane) in DMSO (200 ml). The reaction mixture was stirred for 1 h at room temperature (TLC monitoring). The salt was removed by filtration and the filtrate was concentrated in vacuum. The residue was dissolved in hexane and washed with HC1 2%, brine and water, then dried over sodium sulfate, and evaporated in vacuo. The residual oil was distilled (49-56 °C, 1 mmHg) to give 26.5 g (37%) of the product. iH NMR (CDCI3) d 0.9 (t, 3H), 1.2 (t, 3H), 1.8-2.0 (dm, 5H), 2.2-2.5 (m, 3H), 4.2 (m, 2H). 2.2-Trimethylenehexan-l-ol (10) To a stirred solution of ethyl 2,2-trimethylenehexanoate (9) (26.5 g, 144mmol) in dry toluene (100 ml) was added dropwise DIBAL-H (206 ml, 289 mmol of 1.4 mol in toluene) at 0 °C. The resulting solution was stirred at room temperature for 3 h (TLC monitoring), and then poured into iced HC1 5%. The organic layer was separated and washed with HC1 5%, brine, dried, filtered and concentrated to give 30 g of the product as an oil. lU NMR (CDCI3) d 0.9 (t, 3H), 1.8-2.0(dm, 5H), 2.5 (m, 1H), 3.0 (m, lH), 3.6 (m, 2H). 2.2-Trimethylenehexaldehvde (11) To a solution of 2,2-trimethylenehexan-l-ol (10) (30 g, 210 mmol), in DME (400 ml), was added dicyclohexanecarbodiimide (DCC) (130 g, 630 mmol), DMSO (120 ml) and orthophosphoric acid (10.3 g). The mixture was stirred at room temperature for 3 h (TLC monitoring), and filtered. The filtrate was diluted with dichloromethane (300 ml), and washed with water. The organic layer was separated. The residue was removed by filtration. The filtrate was washed with brine (100 ml), dried and concentrated in vacuum. The residue was purified by column chromatography on silica gel using hexane as eluent to give the title product (17.3 g) as an oil. 1H NMR (CDCI3) d 0.9 (t, 3H), 1.2 (t, 3H), 1.8-2.0 (dm, 5H), 8.8 (s, 1H). 4.4-Trimethylene-l-octvn-3-ol (12) To a solution of lithium acetylide-ethylenediamine complex (12.2 g, 132 mmol) in DMSO (10 ml) was added a solution of 2,2-trimethylenehexaldehyde (11) (17 g, 120 mmol) in DMSO (20 ml) at 0 °C under N2. The mixture was stirred at room temperature for 24 h (TLC monitoring) and then poured into an ice-cold HC1 2% (50 ml) and ether (50 ml). The organic layer was separated and the aqueous layer was extracted with ether (50 ml), the combined organic phases were washed with brine , dried, filtered and concentrated in vacuo. The residue was chromatographed on silica gel using hexane : ethyl acetate 5: 1 as eluent, which gave 12 (7.6 g, 38%) as an oil.

E-Tributyltin-4,4-trimethylene- 1 -octene-3-ol (13) 16 A mixture of 4,4-trimethylene-l-octyn-3-ol (12) (5.0 g, 30 mmol), tributyltin hydride (14.6 ml, 54.2 mmol), and AEBN (30 mg) was stirred at 130 °C for 24 h (TLC monitoring). The residue was chromatographed on silicagel using hexane and hexane:ether 9: 1 , respectively, as eluent, to give the title compound (13) (12.54 g, 91.4%) as an oil.

E-Tributyltin-4.4-trimethylene-3-trimethylsilyloxy-l-octene (14) To the mixture of E-tributyltin-4,4-trimethylene-l-octene-3-ol (13) (7 g, 15.3 mmol) in D F (100 ml) was added imidazole (2.1 g, 30.6 mmol) and trimethylsilyl chloride (2.5 g, 23.0 mmol). The reaction mixture was stirred at room temperature for 1 h (TLC monitoring). The mixture was partitioned between water (200 ml) and ether (200 ml). The organic phase was dried and evaporated in vacuo. The residue was chromatographed on silica gel using hexane as eluent to give 14 (5.53 g). 11.15-bis Trimethylsilyloxy-16,16-trimethylene-5.6-didehvdro-PGE7 methyl ester (17) A dry 100-ml three-necked flask was charged with cupper(I)cyanide (928 mg, 10.4 mmol) and a magnetic bar. The flask was capped with a rubber septum and heated under vacuum to remove any trace of water, and cooled to 0 °C under N2. Dry THF was added and followed by methyl lithium (14 ml, 22.4 mmol of 1.6 mol in diethyl ether), via a syringe. The mixture was stirred at 0 °C for 15 min. during which the suspension became clear and homogeneous. A solution of E-tributyltin-4,4-trimethylene-3-trimethylsilyloxy-l-octene (14) (5.9 g, 11.2 mmol) in THF (10 ml) was added, via a syringe, at 0 °C and stirred at room temperature for 30 min. To the resulting solution a solution of 4-(t-butyldimethylsilyloxy)-cyclopentenone (15) (1.7 g, 8 mmol) in THF (6 ml), trimethylsilyl chloride (4.35 g, 40 mmol) and triethylamine (8.1 g, 80 mmol) was added, at -70 °C, successively and stirred at -70 °C for another 15 min, then for 15 min at 0 °C. The mixture was partitioned between hexane (600 ml) and water (300 ml). The organic layer was separated, dried over sodium sulfate, filtered and concentrated in vacuo to give the crude silyl enol ether as a clear oil. To the stirred solution of the silyl enol ether in THF (50 ml), under N2, at -30 °C methyl lithium (7.7 ml, 12.3 mmol of 1.6 mol in diethyl ether) was added and stirred for 30 min followed by addition of a freshly prepared methyl- l-triflate-2-hexynoate (16) 17 (Erhardt, P.W., et al. 1987; Caldwell A. G., et al. 1979) and stirred at -40 °C for 5 min. The resulting solution was quenched with saturated aqueous ammonium chloride solution (30 ml) and extracted with ether (3x 100 ml), dried on sodium sulfate, filtered and concentrated in vacuo. The residue was chromatographed on silica gel using hexane : ethyl acetate (1: 1) as eluent, to give a clear oil of a mixture of 15RS isomers (2.71 g, 57.3%) Rf= 0.36 (Si02, ether : hexane 1:1). 1H NMR CDCI3) d 0.2 (dm, 12H), 0.8-0.9 (ms, 18H), 1.8 (m, 2H), 2.3 (m, 4H), 3.7 (s, 3H), 3.9-4.1 (dm, 2H), 5.5- 5.6 (2H). The NMR was also performed on the desilylated analogue, 16,16-trimethylene-5,6-didehydro-PGE2 methyl ester, !H NMR (CDCI3) d 0.9 (t, 3H), 1.2- I.3 (m, 3H), 1.9-2.1 (m, 4H), 3.7 (s, 3H), 4.1 (m, 2H), 5.6-5.9 (dm, 2H).

I I.15-bis Trimethylsilyloxy-16.16-trimethylene-PGE2 methyl ester To a stirred solution of 11,15-bis trimethylsilyloxy-16,16-trimethylene-5,6-didehydro-PGE2 methyl ester (17) (500 mg, 0.8 mmol), in benzene : cyclohexane 1 : 1 (50 ml) was added Pd-BaS04 (250 mg) and quinoline (250 mg) and stirred at -40 °C under H2 atmosphere for 5 h (TLC monitoring). The reaction mixture was diluted with ether and filtered through celite, and concentrated in vacuum. The residue was chromatographed on silica gel using hexane : ethyl acetate 9:1 to give 442 mg of the corresponding product. 16.16-Trimethylene-PGE? methyl ester (6) To the solution of 11,15-bis trimethylsilyloxy-16,16-trimethylene-PGE2 methyl ester (374 mg, 0.589 mmol) in THF ( 18 ml) was added HF 40% (3.5 ml) in THF (1 ml) at 0 °C. The reaction mixture was stirred for 5 h (TLC monitoring) and then poured into a mixture of sodium hydrogen carbonate 5% (30 ml) and ethyl acetate (50 ml). The organic layer was separated and the aqueous layer was washed with ethyl acetate (2x30 ml). The organic layers were pooled and dried, on sodium sulfate, and concentrated in vacuo. The residue was chromatographed on silica gel using hexane : ethyl acetatel:l, and ethyl acetate successively to give 6 (75 mg, 31%), as an oil. *H NMR (CDCI3) d 0.9 (t, 3H), 1.3 (t, 6H), 2.0-2.6 (mm, 9H), (dm, 5H), 3.6 (s, 3H), 4.1 (m, 2H), 5.4 (m, 2H), 5.6-5.8 (dm, 2H); 13C NMR (CDCI3) d 14.222, 14.9, 23.7, s 18 24.7, 25.2, 26.2, 26.5, 26.6, 26.8, 29.7, 33.4, 36.5, 44.9, 46.0, 51.6, 54.0, 54.6, 71.9, 76.7, 77.06, 77.1, 77.38, 126.5, 126.9, 127.7, 130.9, 132.5, 132.9, 133.36, 133.46, 174.15, 214.32.

Example 7: Synthesis of 13,14-dihydro-17-(3-fluorophenyl)-18,19,20-trinor PGE2 isopropyl ester (compound 7) The synthesis of the title compound is schematically shown in Scheme 3. Bold figures refer to respective structures in Scheme 3.

Dimethyl-(2-oxo-4-(3-fluorophenylbutyl) phosphonate To a stirred suspension of sodium hydride (4.17 g, 138 mmol) previously washed with n-pentane, in dry THF (250 ml) at room temperature was added dropwise a solution of dimethyl-2-oxo-propylphosphonate (23.12 g, 132.3 mmol) in THF (1 10 ml). The reaction mixture was stirred for 2 h, then cooled in an ice bath and treated with a solution of n-BuLi (10.2 g, 158.7 mmol) in hexane, causing a dark brown solution to be formed. Stirring was continued for 2 h at 0 °C, followed by dropwise addition of 3-fluorobenzyl bromide (25 g, 132.3 mmol) in THF (50 ml). The reaction mixture was gradually warmed to room temperature and after 3 h (TLC monitoring), it was quenched with 10% HC1 (20 ml). The mixture was poured into ice-water (200 ml), extracted with CHCI3 (2x150 ml), the organic layers were collected, washed with brine (150 ml), chromatographed on silica gel using CH2CI2 and EtOAc successively as eluent, furnishing 19.5 g of a slightly yellow oil. R = 0.37 (silica gel, EtOAc:acetone 1:1) (lS.5R.6R.7R -6-Formyl-7-(4-phenyl benzoyloxy)-2-oxabicvclolY3.3.01octane-3-one 19 To a solution of the alcohol 18 (19.0 g, 53.9 mmol) in DME (100 ml), cooled to 18 °C, was added dicyclohexylcarbodiimide (DCC) (33.3, 161.8 mmol), DMSO (38.2 ml) and phosphoric acid (1.43 ml, 21.28 mmol). The temperature of the reaction mixture was kept below 25 °C for 30 min. The reaction mixture was stirred at room temperature for additional 2 hours (TLC monitoring), and the precipitate was removed by filtration and washed with ether (2x50 ml). The combined organic layer was washed with water (50 ml) and brine (2x50 ml), the aqueous solution was extracted with ether (100 ml), the organic layers were collected and dried over sodium sulfate, filtered, and used directly for the next step. TLC Rf = 0.37 (silica gel, EtOAc:toluene 2:1). (lS.5R.6RJRV6-{3-Oxo-5-(3-fluorophenyl)-l-E-pentenyl )-7-(4-phenyl benzoyloxyV 2-oxabicyclor3.3.01octane-3-one (20) To a stirred suspension of NaH (1.9 g, 65.1 mmol), prewashed with n-pentane, in DME (130 ml) under nitrogen, was added dropwise dimethyl-2-oxo-4-(3-fluorophenyl) butylphosphonate (Wadsworth, Jr., W. S., et al. 1961) (19.3 g, 70.5 mmol), in DME (100 ml) and stirred vigorously for 1 h at room temperature. The mixture was then cooled to -10 °C and a solution of the crude aldehyde 19 was added dropwise. After 30 min. at 0 °C and 2 h at room temperature (TLC monitoring), the reaction mixture was neutralized with acetic acid, the solvent was removed in vacuo and the residue was dissolved in EtOAc (200 ml), and washed with water (50 ml) and brine (50 ml). The organic layer was dried over anhydrous sodium sulfate, filtered and evaporated in vacuo. The residue was stirred with ether (100 ml), the resulting white precipitate was filtered and washed with cold ether, giving a white crystalline substance yield (17 g, 58.5%) Rf= 0.56 (silica gel, ethyl acetate : toluene 2:1) (lS.5R.6R,7RV6-(3S-3-Hvdroxy-5-(3-fluorophenvn-l-pentenvn-7-(4^phenyl benzoyloxy'^-oxabicvclorSAOloctane-S-one tel) To a stirred solution of the enone 20 (17.1 g, 34.3 mmol) in THF (20 ml) and cerium chloride (CeCl3.7 ¾0) (3.8g, 10.3 mmol) in THF:ether 1:2 (60 ml) cooled to -20 °C under nitrogen was added sodium borohydride (0.8 g, 20.57 mmol) in small portions. The reaction mixture was stirred for 2 h (TLC monitoring). The temperature was raised to ±0 °C, then quenched by adding water (20 ml) and an aqueous solution of 10% HC1 to pH 4 and extracted with EtOAc (50 ml). The organic layer was separated and washed with brine, dried on anhydrous sodium sulfate, concentrated in vacuo and chromatographed twice on silica gel using toluene:EtOAc 2: 1 and 1 :1 successively as eluent, furnishing 4 (5 g) as a white crystalline product Rf= 0.32 (silica gel, EtOAc:toluene 2:l. ( 1 S.5R.6R.7RV6- ( 3R-3-Hvdroxy-5-(3-fluoroDhenyl 1 -pentyl l-7-(4-phenyl benzoyloxy1-2-oxabicvcior3.3.01octane-3-one (22) To a suspension of 10% Pd/C (0.1 g) in sodium nitrite (3.6 ml, 1.8 mmoi) and ethanol (15 ml) was added a solution of 21 (3 g, 6.0 mmol) in ethanol (6.0 ml). The mixture was stirred under hydrogen atmosphere for 6 h (TLC monitoring), and quenched with 1M solution of HC1. The catalyst was removed by filtration through a celite pad, washed with ethanol abs. (15 ml). The solvent was removed in vacuo. The resulting oil was dissolved in EtOAc (100 ml), and washed with brine 15% (30 ml). The water phase was washed with EtOAc (40 ml). The combined organic extracts were dried over sodium sulfate and filtered. The solvent was removed in vacuo. The residue was chromatographed on silica gel using EtOAc as eluent, which gave 5 (2.94 g), Rf= 0.25 (silica gel, EtOAc). f 1 S .5R.6R.7RV6- ( 3R-3-Hvdroxy-5-(3-fluorophenyl )- 1 -pentyl ) -7-R-hvdroxy-2-oxabicvclor3.3.01octane-3-one (23) To a solution of the lactone 22 (2.8 g, 5.65 mmol) in methanol (15 ml) was added potassium carbonate (0.47 g, 3.3 mmol) and the mixture was stirred at ambient temperature for 6 h (TLC monitoring). The mixture was neutralised with 10% aqueous solution of HC1 and extracted with EtOAc (2x30 ml). The organic phase was dried on anhydrous sodium sulfate and evaporated to dryness. The crude product was chromatographed on silica gel using EtOAc:acetone 1: 1 as eluent. The title compound 23 was obtained as a white crystalline product; yield 1.6 g, Rf= 0.17 (silica gel, EtOAc); IH NMR (CDCI3) d 1.2-1.4 (m, IH), 1.54 (m, 3H), 1.8 (m, 3H), 2.1 (m, IH), 2.2 (m, IH), 2.3 (m, IH), 2.6 (m, 2H), 2.67 (m, IH), 2.8 (m, 2H), 3.60 (m, CH2CHOHCH2), 4.0 (m, CHOH) 4.92 (m, CHOC=0), 6.8-7.0 (m, 3H), 7.28 (m, IH). (lS.5R.6R.7R)-6-(3R-3-t-butyl dimethylsilyloxy-5-(3-fluorophenyl)-l -pentyl ) -7-R-t-butyl dimethylsilyloxy-2-oxabicyclor3.3.01octane-3-one (24) 21 t-Butyldimetyhylsilyl chloride (2.3 g, 14.9 mmol) was added in one portion to a solution of the diol 23, triethyl amine (2.1 ml, 14.8 mmol) and 4-dimethylamino pyridine (0.06 g, 0.1 mmol) in dichloromethane (20 ml) with vigorous stirring at room temperature for 24 h, and the reaction mixture was concentrated in vacuo. The crude product was dissolved in ethyl acetate (50 ml), washed with water (20 ml) and 5% aqueous solution of sodium hydrogen carbonate (20 ml). The organic phase was dried on sodium sulfate, filtered and concentrated in vacuo. The residue was chromatographed on silica gel using dichloromethane as eluent to give 3 g of the product as oil. /?/= 0.68 (silica gel, ether) ( 1 S .5R.6R.7RV6- f 3R-3-t-butyl dimethvIsilyloxy-5-f 3-fluorophenvn- 1 -oentyl ) -7-R-t-butyl dimethylsilyloxy-2-oxabicvclor3.3.01octane-3-ol (25) A solution of diisobutylaluminium hydride (DD3AL) (1.1 g, 7.43 mmol) in dry toluene (5.3 m) was added dropwise to a stirred solution of the lactone 24 (2.7 g, 4.95 mmol) in dry THF (30 ml) at -72/-80 °C. After 1 h (TLC monitoring), the reaction mixture was quenched with methanol (5 ml) and was warmed to room temperature, and added water (50 ml), 10% aqueous solution of HCl (50 ml), extracted with EtOAc (2x50 ml). The organic layer was dried with sodium sulfate, filtered, the solvent was removed in vacuo, and the residue was chromatographed on silica gel using EtOAc and EtOAcracetone 1 :1, respectively, as eluent, to give a yellow oil product (2.7 g), Rf = 0.85 (silica gel, ethyl acetate 1:1). 13.14-Dihvdro- 1 1.15-di-t-butyldimethyl silyloxy- 17-(3-fluorophenylV 18.19.20-trinor-PGF,„ (26) To a stirred suspension of 4-carboxybutyl triphenyl phosphonium bromide (8.78 g, 19.82 mmol) in THF (50 ml) under nitrogen at 0-5 °C was added potassium t-butoxide (3.89 g, 34.6 mmol), and the mixture stirred for 30 min. at room temperature. To the resultant red orange solution of ylide at -15/- 10 °C was added the lactol 25 (2.7 g, 4.95 mmol) in THF (10 ml), and the mixture was stirred for 3-4 h (TLC monitoring). The reaction mixture was diluted with water (30 ml) and washed with ether (4x40 ml). The water layer was acidified with 5% aqueous solution of citric acid to pH 4 and extracted with EtOAc (2x50 ml). The organic phase was washed 22 with brine (30 ml), dried on sodium sulfate, and filtered. The solvent was removed in vacuo, and the slurry 26 was used directly without isolation for the next step. 13.14-Dihvdro-l 1.15-di-t-butyldimethyl silyloxy 17-(3-fluorophenyl)-18.19,20-trinor PGF^ isopropyl ester (27) DBU (5.28 g, 34.7 mmol) was added dropwise to a stirred solution of the crude product 26 (3.16 g, 4.96 mmol) in acetone (20 ml) at 0 °C. The mixture was allowed to warm to room temperature, and isopropyl iodide (5.05 g, 29.7 mmol) was added dropwise. After 4 h (TLC monitoring), the mixture was diluted with EtOAc (100 ml), washed with brine (30 ml), citric acid 3% (2x25 ml) and sodium hydrogen carbonate 5% (2x25 ml) and dried over anhydrous sodium sulfate. The solvent was removed in vacuo and the residue was chromatographed on silica gel using ethenpetroleum ether 1:2 as eluent. This afforded a colourless oil, yield 1.7 g, Rf = 0.43 (silica gel, ether : petroleum ether 1:2) lU NMR (CDCI3) d 0.1 (m, 9H), 0.9 (m, 16H), 1.2 (m, 9H), 1.6-1.8 (mm, lOH), 2.12 (m, 2H), 2.22-2.33 (m, 2H), 2.6-2.9 (dm, 2H), 3.65 (m, CH2CHOHCH2), 3.94 (m, CH9CHOH). 4.16 (m, CH9CHOH). 5.0 (sept. 1H), 5.38 (m, db), 5.47 (m, db), 6.8-7.0 (dm, Ar, 3H), 7.2 (m, Ar, 1H). 13.14-Dihvdro-l 1.15-di-t-butyldimethyl silyloxy 17-(3-fluorophenyl)-18.19.20-trinor PGE? isopropyl ester (28) Pyridinium dichlorochromate (2.43 g, 11.25 mmol) on aluminum oxide (20 g) was added in small portions to a solution of 27 (1.7 g, 2.5 mmol) in dichloromethane (30 ml) and the mixture was stirred at room temperature (TLC monitoring), filtered, and the precipitate was washed with ether: ethyl acetate 2: 1. The solvent was removed in vacuo. The residue was diluted with ether (100 ml) and washed with water (30 ml), 5% aqueous solution of NaHC03 (3x20 ml), the organic phase was separated and dried over sodium sulfate, and evaporated in vacuo to give 28 (1.3 g), as an oil. Rf= 0.72 (silica gel, ethyl acetate). 13.14-Dihvdro-17-(3-fluorophenylV18.19.20-trinor PGE-> isopropyl ester (7) 23 Hydrogen fluoride 15% (12 ml) was added to a solution of 28 (314 mg) in acetonitrile. The mixture was stirred at room temperature for 4 h (TLC monitoring). The reaction mixture was diluted with ethyl acetate (100 ml) and washed with water (3x20 ml), dried and evaporated in vacuo. The residue was chromatographed on silica gel using ethyl acetate as eluent, which gave 7 (64 mg) as an oil, /?/= 0.43 (silica gel, ethyl acetate). *H NMR (CDCI3) d 1.2 (d, 6H), 1.6-1.8 (m, 6H), 1.8 (m, 2H), 2.12 (m, 2H), 2.2-2.3 (m, 2H), 2.6-2.8 (dm, 2H), 3.6 (m, CH9CHOHCH7). 4.16 (m, CH2CHOH), 5.0 (sept. 1H), 5.38 (m, db), 5.47 (m, db), 6.8-7.0 (dm, Ar, 3H), 7.2 (m, Ar, 1H).

Pharmacology Intraocular pressure reducing effect of he test compounds in cats and monkeys.

The compounds were tested for intraocular pressure reducing effect in animal models. The intraocular pressure was measured with a calibrated pneumotonometer. European domestic cats and cynomolgus monkeys were used as experimental animals. The cornea was anaesthetized with oxibuprocain before the measurement. The reductions in intraocular pressure after topical treatment with the PGF2p isopropyl ester (2), 17-phenyl-18,19,20-trinor-PGE2-isopropyl ester (4), 15RS-16,16-trimethylene-methyl ester (6) and 13,14-dihydro-I7-(3-fluorophenyl)-18,19,20-trinor-PGE2-isopropyl ester (7) are demonstrated in Tables IV and V. 24 Table IV. Intraocular pressure reducing effect of 1-10 μg of the test compounds, with effect on the EP| prostanoid receptor, in cats. The control eye received the vehicle only. (n= 5-6; Mean±SEM).

Baseline pressure Pressure 3 h after treatment (mmHg) (mmHg) 2 Experimental eye 24.2 ± 2.3 15.1 ± 2.8 * Control eye 24.5 ± 2.7 22.5 ± 3.4 4 Experimental eye 22.0 ± 1.7 14.2 ± 1.7 * Control eye 21.5 ± 1.7 18.7 ± 1.9 6 Experimental eye 19.2 ± 1.7 9.5 ± 0.5 * Control eye 19.3 ± 1.7 17.0 ± 1.3 7 Experimental eye 20.4 ± -2.0 14.2 ± 0.9 * Control eye 20.6 ± -1.8 18.4 ± 1.5 * p<0.01 (matched pair t-test between eyes) TableV. Intraocular pressure reducing effect of the test compounds, with effect on the EP\ receptor, in monkeys. The dose of PGF2p-isopropyl ester was 30 μg, while that of 17-phenyl-18,19,20-trinor-PGE2-isopropyl ester, and 15RS-16,16-trimethylene-PGE2-isopropyl ester was 3 μg. The control eye received the vehicle only (n=6; Mean±SEM).

Prostaglandin/ Baseline pressure Pressure 4 h after treatment Eye (mmHg) (mmHg) 17.8 ± 1.4 14.1 ± 1.8 16.9 ± 1.2 17.5 ± 2.0 14.1 ± 1.1 9.9 ± 0.9 13.9 ± 1.0 11.5 ± 0.8 6 Experimental eye 20.9 ± 1.6 15.3 ± 2.4 * Control eye 21.3 ± 1.5 19.0 ± 1.5 * p<0.05 (match paired t-test between the eyes) It can be seen that both in cats and monkeys all the prostaglandin analogues with preference for the EP| receptor significantly reduced the intraocular pressure.

Accordingly, the present invention discloses that compounds with selective stimulatory effect on EPi receptors reduce the intraocular pressure, and that such compounds cannot have any melanogenic effect, or at least have significantly reduced effect in the eye since the pigment producing cells, the melanocytes, lack the EPi 26 receptor in man. Thus, the common side-effect of increased iridial pigmentation can be avoided during chronic therapy with prostaglandins selective for EPi receptors.

Scheme 1 COOCH(CH3 3)'2 COOCH(CH3 3)'2 27 Scheme 2 Reagents a. N-isopropylcyclohexyl amine / THF, n-BuLi, ethylcyclobutanecarboxylate/ DMSO b. DIBAL-H, / toluene C.DCC/ DME, DMSO, H3P04, d. Lithium-acetylide-ethylene diamine, DMSO e. tributyltin hydride, AIBN f. Trimethylsilyl chloride (TMSCI), imidazole/ DMF g. Li2CuCN(CH3)2, TMSCI, triethylamine, 4-t-butyl-dimethylsilyloxy-2-cyclopentenone, 1 -tributyltin-4,4,-trimethylene-3-trimethylsilyloxy-1 -octene, methyl-2-yn-8-octanoate K.Pd-BaS04, quinoline, i.HF THF 28 Scheme 3 7 Reagents a. DCC, DMSO, H2S04, D E, H3P04 b. NaH, dimethyl-2-oxo-4-(3-fluorophenyl)-butylphosphonate c. NaBH4. CeCI3.7H20/THF d. Pd/C, NaN02/ THF e. K2C03/Methanol f. TBDMS, TEA, 4-dimethylamino pyridine/dichloromethane g. DIBAL-H/ THF h.4-carboxybutyl triphenyl phosphonium bromide potassium t-butoxide, THF i. DBU , isopropyl iodide/ acetone j.pyridinium chlorochromate, aluminium oxide/ dichloromethane k.HF/acetonitrile 29 References Bill, A. (1975). Blood circulation and fluid dynamics in the eye. Physiol. Rev. 55; 383-417.

Coleman, R.A., Smith, W.L. and Narumiya, S. (1994). Vm. International Union of Pharmacology classification of prostanoid receptors: Properties, distribution and structure of the receptors and their subtypes. Pharmacol. Rev. 46; 205-229.

Crawford, K., and Kaufman, P.(1987). Pilocarpine antagonizes PGF2a-induced ocular hypotension in monkeys. Arch. Ophthalmol. 105; 1112-1116.

Ernhardt, P.W, Owens, A. H. (1987) Facile Formation of Quaternary azetidinium compounds During Inflation of Dialkylaminopropanols. Synth. Commun. 17, 469-475.

Caldwell, A., G,. Harris, C. J., Stepny, R., Whittaker, N. ( 1979). Hydantoin Prostaglandin analogues, Potent and Selective Inhibitors of Platelet Aggregation. J. C. S. Chem. Commun. 561.

Skotnicki, S„ Schaub, E., Weiss, J. (1977). Prostaglandins and congeners. 14.

Synthesis and Bronchodialator Activity of dl-16,16-trimethyleneprostaglandins. J. Med. Chem. 20, 1042.

Hu, D-N. et'al. (1993). Investigative OphthaJmlogy and Visual Science 34; 2210-2219.

Nilsson, S.F.E., Samuelsson, M., Bill, A., and Stjernschantz, J. (1989). Increased uveoscleral outflow as a possible mechanism of ocular hypotension caused by prostaglandin F2a-isopropyl ester in the cynomolgus monkey. Exp. Eye Res. 48; 707-716. 133871/2 Stjernschantz, J., Selen, G., Sjoquist, B., and Resul, B. (1995). Preclinical pharmacology of latanoprost. Advances in Prostaglandin, Thromboxane and Leukotriene Research 23; 5 13-518.

Stjernschantz, J. and Aim, A. (1996). Latanoprost as a new horizon in the medical management of glaucoma. Current Opinion in Ophthalmology 7; 2: 11-17.

Toris, C, Camras, C.B., and Yablonski, M.E. (1993). Effects of PhXA4I, a new prostaglandin F2a analogue, on aqueous humor dynamics in human eyes.

Ophthalmology 10; 1297-1304.

Wodswarth, Jr., W. 5., Emmon, W. D. (1961). The Utility of Phosphonate Carbanions in Olefin Synthesis. J. Am. Chem. Soc. 83, 1733.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Claims (7)

133871/2 -31 THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. An ophthalmological composition for treating glaucoma or ocular hypertension without increased or with reduced melanogenesis side effect, comprising a therapeutically active and physiologically acceptable amount of a compound of the general formula: wherein: the wavy bonds represent the or β configuration, and the dashed bonds represent a single bond, a triple bond or a double bond in the cis or trans configuration; R is hydrogen, saturated or unsaturated alkyl, preferably CMO alkyl, cycloalkyl, preferably C3-8 cycloalkyl, aryl, arylalkyl, preferably aryl-C2.5 alkyl, or heteroaryl; Rl is a saturated or unsaturated alkyl group having 2-5 carbon atoms, optionally interrupted by heteroatoms seleeted from oxygen, sulfur and nitrogen, · cycloalkyl, preferably C3-7 cycloalkyl, cycloalkenyl, preferably C3-7 cycloalkenyl, aryl or heteroaryl; X is C-OH or C=0; R2 is hydrogen, hydroxy, methyl, ethyl, methoxy or OCOR4, where R4 is a straight or branched chain saturated or unsaturated alkyl group, preferably Cj-io alkyl, especially Ci-6 alkyl, or a cycloalkyl, preferably C3-8 cycloalkyl, or aryl group; R3 is a straight or branched chain saturated or unsaturated alkyl group, preferably having 3-8 carbon atoms, especially 3-5 carbon atoms, optionally interrupted by one or more heteroatoms selected from oxygen, sulfur and nitrogen, each carbon atom optionally being substituted with a substituent selected from C1.5 alkyl, hydroxy and carbonyl groups, hydroxy and carbonyl preferentially being attached to carbon 15 of the prostaglandin 133871/4 -32- structure, and said alkyl group optionally containing a cycloalkyl, preferably C3.8 cycloalkyl, aryl or heteroaryl group, which may be mono- or independently multi-substituted with C1-3 alkyl, C1-3 alkoxy, hydroxy, nitro, trifluoromethyl or halogen; or a pharmaceutically acceptable salt or ester thereof, which is a selective agonist for EP! prostanoid receptors, and an ophthalmologically compatible carrier.

2. The composition according to claim 1, wherein the prostaglandin analogue is 15(R,S)-16, 16-trimethylene-PGE2 or an alkyl ester thereof.

3. The composition according to claim 1, wherein the prostaglandin analogue is 13,14-dihydro-17-(3-fluorophenyl)-18,19,20-trinor-PGE2 or an alkyl ester thereof.

4. The use of an effective intraocular pressure reducing amount of a therapeutically active and physiologically acceptable prostaglandin analogue which is a selective agonist for EPi prostanoid receptors, or a pharmaceutically acceptable salt or ester thereof, wherein the prostaglandin analogue is derived from PGF or PGE prostaglandins, or wherein the prostaglandin analogue is a compound of the general formula: COOR wherein: the wavy bonds represent the a or β configuration, and the dashed bonds represent a single 133871/4 -33- bond, a triple bond or a double bond in the cis or trans configuration; R is hydrogen, saturated or unsaturated alkyl, preferably CMo alkyl, cycloalkyl, preferably C3-8 cycloalkyl, aryl, arylalkyl, preferably aryl-C2-5 alkyl, or heteroaryl; Rl is a saturated or unsaturated alkyl group having 2-5 carbon atoms, optionally interrupted by heteroatoms selected from oxygen, sulfur and nitrogen, cycloalkyl, preferably C3.7 cycloalkyl, cycloalkenyl, preferably C3.7 cycloalkenyl, aryl or heteroaryl; X is C-OH or C=0; R2 is hydrogen, hydroxy, methyl, ethyl, methoxy or OCOR4, where R4 is a straight or branched chain saturated or unsaturated alkyl group, preferably C MO alkyl, especially Ci-6 alkyl, or a cycloalkyl, preferably C3-8 cycloalkyl, or aryl group; R3 is a straight or branched chain saturated or unsaturated alkyl group, preferably having 3-8 carbon atoms, especially 3-5 carbon atoms, optionally interrupted by one or more heteroatoms selected from oxygen, sulfur and nitrogen, each carbon atom optionally being substituted with a substiruent selected from Ci_5 alkyl, hydroxy and carbonyl groups* hydroxy and carbonyl preferentially being attached to carbon 15 of the prostaglandin structure, and said alkyl group optionally containing a cycloalkyl, preferably C3.8 cycloalkyl, aryl or heteroaryl group, which may be mono- or independently multi-substituted with C i3 alkyl, C 1.3 alkoxy, hydroxy, nitro, trifluoromethyl or halogen; or a pharmaceutically acceptable salt or ester thereof, in the preparation of a medicament for treating glaucoma or ocular hypertension without increased or with reduced melanogenesis side-effect, in a subject's eye, substantially as described in the specification.

5. The use according to claim 4, wherein the prostaglandin analogue is 15(R,S)-16,16-trimethylene-PGE2 or an alkyl ester thereof. 133871 /3 -34-

6. The use according to claim 4 , wherein the prostaglandin analogue is 13, 1 4-dihydro- 1 7-(3-fluorophenyl)- 18, 1 9,20-trinor-PGE2 or an alkyi ester thereof

7. The use according to any one of claims 4 to 6, wherein a therapeutically active and physiologically acceptable composition containing said prostaglandin analogue is administered topically on the eye 1 -3 times daily. LUZZATTO & LUZZATTO