Tricyclic heterocycles

Abstract: The invention relates to tricyclic heterocycles, or pharmaceutically-acceptable salts thereof, which possess anti-hyperalgesic properties. The invention also relates to processes for the manufacture of said tricyclic heterocycles; and to novel pharmaceutical compositions containing them. The invention provides a tricyclic heterocycle of the formula I wherein X is oxy, thio, sulphinyl, sulphonyl, amino, (1-4C)alkylamino or methylene; Y is carbonyl or methylene; each R¹ includes hydrogen and halogeno; each of m and n is 1 or 2; each of A¹ and A² is a direct link, alkylene, alkenylene or alkynylene; Ar is phenylene which may optionally bear one or two substituents; and G is carboxy, 1H-tetrazol-5-yl or a group of the formula:- -CONH-SO₂R² wherein R² is (1-4C)alkyl, benzyl or phenyl; or a pharmaceutically-acceptable salt thereof.

Description: This invention relates to novel tricyclic heterocycles, or pharmaceutically-acceptable salts thereof, which possess useful pharmacological properties. More particularly the compounds of the invention may be used to counteract mild or moderate pain by virtue of their anti-hyperalgesic properties. The invention also relates to processes for the manufacture of said tricyclic heterocycles, or pharmaceutically-acceptable salts thereof; to novel pharmaceutical compositions containing them; and to the use of said compounds in the production of an anti-hyperalgesic effect in the human or animal body. As stated above the compounds of the invention may be used to counteract mild to moderate pain such as the pain associated with inflammatory conditions (such as rheumatoid arthritis and osteoarthritis), postoperative pain, post-partum pain, the pain associated with dental conditions (such as dental caries and gingivitis), the pain associated with burns (such as sunburn) and the pain associated with sports injuries and sprains. In many of these conditions a hyperalgesic state is present, i.e. a condition in which a warm-blooded animal is extremely sensitive to mechanical or chemical stimulation which would normally be painless. Thus a hyperalgesic state is known to accompany certain physical injuries to the body, for example the injury inevitably caused by surgery. Hyperalgesia is also known to accompany certain inflammatory conditions in man such as arthritic and rheumatic disease. It is known that low doses of prostaglandin E₁ or prostaglandin E₂ (hereinafter PGE₁ and PGE₂ respectively) can induce the hyperalgesic state. Thus, for example, a long-lasting hyperalgesia occurs when PGE₁ is infused in man and, in particular, the co-administration of PGE₁ with a further chemical stimulant such as bradykinin causes marked pain. Thus it is believed that prostaglandins such as PGE₁ and PGE₂ act to sensitise pain receptors to mechanical or chemical stimulation. These undesirable effects of the arachidonic acid metabolite PGE₂ could be ameliorated if its production could be inhibited. It is believed that such an inhibitory effect, by virtue of inhibition of the enzyme cyclooxygenase, contributes to the mode of action of the non-steroidal anti-inflammatory drugs or NSAIDS such as aspirin and indomethacin. Unfortunately the effective pain relief afforded by such agents is often accompanied by undesirable side effects such as gastrointestinal irritation. An alternative way of ameliorating the effects of PGE₂ is to use an agent capable of antagonising its sensitising effects at the receptor or receptors responsible for mediating hyperalgesia. Certain compounds which possess such prostaglandin-antagonist properties are known. Thus it is known that various 10,11-dihydrodibenzo[b,f][1,4]oxazepine-10-carboxylic acid hydrazides are PGE₂ antagonists and these are stated to possess analgesic properties [European Patent Application No. 0218077]. We have now found that certain novel tricyclic heterocycles which possess a very different side-chain to the carboxylic acid hydrazide side-chain of the compounds disclosed in EP 0218077 are effective PGE₂ antagonists. Thus such compounds are of value in the treatment of mild or moderate pain and in the antagonism of the hyperalgesic state which, for example, accompanies inflammatory conditions such as rheumatoid arthritis and osteoarthritis. The compounds of the invention also possess anti-inflammatory, anti-pyretic and anti-diarrhoeal properties by virtue of antagonism of the effects of PGE₂. According to the invention there is provided a tricyclic heterocycle of the formula I (set out hereinafter) wherein X is oxy, thio, sulphinyl, sulphonyl, amino, (1-4C)alkylamino or methylene, the last named group optionally bearing one or two (1-4C)alkyl groups; Y is carbonyl or methylene, the latter group optionally bearing one or two (1-4C)alkyl groups; each R¹, which may be the same or different, is selected from hydrogen, halogeno, trifluoromethyl, nitro, cyano, hydroxy, amino, (1-4C)alkyl, (1-4C)alkoxy, (1-4C)alkylthio, (1-4C)alkylsulphinyl, (1-4C)alkylsulphonyl, (1-4C)alkylamino and di-(1-4C)alkylamino; m and n, which may be the same or different, is the integer 1 or 2; A¹ is a direct link to Ar, or A¹ is (1-6C)alkylene, (3-6C)alkenylene or (3-6C)alkynylene; A² is a direct link to G; Ar is phenylene which may optionally bear one or two substituents selected from halogeno, trifluoromethyl, nitro, cyano, hydroxy, amino, (1-4C)alkyl, (1-4C)alkoxy, (1-4C)alkylthio, (1-4C)alkylsulphinyl, (1-4C)alkylsulphonyl, (1-4C)alkylamino and di-(1-4C)alkylamino; and G is carboxy, 1H-tetrazol-5-yl or a group of the formula:- -CONH-SO₂R² wherein R² is (1-4C)alkyl, benzyl or phenyl, the latter two of which may optionally bear one or two substituents selected from halogeno, trifluoromethyl, nitro, cyano, hydroxy, (1-4C)alkyl and (1-4C)alkoxy; or when G is carboxy an in-vivo hydrolysable ester thereof or an amide thereof; or a pharmaceutically-acceptable salt thereof. The chemical formulae referred to herein by Roman numerals are set out for convenience on a separate sheet hereinafter. In this specification the generic term "alkyl" includes both straight-chain and branched-chain alkyl groups. However, references to individual alkyl groups such as "propyl" are specific for the straight-chain version only and references to individual branched-chain alkyl groups such as "isopropyl" are specific for the branched-chain version only. An analogous convention applies to other generic terms. It is to be understood that, insofar as certain of the compounds of formula I defined above may exist in optically active or racemic forms by virtue of one or more substituents containing an asymmetric carbon atom, the invention includes in its definition of active ingredient any such optically active or racemic form which possesses anti-hyperalgesic properties. The synthesis of optically active forms may be carried out by standard techniques of organic chemistry well known in the art, for example by synthesis from optically active starting materials or by resolution of a racemic form. Similarly, anti-hyperalgesic properties may be evaluated using the standard laboratory techniques referred to hereinafter. Suitable values for the generic terms referred to above include those set below. A suitable value for the (1-4C)alkyl group when X is (1-4C)alkylamino, or X or Y is methylene which bears one or two (1-4C)alkyl groups is, for example, methyl, ethyl, propyl or isopropyl. A suitable value for each R¹, which may be the same or different, when it is halogeno is, for example, fluoro, chloro or bromo; when it is (1-4C)alkyl is, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec -butyl or tert -butyl; when it is (1-4C)alkoxy is, for example, methoxy, ethoxy, propoxy or isopropoxy; when it is (1-4C)alkylthio is, for example, methylthio, ethylthio, propylthio or isopropylthio; when it is (1-4C)alkylsulphinyl is, for example, methylsulphinyl, ethylsulphinyl, propylsulphinyl or isopropylsulphinyl; when it is (1-4C)alkylsulphonyl is, for example, methylsulphonyl, ethylsulphonyl, propylsulphonyl or isopropylsulphonyl; when it is (1-4C)alkylamino is, for example, methylamino, ethylamino, propylamino or isopropylamino; and when it is di-(1-4C)alkylamino is, for example, dimethylamino, N-ethyl-N-methylamino or diethylamino. A suitable value for A¹ when it is (1-6C)alkylene is, for example, methylene, ethylene, ethylidene, trimethylene, propylidene, propylene, tetramethylene or pentamethylene; when it is (3-6C)alkenylene is, for example, 2-propenylene, 2-methylprop-2-enylene, 2-butenylene or 3-butenylene; and when it is (3-6C)alkynylene is, for example, 2-propynylene, 2-methylprop-2-ynylene, 2-butynylene or 3-butynylene. A suitable value for Ar when it is phenylene is, for example, 1,2-phenylene, 1,3-phenylene or 1,4-phenylene. A suitable value for the one or two substituents which may be present on Ar when it is halogeno is, for example, fluoro, chloro or bromo; when it is (1-4C)alkyl is, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec -butyl or tert -butyl; when it is (1-4C)alkoxy is, for example, methoxy, ethoxy, propoxy or isopropoxy; when it is (1-4C)alkylthio is, for example, methylthio, ethylthio, propylthio or isopropylthio; when it is (1-4C)alkylsulphinyl is, for example, methylsulphinyl, ethylsulphinyl, propylsulphinyl or isopropylsulphinyl; when it is (1-4C)alkylsulphonyl is, for example, methylsulphonyl, ethylsulphonyl, propylsulphonyl or isopropylsulphonyl; when it is (1-4C)alkylamino is, for example, methylamino, ethylamino, propylamino or isopropylamino; and when it is di-(1-4C)alkylamino is, for example, dimethylamino, N-ethyl-N-methylamino or diethylamino. A suitable value for R² when G is a group of the formula: -CONH-SO₂R² and R² is (1-4C)alkyl is, for example, methyl, ethyl, propyl or isopropyl. When G is a group of the formula: -CONH-SO₂R² and R² is benzyl or phenyl which may optionally bear one or two substituents, a suitable value for said substituent when it is halogeno is, for example, fluoro, chloro or bromo; when it is (1-4C)alkyl is, for example, methyl, ethyl, propyl or isopropyl; and when it is (1-4C)alkoxy is, for example, methoxy, ethoxy, propoxy or isopropoxy. A suitable value for an in-vivo hydrolysable ester of a tricyclic heterocycle of the formula I wherein G is carboxy is, for example, a pharmaceutically-acceptable ester which is hydrolysed in the human or animal body to produce the parent acid, for example, an ester formed with a (1-6C)alcohol such as methanol, ethanol, ethylene glycol, propanol or butanol, or with a phenol or benzyl alcohol such as phenol or benzyl alcohol or a substituted phenol or benzyl alcohol wherein the substituent is, for example, a halogeno (such as fluoro or chloro), (1-4C)alkyl (such as methyl) or (1-4C)alkoxy (such as methoxy) group. A suitable value for an amide of a tricyclic heterocycle of the formula I wherein G is carboxy is, for example, a N-(1-6C)alkyl or N,N-di-(1-6C)alkyl amide such as a N-methyl, N-ethyl, N-propyl, N,N-dimethyl, N-ethyl-N-methyl or N,N-diethyl amide. A suitable pharmaceutically-acceptable salt of a tricyclic heterocycle of the invention is, for example, an acid-addition salt of a tricyclic heterocycle of the invention which is sufficiently basic, for example an acid-addition salt with an inorganic or organic acid such as hydrochloric, hydrobromic, sulphuric, trifluoroacetic, citric or maleic acid; or, for example a salt of a tricyclic heterocycle of the invention which is sufficiently acidic, for example an alkali or alkaline earth metal salt such as a calcium or magnesium salt, or an ammonium salt, or a salt with an organic base such as methylamine, dimethylamine, trimethylamine, piperidine, morpholine or tris-(2-hydroxyethyl)amine. Particular novel compounds of the invention include, for example, tricyclic heterocycles of the formula I wherein:- (a) X is oxy, thio, sulphinyl or sulphonyl; and Y, R¹, m, n, A¹, A², Ar and G have any of the meanings defined hereinbefore; (b) X is oxy, thio, amino, (1-4C)alkylamino or methylene; and Y, R¹, m, n, A¹, A², Ar and G have any of the meanings defined hereinbefore; (c) X is oxy; and Y, R¹, m, n, A¹, A², Ar and G have any of the meanings defined hereinbefore; (d) Y is methylene optionally bearing one or two (1-4C)alkyl groups; and X, R¹, m, n, A¹, A², Ar and G have any of the meanings defined hereinbefore; (e) each R¹, which may be the same or different, is selected from hydrogen, halogeno, trifluoromethyl, nitro and cyano; and X, Y, m, n, A¹, A², Ar and G have any of the meanings defined hereinbefore; (f) each R¹, which may be the same or different, is selected from hydrogen, halogeno, trifluoromethyl, nitro, cyano, (1-4C)alkyl, (1-4C)alkoxy, (1-4C)alkylthio, (1-4C)alkylsulphinyl and (1-4C)alkylsulphonyl; and X, Y, m, n, A¹, A², Ar and G have any of the meanings defined hereinbefore; (g) each of m and n is the integer 1; and X, Y, R¹, A¹, A², Ar and G have any of the meanings defined hereinbefore; (h) A¹ is (1-6C)alkylene; and X, Y, R¹, m, n, A², Ar and G have any of the meanings defined hereinbefore; (i) A¹ is (1-6C)alkylene, (3-6C)alkenylene or (3-6C)alkynylene; and X, Y, R¹, m, n, A², Ar and G have any of the meanings defined hereinbefore; (j) A² is a direct link to G; and X, Y, R¹, m, n, A¹, Ar and G have any of the meanings defined hereinbefore; (l) Ar is 1,3-phenylene or 1,4-phenylene which may optionally bear one substituent selected from halogeno, trifluoromethyl, nitro, cyano, hydroxy, (1-4C)alkyl and (1-4C)alkoxy; and X, Y, R¹, m, n, A¹, A² and G have any of the meanings defined hereinbefore; (m) Ar is 1,2-phenylene, 1,3-phenylene or 1,4-phenylene which may optionally bear one substituent selected from halogeno, trifluoromethyl, nitro, cyano, hydroxy, amino, (1-4C)alkyl and (1-4C)alkoxy; and X, Y, R¹, m, n, A¹, A² and G have any of the meanings defined hereinbefore; (n) G is carboxy or an in-vivo hydrolysable ester thereof; and X, Y, R¹, m, n, A¹, A² and Ar have any of the meanings defined hereinbefore; (o) G is 1H-tetrazol-5-yl; and X, Y, R¹, m, n, A¹, A² and Ar have any of the meanings defined hereinbefore; and (p) G is a group of the formula:- -CONH-SO₂R² wherein R² is (1-4C)alkyl or phenyl, the latter optionally bearing one or two substituents selected from halogeno, trifluoromethyl, nitro, cyano, hydroxy, (1-4C)alkyl and (1-4C)alkoxy; and X, Y, R¹, m, n, A¹, A² and Ar have any of the meanings defined hereinbefore; or a pharmaceutically-acceptable salt thereof. A preferred compound of the invention comprises a tricyclic heterocycle of the formula I wherein X is oxy, thio, amino, methylamino, ethylamino or methylene; Y is methylene optionally bearing one or two methyl or ethyl groups; each R¹, which may be the same or different, is selected from hydrogen, fluoro, chloro, bromo, trifluoromethyl, nitro, cyano, methyl, ethyl, methoxy, ethoxy, methylthio, methylsulphinyl and methylsulphonyl; each of m and n is the integer 1; A¹ is methylene, ethylene, ethylidene, trimethylene, propylidene, propylene, 2-propenylene or 2-propynylene; A² is a direct link to G; Ar is 1,2-phenylene, 1,3-phenylene or 1,4-phenylene which may optionally bear one substituent selected from fluoro, chloro, bromo, trifluoromethyl, nitro, cyano, hydroxy, amino, methyl, ethyl, methoxy and ethoxy; and G is carboxy, 1H-tetrazol-5-yl or a group of the formula:- -CONHSO₂R² wherein R² is methyl, ethyl or phenyl, the last group optionally bearing one substituent selected from fluoro, chloro, trifluoromethyl, nitro, cyano, hydroxy, methyl and methoxy; or when G is carboxy an in-vivo hydrolysable ester thereof; or a pharmaceutically-acceptable salt thereof. A preferred compound of the invention comprises a tricyclic heterocycle of the formula I wherein X is oxy; Y is methylene optionally bearing one or two methyl or ethyl groups; each R¹, which may be the same or different, is selected from hydrogen, fluoro, chloro, bromo, trifluoromethyl, nitro and cyano; each of m and n is the integer 1; A¹ is methylene, ethylene, ethylidene, trimethylene, propylidene or propylene; A² is a direct link to G; Ar is 1,3-phenylene or 1,4-phenylene which may optionally bear one substituent selected from fluoro, chloro, bromo, trifluoromethyl, nitro, cyano, hydroxy, methyl, ethyl, methoxy and ethoxy; and G is carboxy or an in-vivo hydrolysable ester thereof; or a pharmaceutically-acceptable salt thereof. A further preferred compound of the invention comprises a tricyclic heterocycle of the formula I wherein X is oxy, thio, amino or methylene; Y is methylene; each R¹, which may be the same or different, is selected from hydrogen, chloro and trifluoromethyl; each of m and n is the integer 1; A¹ is methylene, trimethylene or 2-propenylene; A² is a direct link to G; Ar is 1,3-phenylene or 1,4-phenylene which may optionally bear one substituent selected from fluoro, nitro, hydroxy, amino and methoxy; and G is carboxy or an in-vivo hydrolysable ester thereof; or G is a group of the formula:- -CONHSO₂R² wherein R² is phenyl; or a pharmaceutically-acceptable salt thereof. A further preferred compound of the invention comprises a tricyclic heterocycle of the formula I wherein X is oxy; Y is methylene; each R¹, which may be the same or different, is selected from hydrogen, chloro and trifluoromethyl; each of m and n is the integer 1; A¹ is methylene or trimethylene; A² is a direct link to G; Ar is 1,3-phenylene or 1,4-phenylene which may optionally bear one substituent selected from fluoro, nitro, hydroxy, amino and methoxy; and G is carboxy or an in-vivo hydrolysable ester thereof; or a pharmaceutically-acceptable salt thereof. A further preferred compound of the invention comprises a tricyclic heterocycle of the formula I wherein X is oxy; Y is methylene; each R¹, which may be the same or different, is selected from hydrogen, fluoro, chloro and trifluoromethyl; each of m and n is the integer 1: A¹ is methylene; A² is a direct link to G; Ar is 1,3-phenylene or 1,4-phenylene; and G is carboxy or an in-vivo hydrolysable ester thereof; or a pharmaceutically-acceptable salt thereof. A specific preferred compound of the invention is, for example, the following tricyclic heterocycle of the formula I, or an in-vivo hydrolysable ester thereof or a pharmaceutically-acceptable salt thereof:- 3-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)benzoic acid, 4-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)benzoic acid, 4-[3-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-yl)propyl]benzoic acid, 4-(8-trifluoromethyl-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)benzoic acid or 5-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)-2-hydroxybenzoic acid. A compound of the invention comprising a tricyclic heterocycle of the formula I, or when G is carboxy an in-vivo hydrolysable ester or an amide thereof, or a pharmaceutically-acceptable salt thereof, may be prepared by any process known to be applicable to the preparation of structurally-related compounds. Such procedures are provided as a further feature of the invention and are illustrated by the following representative process variants in which, unless otherwise stated, X, Y, R¹, m, n, A¹, A², Ar and G have any of the meanings defined hereinbefore. (a) The coupling of a compound of the formula II with a compound of the formula:- Z-A¹-Ar-A²-G wherein Z is a displaceable group; provided that any hydroxy, amino, alkylamino or carboxy group in these reactants may be protected by a conventional protecting group or alternatively any such group need not be protected, whereafter any such protecting group is removed by conventional means. A suitable displaceable group Z is, for example, a halogeno or sulphonyloxy group such as chloro, bromo, iodo, methanesulphonyloxy or toluene-4-sulphonyloxy. The coupling reaction is preferably carried out in the presence of a suitable base such as, for example, an alkali or alkaline earth metal carbonate, (1-4C)alkoxide, hydroxide or hydride, for example sodium carbonate, potassium carbonate, sodium ethoxide, potassium butoxide, sodium hydroxide, potassium hydroxide, sodium hydride or potassium hydride, or, for example, an organic amine base such as, for example, pyridine, lutidine, collidine, 4-dimethylaminopyridine, triethylamine, morpholine or diazabicyclo[5.4.0]undec-7-ene. The coupling reaction is conveniently performed in a suitable inert solvent or diluent, for example N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulphoxide, acetone, 1,2-dimethoxyethane or tetrahydrofuran, and at a temperature in the range, for example -10 to 150°C, conveniently at or near ambient temperature. Alternatively the coupling reaction may be performed utilising a phase transfer catalyst, for example a tetra-(1-4C)alkylammonium salt such as tetrabutylammonium hydroxide or hydrogen sulphate, a suitable alkali or alkaline earth metal hydroxide as defined above and a suitable inert solvent or diluent, for example methylene chloride or methyl ethyl ketone, and at a temperature in the range, for example 10 to 80°C, conveniently at or near ambient temperature. A suitable protecting group for a hydroxy group is, for example, an arylmethyl group (especially benzyl), a tri-(1-4C)alkylsilyl group (especially trimethylsilyl or tert -butyldimethylsilyl), an aryldi-(1-4C)alkylsilyl group (especially dimethylphenylsilyl), a diaryl-(1-4C)alkylsilyl group (especially tert -butyldiphenylsilyl), a (1-4C)alkyl group (especially methyl), a (2-4C)alkenyl group (especially allyl), a (1-4C)alkoxymethyl group (especially methoxymethyl) or a tetrahydropyranyl group (especially tetrahydroyran-2-yl). The deprotection conditions for the above protecting groups will necessarily vary with the choice of protecting group. Thus, for example, an arylmethyl group such as a benzyl group may be removed, for example, by hydrogenation over a catalyst such as palladium-on-charcoal. Alternatively a trialkylsilyl or an aryldialkylsilyl group such as a tert -butyldimethylsilyl or a dimethylphenylsilyl group may be removed, for example, by treatment with a suitable acid such as hydrochloric, sulphuric, phosphoric or trifluoroacetic acid, or with an alkali metal or ammonium fluoride such as sodium fluoride or, preferably, tetrabutylammonium fluoride. Alternatively an alkyl group may be removed, for example, by treatment with an alkali metal (1-4C)alkylsulphide such as sodium thioethoxide or, for example, by treatment with an alkali metal diarylphosphide such as lithium diphenylphosphide or, for example, by treatment with a boron or aluminium trihalide such as boron tribromide. Alternatively a (1-4C)alkoxymethyl group or tetrahydropyranyl group may be removed, for example, by treatment with a suitable acid such as hydrochloric or trifluoroacetic acid. Alternatively a suitable protecting group for a hydroxy group is, for example, an acyl group, for example a (2-4C)alkanoyl group (especially acetyl) or an aroyl group (especially benzoyl). The deprotection conditions for the above protecting groups will necessarily vary with the choice of protecting group. Thus, for example, an acyl group such as an alkanoyl or an aroyl group may be removed, for example, by hydrolysis with a suitable base such as an alkali metal hydroxide, for example lithium or sodium hydroxide. A suitable protecting group for an amino or alkylamino group is, for example, an acyl group, for example a (2-4C)alkanoyl group (especially acetyl), a (1-4C)alkoxycarbonyl group (especially methoxycarbonyl, ethoxycarbonyl or tert -butoxycarbonyl), an arylmethoxycarbonyl group (especially benzyloxycarbonyl) or an aroyl group (especially benzoyl). The deprotection conditions for the above protecting groups necessarily vary with the choice of protecting group. Thus, for example, an acyl group such as an alkanoyl, alkoxycarbonyl or aroyl group may be removed for example, by hydrolysis with a suitable base such as an alkali metal hydroxide, for example lithium or sodium hydroxide. Alternatively an acyl group such as a tert -butoxycarbonyl group may be removed, for example, by treatment with a suitable acid such as hydrochloric, sulphuric or phosphoric acid or trifluoroacetic acid, and an arylmethoxycarbonyl group such as a benzyloxycarbonyl group may be removed, for example, by hydrogenation over a catalyst such as palladium-on-charcoal. A suitable protecting group for a carboxy group is, for example, an esterifying group, for example a (1-4C)alkyl group (especially methyl or ethyl) which may be removed, for example, by hydrolysis with a suitable base such as an alkali metal hydroxide, for example lithium or sodium hydroxide; or, for example, a tert -butyl group which may be removed, for example, by treatment with a suitable acid such as hydrochloric, sulphuric or phosphoric acid or trifluoroacetic acid. The starting materials of the formula II and of the formula:- Z-A¹-Ar-A²-G may be obtained by standard procedures of organic chemistry. The preparation of such starting materials is described within the accompanying non-limiting Examples which are provided for the purpose of illustration only. Other necessary starting materials are obtainable by analogous procedures or by modifications thereto which are within the ordinary skill of an organic chemist. (b) For the production of a compound of the formula I wherein R¹ is (1-4C)alkylthio or Ar bears a (1-4C)alkylthio substituent, the displacement reaction of a compound of the formula I wherein R¹ is a displaceable substituent Z as defined hereinbefore, or Ar bears a displaceable substituent Z, with a (1-4C)alkylthiol. The displacement reaction is preferably carried out in the presence of a suitable base as defined hereinbefore and in a suitable inert solvent or diluent, for example, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulphoxide, N-methylpyrrolidin-2-one, acetone, tetrahydrofuran or ethanol, and at a temperature in the range, for example 10 to 150°C, conveniently at or near ambient temperature. (c) For the production of a compound of the formula I wherein R¹ is (1-4C)alkylsulphinyl or (1-4C)alkylsulphonyl, or Ar bears a (1-4C)alkylsulphinyl or (1-4C)alkylsulphonyl substituent, the oxidation of a compound of the formula I wherein R¹ is (1-4C)alkylthio or Ar bears a (1-4C)alkylthio substituent. A suitable oxidising agent is, for example, any agent known in the art for the oxidation of thio to sulphinyl and/or sulphonyl, for example, hydrogen peroxide, a peracid (such as 3-chloroperoxybenzoic or peroxyacetic acid), an alkali metal peroxysulphate (such as potassium peroxymonosulphate), chromium trioxide or gaseous oxygen in the presence of platinum. The oxidation is generally carried out under as mild conditions as possible and with the required stoichiometric amount of oxidising agent in order to reduce the risk of over oxidation and damage to other functional groups. In general the reaction is carried out in a suitable solvent or diluent such as methylene chloride, chloroform, acetone, tetrahydrofuran or tert -butyl methyl ether and at a temperature, for example, at or near ambient temperature, that is in the range 15 to 35°C. When a compound carrying a sulphinyl group is required a milder oxidising agent may also be used, for example sodium or potassium metaperiodate, conveniently in a polar solvent such as acetic acid or ethanol. It will be appreciated that when a compound of the formula I containing a sulphonyl group is required, it may be obtained by oxidation of the corresponding sulphinyl compound as well as the corresponding thio compound. (d) For the production of a compound of the formula I wherein G is 1H-tetrazol-5-yl, the reaction of a nitrile of the formula III with an azide. A particularly suitable azide is, for example, an alkali metal azide such as sodium or potassium azide, preferably together with an ammonium halide, for example ammonium chloride, ammonium bromide or triethylammonium chloride. The process is preferably carried out in a suitable polar solvent, for example N,N-dimethylformamide or N-methylpyrrolidin-2-one and, conveniently, at a temperature in the range, for example, 50 to 160°C. (e) For the production of a compound of the formula I wherein G is a group of the formula -CONH-SO₂R² the reaction of a compound of the formula I wherein G is carboxy, or a reactive derivative thereof, with a sulphonamide of the formula:- H₂N-SO₂R² provided that any hydroxy, amino or alkylamino group in these reactants may be protected by a conventional protecting group or alternatively any such group need not be protected, whereafter any such protecting group is removed by conventional means. A suitable reactive derivative of a compound of the formula I wherein G is carboxy is, for example, an acyl halide, for example an acyl chloride formed by the reaction of the acid and an inorganic acid chloride, for example thionyl chloride; a mixed anhydride, for example an anhydride formed by the reaction of the acid and a chloroformate such as isobutyl chloroformate; an active ester, for example an ester formed by the reaction of the acid and a phenol such as pentafluorophenol; an acyl azide, for example an azide formed by the reaction of the acid and an azide such as diphenylphophoryl azide; an acyl cyanide, for example a cyanide formed by the reaction of an acid and a cyanide such as diethylphosphoryl cyanide; or the product of the reaction of the acid and a carbodiimide, for example dicyclohexylcarbodiimide or 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide. The sulphonamidation reaction is preferably carried out in the presence of a suitable base as defined hereinbefore in a suitable solvent or diluent such as methylene chloride, N,N-dimethylformamide, N,N-dimethylacetamide or dimethylsulphoxide and at a temperature in the range, for example, 10 to 100°C, conveniently at or near ambient temperature. (f) For the production of a compound of the formula I wherein R¹ is (1-4C)alkoxy or Ar bears a (1-4C)alkoxy substituent, the alkylation of a compound of the formula I wherein R¹ is hydroxy or Ar bears a hydroxy substituent. A suitable alkylating agent is, for example, any agent known in the art for the alkylation of hydroxy to (1-4C)alkoxy, for example a (1-4C)alkyl halide such as a chloride, bromide or iodide, preferably in the presence of a suitable base as defined hereinbefore. The alkylation reaction is preferably performed in a suitable inert solvent of dilent, for example N,N-dimethylformamide, dimethylsulphoxide, acetone, 1,2-dimethoxyethane or tetrahydrofuran, and at a temperature in the range, for example, 10 to 150°C, conveniently at or near ambient temperature. (g) For the production of a compound of the formula I wherein A¹ is (3-6C)alkynylene, the coupling of an alkyne of the formula IV wherein p is an integer from 1 to 4 with a compound of the formula V wherein Z is a displaceable substituent as defined hereinbefore. The coupling reaction is preferably carried out in the presence of a suitable organometallic catalyst such as, for example, an organopalladium catalyst and/or an organocopper catalyst. Thus, for example, a suitable catalyst is formed when, for example, bis(triphenylphosphine)palladium(II) chloride or tetrakis(triphenylphosphine)palladium(O) and a copper halide, for example cuprous iodide, are mixed. The coupling reaction is generally carried out in a suitable inert solvent or diluent, for example acetonitrile, 1,2-dimethoxyethane, toluene or tetrahydrofuran, at a temperature in the range, for example 0 to 80°C, conveniently at or near ambient temperature, and in the presence of a suitable base such as, for example, a tri-(1-4C)alkylamine such as triethylamine, or a cyclic amine such as piperidine. The alkyne of the formula IV used as a starting material may be obtained, for example, by the alkylation, preferably in the presence of suitable base, of a compound of the formula II with an alkylating agent of the formula H-C≡C-(CH₂) p -Z, wherein p is an integer from 1 to 4, and Z is a displaceable group as defined hereinbefore. (h) For the production of a compound of the formula I wherein A¹ is (3-6C)alkenylene or (1-6C)alkylene, the reduction of the corresponding compound wherein A¹ is (3-6C)alkynylene. In general conditions which are standard in the art for the reduction of an alkynylene group are used. Thus, for example, the reduction may be carried out by the hydrogenation of the alkynylene compound in an inert solvent or diluent in the presence of a suitable metal catalyst. A suitable inert solvent is, for example, an alcohol, for example methanol or ethanol, an ether, for example tetrahydrofuran or tert -butyl methyl ether, or an ester, for example ethyl acetate. A suitable metal catalyst is, for example, palladium or platinum on an inert support, for example charcoal or barium sulphate The reaction is generally carried out a temperature at or near ambient temperature. (i) For the production of a compound of the formula I wherein R¹ is amino or Ar bears an amino substituent, the reduction of a compound of the formula I wherein R¹ is nitro or Ar bears a nitro substituent. A suitable reducing agent is, for example, any agent known in the art for the reduction of a nitro group to an amino group. Thus, for example, the reduction may be carried out by the hydrogenation of a solution of the nitro compound in an inert solvent or diluent in the presence of a suitable metal catalyst, for example finely divided platinum metal (obtained by the reduction of platinum oxide in situ ). A suitable inert solvent or diluent is, for example, an alcohol, for example methanol, ethanol or isopropanol, or an ether, for example tetrahydrofuran. A further suitable reducting agent is, for example, an activated metal such as activated iron (produced by washing iron powder with a dilute solution of an acid such as hydrochloric acid). Thus, for example, the reduction may be carried out by the heating a mixture of the nitro compound and the activated metal in a suitable solvent or diluent such as a mixture of water and an alcohol, for example, methanol or ethanol, to a temperature in the range, for example 50 to 150°C, conveniently at or near 70°C. A further suitable reducing agent is, for example, an oxidisable metal salt such as, for example, stannous chloride or ferrous chloride preferably in the presence of an acid, for example, aqueous hydrochloric acid, in a suitable solvent or diluent such as an ether, for example diethyl ether or a mixture of water and an alcohol, for example methanol or ethanol, and at a temperature in the range, for example 10 to 100°C, conveniently in the range 20 to 70°C. (j) For the production of a compound of the formula I wherein Y is methylene, the reduction of a compound of the formula I wherein Y is carbonyl. A suitable reducing agent is, for example, any agent known in the art for the reduction of the carbonyl group within an amide functional group to a methylene group. Many 'hydride' reducing agents can effect this reduction such as, for example, a metal hydride such as lithium aluminium hydride. Alternatively a borane reducing agent such as, for example, diborane may be used. The reduction is preferably performed in a suitable inert solvent or diluent, for example an ether such as diethyl ether or tetrahydrofuran and at a temperature in the range, for example, 0 to 100°C, conveniently in the range 20 to 70°C. When an in-vivo hydrolysable ester of a compound of the formula I wherein G is carboxy is required, it may be obtained, for example, by reaction of said compound of the formula I wherein G is carboxy, or a reactive derivative thereof as defined hereinbefore, with a suitable esterifying reagent using a conventional procedure. When an amide of a compound of the formula I wherein G is carboxy is required, it may be obtained, for example, by reaction of said compound of the formula I wherein G is carboxy, or a reactive derivative thereof as defined hereinbefore, with a suitable amine using a conventional procedure. When a pharmaceutically-acceptable salt of a compound of the formula I is required, it may be obtained, for example, by reaction of said compound with a suitable acid or base using a conventional procedure. As stated hereinbefore a tricyclic heterocycle of the formula I possesses anti-hyperalgesic properties and hence is of value in the treatment of the hyperalgesic state which, for example, accompanies inflammatory conditions such as rheumatoid arthritis and osteoarthritis. These properties may be demonstrated using one or more of the test procedures set out below:- (a) an in-vitro guinea pig ileum assay which assesses the inhibitory properties of a test compound against PGE₂-induced contractions of the ileum; ileum was immersed in oxygenated Krebs solution containing indomethacin (4 µg/ml) and atropine (1 µM) and which was maintained at 37°C; the ileum was subject to a resting tension of 1 g; a control dose response curve for PGE₂-induced contraction of the ileum was obtained; test compound (dissolved in dimethylsulphoxide) was added to the Krebs solution and a dose response curve for the PGE₂-induced contraction of the ileum in the presence of the test compound was obtained; the pA₂ value for the test compound was calculated; (b) an in-vivo assay in mice which assesses the inhibitory properties of a test compound against writhing induced by the concomitant administration of PGE₂ and bradykinin; each test compound was dosed in a range of doses (either by the subcutaneous or oral routes) to a group of 10 mice; 30 minutes later each mouse was dosed intraperitoneally with PGE₂ (100 nanograms) and bradykinin (1 µg) and the animals were monitored for the writhing response which occurs in approximately 90% of the animals in the absence of the test compound [bradykinin (1 µg) dosed alone induces a writhing response in less than 10% of the animals]; an ED₅₀ value for antagonism of the writhing response was obtained; (c) an in-vivo assay in mice which assesses the inhibitory properties of a test compound against writhing induced by the intraperitoneal administration of phenylbenzoquinone (hereinafter PBQ) using the procedure disclosed in European Patent Application No. 0218077. Although the pharmacological properties of the compounds of the formula I vary with structural change as expected, in general activity possessed by compounds of the formula I may be demonstrated at the following concentrations or doses in one or more of the above-mentioned Tests (a), (b) and (c):- Test (a):- pA₂ > 5.3; Test (b):- ED₅₀ in the range, for example, 5-100 mg/kg orally; Test (c):- ED₅₀ in the range, for example, 10-100 mg/kg orally. Thus, by way of example, the compound 4-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)benzoic acid has a pA₂ value of 7.0 in Test (a) and an ED₅₀ of 19 mg/kg in Test (b) on oral dosing; and the compound 3-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)benzoic acid has a pA₂ of 7.4 in Test (a) and it possesses significant activity at 100 mg/kg in Test (c) on oral dosing. No overt toxicity or other untoward effects were noted in Tests (b) or (c) when compounds of the formula I are administered at several multiples of their minimum inhibitory dose. Prostanoid receptors and in particular receptors for PGE₂ have been tentatively characterised by Kennedy et al . (Advances in Prostaglandin, Thromboxane and Leukotriene Research, 1983, 11 , 327). The known PGE₂ anatagonist SC-19220 blocks the effect of PGE₂ on some tissues such as guinea pig ileum or dog fundus but not on other tissues such as the cat trachea or chick ileum. Those tissues which did possess SC-19220 affected PGE₂ receptors were said to possess EP₁ receptors. Accordingly compounds of the present invention, possessing activity in Test (a), are EP₁ antagonists. According to a further feature of the invention there is provided a pharmaceutical composition which comprises a tricyclic heterocycle of the formula I, or when G is carboxy an in-vivo hydrolysable ester thereof or an amide thereof, or a pharmaceutically-acceptable salt thereof, in association with a pharmaceutically-acceptable diluent or carrier. The composition may be in a form suitable for oral use, for example a tablet, capsule, aqueous or oily solution, suspension or emulsion; for topical use, for example a cream, ointment, gel or aqueous or oily solution or suspension; for nasal use, for example a snuff, nasal spray or nasal drops; for vaginal or rectal use, for example a suppository; for administration by inhalation, for example as a finely divided powder or a liquid aerosol; for sub-lingual or buccal use, for example a tablet or capsule; or for parenteral use (including intravenous, subcutaneous, intramuscular, intravascular or infusion), for example a sterile aqueous or oily solution or suspension. In general the above compositions may be prepared in a conventional manner using conventional excipients. The amount of active ingredient (that is a tricyclic heterocycle of the formula I or a pharmaceutically-acceptable salt thereof) that is combined with one or more excipients to produce a single dosage form will necessarily vary depending upon the host treated and the particular route of administration. For example, a formulation intended for oral administration to humans will generally contain, for example, from 0.5 mg to 2 g of active agent compounded with an appropriate and convenient amount of excipients which may vary from about 5 to about 98 percent by weight of the total composition. Dosage unit forms will generally contain about 1 mg to about 500 mg of an active ingredient. According to a further feature of the invention there is provided a tricyclic heterocycle of the formula I, or when G is carboxy an in-vivo hydrolysable ester thereof or an amide thereof, or a pharmaceutically-acceptable salt thereof, for use in a method of treatment of the human or animal body by therapy. According to a further feature of the invention there is provided the use of a tricyclic heterocycle of the formula I, or when G is carboxy an in-vivo hydrolysable ester thereof or an amide thereof, or a pharmaceutically-acceptable salt thereof, in the manufacture of a medicament for use in the production of an anti-hyperalgesic effect in the human or animal body. According to a further feature of the invention there is provided a method for producing an anti-hyperalgesic effect in the human or animal body in need of such treatment which comprises administering to said body an effective amount of a tricyclic heterocycle of the formula I, or when G is carboxy an in-vivo hydrolysable ester thereof or an amide thereof, or a pharmaceutically-acceptable salt thereof. As mentioned above, a tricyclic heterocycle of the formula I is useful in treating the hyperalgesic state which, for example, accompanies inflammatory conditions such as rheumatoid arthritis and osteoarthritis. In using a compound of the formula I for therapeutic or prophylactic purposes it will generally be administered so that a daily dose in the range, for example, 0.5 mg to 75 mg per kg body weight is received, given if required in divided doses. In general lower doses will be administered when a parenteral route is employed. Thus, for example, for intravenous administration, a dose in the range, for example, 0.5 mg to 30 mg per kg body weight will generally be used. Similarly, for administration by inhalation, a dose in the range, for example, 0.5 mg to 25 mg per kg body weight will be used. Although the compounds of the formula I are primarily of value as therapeutic agents for use in warm-blooded animals (including man), they are also useful whenever it is required to antagonise the effects of PGE₂. Thus, they are useful as pharmacological standards for use in the development of new biological tests and in the search for new pharmacological agents. By virtue of their anti-hyperalgesic effect the compounds of the formula I are of value in the treatment of certain inflammatory diseases which are currently treated with a cyclooxygenase-inhibitory non-steroidal anti-inflammatory drug (NSAID) such as indomethacin, acetylsalicyclic acid, ibuprofen, sulindac, tolmetin and piroxicam. Co-administration of a compound of the formula I with a NSAID can result in a reduction of the quantity of the latter agent needed to produce a therapeutic effect. Thereby the likelihood of adverse side-effects from the NSAID such as gastrointestinal effects are reduced. Thus according to a further feature of the invention there is provided a pharmaceutical composition which comprises a tricyclic heterocycle of the formula I, or when G is carboxy an in-vivo hydrolysable ester thereof or an amide thereof, or a pharmaceutically-acceptable salt thereof, in conjunction or admixture with a cyclooxygenase inhibitory non-steroidal anti-inflammatory agent, and a pharmaceutically-acceptable diluent or carrier. The compositions of the invention may in addition contain one or more therapeutic or prophylactic agents known to be of value for the treatment of mild or moderate pain. Thus, for example, a known mild opiate pain-killer (such as dextropropoxyphene or codeine) or an inhibitor of the enzyme 5-lipoxygenase (such as those disclosed in European Patent Applications Nos. 0351194, 0375368, 0375404, 0375452, 037547, 0381375, 0385662, 0385663, 0385679, 0385680) may usefully also be present in a pharmaceutical composition of the invention. The invention will now be illustrated in the following non-limiting Examples in which, unless otherwise stated:- (i) evaporations were carried out by rotary evaporations in vacuo and work-up procedures were carried out after removal of residual solids by filtration; (ii) operations were carried out at room temperature, that is in the range of 18-20°C and under an atmosphere of an inert gas such as argon; (iii) column chromatography (by the flash procedure) and medium pressure liquid chromatography (MPLC) were performed on Merck Kieselgel silica (Art. 9385) obtained from E. Merck, Darmstadt, W. Germany; (iv) yields are given for illustration only and are not necessarily the maximum attainable; (v) the end-products of the formula I have satisfactory microanalyses and their structures were generally confirmed by NMR and mass spectral techniques; (vi) intermediates were not generally fully characterised and purity was assessed by thin layer chromatographic, infra-red (IR) or NMR analysis; (vii) melting points are uncorrected and were determined using a Mettler SP62 automatic melting point apparatus or an oil-bath apparatus; melting points for the end-products of the formula I were determined after recrystallisation from a conventional organic solvent such as ethanol, methanol, acetone, ether or hexane, alone or in admixture; and (viii) the following abbreviations have been used:- DMF N,N-dimethylformamide; THF tetrahydrofuran. EXAMPLE 1 A solution of 8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepine (1 g; US Patent No. 3,357,998) in DMF (10 ml) was added dropwise to a stirred suspension of sodium hydride (60% w/w dispersion in vegetable oil, 0.207 g) in DMF (10 ml) which had been cooled to 0°C. The mixture was stirred at 0°C for 30 minutes. A solution of 3-methoxycarbonylbenzyl bromide (0.99 g; J. Amer. Chem. Soc ., 1940, 62, 1180) in DMF (5 ml) was added dropwise. The mixture was allowed to warm to ambient temperature and was stirred for 18 hours. The mixture was poured onto ice (50 g) and acidified by the addition of acetic acid. The mixture was extracted with diethyl ether (3 x 50 ml). The combined extracts were washed with water and with brine, dried (MgSO₄) and evaporated. The residue was purified by column chromatography using a 1:1 v/v mixture of methylene chloride and petroleum ether (b.p. 60-80°C) as eluent. There was thus obtained methyl 3-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)benzoate (0.6 g), m.p. 78°C. A mixture of the product so obtained, 2N aqueous sodium hydroxide solution (3.3 ml) and methanol (50 ml) was stirred at ambient temperature for 4 hours. The mixture was evaporated and the residue was acidified to pH4 by the addition of 2N aqueous hydrochloric acid solution. The precipitate so obtained was isolated by filtration and dried. There was thus obtained 3-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)benzoic acid (0.22 g), m.p. 174-176°C (recrystallised from cyclohexane). NMR Spectrum (CDCl₃, δ values) 4.58 (s, 4H), 6.64-7.88 (m, 11H), 12.6-13.1 (broad, 1H); Elemental Analysis Found C, 69.6; H, 4.2; N, 3.8; Cl, 9.7%. C₂₁H₁₆ClNO₃ requires C, 69.0; H, 4.4; N, 3.8; Cl, 9.7%. EXAMPLE 2 The procedures described in Example 1 were repeated except that 4-methoxycarbonylbenzyl bromide was used in place of 3-methoxycarbonylbenzyl bromide. There was thus obtained 4-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)benzoic acid in 20% yield, m.p. 185°C. NMR Spectrum (CDCl₃, δ values) 4.58 (s, 4H), 6.65-7.95 (m, 11H), 12.8-13.1 (broad, 1H); Elemental Analysis Found C, 68.5; H, 4.2; N, 3.6; Cl, 9.3; C₂₁H₁₆ClNO₃ requires C, 69.0; H, 4.4; N, 3.8; Cl, 9.7%. EXAMPLE 3 Using a similar procedure to that described in Example 1, the appropriate 10,11-dihydrodibenzo[b,f][1,4]oxazepine was reacted with the appropriate methoxycarbonylbenzyl bromide and the resultant product was hydrolysed with aqueous sodium hydroxide solution. There were thus obtained the compounds described in Table I, the structures of which were confirmed by proton magnetic resonance and mass spectroscopy and by microanalysis. The appropriate methoxycarbonylbenzyl bromides were obtained from the corresponding commercially-available toluic acids or their methyl esters by conventional N-bromosuccinimide bromination using an analogous procedure to that described in Bull. Chim. Soc. France , 1966, 2821. EXAMPLE 4 A solution of 8-chloro-10,11-dihydrodibenzo[b,f][1,4]-oxazepine (3.79 g) in methylene chloride (25 ml) was added to a solution of tetrabutylammonium hydrogen sulphate (5.56 g) in 1N aqueous sodium hydroxide solution (32.74 ml) and the mixture was stirred at ambient temperature for 30 minutes. A solution of 2-acetoxy-3-methoxcarbonylbenzyl bromide ( Bull. Chim. Soc. France , 1966, 2821; 4.7 g) in methylene chloride (25 ml) was added and the mixture was stirred at ambient temperature for 18 hours. The organic layer was separated, washed with water, dried (MgSO₄) and evaporated. The residue was purified by column chromatography using a 1:1 v/v mixture of petroleum ether (b.p. 60-80°C) and methylene chloride as eluent. There was thus obtained methyl 2-acetoxy-3-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)benzoate (3.64 g) as an oil. A mixture of the product so obtained, 2N aqueous sodium hydroxide solution (10 ml), THF (20 ml) and methanol (10 ml) was stirred at ambient temperature for 2 hours. The organic solvents were evaporated and the aqueous residue was acidified by the addition of 2N aqueous hydrochloric acid solution. The mixture was extracted with diethyl ether (3 x 30 ml). The combined extracts were washed with water and with brine, dried (MgSO₄) and evaporated. The residue was purified by column chromatography using a 2:1 v/v mixture of petroleum ether (b.p. 60-80°C) and methylene chloride as eluent. There was thus obtained methyl 3-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)-2-hydroxybenzoate (1.18 g), m.p. 106-108°C (recrystallised from a mixture of petroleum ether (b.p. 60-80°C) and diethyl ether). A mixture of a portion (0.43 g) of the product so obtained, 1N aqueous sodium hydroxide solution (10 ml), THF (10 ml) and methanol (5 ml) was stirred and heated to reflux for 2 hours. The organic solvents were evaporated and the aqueous residue was acidified by the addition of 2N aqueous hydrochloric acid solution. The mixture was extracted with diethyl ether (3 x 20 ml). The combined extracts were washed with water and with brine, dried (MgSO₄) and evaporated. The solid residue was recrystallised from a mixture of petroleum ether (b.p. 60-80°C) and diethyl ether. There was thus obtained 3-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)-2-hydroxybenzoic acid (0.24 g), m.p. 145-146°C. EXAMPLE 5 A mixture of methyl 3-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)-2-hydroxybenzoate (0.56 g), methyl iodide (1 ml), potassium carbonate (1 g) and DMF (10 ml) was stirred at ambient temperature for 18 hours. The mixture was evaporated and the residue was partitioned between diethyl ether and water. The organic phase was washed with water and with brine, dried (MgSO₄) and evaporated. There was thus obtained methyl 3-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)-2-methoxybenzoate (0.58 g) which was used without further purification. The ester so obtained was hydrolysed using an analogous procedure to that described in the third paragraph of Example 4. There was thus obtained 3-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)-2-methoxybenzoic acid (0.45 g), m.p. 149-150°C (recrystallised from a mixture of petroleum ether (b.p. 60-80°C) and diethyl ether). EXAMPLE 6 Using a similar procedure to that described in Example 4 except that the appropriate acetoxybenzyl bromide was used in place of 2-acetoxy-3-methoxycarbonylbenzyl bromide, and, where appropriate, a similar procedure to that described in Example 5, there were obtained the compounds described in Table II, the structures of which were confirmed by proton magnetic resonance and mass spectroscopy and by microanalysis. With one exception the appropriate acetoxybenzyl bromides were obtained from the corresponding commercially-available hydroxytoluic acids using analogous procedures to those described in Bull. Chim. Soc. France , 1966, 2821. 5-Acetoxy-3-methoxycarbonylbenzyl bromide was prepared from the sodium salt of the acetopyruvate ester described in J. Org. Chem. , 1959, 24 , 1952 using the procedure also described therein. EXAMPLE 7 The procedures described in Example 1 were repeated except that 2-methoxycarbonylbenzyl bromide was used in place of 3-methoxycarbonylbenzyl bromide. There was thus obtained 2-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)benzoic acid in 10% yield, m.p. 203-205°C. EXAMPLE 8 A mixture of methyl 4-[3-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-yl)prop-1-ynyl]benzoate (2.7 g), 10% palladium-on-charcoal catalyst (0.05 g) and THF (100 ml) was stirred under an atmosphere of hydrogen for 9 hours. The mixture was filtered and the filtrate was evaporated. The residue was purified by column chromatography using a 9:1 v/v mixture of methylene chloride and petroleum ether (b.p. 60-80°C) as eluent. There were thus obtained in turn methyl 4-[3-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-yl)propyl]benzoate (0.6 g) as a gum and methyl 4-[3-(10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-yl)propyl]benzoate (0.18 g) as a gum. A mixture of the 8-chloro derivative so obtained, 2N aqueous sodium hydroxide solution (2 ml) and THF (25 ml) was stirred and heated to 50°C for 20 hours. The mixture was evaporated and the residue was acidified by the addition of 2N aqueous hydrochloric acid solution. The mixture was extracted with ethyl acetate (3 x 25 ml). The combined extracts were evaporated and the residue was triturated under methanol. There was thus obtained 4-[3-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-yl]propyl]benzoic acid (0.23 g), m.p. 131-133°C. The methyl 4-[3-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-yl)prop-1-ynyl]benzoate used as a starting material was obtained as follows:- A solution of 8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepine (0.463 g) in DMF (10 ml) was added dropwise to a stirred suspension of sodium hydride (60% w/w dispersion in vegetable oil, 0.08 g) in DMF (10 ml) which had been cooled to 0°C. The mixture was stirred at 0°C for 30 minutes. A solution of propargyl bromide (0.25 ml) in DMF (5 ml) was added dropwise. The mixture was allowed to warm to ambient temperature and was stirred for 18 hours. The mixture was poured into water (50 ml). The mixture was extracted with ethyl acetate (3 x 50 ml). The combined extracts were washed with water and with brine, dried (MgSO₄) and evaporated. The residue was purified by column chromatography using a 1:9 v/v mixture of ethyl acetate and petroleum ether (b.p. 60-80°C) as eluent. There was thus obtained 8-chloro-10-(2-propynyl)-10,11-dihydrodibenzo[b,f][1,4]oxazepine (0.25 g), m.p. 78-79°C. After appropriate repetition of the above-mentioned reaction a mixture of the product so obtained (3 g), methyl 4-iodobenzoate (2.43 g), bis(triphenylphosphine)palladium(II) chloride (0.13 g), cuprous iodide (0.01 g) and triethylamine (50 ml) was stirred at ambient temperature for 20 hours. The mixture was evaporated and the residue was partitioned between methylene chloride and water. The organic phase was dried (MgSO₄) and evaporated. The residue was purified by column chromatography using a 95:1 v/v mixture of petroleum ether (b.p. 60-80°C) and ethyl acetate as eluent. There was thus obtained the required staring material (3.2 g). EXAMPLE 9 The procedure described in the second paragraph of Example 8 were repeated except that methyl 4-[3-(10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-yl)propyl]benzoate was used as a starting material. There was thus obtained 4-[3-(10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-yl)propyl]benzoic acid in 92% yield, m.p. 102-104°C. EXAMPLE 10 The procedure described in the second paragraph of the portion of Example 8 which is concerned with the preparation of starting materials was repeated except that methyl 3-iodobenzoate was used in place of methyl 4-iodobenzoate. There was thus obtained methyl 3-[3-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-yl)prop-1-ynyl]benzoate in 73% yield as a solid, the structure of which was confirmed by proton magnetic resonance spectroscopy. The ester so obtained was hydrolysed using an analogous procedure to that described in the second paragraph of Example 1. There was thus obtained 3-[3-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-yl)propyl]benzoic acid in 10% yield, m.p. 166-168°C. EXAMPLE 11 A mixture of methyl 3-[3-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-yl)prop-1-ynyl]benzoate (3.48 g), 10% palladium-on-charcoal catalyst (0.35 g) and ethyl acetate (150 ml) was stirred under an atmosphere of hydrogen for 5 hours. The mixture was filtered and the filtrate was evaporated. The residue was purified by column chromatography using increasingly polar mixtures of petroleum ether (b.p. 60-80°C) and methylene chloride as eluent. There was thus obtained methyl 3-[(Z)-3-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-yl)prop-1-enyl]benzoate in 98% yield. The ester so obtained was hydrolysed using an analogous procedure to that described in the second paragraph of Example 1. There was thus obtained 3-[(Z)-3-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-yl)prop-1-enyl]benzoic acid in 13% yield, m.p. 130°C. EXAMPLE 12 The procedures described in Example 1 were repeated except that 8-chloro-11-methyl-10,11-dihydrodibenzo[b,f][1,4]oxazepine was used in place of 8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepine. There was thus obtained 3-(8-chloro-11-methyl-10,11-dihydrobenzo[b,f][1,4]oxazepin-10-ylmethyl)benzoic acid in 33% yield, m.p. 99°C. The starting material 8-chloro-11-methyl-10,11-dihydrodibenzo[b,f][1,4]oxazepine used as a starting material was obtained from 5'-chloro-2'-phenoxyacetanilide using analogous procedures to those described in Coll. Czech. Chem. Comm. , 1965, 30 , 463. EXAMPLE 13 The procedures defined in Example 2 were repeated except that 8-chloro-11-methyl-10,11-dihydrodibenzo[b,f][1,4]oxazepine was used in place of 8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepine. There was thus obtained 4-(8-chloro-11-methyl-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)benzoic acid in 27% yield, m.p. 148°C. EXAMPLE 14 A mixture of 8-chloro-10-(3-cyanobenzyl)-10,11-dihydrodibenzo[b,f][1,4]oxazepine (1.77 g), sodium azide (0.36 g), ammonium chloride (0.3 g) and DMF (15 ml) was stirred and heated to 80°C for 8 hours. The mixture was cooled to ambient temperature and poured into water (50 ml). The mixture was extracted with ethyl acetate (3 x 50 ml). The combined extracts were washed with brine, dried (MgSO₄) and evaporated. The residue was purified by column chromatography using a 1:1 v/v mixture of methylene chloride and ethyl acetate as eluent and the product so obtained was triturated under methanol. There was thus obtained 8-chloro-10-[3-(1H-tetrazol-5-yl)benzyl]-10,11-dihydrodibenzo[b,f][1,4]oxazepine (0.312 g), m.p. 206-207°C. The 8-chloro-10-(3-cyanobenzyl)-10,11-dihydrodibenzo[b,f] [1,4]oxazepine used as a starting material was obtained by repetition of the procedure described in the first paragraph of Example 1 except that 3-cyanobenzyl bromide was used in place of 3-methoxycarbonylbenzyl bromide. There was thus obtained the required starting material in 59% yield, m.p. 99°C. EXAMPLE 15 A mixture of 4-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)benzoic acid (3.61 g), benzenesulphonamide (1.55 g), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (1.53 g), 4-dimethylaminopyridine (1.21 g) and methylene chloride (400 ml) was stirred at ambient temperature for 48 hours. The mixture was washed with water (2 x 50 ml), dried (MgSO₄) and evaporated. The residue was purified by column chromatography using a 9:1 v/v mixture of ethyl acetate and methanol as eluent. There was thus obtained 4-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)-N-phenylsulphonylbenzamide (0.48 g), m.p. 192°C. EXAMPLE 16 Using a similar procedure to that described in Example 15, the appropriate (10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)benzoic acid was reacted with the appropriate benzenesulphonamide to give the compounds described in Table III, the structures of which were confirmed by proton magnetic resonance and mass spectroscopy and by microanalysis. EXAMPLE 17 A mixture of methyl 4-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)-3-nitrobenzoate (0.33 g), stannous chloride (0.58 g) concentrated aqueous hydrochloric acid (5 ml) and diethyl ether (5 ml) was stirred at ambient temperature for 16 hours. The precipitated product was isolated, stirred in a saturated aqueous sodium bicarbonate solution and reisolated. There was thus obtained methyl 3-amino-4-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)benzoate which was used without further purification. The ester so obtained was hydrolysed using a similar procedure to that described in the second paragraph of Example 1. The crude product was triturated under methanol. There was thus obtained 3-amino-4-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)benzoic acid as a monohydrate (0.118 g), m.p. 198-201°C. EXAMPLE 18 The procedures described in Example 1 were repeated except that 8-chloro-10,11-dihydrodibenzo[b,f][1,4]thiazepine ( Coll. Czech. Chem. Comm. , 1959, 24 , 207) was used in place of 8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepine. There was thus obtained 3-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]thiazepin-10-ylmethyl)benzoic acid in 2% yield, m.p. 193-194°C. EXAMPLE 19 The procedures defined in Example 2 were repeated except that 8-chloro-8,11-dihydrodibenzo[b,f][1,4]thiazepine was used in place 8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepine. There was thus obtained 4-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]thiazepin-10-ylmethyl)benzoic acid in 19% yield, m.p. 191-192°C. EXAMPLE 20 Diborane (1M in THF; 12.8 ml) was added to a stirred solution of methyl 4-(11-oxo-10,11-dihydro-5 H -dibenzo[b,e][1,4]diazepin-10-ylmethyl)benzoate (2.3 g) in THF (25 ml). The mixture was stirred and heated to reflux for 8 hours. The mixture was allowed to cool to ambient temperature, 2N aqueous hydrochloric acid solution was added and the mixture was stirred at ambient temperature for 15 minutes. The mixture was extracted with ethyl acetate (3 x 25 ml). The aqueous layer was basified by the addition of 2N aqueous sodium hydroxide solution and extracted with ethyl acetate (25 ml). The organic extracts were combined, washed with a saturated aqueous sodium bicarbonate solution and with brine, dried (MgSO₄) and evaporated. The residue was purified by column chromatography using a 19:1 v/v mixture of methylene chloride and ethyl acetate as eluent. There was thus obtained methyl 4-(10,11-dihydro-5 H -dibenzo[b,e][1,4]diazepin-10-ylmethyl)benzoate (0.62 g) as an oil. A mixture of the product so obtained, 2N aqueous sodium hydroxide solution (6.3 ml), THF (20 ml) and methanol (20 ml) was stirred at ambient temperature for 3 hours. The mixture was evaporated and the residue was acidified to pH4 by the addition of 2N aqueous hydrochloric acid solution. The precipitate so obtained was isolated by filtration and dried. There was thus obtained 4-(10,11-dihydro-5 H -dibenzo[b,e][1,4]diazepin-10-ylmethyl)benzoic acid as a dihydrate containing 1 mole of acetic acid (0.32 g), m.p. 235°C (recrystallised from glacial acetic acid). The methyl 4-(11-oxo-10,11-dihydro-5 H -dibenzo[b,e][1,4]diazepin-10-ylmethyl)benzoate used as a starting material was obtained as follows:- A mixture of 10,11-dihydro-5 H -dibenzo[b,e][1,4]diazepin-11-one ( Synthesis , 1985, 550; 5g) 4-methoxycarbonylbenzyl bromide (5.45 g), tetrabutylammonium hydrogen sulphate (8.1 g), 2N aqueous sodium hydroxide solution (23.8 ml) and methylene chloride (200 ml) was stirred vigorously at ambient temperature for 18 hours. The mixture was washed with water (100 ml). The organic phase was dried (MgSO₄) and evaporated. The residue was purified by column chromatography using increasingly polar mixtures of methylene chloride and ethyl acetate as eluent. There was thus obtained the required starting material (3.15 g). EXAMPLE 21 The procedures described in Example 20 were repeated except that methyl 3-(11-oxo-10,11-dihydro-5 H -dibenzo[b,e][1,4]diazepin-10-ylmethyl)benzoate was used as the starting material. There was thus obtained 3-(10,11-dihydro-5 H -dibenzo[b,e][1,4]diazepin-10-ylmethyl)benzoic acid in 11% yield, m.p. 125-126°C. The appropriate starting material was obtained from 10,11-dihydro-5 H -dibenzo[b,e][1,4]diazepin-11-one and 3-methoxycarbonylbenzyl bromide using an analogous procedure to that described for the preparation of the starting material for Example 20. EXAMPLE 22 A mixture of 5-ethyl-10,11-dihydro-5 H -dibenzo[b,e][1,4]diazepine (1.7 g), 4-methoxycarbonylbenzyl bromide (1.73 g), tetrabutylammonium hydrogen sulphate (2.57 g), 2N aqueous sodium hydroxide solution (7.6 ml) and methylene chloride (20 ml) was stirred vigorously at ambient temperature for 20 hours. The organic phase was washed with water, dried (MgSO₄) and evaporated. The residue was purified by column chromatography using a 4:1 v/v mixture of methylene chloride and hexane as eluent. There was thus obtained methyl 4-(5-ethyl-10,11-dihydro-5 H -dibenzo[b,e][1,4]diazepin-10-ylmethyl)benzoate (1.9 g) as a gum. A mixture of the product so obtained, 2N aqueous sodium hydroxide solution (12.8 ml), THF (20 ml) and methanol (20 ml) was stirred at ambient temperature for 3 hours. The mixture was concentrated to half of its original volume and water (10 ml) was added. The mixture was acifified by the addition of glacial acetic acid. The precipitate so obtained was isolated, dried and recrystallised from glacial acetic acid. There was thus obtained 4-(5-ethyl-10,11-dihydro-5 H -dibenzo[b,e][1,4]diazepin-10-ylmethyl)benzoic acid (1.1 g) m.p. 182-184°C. The 5-ethyl-10,11-dihydro-5 H -dibenzo[b,e][1,4]diazepine used as a starting material was obtained as follows:- Acetic anhydride (4.1 g) was added dropwise to a stirred solution of 10,11-dihydro-5 H -dibenzo[b,e][1,4]diazepin-11-one (9.1 g) in pyridine (50 ml) and the mixture was heated to 100°C for 7 hours. The mixture was evaporated and the residue was purified by column chromatography using a 7:3 v/v mixture of methylene chloride and ethyl acetate as eluent. There was thus obtained 5-acetyl-10,11-dihydro-5 H -dibenzo[b,e][1,4]diazepin-11-one (2.8 g). Lithium aluminium hydride (1M in THF; 48 ml) was added dropwise to a stirred solution of the product so obtained in THF (30 ml) and the mixture was stirred at ambient temperature for 20 hours. The excess of reducing agent was destroyed by the addition of 2N aqueous sodium hydroxide solution (10 ml). The mixture was filtered. The organic phase was dried (MgSO₄) and evaporated. The residue was purified by column chromatography using a 1:1 v/v mixture of hexane and methylene chloride as eluent. There was thus obtained the required starting material (1.7 g), the structure of which was confirmed by proton magnetic resonance spectroscopy. EXAMPLE 23 Using similar procedures to those described in Example 1, 5,6-dihydro-11 H -dibenzo[b,e]azepine ( Tetrahedron , 1981, 37 , 4159) was reacted with 4-methoxycarbonylbenzyl bromide to give 4-(5,6-dihydro-11 H -dibenzo[b,e]azepin-5-ylmethyl)benzoic acid in 45% yield, m.p. 198°C. EXAMPLE 24 The following illustrate representative pharmaceutical dosage forms containing the compound of formula I, or a pharmaceutically-acceptable salt thereof (hereafter compound X), for therapeutic or prophylactic use in humans: (a) Tablet I mg/tablet Compound X 100 Lactose Ph.Eur 182.75 Croscarmellose sodium 12.0 Maize starch paste (5% w/v paste) 2.25 Magnesium stearate 3.0 (b) Tablet II mg/tablet Compound X 50 Lactose Ph.Eur 223.75 Croscarmellose sodium 6.0 Maize starch 15.0 Polyvinylpyrrolidone (5% w/v paste) 2.25 Magnesium stearate 3.0 (c) Tablet III mg/tablet Compound X 1.0 Lactose Ph.Eur 93.25 Croscarmellose sodium 4.0 Maize starch paste (5% w/v paste) 0.75 Magnesium stearate 1.0 (d) Capsule mg/capsule Compound X 10 Lactose Ph.Eur 488.5 Magnesium stearate 1.5 (e) Injection I (50 mg/ml) Compound X 5.0% w/v 1M Sodium hydroxide solution 15.0% v/v 0.1M Hydrochloric acid (to adjust pH to 7.6) Polyethylene glycol 400 4.5% w/v Water for injection to 100% (f) Injection II (10 mg/ml) Compound X 1.0% w/v Sodium phosphate BP 3.6% w/v 0.1M Sodium hydroxide solution 15.0% v/v Water for injection to 100% (g) Injection III (1mg/ml, buffered to pH6) Compound X 0.1% w/v Sodium phosphate BP 2.26% w/v Citric acid 0.38% w/v Polyethylene glycol 400 3.5% w/v Water for injection to 100% (h) Aerosol I mg/ml Compound X 10.0 Sorbitan trioleate 13.5 Trichlorofluoromethane 910.0 Dichlorodifluoromethane 490.0 (i) Aerosol II mg/ml Compound X 0.2 Sorbitan trioleate 0.27 Trichlorofluoromethane 70.0 Dichlorodifluoromethane 280.0 Dichlorotetrafluoroethane 1094.0 (j) Aerosol III mg/ml Compound X 2.5 Sorbitan trioleate 3.38 Trichlorofluoromethane 67.5 Dichlorodifluoromethane 1086.0 Dichlorotetrafluoroethane 191.6 (k) Aerosol IV mg/ml Compound X 2.5 Soya lecithin 2.7 Trichlorofluoromethane 67.5 Dichlorodifluoromethane 1086.0 Dichlorotetrafluoroethane 191.6 Note The above formulations may be obtained by conventional procedures well known in the pharmaceutical art. The tablets (a)-(c) may be enteric coated by conventional means, for example to provide a coating of cellulose acetate phthalate. The aerosol formulations (h)-(k) may be used in conjunction with standard, metered dose aerosol dispensers, and the suspending agents sorbitan trioleate and soya lecithin may be replaced by an alternative suspending agent such as sorbitan monooleate, sorbitan sesquioleate, polysorbate 80, polyglycerol oleate or oleic acid.

Claims: Claims for the following Contracting States : AT, BE, CH, DE, DK, FR, GB, IT, LI, LU, NL, SE A tricyclic heterocycle of the formula I wherein X is oxy, thio, sulphinyl, sulphonyl, amino, (1-4C)alkylamino or methylene, the last named group optionally bearing one or two (1-4C)alkyl groups; Y is carbonyl or methylene, the latter group optionally bearing one or two (1-4C)alkyl groups; each R¹, which may be the same or different, is selected from hydrogen, halogeno, trifluoromethyl, nitro, cyano, hydroxy, amino, (1-4C)alkyl, (1-4C)alkoxy, (1-4C)alkylthio, (1-4C)alkylsulphinyl, (1-4C)alkylsulphonyl, (1-4C)alkylamino and di-(1-4C)alkylamino; m and n, which may be the same or different, is the integer 1 or 2; A¹ is a direct link to Ar, or A¹ is (1-6C)alkylene, (3-6C)alkenylene or (3-6C)alkynylene; A² is a direct link to G; Ar is phenylene which may optionally bear one or two substituents selected from halogeno, trifluoromethyl, nitro, cyano, hydroxy, amino, (1-4C)alkyl, (1-4C)alkoxy, (1-4C)alkylthio, (1-4C)alkylsulphinyl, (1-4C)alkylsulphonyl, (1-4C)alkylamino and di-(1-4C)alkylamino; and G is carboxy, 1H-tetrazol-5-yl or a group of the formula:- -CONH-SO₂R² wherein R² is (1-4C)alkyl, benzyl or phenyl, the latter two of which may optionally bear one or two substituents selected from halogeno, trifluoromethyl, nitro, cyano, hydroxy, (1-4C)alkyl and (1-4C)alkoxy; or when G is carboxy an in-vivo hydrolysable ester thereof or an amide thereof; or a pharmaceutically-acceptable salt thereof. A tricyclic heterocycle of the formula I as claimed in claim 1 wherein X is oxy, thio, amino, methylamino, ethylamino or methylene; Y is methylene optionally bearing one or two methyl or ethyl groups; each R¹, which may be the same or different, is selected from hydrogen, fluoro, chloro, bromo, trifluoromethyl, nitro, cyano, methyl, ethyl, methoxy, ethoxy, methylthio, methylsulphinyl and methylsulphonyl; each of m and n is the integer 1; A¹ is methylene, ethylene, ethylidene, trimethylene, propylidene, propylene, 2-propenylene or 2-propynylene; A² is a direct link to G; Ar is 1,2-phenylene, 1,3-phenylene or 1,4-phenylene which may optionally bear one substituent selected from fluoro, chloro, bromo, trifluoromethyl, nitro, cyano, hydroxy, amino, methyl, ethyl, methoxy and ethoxy; and G is carboxy, 1H-tetrazol-5-yl or a group of the formula:- -CONHSO₂R² wherein R² is methyl, ethyl or phenyl, the last group optionally bearing one substituent selected from fluoro, chloro, trifluoromethyl, nitro, cyano, hydroxy, methyl and methoxy; or when G is carboxy an in-vivo hydrolysable ester thereof; or a pharmaceutically-acceptable salt thereof. A tricyclic heterocycle of the formula I as claimed in claim 1 wherein X is oxy; Y is methylene optionally bearing one or two methyl or ethyl groups; each R¹, which may be the same or different, is selected from hydrogen, fluoro, chloro, bromo, trifluoromethyl, nitro and cyano; each of m and n is the integer 1; A¹ is methylene, ethylene, ethylidene, trimethylene, propylidene or propylene; A² is a direct link to G; Ar is 1,3-phenylene or 1,4-phenylene which may optionally bear one substituent selected from fluoro, chloro, bromo, trifluoromethyl, nitro, cyano, hydroxy, methyl, ethyl, methoxy and ethoxy; and G is carboxy or an in-vivo hydrolysable ester thereof; or a pharmaceutically-acceptable salt thereof. A tricyclic heterocycle of the formula I as claimed in claim 1 wherein X is oxy, thio, amino or methylene; Y is methylene; each R¹, which may be the same or different, is selected from hydrogen, chloro and trifluoromethyl; each of m and n is the integer 1; A¹ is methylene, trimethylene or 2-propenylene; A² is a direct link to G; Ar is 1,3-phenylene or 1,4-phenylene which may optionally bear one substituent selected from fluoro, nitro, hydroxy, amino and methoxy; and G is carboxy or an in-vivo hydrolysable ester thereof; or G is a group of the formula:- -CONHSO₂R² wherein R² is phenyl; or a pharmaceutically-acceptable salt thereof. A tricyclic heterocycle of the formula I as claimed in claim 1 wherein X is oxy; Y is methylene; each R¹, which may be the same or different, is selected from hydrogen, chloro and trifluoromethyl; each of m and n is the integer 1; A¹ is methylene or trimethylene; A² is a direct link to G; Ar is 1,3-phenylene or 1,4-phenylene which may optionally bear one substituent selected from fluoro, nitro, hydroxy, amino and methoxy; and G is carboxy or an in-vivo hydrolysable ester thereof; or a pharmaceutically-acceptable salt thereof. A tricyclic heterocycle of the formula I as claimed in claim 1 wherein X is oxy; Y is methylene; each R¹, which may be the same or different, is selected from hydrogen, fluoro, chloro and trifluoromethyl; each of m and n is the integer 1: A¹ is methylene; A² is a direct link to G; Ar is 1,3-phenylene or 1,4-phenylene; and G is carboxy or an in-vivo hydrolysable ester thereof; or a pharmaceutically-acceptable salt thereof. A tricyclic heterocycle of the formula I, or an in-vivo hydrolysable ester thereof or a pharmaceutically-acceptable salt thereof, as claimed in claim 1 selected from:- 3-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)benzoic acid, 4-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)benzoic acid, 4-[3-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-yl)propyl]benzoic acid, 4-(8-trifluoromethyl-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)benzoic acid and 5-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)-2-hydroxybenzoic acid. A process for the preparation of a tricyclic heterocycle of the formula I, or when G is carboxy an in-vivo hydrolysable ester or an amide thereof, or a pharmaceutically-acceptable salt thereof, as claimed in claim 1 which comprises (a) the coupling of a compound of the formula II with a compound of the formula:- Z-A¹-Ar-A²-G wherein Z is a displaceable group; provided that any hydroxy, amino, alkylamino or carboxy group in these reactants may be protected by a conventional protecting group or alternatively any such group need not be protected, whereafter any such protecting group is removed by conventional means; (b) for the production of a compound of the formula I wherein R¹ is (1-4C)alkylthio or Ar bears a (1-4C)alkylthio substituent, the displacement reaction of a compound of the formula I wherein R¹ is a displaceable substituent Z, or Ar bears a displaceable substituent Z, with a (1-4C)alkylthiol; (c) for the production of a compound of the formula I wherein R¹ is (1-4C)alkylsulphinyl or (1-4C)alkylsulphonyl, or Ar bears a (1-4C)alkylsulphinyl or (1-4C)alkylsulphonyl substituent, the oxidation of a compound of the formula I wherein R¹ is (1-4C)alkylthio or Ar bears a (1-4C)alkylthio substituent; (d) for the production of a compound of the formula I wherein G is 1H-tetrazol-5-yl, the reaction of a nitrile of the formula III with an azide; (e) for the production of a compound of the formula I wherein G is a group of the formula -CONH-SO₂R² the reaction of a compound of the formula I wherein G is carboxy, or a reactive derivative thereof, with a sulphonamide of the formula:- H₂N-SO₂R² provided that any hydroxy, amino or alkylamino group in these reactants may be protected by a conventional protecting group or alternatively any such group need not be protected, whereafter any such protecting group is removed by conventional means; (f) for the production of a compound of the formula I wherein R¹ is (1-4C)alkoxy or Ar bears a (1-4C)alkoxy substituent, the alkylation of a compound of the formula I wherein R¹ is hydroxy or Ar bears a hydroxy substituent; (g) for the production of a compound of the formula I wherein A¹ is (3-6C)alkynylene, the coupling of an alkyne of the formula IV wherein p is an integer from 1 to 4 with a compound of the formula V wherein Z is a displaceable substituent; (h) for the production of a compound of the formula I wherein A¹ is (3-6C)alkenylene or (1-6C)alkylene, the reduction of the corresponding compound wherein A¹ is (3-6C)alkynylene; (i) for the production of a compound of the formula I wherein R¹ is amino or Ar bears an amino substituent, the reduction of a compound of the formula I wherein R¹ is nitro or Ar bears a nitro substituent; or (j) for the production of a compound of the formula I wherein Y is methylene, the reduction of a compound of the formula I wherein Y is carbonyl; and when an in-vivo hydrolysable ester of a compound of the formula I wherein G is carboxy is required, it may be obtained by reaction of said compound of the formula I wherein G is carboxy, or a reactive derivative thereof, with a suitable esterifying reagent using a conventional procedure; when an amide of a compound of the formula I wherein G is carboxy is required, it may be obtained by reaction of said compound of the formula I wherein G is carboxy, or a reactive derivative thereof, with a suitable amine using a conventional procedure; and when a pharmaceutically-acceptable salt of a compound of the formula I is required, it may be obtained by reaction of said compound with a suitable acid or base using a conventional procedure. A pharmaceutical composition which comprises a tricyclic heterocycle of the formula I, or when G is carboxy an in-vivo hydrolysable ester thereof or an amide thereof, or a pharmaceutically-acceptable salt thereof, as claimed in any one of claims 1 to 7 in association with a pharmaceutically-acceptable diluent or carrier. Claims for the following Contracting States : GR, ES A process for the preparation of a tricyclic heterocycle of the formula I wherein X is oxy, thio, sulphinyl, sulphonyl, amino, (1-4C)alkylamino or methylene, the last named group optionally bearing one or two (1-4C)alkyl groups; Y is carbonyl or methylene, the latter group optionally bearing one or two (1-4C)alkyl groups; each R¹, which may be the same or different, is selected from hydrogen, halogeno, trifluoromethyl, nitro, cyano, hydroxy, amino, (1-4C)alkyl, (1-4C)alkoxy, (1-4C)alkylthio, (1-4C)alkylsulphinyl, (1-4C)alkylsulphonyl, (1-4C)alkylamino and di-(1-4C)alkylamino; m and n, which may be the same or different, is the integer 1 or 2; A¹ is a direct link to Ar, or A¹ is (1-6C)alkylene, (3-6C)alkenylene or (3-6C)alkynylene; A² is a direct link to G; Ar is phenylene which may optionally bear one or two substituents selected from halogeno, trifluoromethyl, nitro, cyano, hydroxy, amino, (1-4C)alkyl, (1-4C)alkoxy, (1-4C)alkylthio, (1-4C)alkylsulphinyl, (1-4C)alkylsulphonyl, (1-4C)alkylamino and di-(1-4C)alkylamino; and G is carboxy, 1H-tetrazol-5-yl or a group of the formula:- -CONH-SO₂R² wherein R² is (1-4C)alkyl, benzyl or phenyl, the latter two of which may optionally bear one or two substituents selected from halogeno, trifluoromethyl, nitro, cyano, hydroxy, (1-4C)alkyl and (1-4C)alkoxy; or when G is carboxy an in-vivo hydrolysable ester thereof or an amide thereof; or a pharmaceutically-acceptable salt thereof; characterised by (a) the coupling of a compound of the formula II with a compound of the formula:- Z-A¹-Ar-A²-G wherein Z is a displaceable group; provided that any hydroxy, amino, alkylamino or carboxy group in these reactants may be protected by a conventional protecting group or alternatively any such group need not be protected, whereafter any such protecting group is removed by conventional means; (b) for the production of a compound of the formula I wherein R¹ is (1-4C)alkylthio or Ar bears a (1-4C)alkylthio substituent, the displacement reaction of a compound of the formula I wherein R¹ is a displaceable substituent Z, or Ar bears a displaceable substituent Z, with a (1-4C)alkylthiol; (c) for the production of a compound of the formula I wherein R¹ is (1-4C)alkylsulphinyl or (1-4C)alkylsulphonyl, or Ar bears a (1-4C)alkylsulphinyl or (1-4C)alkylsulphonyl substituent, the oxidation of a compound of the formula I wherein R¹ is (1-4C)alkylthio or Ar bears a (1-4C)alkylthio substituent; (d) for the production of a compound of the formula I wherein G is 1H-tetrazol-5-yl, the reaction of a nitrile of the formula III with an azide; (e) for the production of a compound of the formula I wherein G is a group of the formula -CONH-SO₂R² the reaction of a compound of the formula I wherein G is carboxy, or a reactive derivative thereof, with a sulphonamide of the formula:- H₂N-SO₂R² provided that any hydroxy, amino or alkylamino group in these reactants may be protected by a conventional protecting group or alternatively any such group need not be protected, whereafter any such protecting group is removed by conventional means; (f) for the production of a compound of the formula I wherein R¹ is (1-4C)alkoxy or Ar bears a (1-4C)alkoxy substituent, the alkylation of a compound of the formula I wherein R¹ is hydroxy or Ar bears a hydroxy substituent; (g) for the production of a compound of the formula I wherein A¹ is (3-6C)alkynylene, the coupling of an alkyne of the formula IV wherein p is an integer from 1 to 4 with a compound of the formula V wherein Z is a displaceable substituent; (h) for the production of a compound of the formula I wherein A¹ is (3-6C)alkenylene or (1-6C)alkylene, the reduction of the corresponding compound wherein A¹ is (3-6C)alkynylene; (i) for the production of a compound of the formula I wherein R¹ is amino or Ar bears an amino substituent, the reduction of a compound of the formula I wherein R¹ is nitro or Ar bears a nitro substituent; or (j) for the production of a compound of the formula I wherein Y is methylene, the reduction of a compound of the formula I wherein Y is carbonyl; and when an in-vivo hydrolysable ester of a compound of the formula I wherein G is carboxy is required, it may be obtained by reaction of said compound of the formula I wherein G is carboxy, or a reactive derivative thereof, with a suitable esterifying reagent using a conventional procedure; when an amide of a compound of the formula I wherein G is carboxy is required, it may be obtained by reaction of said compound of the formula I wherein G is carboxy, or a reactive derivative thereof, with a suitable amine using a conventional procedure; and when a pharmaceutically-acceptable salt of a compound of the formula I is required, it may be obtained by reaction of said compound with a suitable acid or base using a conventional procedure. A process as claimed in claim 1 for the preparation of a tricyclic heterocycle of the formula I wherein X is oxy, thio, amino, methylamino, ethylamino or methylene; Y is methylene optionally bearing one or two methyl or ethyl groups; each R¹, which may be the same or different, is selected from hydrogen, fluoro, chloro, bromo, trifluoromethyl, nitro, cyano, methyl, ethyl, methoxy, ethoxy, methylthio, methylsulphinyl and methylsulphonyl; each of m and n is the integer 1; A¹ is methylene, ethylene, ethylidene, trimethylene, propylidene, propylene, 2-propenylene or 2-propynylene; A² is a direct link to G; Ar is 1,2-phenylene, 1,3-phenylene or 1,4-phenylene which may optionally bear one substituent selected from fluoro, chloro, bromo, trifluoromethyl, nitro, cyano, hydroxy, amino, methyl, ethyl, methoxy and ethoxy; and G is carboxy, 1H-tetrazol-5-yl or a group of the formula:- -CONHSO₂R² wherein R² is methyl, ethyl or phenyl, the last group optionally bearing one substituent selected from fluoro, chloro, trifluoromethyl, nitro, cyano, hydroxy, methyl and methoxy; or when G is carboxy an in-vivo hydrolysable ester thereof; or a pharmaceutically-acceptable salt thereof. A process as claimed in claim 1 for the preparation of a tricyclic heterocycle of the formula I wherein X is oxy; Y is methylene optionally bearing one or two methyl or ethyl groups; each R¹, which may be the same or different, is selected from hydrogen, fluoro, chloro, bromo, trifluoromethyl, nitro and cyano; each of m and n is the integer 1; A¹ is methylene, ethylene, ethylidene, trimethylene, propylidene or propylene; A² is a direct link to G; Ar is 1,3-phenylene or 1,4-phenylene which may optionally bear one substituent selected from fluoro, chloro, bromo, trifluoromethyl, nitro, cyano, hydroxy, methyl, ethyl, methoxy and ethoxy; and G is carboxy or an in-vivo hydrolysable ester thereof; or a pharmaceutically-acceptable salt thereof. A process as claimed in claim 1 for the preparation of a tricyclic heterocycle of the formula I wherein X is oxy, thio, amino or methylene; Y is methylene; each R¹, which may be the same or different, is selected from hydrogen, chloro and trifluoromethyl; each of m and n is the integer 1; A¹ is methylene, trimethylene or 2-propenylene; A² is a direct link to G; Ar is 1,3-phenylene or 1,4-phenylene which may optionally bear one substituent selected from fluoro, nitro, hydroxy, amino and methoxy; and G is carboxy or an in-vivo hydrolysable ester thereof; or G is a group of the formula:- -CONHSO₂R² wherein R² is phenyl; or a pharmaceutically-acceptable salt thereof. A process as claimed in claim 1 for the preparation of a tricyclic heterocycle of the formula I wherein X is oxy; Y is methylene; each R¹, which may be the same or different, is selected from hydrogen, chloro and trifluoromethyl; each of m and n is the integer 1; A¹ is methylene or trimethylene; A² is a direct link to G; Ar is 1,3-phenylene or 1,4-phenylene which may optionally bear one substituent selected from fluoro, nitro, hydroxy, amino and methoxy; and G is carboxy or an in-vivo hydrolysable ester thereof; or a pharmaceutically-acceptable salt thereof. A process as claimed in claim 1 for the preparation of tricyclic heterocycle of the formula I wherein X is oxy; Y is methylene; each R¹, which may be the same or different, is selected from hydrogen, fluoro, chloro and trifluoromethyl; each of m and n is the integer 1: A¹ is methylene; A² is a direct link to G; Ar is 1,3-phenylene or 1,4-phenylene; and G is carboxy or an in-vivo hydrolysable ester thereof; or a pharmaceutically-acceptable salt thereof. A process as claimed in claim 1 for the preparation of a tricyclic heterocycle of the formula I, or an in-vivo hydrolysable ester thereof or a pharmaceutically-acceptable salt thereof, selected from:- 3-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)benzoic acid, 4-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)benzoic acid, 4-[3-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-yl)propyl]benzoic acid, 4-(8-trifluoromethyl-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)benzoic acid and 5-(8-chloro-10,11-dihydrodibenzo[b,f][1,4]oxazepin-10-ylmethyl)-2-hydroxybenzoic acid. A process for the preparation of a pharmaceutical composition which comprises bringing into admixture a tricyclic heterocycle of the formula I, or when G is carboxy an in-vivo hydrolysable ester thereof or an amide thereof, or a pharmaceutically-acceptable salt thereof, as defined in any one of claims 1 to 7 and a pharmaceutically-acceptable diluent or carrier. The use of a tricyclic heterocycle of the formula I, or when G is carboxy an in-vivo hydrolysable ester thereof or an amide thereof, or a pharmaceutically-acceptable salt thereof, as defined in any one of claims 1 to 7 in the manufacture of a medicament for use in the production of an anti-hyperalgesic effect in the human or animal body.

Inventors: TUCKER HOWARD, TUCKER, HOWARD
Applicants: ZENECA LTD, ZENECA LIMITED
Application year: 1991
Main classification: C07D223
IPC codes: C07D281, C07D413, A61K31, A61P25, C07D243, A61P43, C07D267, C07D223