NOVEL 2,6-DISUBSTITUTED PURINE DERIVATIVES

Abstract: A compound of formula (I), or a pharmaceutically acceptable salt thereof wherein X is halogen, perhalomethyl, cyano, C1-6-alkoxy, C1-6-alkylthio or C1-6-alkylamino; R<1> is selected from optionally substituted N &cir& _-bonded heterocyclics. The compounds have been found useful for treating central nervous system ailments.

Description: Novel 2,6-disubstituted purine derivatives The present invention relates to modified 6-hydrazino-9- (β-D-ribofuranosyl)-(9H)-purines further substituted at the 2-position and pharmaceutically acceptable addition salts thereof having certain very desirable central nervous system properties, processes for their prepara¬ tion and their pharmaceutical compositions as well as methods for using the compounds and compositions described. Background of the Invention Adenosine can be considered to be a hormone which has been shown to have a number of significant effects on the mammalian central nervous system (CNS) [see, for example, Adenosine in the Nervous System (in the series Neuro- science Perspectives, Series Editor Jenner, P.) Stone, T. . , Ed., Academic Press Ltd., London, 1991, Annual Reports in Medicinal Chemistry, 1988, 23, 39-48; Inter¬ national Review of Neurobiology (Smythies, J.R. and Bradley, R.J. , eds.) Academic Press Inc., 1985, 27, 63- 139.], especially under conditions of neuronal stress where the compound appears to act as an endogenous neuro- protectant (Progress in Neurobiology, 1988, 31, 85-108, Trends in Pharmacological Sciences, 1988, 9, 193-194). For example, the concentration of adenosine has been demonstrated to rise greatly in certain brain regions following epileptic seizures or conditions of neuronal ischaemia/anoxia, (Brain Research 1990, 516, 248-256). It has been established for some years now that centrally acting adenosine receptor agonists or compounds which increase extracellular adenosine levels can exhibit what is termed neuro odulator activity. Such substances influ ence the release of neurotransmitters in regions of the central nervous system (Annual Review of Neuroscience, 1985 r 8, 103-124; Trends in Neurosciences, 1984, 164- 168) , with particular inhibitory effects on the release of the excitatory amino acid glutamic acid (glutamate) (Nature, 1985, 316, 148-150, Journal of " Neurochemistry, 1992, 58, 1683-169). There are several CNS ailments in which this adenosine receptor mediated neuromodulator activity may be of clear therapeutic benefit. Examples of these would include the treatment of convulsive disorders (European Journal of Pharmacology, 1991, 195, 261-265; Journal of Pharmacology and Experimental Therapeutics, 1982, 220, 70-76), preven¬ tion of neurodegeneration under conditions of brain anoxia/ischaemia (Neuroscience, 1989, 3Θ, 451-462; Neuroscience Letters, 1987, 83, 287-293; Medical Hy¬ potheses, 1990, 32 r 45-49, Pharmacology of Cerebral Ischaemia 1990 (Kriegelstein, J. and Oberpichler, H. , Eds., issenschaftliche Verlagsgesellschaft mbH: Stutt¬ gart, 1990, pp 439-448) or the use of a urinergic agent in the treatment of pain (European Journal of Pharma¬ cology, 1989, 162, 365-369; Neuroscience Letters, 1991, 121, 267-270) . The relevance of adenosine and adenosine agonists to all these disease areas has recently been reviewed in Adenosine and Adenine Nucleotides as Regula¬ tors of Cellular Function (Phyllis, J.W. , Ed., CRC Press Inc: Boca Raton, Florida, 1991, pp 319 - 400) . Adenosine receptors represent a subclass (P.,) of the group of purine nucleotide and nucleoside receptors known as purinoreceptors. This subclass has been further clas¬ sified into two distinct receptor types which have become known as Al and A2. Extensive research has been curried out in a quest to identify selective ligands at these sites [see, for example. Comprehensive Medicinal Chemi- stry. Volume 3, (Hansch, C. , Sa mes, P.G. and Taylor, J.B., Pergamon Press PLC, 1990, 601-642)]. Selective ligands exist for Al and A2 adenosine receptor and the structure-activity relationships of the various reference ligands have been reviewed (Biochemical Pharma cology, 1986, 35, 2467-2481) together with their thera¬ peutic potential (Journal of Medicinal Chemistry, 1992, 35, 407-422). Among the known adenosine receptor agonist most selective for the Al receptor over the A2 receptor are the examples where the adenine nucleus is substitute with a cycloalkyl group on the amino function, for example N-cyclopentyladenosine and N-cyclohexyladenosine (Journal of Medicinal Chemistry, 1985, 28, 1383-1384) or 2-chloro-N-cyclopentyladenosine (Naunyn-Schmiedeberg's Arch. Pharmacol. 1988, 337, 687-689). Examples of adenosine derivatives in the chemical litera¬ ture having a nitrogen bonded directly to the 6-amino substituent are few in number, and are summarised below. They include N-aminoadenosine, N-[ (N-methyl-N-phenyl)- amino]adenosine (Journal of Medicinal Chemistry, .1985, 28, 1636-1643); N-(methylamino)adenosine and N-[(N- hydroxy-N-methyl)amino]adenosine (Journal of Medicinal Chemistry, 1968, 11, 521-523); 2-amino-N-aminoadenosine (Chemical and Pharmaceutical Bulletin, 1969, 17, 2373- 2376) ; 2-fluoro-N-aminoadenosine (Journal of Medicinal Chemistry, 1970, 13, 427-430) and 2-fluoro-N-methoxy- adenosine (Journal of Medicinal Chemistry, 1971, 14, 816- 819) . Finally, there is one example containing a cyclic amine, namely 2-amino-N-piperidinyladenosine (Arznei- mittel-Forschung, 1970, 20, 1749-1751). In the above scientific articles, no mention is made of any pharmacological effects of the compounds concerned on the central nervous system. In US Patent No. 3,819,613, substituted adenosine ana¬ logues with hydrazone derivatives on the 6-amino functio are disclosed as hypotensive agents. In GB Patent No. 1,351,501, adenosine and 2-aminoadenosine derivatives having a -NH-R 2 group joined to the 6-amino function are disclosed as coronary dilators and platelet aggregation inhibitors. In EP Publication No. 152,944A, a series of 2-, 6- and 8- substituted adenosine derivatives are described having activity as anti-allergy agents. In EP Publication No. 253,962A, adenosine and 2-haloadenosine analogues having an alkyl, cycloalkyl or an aralkyl grou attached to the 6-amino function are described with ac¬ tivity as antidementia agents. In EP Publication No. 402,752A, derivatives of adenosine unsubstituted in the 2-position are described which have a substituted heteroaromatic 1-pyrrolyl moiety attached to the 6-amino group. In PCT Publication No. WO 91/04032, methods of preventing neural tissue damage in neuro- degenerative diseases by increasing extracellular concen¬ trations of adenosine are described. Examples are given of prodrug esters of AICA riboside which are claimed to be centrally acting neuroprotective agents. In PCT Publi¬ cation No. WO 92/02214, analogues of AICA riboside are described which increase extracellular adenosine levels with beneficial effects claimed in peripheral and CNS ischaemia. In PCT Publication No. WO 90/05526, 2-(alkyl- alkynyl)adenosine derivatives are described for treatment of ischaemic disease of the heart and brain. In EP Publi- cation No. 0 423 777 A2 a method for treating gastro¬ intestinal motility disorders using N(6) (substituted aminoalkyl) adenosine derivatives is disclosed. EP Pub¬ lication No. 0 490 818 Al describes a new use of 2'-0- methyl adenosine derivatives for a range of ailments including neurodegenerative disorders. The present invention relates to new adenosine analogues having remarkably potent binding in vitro to the adenosine Al receptor and at the same time showing selec tivity for Al receptor binding in vitro over that of the A2 receptor subtype. In addition, the compounds containe in this invention have a relatively high lipophilicity, especially when compared to adenosine analogues which ar not substituted on the 6-amino group or the purine 2- position. This latter property makes these compounds suitable for passage across the blood brain barrier, and supports the suggestion that the compounds may be candi¬ date drugs for the CNS ailments mentioned within this invention. The possibility that some of the compounds may be sub- strates for nucleoside-specific active transport systems across the blood barrier is, however, not excluded. Thes useful properties support the suggestion that the com¬ pounds may be candidate drugs for the CNS ailments men¬ tioned above in humans. There are instances where it has been demonstrated that co-administration of a periph¬ erally active adenosine receptor antagonist can lower th expected side effects on the cardiovascular system when an adenosine agonist is used as a neuroprotectant in animal models (Journal of Molecular-Neuroscience, 1990, 2, 53-59). This method of lowering side-effects is also applicable during the therapeutic use of the adenosine receptor agonists covered by the present invention. The novel compounds of the invention are purine deriva- tives of formula (I) , or a pharmaceutically acceptable salt thereof: wherein X is halogen, perhalomethyl, cyano, C-^-alkoxy, C-. 6 - alkylthio or c^-alkylamino; R 1 is selected from the groups consisting of wherein n is l to 3 and where the group (a) may be op¬ tionally substituted with one or two C^-alkyl groups, C 2 . 6 -alkenyl, C 2 . 6 -alkynyl, phenoxy, phenylsulphonyl, phenylthio, hydroxy, phenyl, C^-alkoxy or C^-alkoxy- C.. 6 -alkyl, phenylthioalkyl or wherein Y is 0, S or NZ, where Z is H, c 1 . 6 -alkyl or phenyl, and where the group (b) may be optionally substi¬ tuted with C^-alkyl, C 2 . 6 -alkenyl, C 2 . 6 -alkyny1, phenoxy, phenyl, C^-alkoxy or C 1 . 6 -alkoxy-C 1 . 6 -alkyl, or which may be optionally substituted with C^-alkyl, C 2 . 6 - alkenyl, C 2 . 6 -alkynyl, phenoxy, phenylthio, phenyl, C-,. 6 - alkoxy or C-. g -alkoxy-C^-alkyl. In certain examples, the group R 1 can contain one or mor asymmetric carbon atoms in addition to those asymmetric centres already present in the molecule. In examples where this is the case, this invention includes all re¬ sulting diastereoisomers and mixtures thereof. Various salts of compounds of formula (I) can be prepare which can be considered physiologically acceptable. Thes include addition salts derived from inorganic or organic acids, for example, acetates, fumarates, glutarates, glutaconates, lactates, maleates, methanesulphonates, phosphates, salicylates, succinates, sulphates, sulpha- mates, tartrates and paratoluenesulphonates. In some cases, solvates of either the free nucleosides or the acid addition salts can be isolated and these solvates may, for example, be hydrates or alcoholates. Compounds of formula (I) , which act as adenosine receptor agonists, are found to be useful in the treatment of central nervous system conditions such as anxiety, neuronal ischaemia/anoxia, convulsive disorders (epi¬ lepsy) and neurodegeneration (including Parkinson-'s disease) . This includes treating disorders where the blood flow to the brain is interrupted, for example during traumatic head injury, cardiac arrest and stroke. Further, the compounds of formula (I) are found to be useful as analgesic agents, in lowering plasma FFA levels or as cardiovascular agents. The invention also relates to methods of preparing the above mentioned compounds. These methods comprise: Method A A compound of formula (I) may be prepared by reacting a substance of formula (II) , wherein L represents a leavin group such as a halogen atom (e.g. a chlorine or bromine atom) or a trimethylsilyloxy group, R 2 and R 3 are the same or different and represent hydrogen or a protecting group such as benzoyl-, p-toluoyl-, lower alkanoyl- (e.g. acetyl-) , a 2,3-0-(l-methyl)ethylidene group or a sub¬ stituted silyl group (e.g. a trimethylsilyl or t-butyl- dimethylsilyl group) with a hydrazine derivative of general formula (III) HO OH giving the compound of formula (IV) as the reaction product. In cases where R z and R 3 are not hydrogen an additional step will be required to remove protecting groups from (IV) ; in cases where the groups R 2 and R 3 are for example acetyl or benzoyl, suitable conditions for deprotection include methanolic ammonia, an alkali metal carbonate in methanol, an alkali metal alkoxide in the corresponding alcohol. Where the protecting groups are for example alkylsilicon or arylsilicon derivatives, suitable deprotection methods include for example treat- ment with tetraalkylammonium fluorides or aqueous hydro¬ lysis in the presence of acid or base. Method B A compound of formula (I) (wherein X represents -NH-R 4 , or -O-R 4 , where R 4 is 0,^-alkyl) may be prepared by react¬ ing a substance of general formula (V) (where L is a leaving group as defined in method (A) ) with a nucleophile, for example C 1 . 6 -alkylamino (optional¬ ly in the presence of a suitable base) or with the anion (C 1 . 6 -alkoxide or C^-thioalkoxide) to afford the product (IV) . In cases where R 2 and R 3 are hydrogen, compound (I) can be obtained directly. However, in cases where R 2 and R 3 are not hydrogen an additional step will be involved to remove protecting groups from (IV) ; examples of condi¬ tions for removal of protecting groups are given in process (A) . In some reactions involving (V) with the anion (C^-alkoxide or C 1 . 6 -thioalkoxide) , where R 2 and R 3 are for example acetyl- or benzoyl-, partial or full deprotection may take place. In cases where only partia deprotection has taken place, deprotection can be com¬ pleted under conditions exemplified in method (A) . Method C A compound of formula (I) may be prepared by reacting a substance of the general formula (VI) (where B represent -NH-R 1 or L as defined previously) with a diazotising agent (such as, for example, 3-methylbutyl nitrite) to form an intermediate species which can be reacted furthe with a variety of substrates as exemplified below in order to introduce the group -X into the product (VII) . In the case where B represents a leaving group L, a further displacement reaction with for example ("II) will be required in order to obtain the product (IV) . In cases where the groups R 2 and R 3 are not hydrogen, or not all hydrogen, another step will be required to remove pro¬ tecting groups from (IV) ; conditions for removing pro¬ tecting groups are described in method A. Methods for assessing adenosine receptor binding in vitr have been reviewed [Adenosine Receptors, (Cooper, D.M.F. and Londos, C. , eds.) Alan R. Liss, Inc., New York, 1988, 43-62]. Evaluation of these compounds in established animal models has indicated that the compounds according to the invention possess desirable central nervous system prop¬ erties. For example, they act as anticonvulsant agents, are effective in animal models of pain, and show cerebro- protective effects in laboratory test animals subjected to simulated cerebral ischaemia. In addition, the com¬ pounds may have efficacy as neuroprotective agents in cases of cerebral oedema and traumatic head injury. Evaluation of .in vitro binding to adenosine Al and A2 receptors The affinity of the novel compounds described in this invention for the adenosine Al receptor was determined essentially as described in the literature using [ 3 H]-L- PIA as a radioligand (Naunyn-Schmiedeberg's Archives of Pharmacology, 1980, 313, 179-187). Affinity for the A2 receptor was measured using the radioligand [ 3 H]-CGS 21680 (European Journal of Pharmacology, 1989, 168, 243- 246), and the values for representative compounds is given in the table below. Jn vitro receptor binding values obtained for the reference standards CPA [N- (cyclopentyl)adenosine] and L-PIA [N-(l-phenyl-2- propyl)adenosine] are included for comparison. DMCM INDUCED SEIZURES IN MICE. I.P.30 min. Method description DMCM, 15 m /kα. i.p. r clonic convulsions RATIONALE DMCM is an inverse agonist at the benzodiazepine recep- tor, presumably producing seizures by decreasing the potency of inhibition of the GABA receptor/benzodiazepi receptor/chloride ionophore complex (1) . METHODS 15 mg/kg of DMCM dissolved in 0.02 N HC1 (1 mg/ml) is administered i.p. in a volume of 300 μl to male NMRI mic weighing 20 + 2 g. This induces two different responses: a) some animals manifest a brief loss of righting reflexes or take up an upright position in which they have a mild short clonus of the upper extremities, b) other animals manifest intense clonic and tonic convul¬ sions of all extremities often followed by death. DMCM i administered 30 min. after an intraperitoneal injection of a test compound. The latency time for the presence of intense clonic and tonic convulsions and death is noted until 15 min. after administration of DMCM. At least 5 doses of each test compound are tested with 8 mice per dose. RESULTS An anticonvulsive ED 50 value is determined as the dose (mg/kg) protecting 50% of the animals against clonic convulsions. This method is described in more detail in Eur. J. Pharmacol. 94, 117-124, 1983. The results obtained by testing compounds disclosed in the present invention are shown in the following table I. TABLE I The compounds of the invention, together with a conven¬ tional adjuvant, carrier, or diluent, and if desired in the form of a pharmaceutically acceptable acid addition salt thereof, may be placed into the form of pharmaceuti¬ cal compositions and unit dosages thereof, and in such form may be employed as solids, such as tablets of filled capsules, or liquids, such as solutions, suspensions, emulsions, elixirs, or capsules filled with the same, all for oral use, in the form of suppositories for rectal administration; or in the form of sterile injectable solutions for parenteral use (including subcutaneous administration and infusion) . Such pharmaceutical compo¬ sitions and unit dosage forms thereof may comprise con- ventional ingredients in conventional proportions, with or without additional active compounds or principles, and such unit dosage forms may contain any suitable effective amount of the adenosine receptor agonist commensurate with the intended daily dosage range to be employed. Tablets containing ten (10) milligrams of active ingredi ent or, more broadly, ten (10) to hundred (100) milli- grams, per tablet, are accordingly suitable representa¬ tive unit dosage forms. The compounds of this invention can thus be used for the formulation of pharmaceutical preparation, e.g. for oral and parenteral administration to mammals including hu¬ mans, in accordance with conventional methods of galenic pharmacy. Conventional excipients are such pharmaceutically accep- table organic or inorganic carrier substances suitable for parenteral or enteral application which do not dele- teriously react with the active compounds. Examples of such carriers are water, salt solutions, alcohols, polyethylene glycols, polyhyroxyethoxylated castor oil, gelatine, lactose, amylose, magnesium stea- rate, talc, silicic acid, fatty acid monoglycerides and diglycerides, pentaerythritol fatty acid esters, hydroxy- methylcellulose and polyvinylpyrrolidone. The pharmaceutical preparations can be sterilized and mixed, if desired, with auxiliary agents, emulsifiers, salt for influencing osmotic pressure, buffers and/or colouring substances and the like, which do not dele- teriously react with the active compounds. For parenteral application, particularly suitable are injectable solutions or suspensions, preferably aqueous solutions with the active compound dissolved in polyhy- droxylated castor oil. Ampoules are convenient unit dosage forms. Tablets, dragees, or capsules having talc and/or a carbo¬ hydrate carrier or binder or the like, the carrier pre¬ ferably being lactose and/or corn starch and/or potato starch, are particularly suitable for oral application. A syrup, elixir or the like can be used in cases where a sweetened vehicle can be employed. Generally, the compounds of this invention are dispensed in unit form comprising 0.05-100 mg in a pharmaceutically acceptable carrier per unit dosage. The dosage of the compounds according to this invention is 0.1-300 mg/day, preferably 10-100 mg/day, when admini¬ stered to patients, e.g. humans, as a drug. A typical tablet which may be prepared by conventional tabletting techniques contains: Active compound 5.0 mg Lactosum 67.0 mg Ph.Eur. Avicel TH 31.4 mg Amberlite™IRP 88 1.0 mg Magnesii stearas 0.25 mg Ph.Eur. As a result of their activity against pain or convulsive disorders and prevention of neurodegeneration under conditions of anoxia/ischaemia the compounds of the invention are extremely useful in the treatment of related symptoms in mammals, when administered in an amount effective for agonist activity of compounds of the invention. The compounds of the invention may accordingly be administered to a subject, e.g., a living animal body, including a human, in need of adenosine receptor agonist, and if desired in the form of a pharmaceutically accept- able acid addition salt thereof (such as the hydro- bromide, hydrochloride, or sulphate, in any event pre¬ pared in the usual or conventional manner, e.g., evapor- ation to dryness of the free base in solution together with the acid) , ordinarily concurrently, simultaneously, or together with a pharmaceutically acceptable carrier diluent, especially and preferably in the form of a pharmaceutical composition thereof, whether by oral, rectal, or parenteral (including subcutaneous) route, in an effective amount of adenosine receptor agonist, and i any event an amount which is effective for the treatment of anoxia, traumatic injury, ischaemia, migraine or othe pain symptoms, epilepsy, or neurodegenerative diseases owing to their adenosine receptor agonist activity. Suitable dosage ranges are 1-200 milligrams daily, 10-10 milligrams daily, and especially 30-70 milligrams daily, depending as usual upon the exact mode of administration form in which administered, the indication toward which the administration is directed, the subject involved and the body weight of the subject involved, and the pre¬ ference and experience of the physician or veterinarian in charge. The preparation of compounds of formula (I) and prepara¬ tions containing them is further illustrated in the following examples. Hereinafter, TLC is thin layer chromatography, THF is tetrahydrofuran, TFA is trifluoracetic acid and m.p. is melting point. Where melting points are given, these are uncorrected. The structures of the compounds are con¬ firmed by assignment of NMR spectra (from which represeπ- tative peaks are quoted) and by microanalysis where appropriate. Compounds used as starting materials are either known compounds or compounds which can be prepared by methods known per se. Column chromatography was carried out using the technique described by Still, W.C. et al., Journal of Organic Chemistry, 1978, 43, 2923 on Merck silica gel 60 (Art 9385) . HPLC was carried out on a Waters model 510 chromatograph interfaced via a system module to a Waters 490 multiwavelength detector to a reversed phase C 18 column (250 x 4 mm, 5μm, lOOA; eluent flow rate 1 mL/min. at 35°C) . Retention times are given in minutes. EXAMPLE 1 (Method A) 2-Chloro-N-(4-morpholinyl)adenosine 2,6-Dichloro-9(H)-purine (5.8 g, 30.7 mmol) and 1-0- acetyl-2,3,5-tri-0-benzoyl-D-ribofuranose (16.26 g, 32. mmol) were thoroughly mixed and fused together at 145- 150°C under oil pump vacuum. The resultant gummy mixtur was stirred gently for 0.75 hours (during which time th acetic acid by-product evaporated) , cooled to ca. 50°C and dissolved in dichloromethane (100 ml) with stirring. This solution was applied directly to a column of silica gel (6 x 22 cm) and eluted initially with cyclohexane/di chloromethane (1/1) , then with dichloromethane and final ly with cyclohexane/ethyl acetate (1/1) to provide 2,6- dichloro-2,3,5-tri-O-benzoyl-β-D-ribofuranosyl-(9H)- purine (16.6 g, 87%) as a colourless foam, TLC r f 0.50 [Si0 2 , cyclohexane/ethyl acetate (1/1)]. 1 H NMR (400 MHz, CDCl j ) δ 4.72 (IH, dd, H-5' a ) , 4.88 (IH, q, H-4'), 4.93 (IH, dd, H-5' b ), 6.15 (2H, m, H-2' & H-3'), 6.50 (IH, d, H-l'), 7.34 - 7.65 (9H, , m- & p-ArH) , 7.90 - 8.13 (6H, , o-ArH) , 8.28 (IH, s, H-8). (This method of preparatio is similar to the one described by Imai, K-i. et al. , Chemical and Pharmaceutical Bulletin, 1966, 14, 1377- 1381, but without the use of a catalyst) . The above 2,6-dichloro-2,3,5-tri-O-benzoyl-β-D-ribo- furanosyl-(9H)-purine (1.26 g, 2 mmol) and 4-amino- orpholine (0.89 g, 8.8 mmol) were dissolved in a mixture of dioxan (30 ml) and toluene (15 ml). The solution was heated at 50°C for 20 hours, after which time it was confirmed that the starting material was consumed and a new product was observed with TLC r f 0.20 [Si0 2 , ethyl acetate/dichloromethane (4/1)]. The cooled reaction mixture was evaporated to a gum and coevaporated with methanol (20 ml). Dried potassium carbonate (0.55 g, 4 mmol) and methanol were added and stirring was continued for 20 hours, whereupon acetic acid (1.0 ml) was intro¬ duced. The reaction mixture was evaporated and the resi¬ due was coevaporated with toluene (30 ml) before purifi¬ cation by column chromatography on silica gel (2.5 x 20 cm) . Elution with dichloromethane initially, gradually increasing the polarity of the eluent to a mixture of dichloromethane/ethanol/25% aqueous ammonia solution (100/10/1) provided the title compound (0.43 g, 55%) as semi-solid foam, TLC r f 0.24 [Si0 2 , dichloromethane/etha- nol/25% aqueous ammonia solution (60/10/1) , 1 H NMR (400 MHz, Me 2 SO-d 6 ) δ 3.56 (IH, m, H-5'a) , 3.67 (IH, m, H- 5'b), 3.95 (IH, q, H-4'), 4.14 (IH, m, H-3') , 4.51 (IH, q, H-2'), 5.84 (IH, d, H-l'), 8.43 (IH, s, H-8). This nucleoside could be recrystallised from ethyl acetate/ trace ethanol to provide an analytical sample (0.3 g) as a white solid, m.p. 160-161°C (after drying in vacuo) . C H 19 N 6 C10 5 . H 2 0 requires C, 41.5; H, 5.2; N, 20.75; Cl, 8.75%. Found: C, 41.7; H, 5.35; N, 20.3; Cl, 8.6%. EXAMPLE 2 2-Chloro-N-[1-(2,3,4,5,6,7-hexahydro)azepinyl]adenosine The title compound was prepared according to method A as described in Example 1 and obtained as a foam (0.12 g, 62% from 2,6-dichloro-2,3,5-tri-O-benzoyl-β-D-ribo- furanosyl-(9H)-purine) ; 1 H NMR (400 MHz, Me 2 SO-d 6 ) δ 3.55 (2H, 2m, H-5' a and H-5' b ) , 3.95 (IH, q, H-4') , 4.12 (IH, m, H-3'), 4.50 (IH, q, H-2' ) , 5.82 (IH, d, H-l'), 8.38 (IH, s, H-8). HPLC retention time 18.39 (gradient elution, 15-35% acentonitrile/0.1 M pH 3.3 ammonium sulphate buffer: 214 nm detector); 99.9% purity. EXAMPLE 3 2-Chloro-N-(2,6-dimethyl-l-piperidinyl)adenosine —— The title compound was prepared according to method A as described in Example 1 and obtained as a foam (a mixture of diastereoiso ers) (0.63 g, 61% from 2,6-dichloro- 2,3,5-tri-O-benzoyl-β-D-ribofuranosyl-(9H)-purine) ; NMR (400 MHZ, Me 2 SO-d 6 ) δ 3.55 (IH, m, H-5' a ) , 3.65 (IH, m, H-5' fa ), 3.95 (IH, m, H-4'), 4.12 (IH, m, H-3'), 4.55 (IH, q, H-2'), 5.82 (IH, 2d, H-l'), 8.35, 8.40 (IH, 2s, H-8). HPLC retention time 19.61 (gradient elution, 15-35% acetonitrile/0.1 M pH 3.3 ammonium sulphate buf- fer: 214 nm detector) . EXAMPLE 4 2-Chloro-N-(4-methyl-l-piperazinyl)adenosine The title compound was prepared according to method A as described in Example 1 and obtained as a foam (0.2 g, 14% from 2,6-dichloro-2,3,5-tri-O-benzoyl-β-D-ribofuranosyl- (9H)-purine) ; 1 H NMR (400 MHz, Me 2 SO-d 6 ) δ 3.56 (IH, m, H-5' a ), 3.67 (IH, m, H-5' b ), 3.96 (IH, m, H-4'), 4J13 (IH, m, H-3'), 4.50 (IH, m, H-2'), 5.84 (IH, d, H-l'), 8.40 (IH, s, H-8). HPLC retention time 10.00 (gradient elution, 15-35% acetonitrile/0.1 M pH 3.3 ammonium sul- phate buffer: 214 nm detector) . EXAMPLE 5 2-Chloro-N-(1-piperidinyl)adenosine 2,6-Dichloro-2,3,5-tri-O-benzoyl-β-D-ribofuranosyl-(9H) purine (20.0 g, 31.7 mmol) (prepared as described in example 1), l-aminopiperidine (6.35 g, 63.4 mmol) and N,N-diisopropylethylamine (8.20 g, 63.4 mmol) were dis¬ solved in dioxan (300 ml), and after 2.5 hours TLC indi¬ cated that the starting material was consumed. Dichloro- methane (500 ml) was added and the mixture was washed with water (2 x 150 ml) . The organic phase was dried (MgS0 4 ) and evaporated in vacuo to a foam. The foam was treated with methanol (120 ml) (causing crystallisation) and the vessel was kept at -10°C for 1 hour. The product, 2',3',5'-tri-O-benzoyl-2-chloro-N-(1-piperidinyl)adeno¬ sine, was collected as white crystals (19.4 g, 88%), m.p. 110-112°C; 'H NMR (400 MHz, Me 2 SO-d 6 ) δ 4.68 (IH, dd, H- 5' 8 ), 4.80 (IH, dd, H-5' b ), 4.88 (IH, q, H-4'), 6.20 (IH, t, H-3'), 6.50 (IH, d, H-l'), 6.85 (IH, t, H-2'), 8.45 (IH, S, H-8) . C 36 H 33 N 6 C10 7 . H 2 0 requires C, 60.45 ; H, 4.9 ; N, 11.75% . Found: C, 60.45 ; H, 4.8 ; N, 11.3% . The above 2',3',5'-tri-O-benzoyl-2-chloro-N-(1-piperidi¬ nyl)adenosine (19.2 g, 27.5 mmol) was dissolved in metha¬ nolic ammonia (150 ml) (previously saturated at -10°C) and stirred at room temperature for 18 hours. The pre¬ cipitated benzamide was removed by filtration, and'the filtrate was evaporated to a fawn oil, which was tritu¬ rated with diethyl ether to provide the title compound (6.0 g, 57%) as a white foam, 1 H NMR (400 MHz, Me 2 SO-d 6 ) δ 3.55 (IH, m, H-5' a ) , 3.66 (IH, m, H-5' b ) , 3.94 (IH, q, H-4'), 4.12 (IH, m, H-3'), 4.50 (IH, q, H-2'), 5.82 (IH, d, H-l'), 8.40 (IH, s, H-8); HPLC retention time 26.57 (gradient elution, 5-25% acetonitrile/0.1 M pH 3.3 ammon¬ ium sulphate buffer: 214 nm detector); purity 99%. EXAMPLE 6 2-Chloro-N-(2-phenyl-l-piperidinyl)adenosine ~~ The title compound was prepared according to method A as described in Example 1 was obtained as a solid (0.25 g, 26%) by the reaction of l-amino-2-phenylpiperidine (Over berger, C.G. and Herin, L.P. Journal of Organic Chemis- try, 1962, 27, 417) with 9-(2',3',5'-tri-0-benzoyl-β-D- ribofuranosyl)-2,6-dichloro-9H-purine, followed by de- protection (as described in Example 5) to give the title nucleoside (a ca. 60:40 mixture of diastereoisomers) : m.p. 186-210°C; NMR (400 MHz, Me 2 SO-d 6 ) δ 3.47 - 3.20 (2H, m, 5'-CH 2 ), 3.82 - 3.97, 4.04 - 4.14 (2H, 2m, H-3' and H-4'), 4.46 - 4.56 (IH, 2q, H-2'), 5.33, 5.73 (IH, 2d, H-l'), 8.26, 8.48 (IH, 2s, H-8). EXAMPLE 7 (R)-2-Chloro-N-[2-(methoxymethyl)-1-pyrrolidinyl] adenosine The title compound was prepared as described in Example 5 and obtained as a semi-solid foam (0.49 g, 37% from 9- (2',3',5'-tri-O-benzoyl-β-D-ribofuranosyl)-2,6-dichloro- 9H-purine); 1 H NMR (400 MHz, Me 2 SO-d 6 ) δ 3.56 (IH, m, H- 5' a ), 3.67 (IH, m, H-5' b ), 3.95 (IH, q, H-4'), 4.13 (IH, 1, H-3'), 4.53 (IH, q, H-2'), 5.82 (IH, d, H-l'), 8.40 (IH, s, H-8); HPLC retention time 5.6 (gradient elution, 20- 80% acetonitrile/water (containing 0.1% TFA) : 250 nm detector) ; purity 99%. EXAMPLE 8 (S)-2-Chloro-N-[2-(methoxymethyl)-1-pyrrolidinyl]- adenosine The title compound was prepared as described in Example 5 and obtained as a foam (0.66 g, 50% from 9-(2',3',5'-tri- O-benzoyl-β-D-ribofuranosyl)-2,6-dichloro-9H-purine) ; 1 H NMR (400 MHz, Me 2 SO-d 6 ) δ 3.56 (IH, m, H-5' a ) , 3.67 (IH, m, H-5' b ), 3.95 (IH, q, H-4'), 4.13 (IH, q, H-3'), 4.53 (IH, q, H-2'), 5.82 (IH, d, H-l'), 8.40 (IH, s, H-8); HPLC retention time 5.6 (gradient elution, 20-80% aceto- nitrile/water (containing 0.1% TFA) : 250 nm detector); purity 98%. EXAMPLE 9 (Method C) 2-Fluoro-N-(1-piperidinyl)adenosine 9-(2',3',5'-Tri-O-acetyl-β-D-ribofuranosyl)-2-amino-6- chloro-(9H)-purine (6.0 g, 14 mmol) (prepared as de¬ scribed by Robins, M.J. and Uznanski, B. , in Nucleic Acid Chemistry (Townsend, L.B. and Tipson, R.S., eds.,) John Wiley and Sons, Inc., 1986, 3, 144) was dissolved in dioxan (100 ml) . 1-Aminopiperidine (1.83 ml, 16.95 mmol) was added followed by triethylamine (2.33 ml, 18.5 mmol) and the solution was stirred for 190 hours at room tem- perature. The reaction mixture was filtered, evaporated and the resultant residue was purified by column chroma¬ tography on silica gel eluting with ethyl acetate/cyclo¬ hexane (3/1) to afford 2' ,3',5'-tri-0-acetyl-2-amino-N- (1-piperidinyl)adenosine (4.88 g, 71%) as a foam which solidified on coevaporation with methanol: m.p. 77-79°C. *H NMR (400 MHz, Me 2 SO-d 6 ) δ 2.04 (6H, s, 2' and 3'-0- acetyl-CH 3 ) , 2.13 (3H, s, 5'-0-acetyl-CH 3 ) , 4.30 (2H, m, H-5 , a and H-4'), 4.40 (IH, dd, H-5' b ), 6.03 (IH, d. H-l' ) . The above 2',3',5'-tri-O-acetyl-N-(1-piperidinyl)adeno¬ sine (1.33 g, 2.7 mmol) was dissolved in THF (50 ml) and the temperature of the solution was held between -10°C and -20°C. Fluoroboriσ acid (48%, 100 ml) was added followed by an aqueous solution of sodium nitrite (0.75 g/ml, 1.5 ml). Addition of three identical amounts of sodium nitrite was continued at 0.3 hour intervals, afte which TLC investigation (on a neutralised sample) indi¬ cated that the starting material was consumed [r f 0.47 (Si0 2 , ethyl aσetate/ ethanol (90/10))]. The pH of the reaction mixture was adjusted to ca. 6 with 50% sodium hydroxide solution with cooling to below 0°C and the now red reaction mixture was diluted with water (250 ml) . The solution was extracted with chloroform (2 x 100 ml) and the combined extracts were dried (MgS0 4 ) . The residue on evaporation (containing 2',3',5'-tri-o-acetyl-2-fluoro-N- (1-piperidinyl)adenosine was treated with methanolic ammonia (150 ml) (previously saturated at -lθ°C) and stirred at room temperature for 72 hours. The reaction mixture was evaporated and the resultant residue was purified by column chromatography on silica gel eluting with dichloromethane/methanol (0-10%) to provide the title compound (0.093 g) as a white solid, after washing with ethyl acetate. M.p. 197-199°C; *H NMR (400 MHz, Me 2 SO-d 6 ) δ 3.57, 3.65 (2H, ABX, H-5' a and H-5' b ) , 3.92 (IH, q, H-4'), 4.12 (IH, m, H-3'), 4.50 (IH, q, H-2'), 5.80 (IH, d, H-l'), 8.35 (IH, s, H-8). HPLC retention time 10.12 (gradient elution, 5-25% acetonitrile/0.1 M pH 3.3 ammonium sulphate buffer: 214 nm detector): 100% purity. C 15 H 21 FN 6 0 4 . 0.2 EtOAc requires C, 49.2; H, 5.9; N, 21.8%. Found: C, 49.2; H, 5.9; N, 21.75%. EXAMPLE 10 (Method C. 2-Bromo-N-(1-piperidinyl)adenosine 9-(2',3',5'-Tri-O-acety1-β-D-ribofuranosyl)-2-amino-6- chloro-9H-purine (2.2 g, 5.13 mmol) (prepared as de¬ scribed in example 9) was dissolved in acetonitrile (40 ml) . Bro oform (5.5 ml, 62.9 mmol) (dried by passage through an alumina column) and 3-methylbutylnitrite (6.1 ml, 45.6 mmol) were introduced and the reaction mixture was satu¬ rated with nitrogen before being heated at 45°C for 18 hours and allowed to cool to room temperature; the pro¬ duct had r f 0.47 (Si0 2 , ethyl acetate). The reaction mix¬ ture was evaporated in vacuo and purified by flash chro¬ matography on silica gel; elution initially with di¬ chloromethane followed by dichloromethane/methanol (50:1) provided the product which was dissolved in a mixture of dichloromethane (2 ml) and ethanol (30 ml) . The dichloro¬ methane was removed in vacuo and 9-(2',3',5'-tri-0- acety1-β-D-ribofuranosyl)-2-bromo-6-chloro-9H-purine crystallized as a solid (2.11 g, 42%): m.p. 160-162°C. To a sample of 9-(2',3',5'-tri-o-acetyl-β-D-ribo- furanosyl)-2-bromo-6-chloro-9H-purine (1.0 g, 2.03 mmol) in dioxan (20 ml) 1-aminopiperidine (0.24 ml, 2.23 mmol) was added followed by triethylamine (2.33 ml, 18.5 mmol) and the solution was stirred for 20 hours at room tem¬ perature. The reaction mixture was filtered, evaporated and the resultant residue was purified by flash chroma¬ tography on silica gel. Elution initially with dichloro¬ methane and then with dichloromethane/methanol (100:1) provided impure 2',3',5'-tri-0-acetyl-2-bromo-N-(l- piperidinyl)adenosine which was repurified by flash chromatography in cyclohexane/ethyl acetate (1:1), giving the pure product as a foam (0.86 g, 76%). The above 2',3',5'-tri-o-acetyl-2-bromo-N-(1-piperidi¬ nyl)adenosine was treated with methanolic ammonia (10 ml (previously saturated at -10°C) and stirred at room temperature for 16 hours after which time TLC investiga- tion indicated that the starting material was consumed and a new product was present [r f 0.24 (Si0 2 , ethyl ace- tate/methanol (90/10) ]. The reaction mixture was evapor¬ ated and the resultant residue was treated with water (2 ml) and the suspension was extracted with ethyl acetate (2 x 25 ml) . The combined extracts were dried (MgS0 4 ) and coevaporated with dichloromethane; NMR (400 MHz, Me 2 SO-d 6 ) δ 3.54, 3.65 (2H, ABX, H-5' a and H-5' b ) , 3.94 (IH, q, H-4'), 4.12 (IH, m, H-3'), 4.50 (IH, m, H-2'), 5.82 (IH, d, H-l'), 8.38 (IH, s, H-8). HPLC retention time 14.25 (gradient elution, 5-25% acetonitrile/0.1 M pH 3.3 ammonium sulphate buffer: 214 nm detector). C 15 H 21 BrN 6 0 4 . 0.33 CH 2 C1 2 . 0.75 H 2 0 requires C, 40.1; H, 5.1; N, 18.3%. Found: C, 40.5; H, 5.2; N, 17.8%. EXAMPLE 11 (Method C) 2-Iodo-N-(1-pyrrolidinyl)adenosine 9-(2',3',5'-Tri-O-acetyl-β-D-ribofuranosyl)-2-amino-6- chloro-9H-purine (2.2 g, 5.13 mmol) (prepared as de¬ scribed in Example 9) (0.54 g, 1.0 mmol) was dissolved in dioxan (5 ml). 1-Aminopyrrolidine hydrochloride (0.135 g, l.l mmol) was added followed by triethylamine (0.312 ml, 2.3 mmol) and the solution was stirred for 72 hours at room temperature. Further 1-aminopyrrolidine hydro- chloride (0.405 g, 3.3 mmol) and triethylamine (0.935 ml, 3.45 mmol) were introduced and stirring was continued at room temperature for 24 hours. Ethanol (1 ml) was added and the solution was heated at 50°C for 2 hours. The reaction mixture was evaporated and purified by column chromatography on silica gel eluting initially with n- heptane/THF (4/1) and later with n-heptane/THF (1/1) to provide 9-(2',3',5'-tri-O-acetyl-β-D-ribofuranosyl)-2- iodo-6-(l-pyrrolidinyl)-(9H)-purine (0.14 g, 23%) as a solid which was recrystallized from ethanol giving 0.08 g (14%); 1 H NMR (400 MHz, Me 2 SO-d 6 ) δ 2.04, 2.07 (6H, s, 2'- and 3'-0-acetyl-CH 3 ) , 2.13 (3H, s, 5'-0-acetyl-CH 3 ) , 4.28 (IH, m, H-5' a ), 4.35 - 4.43 (2H, m, H-5' b and H-4'), 6.15 (IH, d, H-l'), 8.29 (IH, S, H-8). The above 9-(2',3',5'-tri-O-acetyl-β-D-ribofuranosyl)-2- iodo-6-(l-pyrrolidinyl)-(9H)-purine (0.063 g, 0.107 mmol) was suspended in methanol (1 ml) and dried potassium carbonate (0.030 g, 0.22 mmol) was introduced. The reac¬ tion mixture was stirred for 24 hours at room temperature and further portions of methanol (10 ml) and dried potas¬ sium carbonate (0.030 g, 0.22 mmol) were added. After a further 24 hours, the solution was treated with glacial acetic acid (0.1 ml) and evaporated. The residue was dissolved in a mixture of water (20 ml) and methanol (10 ml) and the methanol was removed by azeotropic distilla¬ tion, causing the product to crystallize. The title compound was obtained as white crystals, m.p. 216-217°C; 1 H NMR (400 MHz, Me 2 SO-d 6 ) δ 3.94 (IH, q, H-4'), 4.12 (IH, q, H-3'), 4.50 (IH, q, H-2'), 5.83 (IH, d, H-l'), 8:28 (IH, s, H-8); HPLC retention time 13.70 (gradient elution, 25-45% acetonitrile/0.1 M Ph 3.3 ammonium sul¬ phate buffer: 214 nm detector) : purity 97.5%. EXAMPLE 12 (Method B) N-(1-Piperidinyl)-2-(1-propoxy)adenosine 2-Chloro-N-(1-piperidinyl)adenosine (0.50 g, 1.3 mmol) (Example 5) was dissolved in a solution of sodium hydrox¬ ide (0.51 g, 1.3 mmol) in 1-propanol (15 ml), and the solution was heated at reflux for 4.5 hours, after which time TLC investigation showed that the starting material had been consumed. The reaction mixture was evaporated and the resultant residue was dissolved in water. The solution was neutralized with 4N aqueous hydrochloric acid and extracted with dichloromethane (3 x 50 ml) . The combined extracts were dried (MgS0 4 ) and evaporated to an oil which was triturated with diethyl ether to afford a fawn foam. This foam was purified by column chromatogra¬ phy on silica gel (2 x 20 cm) ; elution with a mixture of dichloromethane/ethanol 25% aqueous ammonia solution (60/10/1) provided the title compound (0.20 g, 37%) as a semi-solid foam; 'H NMR (400 MHz, Me 2 SO-d 6 ) δ 3.54, 3.65 (2H, ABX, H-5' a and H-5' b ) , 3.92 (IH, q, H-4'), 4.15 (IH, q, H-3'), 4.60 (IH, q, H-2'), 5.80 (IH, d, H-l'), 8.16 (IH, S, H-8) . EXAMPLE 13 2-Chloro-N-(4-pheny1-1-piperazinyl)adenosine The title compound was prepared according to method A as described in Example 6 by reacting l-amino-4-phenyl- piperazine hydrochloride (also prepared using the method described by Overberger, C.G. and Herin, L.P., Journal of Organic Chemistry, 1962, 27, 417) (0.77 g, 3.0 mmol) with 9-(2',3',5'-tri-o-benzoyl-β-D-ribofuranosyl)-2,6-di- chloro-9H-purine (1.90 g, 3.0 mmol), followed by de- benzoylation of the purified product using methanolic ammonia. This provided the title 2-chloro-N-(4-pheny1-1- piperazinyl) denosine (0.81 g, 60%) (after column chroma¬ tography) as a foam, 1 H NMR (DMSO-d 6 ) δ 3.53 - 3.60 (IH, m, H-5' a ) , 3.63 - 3.70 (IH, m, H-5' b ) , 3.95 (IH, q, H-4'), 4.13 (IH, q, H-3'), 4.51 (IH, q, H-2'), 5.07 (IH, t, 5'-0H), 5.22, 5.50 (2H, 2d, 2'-and 3'-OH), 5.85 (IH, d, H-l'), 6.77 - 7.26 (5H, 3m, Ar-H) , 8.44 (IH, s, H-8), 9.50 (IH, S, N-H) . C 20 H 24 Cl 7 O 4 . H 2 0 requires C, 50.1 ; H, 5.3 ; N, 20.4%. Found: C, 50.2; H, 5.4; N, 20.0%. EXAMPLE 14 2-Chloro-N-(4-phenyl-l,2,3,6-tetrahydro-l-pyridinyl)- adenosine The title compound was prepared according to method A as described above by reacting crude l-amino-4-phenyl- 1,2,3,6-tetrahydropyridine (prepared by the procedure outlined in Example 6) (1.25 g) with 9-(2',3',5'-tri-0- benzoyl-β-D-ribofuranosyl)-2,6-dichloro-9H-purine (2.50 g, 3.9 mmol), followed by debenzoylation of the purified product using methanolic ammonia to provide the title 2- Chloro-N-(4-phenyl-l,2,3,6-tetrahydro-l-pyridinyl)adeno¬ sine (0.20 g 12%) (after column chromatography) as a foam, 1 H NMR (DMSO-d 6 )5 3.53 - 3.70 (4H, m, H-5' a , H-5' b and -CH 2 -) , 3.94 (IH, q, H-4'), 4.14 (IH, q, H-3'), 4.52 (IH, q, H-2'), 5.07 (IH, t, 5'-0H) , 5.22, 5.50 (2H, 2d, 2'-and 3'-OH), 5.85 (IH, d, H-l'), 6.15 (IH, br s, vi- nylic C-H) , 7.24 - 7.51 (5H, m, Ar-H) , 8.43 (IH, s, H-8), 9.55 (IH, S, N-H) . C 21 H 23 C1N 6 0 4 , 1.25H 2 0 requires C, 52.4; H, 5.3; N, 17.5%. Found: C, 52.6; H, 5.0; N, 17.1%. EXAMPLE 15 2-Chloro-N-(4-pheny1-1-piperidinyl)adenosine The title compound was prepared according to method A as described above by reacting l-amino-4-phenylpiperidine (prepared as outlined in Example 6) (0.77 g, 3.6 mmol) with 9-(2',3',5'-tri-0-benzoyl-β-D-ribofuranosyl)-2,6-di- chloro-9H-purine (1.90 g, 3.0 mmol), followed by de¬ benzoylation of the purified product using methanolic ammonia. This provided the title 2-chloro-N-(4-phenyl-l- piperidinyl)adenosine (0.49 g, 37%) as a solid which precipitated on evaporation of column chromatography fractions, mp 142-149°C. 1 H NMR (DMSO-d 6 ) δ 3.53 - 3.60 (IH, m, H-5' a ), 3.63 -3.70 (IH, m, H-5' b ) , 3.95 (IH, q, H-4'), 4.13 (IH, q, H-3'), 4.51 (IH, q, H-2'), 5.07 (IH, t, 5'-0H), 5.22, 5.50 (2H, 2d, 2'-and 3'-OH) , 5.84 (IH, d, H-l'), 7.18 - 7.35 (5H, 2m, Ar-H) , 8.43 (IH, s, H-8), 9.45 (IH, s, N-H) . C Α Ε- 25 ClR 6 O i requires C, 54.6; H, 5.8; N, 17.4%. Found: C, 54.4; H r 5.8; N, 17.0%. EXAMPLE 16 2-Chloro-N-(3-phenoxy-l-piperidinyl)adenosine 1-(1.1-Dimethylethoxycarbonyl)-3-hvdroxypiperidine 3-Hydroxypiperidine (10.1 g, 0.1 mol) was dissolved in tetrahydrofuran (50 ml) and IN aqueous sodium hydroxide solution (95 ml) was introduced. The solution was cooled to 0°C and a solution of di-tert-butyl dicarbonate (24.0 g, 0.11 mol) in tetrahydrofuran was added over 1 h. The reaction mixture was stirred at ambient temperature for 18 h and evaporated to an aqueous suspension. Water (100 ml) was added and the mixture was extracted with di¬ chloromethane (3 x 100 ml) . The combined extracts were dried (MgS0 4 ) , evaporated and the residue was recrystal- lised from n-heptane to provide the title product as a solid (15.71 g, 78%), mp 67-69°C. 3-Phenoxypiperidine 1-(1 ,1-Dimethylethoxycarbonyl)-3-hydroxypiperidine (6.0 g, 30 mmol) was dissolved in toluene (75 ml) and phenol (2.82 g, 30 mmol) was added followed by triphenylphos- phine (11.8 g, 45 mmol). To this mixture a solution of diethylazodicarboxylate (7.84 g, 45 mmol) in toluene (75 ml) was introduced dropwise and the reaction mixture was stirred for 18 h. at ambient temperature during which time triphenylphosphine oxide precipitated. The reaction mixture was filtered, washed with 0.1 N sodium hydroxide solution (55 ml), 0.5 N sodium bicarbonate (100 ml) and with a mixture of saturated brine (25 ml) and water (25 ml) . The dried toluene solution was evaporated, the residue was dissolved in ethyl acetate (10 ml) and cyclo¬ hexane (200ml) was added. The solid precipitate was removed and the residue on evaporation was purified by flash chromatography on silica gel (7.5 x 15 cm). Elution with heptane ethyl acetate (9/1) provided the phenyl ether as an oil (4.01 g, 40%), containing the desired intermediate as well as ca. 20% phenol. This oil was dissolved in dichloromethane (15 ml) and trifluoroacetic acid (3 ml) was added. The solution was stirred at room temperature for 6 h and at -18°C for 72 h. Saturated sodium bicarbonate solution was added to the reaction mixture until neutrality was reached, followed by extrac¬ tion with dichloromethane (6 x 30 ml) . The combined extracts were dried (MgS0 4 ) and evaporated to an oil which was dissolved in toluene (200 ml) containing πteth- anol (1.26 ml, 30 mmol). Chlorotrimethylsilane (1.82 ml, 15 mmol) was added, and in the absence of cryst¬ allisation, the solution was evaporated to an oil, which was treated with diethyl ether. The solid which was formed was dried in vacuo to give the title compound (1.90 g, 27%), mp 156-159°C. This 3-phenoxypiperidine was N-aminated using the method described in Example 6. 2-Chloro-N-(3-phenoxy-l-piperidinyl)adenosine was pre¬ pared according to method A as described in Example 6 by reacting l-amino-3-phenoxypiperidine (0.60 g, 3.4 mmol) with 9-(2',3',5'tri-o-benzoyl-β-D-ribofuranosyl)-2,6-di- chloro-9H-purine (2.0 g, 3.2 mmol), followed by de¬ benzoylation of the purified product using methanolic ammonia. This provided the desired compound (0.65 g, 43% (after column chromatography) as a foam, 1 H NMR (DMSO- ά 6 ) δ 3.53 - 3.60 (IH, m, H-5' a ) , 3.64 - 3.72 (IH, m, H-5' b ), 3.96 (IH, q, H-4'), 4.14 (IH, q, H-3'), 4.50 - 4.59 (IH, m, H-2' and -C-H)) , 5.07 (IH, t, 5'-0H), 5.23, 5.50 (2H, 2d, 2'-and 3'-OH), 5.84 (IH, d, H-l'), 6.79 - 7.32 (5H, 3m, Ar-H) , 8.45 (IH, s, H-8), 9.55 (IH, s, N- H). C^H^CIN^. 0.5 H 2 0 requires C, 51.9 ; H, 5.4 ; N, 17.3%. Found: C, 51.9; H, 5.5; N, 17.1%. EXAMPLE 17 2-Chloro-N-[4-phenoxy-l-piperidinyl]adenosine This compound was prepared from 4-hydroxypiperidine using the methodology described in Example 16. l-Amino-4-phen- oxypiperidine (0.96 g, 5.0 mmol) was reacted with 9- (2',3',5'-tri-O-benzoyl-β-D-ribofuranosyl)-2,6-dichloro- 9H-purine (2.50 g, 4 mmol), followed by debenzoylation of the purified product using methanolic ammonia. This provided the title 2-chloro-N-(4-phenoxy-1-piperidinyl)- adenosine (1.07 g, 57%) as a foam, 1 H NMR (DMSO-d 6 ) δ 3.52 - 3.60 (IH, m, H-5' a ) , 3.63 - 3.70 (IH, m, H-5' b ) , 3.95 (IH, q, H-4'), 4.14 (IH, q, H-3'), 4.43 - 4.54 (2H, m, H- 2' and -C-H), 5.07 (IH, t, 5'-0H) , 5.22, 5.50 (2H, 2d, 2'-and 3'-OH), 5.84 (IH, d, H-l'), 6.90 - 7.33 (5H, 2m, Ar-H), 8.42 (IH, s, H-8), 9.49 (IH, S, N-H) . C 21 H 25 C1N 6 0 4 .H 2 0 requires C, 51.0; H, 5.5; N, 17.0%. Found: C, 50.9; H, 5.2; N, 16.6%. EXAMPLE 18 2-Chloro-N-(3-phenylthio-l-piperidinyl)adenosine 3-Phenylthiopiperidine was prepared from 1-(1,1-dimethy1- ethoxycarbonyl)-3-hydroxypiperidine by the method described by Kotsuki et &1. , Tetrahedron Letters, 1991, 32, 4155-4158; otherwise the synthesis proceeded as described in Example 16. l-Amino-3-phenylthiopiperidine (0.98 g, 4.0 mmol) was reacted with 9-(2',3',5'tri-O- benzoyl-β-D-ribofuranosyl)2,6-dichloro-9H-purine (2.11 g, 3.3 mmol), followed by debenzoylation of the purified product using methanolic ammonia. This provided the title 2-chloro-N-(3-phenylthio-l-piperidinyl)adenosine (0.89 g, 55%) as a foam, 1 H NMR (DMSO-d 6 ) δ 3.52 - 3.59 (IH, m, H-5' a ), 3.63 -3.71 (IH, m, H-5' b ) , 3.95 (IH, q, H-4'), 4.13 (IH, q, H-3'), 4.46 - 4.54 (IH, q, H-2'), 5.07 (IH, t, 5'-0H), 5.22, 5.49 (2H, 2d, 2'-and 3'-0H), 5.84 (IH, d, H-l'), 7.20 - 7.50 (5H, 2m, Ar-H), 8.43 (IH, s, H-8), 9.50 (IH, S, N-H) . C 21 H 25 C1N 6 0 4 , 0.5 H 2 0 requires C, 50.2; H, 5.2; N, 16.7%. Found: C, 50.0; H, 5.3; N, 16.6%. EXAMPLE 19 2-Chloro-N-(4-phenylthio-1-piperidinyl)adenosine The title compound was prepared as described in Example 18. l-Amino-4-phenylthiopiperidine (1.10 g, 6.7 mmol) was reacted with 9-(2',3',5'tri-O-benzoyl-β-D-ribofuranosyl) -2,6-dichloro-9H-purine (2.5 g, 4 mmol), followed by debenzoylation of the purified product using methanolic ammonia. This provided the title 2-chloro-N-(4-phenyl- thio-1-piρeridinyl)adenosine (1.25 g, 65%) as a foam, 1 H NMR (DMSO-d 6 )S 3.51 - 3.60 (IH, m, H-5' a ) , 3.62 -3.68 (IH, m, H-5' fa ), 3.95 (IH, q, H-4'), 4.14 (IH, q, H-3'), 4.50 (IH, q, H-2'), 5.08 (IH, t, 5'-0H) , 5.21, 5.50 (2H, 2d, 2'-and 3'-OH), 5.83 (IH, d, H-l'), 7.24 - 7.45 (5H, 2m, Ar-H), 8.41 (IH, S, H-8), 9.44 (IH, s, N-H) . C 2 i H 25 C1N 6 ° 4 s ' °- 75 H 2 ° requires C, 49.8; H, 5.3; N, 16.6%. Found: C, 49.6; H, 5.2; N, 16.5%. EXAMPLE 20 2-Chloro-N-[2-(phenylthiomethyl)-1-piperidinyl]adenosine 2-(Phenylthiomethyl)piperidine was prepared from 2- (hydroxymethyl)piperidine by the method described by Kotsuki et al.. Tetrahedron Letters, 1991, 32, 4155-4158; otherwise the synthesis proceeded as described in Example 16. l-Amino-2-(phenylthiomethyl)piperidine (1.4 g, 6.5 mmol) was reacted with 9-(2' ,3' ,5'tri-O-benzoyl-β-D-ribo- furanosyl)-2,6-dichloro-9H-purine (2.0 g, 3.25 mmol), followed by debenzoylation of the purified product using methanolic ammonia. This provided the title 2-chloro-N- [2-(phenylthiomethyl)-1-piperidinyl]adenosine (0.17 g, 10%) as a foam (a mixture of diastereoisomers) ; 1 H NMR (DMSO-d 6 )<S 3.51 - 3.59 (IH, m, H-5' a ) , 3.62 - 3.70 (IH, m, H-5' b ) , 3.95 (IH, q, H-4'), 4.13 (IH, q, H-3'), 4.47 - 4.56 (IH, m, H-2'), 5.06 (IH, t, 5'-0H) , 5.22, 5.50 (2H, 2d, 2'-and 3'-OH), 5.82 - 5.87 (IH, 2d, H-l'), 7.16 - 7.54 (5H, 2m, Ar-H), 8.41, 8.46 (IH, 2s, H-8), 9.40 (IH, s, N-H) . EXAMPLE 21 2-Chloro-N-(3-hydroxypiperidinyl)adenosine The title compound was prepared according to method A as described above by reacting l-amino-3-hydroxypiperidine (prepared from 3-hydroxypiperidine as outlined in Example 6) (0.60 g, 5.9 mmol) with 9-(2',3',5'tri-Q-benzoyl-β-D- ribofuranosyl)-2,6-dichloro-9H-purine (2.50 g, 3.94 mmol) , followed by debenzoylation of the purified product using methanolic ammonia to provide the title 2-chloro-N- (3-hydroxypiperidinyl)adenosine (0.12 g, 8 %) (after column chromatography) as a foam (a mixture of diastereo- isomers) ; 1 H NMR (DMSO-d 6 ) δ 3.52 - 3.60 (IH, m, H-5' a ), 3.63 - 3.70 (IH, m, H-5' b ) , 3.95 (IH, q, H-4'), 4.14 (IH, m, H-3'), 4.52 (IH, m, H-2'), 5.08 (IH, t, 5'-0H), 5.22, 5.50 (2H, 2d, 2'-and 3'-OH), 5.84 (IH, d, H-l'), 8.43 (IH, br s, H-8), 9.45 (IH, 2 br s, N-H). EXAMPLE 22 2-Chloro-N-(4-phenylsulphonyl-l-piperidinyl)adenosine 2-Chloro-N-(4-phenylthio-1-piperidinyl)adenosine (Example 19) (0.25 g, 0.5 mmol) was dissolved in methanol (2 ml) and a solution of potassium hydrogen persulphate ("Oxone") (Trost, B.M. and Curran, D.P., Tetrahedron Letters, 1981, 22, 1287-1290) (0.47 g, 0.76 mmol) in water (2 ml) was added at 0°C. The yellowish reaction mixture was stirred at ambient temperature for 4 h. , and saturated sodium bicarbonate (10 ml) was introduced. The suspension was extracted with dichloromethane (2 x 50 ml) , and a yellow gum was seen to appear in the aqueous phase. This yellow gum was dissolved in methanol (20 ml) , the dried dichloromethane extracts were added, and the mixture was evaporated to a residue. Purification by "flash" chromatography, eluting initially with dichloro¬ methane, proceeding to dichloromethane/methanol (9/1) provided the title nucleoside as a foam (0.04 g, 15%), 1 H NMR (DMSO-d 6 )tT 3.50 - 3.60 (IH, m, H-5' a ) , 3.62 -3.68 (IH, m, H-5' b ), 3.93 (IH, br q, H-4'), 4.12 (IH, m, H-3'), 4.50 (IH, m, H-2'), 5.05 (IH, t, 5'-0H) , 5.21, 5.48 (2H, 2d, 2'-and 3'-0H), 5.82 (IH, d, H-l'), 7.66 - 7.94 (5H, 2m, Ar-H), 8.41 (IH, s, H-8), 9.49 (IH, S, N- H). EXAMPLE 23 (Method C) 2-Methylthio-N-(1-piperidinyl)adenosine 9-(2',3',5'-Tri-O-acetyl-β-D-ribofuranosyl)-6-chloro-2- methylthio-9H-purine 9-(2',3',5'-Tri-O-acetyl-β-D-ribofuranosyl)-2-amino-6- chloro-9H-purine (see Example 9) (4.0 g, 9.3 mmol) was dissolved in acetonitrile (100 ml) . Isoamylnitrite (10.84 g, 93 mmol) was introduced followed by methyl disulphide (4.14 ml, 46 mmol) and the reaction mixture was heated at an oil bath temperature of 100°C for 2h. The evolved gas was removed via a hypochlorite scrubber. The reaction mixture was cooled, evaporated and purified by flash chromatography on silica gel. Elution initially with dichloromethane, followed by dichloro-methane/methanol (100/1) provided 9-(2',3',5'-tri-o-acetyl-β-D-ribofuran- osyl)-6-chloro-2-methylthio-9H-purine (3.1 g, 72%) as a foam, 1 H NMR (CDC1 3 )S 2.12, 2.14, 2.18 (9H, 3s, 2', 3' and 5'-0-acetyl CH 3 ) , 2.66 (3H, s, -SCH 3 ) , 4.28 - 4.51 (3H, m, H-5' a , H-5' b and H-4'), 5.66 (IH, t, H-3'), 6.0 (IH, t, H-2'), 6.13 (IH, d, H-l'), 8.11 (IH, s, H-8). The above 9-(2',3',5'-tri-O-acetyl-β-D-ribofuranosyl)-6- chloro-2-methylthio-9H-purine (1.83 g, 3.9 mmol) was dissolved in dioxan (40 ml) followed by 1-aminopiperidine (0.59 g, 5.85 mmol) and triethyl-amine (1.63 ml, 11.7 mmol) . The reaction mixture was stirred at ambient tem¬ perature for 18 h, evaporated and purified by flash chromatography on silica gel. Elution initially with dichloromethane, followed by dichloromethane/methanol (100/1) provided 9-(2',3',5'-tri-O-acetyl-β-D-ribofuran¬ osyl)-2-methylthio-6-(1-piperidinyl)-9H-purine (1.24 g, 59%) as a foam. This compound was dissolved in methanolic ammonia (10 ml) and the solution was stirred at room temperature for 18 h, evaporated and purified by flash chromatography on silica gel. Elution initially with dichloromethane, followed by dichloromethane/methanol (19/1) gave 2-methylthio-N-(1-piperidinyl)adenosine (0.67 g, 55%) as a foam, 1 H NMR (DMSO-d 6 ) δ 2.51 (3H, s, -SCH 3 ) , 3.50 - 3.56 (IH, m, H-5' a ) , 3.62 - 3.68 (IH, m, H-5' b ) 3.92 (IH, q, H-4'), 4.15 (IH, q, H-3'), 4.50 (IH, q, H- 2'), 5.03 (IH, t, 5'-0H), 5.18, 5.44 (2H, 2d, 2'-and 3'- OH) , 5.84 (IH, d, H-l'), 8.24 (IH, S, H-8), 8.84 (IH, s, N-H) . C 16 H 24 N 6 0 4 S . H 2 0 requires C, 46.4 ; H, 6. 3 ; N, 20. 3% . Found: C, 46. 1; H, 6. 0 ; N, 19.8% .

Claims: CLAIMS l. A compound of formula (I) , or a pharmaceutically acceptable salt thereof: wherein X is halogen, perhalomethyl, cyano, C^-alkoxy, C^- alkylthio or C^-alkylamino; R 1 is selected from the groups consisting of wherein n is 1 to 3 and where the group (a) may be op¬ tionally substituted with one or two C^-alkyl groups, C 2 . 6 -alkenyl, C 2 . 6 -alkynyl, phenoxy, phenyisulphonyl, phenylthio, hydroxy, phenyl, C^-alkoxy, C,_ 6 -alkoxy- C^-alkyl or phenylthioalkyl or wherein Y is O, S or NZ, where Z is H, C^-alkyl or phenyl, and where the group (b) may be optionally substi¬ tuted with C 1 . 6 -alkyl, C 2 . 6 -alkenyl, C 2 . 6 -alkynyl, phenoxy, phenyl, C-^-alkoxy or C-^-alkoxy-C^-alkyl, or which may be optionally substituted with C,_ 6 -alkyl, C 2 . 6 - alkenyl, C 2 . 6 -alkynyl, phenoxy, phenylthio, phenyl, C,_ 6 - alkoxy or C^-alkoxy-C^-alkyl. 2. A compound of formula (I) , or a pharmaceutically acceptable salt thereof: HN (I) HO HOjOH wherein X is halogen, perhalomethyl, cyano, C,_ 6 -alkoxy, C-_ 6 - alkylthio or C-. 6 -alkylamino; s wherein n is l to 3 and where the group (a) may be optio- nally substituted with one or two C-_ 6 -alkyl groups, C 2 . 6 - alkenyl, C 2 . 6 -alkynyl, phenoxy, phenylsulphonyl, phenyl¬ thio, hydroxy, phenyl, or phenylthioalkyl. 3. A compound selected from 2-chloro-N-(1-piperidinyl)- adenosine, 2-chloro-N-(4-pheny1-1-piperazinyl)adenosine, 2-chloro-N-(3-phenoxy-l-piperidinyl)adenosine, 2-chloro- H-[4-phenoxy-l-piperidinyl]adenosine, 2-chloro-N-(4- phenyl-1-piperidinyl)adenosine, 2-chloro-N-(4-phenylthio- 1-piperidinyl)adenosine, 2-chloro-N-(4-phenylsulphony1-1- piperidinyl)adenosine, 2-fluoro-N-(piperidinyl)adenosine, or a pharmaceutically acceptable salt thereof. 4_ s _ A method for the preparation of a compound of formula (I) CHARACTERIZED in: a) reacting a compound of formula II wherein X has the meaning set forth above, wherein L is a leaving group and wherein R 2 and R 3 are the same or dif- ferent and represent hydrogen or benzoyl-, p-toluoyl-, C- j ^-alkanoyl, trimethylsilyl or t-butyldimethylsilyl, with a hydrazine derivative of the general formula III H 2 N-R 1 (III) wherein R 1 has the meaning set forth above, to form a compound of the invention, or b) reacting a compound of formula II wherein X has the meaning set forth above, wherein L is leaving group and wherein R 2 and R 3 are the same or dif¬ ferent and represent hydrogen or benzoyl-, p-toluoyl-, C 1 . 4 -alkanoyl, trimethylsilyl or t-butyldimethylsilyl, with a hydrazine derivative of the general formula III H 2 N-R 1 (III) wherein R 1 has the meaning set forth above, to form a compound of formula IV wherein X, R 1 , R 2 and R 3 have the meaning set forth above, and reacting the compound of formula (IV) with suitable deprotecting agents such as methanolic ammonia, an alkali metal carbonate in alcohol or tetraalkylammonium fluoride to form a compound of the invention, or c) reacting a compound of formula V wherein L, R 1 , R 2 and R 3 have the meanings set forth above with a nucleophile XH, wherein X is C 1 . 6 -alkylamino or C^ g -alkoxy, to form a compound of the invention, or d) reacting a compound of formula V wherein L, R 1 , R 2 and R 3 have the meanings set forth above with a nucleophile XH, wherein X is C 1 . 6 -alkylamino or C^ g -alkoxy, to form a compound of formula IV wherein R 1 , R 2 and R 3 have the meaning set forth above, and wherein X is C 1 . 6 -alkylamino or c 1 . 6 -alkoxy, and react¬ ing the compound of formula (IV) with suitable deprotect- ing agents such as methanolic ammonia, an alkali metal carbonate in alcohol or tetraalkylammonium fluoride to form a compound of the invention, or e) reacting a compound of formula VI wherein B is -NH-R 1 , wherein R 1 has the meaning set forth above, and wherein R 2 and R 3 have the meaning set forth above, with a diazotising agent such as 3-methylbutyl nitrite, to form an intermediate which can be reacted further with a variety of substrates in order to intro¬ duce the group -X into the compound of the invention, or f) reacting a compound of formula VI wherein B is -NH-R 1 , wherein R 1 has the meaning set forth above, and wherein R 2 and R 3 have the meaning set forth above, with a diazotising agent such as 3-methylbutyl nitrite, to form a compound of formula IV wherein X, R 1 , R 2 and R 3 have the meaning set forth above, and reacting the compound of formula (IV) with suitable deprotecting agents such as methanolic ammonia, an alkali metal carbonate in alcohol or tetraalkylammonium fluoride to form a compound of the invention, or g) reacting a compound of formula VI wherein B is a leaving group L with the meaning as set forth above, and wherein R 2 and R 3 have the meaning set forth above, with a diazotising agent such as 3-methyl- butyl nitrite, to form an intermediate which can be reacted further with a variety of substrates in order to introduce the group -X into the compound of formula II wherein X, L, R 2 and R 3 have the meaning set forth above, and reacting the compound of formula (II) with a hydra- zine derivative of the general formula III H 2 N-R 1 (III) wherein R 1 has the meaning set forth above, to form a compound of the invention, or wherein B is a leaving group L with the meaning as set forth above, and wherein R 2 and R 3 have the meaning set forth above, with a diazotising agent such as 3-methyl¬ butyl nitrite, to form an intermediate which can be re¬ acted further with a variety of substrates in order to introduce the group -X into the compound of formula II wherein X, L, R 2 and R 3 have the meaning set forth above, and reacting the compound of formula (II) with a hydra- zine derivative of the general formula III R.N-R 1 (HI) wherein R 1 has the meaning set forth above, to form a compound of formula IV wherein X, R 1 , R 2 and R 3 have the meaning set forth above, and reacting the compound of formula (IV) with suitable deprotecting agents such as methanolic ammonia, an alkali metal carbonate in alcohol or tetraalkylammonium fluoride to form a compound of the invention. 5____ A pharmaceutical composition comprising as active component a compound according to claim 1 or a pharmaceu¬ tically acceptable salt thereof and a pharmaceutically acceptable carrier. §____ A " pharmaceutical composition suitable for use in the treatment of a central nervous system ailment, which comprises as active component a compound according to claim 1 or a pharmaceutically acceptable salt thereof and a pharmaceutically acceptable carrier. 7. A pharmaceutical composition according to claim 5 or 6 in the form of an oral dosage unit containing about 1- 200 mg of the active compound. ji___ A method of treating a central nervous system ailment in a person in need of such treatment characterized in administering to said person an amount of a compound of claim 1 effective in alleviation of such an ailment. 9. A method of treating a central nervous system ailment in a subject in need of such treatment comprising the step of administering to said subject an amount of a com¬ pound of claim 1 which is effective for the alleviation of such ailment in the form of a pharmaceutical composi¬ tion thereof, in which it is present together with a pharmaceutically acceptable carrier or diluent.

Inventors: KNUTSEN LARS JACOB STRAY, LAU JESPER, KNUTSEN, LARS, JACOB, STRAY, LAU, JESPER
Applicants: NOVONORDISK AS, NOVO NORDISK A/S
Application year: 1992
Main classification: A61K31
IPC codes: A61K31, A61P25, C07H19