NO152214B - ANALOGY PROCEDURE FOR THE PREPARATION OF THERAPEUTIC ACTIVE N-CYANO-N`- (2 - ((4-METHYL-5-IMIDAZOLYL) -METHYLTIO) ETHYL-N "-ALKNYLGUANIDINES - Google Patents

Description

The present invention relates to an analog method

for the preparation of certain N-cyano-N<1->{2-[(4-methyl-5-imidazolyl)-methylthio]ethyl}-N"-alkynylguanidines•

These compounds are reported to be I 2 -receptor blocking agents, which inhibit gastric acid secretion and are valuable for the treatment of ulcers.

The clinical purpose in the treatment of pepsin ulcer is

to reduce gastric acid secretion based on the principle "no acid, no ulcer". The traditional therapy of pepsin ulcer in-

carries dietary control and the use of antacids and anticholinergic

ergica.

There is some evidence that histamine may be the final joint

path by,stimulation of gastric acid secretion. This effect of histamine is mediated via f^-receptors and is not inhibited by the classical antihistamines which are F^-receptor blocking agents.

A number of specific F₂ receptor blocking agents (f₂ receptor antagonists) are now known. These compounds inhibit basal acid secretion as well as secretion by other known gastric acid stimulants and are valuable in the treatment of pepsin ulcers.

The compounds produced according to the present invention are histamine I^-receptor antagonists which are effective inhibitors of gastric acid secretion in mammals, including humans, and which are valuable for the treatment of pepsin ulcers.

The compounds in question have the general formula:

where R"<*>" denotes a straight-chain or branched alkynyl group containing from 3-9 carbon atoms, or are non-toxic, pharmaceutically acceptable acid addition salts thereof.

A preferred group of compounds which are prepared by the analogical process according to the invention have the general formula:

where R 4 is hydrogen or methyl, or are non-toxic, pharmaceutically acceptable acid addition salts thereof.

Another preferred group of compounds which are prepared by the analog method according to the invention has the general formula:

where R<4> denotes hydrogen or methyl, and n is an integer from 1-6, or are non-toxic, pharmaceutically acceptable acid addition salts thereof.

A further preferred group of compounds which are prepared by the analog method according to the invention have the general formula:

where R<4> denotes hydrogen or methyl, or are non-toxic, pharmaceutically acceptable acid addition salts thereof.

An even more preferred group of compounds produced by the analogous method according to the invention is N-cyano-N'-{2-[4-methyl-5-imidazolyl)methylthio]ethyl}-N"-(2-butyn-1-yl) )guanidine or non-toxic, pharmaceutically acceptable acid addition salts thereof.

A further preferred group of compounds which are prepared by the analogous method according to the invention is N-cyano-N'-{2-[(4-methyl-5-imidazolyl)methylthio]ethyl}-N"-(3-butyn-1-yl )guanidine or non-toxic, pharmaceutically acceptable acid addition salts thereof.

A further preferred group of compounds which are prepared by the analog method according to the invention is N-cyano-N'-{2-[(4-methyl_-5-imidazolyl)methylthio]ethyl}-N"-(4-entyn-1-yl )guanidine or non-toxic, pharmaceutically acceptable acid addition salts thereof.

A further preferred group of compounds which are prepared by the analogous method according to the invention is N-cyano-N'-{2-[(4-methyl-5-imidazolyl)methylthio]ethyl}-N"-(2-methyl-3-butyne -2-yl)guanidine or non-toxic, pharmaceutically acceptable acid addition salts thereof.

A further preferred group of compounds which are prepared by the analogous method according to the invention is N-cyano-N'-{2-[(4-methyl-5-imidazolyl)methylthio]ethyl}-N"-(3-butyn-2-yl) )guanidine or non-toxic, pharmaceutically acceptable acid addition salts thereof.

The most preferred compounds prepared by the analogous method of the compound are N-cyano-N'-{2-[(4-methyl-5-imidazolyl)methylthio]-ethyl}-N"-propargylguanidine or non-toxic pharmaceutically acceptable acid addition salts hence.

The compounds in question with the general formula:

where R"<*>" denotes a straight-chain or branched alkynyl group with 3-9 carbon atoms, or non-toxic, pharmaceutically acceptable acid addition salts thereof, are produced by an analogous preparation method which, according to the invention, is characterized by reacting a compound with the formula: or an acid addition salt thereof , with a compound of the formula : 1 5 6 where R has the meaning given above, and R and R are different groups which are either H or the group:

where R denotes any such substituent, that SR is a <p>appending, cleavable group with an amino group, e.g. lower alkyl, aryl, substituted aryl, aralkyl, CH2CN, O^COOH or an ester or salt thereof,

and that, if desired, one converts the resulting compound of formula I in basic form or an acid addition salt thereof to the corresponding non-toxic, pharmaceutically acceptable acid addition salt or the free base form.

The reaction is carried out in a non-reactive solvent at a temperature above room temperature. In a preferred embodiment, equimolar amounts of the compounds of formula II and III are used.

The analog method according to the invention is illustrated by the following reaction schemes for the production of a preferred compound.

The reaction is carried out in a non-reactive solvent at a temperature above room temperature. As those skilled in the art will readily appreciate, R can be any such substituent that -SR denotes a suitable leaving group. Thus, as mentioned, R can be lower-alkyl, aryl, substituted aryl (e.g. p-nitrophenyl), aralkyl, -CH2CN, -CH2COOH, -Ct^COOR', e. 1. N-cyano-N'-{ The 2-[(4-methyl-5-imidazolyl)methylthio]ethyl}-SR-isothiourea starting materials can be prepared using the methods described in BE-PS 804,144. The alkynylamine starting materials are either commercially available or can be prepared by methods described in "Bull. Soc. Chim. Fr.", 490 (1958), "Bull. Soc. Chim. Fr.", 592 (1967) and "Annales de Chimie" (Paris), 3, 656 (1958).

The reaction is carried out in a non-reactive solvent at a temperature above room temperature. The substituent R can have the same meaning as in connection with scheme I above. The 2-[(4-methyl-5-imidazolyl)methylthio]ethylamine starting material can be prepared as described in US-PS 3,950,353. The disubstituted cyanodithioiminocarbonate which is used as a starting material in the preparation of the N-cyano-N'-propargyl-SR-isothiourea (see step b in ex. 2) can itself be prepared using methods described in "J. Org. Chem.” 32, 1566 (1967).

It has also been shown that specially chosen reaction conditions in the last step in the preparation of N-cyano-N'-{2-[(4-methyl-5-imidazolyl)methylthio]ethyl}-N"-propargylguanidine via reaction scheme I give significantly improved product yields as well as a product containing fewer impurities. The latter condition has the further advantage that it enables the isolation of the original ("crude") product as a crystalline substance that can be purified to a higher degree by simple recrystallization, and one avoids a chromatographic purification of the original raw product which had to be considered desirable in advance by using other reaction conditions.

The above-mentioned specially chosen reaction conditions consist of using methanol as solvent, using a more concentrated solution during the reaction (approx. 1 g of substituted iso-thiourea per 5 ml of methanol), using nitrogen flushing of the reaction apparatus during the reaction and making use of freshly distilled propargylamine during the reaction.

Experiments have shown that by using a nitrogen purge during the reaction, the formation of small amounts of two as yet unidentified by-products that are formed in the absence of a nitrogen purge is avoided. These byproducts, when present, eluded removal by column chromatography and recrystallization. It is believed that the nitrogen purge prevents the formation of these by-products by removing the methyl mercaptan gas as soon as it is formed.

According to a further analog method according to the invention, a compound is prepared with the general formula:

where R"*" denotes a straight-chain or branched alkynyl group containing from 3-9 carbon atoms, or a non-toxic pharmaceutically acceptable acid addition salt thereof, by reacting a compound with the formula: or an acid addition salt thereof, wherein X denotes hydroxy or or one with a mercapto group conventional leaving group, preferably fluorine, chlorine, bromine, iodine, -0-.SR 2 , where R 2 is lower-3 3 alkyl, -03SR , where R is aryl or substituted aryl, -03SF, acetoxy or 2 ,4-dinitrophenoxy with a compound of the formula:

where R has the meaning given above, and, if desired, converts the compound of formula I in base form or an acid addition salt thereof to the corresponding non-toxic, pharmaceutically acceptable acid addition salt thereof or the free base form.

The reaction is carried out in an inert organic solvent.

According to a preferred embodiment, equimolar amounts of the compounds of formula VII and VIII are used, and the reaction is carried out in the presence of a base.

Suitable leaving groups "X" for use in this reaction are well known to those skilled in the art. They include sem mentioned above, e.g. fluoride,

2 2

chlorine, bromine, iodine, -0-.SR , where R denotes lower-alkyl (e.g. methanesulfonate), -03SR 3 , where R 3 denotes aryl or substituted aryl (e.g. benzenesulfonate, p-bromobenzenesulfonate or p- toluene sulfonate), -O^SF, acetoxy and 2,4-dinitrophenoxy. For practical and economic reasons, it is usually preferred to use compound VII, where X is chlorine.

In the aforementioned method, the compound VII is preferably used in the form of an acid addition salt. The compound VII is relatively unstable in the form of a free base and is therefore preferably prepared and stored as an acid addition salt. Although the free base form of the compound of formula VII can be regenerated during the reaction, no advantage is gained by doing so. The person skilled in the art will be able to understand that any inorganic acid or organic acid can be used to form the acid addition salt of compound VII, e.g. hydrochloric acid., sulphamic acid, sulfuric acid, oxalic acid, benzoic acid, succinic acid, acetic acid, nitric acid, citric acid or the like. For practical and economic reasons, it is usually preferred to use compound VII in the form of the hydrochloride.

The reaction of compounds VII and VIII to produce compound I can be carried out in any organic solvent, such as an alkanol, acetonitrile, dimethylformamide, dimethylsulfoxide, acetone, etc. It is preferred to carry out the reaction in an alkanol, such as ethanol or 2-propanol.

The reaction temperature is not critical, and the reaction can be carried out at temperatures from 0 to approx. 200°C. At low temperatures, the reaction is slow, while high temperatures usually lead to less pure products due to decomposition and the formation of by-products. It is usually preferred to carry out the reaction at room temperature.

The reaction of compounds VII and VIII to produce compound I is preferably carried out in the presence of a base which facilitates the reaction by acting as an acid acceptor. Suitable bases for use in this reaction include both inorganic and organic bases, such as NaOH, KOH, LiOH, triethylamine, dimethylaniline, sodium ethoxide and the like.

This process is illustrated by reaction core IV below for the preparation of a preferred compound.

The invention further relates to previously unknown intermediates with the general formula:

where R<1> denotes a straight-chain or branched alkynyl group containing from 3-9 carbon atoms, as well as acid addition salts thereof, which are valuable for the production of histamine H2-receptor antagonists of formula I. According to a preferred embodiment, R denotes in the compound of formula VIII in which R 4 denotes hydrogen or methyl; according to another preferred embodiment, R means -(CH2)nCsCR 4 , where n is an integer from 1-6 and R 4 means hydrogen or methyl; according to a further preferred embodiment R<1> means

where R 4 means hydrogen or methyl.

According to a more preferred embodiment, R" in the compound of formula VIII means the 2-butyn-1-yl group; according to a further and more preferred embodiment, R means the 3-.butyn-1-yl group; according to a further and more preferred embodiment R₁" means the 4-pentyn-1-yl group; according to a further and more preferred embodiment, R means the 2-methyl-3-butyn-2-yl group; according to a further and more preferred embodiment, R means the 3-butyn-2-yl group. According to the most preferred embodiment, R"*" in the compound of formula VIII means the propargyl group.

The intermediate products in the analog method according to the invention have the formula:

and these are obtained by reacting a compound of the formula: where P denotes a suitable sulfhydryl protecting group, a compound of the formula:

after which the sulfhydryl protecting group is removed from the resulting compound to form intermediate VIII.

This procedure is explained in form V below.

The dimethylcyanodithioiminocarbonate, which is used as a starting material for the preparation of the N-cyano-N'-alkynyl-S-methylisothiourea substances, can itself be prepared by means of methods described in "J. Org. Chem.", 32, 1566 (1967 ). The alkynyl starting materials are either commercially available or can be prepared by methods described in "Bull. Soc. Chim. Fr.", 490 (1958); "Bull. Soc. Chim. Fr.", 592 (1967) and "Annales de Chimie" (Paris), 3, 656 (1958).

When cystamine hydrochloride is reacted with an N-cyano-N'-alkynyl-S-methylisothiourea to produce an N-cyano-N<1->alkynyl-N"-(2-mercaptoethyl)guanidine of formula VIII, it has been shown it is desirable to carry out the reaction in the presence of a small amount of hydroquinone and bubble nitrogen through the reaction mixture (see, for example, step B in Ex. 14). These reaction conditions have been shown to give compounds of formula VIII in higher yields and with a higher degree of purity. The nitrogen purge is believed to remove the methyl mercaptan formed during the reaction and thereby prevent secondary reactions caused by the addition of methyl mercaptan to the carbon-carbon triple bond.It is believed that the hydroquinone prevents the formation of free radicals and the occurrence of secondary reactions due to their presence.

In the present description, the term non-toxic, pharmaceutically acceptable acid addition salt means the mono- or di-salt of a compound prepared according to the invention with a non-toxic, pharmaceutically acceptable organic or inorganic acid. Such acids are known and include e.g. hydrochloric acid, hydrobromic acid, sulfuric acid, sulfamic acid, phosphoric acid, nitric acid, maleic acid, fumaric acid, succinic acid, oxalic acid, benzoic acid, methanesulfonic acid, ethanedisulfonic acid, benzenesulfonic acid, acetic acid, propionic acid, tartaric acid, citric acid and camphorsulfonic acid. The salts are produced in a manner known per se.

The term lower-alkyl refers to straight-chain or branched alkyl groups containing from 1-6 carbon atoms.

For therapeutic use, the pharmacologically active compounds of this invention are usually administered as a pharmaceutical preparation comprising, as essentially active ingredient, at least one such compound in base form or in the form of a non-toxic, pharmaceutically acceptable acid addition salt in connection with a pharmaceutically acceptable carrier .

The pharmaceutical preparations can be administered orally, parenterally or rectally as suppositories. A wide variety of pharmaceutical forms can be used. If a solid carrier is used, the preparation can thus be tableted, placed in a hard gelatin capsule in powder or pill form, or in the form of a pastille or a bolche. If a liquid carrier is used, the preparation can be a syrup, an emulsion, a soft gelatin capsule, a sterile injection solution or an aqueous or non-aqueous liquid suspension. The pharmaceutical preparations are produced using conventional methods, which are suitable for the desired preparation form.

Preferably, each dosage unit contains the active ingredient in an amount from approx. 50 mg to approx. 250 mg, and it is most preferred to use amounts from approx. 100 mg to approx. 200 mg. The active ingredient is preferably given in equal doses from 2-4 times a day. The daily dose interval will preferably be from 250 mg to approx. 1000 mg and most preferably from approx. 500 mg. to approx. 750 mg.

It has been demonstrated that histamine I^-receptor antagonists are effective inhibitors of gastric acid secretion in animals and humans,

see Brimblecombe et al., in "J. Int. Med. Res.", 3, 86 (1975). Clinical evaluation of the histamine I^-receptor antagonist, cimetidine, has shown it to be an effective therapeutic agent in the treatment of pepsin ulcers, see Gray et. al., in "Lancet", 1 (8001), 4

(1977). The compound prepared in examples 1 and 2 below (hereafter called BL-5641) has been compared with cimetidine in various tests and has been shown to be more potent than cimetidine both as a histamine I^ receptor antagonist in isolated guinea pig atria, and as an inhibitor for gastric secretion in rats and dogs. Furthermore, gastric secretion studies in dogs suggest that BL-5641 has a longer duration of action than cimetidine at the same doses.

Histamine H^-receptor antagonism studies

on isolated guinea pig atria

Histamine induces concentration-related increases

in the contractile velocity of isolated spontaneously beating guinea pig right atria. Black et al., described in "Nature", 236, 385

(1972) the receptors involved in this effect of histamine

as histamine H-j receptors, when they reported the properties of burimamide, a competitive antagonist for these receptors. Subsequent investigations by Hughes and Coret, "Proe. Soc.

Exp. Biol. Med.", 148, 127 (1975) and Verma and McNeill, "J. Pharma-col. Exp. Ther.", 200, 353 (1977), supports the conclusion of Black et al., which states that the positive chronotropic effect of histamine in isolated right guinea pig atria is mediated via histamine H2-receptors. Black et al. in "Agents and Actions", 3, 133 (1973) and Brimblecombe et al. in "Fed. Proe", 35, 1931

(1976) have used isolated right guinea pig atria as a means

to compare the activities of histamine H2-receptor antagonists. The present comparative studies were carried out using a modification of the method described by Reinhardt et al. in Agents and Actions, 4, 217 (1974).

Male guinea pigs of the Hartley strain with a body weight of 350-

450 g was killed by a blow to the head. The heart was excised and placed in a Petri dish containing oxygenated (95% O^, 5% CO 2 ) modified Krebs solution (g/l: NaCl 6.6, KCl 0.35, MgSO 4 .7H 2 O 0.295, KH 2 PO 4 0.162 , CaCl2 0.238, NaHCO3 2.1 and dextrose 2.09). The spontaneously beating right atrium was dissected free of

other tissue, and a silk thread (4-0) was attached to each end. The atrium was suspended in a 20 ml muscle chamber containing oxygenated modified Krebs solution, which was maintained at 32°C. Atrial contractions were recorded isometrically using a "Grass FT" 0.03 force displacement transducer, and recordings of contractile force and velocity were made with a "Beckman RP Dynograph".

The atrium is subjected to a resting tension of 1 g and allowed to equilibrate for 1 hour. After the equilibration period had expired, a submaximal concentration of histamine dihydrochloride (3 x 10 M) was added to the bath and washed out to prime the tissue. Next, histamine was added to the bath in a cumulative manner using one \log 10 intervals, so that

-7-5 achieved molar end-bath concentrations of 1 x 10 to 3 x 10 The histamine-induced increase in atrial rate was allowed

to stabilize before the next successive concentration was added. The maximal response invariably occurred at a concentration of 3 x 10 2 M. The histamine was washed out several times, and the atrium was allowed to return to the control rate. The test compound (1 x 10 ^ M) was then added, and after 30 minutes of incubation, the histamine concentration reaction was repeated adding higher concentrations as needed.

The histamine ED^^ values (the concentration of histamine which increased the contractile velocity by 50% of maximum) and 95% significance limits before and after addition of the test compound were obtained by regression analysis as described by Finney, in "Probit Analysis", 3rd ed. , Cambridge (1971). The concentration-response curve shift factors were calculated as follows:

The factor obtained for BL-5641 was then expressed relative to the factor obtained for cimetidine.

The results obtained in these studies are summarized

in Table I. Cimetidine and BL-5641 shifted the histamine concentration-response curve to the right by a factor of, respectively. 6.6 and 32.7. Based on the concentration-response curve shift factors

was BL-5641 approx. 5.7 times more active than cimetidine as a histamine H^-receptor antagonist in isolated right guinea pig atria.

Determination of gastric antisecretory activity

in the 2 Hour Pyloric Banded (Shay) Rat The pyloric ligation procedure in the rat was devised by Shay et al., "Gastroenterology", 5.53 (1945) for the study of perforating gastric ulcers; however, when the method became known, it was also used as a means of studying the gastric secretion of the rat, Shay et al., "Gastroenterology", 26, 906 (1954), Brodie, D.A., "Am. J. Dig. Dis.", 11, 231 (1966). A modification of this procedure is used today to assess compounds for gastric antisecretory activity.

Male Long Evans rats with a body weight of 280-300 g are used. The animals are placed in individual cages and starved for 24 hours with free access to water. Under ether anesthesia, the stomach is accessed through a midline incision, and a ligature of cotton thread is placed around the pylorus. After closure of the wound, the ether administration is stopped and either BL-5641, cimetidine or a vehicle is administered intraperitoneally in a volume of 1 mg/kg. BL-5641 and cimetidine were dissolved with one equivalent of HCl and brought to the correct volume with water. The animals are placed back in their cages from which the water bottles have been removed, and they are killed 2 hours later with ether. The stomach is removed, and the two-hour stomach collection is emptied into a graduated test tube to determine the volume. Titratable acidity is measured by titrating a 1 ml sample to pH 7.0 with 0.02N NaOH using an autoburette and an electrometric pH meter (Radiometer). The titratable amount of acid is calculated in microequivalents by multiplying the volume in ml by the acid concentration in milliequivalents per litres. The percentage inhibition of acid release is calculated as follows:

The results obtained with BL-5641 and cimetidine are shown in Table 2.

These results show that BL-5641 is at least as potent as cimetidine in the two-hour pyloric ligation test in rats for the inhibition of gastric acid secretion.

Determination of gastric antisecretory activity

in dogs with gastrocolic fistula

Thomas-type stainless steel cannulas [Thomas, J.E., "Proe. Soc. exp. Biol. Med.", 46, 260 (1941)] were inserted into the abdomen of beagle dogs weighing 10-12 kg near the pyloric gland area when the greater curvature for the provision of a chronic gastrocolic fistula. The animals are allowed to recuperate for at least 2 months before any testing is carried out. The dogs fast overnight

(approx. 18 hours) with water ad libitum before each experiment. The dogs are placed in a sling and an approx. 20.3 cm needle insertion catheter with an approx. A 5 cm needle No. 17 is inserted into a leg vein for use in administering the medicine. Gastric secretions are collected every 15 minutes by gravity drainage from the open cannula. Basal secretions are collected in 2 successive 15-minute periods, and if these prove to be too large (>4 ml/15 min.; pH <5.0), the animal is not used. A modification of the method described by Grossmann and Konturek in "Gastroenterology", 66, 517 (1974) was followed. Immediately after the second basal collection, histamine was infused (100 µg/kg/hour) for 90 minutes using a Harvard infusion pump at a volume of 6 ml/hour. At this time either BL-5641, cimetidine (dissolved with one equivalent of HCl and brought to the correct volume with normal saline) or normal saline was injected rapidly (within 30 sec.) in a volume of 0.1 ml/kg, and then the infusion of histamine was continued for another 150 min. (total infusion time is 4 hours). Every 15 minute sample of gastric juice was measured to the nearest 0.5 ml, and titratable acidity against 0.02N NaOH (end point pH 7.0) was measured with an autoburette and pH meter (Radiometer). The percentage inhibition of acid release is calculated as described in connection with the pyloric ligation experiment on rats.

Equimolar doses of BL-5641 and cimetidine were administered to

5 different dogs, and the results obtained are indicated in the table

III.

Both BL-5641 and cimetidine produced an immediate inhibitory effect on gastric acid secretion. However, the degree of inhibition at equimolar doses was consistently greater and of longer duration with BL-5641 than with cimetidine. These results show that BL-5641 as an inhibitor of histamine-induced gastric acid secretion

lence in dogs is more potent and/or longer acting than cimetidine.

The invention shall be explained in more detail by means of the following examples.

Example 1

N- cyano- N'-{ 2-[( 4- methyl- 5- imidazolyl) methylthio] ethyl}- N"- propargylguanidine

A mixture of 3.00 g or 0.0111 mol of N-cyano-N'-{2-[(4-methyl-5-imidazolyl)methylthio]ethyl}-S-methylisothiourea

and 2.50 g or 0.045 mol of propargylamine in 60 ml of acetonitrile was stirred under reflux for 65 hours and then heated in a stainless steel pressure vessel to 120-130°C for 38 hours. The reaction mixture was cooled, decanted from a tar and then evaporated to give 3.57 g of a gum. This material was placed on silica gel (100-200 mesh) and eluted with a mixture of 97 parts methylene chloride and 3 parts methanol. The product obtained from a middle fraction was crystallized by trituration under acetonitrile and then recrystallized from acetonitrile to give 0.236 g or 7.7% of the title compound - melting point 146-149.5°C.

Analysis calculated for: C]_2Hi6N6S: C 52.15; H 5.83; N 30,41. Found: C 51.86; H 5.81; N 30.70.

Example 2

N- cyano- N'-{ 2-[( 4- methyl- 5- imidazolyl) methylthio] ethyl}~ N"- propargylguanidine

a. N- cyano- N'- propargyl- S- methylisothiourea ( A)

A solution of 16.00 g or 0.109 mol of dimethyl cyanodithioiminocarbonate and 6.03 g or 0.109 mol of propargylamine in 320 ml of acetonitrile was stirred under reflux for 4 hours and then at 25°C for 12 hours. Workup gave the title compound A in an amount of 13.58 g or 81% and with a melting point of 160-164°C.

b. N-cyano-N'-{2-[(4,-methyl-5-imidazolyl)methylthio]ethyl}-N"-propargylguanidine

A solution of 11.71 g or 0.0765 mol of A and 13.10 g or 0.0765 mol of 2-[(4-methyl-5-imidazolyl)methylthio]ethylamine in 250 ml of methanol was heated under reflux for 64 hours. The solvent was removed by evaporation, and the residue was applied to silica gel (100-200 mesh) and chromatographed by gradient elution using methylene chloride/methanol; the latter fractions yielded 4.0 g of the title compound. Recrystallization from acetonitrile gave purified product with melting point 150-152.5°C which was identical (ir, nmr, tic) to the product prepared in ex. 1.

Example 3

N-cyano-N'-{2-[(4^methyl-5-imidazolyl)methylthio]ethyl}-N"-2-butyn-1-yl)guanidine

a. N-(2-butyn-l-yl)-N'-cyano-S-methylisothiourea (B)

A solution of 10.00 g or 0.0684 mol of dimethylcyano-dithioiminocarbonate and 4.73 g or 0.0684 mol of 2-butyn-1-amine in 200 ml of acetonitrile is stirred at 25°C for 0.5 hour and then under reflux for 2.5 hours. The mixture is cooled and then filtered to obtain the title compound B with melting point 180-183°C.

b. N-cyano-N'-{2-[(4-methyl-5-imidazolyl)methylthio]ethyl}-N"-(2-butyn-1-yl)guanidine

A solution of 6.82 g or 0.0407 mol B and 6.98 g

or 0.0407 mol of 2-[(4-methyl-5-imidazolyl)methylthio]ethylamine in 140 ml of methanol is heated under reflux for 40 hours. Processing and chromatography as described above in ex. 2, gave the title compound. When the title compound was prepared according to the usual method according to ex. 1, it melted at 128-130°C.

Example 4

N- cyano- N'-{ 2-[( 4- methyl- 5- imidazolyl) methylthio] ethyl}- N"-( 4- pentyn-1- yl) guanidine

The usual procedure according to e.g. 1 was repeated, except that the propargylamine used therein was replaced by an equimolar amount of 4-pentyn-1-amine, and the title product was thereby prepared with a melting point of 99-103°C.

Example 5

N-cyano-N'-{2-[(4-methyl-5-imidazolyl)methylthio]ethyl)-N"-(2-butyn-1-yl)guanidine

A mixture of 3.00 g or 0.0111 mol of N-cyano-N'-{2-[(4-methyl-5-imidazolyl)-methylthio]ethyl}-S-methylisothiourea and 3.07 g or 0.0445 mol of 2-butyn-1-amine in 60 ml of propionitrile was stirred under reflux for 40 hours. TLC analysis of an aliquot of the reaction mixture showed traces of the isothiourea starting materials, so the mixture was refluxed for an additional 6 hours and then stirred at room temperature for 64 hours. The solvent together with an excess of amine was removed

under reduced pressure, and the remaining gum was placed on silica gel (100-200 mesh) and eluted with a mixture of 97 parts methylene chloride and 3 parts methanol. The middle fractions were combined and evaporated to give 1.81 g of yellow gum. The gum was dissolved in 20 ml of ethyl acetate and crystallized at -15°C. The resulting pale yellow solid in an amount of 1.2 g was

dissolved in 11 ml of hot acetonitrile and recrystallized at -15°C, and a yield of 1.072 g with melting point 128-130°C was obtained.

Analysis calculated for C^H^gNgS:

C 53.77; H 6.25; N 28.94; S 11.08. Found: c 53.72; H 6.29; N 29.62; S 11,34.

Example 6

N-cyano-N'-{2-[(4-methyl-5-imidazolyl)methylthio]ethyl}-N"-(3-butyn-1-yl)guanidine

A mixture of 3.00 g or 0.0111 mol of N-cyano-N<1->{2-[(4-methyl-5-imidazolyl)-methylthio]ethyl}-S-methylisothiourea and 3.13 g or 0.453 mol of 3-butyn-1-amine in 60 ml of propionitrile was stirred at reflux for 40 hours. The solvent was evaporated to give 5.40 g of a syrup which was applied to 70 g of 100-200 mesh silica gel and chromatographed by gradient elution using methylene chloride/methanol.

TLC (silica gel, 90 CH 2 Cl 2 /10 MeOH) indicated that fractions 9-12 were pure and should be combined. Fractions 1-8 showed fast moving impurities. Fractions 13 and 14 showed some subsequent impurities. Fractions 9-12 were combined and evaporated to 1.72 g of a yellow gum. The gum was dissolved in 11 mL of nitromethane and crystallized at -15°C to give 1.18 g of a pale yellow solid which was recrystallized from 9 mL of nitromethane to give 0.987 g, mp 86-89°C, after softening at 85°C.

IR and NMR (100 MHZ) were clean and consistent with the desired structure. NMR showed the product was solvated with approx. 0.08 mol of nitromethane.

Analysis calculated for C-^H^NgS > 0 r 0 , 8 (CH3N02) :

C 53.21; H 6.22; N 28.84; S 10.86. Found: C 52.68; H 6.28; N 29.39; S 11,22.

52.87; 6.02; 29.50;

Example 7

N-cyano^N1-{2-[(4-methyl-5-imidazolyl)methylthio]ethyl}-N"-(4-pentyn-1-yl)guanidine

A mixture of 3.00 g or 0.0111 mol of N-cyano-N'-{2-[(4-methyl-5-imidazolyl)-methylthio] ethyl}-S-methylisothiourea and 3.69 g or 0.0445 mol of 4-pentyn-1-amine in 60 ml of acetonitrile was stirred under reflux for 24 hours and then allowed to stand at room temperature for 96 hours. The solvent and excess amine were removed under reduced pressure and the remaining yellow gum was purified by chromatography on 50 g of 100-200 mesh silica gel using gradient elution with methylene chloride/methanol (99:1-96:4). The middle fractions which were found to be pure by TLC were combined and evaporated to give 1.91 g of yellow gum, which was crystallized from 18 ml of ethyl acetate at -15°C. The resulting white solid in an amount of 1.25 g was recrystallized at -15°C from 10 ml of acetonitrile, and 1.063 g of the product with melting point 99-103°C was obtained.

Analysis calculated for C^^H^øNgS:

C 55.24; H 6.52; N 27.61; S 10.53. Found: C 55.43; H 6.58; N 28.26; P10.97.

Example 8

N- cyano- N'-{ 2-[( 4- methyl- 5- imidazolyl) methylthio] ethyl}- N"-propargylguanidine

A mixture of 10.0 g or 0.0371 mol of N-cyano-N'-{2-[(4-methyl-5-imidazolyl)methylthio]ethyl}-S-methylisothiourea and 20 ml or 0.325 mol of distilled propargylamine in 50 ml of methanol was stirred under reflux under a pressure of nitrogen atmosphere (nitrogen purge) for 20.5 hours. The solvent and excess amine were then removed by evaporation, leaving a tan oil which crystallized easily. Trituration of the crude product under 30 ml of isopropanol gave the title compound as a whitish fragile solid in an amount of 8.11 g or 79%. The melting point was 146-148.5°C.

Example 9

N- cyano- N'-{ 2-[( 4- methyl- 5- imidazolyl) methylthio] ethyl}- N"-propargylguanidine

A mixture of 100 g or 0.371 mol of N-cyano-N'-{2-[(4-methyl-5-imidazolyl)methylthio]ethyl}-S-methylisothiourea and 150 ml or 2.44 mol of distilled propargylamine in 500 ml of methanol was stirred under reflux under a pressure of nitrogen atmosphere (nitrogen purge) for 22 hours. The reaction mixture was cooled and the solvent and excess amine were removed by evaporation, leaving an amber oil which readily crystallized. The crude product was triturated under 250 ml of isopropanol, cooled at 0°C for 2 hours and collected by filtration. The filter cake was washed with cold isopropanol and dried in vacuum over P2°5 for 16 hours. The dried title product was an off-white dense solid in a yield of 73.5 g or 71.7%. The melting point was 147-149°C.

Example 10

Recrystallization of N-cyano-N'-{2-[(4-methyl-5-imidazolyl)-methylthio]ethyl}-N"-propargylguanidine

The end products obtained in ex. 11 and 12 are combined, giving a total of 81.3 g, and this amount is dissolved in 1000 ml of hot isoproanol, filtered through "Super-Cel" and allowed to cool at room temperature for approx. 68 hours. The resulting crystalline product was obtained by filtration, was washed with cold isopropanol, powdered and dried in a heated desiccator under high vacuum for approx. 45 hours. The yield was 72.4 g or 89%, the melting point was 149-151°C. HPLC analysis showed that the purity was approx. 99.5%. The NMR spectrum at 100 MHz was clean and consistent.

Analysis calculated for C,_H,,N,S:

C 52.15; H 5.83; N 30.41; S 11.60. Found: C 52.42; H 5.94; N 30.51; S 11.35.

Example 11

N- cyano- N'-{ 2-[( 4- methyl- 5- imidazolyl) methylthio] ethyl}- N"-propargylguanidine

A. N-cyano-N'-propargyl-S-methylisothiourea

A solution of 16.00 g or 0.109 mol of dimethylcyanodithioiminocarbonate and 6.03 g or 0.109 mol of propargylamine in 320 ml of acetonitrile was stirred under reflux for 4 hours and then at 25°C for 12 hours. The mixture was cooled and filtered, and the title compound was obtained in an amount of 13.58 g or 81%. The melting point was 160-164°C.

B. N- cyano- N'- propargyl- N"-( 2- mercaptoethyl) guanidine

A mixture of 1.136 g or 10 mmol of cysteamine hydrochloride, 1.53 g or 10 mmol of the product from step A above and 0.055 g of hydroquinone in 10 ml of DMF was heated slightly to solution. To this solution was added 10 ml of 1N aqueous sodium hydroxide, and nitrogen was bubbled through the solution. After standing at room temperature for 17 hours, the reaction mixture was evaporated to dryness to form a mixture of the title product and sodium chloride. The title product was extracted from this mixture with 10 ml of ethanol and the ethanolic solution was used in step C below.

C. N-cyano-N'-{2-[(4-methyl-5-imidazolyl)methylthio1ethyl}-N"-propargylguanidine

The ethanol solution of the product from step B above, approx. 10 mmol, was added to a solution of 0.46 g of sodium (0.02 g atoms) in 10 ml of ethanol at 4°C under nitrogen. After 5 minutes, a solution of 1.67 g or 10 mmol of 4-methyl-5-chloromethylimidazole, HCl in 14 ml of ethanol was added. The mixture was stirred at room temperature under nitrogen for 70 . my. The reaction mixture was filtered through a pad of celite filter aid to remove inorganic salts, and the celite was washed with ethanol. The filtrate was evaporated to dryness and the product was purified by chromatography on a silica gel column (20 g silica gel, 3.2 x 4.5 cm layer) with ethanol-chloroform mixtures as solvent. The ethanol content was increased gradually from 2-15%. The eluent was evaporated to dryness, yielding 1.906 g of crystalline product. Recrystallization from 2-propanol gave 1.49 g or 54% of the title product with melting point 144-145°C.

Claims (2)

1. Analogue procedure for the preparation of a therapeutically active compound of the general formula: where R 1 denotes a straight-chain or branched alkynyl group with from 3-9 carbon atoms or a non-toxic, pharmaceutically acceptable acid addition salt thereof, characterized in that one a) in a non-reactive solvent at a temperature above room temperature reacts a compound with the formula or an acid addition salt thereof, with a compound of the formula: 1 Dd where R has the meaning given above and R and R are H or the group: where R denotes any such substituent, that SR is a suitable leaving group with an amino group, preferably lower alkyl, aryl, substituted aryl, aralkyl, CH2CN, CH^COOH or an ester or salt thereof, or b) in an inert organic solvent reacts a for bond with the formula: or an acid addition salt thereof, where X denotes hydroxy or a conventional leaving group with a mercapto group, preferably fluorine, chlorine, bromine, iodine, -0,SR 2 , where R 2 is lower alkyl, -O^SR 3 , where R 3 is aryl or substituted aryl, -O^SF, acetoxy or 2,4-dinitrophenoxy with a compound of the formula: where R 1 has the meaning given above, and that, if desired, the resulting compound of formula I is converted in base form or an acid addition salt thereof to the corresponding non-toxic thereof or the free base form. 2. Method according to claim 1 for the production of N-cyano-N<1->{2-[(4-methyl-5-imidazolyl)methylthio]ethyl}~N"-propargylguanidine or a non-toxic pharmaceutically acceptable acid addition salt thereof, characterized by. that starting materials are used where R 1 is -CH2C- =CH.