Substituted 2-Phenylamino-1,3-Tetrahydro-2-Pyrimidines and Salts Thereof

This invention relates to novel substituted 2-phenylamino-1,3-tetrahydro-2-pyrimidines and non-toxic acid addition salts thereof, to various methods of preparing these compounds, to pharmaceutical compositions containing them as active ingredients, and to methods of using them as bradycardiacs.

More particularly, the present invention relates to a novel class of 2-phenylamino-1,3-tetrahydro-2-pyrimidines represented by the formula ##STR3## wherein R is a radical selected from the group consisting of ##STR4##

and non-toxic, pharmacologically acceptable acid addition salts thereof.

The compounds of Formula I may be prepared by the following methods:

By reacting 2-(2,6-dibromophenylimino)-1,3-diazacyclohexane of formula ##STR5## with a halide of general formula

wherein Hal represents a chlorine, bromine, or iodine atom and R is as defined above.

By reacting a compound of general formula ##STR6## wherein R is as defined above for formula I and

A represents a cyano group or the group ##STR7## where Y is an alkoxy group having from 1 to 4 carbon atoms, an alkylthio group having from 1 to 4 carbon atoms, a sulfhydryl group or amino group,

with 1,3-diamino-propane or an acid addition salt thereof.

In the alkylation of the 2-arylimino-1,3-diazocyclohexane of Formula II pursuant to Method A, the substitution is effected exclusively at the bridge nitrogen atom. In the reaction pursuant to Method B, the structure of the end product is determined by the synthesis. The position of the substituent may also be determined by NMR-spectroscopy. [cf., H. Stahle et al., Liebigs Ann. Chem. 751, 159 et seq. (1971)].

It is advantageous to effect the reaction according to Method A by heating the reaction partners, preferably in the presence of a polar or non-polar organic solvent, to temperatures of about 50.degree. to 150.degree. C. The specific reaction conditions depend to a great extent upon the reactivity of the reaction partners. It is recommended to provide the halide for the alkylation in excess and to perform the reaction in the presence of an acid-binding agent.

Method B is required to be performed at elevated temperatures between 60.degree. and 180.degree. C. Solvents are not necessary. It is advantageous to provide the 1,3-diamopropane or its acid addition salt in excess.

The starting compounds of the Formula II are described, for example, in Belgian Pat. Nos. 623,305, 687,657, and 705,944, incorporated herein by reference.

The starting compounds of the Formula III may be prepared by halogenating the corresponding primary alcohol.

The compounds of the Formula IV are obtained, starting from anilines, by reaction with compounds of Formula III and subsequent reaction of the secondary amines formed thereby with cyanates or thiocyanates, whereby ureas or thioureas are formed. Ureas and thioureas may then be converted by alkylation agents into corresponding isouronium salts or isothiouronium salts. From these acid addition compounds the corresponding isoureas or isothioureas may be obtained with bases. By splitting off water from ureas or splitting off H.sub.2 S from thioureas by means of lead or mercury salts, cyanamides are obtained which may be converted into guanidines by addition of ammonia.

The 2-phenylamino-2-tetrahydro-2-pyrimidines embraced by Formula I are organic bases and therefore form acid addition salts with inorganic or organic acids. Examples of non-toxic, pharmacologically acceptable acid addition salts are those formed with, for example, hydrochloric acid, hydrobromic acid, hydriodic acid, hydrofluoric acid, sulfuric acid, phosphoric acid, nitric acid, acetic acid, propionic acid, butyric acid, caproic acid, valeric acid, oxalic acid, malonic acid, succinic acid, maleic acid, fumaric acid, lactic acid, tartaric acid, citric acid, malic acid, benzoic acid, p-hydroxybenzoic acid, p-aminobenzoic acid, phthalic acid, cinnamic acid, salicylic acid, ascorbinic acid, methanesulfonic acid, 8-chlorotheophylline, or the like.

The compounds of the present invention, that is, those embraced by Formula I above and their non-toxic, pharmacologically acceptable acid addition salts, have useful pharmacodynamic properties. More particularly, they exhibit very strong bradycardiac activity in warm-blooded animals, such as rabbits and rats, including spinal rats and intact, narcotized rats, and are therefore useful for the treatment of coronary diseases.

For pharmaceutical purposes the compounds of the present invention are administered to warm-blooded animals perorally or parenterally as active ingredients in customary dosage unit compositions, that is, compositions in dosage unit form consisting essentially of an inert pharmaceutical carrier, galenic excipient, disintegrant, lubricant, or substance for obtaining sustained release and one effective dosage unit of the active ingredient, such as tablets, coated pills, capsules, wafers, powders, solutions, suspensions, emulsions, syrups, suppositories, and the like. One effective dosage unit of the compounds according to the present invention is from 0.0017 to 1.33 mg/kg body weight, preferably 0.017 to 0.5 mg/kg body weight.

The following examples illustrate the present invention and will enable others skilled in the art to understand it more completely. It should be understood, however, that the invention is not limited solely to the particular examples given below.

A mixture of 7.7 g (0.02 mol) of 2-(2,6-dibromophenylimino)-1,3-diazacyclohexane with 2.26 g (125%) of chloromethylcyclopropane and 5 ml of triethylamine in 25 ml of dried toluene was heated in a reaction vessel for 18 hours at 125.degree. C. After the solvent was evaporated in vacuo, the remainder was dissolved in dilute hydrochloric acid, and the acid solution was extracted several times with ether. The ethereal extracts were discarded. After treatment with active charcoal, the hydrochloric acid solution phase was then fractionally extracted with ether at stepwisely increasing pH values (addition of 2 N sodium hydroxide solution), whereby about ten ethereal extracts were obtained. The fractions, which contained the desired compound in pure form (determination by thin-layer chromatogram), were combined and dried over calcium sulfate, and then ether was evaporated therefrom, in vacuo. The yield was 0.35 gm (4.5% of theory) of the tetrahydropyrimidine derivative, which crystallized after stirring with petroleum ether. The melting point of the product was 128.degree.-130.degree. C.

Using procedures analogous to those described in Example 1, the compounds of Formula I shown in the table below were also prepared. The melting points are those of the free bases, unless the salt form is otherwise indicated.

The following examples illustrate a few pharmaceutical dosage unit compositions comprising a compound of the present invention as an active ingredient and represent the best modes contemplated of putting the invention into practical use. The parts are parts by weight unless otherwise specified.

Coated tablets

The tablet, or pill, core composition can be compounded from the following ingredients:

Preparation:

The active ingredient is admixed with a portion of the excipients, the mixture is thoroughly kneaded with an aqueous solution of the soluble starch, the moist mass is granulated through a screen, and the granulate is dried. The dry granulate is admixed with the remainder of the excipients, and the composition is compressed in 250 mg tablet cores which are subsequently coated with a thin shell consisting essentially of a mixture of sugar, talcum, and gum arabic. Each coated tablet is an oral dosage unit composition containing 5 mg of the active ingredient.

Hypodermic solution

The solution can be compounded from the following ingredients:

Preparation:

The active ingredient and the sodium chloride are dissolved in the distilled water, the solution is filtered until free from suspended particles, and the filtrate is filled under aseptic conditions and in an atmosphere of nitrogen into 2 cc-ampules which are then sterilized and sealed. The contents of each ampule are an injectable dosage unit composition containing 1 mg of the active ingredient.

Drop solution

The solution can be compounded from the following ingredients:

Preparation:

The active ingredient and the p-hydroxy-benzoates are dissolved in the demineralized water, the solution is filtered, and the filtrate is filled into 100 ml-bottles equipped with a dropping spout. An amount of 10 cc of the solution is an oral dosage unit composition containing 2 mg of the active ingredient.

Any one of the other compounds embraced by Formula I or a non-toxic, pharmacologically acceptable acid addition salt thereof may be substituted for the particular active ingredient in Examples 7 through 9. Likewise, the amount of active ingredient in these illustrative examples may be varied to achieve the dosage unit range set forth above, and the amounts and nature of the inert pharmaceutical carrier ingredients may be varied to meet particular requirements.

While the present invention has been illustrated with the aid of certain specific embodiments thereof, it will be readily apparent to others skilled in the art that the invention is not limited to these particular embodiments and that various changes and modifications may be made without departing from the spirit of the invention or the scope of the appended claims.