Abstract:
Antimicrobial bis-(pyrrolidonyl alkylene) biguanides having the formula: 
     
       A--Z--A 
     
     where A is: ##STR1## X is C 2  -C 4  alkylene; and Z is a bivalent bridging group, and acid addition salts thereof, 
     are provided herein.

Description:
BACKGROUND OF THE DISCLOSURE 
     1. Field of the Invention 
     This invention relates to bisbiguanide derivatives, and, more particularly to bis-(pyrrolidonyl alkylene) biguanide derivatives having antimicrobial activity. 
     2. Description of the Prior Art 
     Bisbiguanides are well known as antimicrobial agents. See, for example, U.S. Pat. Nos. 3,468,898; 4,022,834; 4,567,174; and 4,670,592. The bisbiguanide known as chlorhexidine, or, chemically, 1,6-bis(4-chlorophenylbiguanido)-hexane, is a widely used antimicrobial compound; its formula is: 
     
         A--Z--A 
    
     where A is: ##STR2## and Z is --CH 2  -- 6 . 
     However, chlorhexidine is known to have many deficiencies, including: (1) the presence of a mutagenic p-chloroaniline moiety*; (2) low water solubility for the free base; (3) inactivity against bacterial spores at room temperature; (4) an antibacterial activity which is pH dependent in the range of pH 5-8, and which deteriorates at a pH below 5; and (5) incompatability in formulations containing surface active agents. 
    
     (2) Prasad, I, &#34;Mutagenic Effects of the Herbicide 3&#39;,4&#39;-Dichloropropionanilide and its Degradation Products&#34;, Can. J. Microbiol 16, 369-372 (1970). 
     Accordingly, it is an object of this invention to provide new and improved antimicrobial bis-biguanide derivatives. 
     A particular object of the invention is to provide novel antimicrobial biguanides having enhanced water solubility properties, low toxicity and better compatability with surfactants. 
     These and other objects and features of the present invention will be made apparent from the following particular description thereof. 
     DETAILED DESCRIPTION OF THE INVENTION 
     In accordance with the present invention, a bis-pyrrolidonyl moiety is introduced into bisbiguanides represented by chlorhexidine and other related compounds. The bis-pyrrolidonyl group in the bisbiguanide provides enhanced water solubility and decreased toxicity as compared to the p-chloroaniline moiety. 
     The bis-(pyrrolidonyl alkylene) biguanides of the invention have the following formula: 
     
         A--Z--A 
    
     where 
     A is: ##STR3## 
     X is C 2  -C 4  alkylene, e.g. ethylene, propylene and butylene; 
     Z is C 2  -C 12  alkylene, which optionally may be interrupted, as by oxygen atoms, and also may incorporate cyclic nuclei which themselves may be saturated or unsaturated, and acid addition salts thereof. 
     The bridging group Z between the biguanides may be, for example, a trimethylene, hexamethylene, heptamethylene, octamethylene, nonamethylene, decamethylene, undecamethylene, dodecamethylene, tetradecamethylene or hexadecamethylene radical optionally interrupted with oxygen or sulfur. Suitable alkyl substituents on a straight chain alkylene radical Z are, for example, methyl, ethyl and n-propyl radicals, and a suitable value for Z in which two pairs of such alkyl radicals are joined together is, for example, the methylenebis(4-cyclohexyl) diradical. 
     Preferred values for Z are the hexamethylene, dodecamethylene, and bis-(2-ethoxy) ethane diradical. 
     The acid-addition salts of the invention may be derived from an inorganic or organic acid. In most circumstances it is preferred that the salts be derived from an acid which affords an anion which is suitable for human usage, for example, a pharmaceutically acceptable anion. Examples of such acids are hydrochloric, hydrobromic, phosphoric, sulphuric, acetic, D-gluconic, N-methyl-2-pyrrolidone-4-carboxylic, 2-pyrrolidone-5-carboxylic, methanesulphonic, carbonic, lactic and glutamic acids. 
     Particularly preferred compounds of the invention are 1,12-bis[l-(2-pyrrolidonylethyl)biguanido]dodecane; 1,6-bis[I-(2-pyrrolidonylethyl)biguanido]hexane; and 1,2-bis[l-(2-pyrrolidonylethyl)-5-(2-ethoxybiguanido)]ethane; and acid addition salts thereof. 
     The bis-(pyrrolidonyl alkylene) biguanide compounds of the invention may be prepared by a two-step synthesis. The first step comprises condensing sodium dicyanamide with the acid salt of a suitable diaminoalkane. The diamine provides the alkylene bridging group and the diamino group of the biguanide. Typical diamine starting materials include 1,6-diaminohexane, 1,12-diaminododecane and 1,2-bis(aminoethoxy) ethane. The intermediate product is a bis-cyanoguanidoalkane. 
     This condensation reaction generally is carried out in a solution of about 2 moles of the diamine di-hydrochloride and about 5 moles of the sodium dicyanamide. A suitable solvent, such as butanol, preferably is present in an amount of about 6-10 times the weight of solids employed in the reaction. The condensation is effected at reflux temperatues for about 4 hours. For 1,6-diaminohexane, for example, the reflux temperature is about 110° C. During the course of the reaction, a heavy precipitate of the bis-cyanoguanido compound is obtained. Filtration, washing with solvent and drying provides the intermediate in high yields, generally over 90% of theory, and of 95%-99% purity. 
     In the second step, the bis-cyanoguanido alkane intermediate is condensed with two moles of a suitable N-(2-aminoalkylene) pyrrolidone to form the desired bis-pyrrolidonyl-biguanide. This step also is preferably carried out in a solvent at reflux temperatures, for a suitable period of time. 
    
    
     The invention will now be illustrated by reference to the following examples. 
     A. Preparation of Bis-Cyanoguanidoalkane Intermediates 
     EXAMPLE 1 
     1,6-Bis-(Cyanoguanido) Hexane 
     A mixture of 40 g. (0.2 mole) of 1,6-diaminohexane dihydrochloride, 45 g. (0.5 mole) of sodium dicyanamide and 300 ml. of n-butanol solvent was heated at a reflux temperature of 110° C. for about 4 hours. Initially most of the solid dissolved, but soon a heavy precipitate was deposited. The reaction product then was filtered and the residue was suspended in water, stirred vigorously and filtered. The residue then was washed with water, and dried. The residue was 1,6-bis-(cyanoguanido) hexane. The yield was over 90% of theory, and was 95%-99% pure (m.p. 203°-205° C.). 
     EXAMPLE 2 
     1,12-Bis-Cyanoguanidododecane 
     The procedure of Example 1 was followed using 1,12-diaminododecane in place of 1,6-diaminohexane to provide the named intermediate compound, m.p. 245°-250° C. 
     EXAMPLE 3 
     1,2-Bis-(Cyanoguanidoethoxy)ethane 
     44 g. of 1,2-bis(2-aminoethoxy) ethane dihydrochloride (0.2 mole) and 45 g. of sodium dicyanamide (0.5 mole) and 300 ml. of n-butanol solvent were refluxed for about 4 hours. Then substantially all of the solvent was removed in a roto-evaporator, and the residue was dissolved in methanol. 
     Insoluble inorganic material then was separated from the reaction product by filtration, and the filtrate was treated with acetone until the product was precipitated. The yield was over 80% of theory, and of 95% purity, m.p. 160°-165° C. 
     B. Preparation of Bis-[{Pyrrolidonyl-alkylene)Biguanido]Alkane 
     EXAMPLE 4 
     1,6-Bis[1-(2-Pyrrolidonylethyl) biguanido]hexane:2HCl 
     A mixture of 25 g. (0.10 mole) of the 1,6-bis-(cyanoguanido) hexane intermediate of Example 1, 34.5 g. (0.21mole) of N-(2-aminoethyl) pyrrolidone and hydrochloride salt 200 ml. of n-butanol solvent was refluxed at 117° C. for 17 hours. The solvent then was removed by vacuum evaporation, and the residue was recrystallized from acetone. 54 g. (90% yield) of the named product was obtained. 
     EXAMPLE 5 
     1,12-Bis[1-(2-Pyrrolidonylethyl) biguanido]dodecane:2HCl 
     The procedure of Example 4 .was followed using the intermediate of Example 2 to provide the named compound in similar yield and purity. 
     EXAMPLE 6 
     1,2-Bis[1-(2-pyrrolidonylethyl)-5-(2-Ethoxybiguanido)]ethane:2HCl 
     A mixture of 28.2 g. (0.1 mole) of the 1,2-bis-(cyanoguanidoethoxy) ethane intermediate of Example 3, 36.2 g. (0.22 mole) of N-(2-aminoethyl)pyrrolidone hydrochloride salt and 200 g. of n-butanol was heated at a reflux temperature of 115° C. overnight. The solvent then was removed on a rotary evaporator. An equal volume of methanol was added to the residue and heated for dissolution. A precipitate was obtained from 10 times the volume of acetone. The solid product was dried at 1 mm. The yield was 63.5 g. (90%), m.p. 110°-125° C. 
     Properties of Compounds of Invention 
     EXAMPLE 7 
     Solubility in Water 
     The results in Table I below illustrates the water solubility of the free base and hydrochloride salts of the invention versus chlorhexidine. The solubility in water of the compounds of the invention is substantially greater than chlorhexidine. 
     
                       TABLE 1______________________________________         Form of Compound           Free Base HCl SaltCompound        (pH 8.5)  (pH 5.5)______________________________________Ex. 4           5%        50%Ex. 5           2%        50%Ex. 6           50%       50%Chlorhexidine   0.008%    1.8%______________________________________ 
    
     EXAMPLE 8 
     Antibacterial Activity 
     The minimum inhibitory concentrations (MIC) against different Gram positive and Gram negative microorganisms, and fungi, were determined and the results are shown in Table 2 below. 
     
                       TABLE 2______________________________________Minimum Inhibitory Concentration (ppm)  Gram Negative            Gram Positive  Microorg. Microorg.Compound E. Coli Ps. aer.                    Strept. py.                            Staph. aur.                                    Fungi______________________________________Ex. 4    250      250    ≦50                            ≦100                                     100Ex. 5    250     &gt;500    ≦50                            ≦50                                    ≦50Ex. 6    100     ≦100                    ≦50                            &gt;500    ≦50Chlorhexidine     5        50    5       2.5      &gt;200gluconate______________________________________ The results show that the compounds of the invention have effective antimicrobial and fungistat activity.