Patent GB-753742-A (GB)
Title: Erythromycin acid esters
IPC: C07H17/08
Filed: 1954-03-08
Abstract: An erythromycin acid ester of a dicarboxylic acid capable of forming an inner anhydride is produced by reacting erythromycin with a dicarboxylic acid inner anhydride, preferably in an inert solvent at a temperature of 0 DEG  to 60 DEG  C.  The dicarboxylic acid inner anhydride preferably has the formula <FORM:0753742/IV(a)/1> in which R is -CH2.CH2-, -CH2.CH2.CH2-, -CH2.CH2.CH2.CH2, -CH=CH-, -CH2-O-CH2-, -CH2-S-CH2- or -CH2NH.CH2-wherein hydrogen can be replaced by alkyl, alkenyl, alkylidene, alkoxy, cycloalkyl, cycloalkenyl, aryl, aralkyl or halo groups and wherein vicinal carbon atoms can be linked together by a polyvalent radical forming therewith a cyclic structure which can be mono- or polycyclic, carbocyclic or heterocyclic, or mixed carbocyclic and heterocyclic. The preferred inert solvent is methylene chloride; others specified are chloroform, ethylene dichloride, carbon tetrachloride, isopropyl ether and dioxan.  The inner anhydride may be used in up to 25 per cent excess of the erythromycin which is otherwise used in molecular equivalent.  The acid esters may be used as intermediates in the purification of erythromycin.  They form salts with (a) the alkali metal hydroxides such as sodium, potassium and ammonium hydroxide; (b) amines having a pKa greater than erythromicin, e.g. mono-, di-, and trimethylamines, mono-, di- and tri-ethylamines, mono-, di and tri-isopropylamines, ethyl dimethylamine, benzyldiethylamine, and other aliphatic amines up to and including eight carbon atoms; heterocyclic amines such as piperidine, morpholine, pyrrolidine, piperazine, and lower alkyl derivatives thereof.  Examples describe the preparation of (a) erythromycin acid succinate; (b) erythromycin acid phthalate; (c) erythromycin acid maleate; (d) erythromycin acid D 4-cis-tetrahydrophthalate; (e) erythromycin acid hexahydrophthalate; (f) erythromycin acid octenylsuccinate; (g) erythromycin acid diglycolate; (h) erythromycin acid naphthalate; (i) erythromycin acid camphorate; (j) erythromycin acid glutarate; (k) erythromycin beta-methyl glutarate; and (l) the formation of the acid esters in the purification of erythromycin. Lists are given of other acid esters of erythromycin.  They are used in pharmaceutical preparations (see Group VI).  Specification 708,159 is referred to.ALSO:A erythromycin acid ester of a dicarboxylic acid capable of forming an inner anhydride, produced by reacting erythromycin with a dicarboxylic inner anhydride (see Group IV(b)), and which is more palatable than erythromycin per se is incorporated in pharmaceutical preparations for topical, parenteral and oral administration.  The dicarboxylic acid inner anhydride preferably has the formula <FORM:0753742/VI/1> wherein R is -CH2 CH2-, -CH2 CH2 CH2-, -CH2 CH2 CH2 CH2-, -CH = CH-, -CH2 O CH2-, -CH2 S CH2-, or CH2 NH CH2 CH2-and a hydrogen can be replaced by alkyl, alkenyl, alkylidene, alkoxy, cycloalkyl, cycloalkenyl, aryl, aralkyl or halor groups, and wherein vicinal carbon atoms can be linked together by a polyvalent radical forming therewith a cyclic structure which can be mono- or polycyclic, carbocyclic or heterocyclic or mixed carbocyclic and heterocylic.  Examples are (a) erythromycin acid succinate, (b) erythromycin acid phthalate, (c) erythromycin acid maleate, (d) erythromycin acid D 4 cis tetrahydrophthalate (e) erythromycin acid hexahydropthalate, (f) erythromycin acid octenylsuccinate, (g) erythromycin acid diglycollate, (h) erythromycin acid naphthalate, (i) erythromycin acid camphorate, (j) erythromycin acid glutarate and (k) erythromycin beta methyl glutarate.  Specification 708,159, [Group IV(b)] is referred to.