CA2471102C - Crystal form ii of clarithromycin - Google Patents

Abstract

The present invention concerns 6-O-methylerythromycin A Form I or Form II containing one or more impurities, Such 6-O-methylerythromycin A Form I or Form II is useful in the treatment of bacterial infections.

Description

CRYSTAL FORM II OF CLARITHROMYCIN
Technical Field 'fh~is invention relates to a compound having therapeutic utility. More particularly, the present invention concerns 6-O-methyleryklltomycin A, Form I or Fozztt II
containing one or more impurities, pharmaceutical compositions containing same and uses of samc as a therapeutic agent.
Bound of the Invention 6-O-methylerythromycin A (Clarithromycin) is a semisyttthetic macrolide antibiotic of formula W
....o Ho- ~ o CH
p 6-O-methyl erythromycin A
2o which exhibits excellent antibacterial activity against gram-positive bacteria, some gram-ztegative bacteria, anaerobic bacteria, Mycoplasma, and Chlamidia. It is stable under acidic conditions and is efficacious when administered orally. Clarithromycin xs a useful therapy for iztfections of the upper respiratory tract in children and adults.
Brief Description of the Drawines 2s FIGS. 1a, 1b and lc show, respectively, the powder ~ ray diffraction spectrum, the infrared spectrum, and the differtntial scanning calorimetric (DSC) thermogram of 6-O-methylerythromycin A Form I.

-2-FIGS. 2a, 2b and 2c shorn, respectively, the powder X ray diffraction spectrum, the infrared spectrum and the differential scanning calorimetric (DSC) thermogram of 6-O-methylerythromycin A Form II.
Summary of the Invention We have discovered that 6-O-methylerythromycin A can exist in at least two distinct crystalline forms, which for the sake of identification are designated "Form I" and "Form II".
The crystal fortes are identified by their infrared spectrum, differential scanning calorimetric thermogram and powder x ray diffraction pattern. Form I and Form II crystals have an identical spectrum of antibacterial activity, but Form I cxystals unexpectedly have an intrinsic rate of 1 o dissolution about three times that of Form II crystals. Investigations in our laboratory have revealed that 6-O-methylerythromycin A when recrystallized from ethanol, tetrahydrofuran, isopropyl acetate, at~d isopropanol, or mixtures of ethanol, te~ahydrofuran, isopropyl acetate, or isopropanol with other common organic solvents results in exclusive formation of Form I
crystals, not identified hitherto.
15 Drugs currently on the market are formulated from the thermodynamically more stable Form II crystals. Therefore, preparation of the current commercial entity requires converting the Form I crystals to Form II. Typically this is done by heating the Form I
crystals under vacuum at temperature of 8reater than 80°C, Therefore, the discovery of a novel forth of G-O-methylerythromycin A which can be prepared without the high temperature treatment results in.
2o substantial processing cost savings. In addition, the favorable dissolution charactezi.stics of Form I relative to Form II increases bioavailability of the antibiotic and provides significant formulation advantages.
The present invention in one embodiment provides 6-O-methylezythromycin A Form r or Form II containing one or more impurities. In a preferred ezxibodiment, the impurities are 25 selected from alkylated 6-O-methylerythromycin A compounds. In a more preferred embodiment of the invention, the aforementioned alkylated 6-O-methylerythroznycin A
compounds are each alkylated at one or more of the 11, 12, 2', 3' and 4"
positions, In a most preferred embodiment of the invention, the 6-O-methylerythrvmycin A
Form I
or Form IZ contains one or more of 6,11-di-D-methylerythromycin A, 6,12-di-O-methylerythromycin A, and 6,4"-di-D-methylerythromycin A.
Also provided in accordance with the present invention are antibiotic pharmaceutical compositions comprising the products of the present invention together with a phatxxtaceutically acceptable carrier, as well as the use of such products as antibiotics yr in the manufacture of antibiotic medicaments.
Detailed Descriation 6-O-methylezythromycin A, is prepared by metbylation of the 6-hydroxy gtotxp of 1o erythromycin A. However, in addition to the 6 position, erythromycin A
contains hydroxy groups at the 11, 12, 2' and 4" positions, and a ztitrogen at 3' position, all of ~cx~hich are potentially reactive with alkyIating agents. Wherefore, it is necessary to protect the various reactive ~unctionalities prior to alkylation of the 6-hydroxy group. Representative 6-O-methylerythromycin A preparations are described in U.S. Pat. Nos. 4,331,803, 4,670,549, is 4,672,109 and 4,990,602 and European Patent Specification 260 938 B 1.
Following Final removal of the protecting groups, the 6-O-methylerythromycin A
may exist as a solid, a Semisolid, or a sytvp containing residual solvents from the deprotection reactions, inorganic salts, and other impurities. 6-O methylerythromycin A
Form I may be crystallized directly from the syrup or semisolid using the solvents described above.
20 Alternatively, if the crude reaction product solidiFes, the solid may be recrystallized $om any of the solvents described above. Pure 6-O-methylerythromyein A Form I may also be obtained by recrystallizing Form II or mixtures of Form I and Form II from any of the solvent systems described above. The term "6-O-methylerythromycin A" as used herein is meant to include 6-O-methylerythromycin A Form I ox II in any state of purity, or mixtures thereof.
25 The term "treating" refers to crystallizing or recrystallizing 6-O-methylerykhromycin A as defined above from any of the sol~rents described above.

The term "hydrocarbon" as used herein refers to straight chain or branched alkanes having the formula CnTTa"+Z. hydrocarbons useful in the solvent mixtures of th,e present invention include hexane, heptane, octane and the like.
The term "alkyl" refers to a monovalent group derived from a straight ox branched chain saturated hydrocarbon by the removal of a single hydrogen atom. Alkyl groups axe exemplified by methyl, ethyl, n- and iso-propyl, n-, sec-, iso- and tent-butyl, and the like.
The term "ketone" refers to a solvent of formula RC(O)R' where R and R' are straight or branched alkyl. Ketones useful in the solvent mixtures of the present invention include acetone, methyl ethyl ketone, 2- , attd 3 pentanone, and the like.
to The term "carboxylic ester" means a solvent of formula RCOzR' where R and R' are straight or branched alkyl. Carboxylic esters useful in the solvent mixtures of the present invention include methyl acetate, ethyl acetate, isobutyl acetate, and the like.
The term "ether" meats a solvent of formula ROR' where R and R' are straight or branched alkyl. Ethers useful in the solvent mixtures of the present invention include ethyl ether, i 5 diisopz-opyl ether, methyl tent-butyl ether, and the like.
The term "polar aprotic" refers to solvents which do not contain hydroxy groups but have a relatively high dipole moment. Polar aprotic solvents useful in the solvent mi~etures of the present invention inclrxde acetonitrile, N,N dimethylforrtamide (bMF), dimethyl sulfoxide (DMSO), l,l- dimethoxyethane (DME), hexamethylphosphoric triamide (HMPA), and the like.
2o By "pharmaceutically acceptable salt" it is meant those salts 'twhich are, within the scope of sound medical judgment, suitable for use in contact with the tissues of humans an,d louver animals without undue toxicity, irritation, allergic response and the like, and are commensurate with a reasonable benefitlrisk ratio. Pharmaceutically acceptable salts are well Down in the art.
For exatxxple, S. M Berge, et al. describe phartxaaceutically acceptable salts in detail in .r 25 Pharmaceutical Sciences, 1977, 66: I-I9 . The salts can be prepared in situ during the final isolation and purification of the compouzids of the invention, or separately by reacting the free base function with a suitable organic acid. Representative acid addition salts include acetate, adipate, alginate, ascorbate, aspartate, benzcnesulfonate, benzoate, bisulfate, borate, butyrate, camphorate, camphersulfonate, citrate, cyclopentanepropionate, diglueonate, dodecylsulfate, ethanesulfonate, fumarate, glucoheptonate, gIycerophosphate, hemisulfate, heptonate, hexanoate, hydmbromide, hydrochloride, hydroiodide, 2-hydroxy-ethanesulfonate, lactobionate, lactate, lauxate, Iauryl sulfate, malate, maleate, malonate, methanesulfonate, 2-naphtl~alenesulfonate, nicotinate, nitrate, oleate, oxalate, palxztitate, pamoate, pectirxate, persulfate, 3-phenylpropiortate, phosphate, picrate, pivalate, propionate, stearate, succinate, sulfate, tartrate, thiocyanate, toluenesulfonate, undecanoate, valerate salts, and the like Representative alkali ox alkaline earth metal salts include sodium, lithium, pota$sium, calcium, magnesium, and the like, as well as nontoxic ammonium, quaternary ammonium, and amine rations, including, but not limited to to ammonium, tetramethylammonium, tetraethylammonium, methylamine, dimethylatxtine, trimethylamine, tTiethylamine, ethylamine, and the lif e, 6-O-methylerythmmycin A is prepared from erytb~omycin A by a variety of synthetic routes. In one method, erythromycin A is converted to 2'-O-3'-N
bis(benzyloxycarbonyl)-N
o t 5 ~zo ~ \
2. OBz ,r ~'a,~ s~,".W
demethylerythromycin A (r).
'The 6-hydroxy group is then txie~thylated by reaction with an alkylating agent such as bromomethane or iodometl'tane and a base. Removal of the benzoyl groups by catalytic hydrogenation and reductive methylation of the 3' N gives 6-O-methylerythromycin A. See U.S.
Pat. No. x,331,803.
An alternative synthetic route involves methylatiozt of 6-D-methylerythromycin oxime. 6-O-methylerythromycaz~ A-9-oxim~e is prepared by methods well known xx~ the art such as reaction of erythromycin A with hydroxylaixline hydrochloride in the presence of base, or by reaction with hydroxylamine in the presence of acid as described in US 1'at.
No. 5,274,085.
Reaction of the oxime with RX wherein R is allyl or benzyl axsd X is halogen results in formation of 2'-0,3'-N-diallyl or dibenzylerythromycin A-9-O-allyl or benzyloxime halide. Methylation of this quaternary salt as described above, follo'uved by elimination of the R
gt'oups and deaxirnatxon gives 6-O-nn~ethylerythromycin A. See U.S. Pat. No. 4,670,549.
Methylation of 6-O-methyleryr7~romycin .A. oxime derivatives of foxtnala II, q~ "2 \ ~ ps 2' g I~iW,,. ~~.,~~ a _..v.v0 N0~ ~ O OCHB
O
O O 4.
II
wherein R is alkyl, alkenyl, substituted or tuxsttbstituted benzyl, oxyalkyl, or substituted phenylthioallcyl, RZ is benzoyl, and R3 is methyl or benxoyl, followed by depxotection, 2o deoximation, and reductive methylation when R3 is benzoyl gives 6-O-methylerythmmycin A.
See U.S. Pat. No. 4,672,109.
A particularly used preparation of 6-O-methylerythromycin A involves methylation of the RIO i \ IVY
9 .~,,OH O
...~~0 O

oxime derivative III, wherein R' is alkenyl, substituted or unsubstituted benzyl, or alkoxyalkyl, R2 is substituted silyl, and R3 is R2 ox H. Removal of the protecting groups and deoximation is then accomplished in a single step by treatment with acid to ,give 6-O-rnethylerythromycin A.
See European Patent Specificatioil 260 938 B1 and U.S. Pat. No. 4,990,602.
A preferred route to 6-O-methylerythromycin A is outlined in Scheme 1.
Erythromycin A, prepared by fermentation of Streptomyces erythreus is oximated to give oxime 4 wherein R' is alkoxyalkyl. The group Rl may be introduced by reaction of erythromycin A
with the substituted hydroxylamine R~ONH2, ox by reaction of erythromycin A
with hydroxylan7~izte hydrochloride in the presence of base, or hydroxylainine in the presence of acid, followed by reaction with R1X. The two hydroxy groups are then protected simultaneously, in.
which RZ or R3 are the same, or sequentially in which R2 and R3 are different.
Particularly useful protecting groups are substituted silyl groups such as trimethylsilyl, tert butyldimethylsilyl, tert z s butyldiphenylsilyl and the like. The protecting groups are then removed acid the compound is deoximated to produce 6-O-xxiethyleryrhromycin A. The order of deprotection/deoximatiori xs not critical. When the protecting groups are substituted silyl, deprotection and deo7~iniatiou can be accomplished in a single step by treatment with acid, for example using formic acid or sodium hydrogen sulfite. See U.S, Pat. No. 4,990,602.
zo Scheme 1 a ~' t~r~ R, a OH 2' di 2' 9 -'~ HD Wa HO O
a ~ ~ HGi.., -~~. 6 .....W
HD..,, w.,,~ "..v ., Oximation i.p~~ _ ' !OCH~ HO' ~ O ~.n9 O pi.i ~ pH
O O 11Y .
O ~~
Erychron~yan A
R,O A2 ~ Nr OH ~ 2' v o i"ip,~.. '' Prpt~n I L Meihyletbn n.._ OCHa O

V

_$_ H, O R 2 \ N~ O \ t~l~
OH 2' 9 . .OGH' p z~ '~~ HO O
O NO.
i,, s doprotedion ti0~ ~ O
_ OCH9 O d

3 OH
d QR O O 4~
O
6-0-m~thyl~rylhromyoln A
In accordance with the process aspect of the present invention, G-O-methylerythmmycin A prepared by any of the methods described above is suspended in the desired solvent and lxeated to about the reflux temperature of the solvent. Heating is then continued and the suspension is stirred for an amount of time sufficient to dissolve most of the solid, generally about 10 minutes to 2 hours. The suspension is then filtered hot. If necessary, the filtrate may be heated to at or 1s about the reflux ternperaxure of the solvent to form a clear solution. The filtrate is then. slowly cooled to ambient temperature with optional further cooling itx az~ ice water bath. For purposes of this specification, ambient temperature is from about 20 °C to about 25 °C. Crystalline 6-O-methylerythromycin A is then isolated, preferably by filtration, and the wet solid is converted to 6-O-methylerykhromycln A Form I by dry'tug in a vacuum oven at a temperature of between 2o ambient temperature and about 70 °C, preferably from about 40 to about 50 °C and a pressure of between about 2 inches of mercury and atmospheric pressure to remove any remaining solvent.
In accordance with the aspects of this invention wherein 6-O-methylerythromycin A is recrystallized from solvent mi~ctures, 6-O-methylerythromycin A is suspended in the first solvent and heated to about the reflux temperature of the solvent. Heating is then cozttir~ued and the zs suspension is stirred for an amount of time sufficient to dissolve most of the solid, generally about 10 minutes to 2 hours. The suspension. is then filtered hot. The filtrate may be heated to reflux to form a clear solution if necessary. A second solvent is then added to the hot filtrate and the mixture is cooled slowly to ambient temperature with optional further cooling in an ice bath.
Representative second solvents include, but are not limited to, hexane, heptane, octane, acetone, 3o methyl ethyl ketorie, 2-, and 3-pentanone, methyl acetate, ethyl acetate, isobutyl acetate, ethyl ether, diisopropyl ether, methyl tart-butyl ether, acetonitrile, N,N
dimethylformamide, dimethyl sulfoxide, l,l-dimethoxyethane, hexamethylphosphoric trianlide, benzene, toluezte, and chlorobenzene. Hydrocarbons of from 5 to 12 carbon atoms are preferred second solvents. The most preferred second solvent is heptane. After cooling, 6-O-methylerythromycin A crystal Form I is isolated by filtration and drying as described above. The amount of second solvent added is dependent on the solubility of the drug in the first solvent and the second solvent, and can be readily determined by one of ordinary skill in the art. Typical ratios fall in the range of about 1:10 to about 2:1 parts by volume of second solvent. A preferred ratio of first solvent to second solvent is 1: I parts by volume.
Preferred solvents for the isolation of 6-O-methylerythromycint A Form I are ethanol, to isopropyl acetate, tetrahydrofuran, and isopmpanol, The most preferred solvent for the isolation of 6-O-rrtethylerythromycin A
Form I is ethanol.
Pharmaceutical Compositions The present invention also provides pharmaceutical compositions which comprise 15 methylerythromycin A Forth I forzxtulated together with one or more non-toxic pharmaceutically acceptable carriers. The pharmaceutical compositions may be specially formulated for oral administration in solid or liquid form, for parenteral injection, or for rectal administration.
The pharmaceutical compositions of this invention can be administered to humans and other animals orally, rectally, parenterally, intracisternally, intravaginally, intrapezitoneally, 20 topically (as by powders, ointments, or drops), bucally, or as an oral or nasal spray. The term "parenteral" administration as used herein refers to modes of administration which include intravenous, intramuscular, intraperitoneal, intrastemal, subcutaneous and intraarticular injection and infusion.
Pharmaceutical compositions of this izwention for parenteral injection comprise 2s pharmaceutically acceptable sterile aqueous or nonaclueous solutions, dispersions, suspensions or emulsions as weh as sterile powders for reconstitution into sterile iz~jectable solutions ox dispersions just prior to use, Examples of suitable aqueous and nonaqueous carriers, diluents, solvents or vehicles include water, ethanol, polyols (such as glycerol, propylene glycol, polyethylene glycol, and the like), and suitable mixtures thereof, vegetable oils (such as olive -1~-oil), and injectable organic esters such, as ethyl oleate. Proper fluidity can be maintained, for example, by the use of coating materials such as lecithin, by the maintenance of the required particle size in the case of dispersions, and by the use of surfactants.
These compositions rnay also contain adjuvants such as preservatives, wetting agents, emulsifying agents, anal dispersing agents. Prevention of the action of microorganisms may be ensured by the inclusion of various antibacterial and antifungal agents, for example, paraben, chlorobutanol, phenol sorbic acid, and the like. It may also be desirable to include isotonic agents such as sugars, sodium chloride, and the like. Prolonged absorption of the injectable pharmaceutical form may be brought about by the inclusion of agents which delay absorption i0 such as aluminum monostearate and gelatin.
In some cases, in order to prolong the effect of the drug, it is desirable to slow the absorption of the drug from subcutaneous or intramuscular injection. This may be accomplished by the use of a liquid suspension of crystalline or amorphous material with poor water solubility.
The rate of absorption of the drug then depends upon its rate of dissolution which, in turn, may 1 s depend upon crystal size and crystalline form. Alternatively, delayed absorption of a parenterally administered drug form is accomplished by dissolving or suspending the drug in an oil vehicle.
Injectable depot forms are made by forming microencapsule matrices of the drug in biodegradable polymers such as polylactide-polyglycolide. Depending upon the ratio of drug to polymer and the nature of the particular polymer employed, the rate of drug release can be 2o controlled. Examples of other biodegradable polymers include poly(orthoesters) and poly(anhydrides). bepot ixzjectable formulations are also prepared by entrapping the drug in liposomes or microemulsxons which are compatible with body tissues.
The injectable formulations can be sterilized, for example, by f ltxation through a bacterial retaining filter, or by incozporating sterilizing agents in the form of sterile solid zs compositioxis which can be dissolved or dispersed in sterile water or other sterile injectable medium just prior to use.
Solid dosage forms for oral administration include capsules, tablets, pills, powders, and granules. In such solid dosage forms, the active compound is mixed with at least one inert, pharmaceutically acceptable excipient or carrier such as sodium citrate or dicalcium phosphate and/or (a) fillers or extenders such as starches, lactose, sucrose, glucose, mannitol, and silicic acid, (b) binders such as, for example, carboxymethylcellulose, alginates, gelatin, polyvinylpyrrolidone, sucrose, and acacia, (c) humectants such as glycerol, (d) disintegrating agents such as agar-agar, calcium carbonate, potato or tapioca starch, alginic acid, certain silicates, arid sodium carbonate, (e) solution retarding agents such as paraffin, (f) absorption accelerators such as quaternary ammonium compounds, (g) wetting agents such as, for example, cetyl alcohol and glycerol monostearate, (h) absorbents such as kaolin azxd bentonite clay, and (i) lubricants such as talc, calcium stearate, magnesiuzx~ stearate, solid polyethylene I5 glycols, sodium lauryl sulfate, and mixtures thereof.
In the case of capsules, tablets and pills, the dosage form may also comprise buffering agents.
Solid compositions of a similar type may also be employed as ~llezs in soft and hard-filled gelatin capsules using such excipients as lactose or mills sugar as well as high ntiolecular weight polyethylene glycols and the like.
2o The solid dosage forms of tablets, dragees, capsules, pills, and granules can be prepared with coatings and shells such as enteric coatings and other coatings well known in the pharmaceutical formulating art. They may optionally contain opacifying agents arid can also be of a composition that they release the active ingredients) only, or preferentially, in a certain part of the intestinal tract, optionally, in a delayed manner. Examples of embedding compositions 25 which earl be used include polymeric substances and waxes.

e.:
~ -12-The active compounds can also ba in micro-encapsulated form, if approp~ciate, with one or more of the above-mentioned excipients.
~ .;
Liquid dosage forms for oral administration include pharmaceutically acceptable emulsions, solutioxis, suspensions, syrups and elixirs. In addition to the active compounds, the liquid dosage forms may contain inert diluents commonly used in the art such as, for example, water or other solvents, solubilizing agents and emulsifiers such as ethyl alcohol, isopropyl alcohol, ethyl carbonate, ethyl acetate, ben2yl alcohol, benzyl benzoate, propylene glycol, 1,3-. ,.
butylene glycol, dzmethyl formamide, oils (in particular, cottonseed, groundnut, corn, germ, ;, ~., olive, castor, and sesame oils), glycerol, tetrahydmfurfuryl alcohol, polyethylene glycols and :,',.. 10 fatty acid esters of sorbitan, and mixtures thereof.
Resides inert diluents, the oral compositions can also include adjuvants such as wetting agents, emulsifying and suspending agents, sweetening, flavoring, arid perfuming agents.
Suspensions, in addition tv the active compounds, may contain suspending agents as, for ,:
example, ethoxylated isostearyl alcohols, polyoxyethylene sorbitol and sorbitan esters, :., ;'y.,, 15 microcrystalline cellulose, aluminum metahydroxide, bentonite, agar agar, and tragacantb, and ,' ~i ~ mixtures thereof.
Compositions far rectal or vaginal administration are preferably suppositories which can l'' ' be prepared by mixing the compounds of this invention with suitable non-irritating excipients or carriers such as cocoa butter, polyethylene glycol or a suppository wax which are solid at room ~:a; 20 temperature but liquid at body temperature and therefore melt in the rectum or vaginal cavity and release the active compound.
Compounds of the present invention can also be administered in the form of liposomes.
As is lrnown in the art, liposomes are generally derived from phospholipids or other lipid substances. Liposomes are formed by mono- or multi-lamellar hydrated liquid crystals that are 25 dispersed in an aqueous medium. Any non-toxic, physiologically acceptable and metabolizable lipid capable of forming liposomes can be used. The present compositions in liposome form can ;'~ contain, in addition to a compound of the present invention, stabilizers, preservatives, excipients, ~_., ~~ .
. ,..

'~ s and the like. The preferred lipids are the phospholipids and the phosphatidyl cholines (lecithins), both natural and synthetic.
Methods to fornn liposomes are known in the art. See, fox exanxple, Prescott, Ed., Methods in Cell Bioloav, Volume XIV, Academic Press, New York, N.Y. (197, p.
33 et seq.
Dosage forms for topical administration of a compound of this invention include '. ; powders, sprays, ointments and inhalants, The active compound is mixed under sterile conditions with a pharmaceutically acceptable carrier and any needed preservatives, buffers, or propellants ' which may be required. Opthalmic fomaulations, eye ointments, powders and solutions are also ;vl,; contemplated as being within the scope of this invention.
1 o Actual dosage levels of active ingredients in the pharmaceutical compositions of this invention may be varied so as to obtain an amount of the active compounds) that is effective to achieve the desired therapeutic response for a particular patient, composition, and mode of administration. The selected dosage level will depend upon the activity of the particular compound, the route of administration, the severity of the coxidition being treated, and the condition and prior medical history of the patient being treated. However, it is within the skill of the art to start doses of the compound at levels lower than required to achieve the desired .. . therapeutic effect and to gradually increase the dosage until the desired effect is achieved.
Generally dosage levels of about 1 to about 1000, more preferably of about 5 to about 200 mg of 6-O-methylerythromycin A Form I per kilogram of body weight per day are ', 2o administered to a mammalian patient. If desired, the effective daily dose may be divided into multiple doses for purposes of administration, e.g. two to four separate doses per day.
The following Examples are provided to enable one skilled in the art to practice the invention a»d are merely illustrative of the invention. They should not be read as limiting the scope of the invention as defined in the claims.
,,,, .
E~tample 1 Preparation of 6-O-methyle omycin Form I

i'i . CA 02471102 2004-09-23 ~-i . ~ -14-6-O-metlzylerythromycin A was prepared from erythromycin A by oximation of the ,.. ~, carbonyl, protection of the C-2' axtd C-4" hydroxy groups, methylation of the C-6 hydroxy group, . ; , deoximation and removal of the protecting groups, and recrystallization from ethanol according to the method of U.S. Pat No, 4,990,602. The material obtained from the recrystallization was dried in a vacuum oven (40-45 °C, 4-8 in. Hg) to give 6-O-methylerythromycin A Form I.
6-O-methylerythromycin A Form I is characterized by its infrared spectrum, the differential scanning calorimetric (DSC) thermogram and the powder x-ray difhaction pattern.
'' ~ r ,y The differential scanning calorimetric thetxoogram is obtained by methods known in the art and is illustrated in Figure lc. In Figure lc, an exothermic transition at 132.2 °C can be seen, which is ,. ;', ' 10 believed to be due to a phase transition. An endothermic peak at 223.4 °C, which may be due to "
melting, can also be seen. Another endothermic peak at 283.3 °C
followed by an exothermic peak at 306.9 °C may be due to decomposition. After the DSC scant the color of the sample was i .
:,' ; ' black.
"; The powder x-ray diffraction pattern is obtained by the methods lrnown in the art. Figure 1 a illustrates the powder x-ray difr'raction pattern. The 2-theta angle positions in the powder x-°'.v ray diffraction pattezzt of 6-O-methylerythrotnycin A Form I are 5.16°f0.2, 6.68°t0,2, 10.20°f0.2, 12.28°~0.2, 14.20°~0.2, 15.40°~0.2.
15.72°~0.2, and 16.36°~0.2.
Example Z
Conversion of 6-O-methyIerythromycin Form I Crystals to Form II Crystals 6-O-t~nethylerythromycin A Form I crystals (0.40 g), prepared as in Example 1, were y i placed in a vial and heated in the vacuum oven (4-9 in Hg, 100-110 °C) for 18 hours to give 6-O-ttaethyler)rthromycin A Form n crystals. 6-O-methylerythromycin A Form II
melts at 223.4 °C.
In the differential scattttiztg calorimetric therraogram of 6-D-methylerythromycin A Form II there can be seen an endothermic peak at 283.3 °C which may be due to decomposition. After the DSC
scan the color of the sample was black, The 2-theta angle positions in the powder x-ray '-, ; diffraction pattern of 6-O-methyierythromycin A Form a are 8.52°~0.2, 9.48°~0.2, 10.84°t0.2, 11.48°~0.2, 11.88°t10.2, 12.36°~0.2, 13.72°f10.2, 14.12°~0.2, 15.16°f0.2. 16.48°t0.2, 16.92°f0.2, 17.32°t0.2, 18.08°~0.2, 18.40°t0.2, 19.04°t0.2, 19,88°~0.2, and 20.48°f0.2.
.v.., ~ .

a ' -15-~,, r ;
:;; . Example 3 isolation of 6-O-xnethyler~rthromycin Form I bar Recrvstallization .y i Recrystallization from 'fetrahydrofuran A ;txxixture of 6-O-methyleryyhromycin A (20 g), prepared as described in Example 1, in . ;.
S tetrahydrofuran (100 mL) was warmed to reflex and stirred for 15 minutes.
The hot solution was ~xltered to remove traces of insoluble material and cooled to ambient temperature. No crystallization occurred so 10 g of 6-O-methylerythromyciza A was added to the solution and the suspension was again heated to reflex, hot filtered, and cooled in an ice bath. The resulting solid was collected by filtratiorA and dried in the vacuum oven (40-45 °C, 4-8 in. Hg) to give 6-O-~ o methylerythromycin A Form I ( 16.74 g).
.a :i Recrystallization from Isopropyl Alcohol i A mixture of 6-O-methylerythromycin A (15 g), prepared as described ixi Example 1, and v isopropyl alcohol (100 mL) was warmed to reflex and heated for 20 minutes.
The hot solution was filtered to remove traces of insoluble material. The filtrate was transferred to another flask :.;
15 along with a 50 zn,L isopropanol rinse, and the solution was again heated to reflex. The clear solution was then cooled slowly to ambient temperature and left standing for seven hours. The j;~', resulting solid was collected by filtration and dried in the vacuum oven (40-45 °C, 4-8 in. Hg) to give 6-D-methylerythromycin A Form I (13.3g).
,,, ;
Recrystallixation from Isopropyl Acetate 2o A mixture of 6-O-methylerythroxnycin A (10 g), prepared as described in Example 1, and isopropyl acetate (100 mL) was warmed to 73 °C. The hot solution was filtered to remove traces :.;
..; of insoluble material. The clear solution was then cooled slowly to ambient temperature, The ',.i , resulting solid was collected by filtration and dried ip the vacuum oven (40-45 °C, 4-8 in. Hg) to give 6-O-methylerythromycin A Form I (3.6 g).
""
.:; , 25 RecrystalIization from Isopropyl Acetate-Heptane A nn~ixture of 6-O-methylerythromycin A (10 g), prepared as described in Example 1, and isopropyl acetate (100 mL) was warmed to reflex. A small amount of insoluble material was -;; ,.

, CA 02471102 2004-09-23 removed by filtration and the filtrate was transferred to another vessel. The filter flask was rinsed with isopz'opyl acetate (5 mL) and the filtrate and rinse were combined and heated to reflex. To the resulting clear solution was added heptane (100 mL) and the clear solution was cooled to ambient temperature over 1.5 hours during which time a precipitate forrued.
The solid was collects by filtration and dried overnight in the vacuum oven (45-50 °C, 4-8 in. Hp~ to give 6-O-methylerytbromycizt A Fomn I (7.0 g).
Recrystallization from rsoprapyl Acetate N,N dimethylformamlde ,,, .
;.
A mixture of 6-O-xnethylerythromycin A (12 g), prepared as described i»
Example 1, and isopropyl acetate (100 tnL) was warmed to reflex. A small amount of insoluble material was v to removed by filtration and the filtrate was transferred to another vessel.
The filtrate was heated to ', reflex and N,N dimethylformamide (30 mI,) was added. The clear solution was cooled to ambient temperature over 1.5 hours during which time a precipitate formed. The solid was collected by fiiltration and dried overnight in the vacuum oven (49-50 °C, 4-8 in. Hg) to give 6-O-rnethylerythron7,ycin A Form I (6.4 g).
Recrystallization from Tetrahydrofuran-Hcptane To a clear solution of 6-O-methylerythromycin A (10 g), prepared as described in F,~cample 1, in teh'ahydrofuran (75 mL) was added heptane (150 mL). The resulting cloudy ",; solution was heated to 71.5 °C at which point it turned clear. The mixture was cooled to ambient temperature over 2 hours, a~ad then was cooled in an ice-water bath for 0.5 hours. The resulting 2o solid was filtered and dried in the vacuum oven (45-50 °C, 3-4 in.
Hg) for four days to give 6-O-methylerythromycin A Form I (0.50 g).
Recrystallization from Ethanol-Heptane a v - A mixture of 6-O-methylerythromycin A (10 g), Prepared as described in Example 1, and ethanol (100 mL) was warmed to reflex, A small amount of insoluble material was removed by filtration and the filtrate was transferred to another vessel. The filter flask was rinsed with ethanol (20 mL) and the filtrate and rinse were combined and heated at 78 °C until a clear solution was obtained. To the clear solution was added heptane (100 mL) and the clear solution was cooled slowly to ambient temperature and stirred for four days. The resulting solid was . CA 02471102 2004-09-23 . -17-:.;
collected by filtration and dried in the vacuum oven (45-50 °C, 4-8 in.
Hg) to givc 6-O-methylerythromycin A Form I (4.5 g).
Recrystallnxation from lsopxopanol-Heptane A mixture of 6-O-methylerythromycin A (4.0 g), prepared as described in Example 1, . 5 and isopropataol (50 mL) was warmed to reflux. Heptane (50 mL) was added and the solution was cooled slowly to ant~bient temperature and then was cooled in ~r ice-water bath. T'he resulting solids were collected by filtration and dried in the vacuum oven (4-8 in. Hg) to give 6-O-methylerythromycin A Form I (3.6 g).
Example 4 Dissolution Rates o~6-O-methylerythromycin Forms I and II
Dissolution studies were carried out at 60 rpm in 300 mL of 0.05 M phosphate buffer at 37°C using a constant surface area (13/32" diaxneter) drug compact.
Aliquots were removed :, periodically and assayed directly by HPLC (Scm x 4.6mm 3p. ODS 2 "Little Champ" (Regis) ,, column; 50:50 acetonatrile-0.05 M pH 4.0 phosphate buffer mobile phase; 1.0 mIJmin flow rate).
15 As shown in Table 1, 6-O-methylerythromycin A Foam I has an intrinsic rate of dissolution about three times greater than Form II.
Table 1 ' Intrinsic Dissolution Rates of 6-O-methylerythromycin A forms I and II

Crystal Form Dissolution Rate f S.D.

. (N.g/min/cm2) I 636 t 2.5 v II ~ 203 ~ 14 2o The foregoing examples are presented fot' purposes of illustration and are not intended to limit the scope of the invention. Variations and changes which are obvious to one skilled in the art are intended to be within the scope and nature of the invention as defined in the appended claims.

Claims (20)

2. Isolated, non-transient, unsolvated, non-hydrated 6-O-methylerythromycin A
Form 11 of
1. claim 1, wherein said one or more impurities are selected from alkylated 6-O-methylerythromycin A
   compounds.
   
   5. The patentee disclaims the entirety of claim 3, with the exception of the following:
   
   3. Isolated, non-transient, unsolvated, non-hydrated 6-O-methylerythromycin A
   Form II of
2. claim 2, wherein said alkylated 6-O-methylerythromycin A compounds are each alkylated at one or more of the 11, 12, 2', 3', and 4" positions.
   
   6. The patentee disclaims the entirety of claim 4, with the exception of the following:
   
   4. Isolated, non-transient, unsolvated, non-hydrated 6-O-methylerythromycin A
   Form II
   containing one or more of 6, 11-di-O-methylerythromycin A, 6, 12-di-O-methylerythromycin A, and 6, 4"-di-O-methylerythromycin A.
   
   7. The patentee disclaims the entirety of claim 5, with the exception of the following:
   
   5. Isolated, non-transient, unsolvated, non-hydrate 6-O-methylerythromycin A
   Form II
   containing 6, 11-di-O-methylerythromycin A.
   
   8. The patentee disclaims the entirety of claim 6, with the exception of the following:
   
   6. Isolated, non-transient, unsolvated, non-hydrated 6-O-methylerythromycin A
   Form II
   containing 6, 12-di-O-methylerythromycin A.
   
   9. The patentee disclaims the entirety of claim 7, with the exception of the following:
   
   7. Isolated, non-transient unsolvated, non-hydrated 6-O-methylerythromycin A
   Form II
   containing 6, 4"-di-O-methylerythromycin A.
   
   CLAIMS:
   
   1. 6-O-methylerythromycin A Form H containing one or more impurities.
   
   2. 6-O-methylerythromycin A Form II of claim 1, wherein said one or more impurities are selected from alkylated 6-O-methylerythromycin A compounds.
3. 3. 6-O-methylerythromycin A Form 11 of claim 2, wherein said alkylated 6-O-methylerythromycin A compounds are each alkylated at one or more of the 11, 12, 2', 3', and 4" positions.
4. 4. 6-O-methylerythromycin A Form II containing one or more of 6, 11-di-O-methylerythromycin A, 6, 12-di-O-methylerythromycin A, and 6, 4"-di-O-methylerythromycin A.
5. 5. 6-O-methylerythromycin A Form II containing 6, 11-di-O-methylerythromycin A.
6. 6. 6-O-methylerythromycin A Form II containing 6, 12-di-O-methylerythromycin A.
7. 7. 6-O-methylerythromycin A Form II containing 6, 4"-di-O-methylerythromycin A.
8. 8. An antibiotic pharmaceutical composition comprising the product of claim 1, 2, 3, 4, 5, 6 or 7, together with a pharmaceutically acceptable carrier.
9. 9. The use of the product of claim 1, 2, 3, 4, 5, 6 or 7 as an antibiotic.
10. 10. The use of the product of claim 1, 2, 3, 4, 5, 6 or 7 in the manufacture of an antibiotic medicament.
11. 11. 6-O-methylerythromycin A Form I containing one or more impurities.
12. 12. 6-0-methylerythromycin A Form I of claim 11, wherein said one or more impurities are selected from alkylated 6-O-methylerythromycin A compounds.
13. 13. 6-O-methylerythromycin A Form I of claim 12, wherein said alkylated 6-O-methylerythromycin A compounds arc each alkylated at one or more of the 11, 12, 2', 3', and 4" positions,
14. 14. 6-O-methylerythromycin A Form I containing one or more of 6, 11-di-O-methylerythromycin A, 6, 12-di-O-methylerythromycin A, and 6,4"-U-O-methylerythromycin A.
15. 15. 6-O-methylerythromycin A Form I containing 6, 11-di-O-methylerythromycin A.
16. 16. 6-O-methylerythromycin A Form I containing 6, 12-di-O-methylerythromycin A.
17. 17. 6-O-methylerythromycin A Form I containing 6, 4'"-di-O-methylerythromycin A.
18. 18, An antibiotic pharmaceutical composition comprising the product of claim 11, 12, 13, 14, 15, 16 or 17, together with a pharmaceutically acceptable carrier.
19. 19. The use of the product of claim 11, 12, 13, 14, 15, 16 or 17 as an antibiotic.
20. 20. The use of the product of claim 11, 12, 13, 14, 15, 16 or 17 in the manufacture of an antibiotic medicament.