Macrolide synthesis process, in specific, gamitromycin

Abstract

 

Description

This application claims the benefit of U.S. Provisional Patent Application No. 61 / 108,046 filed October 24, 2008, which is incorporated herein by reference in its entirety. The documents cited or referred to herein (documents cited herein) and all documents cited or referred to in the documents cited herein, together with any manufacturer's instructions, descriptions, product specifications, and product sheets for any products mentioned herein or in any document incorporated herein, are hereby incorporated herein by reference and may be employed in the practice of the invention. Field of the Invention The present invention relates to a process for synthesizing a group of chemical compounds exhibiting antibacterial activity, which are useful in the therapy of bacterial infections in mammals. More specifically, the invention relates to processes for synthesizing the compounds. Petition 870260057411, dated 12 / 06 / 2026, page 15 / 152 2 / 61 macrolide, for example, gamithromycin. More specifically, the invention relates to a process for producing gamithromycin using a novel configuration of catalysts, chemical structures and / or processes. The present invention also provides a novel process for inhibiting degradation while isolating a structure from a pharmaceutical composition. Background of the Invention Macrolides are a group of chemical compounds, some of which exhibit antibacterial activity and are useful in the therapy of bacterial infections in mammals. Macrolide antibiotics include those possessing a multi-membered lactone ring to which one or more deoxy sugar molecules are attached. These antibiotics are generally bacteriostatic, but have also shown bactericidal activity against some organisms. Macrolide antibiotics are effective against Gram-positive cocci and bacilli, although some of them have some activity against some Gram-negative organisms. Macrolide antibiotics exert their bacteriostatic activity by inhibiting bacterial protein synthesis (Goodman & Gillman's The Pharmacological Basis of Therapeutics, 9th Ed., J.G. Hadman & L.E. Limbird, Eds., chapter 47, pp. 1135). 3 / 61 1140, McGraw-Hill, New York (1996)). As a class, macrolides tend to be colorless and generally crystalline. The compounds are generally stable in near-neutral solution, but may be less stable in acidic or basic solutions. The precursors of the macrolide compounds useful in the invention process (for example, (9E)-9-deoxy-9-hydroxyiminoerythromycin A (hereinafter “Structure 1”); 9-(Z)-erythromycin oxime (hereinafter “Structure 2”); and 9-Deoxo-12-deoxy-9,12-epoxy8a,9-didehydro-8a-aza-8a homoerythromycin A (hereinafter “Structure 3”) were described in U.S. Patents Nos. 5,202,434 and 5,985,844. Additionally, Yang et al., Tetrahedron Letters, 1994, 35(19), 3025-3028 and Djokic et al., J. Chem. Soc. Perkin Trans. 1, 1986, 1881-1890 described the synthesis of the compounds Macrolides employ these compounds as intermediates. However, the synthesis and isolation of macrolide compounds, such as gamithromycin, typically require multiple extractions and phase separations. Therefore, there is still a need to simplify the synthesis and isolation of macrolides, as well as to increase the stability of macrolides and their intermediates. The citation or identification of any document in this application does not constitute an admission that such document is... Petition 870260057411, dated 12 / 06 / 2026, p. 17 / 152 4 / 61 available as prior art in connection with the present invention. Summary of the Invention The present invention relates to a novel process for synthesizing macrolide compounds. One embodiment of the present invention may include the fact that multiple chemical reactions proceed without isolating the chemical intermediates. For example, a chemical substance may be reduced and subsequently alkylated without isolating the chemical intermediates. Thus, multiple reactions may occur in a reaction vessel, which may allow a considerable decrease in the cycle time of the process. In an alternative embodiment, one or more intermediates may be isolated before the reaction. In one embodiment, (9E)-9-deoxy-9-hydroxyiminoerythromycin A (hereinafter Structure 1) can be isomerized to form 9-(Z)-erythromycin oxime (hereinafter Structure 2). In some embodiments, a rearrangement can be employed to convert 9-(Z)erythromycin oxime into 9-deoxo-12-deoxy-9,12-epoxy-8a,9-didehydro-8a-aza-8a homoerythromycin A (hereinafter Structure 3). Reduction and alkylation can be used to convert 9-deoxo-12-deoxy-9,12-epoxy-8a,9-didehydro-8aaza-8a homoerythromycin A into gamithromycin. In another Petition 870260057411, dated 12 / 06 / 2026, page 18 / 152 In the 5 / 61 method, the quantity of by-products resulting from distillations and washings can be reduced. Additionally, one embodiment of the invention may include isolating an intermediate under conditions that are controlled to inhibit degradation of the intermediate. These and other modalities are revealed or are obvious and encompassed by the Detailed Description below. It is clear from this disclosure, and specifically from the claims and / or paragraphs, that terms such as "comprises," "comprised," "comprising," and the like may have the meaning assigned to them under U.S. Patent Law; for example, they may mean "includes," "included," "including," and the like; and that terms such as "essentially consisting of" and "essentially consists of" have the same meaning assigned to them under U.S. Patent Law, for example, they allow for elements not explicitly mentioned, but exclude elements that are found in the prior art or that affect a basic or novel feature of the invention. Brief Description of the Drawings The detailed description that follows, provided by way of example but not intended to limit the invention solely to the specific embodiments described, may be better explained. Petition 870260057411, dated 12 / 06 / 2026, page 19 / 152 6 / 61 understood in conjunction with the attached drawings where: Figure 1 illustrates the chemical structures involved in a process for the synthesis of gamithromycin. Figure 2 illustrates the chemical structures of degradants from structure 3 in a process for the synthesis of gamithromycin. Figure 3 illustrates an HPLC trace of an isolated sample of Structure 3. Figure 4 illustrates an HPLC trace of an isolated sample of Structure 7 obtained by hydrogenation under acidic conditions. Figure 5 illustrates an HPLC trace of an isolated sample of Structure 7 obtained by hydrogenation under less acidic conditions. Figure 6 illustrates an HPLC trace of a sample from Structure 8 (Gamithromycin). Figure 7 illustrates an HPLC trace of an isolated gamithromycin sample. Figure 8 illustrates an overlay of an HPLC trace from a conventional synthesis process and an HPLC trace from the process described in this document. Detailed Description For the sake of clarity, the numbering of the macrocyclic lactones and macrocyclic lactams described herein will employ the ring numbering used in the Patent. Petition 870260057411, dated 12 / 06 / 2026, page 20 / 152 7 / 61 North American patent number 5,202,434, which is incorporated herein by reference in its entirety. The erythromycin A lactone ring numbering shown below will be maintained throughout this document for the 5 14-membered ring compounds described. Similarly, the 15-membered lactam numbering described and shown below will be employed for 15-membered ring compounds described herein. Erythromycin A CH3 15-element ring lactam Petition 870260057411, dated 12 / 06 / 2026, p. 21 / 152 8 / 61 Definitions The terms used in this document will have their usual meaning in the art unless otherwise specified. The organic fractions mentioned in the definitions of the formula variables (I) or (II) are – like the term halogen – collective terms for individual listings of individual elements of the group. The suffix CnCm indicates in each case the possible number of carbon atoms in the group. The term alkyl as used herein refers to linear, branched, cyclic, primary, secondary or tertiary saturated hydrocarbons, including those having 1 to 20 atoms. In some embodiments, the alkyl groups will include C1-C12, C1-C10, C1-C8, C1-C6 or C1-C4 alkyl groups. Examples of C1-C10 alkyl groups include, but are not limited to, methyl, ethyl, propyl, 1-methylethyl, butyl, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 2,2-dimethylpropyl, 1-ethylpropyl, hexyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, 3,3-dimethylbutyl, 1-ethylbutyl, 2 Petition 870260057411, dated 12 / 06 / 2026, page 22 / 152 9 / 61 ethylbutyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1-ethyl-1-methylpropyl, 1-ethyl-2-methylpropyl, heptyl, octyl, 2-ethylhexyl, nonyl and decyl and their isomers. Alkyl C1-C4 means, for example, methyl, ethyl, propyl, 1-methylethyl, butyl, 1-methylpropyl, 2-methylpropyl or 1,1-dimethylethyl. The term alkenyl refers to both linear and branched carbon chains that possess at least one carbon-carbon double bond. In some embodiments, alkenyl groups may include C2-C20 alkenyl groups. In other embodiments, alkenyl includes C2-C12, C2-C10, C2-C8, C2-C6, or C2-C4 alkenyl groups. In one embodiment of alkenyl, the number of double bonds is 1-3; in another embodiment of alkenyl, the number of double bonds is one or two. Other ranges of carbon-carbon double bonds and numbers of carbons are also contemplated depending on the location of the alkenyl moiety in the molecule. C2-C10 alkenyl groups may include more than one double bond in the chain.Examples include, but are not limited to, ethenyl, 1-propenyl, 2-propenyl, 1-methyl-ethenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1-methyl-1-propenyl, 2-methyl-1-propenyl, 1-methyl-2-propenyl, 2-methyl-2-propenyl; 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl, 1-methyl-1-butenyl, 2-methyl-1-butenyl, 3-methyl-1-butenyl, 1-methyl-2-butenyl. Petition 870260057411, dated 12 / 06 / 2026, page 23 / 152 10 / 61 2-methyl-2-butenyla, 3-methyl-2-butenyla, 1-methyl-3-butenyla, 2-methyl-3-butenyla, 3-methyl-3-butenyla, 1,1-dimethyl-2-propenyla, 1,2-dimethyl-1-propenyla, 1,2-dimethyl-2-propenyla, 1-ethyl-1-propenyla, 1-ethyl-2-propenyla, 1hexenila, 2-hexenila, 3-hexenila, 4-hexenila, 5-hexenila, 1methyl-1-pentenyla, 2-methyl-1-pentenyla, 3-methyl-1-pentenyla, 4-methyl-1-pentenyla, 1-methyl-2-pentenyla, 2-methyl-2-pentenyla, 3-methyl-2-pentenyla, 4-methyl-2-pentenyla, 1-methyl-3-pentenyla, 2-methyl-3-pentenyla, 3-methyl-3-pentenyla, 4-methyl-3-pentenyla, 1-methyl-4pentenyla, 2-methyl-4-pentenyla, 3-methyl-4-pentenyla, 4-methyl-4-pentenyla, 1,1-dimethyl-2-butenyla, 1,1-dimethyl-3butenyla, 1,2-dimethyl-1-butenyla, 1,2-dimethyl-2-butenyla, 1,2-dimethyl-3-butenyla, 1,3-dimethyl-1-butenyla, 1,3dimethyl-2-butenyla, 1,3-dimethyl-3-butenyla, 2,2-dimethyl-3butenyla, 2,3-dimethyl-1-butenyla, 2,3-dimethyl-2-butenyla, 2,3-dimethyl-3-butenyla, 3,3-dimethyl-1-butenyla, 3,3dimethyl-2-butenyla, 1-ethyl-1-butenyla, 1-ethyl-2-butenyla, 1-ethyl-3-butenyla,2-ethyl-1-butenyl, 2-ethyl-2-butenyl, 2ethyl-3-butenyl, 1,1,2-trimethyl-2-propenyl, 1-ethyl-1methyl-2-propenyl, 1-ethyl-2-methyl-1-propenyl and 1-ethyl-2methyl-2-propenyl. "Alkynyl" refers to linear and branched carbon chains that have at least one triple bond. Petition 870260057411, dated 12 / 06 / 2026, page 24 / 152 11 / 61 carbon-carbon. In one embodiment of the alkynyl group, the number of triple bonds is 1-3; in another embodiment of the alkynyl group, the number of triple bonds is one or two. In some embodiments, the alkynyl groups include C2-C20 alkynyl groups. In other embodiments, the alkynyl groups may include C2-C12, C2-C10, C2-C8, C2-C6, or C2-C4 alkynyl groups. Other ranges of carbon-carbon triple bonds and numbers of carbons are also contemplated depending on the location of the alkenyl moiety in the molecule.For example, the term alkynyl C2C10as used in the present paper refers to an unsaturated hydrocarbon group of linear or branched chain having 2 to 10 carbon atoms and containing at least one triple bond, such as, ethynyl, prop-1-in1-yl, prop-2-1-in-1-butyl, n-butyl n-but-1-in-3-ila, n-but-1-in-4-ila, n-but-2-in-1-ila, n-pent-1-in-1-ila, n-pent-1-in-3-ila, n-pent-1-in-4-ila, n-pent-1-in-5-ila, n-pent-2-in-1-ila, n-pent-2, in-4-ila n-pent-2-in-5-ila, 3methylbut-1-in-3-ila, 3-methylbut-1-in-4-ila, n-hex-1-in-1ila, n-hex-1-in-3-ila, n-hex-1-in-4-ila, n-hex-1-in-5-ila, n-hex-1-ila, n-hex-6-ila, n-hex-2-in-1-ila, n-hex-2-in-4-ila, n-hex-2-in-5-ila, n-hex-2-in-6-ila, n-hex-3-in-1-ila, n-hex3-in-2-ila, 3-methylpent-1-in-1-ila, 3-methylpent-1-ila, 3-methylpent-1-in-4-yl, 3-methylpent-1-in-5-yl, 4methylpent-1-in-1-yl, 4-methylpent-2-in-4-yl or 4. Petition 870260057411, of 12 / 06 / 2026, p. 25 / 152 12 / 61 methylpent-2-in-5-yl and the like. Aryl refers to a monovalent aromatic carbocyclic group of 6 to 14 carbon atoms possessing a single ring or multiple fused rings. In some embodiments, aryl groups include C6-C10 aryl groups. Aryl groups include, but are not limited to, phenyl, biphenyl, naphthyl, tetrahydronaphthyl, phenylcyclopropyl, and indanyl.Os grupos aryl podem ser substituídos ou no substituídos por uma ou mais frações selecionadas de halogênio, ciano, nitro, hidroxi, mercapto, amino, alquila, alkenila, alkynila, cicloalquila, cicloalkenila, haloalquila, haloalkenila, haloalkynila, halocicloalquila, halocicloalkenila, alcóxi, alkeniloxi, alkyniloxi, haloalkoxi, haloalkeniloxi, haloalkynoxi, cicloalkoxi, cicloalkeniloxi, halocicloalkoxi, halocicloalkeniloxi, alkyltio, haloalquiltio, cicloalquiltio, halocicloalquiltio, alkylssulfinila, alkenylssulfinila, alkynil-sulfinila, haloalkylsulfinila, haloalkenylssulfinila, haloalkynilssulfinila, alkylsulfonyl, alkenylsulfonyl, alkynylsulfonyl, haloalkylsulfonyl, haloalkenylsulfonyl, haloalkynylsulfonyl, alkylamino, alkenylamino, alkynylamino, di(alkyl)amino, di(alkenyl)-amino, di(alkynyl)amino or trialkylssilyl. Petition 870260057411, dated 06 / 12 / 2026, page. 26 / 152 13 / 61 The term “aralkyl” refers to an aryl group that is linked to a parent compound via a diradical alkylene bridge, (-CH2-)n, where n is 1-12 and where “aryl” is as defined above. "Heteroaryl" refers to a monovalent aromatic group of 1 to 15 carbon atoms, preferably 1 to 10 carbon atoms, having one or more oxygen, nitrogen, and sulfur heteroatoms within the ring, preferably 1 to 4 heteroatoms or 1 to 3 heteroatoms. Nitrogen and sulfur heteroatoms may optionally be oxidized. Such heteroaryl groups may have a single ring (e.g., pyridyl or furyl) or multiple condensed rings provided that the point of attachment is through an atom of the heteroaryl ring. Preferred heteroaryls include pyridyl, pyridazinyl, pyrimidinyl, pyrazinyl, triazinyl, pyrrolyl, indolyl, quinolinyl, isoquinolinyl, quinazolinyl, quinoxalinyl, furanyl, thiophenyl, furyl, pyrrolyl, imidazolyl, oxazolyl, isoxazolyl, isothiazolyl, pyrazolyl benzofuranyl, and benzothiophenyl. Heteroaryl rings may or may not be substituted by one or more moieties as described for aryl above. In some embodiments, the invention may include pharmaceutically or veterinary-acceptable salts of the compounds. Petition 870260057411, dated 12 / 06 / 2026, p. 27 / 152 14 / 61 shown in Figure 1. Such salts are generally prepared as acid addition salts by combining a macrolide compound with one to three equivalents of a suitable acid in an inert solvent. The salt is recovered by evaporation of the solvent or by filtration if the salt precipitates spontaneously, or by precipitation using a cosolvent or a non-polar cosolvent followed by filtration.Salts may include, but are not limited to, acetate, benzenesulfonate, benzoate, bicarbonate, bisulfate, bitartrate, borate, bromide, calcium, calcium edetate, edentate, cansilate, carbonate, chlorite, clavulanate, citrate, dihydrochloride, edentate, edisilate, estolate, esilate, ethylsuccinate, fumarate, gluceptate, glucoheptonate, gluconate, glutamate, glycolylarsanilate, hexylresorcinate, hydrabamine, hydrobromide, hydrochloride, iodide, isethionate, lactate, lactobionate, laurate, malate, maleate, mandelate, mesylate, methylsulfate, mucate, napsylate, nitrate, oleate, oxalate, pamoate (embonate), palmitate, pantothenate, phosphate / diphosphate, polygalacturonate, salicylate, stearate, subacetate, succinate, tannate, tartrate, theoaclate, tosylate, triethiodode, valerate and / or combinations thereof. In one embodiment, Structure 1 can be isomerized to form Structure 2 as shown in Figure 1. Petition 870260057411, dated 12 / 06 / 2026, page 28 / 152 15 / 61 In some embodiments, isomerization can be carried out in the presence of one or more reagents. Suitable reagents include, but are not limited to, solvents and bases. The solvents suitable for the transformation may be aprotic or protic solvents known in the art. The following list of reagents is illustrative and it will be clear to a person skilled in the art that other known or yet to be discovered bases and solvents in the state of the art should not be excluded. Suitable bases include, but are not limited to, hydroxides including, but not limited to, lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, calcium hydroxide, magnesium hydroxide, tetramethylammonium hydroxide, benzyltrimethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide and the like; alkoxides including, but not limited to, lithium methoxide, lithium ethoxide, lithium n-butoxide, lithium sec-butoxide, sodium methoxide, sodium ethoxide, sodium n-propoxide, sodium isopropoxide, sodium n-butoxide, sodium sec-butoxide, sodium t-butoxide, sodium trimethylsilanoate, potassium methoxide, potassium ethoxide, potassium t-butoxide, potassium trimethylsilanoate, potassium sec-butoxide, cesium t-butoxide, Petition 870260057411, dated 12 / 06 / 2026, page 29 / 152 16 / 61 calcium methoxide, magnesium ethoxide, titanium (IV) ethoxide, titanium (IV) isopropoxide, benzyltrimethylammonium methoxide, and the like; carbonates including, but not limited to, potassium carbonate, cesium carbonate, sodium carbonate and the like; amides including, but not limited to, lithium amide, lithium dimethylamide, lithium diisopropylamide, lithium dicyclohexylamide, lithium bi(trimethylsilyl)amide, potassium sodium bi(trimethylsilyl)amide and similar amines, including but not limited to 1,1,3,3-tetramethylguanidine, 1,8-diazabicyclo[5,4,0]-undec-7-ene, 1,8-bi(dimethylamino)naphthalene) and the like and hydrides including, but not limited to, lithium hydride, sodium hydride, potassium hydride and the like. Suitable solvents include those that are miscible in water as well as those that are not miscible in water. In some embodiments, suitable solvents include, but are not limited to, water, methanol, ethanol, isopropanol, normal-butanol, sec-butanol, t-butanol, diethyl ether, tetrahydrofuran, dimethoxyethane, toluene, dichloromethane, chloroform, dimethylformamide, dimethylacetamide, 1,3-dimethyl-2-imidazolidinone, 1-ethyl-2-pyrrolidinone, 1-methyl-2-pyrrolidinone, hexamethylphosphoramide, nitromethane, acetonitrile, dioxane, Petition 870260057411, dated 12 / 06 / 2026, page 30 / 152 17 / 61 pyridine, dimethyl sulfoxide and similar substances and / or combinations thereof. In one embodiment, Structure 1 can react with the base in the presence of a solvent to form Structure 2. In another embodiment, the base can be lithium hydroxide and the solvent can be ethanol. In certain embodiments, hydrates of the base, such as lithium hydroxide monohydrate, are employed. Structure 1 Structure 2 In some embodiments, optimization of the isomerization process may include the use of a base and solvent combination sufficient to substantially deprotonate the hydroxyimino group (oxime) of Structure 1. In one embodiment, the reaction conditions may be controlled to stabilize the oxime anion for the time period required to complete an isomerization process. In another modality, a state of equilibrium can Petition 870260057411, dated 12 / 06 / 2026, page 31 / 152 Structure 18 / 61 can be created upon the addition of the base to Structure 1. One embodiment may include protonation of the oxime anions to provide the neutral oxime product mixture from which Structure 2 can be isolated by crystallization, by chromatography followed by crystallization, or by crystallization followed by chromatography. The relative amounts of Structure 1 and Structure 2 in the equilibrium mixture can be controlled by several factors. These factors may include, but are not limited to, the strength and quantity of the base reagent, the size and polarizability of the counteranion, the reaction solvent, and / or the reaction temperature. In some embodiments, the isomerization reaction can be carried out at a concentration of about 1% to about 25% by weight of structure 1 / volume of solvent. In other embodiments, the concentration of structure 1 can be about 5% to about 25%, about 5% to about 15%, or about 7% to about 12% by weight of structure 1 / volume of solvent. In a preferred embodiment, the weight of structure 1 / volume of solvent can be about 10%. In some embodiments, the amount of base used may range from about 1 to about 10 molar equivalents based on the starting amount of Structure 1. In other embodiments, the amount of base may range from about 1 to about 3 molar equivalents. Petition 870260057411, dated 12 / 06 / 2026, p. 32 / 152 19 / 61 a preferred embodiment, the process may include the use of a quantity of base having a value of 2 molar equivalents. In some embodiments, the reaction temperature can be monitored. In one embodiment, the reaction conditions can be controlled to maintain a temperature within a range of about -10°C to about 80°C or from about 0°C to about 80°C. The temperature can be maintained in a range of about 10°C to about 70°C in one embodiment. In another embodiment, the reaction temperature can be maintained within a range of about 15°C to about 60°C. Another embodiment may include maintaining the reaction temperature within a range of about 20°C to about 50°C. Yet another embodiment may include maintaining the reaction temperature within a range of about 20°C to about 30°C. Some embodiments may include maintaining a temperature within a range of about 22°C to about 25°C. In some embodiments, the reaction time may vary. For example, the reaction may operate for about half an hour to about 20 days. Another embodiment may include the reaction operating for about 1 hour to about 15 days. In other embodiments, the reaction time may be within the range of about 3 hours to about 5 days. Alternatively, a reaction time may be within... Petition 870260057411, dated 12 / 06 / 2026, p. 33 / 152 20 / 61 a range of about 6 hours to about 24 hours in one modality. Additionally, one modality may include a reaction time of about 10 hours to about 24 hours. In another modality, a reaction time may be within the range of about 20 hours to about 24 hours. The equilibrium in these reactions can be influenced by several factors including, but not limited to, the strength and quantity of the base, the size and polarization of a counteranion, a reaction solvent, and / or the reaction temperature. Any solvent or base known or yet to be discovered in the art can be used. One embodiment of the invention may include isolating Structure 2 by appropriate means. For example, in one embodiment, Structure 2 may be isolated using crystallization. In other embodiments, the isolation of Structure 2 may include employing chromatography followed by crystallization or crystallization followed by chromatography. It will be clear to one skilled in the art that Structure 2 or any other compound of the invention may be crystallized from solution by any process that appropriately reduces the solubility of the compound in the solvent. Crystallization processes may include, but are not limited to, reducing the temperature of a solution, adding an antisolvent in which the compound is not soluble, forming Petition 870260057411, dated 12 / 06 / 2026, page 34 / 152 21 / 61 of an insoluble salt and similar substances. The process uses a rearrangement to form a mixture of Structure 3 and Structure 5 of an oxime of Structure 1 or Structure 2. Structure 3 Structure 4 Beckmann rearrangements of ketoximes (see, for example, Comprehensive Organic Chemistry, 1.0. Sutherland (Ed.), Pergamon Press, New York, 1979, Vol. 2, pp. 398-400 and 967-968; and Gawley, Organic Reactions, 1988, 35, 1-420) can lead to carboxamides and, in cyclic systems, to ring-expanded lactams. In one embodiment, an acid-catalyzed rearrangement, such as a Beckmann rearrangement, can be used to form a mixture of Structure 2. For example, in certain embodiments of the invention, a mixture resulting from a Beckmann rearrangement of Structure 2 may include, but is not limited to Petition 870260057411, dated 12 / 06 / 2026, page 35 / 152 22 / 61 a 9-deoxo-12-deoxy-9,12-epoxy-8a,9-dideshydro-8a-aza-8a homoerythromycin A (hereinafter Structure 3”) and / or 9-deoxo-6-deoxy-6,9-epoxy-8a,9-dideshydro-8a-aza-8a homoerythromycin A (hereinafter Structure 4”). Although not wishing to be tied to any particular theory, in one embodiment, the mechanism of a Beckmann rearrangement may involve an initial conversion of the oxime hydroxyl group into a leaving group which is then lost with concomitant migration of the oxime carbon substituent that is situated opposite to the leaving group. In aqueous medium, a nitrile intermediate cation thus formed generally reacts with water to give the amide product. The nitrile intermediate may be trapped by other appropriate nucleophiles thereby leading to imino products such as imidates and amidines. Beckmann rearrangement can be performed by varying the conditions, including but not limited to acidic, basic, and neutral conditions. One embodiment may include controlling the reaction conditions and / or reagents in order to provide varying proportions of products. Common acidic reagents that can be used include, but are not limited to, sulfuric acid, including concentrated sulfuric acid, polyphosphoric acid, thionyl chloride, phosphorus pentachloride, sulfur dioxide, and formic acid. Petition 870260057411, dated 12 / 06 / 2026, page 36 / 152 23 / 61 and / or combinations thereof. In some embodiments, a Beckmann rearrangement may occur by heating the oxime with silica gel in a suitable solvent. Suitable solvents include, but are not limited to, aromatic solvents such as toluene or xylene. An alternative embodiment of a Beckmann rearrangement may include heating the oxime under moderately mild conditions in a suitable solvent including hexamethylphosphoramide. In one embodiment, a Beckmann rearrangement may include initial O-sulfonylation of the oxime group with an appropriate sulfonylating agent. Sulfonylating agents are well known in the art and include, but are not limited to, an alkylsulfonyl halide, arylsulfonyl halide, or arylsulfonic anhydride. An intermediate sulfonate oxime formed in this manner may be isolated or may be converted in situ to rearranged products. The sulfonylation and rearrangement reactions may be carried out in the presence of an organic or inorganic base. Some embodiments may include sulfonylation reagents to effect the rearrangement of Structure 2 including, but not limited to, methanesulfonyl chloride, benzenesulfonyl chloride, 4-acetamidobenzenesulfonyl chloride, p-chloride Petition 870260057411, dated 12 / 06 / 2026, page 37 / 152 24 / 61 toluenesulfonyl, benzenesulfonic anhydride, ptoluenesulfonic anhydride and / or other sulfonylation reagents known or yet to be discovered in the art. The reaction can be carried out in the presence of an inorganic base including, but not limited to, sodium bicarbonate or potassium carbonate. Alternatively, in some embodiments the reaction can occur in the presence of an organic base including, but not limited to, pyridine, 4-dimethylaminopyridine, triethylamine, N,N-diisopropylethylamine, and / or any organic base known or yet to be discovered in the art. Suitable solvents may include, but are not limited to, aqueous mixtures such as aqueous acetone or aqueous dioxane and organic solvents such as dichloromethane, chloroform, ethyl acetate, diethyl ether, tetrahydrofuran, toluene, acetonitrile, pyridine and the like. In addition, mixtures of organic solvents, especially those containing pyridine, can be used.In one embodiment, the reaction can be carried out using about one to about three molar equivalents of the sulfonylating agent and about one or more molar equivalents of the base at a reaction temperature of about -20°C to about 50°C. In another embodiment, pyridine can be employed as both solvent and base. In one modality, the distribution of products Petition 870260057411, dated 12 / 06 / 2026, p. 38 / 152 25 / 61 resulting from a Beckmann rearrangement of Structure 2 may depend on the specific reaction conditions employed. For example, when the rearrangement is carried out with p-toluenesulfonyl chloride and sodium bicarbonate in aqueous acetone, the main products may include a lactam and Structure 3. In one embodiment, a Beckmann rearrangement of Structure 2 under anhydrous conditions leads to a product mixture comprising the bridged iminoethers in 9,12 and 6,9, Structure 3 and Structure 4. For example, when a reaction is conducted under anhydrous conditions, such as p-toluenesulfonyl chloride in pyridine, the main products may include Structure 3 and Structure 4. The rate of product may be affected by the addition of cosolvents, temperature and / or initial oxime concentration.For example, when the proportion of pyridine as solvent is increased, the increase in reaction temperature and / or decrease in the initial oxime concentration may favor the formation of Structure 3 over Structure 4. In one embodiment, a Beckmann rearrangement of Structure 2 may involve adding a solution of about 2.5 molar equivalents of ptoluenesulfonyl chloride in diethyl ether to a solution of Structure 2 in pyridine at a temperature in a range of Petition 870260057411, dated 12 / 06 / 2026, page 39 / 152 26 / 61 approximately 0°C to approximately 5°C. One embodiment may include oxime osulfonylation and subsequent rearrangement under reaction conditions to form a mixture of Structure 3 and Structure 4. One embodiment of the invention may include purification of the products following a Beckmann rearrangement of Structure 2. For example, chromatographic processes including, but not limited to, silica gel column chromatography or reversed-phase chromatography and high-performance liquid chromatography may be used, among other chromatographic processes. Structure 3 and Structure 4 may be separated by chromatographic processes. In another embodiment, Structure 3 may be purified by crystallization. In yet another embodiment, the product may be purified by a combination of crystallization and chromatography. In some embodiments, the mixture of Structure 3 and Structure 4 can be further reacted without purification or with limited purification. In one embodiment, additional reactions can occur without isolating the individual structures. For example, the mixture of isomers can be reduced without purification. In one embodiment, Structure 3 can be isolated from the mixture using a low-temperature purification procedure. For example, in one embodiment the Petition 870260057411, dated 12 / 06 / 2026, page 40 / 152 27 / 61 Isolation of structure 3 in dichloromethane can be carried out at a temperature between about -20°C and about 15°C. More typically, the isolation can be carried out at a temperature of about -20°C to about 10°C, about 10°C to about 5°C, about -5°C to about 5°C, or preferably about 0°C to about 5°C. In another embodiment, the purification can be conducted at less than about 25°C, less than about 20°C, or less than about 15°C. In some embodiments, the use of a low-temperature purification procedure can inhibit the degradation of Structure 3 into degradation products including, but not limited to, Structure 5 and / or Structure 6, as illustrated in Figure 2. In one embodiment, the degradation of Structure 3 can be inhibited by removing p-toluenesulfonic acid (hereinafter "PTSA") from the dichloromethane phase. Some embodiments may include solvent removal from the combined organic phases under vacuum at a temperature below 35°C.One option may involve removing components, such as dichloromethane, with methyl tert-butyl ether (hereinafter MTBE) by concentrating once or twice in the residue. In one embodiment, Structure 3 can be formed by internal trapping of the intermediate nitrile species by the hydroxyl group at C12. Structure 3 can be isolated Petition 870260057411, dated 12 / 06 / 2026, page 41 / 152 28 / 61 as a mixture of larger and smaller forms that are isomeric around the imino double bond. In one embodiment, the initial mixture of isomers can equilibrate at room temperature, either in solution or in storage as a crude product, to approximately a 1:1 mixture of isomers. In another embodiment, the larger isomer formed first can be isolated from the crystallization mixture from the solution in a suitable solvent, such as a nitromethane solution. In one embodiment, both forms of the isomer (i.e., Structure 3 and Structure 4) can be readily reduced to 9-deoxo-8a-aza-8a-homoerythromycin A (hereinafter “Structure 7”). One embodiment may include washing the reaction mixture. In one embodiment, the washing may be performed with an appropriate organic solvent. Suitable organic solvents that may be employed for washing are well known in the art and include, but are not limited to, hydrocarbon solvents such as heptane, hexane, pentane, and the like. Other organic solvents include ethers, such as MTBE and the like, alkyl esters such as ethyl acetate and the like, aromatic solvents such as toluene or others. Washing with heptane may remove some pyridine from the reaction mixture. In a Petition 870260057411, dated 12 / 06 / 2026, page 42 / 152 In embodiment 29 / 61, the resulting oil can be diluted with a second solvent mixture, such as dichloromethane and water. In an alternative embodiment, the resulting oil can be washed with 1,3-dimethyl-2-imidazolidinone or N,N'-dimethylethyleneurea (hereinafter DMEU). In some embodiments, the pH of the mixture can be adjusted to a value in a range of about 7 to about 12. Additionally, some embodiments may include adjusting the pH to a value in a range of about 9 to about 10. The pH adjustment can be performed using any pH modifier known in the art, including, but not limited to, metal hydroxides, such as aqueous solutions of sodium hydroxide, lithium hydroxide, or potassium hydroxide. Other suitable pH adjusters include carbonate and bicarbonate salts and amines. One embodiment may include phase separation.Additionally, some embodiments may include backwashing the aqueous phase using dichloromethane or another suitable water-immiscible solvent. In one embodiment, pyridine in the residue can be removed during the crystallization of MTBE. One embodiment may include crystallizing the product at room temperature and then cooling it to a temperature within a range of about -20°C to about 15°C or more, typically about... Petition 870260057411, dated 12 / 06 / 2026, p. 43 / 152 30 / 61 from -20°C to about 10°C. In other embodiments, the mixture is cooled from about -10°C to about 10°C, from about -5°C to about 10°C, or from about 0°C to about 5°C. In some embodiments, the resulting material may be stirred at this temperature for a period of time in order to increase the yield. For example, a material may be stirred for an hour or more to increase the yield. In one embodiment, Structure 3 can be isolated after filtration and low-temperature MBTE washing of the resulting yellow cake. Other chemical structures, including but not limited to Structure 4 and degradation products (e.g., Structure 5 and Structure 6 – see Figure 2), may remain dissolved in the main liquids after the rearrangement reaction. In one embodiment, Structure 3 can be stored in a solid form. Storage in a solid form may inhibit degradation. In some embodiments, Structure 7 can be synthesized by reduction of Structure 3 with the appropriate reacting agent. Several reagents that reduce immunoethers, including those of Structures 3 and 4, to the corresponding amines are known in the art (see, for example, “The Chemistry of Amidines and Imidates,” S. Patai (Ed.), John Wiley and Sons, 1975, pp. 460–461 and “Comprehensive Organic Chemistry,” I.O. Sutherland (Ed.), Pergamon Press, Petition 870260057411, dated 12 / 06 / 2026, p. 44 / 152 31 / 61 New York, 1979, Vol. 2, pg. 495). In this regard, U.S. Patent No. 5,985,844 describes that the reduction of cyclic imino ethers is preferably carried out with metal hydride reagents, including sodium borohydride and derivatives. However, it has been found that the reduction of the imino ethers of Structures 3 and 4 with metal hydride reagents, including borohydride reagents, results in boron salts that complicate product isolation and lead to lower yields and purity. Therefore, in one embodiment of the invention, Structure 7 is formed by reducing Structure 3 using hydrogenation under conditions that provide superior quality and yield to the products. The improved hydrogenation reaction of the invention allows conversion in a container of Structure 3 into a macrocycle of Structure 8 in certain embodiments. In one embodiment, Structure 7 can be formed from the resulting mixture after rearrangement. For example, the mixture resulting from the Beckmann rearrangement of Structure 2 can be hydrogenated to form Structure 7 with an appropriate hydrogen pressure. Some embodiments may include the use of a catalyst during hydrogenation. Catalysts may include, but are not limited to, noble metals and their oxidized forms (e.g., platinum oxide), palladium-based catalysts (e.g., Petition 870260057411, dated 12 / 06 / 2026, page 45 / 152 32 / 61 palladium on carbon, palladium hydroxide on carbon), platinum-based catalysts (e.g., platinum on carbon), rhodium-based catalysts (e.g., rhodium on carbon), iridium-based catalysts, ruthenium-based catalysts and / or any catalysts known or yet to be discovered in the art. In some embodiments, the catalysts may be homogeneous or heterogeneous. In one embodiment, conditions can be controlled to enhance the formation of Structure 7. For example, one embodiment might include operation at ambient temperature and at a hydrogen pressure of 5,000 kPa. In one embodiment, the hydrogenation reaction used to form Structure 7 may employ a solvent including, but not limited to, acetic acid, formamide, acetamide, 2-pyrrolidone; polar aprotic solvents including, but not limited to, DMEU, dimethylacetamide (hereinafter “DMA”), diethylacetamide, dimethyl sulfoxide (hereinafter DMSO), dimethylformamide (hereinafter “DMF”), N-methylpyrrolidone (NMP”), dioxane, tetrahydrofuran, esters such as ethyl acetate, nitriles such as acetonitrile and hexamethylphosphorotriamide and / or other solvents known or yet to be discovered in the art. In some forms, hydrogenation reactions Petition 870260057411, dated 12 / 06 / 2026, page 46 / 152 33 / 61 can be carried out at a temperature in a range between about -20°C to about 40°C. In other embodiments, the hydrogenation reaction can be conducted at a temperature of about -20°C to about 30°C or more typically about -20°C to about 20°C. Preferably, the reaction is carried out at a temperature of about -10°C to about 20°C, about -5°C to about 20°C, about -5°C to about 15°C or about 5°C to about 20°C. Controlling the reaction temperature can inhibit the formation of degradation products in some embodiments. In one embodiment, Structure 7 can be synthesized directly from Structure 2. A polar aprotic solvent can be added to the mixture in the presence of a catalyst. For example, DMA can be added to Structure 7 in the presence of a catalyst containing 50% by weight of platinum over carbon. In some embodiments, Structure 2 can be isolated from a mixture before the reaction. One embodiment may involve reacting the mixture including Structure 2 to form Structure 7. In one embodiment, the mixing conditions can be controlled. For example, the mixture can be stirred while maintaining a temperature of about 15°C and a hydrogen pressure of about 5,000 kPa. As shown in Figure 1, gamithromycin (hereinafter “Structure 8 (Gamithromycin)”) can be formed Petition 870260057411, dated 12 / 06 / 2026, page 47 / 152 34 / 61 by reductive amination of Structure 7 in the presence of propanal and a suitable reaction agent. In one embodiment, the reductive amination reaction is carried out in the presence of hydrogen under pressure. In another embodiment, the reductive amination reaction can be carried out in the presence of a hydride reducing agent including, but not limited to, a boron-based hydride reducing agent, such as sodium cyanoborohydride and the like. In another embodiment of the invention, a compound of Structure 8a, where R is hydrogen, alkyl, alkenyl, alkynyl, aryl, heteroaryl or aralkyl. In one embodiment, a compound where R is alkyl C1-C10 can be obtained by employing the appropriate alkylating agent. NMe2 HO, HO' O, » OMe H (Structure 8a) In yet another embodiment of the invention, R is a C1C4 alkyl group. In one embodiment of the invention, the reaction can occur Petition 870260057411, dated 12 / 06 / 2026, page 48 / 152 35 / 61 employing a catalyst. For example, a palladium catalyst or a platinum catalyst can be used. In one embodiment, a complete reaction can occur within a few hours when excess propanal is employed. Thus, when we employ propanal as both the reagent and solvent, we can decrease the reaction time. In one embodiment, the pH can be controlled within a range of about 5.0 to about 5.5 during the reactions. Another embodiment may include controlling the pH of a reaction mixture within a range of about 4.5 to about 5.5. Preferably, the pH is controlled to about 5.0 to about 5.5 before hydrogenation. In another embodiment, the pH adjustments can be made using acetic acid. One embodiment may involve maintaining the temperature of the reaction mixture in a range of about 20°C to about 60°C, about 30°C to about 50°C, or about 40°C to about 50°C. Preferably, the temperature is about 40°C to about 45°C. In one embodiment, Structure 8 (Gamithromycin) can be synthesized from Structure 3 without isolating the intermediate from Structure 7. Since reductive amination can employ a catalyst similar to the catalyst used in the synthesis of Structure 7, these steps can be combined in several embodiments. Thus, one embodiment Petition 870260057411, dated 12 / 06 / 2026, p. 49 / 152 36 / 61 may include the formation of Structure 8 (Gamithromycin) without isolation of the intermediate from Structure 7. In one embodiment, the intermediates of Structure 7 and Structure 8 (Gamithromycin) may be synthesized in a single reaction vessel without isolation. In one embodiment, this may decrease the cycle time. The invention will now be further described by means of the following non-limiting examples. EXAMPLES Gamithromycin was manufactured as highlighted in Figure 1. Initially, the objective was to prepare Structure 7 without isolating the intermediate, Structure 3. This would maintain the same number of isolated intermediates as in the process currently employed. However, the chemical instability of the intermediate Imidate-4 (Structure 3) under varying conditions resulted in degradation. The degradation products included Structure 5 and Structure 6. The various conditions included low pH and some solvent solutions. Attempts were made to isolate Imidate-4 as a stable solid before carrying out the subsequent steps. Example 1 - Formation of Structure 3 A compound of Structure 2 (30 q) was mixed with pyridine (219.4 mL) and cooled to between 2°C and 6°C. A solution of 4-toluenesulfonyl chloride (hereinafter p Petition 870260057411, dated 12 / 06 / 2026, p. 50 / 152 37 / 61 TsCl) (16.5 g) in methyl t-butyl ether (64.4 mL) was added and the resulting solution was stirred for about 4 hours between 2°C and 6°C and then cooled to between 15°C and -10°C. Heptane (282 mL) was pre-cooled to less than -10°C and added to the solution with stirring. After stirring, the phases were separated for at least 40 minutes. The upper phase (heptane phase) was removed, and dichloromethane (403 mL) and water (503 mL) were added to the aqueous phase, maintaining the temperature between 0°C and 5°C. The pH was adjusted to between 9 and 10 with sodium hydroxide solution, and the mixture was stirred for at least 40 minutes between 0°C and 5°C. The aqueous phase was removed and backwashed twice with dichloromethane (60 mL). The combined organic phases were dried with sodium sulfate, and the dried filtrate was concentrated in the residue at a temperature below 35°C under vacuum. Methyl tert-butyl ether (MTBE) and absolute ethanol were added, and the mixture was concentrated in the residue again. The resulting solid was suspended in MTBE and stirred for 4 hours before cooling to between 0°C and 5°C.The suspension was shaken for at least 1 hour before filtration and washed with MTBE (twice with 30 mL) previously cooled to between 0°C and 5°C. The wet solid was dried to provide a pale yellow solid (19.26 g) of Structure 3. Petition 870260057411, dated 12 / 06 / 2026, p. 51 / 152 38 / 61 Example 2 - Formation of Structure 7 A compound of Structure 3 (8 g) in DMA (80 mL) with 5% Pt / C catalyst (4.0 g) was stirred between 15°C and 25°C with a hydrogen pressure of 5,000 kPa. The addition of acetic acid (0.5 mL) was necessary to complete the reaction. Water (80 mL) was added to the suspension, and the suspension was filtered through a cellulose bed. The filter cake was washed with water (80 mL), and dichloromethane (160 mL) was added to the resulting filtrate. The biphasic mixture was stirred for at least 1 hour. The organic phase was removed, and dichloromethane (160 mL) was added to the aqueous phase before adjusting the pH to between 9 and 11 with sodium hydroxide solution. The biphasic mixture was stirred, and the separated organic phase containing Structure 7 was washed with water (160 mL). The organic phase obtained was dried with sodium sulfate and the dried solution was concentrated in the residue at a temperature below 50°C under vacuum to provide an oil of Structure 7 (13.84 g). Example 3 - Formation of Structure 8 (Gamithromycin) To the oily residue of structure 7 (13.84 g) were added propanal (80 mL), 3% Pd / C catalyst (8.0 g) and acetic acid (7.5 mL). The suspension was stirred at a temperature between 40°C and 45°C with a hydrogen pressure of approximately 2,000 kPa for at least 4 hours. Water (80 mL) Petition 870260057411, dated 12 / 06 / 2026, page 52 / 152 39 / 61 was added to the suspension and the suspension was filtered through a cellulose bed. The filter cake was washed with water (80 mL) and MTBE (160 mL) was added to the resulting filtrate and the biphasic mixture was stirred for at least 30 minutes. The organic phase was removed and MTBE (160 mL) was added to the aqueous phase before adjusting the pH to between 9 and 11 with sodium hydroxide solution. The biphasic mixture was stirred and the separated organic phase containing Structure 8 (Gamithromycin) was washed with water (160 mL). The obtained organic phase was dried with sodium sulfate and the dried solution was concentrated in the residue. Acetonitrile was added and the mixture was back-concentrated in the crude residue of Structure 8 (Gamithromycin) (6.9 g). Example 4 - Formation of Structure 8 (Gamithromycin) without isolation of structure 7 A compound of Structure 3 (1 g) in DMA (10 mL) with 5% Pt / C catalyst (0.5 g) was stirred between 15°C and 25°C with a hydrogen pressure of 5,000 kPa. Addition of acetic acid (0.125 mL) was necessary to complete the reaction. Propanal (5 mL) and acetic acid (2.5 mL) were added to the suspension and stirred at a temperature between 40°C and 45°C with a hydrogen pressure of approximately 2,000 kPa for at least 4 hours. Water (10 mL) was added to the suspension and the suspension was filtered through a bed of Petition 870260057411, dated 12 / 06 / 2026, page 53 / 152 40 / 61 cellulose. The filter cake was washed with water (10 mL) and MTBE (20 mL) was added to the resulting filtrate and the biphasic mixture was stirred for at least 30 minutes. The organic phase was removed and MTBE (20 mL) was added to the aqueous phase before adjusting the pH to between 9 and 11 with sodium hydroxide solution. The biphasic mixture was stirred and the separated organic phase containing Structure 8 (Gamithromycin) was washed with water (20 mL). The obtained organic phase was dried with sodium sulfate and the dried solution was concentrated in the residue. Acetonitrile was added and the mixture was back-concentrated in the crude residue of Structure 8 (Gamithromycin) (0.84 g). Structure 3 was synthesized according to the current manufacturing process using a modified elaboration. The process was carried out up to the washing of the reaction mixture with heptane, designed to partially remove pyridine, and the resulting oil was diluted with dichloromethane and water. The pH was then adjusted to between 9 and 10 with aqueous sodium hydroxide solution. The phases were then separated and a backwash of the aqueous phase was performed with dichloromethane. The isolation of Structure 3 in dichloromethane was carried out at a temperature between 0°C and 5°C. Ptoluenesulfonic acid (hereinafter "PTSA"), from the chloride reagent Petition 870260057411, dated 12 / 06 / 2026, page 54 / 152 41 / 61 of p-toluenesulfonyl, remain dissolved in the aqueous phase after phase separations. The solvents from the combined organic phases were removed under vacuum at a temperature below 35°C, and dichloromethane was captured with MTBE by concentrating 1 or 2 times in the residue. The pyridine remaining in the residue was removed during MTBE crystallization. The product was first crystallized at room temperature and then cooled to 0-5°C and stirred at this temperature for 1 hour to increase the yield. Structure 3 was isolated after filtration, and the resulting yellow cake was washed with MBTE at a low temperature. The degradation products, Structure 5 and Structure 6, and almost all of Structure 4 formed in a Beckmann rearrangement remained dissolved in the main liquids. The yield of Structure 2 was approximately 65-70% by weight, with a purity of Structure 3 isolated around 75-85% by area when using HPLC. The main contaminants of Structure 3 were Structure 5 and Structure 6, each at a level of 5% to 10% by area by HPLC. Figure 3 illustrates the HPLC trace of a batch of isolated Structure 3. The peak results for Figure 3 Petition 870260057411, dated 12 / 06 / 2026, page 55 / 152 42 / 61 are shown below in Table 1. Table 1 RT (Retention Time) Designation Area % of Area 1 12.646 23039 0.12 2 14.457 Structure 5 948922 4.82 3 15.479 Structure 3 14663001 74.43 4 17.307 625131 3.17 5 18.629 8420 0.04 6 18.821 9933 0.05 7 19.700 Structure 2 8 20.563 Structure 6 1935293 9.82 9 22.537 52241 0.27 10 23.860 5976 0.03 11 24.470 6748 0.03 12 24,848 120168 0.61 13 25,400 14 25,581 7889 0.04 15 25,990 10197 0.05 16 26,412 9086 0.05 17 27,551 46974 0.24 18 28,296 Impurity 1094959 5.56 Petition 870260057411, dated 12 / 06 / 2026, page 56 / 152 43 / 61 “Excessive shearing” 19 28,995 81267 0.41 20 29,549 23052 0.12 21 32,061 19794 0.10 22 33,457 8897 0.05 Total 19700986 Although Structure 3 was unstable in solution, the solids obtained did not degrade over time, and their purity was maintained for at least 1 month. The synthesis of Structure 7 via hydrogenation was carried out using a platinum oxide catalyst. The reaction mixture was stirred for about 1 day at room temperature under hydrogen at approximately 6.895 kPa ± 20.684 kPa. These conditions were the starting point for the experiments. The resulting isolated Structure 3 was then used as a standard to compare the products of other experiments. Other carbon-supported reagents / catalysts were also tested. Table 2 summarizes some of the results. Table 2 - Hydrogenation of isolated Structure 3 using various reagents / catalysts Solvent Reagent / Pressure Temperature Purity Petition 870260057411, dated 12 / 06 / 2026, page 57 / 152 44 / 61 (Quantity) Catalyst (Quantity) (kPa) Acetic acid (40 vol.) PtO2 (100% by weight) 5,000 room temperature Structure 7 - 64% Structure 6 - 23% Acetic acid (20 vol.) Rh / C at 5% (50% by weight) 5,000 room temperature Structure 7 - 5% Structure 6 - 63% Acetic acid (40 vol.) Pd / C at 5% (50% by weight) 5,000 room temperature — 50°C No Structure 7 formed Acetic acid (20 vol.) Pt / C at 5% (50% by weight) 5,000 room temperature Structure 7 - 49% Structure 6 - 38% Acetic acid (40 vol.) Pt / C at 5% (66% by weight) 5,000 room temperature Structure 7 - 29% Structure 6 - 59% Acetic acid (40 vol.) Pt / C at 5% with 0.5% S (66% at 5,000°C room temperature) Structure 7 - 59% Structure Petition 870260057411, dated 12 / 06 / 2026, page 58 / 152 45 / 61 Structure 6 - 35% Acetic acid (20 vol.) Pt / C at 5% (50% by weight) 5,000 room temperature Structure 7 - 30% Structure 6 - 70% Acetic acid (20 vol.) Pt / C 1.5% (75% by weight) 5,000 room temperature Structure 7 - 45% Structure 6 - 41% Acetic acid (20 vol.) Pd / C 3% (50% by weight) 5,000 room temperature No Structure 7 formed Acetic acid (20 vol.) Pt / C at 5% (50% by weight) 5,000 room temperature Structure 7 - 31% Structure 6 - 52% Acetic acid (20 vol.) Pt / C at 5% (50% by weight) 5,000 room temperature Structure 7 - 39% Structure 6 - 45% Acetic acid (20 vol.) Pt / C at 5% (50% by weight) 5,000 room temperature Structure 7 - 50% Structure 6 - 23% In the experiments conducted, the 5% Pt / C catalyst Petition 870260057411, dated 12 / 06 / 2026, page 59 / 152 46 / 61 provided a desired result under the conditions employed. Figure 4 shows the HPLC trace of Structure 7 obtained from an experiment using 5% Pt / C catalyst. The values ​​of the area under the peak in the HPLC trace are shown in Table 5 below. Table 3 RT (Retention Time) Designation Area % of Area 1 15.500 Structure 3 2 16.302 45449 0.41 3 16.516 43684 0.40 4 17.243 73435 0.67 5 17.575 24360 0.22 6 18.628 129219 1.18 7 19.700 Structure 2 8 19.729 11809 0.11 9 20.414 Structure 6 2536368 23.10 10 21.409 1189347 10.83 11 23.889 47595 0.43 12 24.300 28497 0.26 13 24.508 Structure 7 5505606 50.15 14 25.341 20326 0.19 15 26.023 170383 1.55 Petition 870260057411, dated 12 / 06 / 2026, page 60 / 152 47 / 61 16 26,374 4586 0.04 17 27,475 12623 0.11 18 27,983 11830 0.11 19 29,262 15805 0.14 20 29,952 32113 0.29 21 31,332 35383 0.32 22 32,221 109461 1.00 23 32,733 51617 0.47 24 32,993 433397 3.95 25 34,142 7096 0.06 26 35,351 406681 3.70 27 36,795 10093 0.09 28 43.278 22005 0.20 Sum 10978866 The use of platinum oxide also yielded the desired result. The standard conditions employed to carry out the hydrogenation were: 20 volumes of acetic acid; room temperature; 5,000 kPa of hydrogen; and stirring overnight, which were used in almost all laboratory experiments. Upon examination of the catalysts, platinum appeared to be the ideal noble metal for this reaction. All tests in this initial study provided the Petition 870260057411, dated 12 / 06 / 2026, page 61 / 152 48 / 61 Structure 7 with a considerable amount of Structure 6. Stability data showed that a solution of Structure 3, when stirred with 20 volumes of acetic acid at room temperature, completely degrades into Structure 5 and Structure 6 after a few hours. Since these conditions were employed in the hydrogenation, it is concluded that the degradation of Structure 3 due to acidic conditions competes with the formation of Structure 7. Consequently, the reaction was attempted in DMEU instead of acetic acid. The results were surprising; the reaction was clearer with only a small amount of Structure 6 formed, and the reaction rate was similar to that of reactions performed using acetic acid as a solvent. Other solvents with characteristics similar to those of DMEU, such as DMF and DMA, were then tested. The tests showed that Structure 3 was not altered in a solution of DMEU, DMF, or DMA at a temperature of approximately 5°C for 3-4 hours, and only showed slight degradation at room temperature after 1 day of agitation. Table 4 summarizes the results of the hydrogenations performed using these solvents and the conditions. Table 4 - Hydrogenation of isolated Structure 3 using DMEU, DMF and DMA Petition 870260057411, dated 12 / 06 / 2026, page 62 / 152 49 / 61 Solvent (quantity) Reagent / catalyst (quantity) Pressure (kPa) Temperature Purity DMEU (20 vol.) Pt / C at 5% (50% BY WEIGHT) 5,000 5°C ^ room temperature Structure 7 - 90% Structure 6 - 1.4% DMF (20 vol.) Pt / C at 5% (50% BY WEIGHT) 5,000 5-10°C Structure 7 - 85% Structure 6 - 3.8% DMA (20 vol.) Pt / C at 5% (50% BY WEIGHT) 5,000 5-10°C Structure 7 - 86.5% Structure 6 - 1.6% DMA (10 vol.) Pt / C at 5% (25% BY WEIGHT) 5,000 5-20°C Structure 7 - 87% Structure 6 - 3.5% DMA (10 vol.) Pt / C at 5% (50% BY WEIGHT) 5,000 15-20°C Structure 7 - 87% Structure 6 - 1.4% The hydrogenations were carried out at a temperature between 5°C and 20°C. In some reactions, acetic acid (0.25% Petition 870260057411, dated 12 / 06 / 2026, page 63 / 152) 50 / 61 A 0.5 volume solution was added towards the end of the reaction. The total solvent volume was reduced from 20 volumes to 10 volumes, while a reduction in the amount of platinum catalyst was carried out without significantly affecting the reaction performance. DMA was the solvent chosen. The preparation was as follows: The reaction mixture was passed through a cellulose filter. The reactor was rinsed with water. The rinse water was used to wash the cellulose buffer. Dichloromethane was added to the filtrate and the pH of the mixture was adjusted to between 4.5 and 5.5 with acetic acid, if necessary, before phase separation. Dichloromethane was added to the aqueous phase and the pH was adjusted to between 9 and 11 with aqueous sodium hydroxide solution. The resulting organic phase containing the product was washed with water to remove any remaining DMA and then concentrated to provide a white foam. Figure 5 illustrates the HPLC trace of Structure 7 obtained from another laboratory experiment using 10 volumes of DMA and the platinum catalyst. The values ​​of the area under the peak in the HPLC trace are shown in Table 5 below. Table 5 Petition 870260057411, dated 12 / 06 / 2026, page 64 / 152 51 / 61 RT (Retention Time) RRT (Relative Retention Time) Designation Area % of Area 1 4.482 0.233 60529 0.58 2 6.249 0.324 29113 0.28 3 7.457 0.387 26836 0.26 4 12.721 0.660 6900 0.07 5 15.188 0.789 18851 0.18 6 15.513 0.805 16914 0.16 7 16.442 0.854 Structure 3 10800 0.10 8 17.827 0.926 12612 0.12 9 18.129 0.941 Structure 1: 30191 0.29 10 18.503 0.961 11329 0.11 11 19.262 1.000 Structure 2: 7558 0.07 12 20.725 1.076 8729 0.08 13 21.093 1.095 Structure 6: 142158 1.36 14 21.800 1.132 4515 0.04 15 22.080 1.146 34763 0.33 16 24.460 1.270 7392 0.07 17 25.010 1.298 Structure 7: 9089710 86.99 18 26. 733 1,388 49639 0,48 19 28,061 1,457 16743 0,16 Petition 870260057411, dated 12 / 06 / 2026, page 65 / 152 52 / 61 20 28,565 1,483 14803 0,14 21 28,880 1,499 26345 0,25 22 29,673 1,541 12139 0,12 23 29,883 1,551 1998 0,02 24 30,942 1,606 47982 0,46 25 31,848 1,653 2627 0,03 26 34,104 1,771 88091 0,84 27 35,821 1,860 512336 4,90 28 41,144 2,136 19501 0,19 29 42.567 2.210 3945 0.04 30 42, 929 2.229 62709 0.60 31 46, 935 2.437 71390 0.68 Sum 1044918 An attempt to synthesize Structure 7 was made directly from the Z-oxime. The same preparation procedure as described above was applied, but instead of isolating Structure 3 by adding MTBE, 10 volumes of DMA and 50% by weight of 5% Pt / C catalyst were added. The resulting mixture was stirred at a temperature of about 15°C under a hydrogen pressure of 5,000 kPa. The reaction proceeded as expected, but an oil was obtained with a mixture of Structure 7 with about 40% by area. HPLC in conjunction with Structure 4 accounts for approximately 42% of the area. Petition 870260057411, dated 12 / 06 / 2026, p. 66 / 152 53 / 61 by HPLC. Since Structure 4 was not removed by crystallization and Structure 3 was not isolated, it was carried over through the isolated Structure 7. The presence of Structure 4 in the hydrogenation may have influenced the impurity profile obtained, although it appears inert under hydrogenation conditions. The residual pyridine that was not removed since Structure 3 was not isolated also influenced the quality of the obtained Structure 7. Structure 8 (Gamithromycin) was prepared by performing a reductive amination of Structure 7 in the presence of propanal. This reaction was carried out under catalytic conditions using hydrogen and a palladium catalyst. Several palladium catalysts and a smaller number of platinum catalysts were used in this transformation. The reactions were slow and incomplete with about 10 equivalents of propanal in ethanol. The use of propanal in large excess allowed a complete reaction within a few hours. Propanal acted as both reagent and solvent. Attempts were made using an acetate buffer solution to obtain a pH of 5.0 to 5.5. However, it was subsequently established that the pH of the reaction mixture only needs to be adjusted to between 5.0 and 5.5 with acid. Petition 870260057411, dated 12 / 06 / 2026, page 67 / 152 54 / 61 acetic acid before hydrogenation. Table 6 summarizes some of the results and conditions for the synthesis of Structure 8 (Gamithromycin). Table 6 - Results and conditions of the reductive amination of Structure 7 Solvent (quantity) Reagent / catalyst (quantity) Pressure (kPa) Initial pH Temperature Purity Propanal (10 vol.) Pd / C at 5% (100% by weight) 2,000 4.70 40-45°C Structure 8 (Gamitromycin) - 42% Propanal (10 vol.) Pd / C 3% (100% by weight) 2,000 5.23 40-45°C Structure 8 (Gamitromycin) - 96% Propanal (10 vol.) Pt / C at 5% with 0.5%S (50% by weight) 1,000 5.06 40-45°C Structure 8 (Gamitromycin) - 46% Structure 7 - 12% Petition 870260057411, dated 12 / 06 / 2026, page 68 / 152 55 / 61 Propanal (vol.) (20 Pt / C at 5% (100% by weight) 2,000 40-45°C Structure 8 (Gamitron icin) - 88% Propanal (vol.) (10 Pd / C at 3% (100% by weight) 2,000 5.49 40-45°C Structure 8 (Gamitron icin) - 89% Initial tests indicated that hydrogenation at room temperature exhibited a slow reaction rate. As a result, a temperature range of 49-45°C was employed for most of the reactions. The pH of the reaction mixture dropped to a range of approximately 4.0 to approximately 4.5 during hydrogenation. Structure 8 (Gamithromycin) was obtained after preparation as described above, but using MTBE as the extraction solvent. The yields depended significantly on the quality of the synthesized Structure 7 and the scale of the laboratory experiment. Structure 8 (Gamithromycin) was obtained with a yield of 86% by weight from 8 g of isolated Structure 3. Figure 6 illustrates the HPLC trace of isolated Structure 8 (Gamithromycin). Petition 870260057411, dated 12 / 06 / 2026, page 69 / 152 56 / 61 typical. The area under the peak values ​​in the HPLC trace are shown in Table 7 below. Table 7 RT (Retention Time) RRT (Relative Retention Time) Description Area % of Area 1 8.255 0.242 7309 0.05 2 11.717 0.343 3245 0.02 3 15.434 0.452 2903 0.02 4 18.081 0.529 16167 0.11 5 19.218 0.562 4256 0.03 6 20.235 0.592 11132 0.07 7 21.027 0.615 1696 0.01 8 22.003 0.644 1388 0.01 9 22.797 0.667 1366 0.01 10 23.200 0.679 2027 0.01 11 23.938 0.700 2338 0.02 12 24.327 0.712 23838 0.16 13 24.725 0.723 4942 0.03 14 25.457 0.745 3033 0.02 15 26.469 0.774 20898 0.14 16 26.753 0.783 40372 0.27 Petition 870260057411, dated 12 / 06 / 2026, page 70 / 152 57 / 61 17 27,407 0,802 10260 0,07 18 28,108 0,822 4246 0,03 19 28,420 0,832 1291 0,01 20 29,200 0,854 11826 0,08 21 29,310 0,858 29056 0,19 22 29,847 0,873 15468 0,10 23 30,303 0,887 4789 0,03 24 30,767 0,900 7826 0,05 25 31,215 0,913 10291 0,07 26 31,717 0,928 813 0,01 27 31,931 0,934 18022 0,12 28 32,319 0,946 2588 0,02 29 32,590 0,954 8105 0,05 30 33,093 0,968 70110 0,47 31 33,504 0,980 1750 0,01 32 34,176 1,000 Structure 8 13341092 88,88 33 35,049 1,026 21138 0,14 34 35,614 1,042 13337 0,09 35 36,615 1,071 457 0,00 36 37,041 1,084 57533 0,38 37 38,514 1,127 92101 0,61 38 39,107 1,144 8684 0,06 39 39,687 1,161 63300 0,42 Petition 870260057411, dated 12 / 06 / 2026, page 71 / 152 58 / 61 40 40,935 1,198 400243 2,67 41 41,533 1,215 3963 0,03 42 41,750 1,222 3210 0,02 43 42,100 1,232 807 0,01 44 42,794 1,252 116557 0,78 45 43,002 1,258 242434 1,62 46 43,283 1,266 6321 0,04 47 45,183 1,322 103524 0,69 48 45,904 1,343 150603 1,00 49 46.942 1.374 37328 0.25 50 48.367 1.415 4688 0.03 Sum 15010670 Since the reductive amination was performed using a platinum catalyst, it was possible to test the use of the same platinum catalyst for the synthesis of structure 8 (Gamithromycin) from structure 3 without isolating structure 7. In a laboratory experiment, Structure 7 was synthesized from isolated Structure 3 using 10 volumes of DMA as a solvent and 50% by weight of 5% Pt / C as described above. After the reaction to form Structure 7, which was not isolated, was complete, 5 volumes of propanal were added and the pH was adjusted to approximately 5.4. Petition 870260057411, dated 12 / 06 / 2026, page 72 / 152 59 / 61 acetic acid and the hydrogenation was carried out as previously described, under the conditions described below. Structure 7 was converted to Structure 8 (Gamithromycin), residual DMA showed no adverse effect. Both hydrogenation reactions proceeded as expected, with similar conversion rates for reactions starting from isolated intermediates. Following the preparation as described above, Structure 8 (Gamithromycin) was obtained with a yield of 84% by weight from Structure 3. Although the yield was comparable to the laboratory experiment where Structure 7 was isolated, the purity was lower (78% by area when measured using HPLC). Several laboratory batches of Structure 8 (gamithromycin) were crystallized to form isolated gamithromycin (Structure 8), yielding approximately 70-80% by weight and generally exceeding 98% purity by area when measured using HPLC. Figure 7 illustrates the HPLC trace of one of those batches of Structure 8 (gamithromycin). The area under the peak values ​​in the HPLC trace are shown in Table 8 below. Table 8 RT(time) RRT Name Area % of Petition 870260057411, dated 12 / 06 / 2026, page 73 / 152 60 / 61 (Retention time) (relative retention time) Area 1 20.149 0.591 16944 0.14 2 26.620 0.780 6928 0.06 3 27.269 0.799 2124 0.02 4 29.192 0.856 21806 0.18 5 29.723 0.871 19650 0.17 6 34.108 1.000 Structure 8 11629284 98.19 7 35.463 1.040 10530 0.09 8 37.073 1.087 46419 0.39 9 42.781 1.254 89503 0.76 Sum 11843187 In Figure 8, this HPLC trace was superimposed with a trace of Structure 8 (Gamithromycin) from conventional production. Comparing the two HPLC profiles, no formation of new impurities was observed. Consequently, this new process can be applied, providing Structure 8 (Gamithromycin) with an impurity profile similar to that of the current manufacturing process. Having thus described in detail the various embodiments of the present invention, it should be understood that the invention defined in the paragraphs above is not limited to the details. Petition 870260057411, dated 12 / 06 / 2026, page 74 / 152 61 / 61 specifics set forth in the description above, since many apparent variations are possible without thereby departing from the spirit or scope of the present invention.

Claims

1. Process for the synthesis of a macrolide compound characterized in that it comprises: (i) treating a compound of Structure 2 with a sulfonylating agent to convert a compound of Structure 2 into a compound of Structure 3; (ii) reducing the compound of Structure 3 in the presence of a polar aprotic solvent and a reducing agent to form a compound of Structure 7, wherein the compound of Structure 3 is reduced with hydrogen in the presence of a platinum or palladium catalyst, wherein the polar aprotic solvent in step ii) is N,N'-dimethylethyleneurea, dimethylformamide, dimethylacetamide, diethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, hexamethylphosphorotriamide or mixtures thereof; Petition 870260057411, dated 12 / 06 / 2026, p.76 / 152 2 / 5 Structure 3 Structure 7 (iii) react the compound of structure 7 with an aldehyde of structure RC(O)H in the presence of a reducing agent to form a compound of structure 8a; Structure 7 Structure 8a where R is an alkyl group comprising C1-C6-alkyl.

2. Process according to claim 1, characterized in that the sulfonylating agent is p-toluenesulfonyl chloride.

3. Process according to claim 1, characterized in that the compound of structure 3 is isolated at a temperature below 10 °C.

4. Process according to claim 1, characterized in that the compound of structure 3 is isolated at a temperature of -20°C to 10°C. Petition 870260057411, dated 12 / 06 / 2026, page 77 / 152 3 / 5 5. Process according to claim 1, characterized in that the reducing agent in step (iii) is hydrogen and the reaction is carried out in the presence of a platinum, rhodium or palladium catalyst.

6. Process according to claim 1, characterized in that the polar aprotic solvent is dimethylformamide or dimethylacetamide.

7. Process according to claim 1, characterized in that the compound of structure 3 in step (ii) is isolated before step (iii).

8. Process according to claim 1, characterized in that steps (ii) and (iii) are conducted without isolating the compound from structure 7.

9. Process according to claim 1 or 8, characterized in that in step (iii) RC(O)H is propanal and the compound of structure 8a is gamithromycin of structure 8: Structure 8 Petition 870260057411, dated 12 / 06 / 2026, page 78 / 152 4 / 5 10. Process according to claim 1 characterized in that it comprises: (i) converting a compound of structure 2 into a compound of structure 3; Structure 2 Structure 3 (ii) reducing the compound of structure 3 in the presence of a polar aprotic solvent and a reducing agent to form a compound of structure 7, wherein the polar aprotic solvent in step ii) is N,N'-dimethylethyleneurea, dimethylformamide, dimethylacetamide, diethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, hexamethylphosphorotriamide or mixtures thereof; (iii) reacting the compound of structure 7 with propanal in the presence of a reducing agent to form a compound of structure 8; where the compound of the structure isolated before step (iii) forms gamithromycin from step (ii) 7 is not NM% Structure 7 Structure 8

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