# Patent

## Title
Processes for the preparation of 0-(2-aminobenzo[d]oxazol-5-yl)methyl hydroxylamine for the synthesis of 6,11-bicyclic erythromycin derivative EDP-182

## Abstract

The present invention relates to processes and intermediates for the preparation of 6-11 bicyclic erythromycin derivative known as EDP-182 (IX-a). In particular, the present invention relates to processes and intermediates for the preparation of O-(2-aminobenzo[d]oxazol-5-yl)methyl hydroxylamine:

## Background
RELATED APPLICATION
This application claims the benefit of U.S. Provisional Application No. 60/778,203, filed on Mar. 2, 2006. The entire teachings of the above application are incorporated herein by reference.


TECHNICAL FIELD
The present invention relates to processes and intermediates useful in the preparation of bridged erythromycin derivative known as EDP-182 and their respective pharmaceutically acceptable salts.
BACKGROUND OF THE INVENTION
Macrolide antibiotics play a therapeutically important role, particularly with the emergence of new pathogens. Structural differences are related to the size of the lactone ring and to the number and nature (neutral or basic) of the sugars. Macrolides are classified according to the size of the lactone ring (12, 14, 15 or 16 atoms). The macrolide antibiotic family (14-, 15- and 16-membered ring derivatives) shows a wide range of characteristics (antibacterial spectrum, side-effects and bioavailability). Among the commonly used macrolides are erythromycin, clarithromycin, and azithromycin. Macrolides possessing a 3-oxo moiety in place of the 3-cladinose sugar are known as ketolides and have shown enhanced activity towards gram-negative bacteria and macrolide resistant gram-positive bacteria. The search for macrolide compounds which are active against MLSB-resistant strains (MLSB=Macrolides-Lincosamides-type B Streptogramines) has become a major goal, together with retaining the overall profile of the macrolides in terms of stability, tolerance and pharmacokinetics.
SUMMARY OF THE INVENTION
The present invention provides methods for preparing 6,11-bridged macrocyclic derivative known as EDP-182. Particularly, the present invention provides methods for preparing O-(2-aminobenzo[d]oxazol-5-yl)methyl hydroxylamine as the key intermediate for the preparation of EDP-182.


DETAILED DESCRIPTION OF THE INVENTION
The processes of the present invention are suitable for synthesizing 6-11 bicyclic erythromycin derivative known as EDP-182, or pharmaceutically acceptable salts thereof. In one embodiment, the process comprises the step of reacting a compound of formula (I):




or a pharmaceutically acceptable salt thereof with a compound of formula II:




to produce a compound of formula III:




optionally in the presence of a palladium

catalyst,
wherein,
Each R1 is independently selected from hydrogen, acyl, silane, a substituted or unsubstituted, saturated or unsaturated aliphatic group, a substituted or unsubstituted, saturated or unsaturated alicyclic group, a substituted or unsubstituted aromatic group, a substituted or unsubstituted heteroaromatic group, saturated or unsaturated heterocyclic group;
Q is independently selected from R1, OR1, or OC(O)R1;
Z is selected from R1, OR1, OC(O)R1, OC(O)NR3R4, OS(O)nR1, and




one of J or G is hydrogen and the other is selected from R1, OR1, or NR3R4;
or, J and G, taken together with the carbon atom to which they are attached, are selected from C═O, C═NR1, C═NOR1, C═NO(CH2)mR1, C═NNHR1, C═NNHCOR1, C═NNHCONR3R4, C═NNHS(O)nR1, or C═N—N═CHR1;
Rp is a hydroxyl protecting group;
m is an integer; and
n is 0, 1, or 2.
Preferred embodiments of the compound of Formula I are the compounds of Formulas I-a and I-b:




In a most preferred embodiment, the compound of Formula I is a compound of formula (I-c):




Although compounds of formula I are preferred, other macrocyclic compounds which contain two or more nucleophilic moieties (e.g. —OH, —NH2, —NH—, etc.) may be substituted for the starting material of formula I.
Preferred embodiments of the compound of formula II are compounds wherein R1 is tert-butyl.
Compounds of formula (II) that are useful in the preparation of compounds of formula (III), are prepared by the process comprising the step of reacting a compound of formula (II-a):




with a C1-C6 alkyl anhydride in the presence of a phase transfer catalyst.

A most preferred embodiment of the compound of Formula III is the compound of Formula III-a:




Another embodiment of the present invention, therefore, is a process comprising the step of hydrolyzing a compound of formula (III) with aqueous acid to provide a compound of formula (IV).




A most preferred embodiment of the compound of formula (IV) is a compound of formula (IV-a):




Yet a further embodiment of the present invention, therefore, is a process comprising the step of reducing a compound of formula (IV) with a reducing agent to provide a compound of formula (V):




Preferred embodiments of the compound of formula (V) are compounds of formula (V-a):




Yet another embodiment of the present invention, therefore, is a process comprising the step of acylating a compound of formula (V) with an acylating agent to provide a compound of formula (VI):




Preferred embodiments the compound of formula (VI) are compounds of formula (VI-a):




Yet a further embodiment of the present invention, therefore, is a process comprising the step of oxidatively cleaving a compound of formula (VI) with a cleaving reagent or reagents which are capable of performing oxidative cleavage to provide a compound of formula (VII):




Preferred embodiments of the compound of formula (VII) are compounds of formulas (VII-a):




Yet another embodiment of the present invention, therefore, is a process which comprises the step of oxidizing a compound of formula (VII) with an oxidizing agent or agents to provide a compound of formula (VIII):




The most preferred embodiments of the compound of formula (VIII) are compounds of formula (VIII-a):




Compounds of formula (VIII) are useful as intermediates in the synthesis of compounds of formula (IX):




A most preferred embodiment of the compound of formula (IX) is a compound of formula (IX-a):




Another embodiment of the present invention is a process which comprises the step of reacting a compound of formula (VIII) with 1-(2-aminobenzo[d]oxazol-5-yl)-hydroxylamine to provide a compound of formula (IX-a). In a most preferred embodiment of this process, a compound of formula (VIII-a) is treated with a 1-(2-aminobenzo[d]oxazol-5-yl)-hydroxylamine (X):




to provide a compound of formula (IX-a).

The present invention provides a process for the preparation of compounds of formula (XI);




Wherein R3 and R4 are hydrogen;
or one of R3 or R4 is a hydrogen and the other is selected from:

    
    
        (a) C(O)R5, where R5 is C1-C6 alkyl, optionally substituted with one or more substituents selected from aryl, substituted aryl, heteroaryl, or substituted heteroaryl;
        (b) C(O)OR5, where R5 is as previously defined; or
        wherein A and B are each independently hydrogen, a substituted or unsubstituted aliphatic group, a substituted or unsubstituted cyclic group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alicyclic group, or a substituted or unsubstituted heteroaryl group; or A and B taken together with the carbon to which they are attached form a cyclic moiety selected from: aryl, substituted aryl, heterocyclic, substituted heterocyclic, alicyclic, or substituted alicyclic;
    
    
    alternatively, R3 and R4 are taken together with the nitrogen atom to which they are attached to form N═C(R6)(R7), where R6 and R7 are each independently selected from a substituted or unsubstituted aliphatic group, a substituted or unsubstituted cyclic group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alicyclic group, or a substituted or unsubstituted heteroaryl group

said process comprising:
    
        (1) reducing 4-(hydroxymethyl)-2-nitrophenol with a reducing agent to provide compound of formula (XII):
    
    






    
    
        (2) reacting cyanogenbromide with compound of formula (XII) in a solvent to give compound of formula (XIII):
    
    






    
    
        (3) halogenating the resulting compound with a chlorinating reagent to provide a compound of formula (XIV);
    
    






    
    
        (4) treating compound of formula (XIV) with compounds of formula R3R4NOH wherein R3 and R4 are as previously defined, in the presence of base to yield compounds of formula (XI).
    
    


Yet another embodiment, the process further comprising the step of hydrolyzing the compound of formula XI with a base or an acid in a protogenic organic solvent or aqueous solution, to yield 1-(2-aminobenzo[d]oxazol-5-yl)-hydroxylamine (X):




In another embodiment, the process for the synthesis of a compound of formula (XV):




wherein R3 and R4 are previously defined and the said process comprising:

    
    
        (1) reacting cyanogenbromide with 2-amino-4-methylphenol in a solvent to give compound of formula (XVI):
    
    






    
    
        (2) protecting the compound of formula (XVI) with succinic anhydride to yield compound of formula (VI):
    
    






    
    
        (3) brominating the compound of formula (XVII) with a brominating reagent to give compound of the following formula (XVIII):
    
    






    
    
        (4) treating the compound of formula (XVIII) with a compound of formula R3R4NOH in the presence of base, to provide a compound of formula (XV).
    
    


Yet in another embodiment, the process further comprising the step of deprotecting the compound of formula (XIX) with a base or an acid in a protogenic organic solvent or aqueous solution, to yield 1-(2-aminobenzo[d]oxazol-5-yl)-hydroxylamine (X).
Definitions
Listed below are definitions of various terms used to describe this invention. These definitions apply to the terms as they are used throughout this specification and claims, unless otherwise limited in specific instances, either individually or as part of a larger group.
An “aliphatic group” is non-aromatic moiety that may contain any combination of carbon atoms, hydrogen atoms, halogen atoms, oxygen, nitrogen or other atoms, and optionally contain one or more units of unsaturation, e.g., double and/or triple bonds. An aliphatic group may be straight chained, branched or cyclic and preferably contains between about 1 and about 24 carbon atoms, more typically between about 1 and about 12 carbon atoms. In addition to aliphatic hydrocarbon groups, aliphatic groups include, for example, polyalkoxyalkyls, such as polyalkylene glycols, polyamines, and polyimines, for example. Such aliphatic groups may be further substituted.
Suitable aliphatic or aromatic substituents include, but are not limited to, —F, —Cl, —Br, —I, —OH, protected hydroxy, aliphatic ethers, aromatic ethers, oxo, —NO2, —CN, —C1-C12-alkyl optionally substituted with halogen (such as perhaloalkyls), C2-C12-alkenyl optionally substituted with halogen, —C2-C12-alkynyl optionally substituted with halogen, —NH2, protected amino, —NH—C1-C12-alkyl, —NH—C2-C12-alkenyl, —NH—C2-C12-alkenyl, —NH—C3-C12-cycloalkyl, —NH-aryl, —NH-heteroaryl, —NH-heterocycloalkyl, -dialkylamino, -diarylamino, -diheteroarylamino, —O—C1-C12-alkyl, —O—C2-C12-alkenyl, —O—C2-C12-alkynyl, —O—C3-C12-cycloalkyl, —O—aryl, —O-heteroaryl, —O-heterocycloalkyl, —C(O)—C1-C12-alkyl, —C(O)—C2-C12-alkenyl, —C(O)—C2-C12-alkynyl, —C(O)—C3-C12-cycloalkyl, —C(O)-aryl, —C(O)-heteroaryl, —C(O)-heterocycloalkyl, —CONH2, —CONH—C1-C12-alkyl, —CONH—C2-C12-alkenyl, —CONH—C2-C12-alkynyl, —CONH—C3-C12-cycloalkyl, —CONH-aryl, —CONH-heteroaryl, —CONH-heterocycloalkyl, —CO2—C1-C12-alkyl, —CO2—C2-C12-alkenyl, —CO2—C2-C12-alkynyl, —CO2—C3-C12-cycloalkyl, —CO2-aryl, —CO2-heteroaryl, —CO2-heterocycloalkyl, —OCO2—C1-C12-alkyl, —OCO2—C2-C12-alkenyl, —OCO2—C2-C12-alkynyl, —OCO2—C3-C12-cycloalkyl, —OCO2-aryl, —OCO2-heteroaryl, —OCO2-heterocycloalkyl, —OCONH2, —OCONH—C1-C12-alkyl, —OCONH—C2-C12-alkenyl, —OCONH—C2-C12-alkynyl, —OCONH—C3-C12-cycloalkyl, —OCONH-aryl, —OCONH-heteroaryl, —OCONH-heterocycloalkyl, —NHC(O)—C1-C12-alkyl, —NHC(O)—C2-C12-alkenyl, —NHC(O)—C2-C12-alkynyl, —NHC(O)—C3-C12-cycloalkyl, —NHC(O)-aryl, —NHC(O)-heteroaryl, —NHC(O)-heterocycloalkyl, —NHCO2—C1-C12-alkyl, —NHCO2—C2-C12-alkenyl, —NHCO2—C2-C12-alkynyl, —NHCO2—C3-C12-cycloalkyl, —NHCO2-aryl, —NHCO2-heteroaryl, —NHCO2-heterocycloalkyl, —NHC(O)NH2, NHC(O)NH—C1-C12-alkyl, —NHC(O)NH—C2-C12-alkenyl, —NHC(O)NH—C2-C12-alkynyl, —NHC(O)NH—C3-C12-cycloalkyl, —NHC(O)NH-aryl, —NHC(O)NH-heteroaryl, —NHC(O)NH-heterocycloalkyl, NHC(S)NH2, NHC(S)NH—C1-C12-alkyl, —NHC(S)NH—C2-C12-alkenyl, —NHC(S)NH—C2-C12-alkynyl, —NHC(S)NH—C3-C12-cycloalkyl, —NHC(S)NH-aryl, —NHC(S)NH-heteroaryl, —NHC(S)NH-heterocycloalkyl, —NHC(NH)NH2, NHC(NH)NH—C1-C12-alkyl, —NHC(NH)NH—C2-C12-alkenyl, —NHC(NH)NH—C2-C12-alkynyl, —NHC(NH)NH—C3-C12-cycloalkyl, —NHC(NH)NH-aryl, —NHC(NH)NH-heteroaryl, —NHC(NH)NH-heterocycloalkyl, NHC(NH)—C1-C12-alkyl, —NHC(NH)—C2-C12-alkenyl, —NHC(H)—C2-C12-alkynyl, —NHC(NH)—C3-C12-cycloalkyl, —NHC(NH)-aryl, —NHC(NH)-heteroaryl, —NHC(NH)-heterocycloalkyl, —C(NH)NH—C1-C12-alkyl, —C(NH)NH—C2-C12-alkenyl, —C(NH)NH—C2-C12-alkynyl, —C(NH)NH—C3-C12-cycloalkyl, —C(NH)NH-aryl, —C(NH)NH-heteroaryl, —C(NH)NH-heterocycloalkyl, —S(O)—C1-C12-alkyl, —S(O)—C2-C12-alkenyl, —S(O)—C2-C12-alkynyl, —S(O)—C3-C12-cycloalkyl, —S(O)-aryl, —S(O)-heteroaryl, —S(O)-heterocycloalkyl —SO2NH2, —SO2NH—C1-C12-alkyl, —SO2NH—C2-C12-alkenyl, —SO2NH—C2-C12-alkynyl, —SO2NH—C3-C12-cycloalkyl, —SO2NH-aryl, —SO2NH-heteroaryl, —SO2NH-heterocycloalkyl, —NHSO2—C1-C12-alkyl, —NHSO2—C2-C12-alkenyl, —NHSO2—C2-C12-alkynyl, —NHSO2—C3-C12-cycloalkyl, —NHSO2-aryl, —NHSO2-heteroaryl, —NHSO2-heterocycloalkyl, —CH2NH2, —CH2SO2CH3, -aryl, -arylalkyl, -heteroaryl, -heteroarylalkyl, -heterocycloalkyl, —C3-C12-cycloalkyl, polyalkoxyalkyl, polyalkoxy, -methoxymethoxy, -methoxyethoxy, —SH, —S—C1-C12-alkyl, —S—C2-C12-alkenyl, —S—C2-C12-alkynyl, —S—C3-C12-cycloalkyl, —S-aryl, —S-heteroaryl, —S-heterocycloalkyl, or methylthiomethyl. It is understood that the aryls, heteroaryls, alkyls and the like can be further substituted.
The terms “C2-C12 alkenyl” or “C2-C6 alkenyl,” as used herein, denote a monovalent group derived from a hydrocarbon moiety containing from two to twelve or two to six carbon atoms having at least one carbon-carbon double bond by the removal of a single hydrogen atom. Alkenyl groups include, but are not limited to, for example, ethenyl, propenyl, butenyl, 1-methyl-2-buten-1-yl, alkadienes and the like.
The term “substituted alkenyl,” as used herein, refers to a “C2-C12 alkenyl” or “C2-C6 alkenyl” group as previously defined, substituted by one, two, three or more aliphatic substituents.
The terms “C2-C12 alkynyl” or “C2-C6 alkynyl,” as used herein, denote a monovalent group derived from a hydrocarbon moiety containing from two to twelve or two to six carbon atoms having at least one carbon-carbon triple bond by the removal of a single hydrogen atom. Representative alkynyl groups include, but are not limited to, for example, ethynyl, 1-propynyl, 1-butynyl, and the like.
The term “substituted alkynyl,” as used herein, refers to a “C2-C12 alkynyl” or “C2-C6 alkynyl” group as previously defined, substituted by one, two, three or more aliphatic substituents.
The term “C1-C6 alkoxy,” as used herein, refers to a C1-C6 alkyl group, as previously defined, attached to the parent molecular moiety through an oxygen atom. Examples of C1-C6-alkoxy include, but are not limited to, methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, n-pentoxy, neopentoxy and n-hexoxy.
The terms “halo” and “halogen,” as used herein, refer to an atom selected from fluorine, chlorine, bromine and iodine.
The terms “aryl” or “aromatic” as used herein, refer to a mono- or bicyclic carbocyclic ring system having one or two aromatic rings including, but not limited to, phenyl, naphthyl, tetrahydronaphthyl, indanyl, idenyl and the like.
The terms “substituted aryl” or “substituted aromatic,” as used herein, refer to an aryl or aromatic group substituted by one, two, three or more aromatic substituents.
The term “arylalkyl,” as used herein, refers to an aryl group attached to the parent compound via a C1-C3 alkyl or C1-C6 alkyl residue. Examples include, but are not limited to, benzyl, phenethyl and the like.
The term “substituted arylalkyl,” as used herein, refers to an arylalkyl group, as previously defined, substituted by one, two, three or more aromatic substituents.
The terms “heteroaryl” or “heteroaromatic,” as used herein, refer to a mono-, bi-, or tri-cyclic aromatic radical or ring having from five to ten ring atoms of which at least one ring atom is selected from S, O and N; zero, one or two ring atoms are additional heteroatoms independently selected from S, O and N; and the remaining ring atoms are carbon, wherein any N or S contained within the ring may be optionally oxidized. Heteroaryl includes, but is not limited to, pyridinyl, pyrazinyl, pyrimidinyl, pyrrolyl, pyrazolyl, imidazolyl, thiazolyl, oxazolyl, isooxazolyl, thiadiazolyl, oxadiazolyl, thiophenyl, furanyl, quinolinyl, isoquinolinyl, benzimidazolyl, benzooxazolyl, quinoxalinyl, and the like. The heteroaromatic ring may be bonded to the chemical structure through a carbon or hetero atom.
The terms “substituted heteroaryl” or “substituted heteroaromatic,” as used herein, refer to a heteroaryl or heteroaromatic group, substituted by one, two, three, or more aromatic substituents.
The term “alicyclic,” as used herein, denotes a monovalent group derived from a monocyclic or bicyclic saturated carbocyclic ring compound by the removal of a single hydrogen atom. Examples include, but not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, bicyclo[2.2.1]heptyl, and bicyclo[2.2.2]octyl.
The term “substituted alicyclic,” as used herein, refers to an alicyclic group substituted by one, two, three or more aliphatic substituents.
The term “heterocyclic,” as used herein, refers to a non-aromatic 5-, 6- or 7-membered ring or a bi- or tri-cyclic group fused system, where (i) each ring contains between one and three heteroatoms independently selected from oxygen, sulfur and nitrogen, (ii) each 5-membered ring has 0 to 1 double bonds and each 6-membered ring has 0 to 2 double bonds, (iii) the nitrogen and sulfur heteroatoms may optionally be oxidized, (iv) the nitrogen heteroatom may optionally be quatemized, (iv) any of the above rings may be fused to a benzene ring, and (v) the remaining ring atoms are carbon atoms which may be optionally oxo-substituted. Representative heterocycloalkyl groups include, but are not limited to, [1,3]dioxolane, pyrrolidinyl, pyrazolinyl, pyrazolidinyl, imidazolinyl, imidazolidinyl, piperidinyl, piperazinyl, oxazolidinyl, isoxazolidinyl, morpholinyl, thiazolidinyl, isothiazolidinyl, quinoxalinyl, pyridazinonyl, and tetrahydrofuryl.
The term “substituted heterocyclic,” as used herein, refers to a heterocyclic group, as previously defined, substituted by one, two, three or more aliphatic substituents.
The term “heteroarylalkyl,” as used herein, to an heteroaryl group attached to the parent compound via a C1-C3 alkyl or C1-C6 alkyl residue. Examples include, but are not limited to, pyridinylmethyl, pyrimidinylethyl and the like.
The term “substituted heteroarylalkyl,” as used herein, refers to a heteroarylalkyl group, as previously defined, substituted by independent replacement of one, two, or three or more aromatic substituents.
The term “alkylamino” refers to a group having the structure —NH(C1-C12 alkyl).
The term “dialkylamino” refers to a group having the structure —N(C1-C12 alkyl) (C1-C12 alkyl), where C1-C12 alkyl is as previously defined. Examples of dialkylamino are, but not limited to, dimethylamino, diethylamino, methylethylamino, piperidino, and the like.
The term “alkoxycarbonyl” represents an ester group, i.e., an alkoxy group, attached to the parent molecular moiety through a carbonyl group such as methoxycarbonyl, ethoxycarbonyl, and the like.
The term “carboxaldehyde,” as used herein, refers to a group of formula —CHO.
The term “carboxy,” as used herein, refers to a group of formula —COOH.
The term “carboxamide,” as used herein, refers to a group of formula —C(O)NH(C1-C12 alkyl) or —C(O)N(C1-C12 alkyl) (C1-C12 alkyl), —C(O)NH2, NHC(O)(C1-C12 alkyl), N(C1-C12 alkyl)C(O)(C1-C12 alkyl) and the like.
The term “hydroxy protecting group,” as used herein, refers to a labile chemical moiety which is known in the art to protect a hydroxyl group against undesired reactions during synthetic procedures. After said synthetic procedure(s) the hydroxy protecting group as described herein may be selectively removed. Hydroxy protecting groups as known in the are described generally in T. H. Greene and P. G. M. Wuts, Protective Groups in Organic Synthesis, 3rd edition, John Wiley & Sons, New York (1999). Examples of hydroxyl protecting groups include benzyloxycarbonyl, 4-nitrobenzyloxycarbonyl, 4-bromobenzyloxycarbonyl, 4-methoxybenzyloxycarbonyl, methoxycarbonyl, tert-butoxycarbonyl, isopropoxycarbonyl, diphenylmethoxycarbonyl, 2,2,2-trichloroethoxycarbonyl, 2-(trimethylsilyl)ethoxycarbonyl, 2-furfuryloxycarbonyl, allyloxycarbonyl, acetyl, formyl, chloroacetyl, trifluoroacetyl, methoxyacetyl, phenoxyacetyl, benzoyl, methyl, t-butyl, 2,2,2-trichloroethyl, 2-trimethylsilyl ethyl, 1,1-dimethyl-2-propenyl, 3-methyl-3-butenyl, allyl, benzyl, para-methoxybenzyldiphenylmethyl, triphenylmethyl(trityl), tetrahydrofuryl, methoxymethyl, methylthiomethyl, benzyloxymethyl, 2,2,2-triehloroethoxymethyl, 2-(trimethylsilyl)ethoxymethyl, methanesulfonyl, para-toluenesulfonyl, trimethylsilyl, triethylsilyl, triisopropylsilyl, and the like. Preferred hydroxyl protecting groups for the present invention are acetyl (Ac or —C(O)CH3), benzoyl (Bz or —C(O)C6H5), and trimethylsilyl (TMS or —Si(CH3)3).
The term “protected hydroxy,” as used herein, refers to a hydroxy group protected with a hydroxy protecting group, as defined above, including benzyloxycarbonyl, 4-nitrobenzyloxycarbonyl, 4-bromobenzyloxycarbonyl, 4-methoxybenzyloxycarbonyl, methoxycarbonyl, tert-butoxycarbonyl, isopropoxycarbonyl, diphenylmethoxycarbonyl, 2,2,2-trichloroethoxycarbonyl, 2-(trimethylsilyl)ethoxycarbonyl, 2-furfuryloxycarbonyl, allyloxycarbonyl, acetyl, formyl, chloroacetyl, trifluoroacetyl, methoxyacetyl, phenoxyacetyl, benzoyl, methyl, t-butyl, 2,2,2-trichloroethyl, 2-trimethylsilyl ethyl, 1,1-dimethyl-2-propenyl, 3-methyl-3-butenyl, allyl, benzyl, para-methoxybenzyldiphenylmethyl, triphenylmethyl(trityl), tetrahydrofuryl, methoxymethyl, methylthiomethyl, benzyloxymethyl, 2,2,2-triehloroethoxymethyl, 2-(trimethylsilyl)ethoxymethyl, methanesulfonyl, para-toluenesulfonyl, trimethylsilyl, triethylsilyl, triisopropylsilyl, and the like. Preferred hydroxyl protecting groups for the present invention are acetyl (Ac or —C(O)CH3), benzoyl (Bz or —C(O)C6H5), and trimethylsilyl (TMS or —Si(CH3)3).
The term “amino protecting group,” as used herein, refers to a labile chemical moiety which is known in the art to protect an amino group against undesired reactions during synthetic procedures. After said synthetic procedure(s) the amino protecting group as described herein may be selectively removed. Amino protecting groups as known in the are described generally in T. H. Greene and P. G. M. Wuts, Protective Groups in Organic Synthesis, 3rd edition, John Wiley & Sons, New York (1999). Examples of amino protecting groups include, but are not limited to, t-butoxycarbonyl, 9-fluorenylmethoxycarbonyl, benzyloxycarbonyl, and the like.
The term “protected amino,” as used herein, refers to an amino group protected with an amino protecting group as defined above.
The term “acy” includes residues derived from acids, including but not limited to carboxylic acids, carbamic acids, carbonic acids, sulfonic acids, and phosphorous acids. Examples include aliphatic carbonyls, aromatic carbonyls, aliphatic sulfonyls, aromatic sulfinyls, aliphatic sulfinyls, aromatic phosphates and aliphatic phosphates.
The term “aprotic solvent,” as used herein, refers to a solvent that is relatively inert to proton activity, i.e., not acting as a proton-donor. Examples include, but are not limited to, hydrocarbons, such as hexane and toluene, for example, halogenated hydrocarbons, such as, for example, methylene chloride, ethylene chloride, chloroform, and the like, heterocyclic compounds, such as, for example, tetrahydrofuran and N-methylpyrrolidinone, and ethers such as diethyl ether, bis-methoxymethyl ether. Such compounds are well known to those skilled in the art, and it will be obvious to those skilled in the art that individual solvents or mixtures thereof may be preferred for specific compounds and reaction conditions, depending upon such factors as the solubility of reagents, reactivity of reagents and preferred temperature ranges, for example. Further discussions of aprotic solvents may be found in organic chemistry textbooks or in specialized monographs, for example: Organic Solvents Physical Properties and Methods of Purification, 4th ed., edited by John A. Riddick et al., Vol. II, in the Techniques of Chemistry Series, John Wiley & Sons, NY, 1986.
The term “protogenic organic solvent,” as used herein, refers to a solvent that tends to provide protons, such as an alcohol, for example, methanol, ethanol, propanol, isopropanol, butanol, t-butanol, and the like. Such solvents are well known to those skilled in the art, and it will be obvious to those skilled in the art that individual solvents or mixtures thereof may be preferred for specific compounds and reaction conditions, depending upon such factors as the solubility of reagents, reactivity of reagents and preferred temperature ranges, for example. Further discussions of protogenic solvents may be found in organic chemistry textbooks or in specialized monographs, for example: Organic Solvents Physical Properties and Methods of Purification, 4th ed., edited by John A. Riddick et al., Vol. II, in the Techniques of Chemistry Series, John Wiley & Sons, NY, 1986.
The term “oxidizing agent(s),” as used herein, refers to reagents useful for oxidizing the 3-hydroxyl of the macrolide ring to the 3-carbonyl. Oxidizing agents suitable in the present process are either Swem oxidation reagents (dimethyl sulfoxide and an electrophilic compound selected from dicyclohexylcarbodiimide, acetic anhydride, trifluoroacetic anhydride, oxalyl chloride, or sulfur trioxide), Dess Martin oxidation reagents, or Corey-Kim oxidation reagents. A preferred method of oxidation is the use of the Corey-Kim oxidation reagents N-chlorosuccinimide-dimethyl sulfide complex.
The term “palladium catalyst,” as used herein, refers to optionally supported palladium(0) such as palladium metal, palladium on carbon, palladium on acidic, basic, or neutral alumina, and the like; palladium(0) complexes such as tetrakis(triphenylphosphine)palladium(0) tris(dibenzylideneacetone)dipalladium(0); palladium(II) salts such as palladium acetate or palladium chloride; and palladium(II) complexes such as allylpalladium(II) chloride dimer, (1,1′-bis(diphenylphosphino)ferrocene)-dichloropalladium(II), bis(acetato)bis(triphenylphosphine)palladium(II), and bis(acetonitrile)dichloropalladium(II).
Combinations of substituents and variables envisioned by this invention are only those that result in the formation of stable compounds. The term “stable”, as used herein, refers to compounds which possess stability sufficient to allow manufacture and which maintains the integrity of the compound for a sufficient period of time to be useful for the purposes detailed herein.
The synthesized compounds can be separated from a reaction mixture and further purified by a method such as column chromatography, high pressure liquid chromatography, or recrystallization. As can be appreciated by the skilled artisan, further methods of synthesizing the compounds of the formulae herein will be evident to those of ordinary skill in the art. Additionally, the various synthetic steps may be performed in an alternate sequence or order to give the desired compounds. Synthetic chemistry transformations and protecting group methodologies (protection and deprotection) useful in synthesizing the compounds described herein are known in the art and include, for example, those such as described in R. Larock, Comprehensive Organic Transformations, VCH Publishers (1989); T. W. Greene and P. G. M. Wuts, Protective Groups in Organic Synthesis, 2d. Ed., John Wiley and Sons (1991); L. Fieser and M. Fieser, Fieser and Fieser's Reagents for Organic Synthesis, John Wiley and Sons (1994); and L. Paquette, ed., Encyclopedia of Reagents for Organic Synthesis, John Wiley and Sons (1995).
The compounds of this invention may be modified by appending appropriate functionalities to enhance selective biological properties. Such modifications are known in the art and may include those which increase biological penetration into a given biological system (e.g., blood, lymphatic system, central nervous system), increase oral availability, increase solubility to allow administration by injection, alter metabolism and alter rate of excretion.
The compounds described herein contain one or more asymmetric centers and thus give rise to enantiomers, diastereomers, and other stereoisomeric forms that may be defined, in terms of absolute stereochemistry, as (R)- or (S)-, or as (D)- or (L)- for amino acids. The present invention is meant to include all such possible isomers, as well as their racemic and optically pure forms. Optical isomers may be prepared from their respective optically active precursors by the procedures described above, or by resolving the racemic mixtures. The resolution can be carried out in the presence of a resolving agent, by chromatography or by repeated crystallization or by some combination of these techniques which are known to those skilled in the art. Further details regarding resolutions can be found in Jacques, et al., Enantiomers Racemates and Resolutions (John Wiley & Sons, 1981). When the compounds described herein contain olefinic double bonds, other unsaturation, or other centers of geometric asymmetry, and unless specified otherwise, it is intended that the compounds include both E and Z geometric isomers or cis- and trans- isomers. Likewise, all tautomeric forms are also intended to be included. The configuration of any carbon-carbon double bond appearing herein is selected for convenience only and is not intended to designate a particular configuration unless the text so states; thus a carbon-carbon double bond or carbon-heteroatom double bond depicted arbitrarily herein as trans may be cis, trans, or a mixture of the two in any proportion.
As used herein, the term “pharmaceutically acceptable salt” refers to those salts which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of humans and lower animals without undue toxicity, irritation, allergic response and the like, and are commensurate with a reasonable benefit/risk ratio. Pharmaceutically acceptable salts are well known in the art. For example, S. M. Berge, et al. describes pharmaceutically acceptable salts in detail in J. Pharmaceutical Sciences, 66: 1-19 (1977). The salts can be prepared in situ during the final isolation and purification of the compounds of the invention, or separately by reacting the free base function with a suitable organic acid. Examples of pharmaceutically acceptable include, but are not limited to, nontoxic acid addition salts are salts of an amino group formed with inorganic acids such as hydrochloric acid, hydrobromic acid, phosphoric acid, sulfuric acid and perchloric acid or with organic acids such as acetic acid, maleic acid, tartaric acid, citric acid, succinic acid or malonic acid or by using other methods used in the art such as ion exchange. Other pharmaceutically acceptable salts include, but are not limited to, adipate, alginate, ascorbate, aspartate, benzenesulfonate, benzoate, bisulfate, borate, butyrate, camphorate, camphorsulfonate, citrate, cyclopentanepropionate, digluconate, dodecylsulfate, ethanesulfonate, formate, fumarate, glucoheptonate, glycerophosphate, gluconate, hemisulfate, heptanoate, hexanoate, hydroiodide, 2-hydroxy-ethanesulfonate, lactobionate, lactate, laurate, lauryl sulfate, malate, maleate, malonate, methanesulfonate, 2-naphthalenesulfonate, nicotinate, nitrate, oleate, oxalate, palmitate, pamoate, pectinate, persulfate, 3-phenylpropionate, phosphate, picrate, pivalate, propionate, stearate, succinate, sulfate, tartrate, thiocyanate, p-toluenesulfonate, undecanoate, valerate salts, and the like. Representative alkali or alkaline earth metal salts include sodium, lithium, potassium, calcium, magnesium, and the like. Further pharmaceutically acceptable salts include, when appropriate, nontoxic ammonium, quaternary ammonium, and amine cations formed using counterions such as halide, hydroxide, carboxylate, sulfate, phosphate, nitrate, alkyl having from 1 to 6 carbon atoms, sulfonate and aryl sulfonate.
As used herein, the term “pharmaceutically acceptable ester” refers to esters which hydrolyze in vivo and include those that break down readily in the human body to leave the parent compound or a salt thereof. Suitable ester groups include, for example, those derived from pharmaceutically acceptable aliphatic carboxylic acids, particularly alkanoic, alkenoic, cycloalkanoic and alkanedioic acids, in which each alkyl or alkenyl moiety advantageously has not more than 6 carbon atoms. Examples of particular esters include, but are not limited to, formates, acetates, propionates, butyrates, acrylates and ethylsuccinates.
The term “pharmaceutically acceptable prodrugs” as used herein refers to those prodrugs of the compounds of the present invention which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of humans and lower animals with undue toxicity, irritation, allergic response, and the like, commensurate with a reasonable benefit/risk ratio, and effective for their intended use, as well as the zwitterionic forms, where possible, of the compounds of the present invention. “Prodrug”, as used herein means a compound which is convertible in vivo by metabolic means (e.g. by hydrolysis) to a compound of Formula I. Various forms of prodrugs are known in the art, for example, as discussed in Bundgaard, (ed.), Design of Prodrugs, Elsevier (1985); Widder, et al. (ed.), Methods in Enzymology, vol. 4, Academic Press (1985); Krogsgaard-Larsen, et al., (ed). “Design and Application of Prodrugs, Textbook of Drug Design and Development, Chapter 5, 113-191 (1991); Bundgaard, et al., Journal of Drug Deliver Reviews, 8:1-38(1992); Bundgaard, J. of Pharmaceutical Sciences, 77:285 et seq. (1988); Higuchi and Stella (eds.) Prodrugs as Novel Drug Delivery Systems, American Chemical Society (1975); and Bernard Testa & Joachim Mayer, “Hydrolysis In Drug And Prodrug Metabolism: Chemistry, Biochemistry And Enzymology,” John Wiley and Sons, Ltd. (2002).
This invention also encompasses pharmaceutical compositions containing, and methods of treating bacterial infections through administering, pharmaceutically acceptable prodrugs of compounds of the formula I. For example, compounds of formula I having free amino, amido, hydroxy or carboxylic groups can be converted into prodrugs. Prodrugs include compounds wherein an amino acid residue, or a polypeptide chain of two or more (e.g., two, three or four) amino acid residues is covalently joined through an amide or ester bond to a free amino, hydroxy or carboxylic acid group of compounds of formula I. The amino acid residues include but are not limited to the 20 naturally occurring amino acids commonly designated by three letter symbols and also includes 4-hydroxyproline, hydroxylysine, demosine, isodemosine, 3-methylhistidine, norvalin, beta-alanine, gamma-aminobutyric acid, citrulline homocysteine, homoserine, ornithine and methionine sulfone. Additional types of prodrugs are also encompassed. For instance, free carboxyl groups can be derivatized as amides or alkyl esters. Free hydroxy groups may be derivatized using groups including but not limited to hemisuccinates, phosphate esters, dimethylaminoacetates, and phosphoryloxymethyloxycarbonyls, as outlined in Advanced Drug Delivery Reviews, 1996, 19, 115. Carbamate prodrugs of hydroxy and amino groups are also included, as are carbonate prodrugs, sulfonate esters and sulfate esters of hydroxy groups. Derivatization of hydroxy groups as (acyloxy)methyl and (acyloxy)ethyl ethers wherein the acyl group may be an alkyl ester, optionally substituted with groups including but not limited to ether, amine and carboxylic acid functionalities, or where the acyl group is an amino acid ester as described above, are also encompassed. Prodrugs of this type are described in J. Med. Chem. 1996, 39, 10. Free amines can also be derivatized as amides, sulfonamides or phosphonamides. All of these prodrug moieties may incorporate groups including but not limited to ether, amine and carboxylic acid functionalities.
Suitable concentrations of reactants is 0.01M to 10M, typically 0.1M to 1M. Suitable temperatures include −10° C. to 250° C., typically −78° C. to 150° C., more typically −78° C. to 100° C., still more typically 0° C. to 100° C. Reaction vessels are preferably made of any material which does not substantial interfere with the reaction. Examples include glass, plastic, and metal. The pressure of the reaction can advantageously be operated at atmospheric pressure. The atmospheres includes, for example, air, for oxygen and water insensitive reactions, or nitrogen or argon, for oxygen or water sensitive reactions.
The term “in situ,” as used herein, refers to use of an intermediate in the solvent or solvents in which the intermediate was prepared without removal of the solvent.
Unless otherwise defined, all technical and scientific terms used herein are accorded the meaning commonly known to one with ordinary skill in the art. All publications, patents, published patent applications, and other references mentioned herein are hereby incorporated by reference in their entirety.
Abbreviations
Abbreviations which may be used in the descriptions of the scheme and the examples that follow are:
Ac for acetyl;
AIBN for azobisisobutyronitrile;
Bu3SnH for tributyltin hydride;
CDI for carbonyldiimidazole;
dba for dibenzylidene acetone;
dppb for diphenylphosphino butane or 1,4-bis(diphenylphosphino)butane;
DBU for 1,8-diazabicyclo[5.4.0]undec-7-ene;
DEAD for diethylazodicarboxylate;
DMAP for dimethylaminopyridine;
DMF for dimethyl formamide;
DPPA for diphenylphosphoryl azide;
EtOAc for ethyl acetate;
HPLC for high-pressure liquid chromatography;
MeOH for methanol;
NaN(TMS)2 for sodium bis(trimethylsilyl)amide;
NMM for N-methylmorpholine;
NMMO for N-methylmorpholine N-oxide;
TEA for triethylamine;
THF for tetrahydrofuran;
TPP or PPh3 for triphenylphosphine;
MOM for methoxymethyl;
Boc for t-butoxycarbonyl;
Bz for benzoyl;
Bn for benzyl;
Ph for phenyl;
POPd for dihydrogen dichlorobis(di-tert-butylphosphinito-κP)palladate(II);
TBS for tert-butyl dimethylsilyl; or
TMS for trimethylsilyl.
All other abbreviations used herein, which are not specifically delineated above, shall be accorded the meaning which one of ordinary skill in the art would attach.
Synthetic Schemes
The present invention will be better understood in connection with Schemes 1-6. It will be readily apparent to one of ordinary skill in the art that the process of the present invention can be practiced by substitution of the appropriate reactants and that the order of the steps themselves can be varied.
Erythromycins can be protected as 9-oximes of formula (I-a) as described in U.S. Pat. Nos. 4,990,602; 4,331,803; 4,680,386; and 4,670,549. Reaction of erythromycin A with hydroxylamine and formic acid in methanol provides a compound of formula (I) wherein Q is OH and Z is




which can be further derivatized without isolation. The preferred amount of hydroxylamine is about 7 to about 10 molar equivalents per molar equivalent of erythromycin A. From about 2 to about 5 molar equivalents of formic acid are used for each molar equivalent of erythromycin A.

The 2′- and 4′′-hydroxyl groups as well as the hydroxyl of the 9-oxime of compounds of formula (I-a) can be protected sequentially or simultaneously by reaction with a suitable hydroxyl-protecting reagent in an aprotic solvent, optionally in the presence of catalytic amounts of base, such as DMAP and/or TEA, as described in U.S. Pat. No. 5,892,008, to provide a compound of formula (I-b). Typical hydroxyl-protecting reagents include acetylating agents and silylating agents such as acetyl chloride, acetic anhydride, benzoyl chloride, benzoic anhydride, benzyl chloroformate, hexamethyldisilazane, and trialkylsilyl chlorides. A preferred hydroxyl-protecting reagent of the present invention is acetic anhydride.
Compounds of formula II, useful in the preparation of compounds of formula III, are prepared by treating 2-methylene-1,3-propanediol with di-tert-butyl dicarbonate in an aprotic solvent, in the presence of a phase transfer catalyst (PTC) and an aqueous base. PTCs suitable for the present process include, but are not limited to, tetrabutylammonium bromide, tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium fluoride trihydrate, tetrabutylammonium hydrogen sulfate, tetrabutylammonium iodide, tetrabutylammonium thiocyanate, tetrabutylammonium tetrafluoroborate, benzyltetrabutylammonium chloride, and the like; the preferred of which is tetrabutylammonium hydrogen sulfate. In a preferred embodiment of the present conversion, the aprotic solvent is dichloromethane, the aqueous base is 4M to 8M NaOH.




As illustrated in Scheme 1, step A, erythromycin derivatives of formula (I-b) are converted in the present invention to compounds of formula (III-a) by the treatment of the former with compounds of formula (II):




preferably where R1 is tert-butyl, isopropyl, or isobutyl. In a preferred embodiment, the conversion takes place in an aprotic solvent, at a temperature range of between 30° C. and 100° C., in the presence of a palladium catalyst and an additive for a period of less than about 12 hours.

Alkylation of a compound of formula (I-b) with a compound of formula (II) preferably takes place in the presence of a palladium catalyst. Most palladium(0) catalysts are expected be effective in this process. Some palladium(II) catalysts, such as palladium(II) acetate, which are converted into a palladium(0) species in-situ by a phosphine, will be effective as well. See, for example, Beller et al. Angew. Chem. Int. Ed. Engl., 1995, 34 (17), 1848. A suitable palladium catalyst for this reaction includes, but is not limited to, palladium(II) acetate, tetrakis(triphenylphospine)palladium(0), tris(dibenzylideneacetone)dipalladium(0) (Pd2(dba)3), tetradi(benzylideneacetone)dipalladium and the like. Palladium on carbon and palladium(II) halide catalysts are less preferred than other palladium catalysts for this process. A preferred palladium catalyst for this process is a palladium(0) catalyst. A particularly preferred palladium catalyst for this process is Pd2(dba)3.
In addition, the process is preferably performed in the presence of an additive. Examples of preferred additives include monodentate phosphorus-containing ligands of formulas P(RC)3 (phosphines) and P(ORD)3 (phosphites), wherein each RC is independently hydrogen; alkyl such as methyl, ethyl, and tert-butyl; cycloalkyl such as cyclopropyl and cyclohexyl; optionally substituted aryl, such as phenyl, naphthyl, and ortho-tolyl; and optionally substituted heteroaryl such as furyl and pyridyl; and wherein each RD is independently alkyl such as methyl, ethyl, and tert-butyl; cycloalkyl, such as cyclopropyl and cyclohexyl; optionally substituted aryl, such as phenyl, naphthyl, and ortho-tolyl; and optionally substituted heteroaryl, such as furyl and pyridyl. Specific examples of additives include, but are not limited to, tri(alkyl)phosphines such as trimethylphosphine, triethylphosphine, tributylphosphine, and the like; tri(cycloalkryl)phosphines such as tricyclopropylphosphine, tricyclohexylphosphine, and the like; tri(aryl)phosphines such as triphenylphosphine, trinaphthylphosphine, and the like; tri(heteroaryl)phosphines such as tri(fury-2-yl)phosphine, tri(pyrid-3-yl)phosphine, and the like; tri(alkyl)phosphites such as trimethylphosphite, triethylphosphite, tributylphosphite, and the like; tri(cycloalkyl)-phosphites such as tricyelopropylphosphite, tricyclohexylphosphite, and the like; tri(aryl)phosphites such as triphenylphosphite, trinaphthylphosphite, and the like; and tri(heteroaryl)phosphites such as tri(fury-2-yl)phosphite, tri(pyrid-3-yl)phosphite, and the like. The term “additive,” as used herein, also refers to bidentate phosphines such as 1,4-bis(diphenylphosphino)butane (dppb), 1,2-bis(diphenyl-phosphino)ethane (dppe), 1,1-bis(diphenylphosphino)methane (dppm), 1,2-bis(dimethyl-phosphino)ethane (dmpe), 1,1′-bis(diphenylphosphino)ferrocene (dppf), and the like. A particularly preferred additive of the instant process is 1,4-bis(diphenylphosphino)butane (dppb).
The process is carried out in an aprotic solvent. Suitable aprotic solvents include, but are not limited to, tetrahydrofuran, N,N-dimethylformamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, hexamethylphosphoric triamide, 1,2-dimethoxyethane, methyl-tert-butyl ether, heptane, acetonitrile, isopropyl acetate and ethyl acetate. Preferred aprotic solvents are tetrahydrofuran or toluene.
The instant conversion is performed preferably at an elevated temperature between 30 and 100° C. A particularly preferred temperature range is between 55° C. and 85° C. A most preferred temperature range for the instant alkylation process is between 60° C. and 75° C.
The instant alkylation process is generally conducted until at least 50% completion, preferably at least about 70% completion, typically until at least 95% completion. Generally, the reaction time will be less than about 12 hours. A preferred reaction time range for the present alkylation process is less than about 8 hours. A most preferred reaction time range for the present alkylation process is less than about 7 hours.
A compound of formula (III-a), wherein R1 and Rp are as previously defined, are converted to a compound of formula (IV-a), wherein Rp is as previously defined, via the process illustrated in Scheme 1, step B. The removal of the cladinose moiety may be achieved either by mild acid hydrolysis or by enzymatic hydrolysis, at a temperature range of between −10° C. and 80° C., for a time period of from 0.5 to 24 hours, to afford a compound of formula (IV-a). Representative acids include dilute hydrochloric acid, sulfuric acid, perchloric acid, chloroacetic acid, dichloroacetic acid or trifluoroacetic acid. Suitable solvents for the reaction include water, methanol, ethanol, isopropanol, butanol and the like. In a preferred embodiment, the removal of the cladinose moiety is achieved by treatment with aqueous hydrochloric acid, for a period of 1 to 2 hours, at a temperature between 50° C. and 70° C. In a most preferred embodiment, 1M aqueous hydrochloric acid is used at a temperature of about 60° C.




As illustrated in Scheme 2, Step A, conversion of a compound of formula (IV-a) to a compound of formula (V), may be achieved by treating the former with a reducing agent. Reducing agents suitable for this conversion include, but are not limited to, lithium aluminum hydride, titanium(III)chloride, borane, and various sulfides such as sodium hydrogen sulfide and sodium nitrite. For a more detailed account of oxime reduction reaction, see J. March in “Advanced Organic Chemistry” 4th ed., Wiley & Son, Inc, 1992. In a particularly preferred embodiment, a compound of formula (IV-a) is treated with a titanium(III) reducing agent (preferably titanium(III)chloride), under acidic conditions, typically in a protogenic organic solvent. Preferred acids include, but are not limited to, acetic acid, formic acid, dilute hydrochloric acid, dilute phosphoric acid, dilute sulfuric acid, and the like. A particularly preferred acid for the present conversion is aqueous hydrochloric acid. Protogenic organic solvents suitable in this preferred embodiment include, but are not limited to, mixtures of water and methanol, ethanol, isopropanol, or butanol. A particularly preferred protogenic organic solvent for the present conversion is ethanol. The conversion is carried out between 10° C. and 110° C. (preferably between about 20° C. and 50° C.) and over a period of less than about 10 hours (preferably between 2 to 4 hours).
As illustrated in Scheme 2, Step B, compounds of formula (V) can be converted to compounds of formula (VI) by treating the former with an acylating agent. In a preferred embodiment, the conversion is carried out in an aprotic solvent. Acylating agents suitable for the instant conversion include, but are not limited to, acetyl chloride, acetic anhydride, benzoyl chloride, benzoic anhydride, and benzyl chloroformate.
Aprotic solvents suitable for the present conversion are dichloromethane, chloroform, tetrahydrofuran, N-methylpyrrolidinone, dimethylsulfoxide, N,N-dimethylformamide, N,N -dimethylacetamide, hexamethylphosphoric triamide, a mixture thereof or a mixture of one of these solvents with ether, tetrahydrofuran, 1,2-dimethoxyethane, 1,2-dichloroethane, acetonitrile, ethyl acetate, acetone, and the like. A preferred aprotic solvent of the present process is selected from dichloromethane, chloroform, N,N-dimethylformamide, tetrahydrofuran, N-methylpyrrolidinone or mixtures thereof. A particularly preferred aprotic solvent is dichloromethane.




Scheme 3 illustrates the process converting a compound of formula (VI) into a compound of formula (VII) through treatment with a reagent or reagents capable of performing oxidative cleavage. Oxidative cleavage may be performed by, for example, ozonolysis or by treatment with an oxidant followed by a cleaving reagent. Ozonolysis may be achieved by treating the alkene of a compound of formula (VI) with ozone followed by decomposition of the ozonide with the appropriate reducing agent. Suitable reducing agents for this process include, but are not limited to, dimethyl sulfide, zinc, trivalent phosphorous compounds, sodium sulfite, and the like. The reaction is typically carried out in an inert solvent such as, but not limited to, methanol, ethanol, ethyl acetate, glacial acetic acid, chloroform, methylene chloride or hexanes or mixtures thereof, preferably methanol, preferably at about −78° to −20° C. Preferred reducing agents include, but are not limited to, triphenylphosphine, trimethyl phosphite, thiourea, and dimethyl sulfide, preferably triphenylphosphine. A more thorough discussion of ozonolysis and the conditions there for can be found in J. March “Advanced Organic Chemistry”4th ed., Wiley & Son, Inc, 1992.
An alternative method for the preparation of a compound of formula (VII) involves dihydroxylation of a compound of formula (IV) by an oxidant followed by treatment with a cleaving reagent. The glycol is first prepared by reacting alkene with an oxidant. Suitable oxidants for the present process include, but are not limited to, permanganate ion and osmium tetroxide. The process may utilize stochiometric amounts of osmium tetroxide, or, if in the presence of an additional oxidant such as hydrogen peroxide, tert-butyl hydroperoxide, N-methylmorpholine-N-oxide, or barium chlorate only catalytic amounts of osmium tetroxide are necessary. Dihydroxylation reactions can be carried out in a variety of solvents including: 1,4-dioxane, tetrahydrofuran, tert-butanol and diethyl ether, preferably at a temperature of between −15° C. and 15° C.
The resulting glycol can be cleaved by a variety of cleaving reagents including, but not limited to, periodic acid, lead tetraacetate, manganesedioxide, potassium permanganate, sodium metaperiodate, and N-iodosuccinamide. Preferably the cleavage reagent is sodium periodate, the solvent is preferably a mixture of acetone, THF, ethanol, methanol or 1,4-dioxane and water at a temperature of between 0° to 80° C.
A compound of the formula (VII) may be prepared by oxidation of the 3-position alcohol using an oxidizing agent or agents. Oxidizing agents suitable in the present process are either Swern oxidation reagents (dimethyl sulfoxide and an electrophilic compound selected from dicyclohexylcarbodiimide, acetic anhydride, trifluoroacetic anhydride, oxalyl chloride, or sulfur trioxide), Dess-Martin periodane, or Corey-Kim oxidation reagents. A preferred method of oxidation is the use of the Corey-Kim oxidation reagents N-chlorosuccinimide and dimethyl sulfide. The reaction typically takes place in an aprotic solvent at a temperature of between about −78° to 25° C. The reaction time typically is less than 12 hours. A more thorough discussion of the state of the art regarding oxidation of secondary alcohols can be found in J. March in “Advanced Organic Chemistry” 4th ed., Wiley & Son, Inc, 1992.




A compound of formula (VIII) represents a useful intermediate which can be further functionalized in a variety of ways. Scheme 4 details a procedure for the conversion of a compound of formula (VIIIinto an oxime compound of formula (IX-a), by first treating with hydroxylamine of formula (X) followed by deprotection of the 2′ hydroxyl. Oxime formation can be accomplished under either acidic or basic conditions in a variety of solvents. Representative acids include, but are not limited to, hydrochloric, camphorsulfonic acid, phosphoric, sulfuric, para-toluenesulfonic, and pyridinium p-toluene sulfonate. Likewise bases which are useful include, but are not limited to, triethylamine, pyridine, diisopropylethyl amine 1,5-lutidine, imidazole, and the like. Appropriate solvents include, but are not limited to, methanol, ethanol, water, tetrahydrofuran, 1,2-dimethoxyethane, and ethyl acetate. Preferably the reaction is run in ethanol using triethylamine as the base. The reaction temperature is generally 0° C. to 50° C. and the duration of the reaction is less than 12 hours. The deprotection can be achieved by for example methanolysis.




Scheme 5 illustrates the synthesis of the side chain (X). As outlined in Scheme 5, Step A, a compound of formula (X) is prepared by by hydrogenation or transfer hydrogenation of 4-(hydroxymethyl)-2-nitrophenol with palladium catalyst in the presence of an acid, preferably in a protogenic solvent, to provide a compound of the formula (XII). In a preferred embodiment of the instant reaction, the reaction temperature is between 20° C. and 60° C. In a particularly preferred embodiment of the instant reaction, 10% Pd/C and ammonium formate are used, and the protogenic solvent is methanol.
A compound of formula (XIII) is prepared, as illustrated in Step B of Scheme 5, by treating a compound of formula (XII) with cyanogen bromide the presence of a protogenic solvent preferably ethanol or methanol. Preferably, the reaction is performed at room temperature to reflux conditions.
A compound of formula (XIV) is prepared, as illustrated in Step C of Scheme 5, by halogenating compound of formula (XIII) with a halogenating agent. Halogenating agents suitable for the instant conversion include, but are not limited to, PBr3, thionyl chloride, and the like. The present reaction preferably takes place in an aprotic solvent, at a temperature between about 0° C. and 50° C., for a duration of less than 24 hours. Most preferably the present conversion takes place in methylene chloride, at room temperature, and for a duration of from 12 to 18 hours.
A compound of formula (XI) is prepared, as illustrated in Step D of Scheme 5, by adding the compound of formula R3R4NOH to a compound of formula (XIV), where R3 and R4 are taken together with the nitrogen atom to form




wherein A and B wherein A and B are hydrogen or A and B taken together with the carbons to which they are attached form a cyclic moiety selected from aryl, substituted aryl, heterocyclic, substituted heterocyclic, alicyclic, or substituted alicyclic. Preferably A and B are hydrogen or A and B taken together with the carbon atoms to which they are attached are phenyl. The present conversion preferably takes place in the presence of a base in an aprotic solvent.

A compound of formula (X) is prepared, as illustrated in Step E of Scheme 5, by hydrolyzing the compound of formula (XI) with a base in a protogenic organic solvent or an aqueous mixture thereof. Preferably the base is either hydrazine or ammonia.




Alternatively compound of formula (X) can also be prepared as outlined in Scheme 6. A compound of formula (XVI) is prepared, as illustrated in Step A of Scheme 6, by treating 2-amino-4-methylphenol with cyanogen bromide the presence of a protogenic solvent preferably ethanol or methanol. Preferably, the reaction is performed at room temperature to reflux conditions.
The amino moiety of compound (XVI) can be protected with a suitable amino protecting including but not limited to an acyl group or succinimide to furnish compound of the formula (XVI). Preferably, the protecting group is succinimide. The present conversion preferably takes place with succinic anhydride in the presence of an alkylating reagent such as HATU and a base such as N-methylmorpholine. Preferably, the reaction is performed at room temperature to reflux conditions.
A compound of formula (XVIII) is prepared, as illustrated in Step C of scheme 6 with standard bromination conditions that are well known in the art of chemistry. Preferably, compound (XVII) is treated with NBS in the presence of benzoyl peroxide in an aprotic solvent such as carbon tetrachloride. Preferably, the reaction is performed at room temperature to reflux conditions.
A compound of formula (XV) is prepared, as illustrated in Step D of Scheme 6, by adding the compound of formula R3R4NOH to a compound of formula (XVIII), where R3 and R4 are taken together with the nitrogen atom to form




wherein A and B wherein A and B are hydrogen or A and B taken together with the carbons to which they are attached form a cyclic moiety selected from aryl, substituted aryl, heterocyclic, substituted heterocyclic, alicyclic, or substituted alicyclic. Preferably A and B are hydrogen or A and B taken together with the carbon atoms to which they are attached are phenyl. The present conversion preferably takes place in the presence of a base in an aprotic solvent.

A compound of formula (X) is prepared, as illustrated in Step E of Scheme 6, by hydrolyzing the compound of formula (XV) with a base in a protogenic organic solvent or an aqueous mixture thereof. Preferably, the base is either hydrazine or methylamine.
All references cited herein, whether in print, electronic, computer readable storage media or other form, are expressly incorporated by reference in their entirety, including but not limited to, abstracts, articles, journals, publications, texts, treatises, internet web sites, databases, patents, and patent publications.
EXAMPLES
The compounds and processes of the present invention will be better understood in connection with the following examples, which are intended as an illustration only and not limiting of the scope of the invention. Various changes and modifications to the disclosed embodiments will be apparent to those skilled in the art and such changes and modifications including, without limitation, those relating to the chemical structures, substituents, derivatives, formulations and/or methods of the invention may be made without departing from the spirit of the invention and the scope of the appended claims.
Example 1
Preparation of O-Bis(Boc)-2-Methylene-1,3-Propanediol (Compound of Formula II wherein R11 is Hydrogen and R1 is Tert-butyl)
To a solution of di-tert-butyl dicarbonate (6.6 kg) in methylene chloride (15.0 L, 15 volumes) was added 2-methylene-1,3-propanediol (1.00 kg) and phase transfer catalyst tetrabutylammonium hydrogensulfate (0.641 kg). The resulting reaction mixture was then agitated vigorously at about 15° C. while adding over a 2 hr period, 6M aqueous sodium hydroxide solution (13.2 L) and controlling the temperature between 25 to 30° C. The resulting two-phase reaction mixture was subsequently agitated for a period of 2-3 hrs at 25° C.
The aqueous layer was discarded and additional phase transfer catalyst tetrabutylammonium hydrogensulfate (0.064 kg, 10% of the initial amount), di-tert-butyl dicarbonate (0.66 kg, 10% of the initial amount), and methylene chloride (2.0 L, 2 volumes) was added to the remaining organic reaction mixture. To the reaction mixture was also added 6M aqueous sodium hydroxide solution (1.32 L, 10% of the initial amount) over a period of about 0.5 to 1 hr, while controlling the temperature between 25 to 30° C. The resulting two-phase reaction mixture was then agitated at about 25° C. for additional 3 to 4 hr. Allowing more than 3 hrs of agitation time is often required to complete the hydrolysis of the excess di-tert-butyl dicarbonate. The aqueous layer was discarded. The resulting organic phase was washed with water (3×8.0 L), diluted with EtOAc (6 L, 6 volumes), and distilled to an oil foam with quantitative yield.
1H (500 MHz, CDCl3) δ 5.15, 4.98, 4.79, 4.68, 4.68, 4.33, 4.31, 3.89, 3.77, 3.67, 3.45, 3.35, 3.19, 2.88, 2.78, 2.74, 2.42, 2.17, 2.11, 2.06, 1.95, 1.72, 1.66, 1.51, 1.48, 1.43, 1.34, 1.27, 1.19, 1.19, 1.18, 1.14, 1.13, 1.11, 0.95, 0.85.
Example 2
Preparation of Erythromycin A 9-oxime 9,2′,4′′-triacetate (Compound of Formula (I-c))
To a solution of erythromycin A oxime (1.0 kg) in EtOAc (4 L, 4 volumes) was added TEA (0.744 L) and DMAP (48.9 g). While agitating and maintaining a temperature of less than 40° C., to the resulting reaction mixture was added acetic anhydride (0.441 L) over a period of 1-5 hrs. The reaction mixture was then agitated for an additional 1-5 hr period at about 25° C. Additional TEA (0.0744 L, 10% of initial amount) was then added to the reaction mixture, and subsequently additional acetic anhydride (0.0441 L, 10% of initial amount) was added over the course of 30 min while maintaining a temperature of less than 35° C. This mixture was then further agitated for 1.5-2 hr at about 25° C. After the reaction had gone to completion, the reaction mixture was diluted with EtOAc (6 volumes), quenched with aqueous NaHCO3 solution 3.0 L (3 volumes), and agitated for 5-10 min at about 25° C. The aqueous phase was then discarded. The remaining organic mixture was washed with aqueous NaHCO3 solution (3.0 L, 3 volumes) and 15% aqueous brine (3.0 L, 3 volumes), and concentrated in vacuo. The concentrated solution was then taken up in acetonitrile (4.0 L, 4 volumes) and concentrated in vacuo two times until crystallization occurs. Upon formation of crystals, the slurry was agitated at 10° C. to 15° C. for at least 2 hr and the crystals were collected and dried under vacuum to afford white crystalline product with a typical yield of 70-80%.
1H (500 MHz, CDCl3) δ 5.15, 4.98, 4.79, 4.68, 4.68, 4.33, 4.31, 3.89, 3.77, 3.67, 3.45, 3.35, 3.19, 2.88, 2.78, 2.74, 2.42, 2.17, 2.11, 2.06, 1.95, 1.72, 1.66, 1.51, 1.48, 1.43, 1.34, 1.27, 1.19, 1.19, 1.18, 1.14, 1.13, 1.11, 0.95, 0.85 13C (125 MHz, CDCl3) δ 178.7, 175.4, 170.4, 170.0, 168.3, 100.6, 96.3, 83.4, 79.4, 79.0, 77.4, 74.9, 74.0, 72.6, 72.2, 70.1, 67.7, 63.6, 63.4, 49.5, 45.0, 40.7, 39.2, 37.4, 35.7, 34.5, 31.5, 28.6, 26.8, 21.8, 21.7, 21.5, 21.3, 21.1, 20.0, 18.7, 18.4, 16.7, 16.1, 14.9, 10.9, 9.2.
Example 3
Preparation of 6,11-O,O-Bridged Erythromycin A 9-Oxime 9,2′,4′′-triacetate (Compound of Formula (III-c))
To a solution of the title compound of Example 2 (1.00 kg) in anhydrous THF (5.0 L, 5 volumes) was added a solution of the title compound of Example 1 (0.62 kg) in anhydrous THF (2.0 L, 2 volumes) while agitating. The resulting reaction mixture was subsequently degassed twice by application under reduced pressure and placed under nitrogen. To the degassed reaction mixture was added 1,4-bis(diphenylphosphino)butane (dppb) (19.5 g), and tris(dibenzylideneacetone)dipalladium(0) [Pd2(dba)3] (20.8 g), after which the resulting reaction mixture was immediately degassed twice as previously described.
The degassed reaction mixture was then heated, while being agitated, to reflux [typically, reflux begins at about 65° C.] over the period of about 1 to 2 hrs and then held at a temperature of 67° C. to 69° C., while being agitated, for a period of 6 hr. After the 6 hr period, the reaction mixture was allowed to cool to about 25° C. over the period of 2 to 3 hrs and the reaction mixture was analyzed for completion by HPLC.
Once it had been determined that the reaction had gone to completion, the reaction was then filtered through a short pad (about 2 inches thick) of silica gel 0.25-0.5 kg to remove the palladium catalyst, phosphine ligand, and other polar impurities. The reaction vessel was then rinsed with reagent-grade THF (2.0 L, 2 volumes), agitate/wash for 10 min, and filtered through the short pad of silica gel, combining with filtrate from the reaction mixture. The combined filtrate was then concentrated in vacuo to afford the title compound in THF solution. The final remaining volume of the THF solution of the title compound was approximately 2-3 L (2-3 volumes) and was used directly in the following step without isolation.
Example 4
Preparation of 3-Decladinose-6,11-O,O-Bridged Erythromycin A 9-Oxime (Compound of Formula (IV-c))
To the concentrated solution of the title compound of Example 3 was added 1M hydrochloric acid solution in water (8.0 L, 8 volumes). The resulting reaction mixture was subsequently agitated and heated to 60° C. over a period of 1-2 hr and then held at said temperature for an additional 2 hr.
After the reaction had gone to completion (determined by HPLC), the reaction mixture was cooled to about 25° C. over the period of about 3 hrs. The aqueous reaction mixture was then washed with methyl tert-butyl ether (MTBE) (4.0 L×2, 4 volumes×2) while agitating at 25° C. for 10 min, keeping the aqueous layer. To the aqueous reaction mixture was then added saturated aqueous K2CO3 solution (about 0.8 kg of solid potassium carbonate in water) at 20 to 30° C. over the period of 1 to 2 hrs until the mixture is pH 9.5.
The resulting aqueous reaction mixture was then extracted EtOAc (4.0 L×2, 4 volumes×2) while agitating at 25° C. for 10 min, keeping the upper organic layer. The combined organic phase was then washed with water (4.0 L, 4 volumes) and subsequently concentrated in vacuo to a volume of 2-2.5 L. To the concentrated solution was added acetonitrile (4.0 L, 4 volumes) and concentrated in vacuo again until about 2 to 2.5 L (2 to 2.5 volumes) remained. Once again, to the concentrated solution was added acetonitrile (2.0 L, 2 volumes) and concentrate in vacuo until less than 2 L (<2 volumes) remains.
The concentrated solution was removed from reduced pressure and agitated the at 45° C. until crystallization began. The resulting slurry was then cooled to a temperature of 0-5° C. over a period of 4-5 hr and held at said temperature for an additional 2 hrs prior to collecting, washing, and drying the crystalline form of the title compound. The typical yield for this two-step one pot process (Pd-catalyzed bridge formation and sugar cleavage) is 40-45%.
1H (500 MHz, CDCl3) δ 5.09, 4.98, 4.97, 4.78, 4.74, 4.43, 4.39, 4.07, 3.90, 3.84, 3.74, 3.67, 3.50, 3.43, 2.82, 2.79, 2.73, 2.62, 2.43, 2.31, 2.08, 2.03, 1.77, 1.59, 1.46, 1.38, 1.35, 1.32, 1.24, 1.23, 1.22, 1.22, 0.97, 0.97, 0.89 13C (125 MHz, CDCl3) δ 175.3, 170.2, 166.5, 143.7, 119.2, 99.7, 82.3, 79.5, 78.2, 78.1, 77.6, 77.3, 77.0, 76.1, 74.0, 71.7, 69.0, 65.6, 63.4, 43.9, 40.9, 37.5, 36.0, 34.3, 31.2, 25.7, 23.4, 21.7, 21.4, 20.0, 19.6, 17.11, 15.7, 14.8, 12.0, 7.9.
Example 5
Preparation of 3-Decladinose-6,11-O,O-Bridged Erythromycin A 9-Imine Acetamide 2′-Acetate (Compound of Formula (VI-b))
Step 5a. Preparation of 3-Decladinose-6,11-O,O-Bridzed Erythromycin A 9-Imine Acetamide 2′-Acetate (Compound of Formula (V))
To an agitating solution of the title compound of Example 4 (1.00 kg) in ethanol (2 L, 2 volumes) was added 20% titanium (III) chloride solution in aqueous 3% hydrochloric acid (2.847 kg or 2.33 L) over the period of about 1 hr via an addition funnel, while adjusting the addition rate to control maintain the temperature between 25 to 35° C. After adding all of the titanium(III) chloride solution, the reaction mixture was then agitated for an additional 3 hrs at a temperature between 25° C. and 30° C. until the reaction was completed (by HPLC). To the reaction mixture was then added pre-chilled purified water (15 L, 15 volumes).
To the resulting aqueous reaction mixture was added a solution of sodium hydroxide (50%, w/w, 0.466 L) over a period of 0.5-1 hr, while adjusting the addition rate to maintain a temperature between 25 to 35° C., until the reaction mixture had reached a pH of between 6 to 7. The reaction mixture was then treated with saturated aqueous potassium carbonate solution (0.666 L) at 25 to 35° C. over a period of 1 to 2 hrs until the resulting reaction mixture was pH 9 to 10.
The basic aqueous reaction mixture was then extracted five times with methylene chloride (5.0 L×5, 5 volumes×5) and the combined organic extract is concentrated in vacuo until about 5 L remain. To the concentrated reaction mixture was then added additional methylene chloride (5.0 L) and removed in vacuo to azeotropically remove water until about 5 L remain. The resulting methylene chloride solution was directly used in the subsequent step without isolation.
Step 5b. Preparation of the 9-Imine Acetate (Compound of Formula (VI-b)).
Acetic anhydride (0.30 kg) is added to the concentrated solution from Step 5a and the resulting mixture was agitated at 25 to 30° C. for 1.5 hrs. After the acetylation reaction had gone to completion as evidenced by HPLC, the reaction mixture was concentrated in vacuo until approximately 2 L remained in the vessel. The remaining solution was then diluted with EtOAc (4.0 L, 4 volumes) and concentrated in vacuo until about 3 L remain. An additional amount of EtOAc (4.0 L, 4 volumes) was added to the concentrate and the diluted solution was concentrated once again in vacuo until crystallization began (about 1.5 L remaining). To the remaining slurry was added n-hexane (1.5 L, 1.5 volumes) while maintaining the temperature of the solution at about 45° C. After the addition of n-hexanes was complete, cool the solution to 0 to 5° C. over the period of about 3 hr and agitate the resulting slurry at this temperature for at least 2 hr before filtration. The crystals were then filtered and washed with chilled (<5° C.) ethyl acetate/hexane (1:2) (0.3 L, 0.3 volume). The collected crystals of the title compound were then dried under a vacuum at a temperature of about 40-45° C. until a constant weight was observed. The typical yield for this two-step one pot process (reduction and acetylation) is 80-89%.
1H (500 MHz, CDCl3) δ 5.18, 4.93, 4.75, 4.74, 4.59, 4.52, 4.13, 1.08, 3.74, 3.60, 3.48, 3.43, 2.84, 2.73, 2.72, 2.66, 2.55, 2.43, 2.26, 2.02, 1.73, 1.69, 1.46, 1.39, 1.33, 1.31, 1.26, 1.23, 1.23, 1.23, 1.10, 0.97, 0.91 13C (125 MHz, CDCl3) δ 184.9, 178.0, 174.9, 170.1, 142.1, 122.4, 99.8, 81.6, 79.1, 78.2, 77.5, 77.3, 77.0, 76.3, 76.2, 73.8, 71.9, 69.1, 65.9, 63.4, 43.8, 40.9, 40.0, 38.4, 36.3, 35.7, 31.1, 25.7, 23.3, 21.7, 21.4, 20.0, 19.7, 17.2, 16.0, 14.7, 12.0, 7.9.
Example 6
Preparation of 6,11-O,O-Bridged Ketone Erythromycin A 9-Imine Acetamide 2′-Acetate 3-ketolide (Compound of Formula (VIII-b))
Step 6a. Preparation of 3-Descladinose-6,11-Bridged Ketone Erythromycin A 9-Imine Acetamide 2′-Acetate (Compound of Formula VII-b)
To a solution of compound from step 5b of example 5 (20 g) in 200 mL of ethyl acetate/MeOH (10:1) was added MeSO3H (2 mL, 1.1 eq.). The mixture was then cooled down to −55° C. and white suspension resulted. The mixture was subjected to 45 min. of O3 from the ozone generator. A light blue color was observed. The solution was passed through with O2 for 15 min. at −55° C. to remove any excess O3. The resulting white suspension was quenched with dimethyl sulfide (2.68 mL, 1.3 eq.) and the reaction mixture was slowly warmed up to room temperature. At room temperature, the solution was homogenous. The mixture was quenched with saturated aqueous sodium bicarbonate (120 mL), further agitated and the organic layer was separated. The aqueous layer was further extracted with 60 mL ethyl acetate. The combined organic extracts were washed with 60 mL of brine, dried (Na2SO4), filtered and rotavaped to dryness to afford 16.3 g of an amorphous white solid (82%). MS(ESI): m/e 713.75 (M+H). 13C (125 MHz, CDCl3) δ 205.5, 184.2, 175.5, 175.2, 169.8, 99.6, 81.9, 80.3, 79.7, 78.3, 77.6, 76.7, 75.8, 71.7, 69.3, 68.9, 63.2, 44.0, 40.9, 39.1, 38.5, 36.3, 36.1, 30.9, 25.3, 22.9, 21.6, 21.4, 19.8, 19.3, 17.1, 15.6, 14.8, 11.4, 7.9.
Step 6b. Corey-Kim Reaction to Prepare the Title Compound of Formula (VIII-b).
A solution of N-chlorosuccinimide (NCS) (0.197 kg) in methylene chloride (3.5 L, 3.5 volumes) was agitated and cooled to a temperature of approximately −15° C. To the cooled solution was added dimethyl sulfide (0.145 L) over a period of 30 min via an addition funnel while controlling the reaction temperature to about −15° C. After maintaining a temperature of −15° C. for 15 min., the solution was further cooled to a temperature of approximately −20° C. and to this cooled solution was added the methylene chloride/toluene solution of the olefin cleavage intermediate solution prepared in Step 6a (1 Kg) while maintaining a reaction temperature of approximately −20° C. The reaction mixture was agitated for an additional 3 hrs at a temperature of approximately −20° C., after which triethylamine (TEA) (0.196 L) was gradually added over a period of about 30 min. During the addition of TEA, the reaction mixture was maintained at −15° C. by controlling the rate of addition. The resulting reaction mixture was then agitated at the temperature of −15° C. for an additional 1 hr, after which the reaction mixture was warmed to 10° C. and diluted with EtOAc (16 L, 16 volumes). The diluted reaction mixture was then washed with saturated aqueous sodium bicarbonate solution (5 L×2, 5 volumes) and half-saturated aqueous sodium chloride solution (5 L, 5 volumes). The remaining organic solution was then concentrated in vacuo at a temperature range of 45° C. to 50° C. until 1.5 L remain. To the concentrated solution is added ethanol (2.5 L, 2.5 volumes) while continuing to concentrate the organic solution in vacuo until crystallization begins. The concentrated solution was then cooled gradually to a temperature of 0° C. for a period of at least 2 hrs. The crystalline title compound was then collected, washed with chilled (about 0° C.) ethanol (0.15 L), and dried at 25° C. under reduced pressure. The typical yield for this two-step one pot process (oxidative cleavage and Corey-Kim oxidation) is 55-60%.
1H (500 MHz, CDCl3) δ 4.93, 4.78, 4.63, 4.53, 4.41, 4.34, 4.24, 4.00, 3.95, 3.65, 3.56, 3.44, 2.87, 2.83, 2.67, 2.64, 2.36, 2.08, 2.07, 1.84, 1.79, 1.57, 1.49, 1.38, 1.35, 1.33, 1.32, 1.29, 1.28, 1.27, 1.17, 0.92 13C (125 MHz, CDCl3) δ 205.5, 205.2, 184.5, 175.8, 170.2, 169.7, 100.0, 80.2, 79.0, 78.9, 77.6, 76.1, 75.8, 74.6, 71.6, 69.3, 68.7, 63.5, 58.4, 51.0, 45.4, 40.8, 39.7, 38.7, 36.6, 30.8, 25.5, 23.1, 21.6, 21.2, 20.0, 19.6, 18.6, 17.2, 15.5, 14.2, 13.0, 11.6
Example 7
Preparation of 1-(2-aminobenzofdloxazol-5-yl)-hydroxylamine (Compound of Formula (X))
Step 7a. Pd-C (10% weight,  ̃130 g) was placed in a reactor under N2. A solution of compound 2 (1.32 Kg, 7.804 mol) in MeOH (16 L) was added under N2. HCOONH4 (2.6 Kg, 41.2 mol) was added in one portion. The reaction mixture was stirred, and the reaction temperature initially changed from 17° C. to 12° C. then rose gradually up to 28° C. The reaction temperature was controlled at 25-29° C. by setting the cooling jacket at 20° C. After 24 h, NMR indicated the reaction was completed. Nitrogen was bubbled into the reaction mixture to remove any remaining hydrogen. The mixture was filtered through celite, washed with MeOH (7 L). The combined filtrates (25 L) were immediately concentrated in vacuum to almost dryness, co-evaporated with MeOH (6 L) to almost dryness. The residue was used directly in next stage.
Step 7b. A mixture of the compound from Step 7a and anhydrous MeOH (14 L) was placed in a reactor. Solid BrCN (0.937 Kg, 8.6 mol) was added (over 45 min) at such a rate that the internal temperature did no exceed 30° C. The reaction mixture was stirred at room temperature for 14 h. HPLC indicated the completion of reaction. The mixture was concentrated in vacuum at 40° C. to a total volume about 13 L (4 L of methanol was removed). EtOAc (20 L) was added and followed by slow addition of an aqueous K2CO3 (w/w 20%, ca. 1 Kg in 4 L of water) at 14 to 20° C. The mixture's pH value is ca. 9. Water (7 L) was added, and the mixture was stirred for 15 min (aqueous phase pH 9 ̃10). After extraction, the aqueous phase was further extracted with EtOAc (3×18 L). The combined organic layers were washed with half saturated aqueous NaCl (15 L) and concentrated to almost dryness, co-evaporated with MeOH (8 L) to almost dryness. The residue was dissolved in hot MeOH (4 L) at 80° C. bath. The solution gradually cooled to room temperature (crystallization began), then to 0° C. over 3 h. The mixture was stirred at 0° C. for an additional hour, filtered, washed with cold MeOH (100 ml). The collected beige solid (compound 3 was dried in vacuum at 40° C. for 27 h. Weight: 0.706 Kg, HPLC 97.1%. The mother liquid was further crystallized to afford more of the desired compound (0.21 Kg).
MS(ESI): m/e 165.10 (M+H).
C13 (DMSO-d6): 63.10, 107.59, 113.52, 118.36, 137.95, 143.45, 146.81,162.86.
Step 7c. Compound from Step 7b (0.77 Kg, 4.69 mol) was placed in a dry reactor under N2. Anhydrous DMF (4 L) was added and the resulting solution was stirred and cooled to 0° C. by setting the cooling jacket at −10° C. Thionyl chloride (370 ml, 5.07 mol) was added slowly while the internal reaction temperature was controlled at 0 to 3° C. during the addition. After the addition was completed, the reaction mixture was stirred at 0° C. for 3 h. HPLC indicated the reaction was completed (the product 93%). Added slowly 0.55 L of an aqueous K2CO3 (1.5 Kg in 10 L of water) while the temperature did not exceed 5° C. ETOAc (8 L) was added, followed by slow addition of the remaining portion of aqueous K2CO3 (the mixture's pH: 8) over 0.5 h. EtOAc (24 L) was added, the mixture was stirred for 10-15 min. The separated lower aqueous phase (pH 8 to 9) was further extracted with EtOAc (2×11 L). The combined organic layers were washed with saturated aqueous NaHCO3 (4×7 L) and half saturated aq. NaCl (7 L), concentrated in vacuo to almost dryness, co-evaporated with CH3CN (4 L) to dryness to afford the desired chlorinated product (0.739 Kg, 86% yield, HPLC purity >95%), which is pure enough for next step. Purer sample can be obtained by crystallization in acetonitrile.
MS(ESI): m/e 183.05 (M+H). C13 (DMSO-d6): 46.85, 108.20, 115.72, 120.95, 133.03, 143.86, 147.78, 163.28.
Step 7d. To the compound from Step 7c (0.633 Kg, 3.46 mol) was added CH3CN (8 L). The mixture was stirred at 50° C for 1 h, insoluble impurities were filtered off. The filtrate was added to N-hydroxysuccinimide (0.61 Kg, 5.3 mol) in a flask. The resulting solution was cooled to 15° C., diisopropylethylamine (1.1 L, 6.2 mol) was added slowly over 15 min. The resulting mixture was stirred at 50° C. until HPLC indicated the completion of reaction (at least 6 h). The reaction mixture was cooled to room temperature. The mixture was stirred at 0° C. for at least 2 h, filtered, washed with pre-chilled CH3CN (250 ml). The collected beige solid was further dried in vacuum at 40° C. for 24 h to afford EP-014723 (0.711 Kg, 79% yield, HPLC purity >95%). The material can be further purified by re-crystallization from MeOH to give the sample with HPLC purity >99%.
MS(ESI): m/e 262.13 (M+H). C13 (DMSO-d6): 26.14, 78.99, 108.82, 117.26, 122.49, 130.29, 144.49, 149.05, 163.96, 172.76.
Step 7e. Compound from Step 7d (0.821 Kg, 3.14 mol) was dissolved in methanol (16.5 L, 20 volumes). To this solution was added a solution of 33% wt MeNH2 in ethanol (2.50 L, 6.3 eq.). The homogeneous mixture was heated to 64° C. for 5 hours and then it was cooled to room temperature. The excess solvents were rotavaped off to a quarter of its volume and then it was recharged with 3 vols of methanol and then it was evaporated to dryness. The resulting solid was vacuum dried at room temperature overnight to give 0.980 Kg of the title compound which was directly used in the next step without further purification.
Example 8
Preparation of Compound of Formula (IX-a)
Step 8a. Oxime Formation Step
To a −10° C. cooled solution of the 1-(2-aminobenzo[d]oxazol-5-yl)-hydroxylamine (compound of formula (X)) from Step 7e of Example 7 (3.14 mol, 1.18 eq.) in ethanol (5.35 L, 2.8 volumes) was added 1.5 M aqueous hydrochloric acid (5.35 L, 2.8 volumes, 3.0 eq.) while maintaining a temperature below 25° C. by controlling the rate of addition. The resulting reaction mixture was then cooled to a temperature between 0 to 1° C. To the cooled reaction mixture was added the title compound of Example 6 (1.90 kg) while maintaining a reaction temperature less than 1° C. After the addition had been completed, the reaction mixture was agitated for a period of 1 hr. The mixture was warmed to 15° C. and the reaction mixture was subsequently diluted with EtOAc (10 volumes) and to this diluted reaction mixture was added saturated aqueous sodium bicarbonate solution (8.5 volumes) at a temperature below 25° C. until the pH of the mixture was between 8 and 9. The biphasic solution was agitated at 23° C. for 10 min before the organic layer was separated from the aqueous phase. The aqueous layer was further extracted with additional EtOAc (5 volumes). The combined organic extracts were then washed with brine (6 volumes), dried (Na2SO4), filtered and then concentrated in vacuo until only a sticky oil residue remains. This residue was subsequent crystallized in methanol (11 volumes to the diketone starting material Example 6) to give 1.9 Kg of the desired product as a wet cake (purity 91-93% by HPLC). MS(ESI): m/e 872.82 (M+H). 13C (125 MHz, CDCl3) δ 205.6, 184.5, 177.7, 169.8, 167.4, 162.2, 152.9, 148.2, 142.7, 133.7, 121.8, 116.8, 108.6, 100.7, 79.3, 78.6, 76.5, 76.3, 74.8, 74.7, 71.7, 69.4, 63.7, 63.3, 62.9, 50.9, 45.7, 40.9, 40.3, 38.7, 37.5, 30.9, 25.3, 23.7, 21.6, 21.2, 20.3, 19.6, 17.8, 15.1, 13.9, 13.4, 13.0.
Step 8b. 2′ Deprotection
To the wet cake from Step 8a was added methanol (8.0 L) and the resulting mixture was rotated in a rotavap at 35° C. for approximately 19 hours after which the deacetylation reaction was complete as evidenced by HPLC. The reaction mixture was then concentrated in vacuo until approximately 2.0 L remained. The suspension was cooled to 0° C. and held at that temperature for 30 min. The solid was filtered off and rinsed with cold methanol (50 mL). The mother liquor still contained 70% of the E isomer and 14% of the Z isomer. The solid was vacuum dried at 30° C. overnight to give 0.915 Kg of the product. The residue was then dissolved with ethyl acetate (4.0 L, 4.5 volumes) in a 65-70° C. bath. To this solution was added slowly hexanes (6 L, 6.6 volumes) while maintaining a temperature of approximately 65° C. Fine crystals crashed out. The mixture was cooled to 20 C and held at that temperature for 2 hours. The solid was filtered off and washed with ethyl acetate/hexanes. The wet solid was dried in a vacuum oven at 30 C for 3 hours and at 25° C. for 24 hours to give 0.735 Kg of the title compound. MS(ESI): m/e 830.41 (M+H). 13C (125 MHz, CDCl3) δ 205.6, 184.4, 177.5, 167.6, 162.2, 153.1, 148.2, 142.7, 133.8, 121.8, 116.8, 108.6, 103.0, 79.3, 78.6, 76.5, 76.3, 75.6, 74.7, 70.4, 69.7, 66.0, 63.1, 62.9, 50.7, 46.2, 40.5, 40.3, 38.7, 37.2, 28.5, 25.3, 23.7, 21.5, 20.5, 19.6, 17.8, 15.1, 13.9, 13.8, 12.7.
Example 9
Alternative Preparation of O-(2-aminobenzo[d]oxazolyl-5-methyl)-hydroxylamine (Compound of Formula (X))
Step 9a. To a solution of 2-amino-4-methylphenol (2-amino-p-cresol, Mol. Wt.: 123.15, 157.6 g, 1.28 mol) in 1500 ml of EtOH at room temperature, under stirred condition, was added bromocyanogen (Mol. Wt.: 105.92, 135.00 g, 1.28 mol) in about 30 mins. During the addition, the reaction mixture became to warm and water bath was used to cool the reaction to room temperature. The reaction color became to a dark color. After 5-6 hours, the reaction solvent was evaporated under reduced pressure. The residue was dissolved in about 1500 ml of EtOAc and washed with the saturated 1500 ml NaHCO3, the gas of CO2 was generated, and water phase was separated and washed again by 400 ml of EtOAc. The organic layer was combined and dried over anhydrous MgSO4. Removal of solvent and dried by high vacuum yielded about 150 g of product 2 as pale brown color, which can be used in next step. The TLC RF value of the product is about 0.35 in solution of acetone and hexane by the ratio of 1 to 2. MS(ESI): m/e 149 (M+H), 1H NMR (CDCl3) (ppm): 2.21 (s, 3H); 5.30 (bs, 2H); 6.99 (d, 1H); 7.10 (s, 1H); 7.22 (d, 2H).
Step 9b. In 2500 ml of anhydrous toluene, succinic anhydride (Mol. Wt.: 100.07, 141.1 g, 1.41 mol) and 70 g (about 0.47 mol) of compound from Step 9a were added under stirred condition, and then the mixture was refluxed for overnight. After that, 100 g (0.26 mol) of HATU and 41.36 ml (0.376 mol) of 4-methylpholine were added and then the resulting mixture was refluxed for 2-3 hours. TLC showed that the major spot was product and its TLC RF value is about 0.45 in solution of acetone and hexane by the ratio of 1 to 2. After reaction was completed, the solvent was evaporated and the residues was dissolved in about 2000 ml of CH2Cl2, the solution was treated with aqueous NaHCO3 and CO2 was generated during stirring. After pH was adjusted to be about 7-8 and washed with brine, organic phase was separated and dried over MgSO4. Filtration and removal of solvent gave about 98 g of crude desired product as fine white needle crystalline. MS(ESI): m/e (M+H) 231.
Step 9c. To the 1.5 L of CCl4 under stirring condition, 44.37 g (about 0.193 mol) of compound from Step 9b and 41.16 g (about 0.23 mol) of NBS was added and then the mixture were heated to reflux. 0.15 g of Benzoyl peroxide was added by three times. This suspension mixture became to solution after 17 hours refluxing, and the solid was found on the flask inside. The color of the reaction solution became to red and then turned to yellow. Other of 0.15 g of Benzoyl peroxide was added again after 6 hours. TLC was used to monitor reaction every two-three hours, and the product's RF value was about 0.4 in solution of acetone and hexane by the ratio of 1 to 2. After completion, the reaction was cooled to room temperature and the white solid was formed. The mixture was diluted with 1.5 L of CH2Cl2 until the white solid was disappearing and organic phase was washed with 4 L of saturated NaHCO3 two times to adjusted pH 7-8, dried over MgSO4, filtrated, and removal of the solvent under reduced pressure, dried by high vacuum gave about 57.3 g of the desired product as slight yellow solid. HPLC test at 254 nm indicated that this product was about 77.6% purity. This product can be used for next step without further purification. MS(ESI): m/e (M+H) 309, 311.
Step 9d. To 450 ml of MeCN, 57.3 g (about 0.185 mol) of the compound from Step C was added and heated to about 50° C., under stirring condition 60.51 g (0.371 mol) N-hydroxyphanthalimide and 80 ml of triethylamine were added. The reaction mixture became to deep red color and the solid product was formed after 10-15 mins. The reaction mixture was stirred at room temperature for further 8 hours. After filtration, the pale yellow product was collected, which was washed by 100 ml of MeOH and ether in the 1:1 ratio. After drying by vacuum, about 48 g of the desired product was obtained as pale solid, its HPLC at 254 nm gave the single peak, which is less polar than starting material from Step 9c and TLC showed single spot at about 0.4 RF value in solution of acetone and hexane by the ratio of 1 to 2. MS(ESI): m/e 392.
Step 9e. A solution of the compound from Setp 9d (3.91 g, 10 mmol) in 100 ml 2M ammonia in methanol was stirred at 40° C. for 16 hours. The reaction mixture was filtered and the filtrate was concentrated. The residue was purified on silica gel column (CH2Cl2/MeOH ̃10/1) to give the title compound (1.7 g, 95%).
MS(ESI): m/e 180 (M+H).
Although the invention has been described in detail with respect to various preferred embodiments it is not intended to be limited thereto, but rather those skilled in the art will recognize that variations and modifications may be made therein which are within the spirit of the invention and the scope of the appended claims.

## Claims

1. A process for preparing a compound of formula (XI):



Wherein R3 and R4 are hydrogen;
or one of R3 or R4 is a hydrogen and the other is selected from:
(a) C(O)R5, where R5 is C1-C6 alkyl, optionally substituted with one or more substituents selected from aryl, substituted aryl, heteroaryl, or substituted heteroaryl;
(b) C(O)OR5, where R5 is as previously defined; or

R3 and R4 are taken together with the nitrogen atom to which they are attached to form




wherein A and B are each independently hydrogen, a substituted or unsubstituted aliphatic group, a substituted or unsubstituted cyclic group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alicyclic group, or a substituted or unsubstituted heteroaryl group; or A and B taken together with the carbon to which they are attached form a cyclic moiety selected from: aryl, substituted aryl, heterocyclic, substituted heterocyclic, alicyclic, or substituted alicyclic;
alternatively, R3 and R4 are taken together with the nitrogen atom to which they are attached to form N═C(R6)(R7), where R6 and R7 are each independently selected from a substituted or unsubstituted aliphatic group, a substituted or unsubstituted cyclic group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted aryl group,
a substituted or unsubstituted alicyclic group, or a substituted or unsubstituted heteroaryl group;
said process comprising:
(1) reducing 4-(hydroxymethyl)-2-nitrophenol with a reducing agent to provide compound of formula (XII):




(2) reacting cyanogen bromide with compound of formula (XII) in a solvent to give compound of formula (XIII):




(3) halogenating the resulting compound with a chlorinating reagent to provide a compound of formula (XIV);




(4) treating compound of formula (XIV) with a compound of formula R3R4NOH in the presence of base to yield a compound of formula (XI).

2. The Process of claim 1 further comprising the step of hydrolyzing the compound of formula XI with a base or an acid in a protogenic organic solvent or aqueous solution, to yield a compound of formula (X):

3. The process of claim 1, wherein step 1 comprises hydrogenating 4-(hydroxymethyl)-2-nitrophenol with palladium on carbon in the presence of hydrogen gas to provide 2-amino-4-(hydroxymethyl)phenol.

4. The process of claim 1, wherein step 2 comprises treating 2-amino-4-(hydroxymethyl)phenol with cyanogenbromide in methanol to provide (2-aminobenzo[d]oxazol-5-yl)methanol.

5. The process of claim 1, wherein step 3 comprises reacting thionyl chloride with (2-aminobenzo[d]oxazol-5-yl)methanol to provide 5-(chloromethyl)benzo[d]oxazol-2-amine.

6. The process of claim 1, wherein step 4 comprises reacting N-hydroxysuccinimide with 5-(chloromethyl)benzo[d]oxazol-2-amine in the presence of diisopropylethylamine to provide 1-((2-aminobenzo[d]oxazol-5-yl)methoxy)pyrrolidine-2,5-dione.

7. The process of claim 1, wherein step 4 comprises reacting N-hydroxysuccinimide with 5-(chloromethyl)benzo[d]oxazol-2-amine in the presence of DBU to provide 1-((2-aminobenzo[d]oxazol-5-yl)methoxy)pyrrolidine-2,5-dione.

8. The process of claim 2 comprising reacting methylamine with 1-((2-aminobenzo[d]oxazol-5-yl)methoxy)pyrrolidine-2,5-dione in methanol to provide O-(2-aminobenzo[d]oxazol-5-yl)methyl hydroxylamine.

9. The process of claim 2 further comprising the step of adding the compound of formula X to the compound of formula (VIII-a):




with an acid in a protogenic organic solvent or aqueous solution, to yield a compound of formula (IX-b):

10. The Process of claim 9 further comprising the step of deprotecting the compound of formula (IX-b) with a protogenic organic solvent or aqueous solution, to yield a compound of formula (IX-a):