DESCRIPTION

METHOD OF PRODUCING ANTHRAC YCLINE DERIVATIVES

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Polish Application Serial No. P 380561, filed September 5, 2006, which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to the fields of synthetic organic chemistry and anticancer agents. In particular, methods of the present invention provide facile synthetic access to anthracycline derivatives. In addition to acting as antibiotics, anthracyclines are known to show high anti-tumor activity and may be utilized as chemotherapeutics. The methods discussed herein offer regioselective control over functionalizing various positions of anthracyclines. Thus, a diverse range of anthracycline derivatives may be produced using such methods.

2. Description of Related Art

A number of classes of antibiotics and other natural compounds used in chemotherapy are glycosides in which the aglycone displays a complex structure. In the case of anthracycline antibiotics, the aglycone is a system of four condensed rings containing hydroxyl, alkoxy and acyl substituents. Anthracycline antibiotics synthesized by

Actinomycetales {e.g., Streptomycae), for example, contain deoxypyranosyl radicals of the L- configuration. 3-Amino-2,3,6-trideoxy-L-pyranose is most frequently joined to the aglycone with an O-glycoside bond (e.g., daunosamine, acosamine, ristosamine).

In the group of anthracycline antibiotics, new compounds in clinical trials are prepared most frequently from efforts in which the tetracyclic system and the sugar unit are obtained in a multistage total synthesis. A key step in this production method is the formation of a glycosidic bond. This approach permits, for example, obtaining new analogs of anthracycline antibiotics and new drug candidates. See, e.g., Grynkiewicz et al, 2002, and the references cited therein.

Regarding manipulation of the sugar moiety of natural anthracyclines, there is a paucity of literature precedent regarding efficient, regioselective control of amino and hydroxy substitutions. For example, the complex structure of these compounds, their sensitivity to the action of acids and bases and the presence of several hydroxy groups in the molecules make controlled synthetic manipulations difficult. Protecting groups are often employed by skilled artisans in efforts to selectively modify certain anthracycline substituents, such as installation of amino protecting groups to allow functionalization of a hydroxy group. However, such efforts are often difficult and are frequently met with disappointing results, particular with respect to O-alkylation reactions. For example, in 1981, Cassinelli et al. reported alkylation attempts of the C-4' hydroxy group of the sugar moiety of two different amino-protected anthracyclines. In both reactions, mixtures of alkylated products resulted, wherein one product was mono-alkylated and the other product was bis- alkylated. Indeed, in one method, the target C-4' hydroxy group was not alkylated at all. In general, outcomes of previous attempts to manipulate substituents of anthracycline sugars have been discouraging.

SUMMARY OF THE INVENTION

The present invention generally provides methods of obtaining anthracycline derivatives. In general, these methods permit manipulation of select functional groups without the disturbance of other portions of the molecule. In particular embodiments, functional groups on the sugar moiety of an anthracycline may be specifically manipulated. Methods described herein permit, in certain embodiments, regioselective functionalization of hydroxy groups of anthracyclines, such as alkylation of a C-4' hydroxy group of the sugar ring. Protection of a C-3 ' amino group of the sugar ring is also encompassed by the present invention, and can facilitate later hydroxy alkylation. These methods also offer benefits over prior synthetic attempts to generate anthracycline derivatives by, for example, avoiding undesired hydroxy alkylations and multistage, total syntheses of entire anthracycline structures. Moreover, the methods are more economical than, for example, total syntheses. The anthracyclines produced via the methods described herein, including any intermediates formed, may find use as antibiotics, DNA intercalating agents, and/or anticancer agents and methods relating thereto.

Accordingly, in certain embodiments, the present invention contemplates a method of synthesizing a product anthracycline compound comprising: protecting the C-3' amino group

of a first anthracycline via an amide or carbamate, wherein the first anthracycline comprises a C-3' amino group and a C-4' hydroxy group; alkylating the C-4' hydroxy group in the presence of an alkylating agent and a chlorinated hydrocarbon solvent; and obtaining a product anthracycline. The first anthracycline can be any anthracycline known to those of skill in the art. In certain embodiments, the first anthracycline is daunorubicin. A variety of protecting groups may be employed to protect the C-3' amino group and agents used to install such groups are well-known to those of skill in the art, as described below. In certain embodiments, the C-3' amino group is protected by a trifluoroacetyl, trichloroacetyl, chloroacetyl, benzyloxycarbonyl, allyloxycarbonyl, or butoxycarbonyl protecting group. Alkylating agents are well-known to those of skill in the art. In certain embodiments, the alkylating agent is a benzyl halide, such as benzyl chloride, benzyl iodide, or benzyl bromide. In certain embodiments, the alkylating agent is an alkyl or aryl sulfonate, such as methanesulfonate, trifluoromethanesulfonate, benzenesulfonate, 4-methylbenzenesulfonate, or 4-nitrobenzenesulfonate. In certain embodiments, the alkylating agent is a benzyl sulfate or a benzyl phosphate.

In certain methods of the present invention, the alkylation step may take place in the presence of a base. A base may be, for example, a metal hydride, such as sodium hydride, potassium hydride, or calcium hydride. The base may be a non-nucleophilic organic base, examples of which are well-known to those of skill in the art. In particular embodiments, the non-nucleophilic organic base is DBU.

A variety of solvents may be used in certain methods of the present invention. In certain embodiments, a chlorinated hydrocarbon solvent is employed, such as in the alkylation step. The chlorinated hydrocarbon solvent may be, for example, dichloromethane or 1,2-dichloroethane. Other solvents that may be employed in the alkylation step include DMF, DMSO, N-methylpyrrolidone, HMPA, or acetonitrile.

In certain embodiments, the first anthracycline comprises a -C(O)CH ₃ group at the C- 9 position of the anthracycline. This -C(O)CH3 group may be further manipulated in certain methods of the present invention. For example, the -C(O)CH3 group may be converted to a - C(O)CH ₂ OH group via, e.g., bromination and then hydrolysis. An anthracycline that comprises a C-3' amino group that becomes protected and a C-

4' hydroxy group that becomes alkylated in the methods described herein may undergo further reaction in order to produce a product anthracycline of interest. For example, methods of the present invention may further comprise deblocking the C-3 ' amide or carbamate. Other substituents may then be introduced at the C-3 ' position, if desired.

A variety of intermediates may be formed during the synthesis of a product anthracycline. In certain embodiments, methods of the present invention may be defined as a process wherein a compound of formula (I) is formed as an intermediate during the synthesis:

wherein:

R ¹ is alkyl, aryl, aralkyl, acyl, alkoxy, or aryloxy; R and R are each independently -H, -OH, or alkoxy; R ⁴ is -H, -OH, alkoxy, or a halide;

Y ¹ and Y ² are each independently a double bonded oxygen, sulfur, or nitrogen atom; Z is a -H, -OH, or acyl;

R ⁵ and R are each independently -H, alkyl, aryl, aralkyl, acyl, alkoxy, aryloxy, or - NR ¹⁹ R ²⁰ , wherein: R ¹⁹ is -H, alkyl, aryl, or aralkyl; and R is an amide or carbamate protecting group, provided that either R ⁵ or R ⁶ is -NR ¹⁹ R ²⁰ ;

R ⁷ and R ⁸ are each independently -H or -OR ²¹ , wherein R ²¹ is -H, alkyl, aryl, or aralkyl, provided that at least one of R ⁷ or R ⁸ is -OR ²¹ ; R ⁹ is -H, alkyl, or aryl; and

R ¹⁰ , R ¹¹ and R ¹² are each independently -H, alkyl, a halide, -OR ²³ , -SR ²³ , -NH ₂ , - NHR ²³ , -N(R ²³ ) ₂ , wherein R ²³ is -H, alkyl, or aralkyl.

Particular, non-limiting examples of compounds that may be formed as an intermediate during a synthesis of the present invention include:

, wherein R forms an amide or carbamate with the

C-3' -NH group.

In certain embodiments, the C-4' hydroxy group of a product anthracycline made via a method of the present invention is a hydroxy group or is alkylated (to form an -OR group). In certain embodiments, the C-3' amino group of the product anthracycline is -NHR ²⁴ ,

wherein R >24 is -H, alkyl, aryl, or aralkyl. A product anthracycline may also be a compound of formula (II):

wherein: R ¹ is alkyl, -COCH ₂ R ¹³ , or -C(OH)-CH ₂ R ¹³ , wherein:

R ¹³ is -H, -OH, alkoxy, alkyl, aryl, -OC(O)(CH ₂ ) _P CH ₃ , wherein p = an integer from 1 to 20, -OC(O)(CH ₂ ) _j (CH=CH) _m (CH ₂ ) _n CH3, wherein j is an integer between 1 and 3, m is an integer between 1 and 6, and n is an integer between 1 and 9, -OC(O)(CH ₂ ) _r CH ₂ NH ₂ , or - OC(O)(CH ₂ ) _r CO ₂ H, wherein r is an integer between 1 and 9;

R and R are each independently -H, -OH, or alkoxy; R ⁴ is -H, -OH, alkoxy, or a halide;

Y ¹ and Y ² are each independently a double bonded oxygen, sulfur, or nitrogen atom; Z is a -H, -OH, or acyl; R ⁹ is -H, alkyl, or aryl;

R ¹⁰ , R ¹¹ and R ¹² are each independently -H, alkyl, a halide, -OR ¹⁹ , -SR ¹⁹ , -NH ₂ , - NHR ¹⁹ , -N(R ¹⁹ ) ₂ , wherein R ¹⁹ is -H, alkyl, or aralkyl; and either: (i) one of R ⁵ and R ⁶ is -H, and one of R ⁵ and R ⁶ is an X-alkyl-aromatic ring (-XAAr) substituent, wherein: X is -N, -S, -SO, or -SO ₂ ;

A is alkyl; and

Ar is a substituted five-member ring, a heteroatomic five- member ring, a heteroatomic six-member ring, or a substituted phenyl ring of the form:

wherein:

R ¹⁴ -R ¹⁸ are each independently -H, -OH, -NO ₂ , -NH ₂ , a halide, an alkoxy group having 1-20 carbon atoms, an alkyl group having 1-20 carbon atoms, an aryl group having 1-20 carbon atoms, an alkylamino group, an alkylthio group, a cyano group, a thiocyano group, or an acyl group; and

A is -(CH ₂ V, wherein t = 0-10; wherein, if R ⁵ is an -XAAr substituent then R is not, and if R is an -XAAr substituent then R ⁵ is not; and R ⁷ and R ⁸ are each independently -H, alkyl, a halide, -OR ¹⁹ , -SR ¹⁹ , -

NH ₂ , -NHR ¹⁹ , -N(R ¹⁹ ) ₂ , or a saccharide, wherein R ¹⁹ is -H, alkyl, or aralkyl; or R ⁷ and R ⁸ are each independently -H, alkyl, a halide, -OR ¹⁹ , -SR ¹⁹ , -

NH ₂ , -NHR ¹⁹ , or -N(R ¹⁹ ) ₂ , wherein R ¹⁹ is -H, alkyl, or aralkyl; and

( ^l i) R ⁵ and R ⁶ are each independently -H, alkyl, a halide, -OR ¹⁹ , -SR ¹⁹ , -

NH ₂ , -NHR ¹⁹ , -N(R ¹⁹ ) ₂ , or a saccharide, wherein R ¹⁹ is -H, alkyl, or aralkyl; one of R ⁷ and R ⁸ is H; and one of R ⁷ and R ⁸ is an X-alkyl-aromatic ring (-XAAr) substituent, wherein:

X is -O, -N, -S, -SO, or -SO ₂ ;

A is alkyl; and

Ar is a substituted five-member ring, a heteroatomic five- member ring, a heteroatomic six-member ring, or a substituted phenyl ring of the form:

wherein:

R ¹⁴ -R ¹⁸ are each independently -H, -OH, -NO ₂ , -NH ₂ , a halide, an alkoxy group having 1-20 carbon atoms, an alkyl group having 1-20 carbon atoms, an aryl group having 1-20 carbon atoms, an alkylamino group, an alkylthio group, a cyano group, a thiocyano group, or an acyl group; and

A is -(CH ₂ V, wherein t = 0-10; wherein, if R ⁷ is an -XAAr substituent then R is not, and if R is an -

XAAr substituent then R ⁷ is not; or R ⁷ and R ⁸ are each independently -H, alkyl, a halide, -OR ¹⁹ , -SR ¹⁹ , -

NH ₂ , -NHR ¹⁹ , or -N(R ¹⁹ ) ₂ , wherein R ¹⁹ is -H, alkyl, or aralkyl.

Particular, non-limiting examples of product anthracyclines that may be produced via methods of the present invention include:

In any method of the present invention, the product anthracycline may be further comprised in a pharmaceutically acceptable composition. Such compositions are described in more detail below. A product anthracycline may be administered or delivered to a target cell, or may be administered to a subject. A product anthracycline may be administered in an amount effective to treat a subject, such as a subject suffering from cancer or a bacterial infection, to produce a therapeutic benefit. A subject may also be susceptible to acquiring a bacterial infection: administration of a product anthracycline may provide a prophylactic therapeutic benefit for such a subject.

The terms "contacted" and "exposed," when applied to a cell, are used herein to describe the process by which a compound of the present invention is administered or delivered to a target cell or are placed in direct juxtaposition with the target cell. The terms "administered" and "delivered" are used interchangeably with "contacted" and "exposed."

As used herein, the term "effective" (e.g., "an effective amount") means adequate to accomplish a desired, expected, or intended result. For example, an "effective amount" may be an amount of a compound sufficient to produce a therapeutic benefit (e.g. , effective to reproducibly inhibit decrease, reduce, inhibit or otherwise abrogate the growth of a cancer cell; or to treat a bacterial infection).

"Treatment" and "treating" as used herein refer to administration or application of a therapeutic agent to a subject or performance of a procedure or modality on a subject for the purpose of obtaining a therapeutic benefit of a disease or health-related condition. For example, a subject (e.g., a mammal, such as a human) having cancer or a bacterial infection may be subjected to a treatment comprising administration of a compound of the present invention.

The term "therapeutic benefit" or "therapeutically effective" as used throughout this application refers to anything that promotes or enhances the well-being of the subject with respect to the medical treatment of a condition. This includes, but is not limited to, a reduction in the onset, frequency, or severity of the signs or symptoms of a disease. For example, a therapeutically effective amount of a compound of the present invention may be administered to a subject having a cancerous tumor, such that the tumor shrinks. A therapeutically effective amount of a compound of the present invention may be admininstered to a subject suffering from a bacterial infection to ameliorate the infection, or may be given to a subject to prevent a bacterial infection.

Pharmaceutical compositions of the present invention comprise an effective amount of one or more candidate substances (e.g., an anthracycline or derivative thereof) or additional agents dissolved or dispersed in a pharmaceutically acceptable carrier. The phrases "pharmaceutical or pharmacologically acceptable" refers to molecular entities and compositions that do not produce an adverse, allergic or other untoward reaction when administered to an animal, such as, for example, a human, as appropriate. The preparation of a pharmaceutical composition that contains at least one candidate substance or additional active ingredient will be known to those of skill in the art in light of the present disclosure, as exemplified by Remington's Pharmaceutical Sciences, 18th Ed. Mack Printing Company, 1990, incorporated herein by reference.

It is specifically contemplated that any limitation discussed with respect to one embodiment of the invention may apply to any other embodiment of the invention. Furthermore, any composition of the invention may be used in any method of the invention, and any method of the invention may be used to produce or to utilize any composition of the invention.

The use of the term "or" in the claims is used to mean "and/or" unless explicitly indicated to refer to alternatives only or the alternative are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and "and/or."

Throughout this application, the term "about" is used to indicate that a value includes the standard deviation of error for the device and/or method being employed to determine the value.

As used herein the specification, "a" or "an" may mean one or more, unless clearly indicated otherwise. As used herein in the claim(s), when used in conjunction with the word "comprising," the words "a" or "an" may mean one or more than one. As used herein "another" may mean at least a second or more.

Other objects, features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention overcomes the deficiencies of the prior art by providing methods that enable facile access to anthracycline derivatives. The present inventors have discovered, for example, how to selectively modify a C-3' amino group of an anthracycline by conversion to, for example, an amide or carbamate derivative, such that certain other positions (particularly positions that are not protected by a protecting group) of the anthracycline are left undisturbed and thus may be further modified. In certain embodiments, the action of substituted carboxylic acid esters (e.g., methyl trifluoroacetate, ethyl trifluoroacetate, or ethyl benzyloxycarbonate) allows corresponding amides to be obtained. Carbamates may also be produced. Moreover, hydroxy positions present in an anthracycline, such as a C-4' hydroxy position of an anthracycline sugar, may be functionalized (e.g., alkylated) in an uncomplicated, selective fashion using methods discovered by the inventors. For example, benzyl bromide in the presence of a chlorinated hydrocarbon solvent, such as dichloromethane, permits selective alkylation of the C-4' hydroxy group in the sugar ring. Such alkylation of the hydroxy group allows for further manipulation of other positions of the anthracycline and allows for rapid preparation of therapeutically useful anthracyclines.

A. Anthracyclines

Anthracyclines have a tetracyclic ring structure to which a sugar moiety is attached via a glycosidic linkage. Cytotoxic agents of this class typically have quinone and

hydroquinone moieties that permit them to function as electron-accepting and electron donating agents. Doxorubicin and daunorubicin are examples of compounds of this class. These compounds act by intercalating with DNA. Non-limiting examples of anthracyclines include daunorubicin, doxorubicin, epirubicin, idarubicin, pyrromycin, aclacinamycine, isorhodomycine, carminomycine, doxorubicine 14-esters (e.g., doxorubicin 14-acetate, doxorubicin 14-propionate, doxorubicin 14-octanoate, doxorubicine 14-benzoate and doxorubicine 14-phenylacetate), 4'-epidaunorubicin, 4'-epidoxorubicin, 4'-iododaunorubicin, 4'-iododoxorubicin, 4'-deoxydaunorubicin, 4'-deoxydoxorubicin, 3'-hydroxydaunorubicin, 3'- hydroxydoxorubicin, 4-demethoxydaunorubicin, 4-demethoxydoxorubicin, 4'-epi-4- demethoxydaunorubicin and 4'-epi-4-demethoxydoxorubicin. Other anthracyclines are known in the art, such as those described in U.S. Patent No. 6,673,907, which is incorporated by reference herein it its entirety. Methods of the present invention can be used in synthetic protocols to access certain of these and other known anthracyclines as well as novel anthracyclines. Moreover, those anthracyclines comprising, for example, a C-4' hydroxy group and a C-3' amine group may be used as synthetic starting materials in certain methods of the present invention. Such starting materials may be obtained by known synthetic methods or by purchase from commerical chemical companies such as Sigma-Aldrich (Milwaukee, WI).

B. Chemical Definitions As used herein, the term "amino" means -NH ₂ ; the term "nitro" means -NO2; the term "halo" or "halide" designates -F, -Cl, -Br or —I; the term "mercapto" or "thiol" means -SH; the term "cyano" means -CN; the term "azido" means -N ₃ ; the term "silyl" means -S1H3, and the term "hydroxy" means -OH.

The term "alkyl" includes straight-chain alkyl, branched-chain alkyl, cycloalkyl (alicyclic), cyclic alkyl, heteroatom-unsubstituted alkyl, heteroatom-substituted alkyl, heteroatom-unsubstituted C _n -alkyl, and heteroatom-substituted C _n -alkyl. In certain embodiments, lower alkyls are contemplated. The term "lower alkyl" refers to alkyls of 1-6 carbon atoms (that is, 1, 2, 3, 4, 5 or 6 carbon atoms). The term "heteroatom-unsubstituted C _n -alkyl" refers to a radical, having a linear or branched, cyclic or acyclic structure, further having no carbon-carbon double or triple bonds, further having a total of n carbon atoms, all of which are nonaromatic, 3 or more hydrogen atoms, and no heteroatoms. For example, a heteroatom-unsubstituted Ci-Cio-alkyl has 1 to 10 carbon atoms. The groups, -CH3 (Me), -CH ₂ CH ₃ (Et), -CH ₂ CH ₂ CH ₃ (n-Pr), -CH(CH ₃ ) ₂ (ώo-Pr), -CH(CH ₂ );. (cyclopropyl),

-CH ₂ CH ₂ CH ₂ CH ₃ (λ-BU), -CH(CH ₃ )CH ₂ CH ₃ (sec-butyl), -CH ₂ CH(CH ₃ ) ₂ (wo-butyl), -C(CH ₃ ) ₃ (ter t-butyl), -CH ₂ C(CH ₃ ) ₃ (neo-psntyl), -cyclobutyl, cyclopentyl, and cyclohexyl, are all non-limiting examples of heteroatom-unsubstituted alkyl groups. Other such non- limiting heteroatom-unsubstituted alkyl group include -CH ₂ -cycloalkyl, such as -CH ₂ - cyclopropyl. The term "heteroatom-substituted C _n -alkyl" refers to a radical, having a single saturated carbon atom as the point of attachment, no carbon-carbon double or triple bonds, further having a linear or branched, cyclic or acyclic structure, further having a total of n carbon atoms, all of which are nonaromatic, 0, 1, or more than one hydrogen atom, at least one heteroatom, wherein each heteroatom is independently selected from the group consisting of N, O, F, Cl, Br, I, Si, P, and S. For example, a heteroatom-substituted Ci-Cio-alkyl has 1 to 10 carbon atoms. The following groups are all non-limiting examples of heteroatom- substituted alkyl groups: trifluoromethyl, -CH ₂ F, -CH ₂ Cl, -CH ₂ Br, -CH ₂ OH, -CH ₂ OCH ₃ , -CH ₂ OCH ₂ CF ₃ , -CH ₂ OC(O)CH ₃ , -CH ₂ NH ₂ , -CH ₂ NHCH ₃ , -CH ₂ N(CH ₃ ) ₂ , -CH ₂ CH ₂ Cl, -CH ₂ CH ₂ OH, CH ₂ CH ₂ OC(O)CH ₃ , -CH ₂ CH ₂ NHCO ₂ C(CH ₃ ) ₃ , -CH ₂ Si(CH ₃ ) ₃ , and -C(OH)- CH ₂ OH.

The term "aryl" includes heteroatom-unsubstituted aryl, heteroatom-substituted aryl, heteroatom-unsubstituted C _n -aryl, heteroatom-substituted C _n -aryl, heteroaryl, heterocyclic aryl groups, carbocyclic aryl groups, biaryl groups, and single-valent radicals derived from polycyclic fused hydrocarbons (PAHs). The term "heteroatom-unsubstituted C _n -aryl" refers to a radical, having a single carbon atom as a point of attachment, wherein the carbon atom is part of an aromatic ring structure containing only carbon atoms, further having a total of n carbon atoms, 5 or more hydrogen atoms, and no heteroatoms. For example, a heteroatom- unsubstituted Cβ-Cio-aryl has 6 to 10 carbon atoms. Non-limiting examples of heteroatom- unsubstituted aryl groups include phenyl (Ph), methylphenyl, (dimethyl)phenyl, -C ₆ H ₄ CH ₂ CH ₃ , -C ₆ H ₄ CH ₂ CH ₂ CH ₃ , -C ₆ H ₄ CH(CH ₃ ) ₂ , -C ₆ H ₄ CH(CH ₂ ) ₂ ,

-C ₆ H ₃ (CH ₃ )CH ₂ CH ₃ , -C ₆ H ₄ CH=CH ₂ , -CgH ₄ CH=CHCH ₃ , -C ₆ H ₄ C=CH, -C ₆ H ₄ C=CCH ₃ , naphthyl, and the radical derived from biphenyl. The term "heteroatom-substituted C _n -aryl" refers to a radical, having either a single aromatic carbon atom or a single aromatic heteroatom as the point of attachment, further having a total of n carbon atoms, at least one hydrogen atom, and at least one heteroatom, further wherein each heteroatom is independently selected from the group consisting of N, O, F, Cl, Br, I, Si, P, and S. For example, a heteroatom-unsubstituted Ci-Cio-heteroaryl has 1 to 10 carbon atoms. Aryl groups may be di-, tri-, terra-, or penta- substituted, for example. Substituents include, but are not limited to, hydroxy, methoxy, nitro, amino, halide, alkoxy, aryl, alkylamino, alkylthio,

cyano, thiocyano, and acyl. Non-limiting examples of heteroatom-substituted aryl groups include the groups: -C ₆ H ₄ F, -C ₆ H ₄ Cl, -C ₆ H ₄ Br, -C ₆ H ₄ I, -C ₆ H ₄ OH, -C ₆ H ₄ OCH ₃ , -C ₆ H ₄ OCH ₂ CH ₃ , -C ₆ H ₄ OC(O)CH ₃ , -C ₆ H ₄ NH ₂ , -C ₆ H ₄ NHCH ₃ , -C ₆ H ₄ N(CH ₃ ) ₂ , -C ₆ H ₄ CH ₂ OH, -C ₆ H ₄ CH ₂ OC(O)CH ₃ , -C ₆ H ₄ CH ₂ NH ₂ , -C ₆ H ₄ CF ₃ , -C ₆ H ₄ CN, -C ₆ H ₄ CHO, -C ₆ H ₄ CHO, -C ₆ H ₄ C(O)CH ₃ , -C ₆ H ₄ C(O)C ₆ H ₅ , -C ₆ H ₄ CO ₂ H, -C ₆ H ₄ CO ₂ CH ₃ , -C ₆ H ₄ CONH ₂ , -C ₆ H ₄ CONHCH ₃ , -C ₆ H ₄ CON(CH ₃ ) ₂ , furanyl, thienyl, pyridyl, pyrrolyl, pyrimidyl, pyrazinyl, quinolyl, indolyl, and imidazoyl.

The term "aralkyl" includes heteroatom-unsubstituted aralkyl, heteroatom-substituted aralkyl, heteroatom-unsubstituted C _n -aralkyl, heteroatom-substituted C _n -aralkyl, heteroaralkyl, and heterocyclic aralkyl groups. In certain embodiments, lower aralkyls are contemplated. The term "lower aralkyl" refers to aralkyls of 7-12 carbon atoms (that is, 7, 8, 9, 10, 11 or 12 carbon atoms). The term "heteroatom-unsubstituted C _n -aralkyl" refers to a radical, having a single saturated carbon atom as the point of attachment, further having a total of n carbon atoms, wherein at least 6 of the carbon atoms form an aromatic ring structure containing only carbon atoms, 7 or more hydrogen atoms, and no heteroatoms. For example, a heteroatom-unsubstituted Cγ-Cio-aralkyl has 7 to 10 carbon atoms. Non-limiting examples of heteroatom-unsubstituted aralkyls are: phenylmethyl (benzyl, Bn) and phenylethyl. The term "heteroatom-substituted C _n -aralkyl" refers to a radical, having a single saturated carbon atom as the point of attachment, further having a total of n carbon atoms, O, 1 , or more than one hydrogen atom, and at least one heteroatom, wherein at least one of the carbon atoms is incorporated an aromatic ring structures, further wherein each heteroatom is independently selected from the group consisting of N, O, F, Cl, Br, I, Si, P, and S. For example, a heteroatom-substituted C ₂ -Cio-heteroaralkyl has 2 to 10 carbon atoms.

The term "acyl" includes straight-chain acyl, branched-chain acyl, cycloacyl, cyclic acyl, heteroatom-unsubstituted acyl, heteroatom-substituted acyl, heteroatom-unsubstituted C _n -acyl, heteroatom-substituted C _n -acyl, alkylcarbonyl, alkoxycarbonyl and aminocarbonyl groups. In certain embodiments, lower acyls are contemplated. The term "lower acyl" refers to acyls of 1-6 carbon atoms (that is, 1, 2, 3, 4, 5 or 6 carbon atoms). The term "heteroatom- unsubstituted C _n -acyl" refers to a radical, having a single carbon atom of a carbonyl group as the point of attachment, further having a linear or branched, cyclic or acyclic structure, further having a total of n carbon atoms, 1 or more hydrogen atoms, a total of one oxygen atom, and no additional heteroatoms. For example, a heteroatom-unsubstituted Ci-Cio-acyl has 1 to 10 carbon atoms. The groups, -CHO, -C(O)CH ₃ , -C(O)CH ₂ CH ₃ , -C(O)CH ₂ CH ₂ CH ₃ , -C(O)CH(CH ₃ ) ₂ , -C(O)CH(CH ₂ ) ₂ , -C(O)C ₆ H ₅ , -C(O)C ₆ H ₄ CH ₃ , -C(O)C ₆ H ₄ CH ₂ CH ₃ , and

-COCgH ₃ (CH ₃ ) ₂ , are non-limiting examples of heteroatom-unsubstituted acyl groups. The term "heteroatom-substituted C _n -acyl" refers to a radical, having a single carbon atom as the point of attachment, the carbon atom being part of a carbonyl group, further having a linear or branched, cyclic or acyclic structure, further having a total of n carbon atoms, 0, 1, or more than one hydrogen atom, at least one additional heteroatom, in addition to the oxygen of the carbonyl group, wherein each additional heteroatom is independently selected from the group consisting of N, O, F, Cl, Br, I, Si, P, and S. For example, a heteroatom-substituted Ci-Cio- acyl has 1 to 10 carbon atoms.. The groups, -C(O)CH ₂ CF ₃ , -CO ₂ H, -CO ₂ CH ₃ , -CO ₂ CH ₂ CH ₃ , -CO ₂ CH ₂ CH ₂ CH ₃ , -CO ₂ CH(CH ₃ ) ₂ , -CO ₂ CH(CH ₂ ) ₂ , -C(O)NH ₂ (carbamoyl), -C(O)NHCH ₃ , -C(O)NHCH ₂ CH ₃ , -CONHCH(CH ₃ ) ₂ , -CONHCH(CH ₂ ) ₂ , -CON(CH ₃ ) ₂ , and -CONHCH ₂ CF ₃ , are non-limiting examples of heteroatom-substituted acyl groups.

The term "alkoxy" includes straight-chain alkoxy, branched-chain alkoxy, cycloalkoxy, cyclic alkoxy, heteroatom-unsubstituted alkoxy, heteroatom-substituted alkoxy, heteroatom-unsubstituted C _n -alkoxy, and heteroatom-substituted C _n -alkoxy. In certain embodiments, lower alkoxys are contemplated. The term "lower alkoxy" refers to alkoxys of 1-6 carbon atoms (that is, 1, 2, 3, 4, 5 or 6 carbon atoms). The term "heteroatom- unsubstituted C _n -alkoxy" refers to a group, having the structure -OR, in which R is a heteroatom-unsubstituted C _n -alkyl, as that term is defined above. Heteroatom-unsubstituted alkoxy groups include: -OCH ₃ , -OCH ₂ CH ₃ , -OCH ₂ CH ₂ CH ₃ , -OCH(CH ₃ ) ₂ , and OCH(CH ₂ ) ₂ . The term "heteroatom-substituted C _n -alkoxy" refers to a group, having the structure -OR, in which R is a heteroatom-substituted C _n -alkyl, as that term is defined above. For example, -OCH ₂ CF ₃ is a heteroatom-substituted alkoxy group.

The term "aryloxy" includes heteroatom-unsubstituted aryloxy, heteroatom- substituted aryloxy, heteroatom-unsubstituted C _n -aryloxy, heteroatom-substituted C _n -aryloxy, heteroaryloxy, and heterocyclic aryloxy groups. The term "heteroatom-unsubstituted C _n - aryloxy" refers to a group, having the structure -OAr, in which Ar is a heteroatom- unsubstituted C _n -aryl, as that term is defined above. A non-limiting example of a heteroatom- unsubstituted aryloxy group is -OC ₆ H ₅ . The term "heteroatom-substituted C _n -aryloxy" refers to a group, having the structure -OAr, in which Ar is a heteroatom-substituted C _n -aryl, as that term is defined above.

The term "alkylamino" includes straight-chain alkylamino, branched-chain alkylamino, cycloalkylamino, cyclic alkylamino, heteroatom-unsubstituted alkylamino, heteroatom-substituted alkylamino, heteroatom-unsubstituted C _n -alkylamino, and heteroatom-

substituted C _n -alkylamino. In certain embodiments, lower alkylaminos are contemplated. The term "lower alkylamino" refers to alkylaminos of 1-6 carbon atoms (that is, 1, 2, 3, 4, 5 or 6 carbon atoms). The term "heteroatom-unsubstituted C _n -alkylamino" refers to a radical, having a single nitrogen atom as the point of attachment, further having one or two saturated carbon atoms attached to the nitrogen atom, further having a linear or branched, cyclic or acyclic structure, containing a total of n carbon atoms, all of which are nonaromatic, 4 or more hydrogen atoms, a total of 1 nitrogen atom, and no additional heteroatoms. For example, a heteroatom-unsubstituted Ci-Cio-alkylamino has 1 to 10 carbon atoms. The term "heteroatom-unsubstituted C _n -alkylamino" includes groups, having the structure -NHR, in which R is a heteroatom-unsubstituted C _n -alkyl, as that term is defined above. A heteroatom- unsubstituted alkylamino group would include -NHCH ₃ , -NHCH ₂ CH ₃ , -NHCH ₂ CH ₂ CH ₃ , -NHCH(CH ₃ ) ₂ , -NHCH(CH ₂ ) ₂ , -NHCH ₂ CH ₂ CH ₂ CH ₃ , -NHCH(CH ₃ )CH ₂ CH ₃ , -NHCH ₂ CH(CH ₃ ) ₂ , -NHC(CH ₃ ) ₃ , -N(CH ₃ ) ₂ , -N(CH ₃ )CH ₂ CH ₃ , -N(CH ₂ CH ₃ ) ₂ , N- pyrrolidinyl, and N-piperidinyl. The term "heteroatom-substituted C _n -alkylamino" refers to a radical, having a single nitrogen atom as the point of attachment, further having one or two saturated carbon atoms attached to the nitrogen atom, no carbon-carbon double or triple bonds, further having a linear or branched, cyclic or acyclic structure, further having a total of n carbon atoms, all of which are nonaromatic, 0, 1, or more than one hydrogen atom, and at least one additional heteroatom, that is, in addition to the nitrogen atom at the point of attachment, wherein each additional heteroatom is independently selected from the group consisting of ν, O, F, Cl, Br, I, Si, P, and S. For example, a heteroatom-substituted Ci-Cio-alkylamino has 1 to 10 carbon atoms. The term "heteroatom-substituted C _n - alkylamino" includes groups, having the structure -νHR, in which R is a heteroatom- substituted Cn-alkyl, as that term is defined above. The term "amide" or "amido" includes straight-chain amido, branched-chain amido, cycloamido, cyclic amido, heteroatom-unsubstituted amido, heteroatom-substituted amido, heteroatom-unsubstituted C _n -amido, heteroatom-substituted C _n -amido, alkylcarbonylamino, arylcarbonylamino, alkoxycarbonylamino, aryloxycarbonylamino, acylamino, alkylaminocarbonylamino, arylaminocarbonylamino, and ureido groups. The term "heteroatom-unsubstituted C _n -amido" refers to a radical, having a single nitrogen atom as the point of attachment, further having a carbonyl group attached via its carbon atom to the nitrogen atom, further having a linear or branched, cyclic or acyclic structure, further having a total of n carbon atoms, 1 or more hydrogen atoms, a total of one oxygen atom, a total of one nitrogen atom, and no additional heteroatoms. For example, a heteroatom-unsubstituted C ₁ -

Cio-amido has 1 to 10 carbon atoms. The term "heteroatom-unsubstituted C _n -amido" includes groups, having the structure -NHR, in which R is a heteroatom-unsubstituted C _n - acyl, as that term is defined above. The group, -NHC(O)CH3, is a non-limiting example of a heteroatom-unsubstituted amido group. The term "heteroatom-substituted C _n -amido" refers to a radical, having a single nitrogen atom as the point of attachment, further having a carbonyl group attached via its carbon atom to the nitrogen atom, further having a linear or branched, cyclic or acyclic structure, further having a total of n aromatic or nonaromatic carbon atoms, 0, 1, or more than one hydrogen atom, at least one additional heteroatom in addition to the oxygen of the carbonyl group, wherein each additional heteroatom is independently selected from the group consisting of N, O, F, Cl, Br, I, Si, P, and S. For example, a heteroatom-substituted Ci-Cio-amido has 1 to 10 carbon atoms. The term "heteroatom-substituted C _n -amido" includes groups, having the structure -NHR, in which R is a heteroatom-unsubstituted C _n -acyl, as that term is defined above. The group, -NHCO ₂ CH ₃ , is a non-limiting example of a heteroatom-substituted amido group. Protecting groups, as described herein, may also comprise an amide, such as amides used to protect amine groups.

The term "alkylthio" includes straight-chain alkylthio, branched-chain alkylthio, cycloalkylthio, cyclic alkylthio, heteroatom-unsubstituted alkylthio, heteroatom-substituted alkylthio, heteroatom-unsubstituted C _n -alkylthio, and heteroatom-substituted C _n -alkylthio. In certain embodiments, lower alkylthios are contemplated. The term "lower alkylthio" refers to alkylthios of 1-6 carbon atoms (that is, 1, 2, 3, 4, 5 or 6 carbon atoms). The term "heteroatom-unsubstituted C _n -alkylthio" refers to a group, having the structure -SR, in which R is a heteroatom-unsubstituted C _n -alkyl, as that term is defined above. The group, -SCH3, is an example of a heteroatom-unsubstituted alkylthio group. The term "heteroatom-substituted C _n -alkylthio" refers to a group, having the structure -SR, in which R is a heteroatom- substituted C _n -alkyl, as that term is defined above.

Compounds of the present invention may contain one or more asymmetric centers and thus can occur as racemates and racemic mixtures, single enantiomers, diastereomeric mixtures and individual diastereomers. In certain embodiments, a single diastereomer is present. All possible stereoisomers of the compounds of the present invention are contemplated as being within the scope of the present invention. However, in certain aspects, particular diastereomers are contemplated. The chiral centers of the compounds of the present invention can have the S- or the ^-configuration, as defined by the IUPAC 1974

Recommendations. In certain aspects, certain compounds of the present invention may comprise S- or ^-configurations at particular carbon centers.

Modifications or derivatives of the compounds, agents, and active ingredients disclosed throughout this specification are contemplated as being useful with the methods and compositions of the present invention. Derivatives may be prepared and the properties of such derivatives may be assayed for their desired properties by any method known to those of skill in the art.

In certain aspects, "derivative" refers to a chemically modified compound that still retains the desired effects of the compound prior to the chemical modification. An "anthracycline derivative," therefore, may refer to a chemically modified compound that still retains the desired effects of the parent anthracycline prior to its chemical modification. Such effects may be enhanced (e.g., slightly more effective, twice as effective, etc.) or diminished (e.g., slightly less effective, 2-fold less effective, etc.) relative to the parent anthracycline, but may still be considered an anthracycline derivative. Anthracycline derivatives may be generated that do not have the same activity or action as the parent anthracycline: indeed, such derivatives may show opposite effects. Derivatives may, for example, have the addition, removal, or substitution of one or more chemical moieties on the parent molecule. Non- limiting examples of the types modifications that can be made to the compounds and structures disclosed herein include the addition or removal of lower unsubstituted alkyls such as methyl, ethyl, propyl, or substituted lower alkyls such as hydroxymethyl or aminomethyl groups; carboxyl groups and carbonyl groups; hydroxyls; nitro, amino, amide, and azo groups; sulfate, sulfonate, sulfono, sulfhydryl, sulfonyl, sulfoxido, phosphate, phosphono, phosphoryl groups, and halide substituents. Additional modifications can include an addition or a deletion of one or more atoms of the atomic framework, for example, substitution of an ethyl by a propyl; substitution of a phenyl by a larger or smaller aromatic group. Alternatively, in a cyclic or bicyclic structure, heteroatoms such as N, S, or O can be substituted into the structure instead of a carbon atom.

Persons of ordinary skill in the art will be familiar with methods of purifying compounds of the present invention. One of ordinary skill in the art will understand that compounds of the present invention can generally be purified at any step, including the purification of intermediates as well as purification of the final products. In certain embodiments, purification is performed via silica gel column chromatography, HPLC, or crystallization.

An anthracycline prepared by methods of the present invention may be a prodrug and/or a solvate. The term "prodrug" as used herein, is understood as being a compound which, upon administration to a subject, such as a mammal, undergoes chemical conversion by metabolic or chemical processes to yield a compound any of the formulas herein, or a salt and/or solvate thereof (Bundgaard, 1991; Bundgaard, 1985). Solvates of the compounds of the present invention are preferably hydrates.

Anthracyclines prepared by methods of the present invention may comprise one or more pharmaceutically acceptable salts. The term "pharmaceutically acceptable salts," as used herein, refers to salts of compounds of this invention that are substantially non-toxic to living organisms. Typical pharmaceutically acceptable salts include those salts prepared by reaction of a compound of this invention with an inorganic or organic acid, or an organic base, depending on the substituents present on the compounds of the invention.

Non-limiting examples of inorganic acids which may be used to prepare pharmaceutically acceptable salts include: hydrochloric acid, phosphoric acid, sulfuric acid, hydrobromic acid, hydroiodic acid, phosphorous acid and the like. Examples of organic acids which may be used to prepare pharmaceutically acceptable salts include: aliphatic mono- and dicarboxylic acids, such as oxalic acid, carbonic acid, citric acid, succinic acid, phenyl- heteroatom-substituted alkanoic acids, aliphatic and aromatic sulfuric acids and the like. Pharmaceutically acceptable salts prepared from inorganic or organic acids thus include hydrochloride, hydrobromide, nitrate, sulfate, pyrosulfate, bisulfate, sulfite, bisulfate, phosphate, monohydrogenphosphate, dihydrogenphosphate, metaphosphate, pyrophosphate, hydroiodide, hydrofluoride, acetate, propionate, formate, oxalate, citrate, lactate, p- toluenesulfonate, methanesulfonate, maleate, and the like.

Pharmaceutically acceptable salts include the salts formed between carboxylate or sulfonate groups found on some of the compounds of this invention and inorganic cations, such as sodium, potassium, ammonium, or calcium, or such organic cations as isopropylammonium, trimethylammonium, tetramethylammonium, and imidazolium.

It should be recognized that the particular anion or cation forming a part of any salt of this invention is typically not critical, so long as the salt, as a whole, is pharmacologically acceptable. Additional examples of pharmaceutically acceptable salts and their methods of preparation and use are presented in Handbook of Pharmaceutical Salts: Properties, Selection and Use (P. H. Stahl & C. G. Wermuth eds., Verlag Helvetica Chimica Acta, 2002), which is incorporated herein by reference.

The term "saccharide" includes oxidized, reduced or substituted saccharides. Saccharides of this invention include, but are not limited to, ribose, arabinose, xylose, lyxose, allose, altrose, glucose, mannose, fructose, glucose, idose, galactose, talose, ribulose, sorbose, tagatose, gluconic acid, glucuronic acid, glucaric acididuronic acid rhamnose, fucose, N- acetyl glucosamine, N-acetyl galactosamine, N-acetyl neuraminic acid, sialic acid, derivatives of saccharides such as acetals, amines, and phosphorylated sugars, oligosaccharides, as well as open chain forms of various sugars, and the like.

As used herein, the term "nucleophile" or "nucleophilic" generally refers to atoms bearing lone pairs of electrons. Such terms are well known in the art and include -NH ₂ , thiolate, carbanion and hydroxyl.

As used herein, the term "leaving group" generally refers to a group readily displaceable by a nucleophile, such as an amine, an alcohol, or a thiol nucleophile. Such leaving groups are well known and include carboxylates, N-hydroxysuccinimide, N- hydroxybenzotriazole, triflates, tosylates, mesylates, alkoxy, thioalkoxy and the like. 1. Protecting Groups

When a chemical reaction is to be carried out selectively at one reactive site or functional group in a multifunctional compound, other reactive sites may be temporarily blocked in order to convey the proper selectivity. A "protecting group," as used herein, is defined as a group used for the purpose of this temporary blockage. During the synthesis of certain compounds of the present invention, various functional groups often must be protected using protecting groups (or protecting agents) at various stages of the synthesis. Functional groups necessary for the desired transformation should remain unprotected. The term "functional group" generally refers to how persons of skill in the art classify chemically reactive groups. Examples of functional groups include hydroxyl, amine, sulfhydryl, amide, carboxyls, carbonyls, etc. Protecting groups exist for each of these types of functional groups. In certain methods of the present invention, it is specifically contemplated that an anthracycline may contain one or more protecting groups.

There are a number of methods well known to those skilled in the art for installing a protecting group. For protecting agents, their reactivity, installation and use, see, e.g., Greene and Wuts, 1999, herein incorporated by reference in its entirety. The function of a protecting group is to protect one or more functionalities {e.g., -NH ₂ , -SH, -COOH) during subsequent reactions which would not proceed well, either because the free (in other words, unprotected) functional group would react and be functionalized in a way that is inconsistent with its need to be free for subsequent reactions, or the free functional group would interfere in the

reaction. The same protecting group may be used to protect one or more of the same or different functional group(s). Also, different protecting groups can be used to protect the same type of functional group within a single compound in multiple steps.

When a protecting group is no longer needed, it is removed by methods well known to those skilled in the art. For deprotecting agents and their use, see, e.g., Greene and Wuts, 1999. Agents used to remove the protecting group are sometimes called deprotecting or deblocking agents. Protecting groups must be readily removable (as is known to those skilled in the art) by methods employing deprotecting agents that are well known to those skilled in the art. It is well known that certain deprotecting agents remove some protective groups and not others, while other deprotecting agents remove several types of protecting groups from several types of functional groups. Thus, a first deprotecting agent may be used to remove one type of protecting group, followed by the use of a second deprotecting agent to remove a second type of protecting group, and so on.

Amino protecting groups are well known to those skilled in the art. See, for example, Greene and Wuts, 1999, Chapter 7. Amino protecting groups that may, in certain embodiments, be employed in methods of the present invention include ϊ-butoxycarbonyl, benzyloxycarbonyl, formyl, trityl, acetyl, trichloroacetyl, dichloroacetyl, chloroacetyl, trifluoroacetyl, difluoroacetyl, fluoroacetyl, benzyl chloroformate, 4- phenylbenzyloxycarbonyl, 2-methylbenzyloxycarbonyl, 4-ethoxybenzyloxycarbonyl, 4- fiuorobenzyloxycarbonyl, 4-chlorobenzyloxycarbonyl, 3-chlorobenzyloxycarbonyl, 2- chlorobenzyloxycarbonyl, 2,4-dichlorobenzyloxycarbonyl, 4-bromobenzyloxycarbonyl, 3- bromobenzyloxycarbonyl, 4-nitrobenzyloxycarbonyl, 4-cyanobenzyloxycarbonyl, 2-(4- xenyl)isopropoxycarbonyl, 1 , 1 -diphenyleth- 1 -yloxycarbonyl, 1 , 1 -diphenylprop- 1 - yloxycarbonyl, 2-phenylprop-2-yloxycarbonyl, 2-(p-toluyl)prop-2 -yloxycarbonyl, cyclopentanyloxycarbonyl, 1-methylcyclopentanyloxycarbonyl, cyclohexanyloxycarbonyl, 1- methylcyclohexanyloxycabonyl, 2-methylcyclohexanyloxycarbonyl, 2-(4- toluylsulfonyl)ethoxycarbonyl, 2-(methylsulfonyl)ethoxycarbonyl, 2-

(triphenylphosphino)ethoxycarbonyl, fluorenylmethoxycarbonyl, 2-

(trimethylsilyl)ethoxycarbonyl, allyloxycarbonyl, 1 -(trimethylsilylmethyl)prop- 1 - enyloxycarbonyl, 5-benzisoxalylmethoxycarbonyl, 4-acetoxybenzyloxycarbonyl, 2,2,2- trichloroethoxycarbonyl, 2-ethynyl-2-propoxycarbonyl, cyclopropylmethoxycarbonyl, 4- (decyloxyl)benzyloxycarbonyl, isobomyloxycarbonyl, 1 -piperidyloxycarbonyl and 9- fluorenylmethyl carbonate, for example. In certain embodiments of the present invention, the amine protecting group is t-butoxycarbonyl.

2. Solvents

Solvent choices for the methods of the present invention may depend, for example, on which one(s) will facilitate the solubilizing of all the reagents or, for example, which one(s) will best facilitate the desired reaction (particularly when the mechanism of the reaction is known). Solvents may include, for example, polar solvents and non-polar solvents. Solvents choices include, but are not limited to, tetrahydrofuran, dimethylformamide, dimethylsulfoxide, dioxane, methanol, ethanol, hexane, dichloromethane, methylene chloride and acetonitrile. More than one solvent may be chosen for any particular reaction or purification procedure. Water may also be admixed into any solvent choice. Further, water, such as distilled water, may constitute the reaction medium instead of a solvent.

In certain embodiments, a chlorinated hydrocarbon solvent is employed in certain steps of the methods discussed herein, such as a C-4' -OH alkylation step. Non- limiting examples of chlorinated hydrocarbon solvents include dichloromethane, dichloroethane and methylene chloride. In certain embodiments, addition of a chlorinated hydrocarbon solvent facilitates the alkylation step in that the yield is improved and/or side -product production is minimized.

In view of the above definitions, other chemical terms used throughout this application can be easily understood by those of skill in the art. Terms may be used alone or in any combination thereof. C. Examples

The following examples are included to demonstrate certain preferred embodiments of the invention. It should be appreciated by those of skill in the art that the techniques disclosed in the examples which follow represent techniques discovered by the inventor to function well in the practice of the invention, and thus can be considered to constitute preferred modes for its practice. However, those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the spirit and scope of the invention.

EXAMPLE 1

Synthesis of 3-N-trifluoroacetyl-4-0-benzyldaunorubicin:

(8S)-10-(2R,4R,5S)-4-trifluoroacetylaminotetrahydro-5-ben zyloxy-6-methyl-2H-pyran- 2-yloxy)-8-acetyl-7,8,9,10-tetrahydro-6,8,ll-trihydroxy-l-me thoxytetraceπe-5,12-dione

Production of 3-N-trifluoroacetyldaunorubicin

Daunorubicin (1 g) is dissolved in methanol (4 mL) in a 25-mL flask. Triethylamine (0.6 mL) and ethyl trifluoroacetate (0.6 mL) are introduced into the flask. The contents of the flask are agitated and the reaction progress is monitored (TLC analysis chloroform/methanol/ammonia = 85/15/1). After the reaction is complete (approximately 1 h), the mixture is subjected to rotary vacuum evaporation and the remainder is dissolved in chloroform (20 mL), washed with IN aqueous hydrochloric acid solution and then neutralized with water. The chloroform solution is dried with sodium sulfate, the drying agent is removed, and the filtrate is evaporated under reduced pressure. The residue was dissolved in chloroform (1 mL) and the product was precipitated with hexane (20 mL). The product obtained (3-N-trifluoroacetyldaunorubicin) is chromatographically pure and may be used in a further step, such as the synthesis discussed below.

Production of 3 '-N-trifluoroacetyl-^-O-benzyldaunorubicin 3'-N-Trifluoroacetyldaunorubicin (4.7 g; 7.5 mmol) is dissolved in dimethyl formamide (47 mL). After cooling to a temperature of 0 ⁰ C, sodium hydride (4.5 g) is added and the contents are agitated for several minutes. Benzyl bromide (13.4 mL) and methylene chloride (150 mL) are added. The agitation is continued for 2 h, maintaining the temperature at 0 ⁰ C. The reaction mixture is treated with an aqueous acetic acid solution to achieve a neutral pH, washed with water (10 mL), diluted with methylene chloride (100 mL), dried with sodium sulfate and, after removal of the drying agent, the solvent is evaporated in a rotary vacuum evaporator. The remainder is dissolved in methylene chloride (2 mL) and the product is precipitated with hexane. The product obtained is purified by chromatography using a hexane-ethyl acetate mixture with an increasing amount of ethyl acetate. 1.5 g of the title compound is obtained (yield: 28%). The compound obtained may be an intermediate product

for producing doxorubicin derivatives, such as the following synthesis of 4-0- benzyldoxorubicin :

EXAMPLE 2 Large-scale Benzylation of 3'-N-Trifluoroacetyldaunorubicin

A solution of 3'-N-trifluoroacetyldaunorubicin (50 g, 80.2 mmol) in DMF (200 mL) was cooled to 5°C and sodium hydride (60% dispersion in mineral oil) (1.2 mol, 48 g) was added. After a very brief stirring period, a solution of benzyl bromide (143 mL) in dichloromethane (800 mL) was added with vigorous stirred using an overhead mechanical stirrer. The cooling bath was removed and the reaction mixture was allowed to warm to ambient temperature with continued mechanical stirring. Progress of the reaction was monitored by TLC on silica gel plates (toluene: acetone 5:1 as eluent). After 2.5 hr, the reaction mixture was cooled to -18 ⁰ C and then neutralized using a separately prepared solution of dilute acetic acid (68 mL). The resulting phases were separated and the organic phase was washed with water until neutral and dried over sodium sulfate. The drying agent was removed by filtration and solvent and the filtrate was concentratd in vacuo to obtain a residue. The residue was dissolved in dichloromethane (200 mL) and crude product was precipitated using hexanes. Subsequently, product was isolated from the precipited crude solid using column chromatography (Silicagel 60) using dichloromethane, then dichloromethane: acetone mixtures (98:2 and 95:5) as an eluents. 17.2 g of pure product (yield 30.2%) was obtained.

All of the methods and apparatuses disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the compositions and methods of this invention have been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations may be applied to

the methods and apparatuses and in the steps or in the sequence of steps of the methods described herein without departing from the concept, spirit and scope of the invention. More specifically, it will be apparent that certain agents which are both chemically and physiologically related may be substituted for the agents described herein while the same or similar results would be achieved. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the invention as defined by the appended claims.

REFERENCES

The following references, to the extent that they provide exemplary procedural or other details supplementary to those set forth herein, are specifically incorporated herein by reference.

U.S. Patent No. 6,673,907 Polish Patent Appl. No. P 380561

Bundgaard, H., Design of Prodrugs, pp. 7-9, 21-24, Elsevier, Amsterdam 1985.

Bundgaard, Drugs of the Future, 16:443-458, 1991.

Cassinelli, G. et al, European Patent Application DE-EP 225 IA (August 13, 1981).

El Khadem, ed., "Recent Developments in the Chemistry of Doxorubicin-related anthracyline glycosides," in Anthracycline Antibiotics, Academic Press, 1982. Greene and Wuts, Protecting Groups in Organic Synthesis, 3 ^rd ed., John Wiley & Sons, Inc.,

1999. Grynkiewicz et al, Wiadomosci Chemiczne [Journal of Polish Chemical Society], 56:536-

560, 2002.

Remington's Pharmaceutical Sciences, 18 ^th Ed. Mack Printing Company, 1990. Stahl and Wermuth, eds., Handbook of Pharmaceutical Salts: Properties, Selection and Use,

Verlag Helvetica Chimica Acta, 2002.