CANCER MULTIDRUG RESISTANCE

TECHNICAL FIELD OF THE INVENTION

The present invention relates to use of prodrug of 4,9-dihydroxy-naphtho[2,3-b]furan derivative for circumventing cancer multidrug resistance. The present invention also relates to use of prodrug of 4,9-dihydroxy-naphtho[2,3-b]furan derivative for the treatment of various types of cancers exhibiting multidrug resistance phenomenon. The present invention further relates to use of the pharmaceutically acceptable composition comprising prodrug of 4,9- dihydroxy-naphtho[2,3-b]furan derivative and methods of using said composition in the treatment of various types of cancers exhibiting multidrug resistance phenomenon.

BACKGROUND OF THE INVENTION

Cancer multidrug resistance is defined as the cross-resistance or insensitivity of cancer cells to the cytostatic or cytotoxic actions of various anticancer drugs which are structurally or functionally unrelated and have different molecular targets (Gottesman M. M. Cancer Res, 1993, vol. 53, p747-54). The resistance of human tumor to multiple chemotherapeutic drugs has been recognized as a major reason for the failure of cancer therapy (Gottesman M. M., Pastan I. Annu Rev Biochem, 1993, vol. 62, p385-427).

4,9-dihydroxy-naphtho[2,3-b]furans are unstable in vitro under aerobic condition, but can be generated in vivo by hydrolyzing esters of 4,9-dihydroxy-naphtho[2,3-b]furans or by reducing naphtho[2,3-b]furan-4,9-diones (PCT application, PCT/CN2011/000357). So esters of 4,9- dihydroxy-naphtho[2,3-b]furans and naphtho[2,3-b]furan-4,9-diones are the prodrugs of 4,9- dihydroxy-naphtho[2,3-b]furans. 4,9-dihydroxy-naphtho[2,3-b]furans are active pharmaceutical ingredients for effective treatment of cancer and other diseases, disorders and conditions (PCT application, PCT/CN2011/000357). However, activity of 4,9-dihydroxy-naphtho[2,3-b]furans against multidrug resistance cancer has not been reported.

As cancer is a leading cause of death worldwide, accounting for 13% of all deaths according to 2004 World Health Organization statistics, there remains a need for novel compounds as active pharmaceutical ingredient useful for more effective treatment of cancer.

SUMMARY

The present invention relates to use of prodrug of 4,9-dihydroxy-naphtho[2,3-b]furan derivative for circumventing cancer multidrug resistance (MDR). The present invention also relates to use of prodrug of 4,9-dihydroxy-naphtho[2,3-b]furan derivative for the treatment of various types of cancers exhibiting multidrug resistance (MDR) phenomenon. The present invention further relates to use of the pharmaceutically acceptable composition comprising prodrug of 4,9-dihydroxy-naphtho[2,3-b]furan derivative and methods of using said composition in the treatment of various types of cancers exhibiting multidrug resistance (MDR) phenomenon.

DEFINITIONS

As used herein, the following definitions shall apply unless otherwise indicated.

The term "aliphatic" or "aliphatic group," as used herein, means a straight-chain (i.e., unbranched) or branched, substituted or unsubstituted hydrocarbon chain that is completely saturated or that contains one or more units of unsaturation, or a monocyclic hydrocarbon or bicyclic hydrocarbon that is completely saturated or that contains one or more units of unsaturation, but which is not aromatic (also referred to herein as "carbocycle," "cycloaliphatic" or "cycloalkyl"), that has a single point of attachment to the rest of the molecule.

The term "halogen" means F, CI, Br, or I.

The term "aryl" used alone or as part of a larger moiety as in or "aryloxyalkyl," refers to monocyclic or bicyclic ring systems having a total of five to fourteen ring members, wherein at least one ring in the system is aromatic and wherein each ring in the system contains 3 to 7 ring members. The term "aryl" may be used interchangeably with the term "aryl ring."

The terms "heteroaryl" and "heteroar-," used alone or as part of a larger moiety, e.g., "heteroaralkyl," or "heteroaralkoxy," refer to groups having 5 to 10 ring atoms, preferably 5, 6, or 9 ring atoms; having 6, 10, or 14 π electrons shared in a cyclic array; and having, in addition to carbon atoms, from one to five heteroatoms. The term "heteroatom" refers to nitrogen, oxygen, or sulfur, and includes any oxidized form of nitrogen or sulfur, and any quaternized form of a basic nitrogen. Heteroaryl groups include, without limitation, thienyl, furanyl, pyrrolyl, imidazolyl, pyrazolyl, triazolyl, tetrazolyl, oxazolyl, isoxazolyl, oxadiazolyl, thiazolyl, isothiazolyl, thiadiazolyl, pyridyl, pyridazinyl, pyrimidinyl, pyrazinyl, indolizinyl, purinyl, naphthyridinyl, and pteridinyl.

As used herein, the terms "heterocycle," "heterocyclyl," "heterocyclic radical," and "heterocyclic ring" are used interchangeably and refer to a stable 5- to 7-membered monocyclic or 7-10-membered bicyclic heterocyclic moiety that is either saturated or partially unsaturated, and having, in addition to carbon atoms, one or more, preferably one to four, heteroatoms, as defined above.

As used herein and in the claims, the singular forms "a", "an", and "the" include the plural reference unless the context clearly indicates otherwise. Thus, for example, a reference to "a compound" includes a plurality of such compounds.

The terms "administer," "administering," or "administration," as used herein, refer to either directly administering a compound or composition to a patient.

The phrase "pharmaceutically acceptable" is employed herein to refer to those compounds, materials, compositions, and/or dosage forms which are, within the scope of sound medical judgment, suitable for use in contact with the tissues of human beings and animals without excessive toxicity, irritation, allergic response, or other problem or complication, commensurate with a reasonable benefit/risk ratio.

As used herein, the term "prodrug" means an agent that is converted into the parent drug in vivo. In certain embodiments, a prodrug is easier to administer than a parent drug. In certain embodiments, a prodrug has improved bioavailability by oral administration compared to the parent drug. Prodrugs may also have improved stability in pharmaceutical compositions over the parent drug. In certain embodiments, a prodrug has reduced toxicity compared to the parent drug by avoiding unnecessary exposure to unintended target tissues.

The phrases "parenteral administration" and "administered parenterally" as used herein means modes of administration other than enteral and topical administration, usually by injection, and includes, without limitation, intravenous, intramuscular, intraarterial, intrathecal, intracapsular, intraorbital, intracardiac, intradermal, intraperitoneal, transtracheal, subcutaneous, subcuticular, intraarticulare, subcapsular, subarachnoid, intraspinal and intrasternal injection and infusion.

The phrases "systemic administration," "administered systemically," "peripheral administration" and "administered peripherally" as used herein mean the administration of a compound, drug or other material other than directly into the central nervous system, such that it enters the patient's system and, thus, is subject to metabolism and other like processes, for example, subcutaneous administration.

As used herein, the term "therapeutically effective amount" means an amount of a substance (e.g., a therapeutic agent, composition, and/or formulation) that elicits a desired biological response when administered as part of a therapeutic regimen.

As used herein, the term "treat," "treatment," or "treating" refers to any method used to partially or completely alleviate, ameliorate, relieve, inhibit, prevent, delay onset of, reduce severity of and/or reduce incidence of one or more symptoms or features of a disease, disorder, and/or condition.

The expression "unit dose" as used herein refers to a physically discrete unit of a formulation appropriate for a subject to be treated. It will be understood, however, that the total daily usage of a formulation of the present invention will be decided by the attending physician within the scope of sound medical judgment.

An individual who is "suffering from" a disease, disorder, and/or condition has been diagnosed with and/or displays one or more symptoms of the disease, disorder, and/or condition. An individual who is "susceptible to" a disease, disorder, and/or condition has not been diagnosed with the disease, disorder, and/or condition.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

4,9-dihydroxy-naphtho[2,3-b]furans (I) are active pharmaceutical ingredients for effective treatment of cancer and other diseases, disorders and conditions (PCT application, PCT/CN201 1/000357). 4,9-dihydroxy-naphtho[2,3-b]furans (I) are unstable in vitro under aerobic condition, but can be generated in vivo by hydrolyzing esters of 4,9-dihydroxy- naphtho[2,3-b]furans (II) or by reducing naphtho[2,3-b]furan-4,9-diones (III), as shown in scheme 1.

Scheme 1 : Active pharmaceutical ingredients, 4,9-dihydroxy-naphtho[2,3-b]furans (I) are generated in vivo by hydrolyzing esters of 4,9-dihydroxy-naphtho[2,3-b]furans (II) or by reducing naphtho[2,3-b]furan-4,9-diones (III).

The n, R ¹ , R ² , R ³ , R ⁴ , R ⁵ in scheme 1 are defined as: n is 0-4; each R ¹ is independently halogen; -N0 ₂ ; -CN; -OR; -SR; -N ⁺ (R) ₃ ; -N(R) ₂ ; -C(0)R; -C0 ₂ R;

-C(0)C(0)R; -C(0)CH ₂ C(0)R; -S(0)R; -S(0) ₂ R; -C(0)N(R) ₂ ; -S0 ₂ N(R) ₂ ; -OC(0)R; -N(R)C(0)R; -N(R)N(R) ₂ ; -N(R)C(=NR)N(R) ₂ ; -C(=NR)N(R) ₂ ;

C=NOR; -N(R)C(0)N(R) ₂ ; -N(R)S0 ₂ N(R) ₂ ; -N(R)S0 ₂ R; -OC(0)N(R) ₂ ; or an optionally substituted group selected from Ci_i ₂ aliphatic; 3- to 14-membered carbocyclyl; 3- to 14-membered heterocyclyl; 6- to 14-membered aryl; or 5- to 14-membered heteroaryl, or: two R ¹ groups on adjacent carbon atoms are taken together with their intervening atoms to form an optionally substituted ring selected from 3- to 14-membered carbocycle; 3- to 14-membered heterocycle; a 6- to 14-membered aryl ring; or a 5- to 14-membered heteroaryl ring; each R ² and R ³ is independently hydrogen, -S(=0) ₂ OR ^a , -P(=0)OR ^a OR ^b , -C(=0)R ^c ; wherein each R ^a and R ^b is independently hydrogen, sodium, potassium, amine cation, or an optionally substituted group selected from Ci_i ₂ aliphatic; 3- to 14-membered carbocyclyl; 3- to 14-membered heterocyclyl; 6- to 14-membered aryl; or 5- to 14-membered heteroaryl; or:

R ^a and R ^b are taken together with their intervening atoms to form an optionally substituted 3- to 14-membered heterocycle;

R° is hydrogen; -N(R) ₂ ; -OR; -SR; or an optionally substituted group selected from Ci_i ₂ aliphatic; 3- to 14-membered carbocyclyl; 3- to 14-membered heterocyclyl; 6- to 14- membered aryl; or 5- to 14-membered heteroaryl; R ⁴ is independently hydrogen; halogen; -N0 ₂ ; -OR; -SR; -N ⁺ (R) ₃ ; -N(R) ₂ ; -C(0)R; -C0 ₂ R; -C(0)C(0)R; -C(0)CH ₂ C(0)R; -S(0)R; -S(0) ₂ R; -C(0)N(R) ₂ ; -S0 ₂ N(R) ₂ ; -OC(0)R; -N(R)C(0)R; -N(R)N(R) ₂ ; -N(R)C(=NR)N(R) ₂ ; -C(=NR)N(R) ₂ ;

C=NOR; -N(R)C(0)N(R) ₂ ; -N(R)S0 ₂ N(R) ₂ ; -N(R)S0 ₂ R; -OC(0)N(R) ₂ ; or an optionally substituted group selected from Ci_i ₂ aliphatic; 3- to 14-membered carbocyclyl; 3- to 14-membered heterocyclyl; 6- to 14-membered aryl; or 5- to 14-membered heteroaryl; or:

R and R are taken together with their intervening atoms to form an optionally substituted ring selected from 3- to 14-membered carbocycle or 3- to 14-membered heterocycle;

R ⁵ is independently halogen; -N0 ₂ ; -CN; -OR; -SR; -N ⁺ (R) ₃ ; -N(R) ₂ ; -C(0)R; -C0 ₂ R; - C(0)C(0)R; -C(0)CH ₂ C(0)R; -S(0)R; -S(0) ₂ R; -C(0)N(R) ₂ ; -S0 ₂ N(R) ₂ ; -OC(0)R; - N(R)C(0)R; -N(R)N(R) ₂ ; -N(R)C(=NR)N(R) ₂ ; -C(=NR)N(R) ₂ ; - C=NOR; -N(R)C(0)N(R) ₂ ; -N(R)S0 ₂ N(R) ₂ ; -N(R)S0 ₂ R; -OC(0)N(R) ₂ ; or an optionally substituted group selected from Ci_i ₂ aliphatic, 3- to 14-membered carbocyclyl; 3- to 14-membered heterocyclyl; 6- to 14-membered aryl; or 5- to 14-membered heteroaryl; or:

R ⁴ and R ⁵ are taken together with their intervening atoms to form an optionally

substituted ring selected from 3- to 14-membered carbocycle or 3- to 14-membered heterocycle; each R is independently hydrogen or an optionally substituted group selected from C _1-12 aliphatic; 3- to 14-membered carbocyclyl; 3- to 14-membered heterocyclyl; a 6- to 14- membered aryl; or 5- to 14-membered heteroaryl.

In some embodiments, n is 0. In some embodiments, n is 1. In some embodiments, n is 2. In some embodiments, n is 3. In some embodiments, n is 4.

In certain embodiments, R ¹ is halogen. In some embodiments, R ¹ is -CN. In some embodiments, R ¹ is -CF ₃ . In some embodiments, R ¹ is -OH.

In some embodiments, R ² is hydrogen. In some embodiments, R ² is -C(=0)R ^c , wherein R° is optionally substituted C _1-12 aliphatic. In some embodiments, R ² is -P(=0)OR ^a OR ^b , wherein R ^a and R ^b are each independently hydrogen, sodium, potassium, or optionally substituted C _1-12 aliphatic. In some embodiments, R ² is -S(=0) ₂ 0R ^a , wherein R ^a is hydrogen, sodium, or potassium.

In some embodiments, R ³ is hydrogen. In some embodiments, R ³ is -C(=0)R ^c , wherein R° is optionally substituted C _1-12 aliphatic. In some embodiments, R ³ is -P(=0)OR ^a OR ^b , wherein R ^a and R ^b are each independently hydrogen, sodium, potassium, or optionally substituted C _1-12 aliphatic. In some embodiments, R ³ is -S(=0) ₂ 0R ^a , wherein R ^a is hydrogen, sodium, or potassium.

In some embodiments, R ⁴ is hydrogen. In some embodiments, R ⁴ is other than hydrogen. In some embodiments, R ⁴ is optionally substituted 6- to 14-membered aryl. In some embodiments, R ⁴ is optionally substituted phenyl. In some embodiments, R ⁴ is -N(R) ₂ , wherein R is independently an optionally substituted group selected from C _1-12 aliphatic or 6- to 14- membered aryl. In certain embodiments, R ⁵ is -N0 ₂ . In some embodiments, R ⁵ is -C(0)R, wherein R is an optionally substituted group selected from C _1-12 aliphatic or 6- to 14-membered aryl. In some embodiments, R ⁵ is -C(0)N(R) ₂ , wherein each R is independently an optionally substituted group selected from C _1-12 aliphatic or 6- to 14-membered aryl.

In certain embodiments, R ⁴ and R ⁵ are taken together with their intervening atoms to form an optionally substituted ring selected from 3- to 14-membered carbocycle or 3- to 14-membered heterocycle.

In some embodiments, R ¹ is halogen, cyano, or CF ₃ ; n is 0, 1, or 2; R ² and R ³ are each independently hydrogen, isobutyryl, pivaloyl, acetyl, octanoyl, dodecanoyl, or hexanoyl; R ⁴ is hydrogen or -N(R) ₂ ; and R ⁵ is -C(0)R, wherein R is an optionally substituted group selected from C _1-12 aliphatic or 6- to 14-membered aryl. In some embodiments, R ¹ is halogen or CF ₃ ; n is 0, 1, or 2; R ^z and R ^J are each independently octanoyl; R is hydrogen; and R is -C(0)R, wherein R is optionally substituted C _1-12 aliphatic.

Exemplary compounds of formula II and III are set forth in table 1 below.

Table 1

compound I compound II

compound V compound VI

As shown in Example 7, compounds I, III, IV, V, and VI can indiscriminately kill regular cancer cell lines and 5-FU or taxol or doxorubicin resistance cancer cell lines. However, 5-FU resistance BEL7404 is also resistant to taxol and doxorubicin; Doxorubicin resistance MCF7 is also resistant to 5-FU and taxol; Taxol resistance A2780 is also resistant to 5-FU and doxorubicin.

The present invention relates to, among other things, use of esters of 4,9-dihydroxy- naphtho[2,3-b]furans (II) or use of naphtho[2,3-b]furan-4,9-diones (III) for circumventing cancer multidrug resistance (MDR). The present invention also relates to use of esters of 4,9-dihydroxy-naphtho[2,3-b]furans (II) or use of naphtho[2,3-b]furan-4,9-diones (III) for the treatment of various types of cancers exhibiting multidrug resistance (MDR) phenomenon.

The present invention further relates to use of the pharmaceutically acceptable composition comprising ester of 4,9-dihydroxy-naphtho[2,3-b]furan derivative (II) or naphtho[2,3-b]furan- 4,9-dione derivative (III) and method of using said composition in the treatment of various types of cancers exhibiting multidrug resistance (MDR) phenomenon.

The pharmaceutically acceptable compositions comprise a compound of formula II or III and at least one pharmaceutically acceptable excipient or carrier or diluent. As used herein, the pharmaceutically acceptable excipient or carrier or diluent is intended to include any and all solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents, and the like, compatible with pharmaceutical administration. The pharmaceutically acceptable excipient or carrier or diluent includes, but not limited to, water, saline solution, dextrose solution, triacetin, human albumin or its derivative, glycerol mono-(or di-)fatty acid esters, lecithin, phospholipids (such as phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl inositol, sphingomyelin, and the like), cholesterol, PEG- phospholipids, PEG-cholesterol, PEG-cholesterol derivatives, PEG-vitamin A, PEG-vitamin E, PEG-glycerol mono-(or di-)fatty acid esters, ethylene glycol mono-fatty acid esters, propylene glycol mono-fatty acid esters, 3-dialkyl(Cl-8)amino-propylene glycol di-fatty acid esters, poly(ethylene glycol) mono-fatty acid esters, stearic acid, sorbitan esters, polyoxyethylene alkyl ethers, polyoxyethylene castor oil derivatives, polyoxyethylene sorbitan fatty acid esters, polyvinyl alcohol, polyvinylpyrrolidone, poloxamers; poloxamines, mixtures of sucrose stearate and sucrose distearate, random copolymers of vinyl acetate and vinyl pyrrolidone, deoxycholic acid, glycodeoxycholic acid, taurocholic acid, anionic biopolymers (such as casein or its derivative), anionic polymers, cationic biopolymers, salts of these acids (deoxycholic acid, glycocholic acid, glycodeoxycholic acid, taurocholic acid), the bulking agents, and mixtures thereof. The bulking agent includes starches or its derivatives, mannitol, lactose, maltitol, maltodextrin, maltose, dextrates, dextrin, dextrose, fructose, sorbitol, glucose, sucrose, carboxymethylcellulose, hydroxypropylcellulose, microcrystalline cellulose, ethylcellulose, methylcellulose, other suitable cellulose derivatives, gelatin, alginic acid, and its salt, colloidal silicon dioxide, croscarmellose sodium, crospovidone, magnesium aluminum silicate, povidone, benzyl phenylformate, chlorobutanol, diethyl phthalate, calcium stearate, glyceryl palmitostearate, magnesium oxide, poloxamer, polyvinyl alcohol, sodium benzoate, sodium lauryl sulfate, sodium stearyl fumarate, stearic acid, talc, zinc stearate, acacia, acrylic and methacrylic acid co-polymers, gums such as guar gum, milk derivatives such as whey, pharmaceutical glaze, glyceryl palmitostearate, hydrogenated vegetable oil, kaolin, magnesium carbonate, magnesium oxide, polymethacrylates, sodium chloride and mixtures thereof.

Formulations of a compound of formula II or III include those suitable for oral, nasal, topical (including buccal and sublingual), rectal, vaginal and/or parenteral administration. The formulation may conveniently be presented in unit dosage form and may be prepared by any methods well known in the art of pharmacy. The amount of active ingredient, which can be combined with a carrier material to produce a single dosage form, will generally be that amount of the compound which produces a therapeutic effect. Generally, out of 100%, this amount will range, for example, from about 1% to about 99% of active ingredient, from about 5% to about about 70%, from about 10% to about 30%. In some embodiments, a compound of formula II is formulated as an aqueous nanoparticle suspension prepared according to the method as described in PCT/CN2012/000190.

In some embodiments, the present invention provides a method of treating a subject suffering from or susceptible to a drug resistance cancer, the method comprising administering to the subject a therapeutically effective amount of a compound of formula II or III. In certain embodiments, a drug resistance cancer is resistant to an approved chemotherapeutic drugs, including, but not limited to, alkylating drugs (mechlorethamine, chlorambucil, Cyclophosphamide, Melphalan, Ifosfamide), antimetabolites (Methotrexate), purine antagonists and pyrimidine antagonists (6-Mercaptopurine, 5-Fluorouracil, Cytarabine, Gemcitabine), spindle poisons (Vinblastine, Vincristine, Vinorelbine, Paclitaxel), podophyllotoxins (Etoposide, Irinotecan, Topotecan), antibiotics (Doxorubicin, Bleomycin, Mitomycin), nitrosoureas (Carmustine, Lomustine), inorganic ions (Cisplatin, Carboplatin), enzymes (Asparaginase), and hormones (Tamoxifen, Leuprolide, Flutamide, and Megestrol), to name a few. In certain embodiments, a drug resistance cancer is resistant to certain cytotoxic or anticancer agent currently in clinical trials and which may ultimately be approved by the FDA (including, but not limited to, epothilones and analogues thereof and geldanamycins and analogues thereof). In some embodiments, the drug resistance cancer is a hematological malignancy. In certain embodiments, the drug resistance cancer is a solid tumor. Exemplary drug resistance cancers that may be treated using compounds of formula II or III include colon cancer, lung cancer, bone cancer, pancreatic cancer, stomach cancer, esophageal cancer, skin cancer, brain cancer, liver cancer, ovarian cancer, cervical cancer, uterine cancer, testicular cancer, prostate cancer, bladder cancer, kidney cancer, neuroendocrine cancer, breast cancer, gastric cancer, eye cancer, nasopharyngeal cancer, gallbladder cancer, laryngeal cancer, oral cancer, penile cancer, glandular tumors, rectal cancer, small intestine cancer, head and neck cancer, multiple myeloma, colorectal carcinoma, kaposi sarcoma, ewing's sarcoma, osteosarcoma, leiomyosarcoma, glioma, meningioma, medulloblastoma, melanoma, urethral cancer, vaginal cancer, to name but a few. In certain embodiments, the drug resistance cancer is a refractory or relapsed malignancy which is resistant to a particular chemotherapeutic agent.

EXEMPLIFICATION

Example 1

Preparation of 2-acetyl-naphtho[2,3-b]furan-4,9-dione (Compound VI)

To an 1 L round-bottom flask, 600 ml of 4-hydroxy-2-butanone, 100 ml of water, 50 ml of methanol and 20 ml of 85% phosphoric acid were added. The mixture was stirred at room temperature for 30 minutes, and then distilled under reduced pressure (150-200 mmHg). Fraction at the boiling point of 65-80°C was collected. To the collected fraction, 80 grams of sodium chloride was added. The resulting mixture was stirred at 4°C for 1 hour, and then top organic layer was separated with funnel, dried with anhydrous sodium sulfate, and place at 4°C for use.

To a 500 ml round-bottom flask containing 16.1 grams (0.23 mol, prepared above) of 3- buten-2-one and 40 ml of dichloromethane cooled in an ice-salt bath, 36.7 grams (0.23 mol) of bromine diluted in 10 ml of dichloromethane was added dropwise in 15 minutes. The mixture was washed with 50 ml of water, dried with anhydrous sodium sulfate, and evaporated to remove dichloromethane. 43.4 grams (0.19 mol) of the residue was transferred into a 1 L round-bottom flask, diluted with 40 ml of DMF and cooled in an ice-salt bath. While stirring vigorously, 27.3 grams (0.18 mol) of l,8-Diazabicyclo[5.4.0]undec-7-ene (DBU) diluted with 50 ml of DMF was added dropwise in 15 minutes. To the mixture, 31.4 grams (0.18 mol) of 2 -hydroxy- 1 ,4- naphthoquinone was added, and the ice-salt bath was removed. While stirring vigorously and open in air, 34.5 grams (0.23 mol) of DBU diluted with 50 ml of DMF was added dropwise in 30 minutes at room temperature. After stirred for 4 hours, 500 ml of ice cooled water was added to the mixture. The crude product was filtered, washed with water, 5% aqueous sodium bicarbonate, water, 2% aqueous acetic acid solution, ice-cooled ethanol, successively. Pure product (14.6 grams, yield 36.5%) was obtained by crystallization in formic acid, and characterized by 1H NMR and mass spectrum. 1H NMR (in DMSO) δ 2.61(s, 3H), 7.91-7.95(m, 2H), 8.06(s, 1H), 8.13-8.17(m, 2H). Mass (M+H) is 241.

Example 2

Preparation of2-(l-hydroxyethyl)-naphtho[2,3-b]furan-4,9-dione (Compound V)

In a 250 ml beaker, 2 grams (8.3 mmoles) of 2-acetyl-naphtho[2,3-b]furan-4,9-dione (prepared in example 1) was dissolved in 40 ml of DMF with heating. To the solution with stirring, 1 gram (26.4 mmoles) of sodium borohydride in 10 ml of water was added. The mixture was stirred in open air for 30 minutes, then diluted by adding 250 ml of water. The resulting mixture was extracted with 100 ml of dichloromethane twice. The combined organic phase was washed with 200 ml of water, dried with anhydrous sodium sulfate, and evaporated to dryness. The residue was crystallized in ethyl acetate to yield 1.6 gram (6.6 mmoles) of pure product with overall yield 80%. Pure product was characterized by ^! H NMR and mass spectrum. ^! H NMR (in DMSO) δ 1.47(d, J=7, 3H), 4.88(m, 1H), 5.83(d, J=5, 1H), 6.91(s, 1H), 7.84-7.90(m, 2H), 8.06-8.1 l(m, 2H). Mass (M+H) is 243.

Example 3

Preparation of2-acetyl-4,9-bis(acetoxy)-naphtho[2,3-b]furan (Compound IV)

In a 500 ml round-bottom flask, 8 grams (33.3 mmoles) of 2-acetyl-naphtho[2,3-b]furan- 4,9-dione (prepared in example 1) was dissolved in 150 ml of DMF with heating. To the solution, added 14 ml of TEA, 8 grams of zinc powder, 1 gram of tetrabutylammonium bromide and 29 grams (166.7 mmoles) of sodium hydrosulfite. The mixture was sealed or isolated from air. Then 17 grams (166.7 mmoles) of acetic anhydride was added with syringe, and the resulting mixture had been stirred vigorously at room temperature for 3 hours. After addition of 300 ml of ethyl acetate, the reaction mixture was filtered, and the solid was washed with 200 ml of ethyl acetate. The filtrates were combined, extracted with 300 ml of ice-cooled aqueous 3% citric acid solution twice, and dried with anhydrous sodium sulfate. The organic phase was evaporated to dryness. The residue was washed with 60 ml of ice-cooled ethanol, and then filtered solid was crystallized in 250 ml of ethanol. 5.5 grams (16.9 mmoles, yield 50.7%) of product was obtained and characterized by ^! H NMR and mass spectrum. ^! H NMR (in CDCI ₃ ) δ 2.59(s, 3H), 2.62(s, 3H), 2.66(s, 3H), 7.50(s, 1H), 7.53-7.62(m, 2H), 8.00-8.03(m, 2H). Mass (M+H) is 327, Mass (M+Na) is 349.

Example 4

Preparation of2-acetyl-4,9-Bis(isobutoxy)-naphtho[2,3-b]furan (compound I) 9.41 grams (24.6 mmoles) of product was obtained from 8 grams (33.3 mmoles) of 2-acetyl- naphtho[2,3-b]furan-4,9-dione (prepared in example 1) and 26.4 grams (166.7 mmoles) of isobutyric anhydride instead of acetic anhydride by using the procedure described in example 3 with overall yield of 74.0%. Product was characterized by ^! H NMR and mass spectrum. ^! H NMR (in CDCls) δ 1.54(d, J=7, 6H), 1.56(d, J=7, 6H), 2.65(s, 3H), 3.1 1-3.20 (m, 2H), 7.43(s, 1H), 7.53-7.60(m, 2H), 7.99-8.02(m, 2H). Mass (M+H) is 383.

Example 5

Preparation of2-acetyl-4,9-Bis(pivaloxy)-naphtho[2,3-b]furan ( compound II)

8.37 grams (20.4 mmoles) of product was obtained from 8 grams (33.3 mmoles) of 2- acetyl-naphtho[2,3-b]furan-4,9-dione (prepared in example 1) and 20.1 grams (166.7 mmoles) of pivaloyl chloride instead of acetic anhydride by using the procedure described in example 3 with overall yield of 61.3%. Product was characterized by ^! H NMR and mass spectrum. ^! H NMR (in CDCI ₃ ) δ 1.59(s, 9H), 1.61(s, 9H), 2.65(s, 3H), 7.40(s, 1H), 7.51-7.61(m, 2H), 7.97-8.00(m, 2H). Mass (M+H) is 411.

Example 6

Preparation of2-acetyl-4,9-bis(octanoyloxy)-naphtho[2,3-b]furan (Compound III)

To an 1 L round-bottom flask, added 30 grams (125 mmoles) of 2-acetyl-naphtho[2,3- b]furan-4,9-dione (prepared as described in example 1), 300 ml of dimethylformide, 87.1 ml of triethylamine (625 mmol), 30 grams (470 mmol) of zinc powder, 3 grams of tetrabutylammonium bromide, 109 grams (625 mmol) of sodium hydrosulfite. The mixture was isolated from air by nitrogen atmosphere or by sealing from air, and stirred vigorously at room temperature for 20 minutes. Then 81.3 grams (500 mmoles) of caprylic chloride was added dropwise with syringe in 30 minutes, and the resulting mixture was stirred vigorously at room temperature for additional 3 hours. The reaction mixture was filtered, and the solid was washed with 50 ml of dimethylformide. To the combined filtrate, 1000 ml of 5% acetic acid aqueous solution was added, and the resulting mixture was stirred for 1 hour. The crude solid product was collected by filtration, washed with 200 ml of water twice, crystallized in ethanol and re- crystallized in acetone/water (8: 1). 15.0 grams (30.4 mmoles, yield 24.3%) of product was obtained and characterized by 1H NMR. 1H NMR (in CDC1 ₃ ) δ 0.93-0.97(m, 6H), 1.37- 1.39(m, 9H), 1.42-1.47(m, 4H), 1.51-1.59(m, 3H), 1.90-2.00 (m, 4H), 2.65(s, 3H), 2.83-2.91 (m, 4H), 7.46(s, 1H), 7.51-7.61(m, 2H), 7.99-8.02(m, 2H).

Example 7

Biological Assays

Cell Culture: 5-FU resistance BEL7404, regular BEL7404, doxorubicin resistance MCF7, regular MDA-231 , taxol resistance A2780, and regular sk-ov3 cells were maintained in Dulbecco's Modified Eagle Medium (DMEM) (imported from Invitrogen, Carlsbad, CA, USA) supplemented with 10% fetal bovine serum (FBS) (Si Ji Qing, Hangzhou, China) and 1% penicillin/streptomycin/amphotericin B (imported from Invitrogen, Carlsbad, CA, USA).

Cell Viability Determination: Popular MTT method {Archives of Biochemistry and Biophysics, 1993, 303: 474-482) was used to screen the in vitro effects of the compounds of formula II and III, 5-FU, doxorubicin, taxol. Briefly, 5000 to 10000 cells were inoculated per well in a 96-well plate. After overnight incubation, a compound of formula II or III was added to the wells at the final concentrations of 10μΜ, 5μΜ, 2.5μΜ, 1.25μΜ, or ΙμΜ, 0.75μΜ, 0.5μΜ and 0.25 μΜ in complete culture medium; 5-FU was added to the wells at the final concentrations ranged from ΙμΜ to 10 mM; doxorubicin was added to the wells at the final concentrations ranged from 50 nM to 500 μΜ; and taxol was added to the wells at the final concentrations ranged from 15 nM to 40 μΜ. Each dose level covered 4 equivalent wells. After 48 hour incubation, one tenth volume of 5 mg/mL MTT (thiazolyl blue tetrazolium bromide, Sigma- Aldrich) stock solution was added, and incubation was continued for 2 hours. Then medium was removed and 100 \L of isopropanol solution comprising 86% isopropanol, 4% aqueous 1 N HCl and 10% aqueous SDS solution (10% in concentration) was added. The absorbance of each well at 570 nm wavelength was measured by a micro-plate reader after gentle shaking for 20 minutes. Drug concentrations of 50% cell viability (IC50) were calculated by LOGIT method.

Test Results : Compounds I, III, IV, V, and VI were tested for their activity against regular cancer cell lines and multidrug resistance (MDR) cancer cell lines, along with 5-FU, taxol, and doxorubicin. The test results are listed in the following tables.

5-FU O.lm M 2.4m M 2.5 μ M 2.5 μ M

TAXOL 10.0 μ M 20.7 μ M 50n M 68n M

DOXORUBICIN 60.0 μ M 60.0 μ M 310n M 370n M

Doxorabicin resistance Regular MDA-231 MCF7

IC50 in first IC50 in IC50 in first IC50 in test second test test second test

Compound I

4.0 μ M 4.0 μ M 4.5 μ M 4.5 μ M

Compound III

5.3 μ M 4.0 μ M 4.5 μ M 5.6 μ M

Compound IV

1.06 μ M 0.6 μ M 1.3 μ M 1.5 μ M

Compound V

2.5 μ M 4.7 μ M 5.6 μ M 3.5 μ M

Compound VI 1.0 μ M 0.8 μ M 1.5 μ M 1.5 μ M

5-FU 6.2m M 4.0m M 15.3 μ M 16.4 μ M

TAXOL 40.0 μ M 10.0 μ M 15n M 45n M

DOXORUBICIN 250 μ M 125 μ M 0.5 μ M 0.5 μ M

Compound I 1.5μ M 1.5μ M 4.0 M 4.0 M

Compound III 1.6μ M Ι. Ιμ Μ 5.4μ M 5.6μ M

Compound IV 1.0μ M 2.5μ M 3.0μ M 2.5μ M

Compound V 2.7μ M 6.8μ M 5.7μ M 8.9μ M

Compound VI 1.0μ M 1.0μ M 1.8μ M 1.3μ M

5-FU 250 μ M 250 μ M 22.3μ M 8. Ομ M

TAXOL 20.0μ M 20.0μ M ΙΟΟηΜ 50nM

DOXORUBICIN 60.0μ M 60.0μ M 130nM 60nM