WO2000066127A1 - Novel highly lipophilic camptothecin analogs - Google Patents

Abstract

Novel analogs of Camptothecin are disclosed. The analogs include various 'A' and 'B' ring substitutions and/or a 7-membered 'E' ring, and include mono- and multi-substituted analogs of Camptothecin. One or more of the substitutions preferably includes a silicon atom in the fragment moiety, and the compounds are highly lipophilic and possessed of high 'E' ring stability.

Description

NOVEL HIGHLY LIPOPHILIC CAMPTOTHECIN ANALOGS

FIELD OF THE INVENTION

This invention relates to novel and useful compositions that are structurally related to the Camptothecins . The compositions of this invention include a seven-membered lactone ^ΛE' ring and/or ^ΛA' and ^ΛB' ring multiple substitutions. The invention also includes pharmaceutical formulations of the new compositions, methods of treating various cancers and leukemias by administering an effective amount of the compositions to a patient, and processes for synthesizing the compositions from naturally occurring Camptothecin, as well as by total synthesis.

BACKGROUND OF THE INVENTION

Camptothecin is a well-known naturally occurring compound that was discovered to possess anticancer properties by Wall and Wani in the early 1960s. Efforts have been made since then to improve upon the antineoplastic properties of Camptothecin and its analogs, to overcome certain clinical and pharmaceutical limitations, and to reduce the unwanted toxicities of this series of agents. Camptothecin and many of its analogs are very poorly soluble in water. Many such analogs exhibit water solubility of less than five micrograms per milliliter. This poor water solubility originally presented problems of administration of the intended drug, and efforts have continued towards making the drug practical for administration to human patients.

These early efforts involved the formulation of Camptothecin analogs with sodium hydroxide, in which the compounds were readily soluble. Unfortunately, these formulations caused the opening of the lactone ^XE' ring of the analog, which resulted in both reduced antineoplastic activity and higher unwanted toxicity upon administration.

Another avenue of exploration has been the development of Camptothecin analogs that exhibited improved water solubility. Compounds which have resulted from this research include the

FDA approved drugs Irinotecan (Camptosar , CPT-11) and

Topotecan (Hycamtin ) , and analogs in clinical trials and

under development, such as DX8951 and 9-nitro camptothecin, and others . Improving the water solubility of Camptothecin analogs improves the ease of administration of the drug to patients . However, especially in the case of Irinotecan, the compound is administered is a pro-drug which requires metabolic activation in vivo to the active species (SN38) . In addition, these water-soluble analogs, and other camptothecin analogs are rapidly converted from the active E' ring lactone form to the inactive and toxic carboxylate form in plasma.

The inventors of the present application have directed recent efforts in discovering and developing analogs of Camptothecin that are highly lipophilic and poorly water- soluble. Several of these analogs are disclosed in United States Patent 5,910,491, and in United States Patent Application 09/022,310, filed February 11, 1998.

Poorly water-soluble Camptothecin analogs are formulated for administration with suitable solvents such as those disclosed in United States Patents 5,726,181; 5,447,936; 5,468,754; and others referred to in the Information Disclosure Sheet that accompanies this application. Preferred solvents for these poorly water-soluble Camptothecin analogs include dimethylacetamide (DMA), dimethylisosorbide (DMI) and N-methylpyrrolidinone (NMP) .

The poorly water-soluble Camptothecin analogs generally provide increased lactone stability and greater antitumor activity than the water-soluble analogs . Some analogs are also less susceptible to metabolism, particularly to the glucuronide form, which is frequently associated with the unwanted toxicities of Camptothecin analogs .

SUMMARY OF THE INVENTION The novel Camptothecin compositions of this invention are

of the following formula I :

( I )

wherein :

R and Ri are each individually hydrogen, lower alkyl, lower alkenyl, lower alkynyl, alkoxy, halo, aryl, arylalkyl, arylalkenyl, arylalkynyl, -Xι~ (C₀-C₆ alkylene, Cι-C₆ alkenylene or C2~C₆ alkynylene) -SiRi2 ι₃ i4, -Xι^~ (C₀-C₆ alkylene, Ci-Cβ alkenylene, C₂-C₆ alkynylene, phenylene or benzylene) -NR₉R₁₀, or OR₆ ;

^R ₂ R₃ R , and R5 are each individually hydrogen, lower alkyl, lower alkenyl, lower alkynyl, alkoxy, halo, aryl, arylalkyl, arylalkenyl, arylalkynyl, amino, nitro, protected amino, -X₂-(C₀-C₆ alkylene, Ci-Cδ alkenylene or C₂-C6 alkynylene) -SiRι₂Rι₃Ri4, -X₂- (C₀-C₆ alkylene, Cι-C₆ alkenylene, C₂-C6 alkynylene, phenylene or benzylene) -NR_9aRιo_a, or ORa, wherein at least one of R₂, R₃ and R₄ is other than hydrogen; and wherein when Ri is hydrogen, lower alkyl, lower alkenyl, lower alkynyl, alkoxy, halo, aryl, arylalkyl, arylalkenyl or arylalkynyl, then one or more of R₂, R₃ and R₄ is -X₂- (Co-C₆ alkylene, Cι-C₆ alkenylene or C₂-C6 alkynylene) -SiRι₂Rι₃Ri4; R₆ is hydrogen, lower alkyl, or an oxygen-protecting group;

R is hydrogen, lower alkyl, aryl, -SiRi2Rι₃Ri4, or is absent when Rn is hydrogen;

Re is hydrogen, lower alkyl or -(C₀-C₆ alkylene, Co-C₆ alkenylene or C₀-C₆ alkynylene) -SiRi2Rι₃Ri4;

Rg, Rio, Rg_a and Rιo_a are each individually hydrogen, lower alkyl or a nitrogen-protecting group;

Rii is hydrogen, carbonyl, sulfonyl, thiocarbonyl, sulfoxo, C₁-C₁₆ alkylene-, -0- or -S-; R12, R1₃, and R_i4 are each individually hydrogen or C₁-C₁₀ alkyl;

R15 is hydrogen, lower alkyl or a nitrogen-protecting group;

X is -CH₂- or absent; X_x and X₂ are each individually sulfur, NR₁₅ or absent; or a pharmaceutically acceptable salt thereof.

The compounds of this invention are useful in treating various cancers and leukemias. They have demonstrated particularly potent activity, both in vi tro and in vivo, against several different solid tumors, including but not limited to cancers of the colon, breast, pancreas, stomach, kidneys, liver, prostate, testis, lung, brain, malignant melanoma, and others. The compounds are preferably formulated for administration to a patient. The formulations are designed for either oral, topical, or parenteral administration, and include one or more pharmaceutically acceptable solvents, excipients and/or diluents combined with the formula I compound (the "active compound") .

Accordingly, it is an object of this invention to provide for novel Camptothecin compositions.

Another object of this invention is to provide for Camptothecin compositions that possess enhanced antineoplastic properties.

Another object of this invention is to provide for novel formulations of Camptothecins .

Another object of this invention is to provide for novel methods of treating antineoplastic diseases, especially cancers and leukemias .

Other objects of this invention will become apparent upon a reading of the following description. DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments herein described are not intended to be exhaustive, or to limit the invention to the precise forms disclosed. They are chosen and described to best illustrate the principles of the invention, and its application and practical use to best enable others skilled in the art to follow its teachings.

DEFINITIONS

"Scaffold" means the fixed structural part of the molecule of the formula given.

"Fragments" or "Moieties" are the variable parts of the molecule, designated in the formula by variable symbols, such as R_x, X or other symbols. Fragments may consist of one or more of the following:

"C_x-C_y alkyl" means a straight or branched-chain aliphatic hydrocarbon containing as few as x and as many as y carbon atoms. Examples include "Cι-C₆ alkyl" (also referred to as "lower alkyl"), which includes a straight or branched chain hydrocarbon with no more than 6 total carbon atoms, and Cι-Cτ_.6 alkyl, which includes a hydrocarbon with as few as one up to as many as sixteen total carbon atoms, and others;

"Cχ-C_y alkylene" means a bridging moiety formed of as few as "x" and as many as "y" -CH₂- groups; "C_x-C_y alkenyl or alkynyl" means a straight or branched chain hydrocarbon with at least one double bond (alkenyl ) or triple bond (alkynyl) between two of the carbon atoms;

"C_x-C_y alkoxy" means a straight or branched hydrocarbon chain with as few as x and as many as y carbon atoms, with the chain bonded to the scaffold through an oxygen atom;

"Alkoxycarbonyl" (aryloxycarbonyl) means an alkoxy (aryloxy) moiety bonded to the scaffold through a carbonyl;

"Halogen" or "Halo" means chloro, fluoro, bromo or iodo; "Acyl" means -C(0)-R, where R is hydrogen, C_x-C_y alkyl, aryl, C_x-C_y alkenyl, C_x-C_y alkynyl, etc.;

"Acyloxy" means -0-C(0)-R, where R is hydrogen, C_x-C_y alkyl, aryl, etc.;

"C_x-C_y Cycloalkyl" means a hydrocarbon ring or ring system consisting of one or more rings, fused or unfused, wherein at least one of the ring bonds is completely saturated, with the ring(s) having from x to y total carbon atoms;

"Aryl" means an aromatic ring or ring system consisting of one or more rings, preferably one to three rings, fused or unfused, with the ring atoms consisting entirely of carbon atoms;

"Arylalkyl" means an aryl moiety as defined above, bonded to the scaffold through an alkyl moiety (the attachment chain) ; "Arylalkenyl" and "Arylalkynyl" mean the same as "Arylalkyl", but including one or more double or triple bonds in the attachment chain;

"Heterocycle" means a cyclic moiety of one or more rings, preferably one to three rings, fused or unfused, wherein at least one atom of one of the rings is a non-carbon atom. Preferred heteroatoms include oxygen, nitrogen and sulfur, or any combination of two or more of those atoms; and

"Substituted" modifies the identified fragments (moieties) by replacing any, some or all of the hydrogen atoms with a moiety (moieties) as identified in the specification.

"Protecting groups" are those moieties which are attached to a particular atom, and which prevent reaction at that position of the scaffold under specified conditions. Examples of the above moieties are as follows :

Ci-Cε alkyl includes methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, amyl and the like;

C₂-Cβ alkenyl or alkynyl includes vinyl, propenyl, butenyl, acetylenyl, propynyl, and other like moieties with one or more double and/or triple bonds;

Alkoxy includes methoxy, ethoxy, propoxy, and the like;

Alkoxycarbonyl and aryloxycarbonyl include methoxycarbonyl, ethoxycarbonyl, benzoxy and others; Acyl includes formyl, acetyl, propionyl, benzoyl and others;

Acyloxy includes formoxy, acetoxy, propionoxy, and the like; Cycloalkyl includes cyclopropyl, cyclobutyl, cyclohexyl, indanyl, dihydronaphthalenyl, cyclohexenyl, and the like;

Aryl includes phenyl, naphthyl and anthracenyl, as well as substituted variants wherein one of the hydrogen atoms bonded to the ring atom is substituted by a halogen atom, an alkyl group, or another moiety;

Arylalkyl includes benzyl, phenethyl, and the like;

Arylalkenyl and arylalkynyl includes phenylvinyl, phenylpropenyl, phenylethylenyl, phenylpropynyl and the like; and Heterocycle includes furanyl, pyranyl, thionyl, pyrrolyl, pyrrolidinyl, prolinyl, pyridinyl, pyrazolyl, imidazolyl, triazolyl, tetrazolyl, oxathiazolyl, dithiolyl, oxazolyl, isoxazolyl, oxadiazolyl, pyridazinyl, pyrimidinyl, pyrazinyl, piperazinyl, oxazinyl, thiazolyl, and the like. Substitutions for hydrogen atoms to form substituted analogs include halo, alkyl, nitro, amino (also N-substituted, and N,N di-substituted amino), sulfonyl, hydroxy, alkoxy, phenyl, phenoxy, benzyl, benzoxy, benzoyl, and trifluoromethyl . Protecting groups include specific moieties for protecting, in particular, nitrogen terminal moieties and oxygen terminal moieties . Protecting groups are well known in the art and are described in detail in Kocienski , P. , Protecting Groups, Foundations of Organic Chemistry (Thieme, 1994); and Greene, Wuts , Protective Groups in Organic Synthesis (Wiley, 2d ed. 1990) .

The compounds of this invention are semisynthetic analogs of Camptothecin. In particular, the compounds have either a seven-membered ^ΛE' ring and/or di- and tri-substituted analogs derived from the Camptothecin scaffold. The analogs are of formula I, depicted below. It should be noted, that for purposes of this invention, the numbering scheme used to identify the CPT scaffold is as shown below. The rings are lettered from left to right across the scaffold.

(I)

wherein : R and Ri are each individually hydrogen, lower alkyl, lower alkenyl, lower alkynyl, alkoxy, halo, aryl, arylalkyl, arylalkenyl, arylalkynyl, ~Xχ- (C₀-C₆ alkylene, Cι-C₆ alkenylene or C₂-C₆ alkynylene)

-Xι-(C₀-C₆ alkylene, Cι-C₆ alkenylene, C₂-C₆ alkynylene, phenylene or benzylene) -NRgRio, or

OR₆ ; R_2? R_{3A 4}; and R₅ are each individually hydrogen, lower alkyl, lower alkenyl, lower alkynyl, alkoxy, halo, aryl, arylalkyl, arylalkenyl, arylalkynyl, amino, nitro, protected amino, -X₂- (Co-C₆ alkylene, Ci-Cβ alkenylene or C₂-C_e alkynylene) -SiRι₂Rι₃Ri4, -X₂- (C₀-C₆ alkylene, Cι-C₆ alkenylene, C₂-C₆ alkynylene, phenylene or benzylene) -NR_9aRι_0a, or OR₈, wherein at least one of R₂, R₃ and R₄ is other than hydrogen; and wherein when Ri is hydrogen, lower alkyl, lower alkenyl, lower alkynyl, alkoxy, halo, aryl, arylalkyl, arylalkenyl or arylalkynyl, then one or more of R₂, R₃ and R is -X₂- (C₀-C₆ alkylene, Cι-C₆ alkenylene or C2-C6 alkynylene) -SiRι₂Rι₃Ri4;

R_δ is hydrogen, lower alkyl, or an oxygen-protecting group;

R₇ is hydrogen, lower alkyl , aryl , -SiRι Ri3Ri4 r or is absent when R_n is hydrogen;

R₈ is hydrogen , lower alkyl or - ( C₀-C₆ alkylene , C₀-C₆ alkenylene or C₀-C6 alkynylene ) -SiRi2Rι₃Ri4 ;

R₉, Rio , R_9a and Rι_0a are each individually hydrogen, lower alkyl or a nitrogen-protecting group ; Rii is hydrogen, carbonyl, sulfonyl, thiocarbonyl, sulfoxo, C1-C1₆ alkylene-, -0- or -S-; i₂, R_I3Λ and Rχ are each individually hydrogen or C1-C10 alkyl; R₁₅ is hydrogen, lower alkyl or a nitrogen-protecting group;

X is -CH₂- or absent;

Xi and X₂ are each individually sulfur, NR₁₅ or absent; or a pharmaceutically acceptable salt thereof.

The formula I preferred compounds include those compounds wherein Ri is -X- (lower alkyl) -Si (alkyl ) ₃ and one or more of the ^λA' ring moieties is other than hydrogen. This formula produces various di- and tri-substituted analogs of naturally occurring Camptothecin. The presence of one or more silane moieties on the scaffold enhances the high lipophilicity of the compound, and stabilizes the lactone ^ΛE' ring.

Preferred Rn moieties include hydrogen and lower alkylene, with preferred R₇ moieties including any silane moiety when R is lower alkylene.

Most preferred compounds include those compounds where Ri is a -lower alkyl-silane moiety, one or two of R₂ through R₄ is amino, substituted amino, hydroxy, alkoxy, -carbonyl-lower alkyl-heterocycle, -lower alkyl-trimethylsilyl, or aryloxy, R₅ is hydrogen, and Rn is hydrogen. Preferred formulations of formula I compound are disclosed in United States Patents 5,447,936; 5,726,181, and related patents and applications assigned to BioNumerik

Pharmaceuticals, Inc., all of which are incorporated herein by reference. The principal solvent in the formulation is N- methylpyrrolidinone (NMP) or dimethylacetamide (DMA) or dimethylisosorbide (DMI). The preferred formulation also includes one or more pharmaceutically acceptable excipients, co-solvents, diluents or fillers as described in the prior patents. Formulations may be adapted for oral, topical, or parenteral administration as required.

The invention also includes methods of treating susceptible cancers by administering an effective amount of the formula I compound to a patient in need of treatment. Effective amounts of the formula I compound depend upon the type and stage of the cancer being treated, ranging from 0.01 mg/m² to about 50 mg/m². Most preferred doses range from 0.2 mg/m² up to about 10 mg/m². Administration may be through oral or parenteral routes, most preferably intravenous infusion or by oral administration.

The following schemes illustrate synthetic processes employed in the making of certain of the formula I compounds. Other synthetic processes can be derived from the schemes and the accompanying examples to enable synthesis of all of the formula I compounds . Scheme 1

Scheme 1 illustrates the preferred process for synthesizing the seven-membered ^ΛE' ring analogs from naturally occurring Camptothecin. Processes for synthesizing the A' and ^ΛB' ring substituted analogs are disclosed in United States Patent 5,910,491 and US Patent Application 09/178,780, both of which are incorporated herein by reference .

As shown in the scheme, naturally occurring Camptothecin 1 is converted to the open ^ΛE' ring carboxylate salt by adding excess base to the solution. Treating Camptothecin 1 with acetic anhydride in the presence of excess base forms the desired acetate ester 2. Acid chloride intermediate 3 is derived by reacting intermediate 2 with a corresponding acid chloride, and then to the diazoketone 4 by reacting 3 with diazomethane .

Diazoketone 4 is converted to the corresponding ester 5 via a Wolff-Hoffman rearrangement. The ester 5 is then hydrolyzed to its free acid. The ^λE' ring is then closed by acidification to form the 7-membered ^λE' ring compound 6, which is a formula I compound.

Scheme la

Scheme la depicts an alternative and known process for synthesizing the 7-membered E' ring compound of formula I. This known process is described in detail in Lavergne , et . al . , Homocamptothecins : Synthesis and Antitumor Activity of Novel E-Ring-Modified Camptothecin Analogues, J. Med. Chem. 1998, 41, 5410-5419. Specific examples of the process are described in the publication, which is attached to the Information Disclosure Sheet accompanying this application, and is incorporated herein by reference.

Schemes 2-5 depicted below illustrate the derivatization of the A and B rings, and the specific processes and examples are shown in the above-mentioned patents and patent applications, which have been incorporated herein by reference .

Scheme 2

Scheme 3

Scheme 4

Scheme 5

Scheme 6

Scheme 6 depicts the conversion of underivatized CPT to 9-Bromo CPT by selective nitration, amination and protection, and finally bromination and deamination. Nitration of underivatized Camptothecin yields a mixture of 9-nitro and 12- nitro CPT. The 9-nitro CPT can be derivatized to 9-Bromo CPT by direct amination and then bromination by known methods .

12-Nitro CPT is separated from the 9-Nitro CPT by flash column chromatography using ethyl acetate as an eluent. Amination of the 12-Nitro CPT is effected by hydrogenation using platinum oxide as catalyst. Protection of the 12-Amino CPT is achieved by reacting with a suitable acid chloride. Bromination is then accomplished with the sole substitution at the para-position by adding elemental bromine to the protected 12-Amino CPT. Deprotection and deamination is accomplished by adding a strong acid followed by sodium nitrite to remove the 12-Amino group and yield pure 9-Bromo CPT.

Scheme 7

Scheme 7 illustrates the conversion of 9-Hydroxy CPT to 9-Bromo CPT. This conversion is through a known process, in which the 9-Hydroxy CPT is first aminated, then brominated. The process is disclosed in several publications of record, and involves aminating the 9-Hydroxy CPT by adding concentrated nitric acid, then hydrogenating, and finally adding elemental bromine to displace the 9-Amino group.

Scheme 8

Scheme 8 illustrates the conversion of the 9-Bromo CPT intermediate (10) to the 9-Silyl analogues (13) of this invention. In these analogues, where the trimethylsilyl is attached directly to C9, the transformation is preferably achieved by reacting intermediate (10) with hexamethyldisilane and methyl lithium, converted to an organic soluble homogenous cuprate reagent according to the principles of Nyori . Where one or more alkylene groups bridge the trimethylsilyl moiety (preferred) , the transformation is preferably accomplished by reacting intermediate (10) with a tributyltin analogue of the respective trimethylsilyl hydrocarbon using palladium chemistry techniques. This process is similar to the process for adding C7 substitutions, as disclosed in U. S. Patent 5,910,491, incorporated herein by reference .

10-substituted analogues (as well as the 10,7- disubstituted analogues) are formed by first triflylating a 10-hydroxy Camptothecin analogue, then performing the silylation through a modified Stille coupling. This process is also disclosed in the prior art.

The following specific examples illustrate synthetic processes for preparing some of the formula I compounds.

These examples are illustrative only and are not intended to limit the scope of the invention in any way. Processes described for synthesis of homocamptothecin derivatives apply equally to processes used to synthesize the same derivatives of camptothecin.

EXAMPLE 1 Camptothecin diol (Scheme la)

Camptothecin (3 gm, 8.6 mmols) is recrystallized from hot dimethyl formamide suspended in methanol (10 ml) and sodium borohydride (1 gram, 26.3 mmols) is added. The reaction mixture is stirred at room temperature overnight. The reaction mixture is concentrated to one-third volume and crushed ice added to precipitate the product. The product is then filtered and washed with ether, dried under vacuum and analyzed. Since the product is found substantially pure, it is taken over to the subsequent step without further purification. 23

¹H NMR: δ 0.83 (3H,t, J= 7.8 Hz) , 1.63 (2H, q, J= 7.2 Hz) , 2.41

(IH, s) , 4.46 (2H, q, J= 17.1 Hz) , 4.83 (IH, s) , 4.92 (IH, d,

J= 4.8Hz) , 5.13 (2H, s) , 6.66 (IH, d, J= 4.5 Hz) , 7.28 (IH, s) , 7.56 (IH, t, J= 7.5 Hz) , 7.72 (IH, t, J= 7.5 Hz) , 8.04 (2H, d, J= 7.8 Hz) , 8.45 (IH, s)

EXAMPLE 2 3- (3-formyloxymethyl-3- (4-oxo-4, 6-dihydroindolizino [l,2-b]quinolin-2-yl) -2-propanone

A portion of the diol (300 mg) obtained from the previous step is dissolved in acetic acid (15 ml) and sodium periodate (300 mg) is added to the stirred solution. The reaction mixture is then stirred for 48 hours. Crushed ice is added to precipitate the product. The wet product is washed with additional amounts of water followed by ether. The crude product is then dried over high vacuum and analyzed.

^XH NMR: δ 1.20 (3H,t, J= 7.8 Hz), 2.9 (2H, q, J= 7.2 Hz), 5.28 (IH, d, J= 4.8Hz), 7.19 (2H, s), 7.25 (IH, s), 7.56 (IH, t, J= 7.5 Hz), 7.72 (IH, t, J= 7.5 Hz), 7.81 (IH, d, J= 7.8 Hz), 8.02 (IH, t, J= 3 Hz), 8.16 (IH, d, J= 7.8 Hz), 8.35 (IH, s)

EXAMPLE 3 t-butyl-3-hydroxy-3- (3-hydroxymethyl-4-oxo-4 , 6-

dihydroindolizino [1, 2-b] quinolin-2-yl) pentanoate

A suspension of zinc (3.25 g, 50 mmol) is stirred in

anhydrous ether (25 ml) under argon. A few drops of

chlorotrimethyl silane are then introduced to activate the

zinc dust. Stirring was continued at room temperature for an

additional 15 minutes and then heated to reflux. While reflux

is continued at constant rate tert-butyl bromoacetate (7.5 ml, 50 mmols) was added. Heating was continued for an additional I

hour. The resulting ethereal solution is allowed to cool to room temperature. It was then cannulated into the above formyloxy mappicine ketone (0.8 g, 2.35 mmols) in anhydrous THF. The reaction is stirred for an additional one hour, then quenched with ammonium chloride. The organic portion is extracted out using chloroform. The organic fraction is dried

over anhydrous sodium sulfate, filtered and concentrated. The

crude product is purified using a silica gel column.

IH NMR: δ 0.8 (3H, t), 1.22 (9H,s), 1.97 (2H, m) , 2.91 (2H,

dd) , 4.79 (IH, s) , 4.87 (2H, dd) , 5.27 (IH, s) , 7.35 (IH, s),

7.7 (IH, t), 7.86 (IH, t), 8.12 (IH, d) , 8.16 (lH,d), 8.67

(IH, s)

EXAMPLE 4 Homocamptothecin

Homocamptothecin was prepared according to the process disclosed in Lavergne , et al , Homocamptothecins : Synthesis and Antitumor Activity of Novel E-Ring-Modified Camptothecin Analogues, J. Med. Chem., 1998, vol. 41, p. 5414.

EXAMPLE 5 7-trimethylsilylethyl homocamptothecin

90 mg of homocamptothecin was dissolved in 4.5 mL of water, to which had been added 1.8 mL of concentrated sulfuric acid and 400 mg of iron sulfate heptahydrate . 2.0 mL of glacial acetic acid and 0.2 mL of 3-trimethylsilyl-propanal were then added and the reaction mixture stirred for 6 hours, and monitored by TLC (5% methanol-chloroform) . The aqueous fraction was concentrated with brine, extracted with dimethyl ether (200 mL x 3) and dried over anhydrous sodium sulfate. The pale yellow solid obtained was chromatographed over silica gel to obtain the title compound.

^XH NMR (CDC1₃, 300 Hz): δ 8.04 (d, 1 H, J = 8.1 Hz), 7.91 (d, 1 H, J = 8.4 Hz), 7.72 (t, 1 H, J = 7.2 Hz), 7.57 (t, 1 H, J = 7.8 Hz), 7.53 (s, 1 H) , 5.70 (d, 1 H, J = 15.3 Hz), 5.36 (d, 1 H, J = 15.6 Hz), 5.18 (m, 2 H) , 3.47 (d, 1 H, J = 13.5 Hz), 3.22 (d, 1 H, J = 13.8 Hz), 3.04 (dd, 2 H, J = 12.6, 5.1 Hz), 2.04 (m, 2 H) , 1.00 (t, 3 H, J = 7.5 Hz) , 0.91 (dd, 2 H, J =

12.5, 5.7Hz) , 0.20 (s, 9 H) ppm.

¹³C NMR (300 MHz, DMSO) 5172.5, 159.7, 156.3, 152.7, 149.2, 147.4, 145.7, 130.5, 128.1, 128.0, 126.8, 124.4, 123.0, 100.1, 73.6, 61.9, 50.2, 42.9, 36.9, 23.8, 17.6, 8.9, -1.18 ppm

MS (M+l) 463.2

EXAMPLE 6 (2' -trimethylsilyl-9-ethynyl) -20 (S) -Camptothecin

9-Bromo Camptothecin (60 mg, 0.14 mmol) and diisopropylethyl amine (0.5 mL) in 1 mL of toluene are dried over 4 A° powdered molecular sieves at room temperature for 14 hours. Copper iodide (Cul, 2 mg, 0.011 mmol), dichlorobis ( tri- o-tolylphosphine) palladium (II) (6 mg, 0.0076 mmol) and trimethylsilylacetylene (56 uL, 0.42 mmol) are added. The resultant mixture is stirred at 60 °C for 72 hours. Once the reaction is completed, the reaction mixture is diluted with chloroform (5 mL) and water (5 mL) . The aqueous phase is extracted with chloroform (3 X 5 mL) . The combined organic extracts are then washed with brine, dried over anhydrous sodium sulfate, filtrated through silica gel, and concentrated by rotary evaporator. The crude product is purified by preparative TLC using 3% MeOH/CHCl₃ as eluents to yield the title compound (19 mg) as a yellow solid: mp, 250 °C dec;

¹H NMR (300 MHz, DMSO) δ8.87 (s, 1 H) , 8.21 (d, 1 H, J = 8.1

Hz), 7.91 - 7.81 (m, 2 H) , 7.36 (s, 1 H) , 6.54 (s, 1 H) , 5.43 (s, 2H) , 5.38 (s, 2 H) , 1.94 - 1.81 (m, 2 H) , 0.89 (t, 3 H, J =

7.2 Hz), 0.36 (s, 9 H) ; ¹³C NMR (300 MHz, DMSO) 6172.5, 156.8,

153.3, 150.0, 147.6, 145.1, 132.1, 131.3, 130.6, 130.0, 129.4, 127.9, 120.5, 119.5, 101.4, 100.9, 97.0, 72.4, 65.3, 50.7, 30.3, 7.8, -0.070 ppm. HRMS exact ma.ss calcd. for C25H24 ₂0_ιSi 444.1505, found 444.1506

EXAMPLE 7 9-Trimethylsilylmethyl Camptothecin

9-Bromo Camptothecin (75 mg, 0.176 mmol) and freshly prepared tetrakis (triphenylphosphine) palladium (14 mg, 0.012 mmol, 7%) are taken in an oven-dried 100 mL flask. 2.0 mL Hexamethylphosphoramide is added. The mixture was stirred under argon for thirty minutes. Trimethylsilylmethyl-tributyltin (0.15 mL, 0.59 mmol) is then injected into the reaction mixture. The reaction mixture is heated to 115 °C for 48 hours under argon, cooled to room temperature. 10 mL water is then added and extracted with chloroform. The organic portion is then washed with water and dried with anhydrous sodium sulfate. The solvent is removed in va cuo . Residue was purified by column chromatography, using hexane and ethyl acetate 1:1 as eluent. 18 mg of 9-Trimethylsilylmethyl Camptothecin was isolated, 24% yield.

^λE NMR (CDC1₃) δ 8.48 (IH, s), 7.98 (IH, d, J = 8.4

Hz), 7.69 (IH, dd, J = 8.4, 7.2 Hz), 7.67 (IH, s), 7.30 (IH, d, J = 7.2 Hz), 5.72 (IH, d, J = 16.5 Hz), 5.30 (2H, s), 5.28 (IH, d, J = 16.5 Hz), 3.73 (IH, s), 2.62 (2H, s), 1.87 (2H, m) , 1.04 (3H, t, J = 7.2 Hz), 0.01 (9H, s).

¹³C NMR (CDCI₃) δ 174.2, 157.9, 152.0, 150.3, 149.8,

146.8, 138.4, 130.4, 128.1, 127.4, 126.6, 118.6, 98.1, 72.9, 66.6, 50.4, 31.8, 29.9, 23.6, 8.0, -1.1.

EXAMPLE 8 9- (2' -Trimethylsilylethyl) -20 (S) Camptothecin

To a solution of 9- (2' -trimethylsilylethynyl) -20 ( S) - Camptothecin (3.0 mg) in ethanol (1 mL) is added palladium (5% on charcoal, 1 mg) under Argon. The mixture is purged with hydrogen several times. Then, the mixture is stirred at room temperature for 14 hours under hydrogen (1 atm) . The mixture is filtrated through silica gel, and concentrated by rotary evaporator. The crude product was purified by radial PLC using 5% MeOH/CHCl₃ as eluents to give 9- (2' -trimethylsilylethyl) - 20 (S) Camptothecin (2.0 mg) as a yellow solid: mp, 250 °C dec;

¹R NMR (300 MHz, DMSO) δ8.84 (s, 1 H) , 8.01 (d, 1 H, J = 8.4

Hz), 7.77 (dd, 1 H, J = 7.2, 8.4 Hz), 7.58 (d, 1 H, J = 6.3 Hz), 7.34 (s, 1 H) , 6.52 (s, 1 H) , 5.43 (s, 2 H) , 5.31 (s, 2

H) , 3.17 - 3.09 (m, 2 H) , 1.94 - 1.81 (m, 2 H) , 1.03 - 0.94 (m, 2 H), 0.89 (t, 3 H, J = 7.2), 0.086 (s, 9 H) ;

¹³C NMR (300 MHz, DMSO) δl72.6, 156.9, 152.1, 150.0, 148.5,

145.6, 142.1, 130.1, 129.7, 127.9, 127.4, 126.3, 119.0, 96.6, 72.4, 65.3, 50.5, 30.3, 26.3, 17.8, 7.8, -1.6 ppm.

EXAMPLE 9 12-Amino Camptothecin

Nitration of Camptothecin in nitric acid and concentrated sulfuric acid gave the majority of 12-nitro camptothecin. 12- Nitro camptothecin is purified by flash column chromatography using ethyl acetate as eluent.

12-Nitro Camptothecin (1.61g, 4.1 mmol) is dissolved in 300 mL dioxane and 100 mL ethanol. The catalyst, platinum dioxide (0.17g) is then added, and hydrogen was bubbled into the reaction mixture for four hours under vigorous stirring. The reaction was monitored by TLC. Additional dioxane was added to dissolve less soluble product. Catalyst is then 30

filtered using a sintered funnel. Organic solvents are removed by vacuum to get 1.25g 12-amino camptothecin, 84% yield.

¹H NMR (DMSO-d₆) δ 8.42 (IH, s), 7.41 (IH, s), 7.34 (IH, dd, J

= 8.1 7.5 Hz), 7.10 (IH, d, J = 8.1 Hz), 6.89 (IH, d, J = 7.5 Hz), 6.48 (IH, s), 6.17 (2H, s), 5.39 (2H, s), 5.21 (2H, s), 1.83 (2H, ) , 0.85 (3H, t, J = 7.5 Hz).

EXAMPLE 10

12-Acetamido Camptothecin-20-acetate

A mixture of 12-amino Camptothecin (1.23g, 3.4 mmol) and 20 mL acetyl chloride is stirred under argon for 5 hours. Acetyl chloride is then removed in vacuo . Residue is dissolved in chloroform, washed with brine, dried over anhydrous sodium sulfate. The solvent was removed to give 1.648g crude product. 12-Acetamido Camptothecin-20-acetate is further purified from crude product by recrystallization in methanol, l.Olg brown solid, 67% yield.

12-acetamido-camptothecin-20-acetate: ¹R NMR (CDC1₃) δ 9.60

(IH, S), 8.88 (IH, d, J = 7.2 Hz), 8.39 (IH, s), 7.62 (2H, m) , 7.09 (IH, s), 5.63 (IH, d, J = 17.4 Hz), 5.38 (IH, d, J = 17.4 Hz) , 5.29 (2H, s) , 2.44 (3H, s) , 2.35 (IH, m) , 2.23 (3H, s) ,

2.17 (IH, m) , 0.99 (3H, t, J = 7.2 Hz) .

¹³C NMR (CDC1₃) δ 170.0, 168.8, 167.6, 157.4, 150.5, 146.0,

145.7, 138.9, 134.9, 132.0, 129.2, 128.2, 122.1, 121.0, 117.9, 95.8, 76.3, 67.3, 50.1, 32.1, 25.6, 21.0, 7.7.

EXAMPLE 11 9-Bromo-12-acetamido Camptothecin-20-acetate

Direct bromination of 12-amino Camptothecin with bromine in acetic acid has given 9, ll-dibromo-12-amino Camptothecin. The conversion of the amino group to acetamide group deactivates the electrophilic substitution reaction of the aromatic ring.

12-Acetamido Camptothecin (0.400g, 1 mmole) in 5 mL acetic acid is cooled down to 11 °C, and 1% bromine in acetic acid solution (5 mL, 1 equiv.) was added drop-wise within one hour. After the reaction, chloroform is added, the reaction mixture is washed with brine, saturated sodium bicarbonate solution, brine, and dried over anhydrous sodium sulfate. Organic solvent is removed to furnish 0.490g 9-Bromo-12- acetamido Camptothecin. The reaction is found to be a quantitative conversion. _«._

^XH NMR (CDCI₃) δ 9.52 (IH, S) , 8.75 (IH, s) , 8.73 (IH, d, J =

7.5 Hz) , 7.83 (IH, d, J = 8.4 Hz) , 7.03 (IH, s) , 5.59 (IH, d, J = 17.4 Hz) , 5.34 (IH, d, J = 17.4 Hz) , 5.28 (2H, s) , 2.38 (3H, s) , 2.30 (IH, m) , 2.22 (3H, s) , 2.13 (IH, m) , 0.94 (3H,

t, J = 8.1 Hz) .

EXAMPLE 12 9-Bromo Camptothecin

To 0.49g crude 9-Bromo-12-acetamido Camptothecin-20- acetate (3.0 mmol) in a 100-mL flask is added 30 mL 10% sulfuric acid in ethanol solution. The reaction mixture is refluxed for an hour. Brown colored solid started precipitated from the solution. At this time, 0.21g sodium nitrite is introduced. The reaction mixture is refluxed for an additional hour. When the reaction is cooled to room temperature, 20 mL water is added. Ethanol is removed in vacuo. The residue is repeatedly extracted with chloroform. Chloroform solution is washed with sodium bicarbonate solution, brine solution, and dried with sodium sulfate. The solvent is removed to give 0.40g crude product. The crude product is purified by flash column, hexane and acetyl acetate 1:5 as eluent, 0.21g 9-bromo Camptothecin is isolated, 48% yield. ^XH NMR (DMSO-d₆) δ 8.79 (IH, s) , 8.18 (IH, d, J = 8.4

Hz) , 7.92 (IH, d, J = 7.5 Hz) , 7.69 (IH, s) , 7.64 (IH, t, J =

7.8 Hz) , 5.72 (IH, d, J = 16.5 Hz) , 5.34 (2H, s) , 5.28 (IH, d, J = 16.8 Hz) , 3.78 (IH, broad s) , 1.85 (2H, m) , 1.02 (3H, t, J = 7.5 Hz) .

EXAMPLE 13 7- (2-trimethylsilylethyl ) homocamptothecin

200 mg of homocamptothecin is suspended in 10 mL of water and 4 mL of acetic acid. 400 mg of iron (II) sulfate heptahydrate is added and the mixture stirred for 10 minutes. 0.6 mL of 3-trimethylsilyl propanal is added, the mixture is cooled to 0 °C and 4 mL concentrated sulfuric acid is added dropwise. The ice bath is removed and 30% hydrogen peroxide is added, the resulting solution stirred for 4 hours, then quenched with ice. The aqueous phase was extracted with chloroform (3x20 mL) . The combined organic extract was washed with brine, dried over anhydrous sodium sulfate, filtered through silica gel, and concentrated using a rotary evaporator. The crude product was purified by column chromatography (silica gel, 2% methanol/chloroform) to furnish 30 mg of the title compound. ^τR NMR (CDCI₃, 300 Hz): δ 8.04 (d, 1 H, J = 8.1 Hz), 7.91 (d, 1 H, J = 8.4 Hz), 7.72 (t, 1 H, J = 7.2 Hz), 7.57 (t, 1 H, J = 7.8 Hz), 7.53 (s, 1 H ), 5.70 (d, 1 H, J = 15.3 Hz), 5.36 (d, 1 H, J = 15.6 Hz), 5.18 (m, 2 H) , 3.47 (d, 1 H, J = 13.5 Hz), 3.22 (d, 1 H, J = 13.8 Hz), 3.04 (dd, 2 H, J = 12.6, 5.1 Hz), 2.04 (m, 2 H) , 1.00 (t, 3 H, J = 7.5 Hz), 0.91 (dd, 2 H, J =

12.5, 5.7Hz), 0.20 (s, 9 H) ppm.

¹³C NMR (300 MHz, DMSO) 5172.5, 159.7, 156.3, 152.7, 149.2, 147.4, 145.7, 130.5, 128.1, 128.0, 126.8, 124.4, 123.0, 100.1,

73.6, 61.9, 50.2, 42.9, 36.9, 23.8, 17.6, 8.9, -1.18 ppm

MS: (M+l) 463.2

EXAMPLE 14

7- (N, N-trimethylsilylethylamino) -20-acetyl camptothecin

A solution of 1, 1' -bis (diphenylphosphino) ferrocene (6 mg) and tris (dibenzylideneacetone) palladium (0) (5 mg) in 2 mL of toluene is stirred at room temperature for 10 minutes. To this mixture is added 43 mg of 7- trifluoromethanesulfonyloxy-20-acetyl camptothecin, 0.5 mL of diisopropylethyl amine, and 19 μL of 2-trimethylsilylethyl amine. The reaction mixture is stirred at room temperature for 3 days, and added 5 mL chloroform and 5 mL water. The aqueous phase is then extracted with chloroform (3x5 mL) . The combined organic extract is washed with brine, dried over anhydrous sodium sulfate, filtered through silica gel, and concentrated by a rotary evaporator. The crude product is purified by radial PLC using 2% methanol/ethyl acetate as eluents to yield 8.8 mg of the title compound as a yellow solid.

¹R NMR (300 MHz, CHCI3) 58.07 (d, IH, J = 8.7 Hz), 7.75 - 7.70

(m, 2H) , 7.53 (dd, IH, J = 6.6, 8.0 Hz), 7.16 (s, IH) , 5.68 (d, 1 H, J = 17.1 Hz), 5.59 (s, 2H) , 5.41 (d, IH, J = 17.1 Hz), 5.12 - 5.05 (m, IH) , 3.22 (d, 2H, J = 5.1 Hz), 2.33 - 2.11 (m, 5H) , 0.96 (t, 3H, J = 7.5), 0.30 (s, 9H) ;

¹³C NMR (300 MHz, CDCI3) 5170.1, 168.0, 157.4, 153.6, 149.4,

148.6, 147.3, 146.1, 130.4, 130.3, 126.2, 119.5, 118.8, 107.3, 95.5, 76.1, 67.4, 50.9, 34.9, 32.0, 21.0, 7.8, -2.5 ppm.

EXAMPLE 15

7- (N, N-trimethylsilylethylamino) -20 (S) Camptothecin

To a solution of 8.8 mg of 7-trimethylsilylethylamino-20- acetyl camptothecin from Example 14 in 2 mL of methanol, is added 4 mg of potassium carbonate and 3 drops of water. The mixture is stirred at room temperature for 2 hours, neutralized with saturated ammonium chloride and dried over anhydrous sodium sulfate. The mixture is then filtered through silica gel and the crude product purified by radial PLC using 2% methanol/ethyl acetate as eluents to yield 2.0 mg of the title compound as a yellow solid.

3-H NMR (300 MHz, CDC1₃) 58.02 (d, IH, J = 8.4 Hz), 7.68-7.62 (m, 2H) , 7.54 (s, IH) , 7.45 (t, IH, J = 7.8 Hz), 5.69 (d, IH, J = 16.2 Hz), 5.54 (s, 2H) , 5.24 (d, IH, J = 16.2 Hz), 5.03 - 4.92 (m, 1 H) , 3.64 (s, IH) , 3.15 (d, 2H, J = 5.1 Hz), 1.88 - 1.78 (m, 2H), 0.97 (t, 3H, J = 7.2), 0.22 (s, 9H) ; MS (El, M/Z) : 449 (M⁺, 100)

EXAMPLE 16

7- (2-trimethylsilyl) ethyl camptothecin-N-oxide

500 milligrams of recrystallized 7- (2-trimethylsilyl) ethyl camptothecin was suspended in 20 mL glacial acetic acid and 35% hydrogen peroxide (2 mL) added. The reaction mixture was then stirred under a positive pressure of nitrogen at room temperature for 48 hours followed by thin layer chromatography for the complete consumption of the starting material. An aliquot of the reaction mixture (~ 0.1 mL) was concentrated at room temperature under high vacuum, ished with ether and dried and analyzed by high field NMR. The reaction mixture was cooled to 10 °C using an ice bath. The cold reaction mixture was then poured into 50 g of crushed ice and allowed to stand for at least 4 hours. An additional 250 mL of water was then added and the product filtered. The product was finally ished with ether (250 mL) and dried to furnish 486 mg of the title compound as a pale orange colored powder.

¹H NMR (CDC1₃); δ 0.21(9H, s), 0.82- 0.87 (2H, m) , 0.97 (3H, t, J= 9 Hz), 1.8- 1.85 (2H, m) , 2.94- 2.99 (2H, m) , 5.1 (2H, s), 5.18- 5.68 (2H, ABq, J_AB= 18 Hz; J_AC= 132 Hz), 7.67- 7.81 (2H, ) , 7.95 (IH, d, J= 8.1) 8.29 (IH, s), 8.77 (IH, d, J= 9 Hz)

EXAMPLE 17 10-Hydroxy-7- (2-trimethylsilyl) ethyl camptothecin

The foregoing N-oxide (50 mg) is taken along with peroxide free dioxane (50 mL) and purged with nitrogen for a period of 60 minutes in a photo-irradiation assembly equipped with High Pressure Mercury Lamp and double-jacketed chilled water circulation. To it is then added 0.5-1 mL of 5% sulfuric acid. The contents were then irradiated for a period of approximately 40 minutes. The crude product was obtained by concentrating the reaction mixture over a rotary evaporator at room temperature and by ishing the residue using cold water to remove the last traces of sulfuric acid. The crude product was then chromatographed over silica gel using 20% chloroform- methanol mixture to obtain 20 mg of the desired product along with 25 mg of 7- (2-trimethylsilyl) ethyl camptothecin as the deoxygenated N-oxide bye-product. The by-product, 7- (2- trimethylsilyl) ethyl camptothecin is usually recycled for the subsequent batch to make the title compound.

^XH NMR (CDC1₃); δ 0.16(9H, s), 0.99- 1.02 (2H, m) , 0.97 (3H, t, J= 9 Hz), 1.8- 1.85 (2H, m) , 3.04- 3.09 (2H, m) , 5.24 (2H, s), 5.18- 5.68 (2H, ABq, J_AB= 18 Hz; J_AC= 1³2 Hz), 7.54 (IH, d, J= 9) 8.07 (IH, s), 8.47 (IH, d, J= 9 Hz)

EXAMPLE 18 9-Nitro camptothecin/12-nitro camptothecin

Camptothecin (5.82g) from recrystallization was dissolved in 25 mL 98% concentrated sulfuric acid. The solution was stirred at room temperature overnight. Potassium carbonate (1.5 g) was added and the reddish reaction solution was stirred for 48 hours. An additional 1.5 g of K₂C0₃ is added and the solution was stirred for one more day. Cold water (100 mL) was added dropwise to the reaction solution in an ice bath. The resulting mixture was extracted with chloroform, 300 mL x 5. Chloroform solution was concentrated to c.a. 200 mL, heated to 60 °C for 30 minutes, and cooled to room temperature. The precipitate, 12-nitro camptothecin, was isolated, 3.28g, 50% yield. The mother liquor was concentrated, purified by column, and eluted with ethyl acetate. 1.72g of 9-nitro camptothecin was isolated (29% yield) .

9-Nitro camptothecin: ^λR NMR (DMSO-d₆) δ 9.08 (IH, s), 8.48

(IH, d, J = 8.7 Hz), 7.43 (IH, d, J = 7.8 Hz), 7.96 (IH, t, J = 8.1 Hz), 7.32 (IH, s), 6.48 (IH, s), 5.37 (2H, s), 5.27 (2H, s), 1.80 (2H, m) , 0.81 (3H, t, J = 7.2 Hz).

12-Nitro camptothecin: ^λR NMR (DMSO-d_s) δ 8.78 (IH, s), 8.31

(IH, d, J = 8.4 Hz) , 7.43 (IH, d, J = 8.7 Hz) , 7.78 (IH, t, J = 8.1 Hz), 7.18 (IH, s) , 5.35 (2H, s) , 5.22 (2H, s) , 1.78 (2H, m) , 0.80 (3H, t, J = 7.5 Hz) .

EXAMPLE 19

9-Bromo camptothecin

9-Nitro camptothecin (0.95g, 2.42 mmol) was dissolved in a mixed solvent of ethanol (75 mL) and dioxane (75 mL) . Platinum oxide (89 mg) was added as a catalyst. The reaction mixture was vigorously stirred and bubbled with hydrogen. The hydrogenation was monitored by NMR, and the reaction was completed in two hours. The mixed solvent was removed in vacuo . Without further purification, the crude product of 9- amino camptothecin was used in the following reaction. The crude 9-amino camptothecin was dissolved in 16% hydrobromic acid (60 mL) in an ice bath. Sodium nitrite (240 mg, 3.48 mmol) in 10 mL water was added dropwise into the above clear brown solution over 15 minutes. The reaction mixture was stirred at 0 °C for 30 minutes. The diazonium salt is soluble in 16% hydrobromic acid solution. In another flask, copper (I) bromide (1.82g, 12.7 mmol) was dissolved in 50 mL 24% hydrobromic acid at 60 °C under argon. The diazonium solution was added slowly by a syringe over 15 minutes. The reaction solution was stirred at 60 °C for two hours, cooled to ambient temperature and poured into crashed ice. The diluted aqueous mixture was extracted with chloroform three times . All chloroform layers were combined and ished with water twice, dried with sodium sulfate. The solvent is removed in vacuo to give 0.85g crude product. The crude product was purified by flash column, 2% methanol in chloroform solution as eluent. 0.63 g of 9-bromo camptothecin is isolated, 61% overall yield.

^λ NMR (DMSO-d₆) δ 8.79 (IH, s), 8.18 (IH, d, J = 8.4 Hz),

7.92 (IH, d, J = 7.5 Hz), 7.69 (IH, s), 7.64 (IH, t, J = 7.8 Hz), 5.72 (IH, d, J = 16.5 Hz), 5.34 (2H, s), 5.28 (IH, d, J

= 16.8 Hz), 3.78 (IH, broad s) , 1.85 (2H, m) , 1.02 (3H, t, J = 7.5 Hz) .

EXAMPLE 20

12-Acetamido-camptothecin/ 12-acetamido-camptothecin-20-acetate

A mixture of 12-amino-camptothecin (1.23 g, 3.4 mmol) and 20 mL acetyl chloride is stirred under argon for 5 hours.

Acetyl chloride is removed in vacuo . Residue is dissolved in chloroform, washed with brine, dried with sodium sulfate. The solvent is removed to give 1.648 g crude product. 12- Acetamido-camptothecin is purified from crude product by recrystallization in methanol, l.Olg brown solid, 67% yield.

When acetic anhydride and pyridine are used to make amide, 12- acetamido-camptothecin-20-acetate is the major product, along with 5-acetyl-12-acetamido-camptothecin-20-acetate .

12-acetamido-camptothecin-20-acetate: R NMR (CDC1₃) δ 9.60

(IH, S), 8.88 (IH, d, J = 7.2 Hz), 8.39 (IH, s), 7.62 (2H, m) , 7.09 (IH, s), 5.63 (IH, d, J = 17.4 Hz), 5.38 (IH, d, J = 17.4 Hz), 5.29 (2H, s), 2.44 (3H, s), 2.35 (IH, m) , 2.23 (3H, s), 2.17 (IH, m) , 0.99 (3H, t, J = 7.2 Hz). ¹³C NMR (CDCI₃) δ 170.0, 168.8, 167.6, 157.4, 150.5, 146.0,

145.7, 138.9, 134.9, 132.0, 129.2, 128.2, 122.1, 121.0, 117.9, 95.8, 76.3, 67.3, 50.1, 32.1, 25.6, 21.0, 7.7.

Claims

What is Claimed I s

1. A compound of the formula:

wherein:

R and Ri are each individually hydrogen, lower alkyl, lower alkenyl, lower alkynyl, alkoxy, halo, aryl, arylalkyl, arylalkenyl, arylalkynyl, -X_- (C₀-C₆ alkylene, Cι-C₆ alkenylene or C₂-C₆ alkynylene) -SiRι₂Rι₃Ri4, -Xι~ (C₀-C₆ alkylene, Cι-C₆ alkenylene, C₂-C₆ alkynylene, phenylene or benzylene) -NR₉Rι₀, or OR₆ ;

R_2f R₃ and R₅ are each individually hydrogen, lower alkyl, lower alkenyl, lower alkynyl, alkoxy, halo, aryl, arylalkyl, arylalkenyl, arylalkynyl, amino, nitro, protected amino, -X2-(C₀-C₆ alkylene, Cι-C₆ alkenylene or C2~C₆ alkynylene) -SiRι₂Ri3Ri4, -X2- (C₀-C6 alkylene, Cι-C₆ alkenylene, C₂-C6 alkynylene, phenylene or benzylene) -NRg_aRι_0a, or OR₈, wherein at least one of R₂, R₃ and R₄ is other than hydrogen; and wherein when Ri is hydrogen, lower alkyl, lower alkenyl, lower alkynyl, alkoxy, halo, aryl, arylalkyl, arylalkenyl or arylalkynyl, then one or more of R₂, R₃ and R₄ is -X₂- (C₀-C6 alkylene, Cι-C₆ alkenylene or C₂-C₆ alkynylene) -SiRι₂Ri3Rι ; R₆ is hydrogen, lower alkyl, or an oxygen-protecting group;

R₇ is hydrogen, lower alkyl, aryl, -SiRι₂Rι₃Ri4, or is absent when Rn is hydrogen;

R₈ is hydrogen, lower alkyl or - (Co-Cβ alkylene, Co-C₆ alkenylene or Co-Cδ alkynylene) -SiRι₂Ri3Ri ;

R₉, Rio, R_9a and Rι_0a are each individually hydrogen, lower alkyl or a nitrogen-protecting group;

Rn is hydrogen, carbonyl, sulfonyl, thiocarbonyl, sulfoxo, C1-C16 alkylene-, -O- or -S-; R12, R13, and Rχ are each individually hydrogen or C1-C10 alkyl;

R₁₅ is hydrogen, lower alkyl or a nitrogen-protecting group;

X is -CH₂- or absent; Xi and X₂ are each individually sulfur, NR₁₅ or absent; or a pharmaceutically acceptable salt thereof.

2. The compound of Claim 1 wherein X is methylene, and Ri is -Xi-lower alkylene-SiRi2Ri3Rι₄.

3. The compound of Claim 1 wherein Ri is -ethylene- trimethylsilyl, and X is methylene.

4. The compound of Claim 1 wherein Ri is -Xi- (Co-C_δ alkylene) - SiRi2Ri₃Ri₄, and one or more of R₂, R3 and R₄ is halo.

5. The compound of Claim 1 wherein Xi is -NR15.

6. A pharmaceutical formulation comprising a compound of Claim 1, and one or more pharmaceutically acceptable solvents, excipients, diluents or fillers.

7. A method of treating a patient suffering from a neoplastic disease comprising administering an effective amount of a compound of Claim 1 to said patient.