HRP921223A2 - Process for preparing 4-demethoxydaunomycinone - Google Patents

Description

The presented invention relates to an improved process for the preparation of 4-demethoxydaunomycin of formula I

[image]

In British patent application no. 8803301 of the said applicant, a new process for the preparation of 4-demethoxydaunomycinone was described. The process in terms of that invention differed from the state of the art in that it started from natural daunomycin, which was faster, more efficient and gave the final product in a much higher yield than earlier processes. In addition, it did not require a degree of optical separation.

The process for the preparation of 4-demethoxydaunomycinone in accordance with the earlier invention used as starting material (+) daunomycinone, which can be obtained according to the procedure described in US-A-4012284. (+) daunomycinone was demethylated by treatment with AlCl3 into 4-demethoxydaunomycinone and by reaction with ethylene glycol they converted it into its 13-dioxolanyl derivative (3). The obtained compound (3), 4-demethyl-13-dioxolanylnyl-daunomycinone was sulfonated in the C4-OH position without special protection of the remaining OH groups. The sulfonating agent was sulfonyl chloride of formula (II)

R-SO2Cl (II)

in which it is advantageous when R is a 4-fluorophenyl or 4-tolyl group.

The sulfonylated compound is then treated, preferably with 4-methoxybenzylamine or 3,4-dimethoxybenzylamine. The resulting 4-amino derivative was diazotized, typically in an acidic medium with sodium nitrate. The resulting diazonium salt was finally reduced under mild conditions, eg with 50% hypophosphorous acid, to obtain 4-demethoxydaunomycinone.

In accordance with the presented invention, a procedure for the preparation of 4-demethoxydaunomycinone of formula (I) has been determined, which includes

(i) reaction of 4-demethyl-13-dioxolanildaunomycinone of formula (3)

[image]

in the presence of N,N-diisopropylethylamine and a catalytic amount of 4-dimethylamino-pyridine with a sulfonyl compound of formula II

R-SO2X (II),

in which X represents a halogen atom, a group OSO2R, an imidazolyl group, a group NH(C6H5)(RSO2) or some other group capable of reacting with phenol to obtain a sulfonate, and R represents an alkyl group with 1 to 10 carbon atoms, which is in a given example substituted with one or more halogen atoms, or an aryl group which in a given example is substituted with halogen, alkyl, alkoxy or nitro;

(ii) reaction of the resulting sulfonated 4-demethyl-13-dioxolanyl-daunomycinone of formula (4)

[image]

in which R is defined as before, under reductive conditions with a catalytic amount of a compound of the formula

MLnL'm (III),

where M represents a metal atom, L and L', which are the same or different, each represent an anion or a neutral molecule, and n and m vary from 0 to 4, and

(iii) removal of the 13-oxo protecting group from the resulting dioxolanildaunomycinone (5)

[image]

The improved procedure is shown in the following diagram:

[image]

The intermediate 13-dioxolanyl derivative (3) can be prepared from 4-demethyldaunomycinone, also called carminomycinone. This is easily achieved by treatment with ethylene glycol, for example in the presence of p-toluenesulfonic acid at reflux temperature. 4-Demethyldaunomycinone can be prepared from (+) daunomycinone. Demethylation can be carried out by treatment with AlCl3, usually in an inert organic solvent such as nitrobenzene at reflux temperature. This process is described in US-A-4188377.

In step (i), we react 4-demethyl-dioxolanyl-daunomycinone (3) with the sulfonating agent of formula (II)

R-SO2-X,

in which X can be a halogen atom, an OSO2R group, an imidazolyl group, a NH(C6H5)(RSO2) group or some other group that is capable of reacting with phenol after the formation of sulfonates, and R represents an alkyl group with 1 to 10 carbon atoms that is in in the given example substituted with one or more halogen atoms, or an aryl group which in the given example is substituted with a halogen, alkyl, alkoxy or nitro group, obtaining the 4-sulfonylated 13-dioxolanyl compound (4). Favorable groups that can represent R are trifluoromethanesulfonyl, 4-fluorophenyl and 4-tolyl. The reaction can be carried out with 4-demethyl-13-dioxolanyl-daunomycin dissolved in pyridine at room temperature.

Sulfurated 4-demethyl-13-dioxolanyl-daunomycinone (4) is converted into the final product (I) in two steps that can be easily carried out without isolating intermediates and with improved yield and purity. In step (ii), we treat the sulfonated compound (4) under suitable reductive conditions with the compound (II) (called catalyst in this text).

MLnL'm (III),

where M represents a metal atom, L and L', which are the same or different, can be an anion, such as Cl- or CH3COO-, or a neutral molecule such as a solvent molecule, mono- or di-phosphine, phosphite or diamine, and n and m easily vary from 0 to 4. Usually m + n is at least 1, eg 1, 2, 3 or 4. It is advantageous when the metal represented by M is palladium or nickel. Favorable groups representing L and/or L' are diphosphines which form chelates, such as 1,3-diphenylphosphinopropane or 1,1'-bis(diphenylphosphino)-ferrocene. The sulfonated compound (4) is therefore chosen with a catalytic amount of metal, preferably a metal complex such as palladium or nickel, and with the above-mentioned ligand that forms chelates, such as 1-3diphenylphosphino-propane or 1,1'-bis(diphenylphosphino)ferrocene. The molecular ratio of metal atoms and ligands forming chelates is advantageously 1:1 to 1:4.

As an example of how easily we can carry out step (ii), we dissolve the sulfonated compound (4) in a suitable polar solvent and add it under an inert atmosphere to a solution of catalyst either previously prepared or prepared "in situ" from suitable precursors in the presence of a reducing system capable of act as a formal hydrogen donor. A suitable reducing system for the conditions in the presented invention is trialkylammonium formate prepared "in situ" by the addition of formic acid and trialkylamine. The reaction temperature is usually from 0 to 150ºC, it is advantageous when it is from 30 to 100ºC. We can easily carry out the reaction during 4 to 24 hours, it is advantageous during 6 to 18 hours. Let's use the catalyst in a molecular ratio of 1:1 to 1:10000, preferably between 1:20 to 1:1000 in relation to the sulfonated compound (4).

The reduction stage /(4) to (5)/ was insufficiently used for simple molecules such as naphthalene and anthracene derivatives (Tetrahydron Lett 27 (1986) 5541; ibidem 28 (1987) 1381), although they did not use it for the hydrolysis of sulfonates of various substituted anthraquinone molecules . The reaction is new in anthracycline chemistry, probably due to the presence of other functional groups. Problems arising from the presence of these groups, especially aromatization of ring A, formation of 7-deoxy derivatives, hydrolysis of 4-sulfonated derivatives and/or modification of the quinone part, can be prevented by the conditions according to the presented invention.

In step (iii), we remove the 13-oxo protecting group from the resulting 4-demethoxy-13-dioxolanyl-daunomycinone (5). I achieve this using trifluoroacetic acid without isolating compound (5). For example 4-demethoxy-13-dioxolanyl-daunomycinone (5) can be easily treated with trifluoroacetic acid at room temperature for one hour. Thus the desired 4-demethoxy-daunomycinone (1) is obtained. It can be easily purified by chromatography on silica gel using a mixture of chloroform/acetone 9/1 vol./vol. as elution agents.

4-demethoxy-daunomycinone is the aglucon part of the useful antitumor agent 4-demethoxy-daunorubicin. Accordingly, the presented invention provides a process for the preparation of 4-demethoxy-daunorubicin of formula (IV)

[image]

in which R1 represents

[image]

or its pharmaceutically acceptable salts, and the process comprises the reaction of 4-demethoxy-daunomycinone of formula (I), which we prepared by the process according to the invention, with a suitable sugar derivative, and then, if desired, the conversion of the thus obtained 4-demethoxy-daunorubicin into its pharmaceutically acceptable salt.

It is advantageous for the sugar derivative to have the formula (V)

[image]

in which Hal represents a halogen atom, R2 represents a protected hydroxy group, and R3 represents a protected amino group, and the protecting groups are removed after the reaction with 4-demethoski-daunorubicin. It is advantageous when Hal is a chlorine atom. The hydroxy group can be easily protected using a trifluoroacetic group. We can also protect the amino group very easily using trifluoroacetic acid.

The resulting 4-demetho-daunorubicin or its pharmaceutically acceptable salt can be easily formulated, for example for use as an antibiotic or antitumor agent, as a pharmaceutical preparation containing a pharmaceutically acceptable base or solvent.

The following example explains the present invention in more detail.

Example 1

4-demethyl-4-trifluoromethanesulfonyl-13-dioxolanyl-daunomycinone (4)

In a solution of 11 g (25.7 mmol) of compound (3), 22 ml (128.5 mmol) of diisopropylethylamine and 3.8 g (25.7 mmol) of 4-dimethylaminopyridine in pyridine (1.1 l), cooled to 0ºC, add 12.7 ml (75.5 mmol) of trifluoromethanesulfonyl anhydride and stir the reaction mixture for one hour at room temperature. The reaction mixture is then cooled to 0ºC and 5 l of methylene chloride and 3 l of 10% hydrochloric acid are added. After separation, the organic phase is washed with water, dried over sodium sulfate and evaporated under reduced pressure to obtain 13.75 g of a solid, which is then refluxed in ethanol (350 ml) for 15 minutes and then filtered to obtain 8.25 g of compound (4).

(HPLC: 91%; HPLC analysis:

Column: MERCK RP 18.7 µm (250 x 4.2 mm)

Mobile phase:

A- 0.01M sodium heptanesulfonate/0.02 M

phosphoric acid 6

acetonitrile 4

B- methanol 7

acetonitrile 3

Gradient: from 20% to 70% B in 25 min.,

Flow rate: 1.5 ml/min.,

Detector: UV at 254 nm.

1H-NMR 300 MHz (in COCl3): = 1.47 (3H, s), 1.98 (1H, dd, J=4.7, 14.6 Hz), 2.47 (1H, d, J= 14.5 Hz), 2.79 (1H, d, J=19.0 Hz), 3.21 (2H, m), 3.82 (1H, bs); 4.09 (4H, s), 5.27 (1H, bs), 7.63 (1H, d, J=8.1 Hz), 7.88 (1H, t, J=7.9 Hz), 8.48 (1H, d, J=7.7 Hz), 13.26 (1H, s), 13.48 (1H, s).

M.S.: m/z = 560 M+, base peak).

TLC on Kieselgel plates F 254 (Merck) after using chloroform/acetone (8:2 vol.) Rf=0.56.

Example 2

4-demethoxydaunomycin (II)

10 ml of triethylamine, 2.7 ml of formic acid, 55 mg of 1,1'-bis(diphenylphosphino)ferrocene (0.089 mmol) were added to a solution of 10 g of compound (4) (17.8 mmol) in 250 ml of dimethylformamide in an inert solution. ) and 20 mg of palladium acetate (0.089 mmol). The reaction mixture was stirred for 7 hours at 40ºC and then cooled to 0ºC, acidified with 10% hydrochloric acid and extracted with methylene chloride. The organic phase was evaporated to dryness and the residue was treated with 50 ml of trifluoroacetic acid for one hour at room temperature. The reaction mixture was then diluted with 500 ml of water and extracted with methylene chloride. The organic layer was washed with saturated sodium bicarbonate solution and water until neutral, dried over sodium sulfate and evaporated to dryness. The residue was chromatographed on silica gel (chloroform/acetone 9:1 by volume as eluent), whereby we obtained 4.7 g (71.6%) of 4-demethoxydaunomycin (I) (HPLC 98%).

1H-nmr 300 MHz (in COCl3): = 2.19 (1H, dd, J=4.8, 14.5 Hz), 2.37 (1H, ddd, J=2.0 14.5 Hz), 2.43 (3H, s) 2.95 (1H, d, J=18.6), 3.20 (1H, dd, J=2.0, 18.6 Hz), 3.83 (1H, d , J=4.8 Hz), 4.55 (1H, s), 5.32 (1H, ddd, J=2.0, 4.8, 4.8 Hz), 7.84-7.86 ( 2H, m), 8.33-8.36 (1H, m), 13.30 (1H, s) 13.60 (1H, s).

U.V. spectrum (in EtOH): = 208, 252, 257, 285, 480, 500, 514 nm., λ max. = 252 nm.

I.R. spectrum (KBr tablet) = 3450, 1715, 1625, 1585 cm-1

[α]D20 (C = 0.1 in dioxane) = + 159º

M.S.: m/z = 368 (M+, base peak)

TLC on Kieselgel plate F 254 (Merck) after using chloroform/acetone (8:2 vol.) Rf = 0.70

Example 3

The reaction was carried out as described in Example 2, but we used dioxane as solvent (250 ml) and 1,3-diphenylphosphinopropane (37 mg, 0.089 mmol) as ligand for palladium. After 16 hours at 60ºC, the reaction mixture was selected in the manner described in example 2, whereby we obtained 3.8 g (58%) of (I) (HPLC 97.8%).

Example 4

The reaction was carried out in the manner described in example 2, but we used 200 mg of palladium acetate (0.89 mmol) in 560 mg of 1,2bis/N-(1-phenylethyl), N-(diphenylphosphino)amino/ethane. After 14 hours at 60ºC, the reaction mixture was processed as described in example 2, whereby we obtained 4.1 g (62.4%) of compound (I), (HPLC 98.3%)

Claims (4)

1. Preparation process of 4-demethoxy-davnomycin formula (I) [image] indicated by that (i) we react 4-demethyl-13-dioxolanyl-davnomycinone of formula (3) [image] in the presence of N,N-diisopropylethylamine and a catalytic amount of 4-dimethylamino-pyridine with a sulfonyl compound of formula II R-SO2X (II) in which X represents a halogen atom, a group OSO2R, an imidazolyl group, a group NH(C6H5)(RSO2) or some other group capable of reacting with phenol to obtain a sulfonate, and R represents an alkyl group with 1 to 10 carbon atoms, which is in a given example substituted with one or more halogen atoms, or an aryl group which in a given example is substituted with halogen, alkyl, alkoxy or nitro; (ii) we react the resulting sulfonated 4-demethyl-13-dioxolanyl-davnomycinone of formula (4) [image] in which R is the same as previously defined, under reductive conditions with a catalytic amount of a compound of the formula MLnL'm(III) in which M represents a metal atom, L and L', which can be the same or different, each represent an anion or a neutral molecule, and n and m can vary from 0 to 4, and (iii) remove the 13-oxo protecting group from the resulting 4-demethoxy-13-dioxolanyl-davnomycinone (5) [image] 2. Preparation procedure of 4-demethoxy-davnorubicin formula (IV) [image] in which R1 represents [image] or its pharmaceutically acceptable salts, indicated by the fact that we react 4-demethoxy-davnomycinone of formula (I), which was prepared by the process in accordance with claim 1, with a suitable sugar derivative of choice, and optionally convert the thus obtained 4-demethoxy-davnorubicin into a pharmaceutically acceptable salt thereof. 3. The method according to claim 2, characterized in that the sugar derivative has the formula (V) [image] in which Hal represents a halogen atom, R2 represents a protected hydroxy group and R3 represents a protected amino group, and after the reaction with 4-demethoxy-davnomycinone we remove the protecting groups. 4. Pharmaceutical preparation, characterized by the fact that it includes a pharmaceutically acceptable base or diluent and as an active ingredient 4-demethoxy-davnorubicin or its pharmaceutically acceptable salt prepared according to claim 2 or 3.