GB1582627A

GB1582627A - Derivatives of sandwicine and isosandwicine and pharmaceutical compositions comprising sandwicine isosandwicine and derivatives thereof

Info

Publication number: GB1582627A
Application number: GB1769/76A
Authority: GB
Original assignee: Inverni Della Beffa SpA
Current assignee: Inverni Della Beffa SpA
Priority date: 1976-01-16
Filing date: 1976-01-16
Publication date: 1981-01-14
Also published as: DE2701417A1; FR2338276B1; GR59327B; PT66064B; JPS5289686A; ES455085A1; PT66064A; FR2338276A1; BE850342A

Description

(54) DERIVATIVES OF SANDWICINE AND ISOSANDWICINE AND PHARMACEUTICAL COMPOSITIONS COMPRISING SANDWICINE, ISOSANDWICINE AND DERIVATIVES THEREOF (71) We, INVERNI DELLA BEFFA S.p.A., an Italian Company of Via Ripamonti, 99 Milan, Italy, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to the alkaloids sandwicine and isosandwincine, to novel derivatives thereof, to methods of preparing these derivatives and to pharmaceutical compositions containing the alkaloids and their derivatives.

Sandwicine and isosandwicine are indolic alkaloids which may be isolated from roots of plants of the genus Rauwolfia and especially from roots of plants of the species Rauwolfia vomitoria. Sandwicine and isosandwicine both have the empirical formula C2()H26N2O2 and have been assigned the following structural formula

wherein the case of sandwicine R' = a-OH and R2 = methyl and in the case of isosandwicine R' = p-OH and R2 = a-ethyl.

We have now found that sandwicine and isosandwicine possess valuable pharmacological properties and in particular pharmacologically useful effects on the cardiovascular system.

Furthermore, it has also been found that certain novel derivatives of sandwicine and isosandwicine similarly are pharmacologically active and in addition may display the advantages over the parent alkaloids of higher activity, lower toxicity or both.

Thus according to one aspect of the invention there are provided pharmaceutical compositions comprising a pharmaceutically acceptable excipient and as active ingredient sandwicine, isosandwicine, a compound having the following structural formula

in. which: u-iR3 R3 is, an unsubstituted alkyl group or an alkyl group substituted by one or more hydroxyl, alkoxy, amino, alkylamino or nitrogen-containing heterocyclic groups, R4 is hydroxy X- is a pharmaceutically acceptable anion, and- either R5 is a -OH and R6 is ss -ethyl, or R5 is ss -OH and R6 is a -ethyl or a pharmaceutically acceptable acid addition salt of sandwicine, of isosandwicine or of said compound of the formula II with the proviso that where the sole active ingredient is sandwicine, isosandwicine or a pharmaceutically acceptable acid addition salt of sandwicine or of isosandwicine and the sole diluent or carrier is water; the composition is sterile and pyrogen-free.

Preferably, the pharmaceutical compositions contain compounds of formula II in which R3 is an unsubstituted alkyl group.

The substituted and unsubstituted alkyll groups represented by R3, preferably contain not more than 15 carbon atoms and most preferably not more than 8 carbon atoms. A particularly preferred glass are substituted or unsubstituted lower alkyl groups containing 1 to 6 carbon atoms.

Specific examples of groups R3 consist of or are derived from C13 alkyl groups and include methyl propyl, substituted ethyl groups of the formula -CH2.CH2.NR 2 (wherein the moieties R , which may be the same or different, represent hydrogen atoms or alkyl groups, or together with the nitrogen atom to which they are attached form a heterocyclic ring); substituted propyl groups of the formuls -CH2.CHOH.CH2OR8 where R8 represents a hydrogen atom or, lower alkyl group; and substituted propyl groups of the formula -CH,.CHOH.CHNR 2 where each R7 is as defined above.

R7 and R8 preferably contain not more than 15 and most preferably not more than 8 carbon atoms. A particularly preferred class are unsubstituted lower alkyl groups containing 1 to 6 carbon atoms.

Specific examples of compounds of formula II include N-methyl, N-propyl, N-[(2 hydroxy-3-diethylamino)-propyl)], N-[2-(piperid- 1-yl)ethyl] and N-(2-hydroxy-3-ethoxy propyl derivatives of sandwicine and of isosandwicine.

Examples of pharmacologically acceptable anions represented by X- are inorganic anions such as, for example, halide, sulphate, and nitrate, and organic anions such as, for example acetate, tartrate, citrate and sulphonated camphor.

The compounds of formula II are novel and constitute a further aspect of the present invention.

Derivatives of sandwicine and isosandwicine of formula II may be produced by subjecting sandwicine or isosandwicine to N-alkylation by reaction with an appropriate alkylating agent, preferably in the presence of an organic solvent. Desirably a solvent is chosen in which both the alkylating agent and alkaloid or alkaloid derivative are soluble, but in which the desired compound of formula II is insoluble. The compound of formula II will then be precipitated in the course of the reaction, thus facilitating its recovery.

Thus, for example. compounds of formula II in which R3 is an unsubstituted alkyl group may be prepared in the manner described above using as alkylating agent an alkyl halide.

Examples of solvents in which this reaction may be effected include protic solvents in which this reaction may be effected include protic solvents for example ethanol, polar aprotic solvents such as, for exaple, dimethyl sulphoxide, dimethyl formamide and acetonitrile and weakly polar solvents such as, e.g. diethyl ether.

Similarly, the derivatives'of formula II in which R3 is an aminoalkyl group, e.g. of the formula -CH,.CHzNR72 (as defined above) may be produced using as alkylating agent an appropriate N-substituted or unsubstituted-aminoalkyl halide, for example an N dialkylaminoalkyl halide.

Derivatives of formula II in which R3 represents a group of the formula -CH1.CHOH.CH2NR72 (as defined above) may be produced in the manner described above using as alkylating agent an appropriately substituted epoxypropane, preferably in the presence as solvent of a cyclic ether such as, for example, dioxan or tetrahydrofuran.

Sandwicine, isosandwicine and derivatives thereof in free base form may be converted to pharmacologically acceptable salts by treatment with an acid yielding pharmacologically acceptable anions, for example those referred to above.

Sandwicine and isosandwicine may be obtained in a state of purity suitable to enable them to be formulated into pharmaceutical compositions by extracting tissue of Rawsolfia vomitoria, especially the roots (particularly the root bark) with an organic solvent, for example C13 lower alcohol or halogenated hydrocarbon to obtain a solution containing alkaloids; isolating sandwicine and/or isosandwicine from the extracted solution.

The isolation of sandwicine and/or isosandwicine may be effected by contacting the extract with a base, for example ammonium hydroxide, extracting the basified extract with a chlorinated hydrocarbon solvent and fractionating the chlorinated hydrocarbon extract so as to recover sandwicine and/or isosandwicine.

The fractionation may take advantage of the different solubilities of sandwicine and isosandwicine compared to other components of the extract. Thus the chlorinated hydrocarbon extract may be evaporated to dryness and the residue so obtained subjected to one or more fractional crystallisations from, for example methanol and/or chloroform.

Sandwicine and isosandwicine may be separated from one another by fractional crystallisation by virtue of the relatively higher solubility of isosandwicine in chlorinated hydrocarbons such as chloroform, and the separated alkaloids may be purified by chromatography and/or recrystallisation either of the free alkaloids or of their derivatives.

Thus, sandwicine may advantageously be purified by treating crude sandwicine with acylating agent, for example acetic anhydride, to form a 17,21-diacyl derivative, subjecting the 17,21-diacyl derivative to chromatographic fractionation, for example using silica gel as solid absorbent and a 4:1 acetone-hexane mixture as eluent and saponifying the chromatographed 17,21-diacyl derivative.

Isosandwicine may conveniently be purified by dissolving the crude alkaloid in an organic solvent in which its acid addition salt with a mineral acid is insoluble, converting the alkaloid to its acid addition salt by treatment with the acid and separating precipitated acid addition salt so formed.

Sandwicine, isosandwicine and the pharmacologically acceptable derivatives of formulae II possess valuable pharmacological activity, these substances particularly having pharmacologically useful effects on the cardiovascular system. In particular, they have antiarrhythmic effects of particularly long duration. Thus the antiarrhythmic activity of sandwicine and isosandwicine has been found to be of longer duration than-that of ajmaline. Furthermore, derivatives of sandwicine and isosandwicine have been prepared which possess certan advantages over the free alkaloids, in particular the advantages of enhanced activity, lower toxicity or both.

Thus as indicated above, the present invention includes pharmaceutical compositions for the treatment of cardiac arrhythmia comprising as active ingredient an alkaloid selected from sandwicine, isosandwicine and the pharmacologically acceptable derivatives of the ,above defined formulae II and a pharmaceutically acceptable excipient.

The particular galenic form of the compositions of the invention depends on the intended route of administration and such forms may be amorphous or in the form of shaped dosage units. Examples include sterile liquids suitable for parenteral administration and forms suitable for oral administration (e.g. tablets, capsules, comfits, solutions or suspensions).

In formulating compositions according to the invention, a wide range of excipients may be used, the nature of which will depend, of course, on the intended mode of application of the composition. Examples include preservatives and buffering, thickening, suspending, stabilizing, wetting, emulsifying, colouring and flavouring agents. Specific examples of suitable excipients include carboxy vinyl polymers, propylene glycol, ethyl alcohol, water, cetyl alcohol, saturated vegetable triglycerides, fatty acid esters or propylene glycol, triethanolamine, glycerol, starch, lactose, sucrose, cellulose sorbitol, bentonite, cellulose, methylcellulose, carboxymethyl cellulose, lauryl-sulphate, dicalcium phosphate, powdered silica, titanium dioxide, lecithin, magnesium carbonate and magnesium stearate.

The production of sandwicine, isosandwicine and certan derivatives will be described in more detail in the following Examples.

EXAMPLE 1 Isolation of sandwicine and isosandwicine 10 kg. of root bark of Rauwolfia comitoria were extracted 4 times with 30 litres of methanol. The combined methanolic extracts were evaporated in vacuo to a volume of 5 litres, made alkaline with ammonium hydroxide to pH 9 and extracted twice with 10 litre aliquots of chloroform. The chloroform extracts were combined and evaporated in vacuo.

The residue was dissolved in 3 litres of methanol and left at OOC. for 15 hours. After filtration of the precipitate, the mother liquors were evaporated to dryness and the residue taken up in chloroform. The chloroform-insoluble solid was separated by filtration (500 grams fraction A) and the mother liquors evaporated to dryness in vacuo (440 grams, fraction B).

Fraction A was dissolved in 3000 ml. of pyridine and treated for 24 hours with 1000 ml. of acetic anhydride. The acetylated material was then chromatographed on a silica gel column using a 4 : 1 acetone-hexane mixture as eluent. 80 grams of 17, 21-di-O-acetyl sandwicine were obtained from which, after saponification with 0.1% methanolic KOH for 2 hours at room temperature and subsequent dilution with water, there were obtained 65 grams of amorphous sandwicine, [a]D + 174 (MeOH).

Fraction B was dissolved in 1500 ml. of acetone and treated with 400 ml. of concentrated hydrochloric acid. After filtration there were obtained 45 grams of isosandwicine hydrochloride by crystallisation from methanol. M.p. 245 , [a]D + 133 (MeOH).

EXAMPLE 2 Isosandwicine methiodide A solution of 0.9 grams of methyl iodide in 10 ml. of diethyl ether was added to a solution of 0.7 grams of isosandwicine in 60 ml. of the same solvent. After 24 hours, the precipitated solid (0.8 grams) was filtered, m.p. 275 (Found: C, 53.78; H, 6.17; N, 5.91; I, 26.93.

C2,H29N2021 requires: C, 53.85; H, 6.20; N, 5.98; I, 27.14).

EXAMPLE 3 N-propyl sandwicine bromide 2 grams of sandwicine were dissolved in 100 ml. of acetonitrile and treated, with agitation, for 12 hours at room temperature with 3 ml. of propyl bromide. The product precipitated from the reaction medium as it formed. Yield 1.7 grams, M.p. 240 (Found. C, 61.51; H, 7.29; N, 6.19; Br, 17.73. C23H33N2O2Br requires: C, 61.47; H, 7.35; N, 6.24; Br, 17.82).

EXAMPLE 4 N-[3-diethylamino-2-hydroxy-propyl] isosandwicine chloride dihydrochloride 3 grams of isosandwicine were refluxed for 6 hours in 35 ml. of dioxan with 0.7 grams of l-(diethylamino)-2,3-expoxypropane. The reaction mixture was concentrated to small volume ,' poured into ethyl ether saturated with hydrochloric acid, and the precipitate which formed crystallised from anhydrous acetone. Yield 3.2 g., m.p. 290 C (Found: C, 57.31; H, 7.84; N, 7.36; Cl, 18.71. C27H44N3O3Cl3 requires: C, 57.40; H, 7.79; N, 7.44; Cl, 18.87).

EXAMPLE 5 N-[2(-piperid-1-yl)-ethyl]-sandwicine chloride dihydrochloride 5 grams of sandwicine were dissolved in 120 ml. of anhydrous dioxan and refluxed for 48 hours with 4 grams of 2-(piperid-l-yl) ethyl chloride. The reaction mixture was diluted with ether saturated with hydrochloric acid, the precipitate filtered and crystallised from anhydrous methyl ethyl ketone. Yield 4.2 grams (Found: C, 52.37; H, 7.73; N, 7.58; Cl, 19.31. C27H42N3O2Cl3 requires: C, 52.29; H, 7.69; N, 7.69; Cl, 19.49).

EXAMPLE 6 N-(3-ethoxy-2-hydroxy-propyl)-isosandwicine chloride 5 grams of isosandwicine were dissolved in 85 ml. of tetrahydrofuran and refluxed for 36 hours with 3.8 grams of 3-ethoxy-l, 2-epoxypropane. The solution was concentrated to small volume and diluted with ethanol contaning 5% of hydrochloric acid. The precipitate was then filtered and recrystallised from methanol. Yield 3.8 g. (Found: C, 64,39; H, 8.09; N, 5.91; Cl, 7.58; C25H38N2O4Cl requires: C, 64.45; H, 8.16; N. 6.01; Cl, 7.63): The pharmacological activity of compounds of the invention is illustration by the following data Toxicitv The results of determining the LD1() for the substance specified in Guinea Pigs by intravenous perfusion are shown in Table l.

Table 1 - LD1( by intravenous perfusion in the Guinea Pig LD1( expressed in mg./kg.

Substance No of animals Average t Standard Deviation Sandwicine 8 59.16 t 3.11 Isosandwicine 8 70.31 t 1.13 N-propyl sandwicine bitartrate 8 23.09 + 2.12 -Ajmaline 13 21.93 + 2.98 Anti-arrhythmic activity To test the activity of substances according to the invention in countering arrhythmia induced by aconitine, groups of male Guinea pigs weighing 400 t 25 grams were kept fasting from the evening prior to the test and anaesthetised with ethyl urethane. Aconitine hydrochloride in an isotonic solution of sodium chloride was perfused intravenously at a rate of 6.5 micrograms/minute until the appearance of arrhythmia was recorded on an electro-cardiograph.

The substances under examination were administered intravenously on two occasions (30 and 120 minutes prior to the administration of aconitine) at doses equivalent in their toxicity to 2 mg./kg. of ajmaline, i.e. doses of 5,5 and 2, mg./kg. respectively of sandwicine, isosandwicine and N-propyl sandwicine. From Table 2 it can be seen that while at 30 minutes after administration ajmaline no longer manifests significant activity, the other three substances display significant anti-arrhythmic active in comparison with the controls, both at 30 and at 120 minutes after their administration.

Table 2 - Arrhythmia Induced by Aconitine in the Guinea Pig Aconitine γ/kg.(2) (Average # S.D.) Substance Dose (1) mg./kg.

30' after administration 120' after administration Controls - 60.69 # 2.37 60.69 # 2.37 Sandwicine 5 126.72 # 7.38* 115.83 # 7.11* Isosandwicine 5 89.95 # 4.56* 70.84 # 2.39 N-propyl sandwicine 2 106.37 # 7.56* 127.73 # 10.43* Ajmaline 2 67.84 # 3.20 (1) The doses administered are equally toxic as a function of the LD100 by intravenous perfusion in the Guinea pig.

(2) Aconitone hydrochloride 6.5 γ/min. was perfused intravenously until the appearance of ventricular arrhythmia.

* Significantly (P < 0.001) different from the mean value of the controls (according to Student's "t" test).

Significantly (P < 0.01) different from the mean value of the controls (according to Student's "t" test)

Claims

The following examples illustrate pharmaceutical compositions according to the invention: Ampoules Sandwicine hydrochloride 20 mg Excipients (propylene glycol, sterile, pyrogen-free water for injection) up to ............. ....................................... 2 ml Drops 1) N-(1-diethylamino-2-hydroxy-propyl)-isosandwicine chloride ........................................ 300 mg Excipient (ethyl alcohol, propylene glycol, purified water) up to ................. 10 ml 2) N-propyl sandwicine bitartrate .............................................. 250 mg Excipient (ethyl alcohol, propylene glycol, purified water) up to ......... ...... ....... ....................... 10 ml Tablets Sandwicine .............................................................. ......

40 mg Excipients (starch, lactose, magnesium stearate, talc, arabic gum) up to ......... . ........ ....... .......... ............... 200 mg Capsules 1) N-propyl sandwicine bitartrate . . ............................. 80 mg Excipient: lactose up to . ....... . . @ 250 mg WHAT WE CLAIM IS: 1. A pharmaceutical composition comprising a pharmaceutically acceptable excipient and as active ingredient sandwicine, isosandwicine, a compound having the following structural formula

in which: R3 is an unsubstituted alkyl group or an alkyl group substituted by one or more hydroxyl. alkoxy. amino, alkvlamino or nitrogen-containing heterocyclic groups, R4 is hydroxy.

X- is a pharmaceutically acceptable anion, and either R' is a -OH and R6 is 3 -ethyl. or R5 is ss -OH and R" is a -ethyl or a pharmaceuticallv acceptable acid addition salt of sandwicine. of isosandwicine or of said compound of the formula II with the proviso that where he sole active ingredient is sandwicine. isosandwicine or a pharmaceutically acceptable acid addition salt of sandwicine or of isosandwicine and the sole excipient is water, the composition is sterile and pyrogen-free.

2. A pharmaceutical composition according to claim 1 in which R3 contains up to 15 carbon atoms.

3. A pharmaceutical composition according to claim 1 or claim 2 in which R' is an unsubstituted alkyl group.

4. A pharmaceutical composition according to claim 1 or claim 2 in which R3 is a lower alkyl group containing up to 6 carbon atoms.

5. A pharmaceutical composition according to claim 1 in which R is a lower alkyl group containing up to 3 carbon atoms.

6. A pharmaceutical composition according to claim 1 in which R3 is methyl.

7. A pharmaceutical composition according to claim 1 in which R3 is propyl.

8. A pharmaceutical composition according to any preceding claim in which R5 is a -OH and R6 is ss -ethyl.

9. A pharmaceutical composition according to claim 1 in which R3 represents an aminoethyl group of the formula -CH2.CH.NRr2 in which the moieties R7, which may be the same or different represent hydrogen atoms or alkyl groups or together with the nitrogen atoms to which they are attached form a heterocyclic ring.

10. A pharmaceutical composition according to claim 9 in which the moieties R7 represent alkyl groups.

11. A pharmaceutical composition according to claim 9 in which R3 is a 2-(piperid-1-yl )-ethyl group.

12. A pharmaceutical composition according to Claim 1 in which R3 represents a substituted propyl group of the formula -CH2.CHOH.CH2CH2NR72 wherein the R7 groups are as defined in Claim 9.

13. A pharmaceutical composition according to claim 12 in which R3 represents a 2-hydroxy-3-diethylamino-propyl group.

14. A pharmaceutical composition according to claim 1 in which R3 represents a substituted propyl group of the formula -CH2.CHOH.CH2OR8 wherein R8 represents a C,-6 lower alkyl group or a hydrogen atom.

15. A pharmaceutical composition according to claim 14 in which R3 represents a 2-hydroxy-3-ethoxy-propyl group.

16. A pharmaceutical composition according to claim 1 containing as active ingredient a compound selected from sandwicine, isosandwicine, isosandwicine methiodide, N-propyl sandwicine bromide, N-[(2-hydroxy-3-diethylamino)-propyl] -isosandwicine chloride, N-[2 (piperid-1-yl)-ethylj-sandwicine chloride and N-(2-hydroxyl-3-ethoxy) -propylisosandwicine chloride.

17. A pharmaceutical composition according to claim 1.comprising a pharmaceutically acceptable N-propyl sandwicine salt.

18. A compound of the formula II, or a pharmaceutically acceptable acid addition salt thereof,

where R3, R4 R5 and R6 areas defined in claim 1.

19 A compound according to claim 18 in which R3 is an unsubstituted alkyl group.

21. A compound according to claim 18 in which R3 is a lower alkyl group containing up to 6 carbon atoms.

22. A compound according to claim 18 in which R3 is a lower alkyl group containing up to 3 carbon atoms.

23. A compound according to claim 18 in which R3 is propyl.

24. A compound according to claim 18 in which R3 in methyl.

25. A compound according to any one of claims 18 to 24 in which Rs is a -OH and R6 is ss -ethyl.

26. A compound according to claim 18 in which R3 represents an aminoethyl group of the formula -CH2.CH1.NR7, in which the on moieties R7, which may be the same or different represent hydrogen atoms or alkyl groups or together with the nitrogen atoms to which they are attached form a heterocyclic ring.

27. A compound according to claim 26 in which the moieties R7 represent alkyl groups.

28. A compound according to claim 26 in which R3 is a 2-(piperid.1-yl)-ethyl group.

29. A compound according to claim 18 in which R3 represents a substituted propyl group of the formula -CH2.CHOH.CH2NR72 wherein the R7 groups are as defined in claim 26.

30. A compound according to claim 29 in which R represents a 2-hydroxy-3 diethylamino-propyl group.

31. A compound according to claim 18 in which R3 represents a substituted propyl group of the formula -CH2.CHOH.CH2OR8 wherein R8 represents a rel lower alkyl group or a hydrogen atom.

32. A compound according to claim 31 in which R3 represents a 2-hydroxy-3-ethoxypropyl group.

33. An N-methyl sandwicine salt.

34. An N-propyl sandwicine salt.

35. Isosandwicine methiodide.

36. An N-propyl sandwicine salt.

37. An N-propyl isosandwicine salt.

38. N-propyl sandwicine bromide.

39. An N-f(2-hydroxy-3-diethylamino)-propyl]-sandwicine or isosandwicine salt.

40. N-[(2-hydroxy-3-diethylamino)-propyl]-isosandwicine chloride.

41. An N-[2-(piperid- 1-yl)-ethyl]-sandwicine or isosandwicine salt.

42. N-[2-(piperid-1-yl)-ethyl]-sandwicine chloride.

43. An N-(2-hydroxy-3-ethoxy)-propyl-sandwicine or isosandwicine salt.

44. N-(2-hydroxy-3-ethoxy)-propyl-isosandwicine chloride.

45. A process for producing a compound as claimed in any one of claims 18 to 44 which process comprises reacting sandwicine or isosandwicine with an alkylating agent capable of introducing the required group R3.

46. A process according to claim 45 in which the akylating agent is an alkyl halide.

47. A process according to claim 45 in which the alkylating agent is an N-substituted or unsubstituted aminoalkyl halide of the formula Hal.CH2.CH2.NR72 wherein Hal represents a halogen atom and each R7 is as defined in Claim 26.

48. A process according to claim 45 in which the alkvlatinp agent is a substituted epoxypropane of the formula

wherein each R7 is as defined in claim 26.

49. A pharmaceutical composition according to claim 1 and substantially as hereinbefore described and exemplified.

50. A process for producing a compound as claimed in any one of claims 18 to 44 and substantially as hereinbefore described and examplified.