SOM.2, ATTEMPTS TO PREPARE NEW COMPfUNDS OF POSSIBLE ANTIMALARIAL ACTIVITY. by Barbara- Evelyn.Halcrow, B.Sc. Thesis presented for the Degree of Ph.D., University of Edinburgh. LZay, 1N-4. -1- Contents. Page . 1. Introduction and General Survey of the Literature ................ .............. 2 II. Attempts to synthesise hydroxy- and chloro- derivatives of o- phenanthroline from 8- amino- quinoline and its derivatives 28 III. Synthesis of 4- chloro -8- nitro- and 4- chloro- 37 8- amino -quinaldines with the object of synthesising o- phenanthrolines from the latter. A study of the nitration of 4- chloro- quinaldine, and the synthesis of 4:8- disubstituted quinaldines IV. Synthesis of o- phenanthroline and its 53 conversion to a number of basically substituted derivatives V. Synthesis of derivatives of 2:3, 4':3'- 65 pyridoquinoline VI. Experimental ........ ..... ........ 74 VII. Summary 118 1. IT] RC-1DUCTION AND (..;....RAL SI:JRVII-;Y OF TH3 LITIiIRATURE. -3- INTRODUCTI - BURVEY OF TnE LI`l'_;RrsTURL. The value of cinchona bark in relieving fevers was known for many centuries before pure quinine was first extracted from it in 1820 and used in the treatment of malaria. Important advances in the control of malaria came with the discovery of the plasmodia in 1880 _by Laveran, and the disclosure by Ross that the anopheline mosquito is the transmitting agent for the. disease. Chemotherapeutic research into the problem began about 1890, when Ehrlich and Guttmann showed that methylene blue was antimalarially active but much less so than quinine. Rabe's announcement in 1908 of the now accepted structure of quinine stimulated attempts to prepare some of the cinchona alkaloids and their derivatives. In 1913 haúfmann (3er., 46, 1823) synthesised a number of simple quinoline derivatives whose structure resembled that of quinine. he prepared dialkylaminomethyl- 6- ethoxy- 4- ouinolyl- carbinols (IX, R = C2H5), which he reported as being of low toxicity to humans but of high toxicity to infusoria and paramoecia. These compounds were tested. later and found to be inactive on avian malaria. The synthesis of the two drugs plasmoquin and etch rin/ -4- atebrin which with :quinine are mainly used at present as antimalarials, came as a result of j researches by $chuleman and his colleagues who I began by modifying the methylene blue molecule (I) . The activity was found to be enhanced when one of the methyl groups was replaced by a diethylaminoethyl group (II) . I. N3C / CH3 N Gi,.-GN,- N HS II. This/ -5- This word led'to the introduction of similar groups into the quinoline nucleus and ultimately to the development of plasmocj .in or 8-(-methyl-- diethyl aminobutylaino) -6- methoxy- quinoline. (III) N3C o NH CFF -CH3 CH CH a CHz- N (C,.Ns)a A natural extension of this work was the trial of similar substituents in other ring systems. This research led Mietsch and Mauss (Angew. 47, 633) to the synthesis of ate'prin or 2- chloro -5- (a(- methyl -S- diethylaminobutylamino) - 7- methoxy- acridine (IV), which possesses an acridine nucleus and which has a considerably lower toxicity than plasmoquin. In general, all these drugs, quinine ate; rind and plasmoquin, act on both the schizonts and gametocytes of Plasmodium vivax (benign tertian Malaria) and Plasmodium malariae (quartan Malaria). On Plasmodium falciparum (malignant tertian malaria) however, quinine and atebrin are schizonticidal only, whereas plasmoquin acts on the gametocytes and not on the schizonts. A paper has been published by Curd(Ann. of Trop. Med. and Parasit. Vol. 37 No 2 1943) in which are collected results available in the literature of the relative activities of various drugs on a large number of species of malaria parasite in their respective hosts. The method used tó test synthesised compounds for their antimalarial activity was devised by Roehl at Elberfield and published in 1926. The potential antimalarial is given by mouth to canaries infected with avian .malaria, and the time taken for parasites to appear in the blood is compared .ith that for a non -treated bird. One of the disadvantages/ -7- disadvantages of this method is that the effect of a compound on'the parasites of avian malaria may be different from that on the parasites of human malaria. For example, sulphanilamide compounds which have so far been tested are most active against monkey malaria and to a lesser extent on húman malaria, but their activity on avian malaria is almost wholly lacking. Again, the action of a drug upon two species of parasite within the same host may differ. Sulphanilamide, in a mixed infection of P. knowlesi and P. inui in monkeys, eliminates P. knowlesi but -is inactive on P. inui. It is ::znownl too that arsenical drugs have considerable action against P. vivax infections but little or none against P.malariae and P. falciparum. In recent years other birds, especially chickens and ducks, are being used in the place of canaries for large scale preliminary tests. Since plasmoquin and atebrin were synthesised, a great amount of work has been done on the problem of the relationship between chemical structure and antimalarial activity. The existence of activity comparable with that of quinine in compounds such as cinchonine (V, R = H, R' ,= CH: C J) and dihydroguinine (V, R = OCH3, R' = CE2. CH3) shows that the methoxy and vinyl groups of quinine (V, R = OCH3, R' = CII: CIT3) can be Modified without loss of activity. On the other/ -8- other hand, changes in the secondary alcohol ( -CEO I) group, e.g. chlorination (- CIC1 -), acetylation (- CHOAc -), reduction (-G42-), oxidation ( -CO- ) etc., cause a disappearance of activity. CH CH-Ri CH). CHx CI-40'1-CH I i+H } N N V. Oxidation of quinine under certain conditions yields the inactive acid quitenine (V, R = OCH3, R' = -C00ìí) where the vinyl group is replaced by a carboxyl group. Activity however is restored on esterification, and it was found by Goodson that the activity increases with the molecular weight of the alcohol used for esterification, until it reaches a maximum at the butyl or amyl compound, after which there is a decrease in activity. A great many compounds closely related to ' plasmoquin and atebrin have been prepared and tested, chiefly by I4agidson in Russia, Fourneau in France and Robinson in Britain, and this work has brought to light many interesting phenomena. -c_ A curious alternuition in the activity of ::embers of a series of 6- methoxy- 8- dialkylarlinoalkyla:nino- quinolines (VI) was noted by Mazidson (Terapeutichesky árkhiv. 15, 65,3, 137) 143C o NH N(CaH,)a The chemotherapeutic'indices for different values of "n" were found to be n a 3 1+- 5 6 7 8 9 lo ,i.. ai as 33.3 40 s /3 /3.3 i° ,(, 6 - This type of alternation is not generally found,. for Magidson and 8trukov in the same paper reported that when the, side -chain in position 8 was kept constant at -NH (CIS )2 îT(Ca n5 )2 and the group in position 6 varied. from -OH to -OCsii , there was a continuous but irre filar fall in the chemotherapeutic indices: - -0H -OCH3 -0C2 H3 -OCaH7 -004H9 -0051i 1 13.3 6 4 1 1 0 2:1though/ -10- Although hydroxy and ethoxy compounds show appreciable activity, the choice of the methoxy group in compounds receiving medical trial is well founded, for no other group has proven superior in tests on birds, a superiority due in part to the lesser toxicity of the methoxy group over the other substituents tried. Again we may consider a series of acridines. Magidson and Grigorowski(Chemico -Pharm.Ind.(U.S.S.R) No.., 1, 1933) foLind that in 2- chloro- 7- !nethoxy- acridines substituted in position 5 by the chain -NH(CHa)nN(C2H8)2 where n = 2 to 6,. the chemo- therapeutic activity increased with n and then decreased,showing a maximum at n = 4 In 193, Magidson and Rubtzow(J.Gen.Chem. Russ., 1937 1896 -1908) described the preparation of some 4-dialkylaminoalkylamiiio-6- methoxy- quinolines (VII). NH CO VII. '- CH(CH3) CHx .CIi2 CH2 .N(C2Hs)2 R: -CH2.CHOH.CH2- N(C2H5)2 -(C )4N(C2H5)2 These were found to be active against bird malaria, but analogous compounds substituted in the 2- position instead of the 4- position were found by a the/ 1 same authors to -be completely inactive. This was confirmed by 8chonhofer (Zeit. f. Physiol. Chem., 1942, 2742 1. ) , who showed that besides compounds of the plùsmoquin type, quinoline derivatives substituted in the 4- and 6- position by a dialkyl- aminoalkylanino side -chain were active, but inactive compounds were obtained if this side -chain were In any other position. A number of compo-.nC.s having a structure resembling that of quinine has been synthesised by King and his colleagues. Among these compounds were 4- (6- methoxy- quinoly1)-- ol- piperidyl- carbinol (VIII) (Ainley and King, Proc.Roy. Soc., 1933, 125 3, 60) and d.ibutyl -, diamyl -, and dihexyl- amino- methyl-6- methoxy- 4- quinolyl- carbinols (IX, R = 0Ií3), (King and Work, J.C.3., 1940, 1307). CN- C H CHa I 'CHoH-eli Ha , NH R3c o RI CHoN - CHx N R IX. These/ asau, spLlnOdti'.c0 0,113 san::oTOoLj jo asoLj; pziJrdaJd cf uuru_3nn7 'otjm q.T sT °uT*sadc4uT o; aOT;ou ' MrO JraU o; "uTJrdadd aLj; ;sJT,T a1LT;Or OT;aL¿w1"s TrTJrT:mT;Ltr. saOUrorsqns aLjI Tn;ssaOOns a.LTau.;raJ; JO rTJrTrt.. 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