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A series of diastereomeric dihydroartemisinin alpha-alkylbenzylic ethers was synthesized in search for analogs with higher antimalarial efficacy and longer plasma half-life than the existing artemisinin derivatives. Artelinic acid was used as the model molecule for the design of new analogs. Two approaches were taken in an attempt to (a) increase the lipophilicity of the molecule and (b) decrease the rate of oxidative dealkylation of the target compounds. All compounds in this study showed at least equal or better in vitro antimalarial activity against Plasmodium falciparum than artelinic acid. The most active compounds of this series showed 10-, 20-, and 40-fold better inhibitory activity than artemether, artemisinin, and artelinic acid, respectively. Compounds which have a small methyl group substituted at the alpha-methylene group showed weaker activity than compounds with a larger carbethoxyalkyl substituent, indicating that the lipophilicity and the steric effect of the molecules play important roles in their antimalarial activity. This fact is further substantiated by the significantly weaker antimalarial activity of the carboxylic acids than their corresponding esters. Compounds with electron-withdrawing function (NO2) substantially increase the antimalarial activity. The S-diastereomers, in general, are severalfold more potent than the corresponding R-isomer.

Halogenated 4-(3,3-dimethyl-1-triazeno)quinolines were synthesized as potential antitumor agents on the basis of the biochemical pharmacological properties of existing triazenes, their structural-activity relationships, and the high melanin binding of chloroquine and iodoquine in vivo and in vitro. They were synthesized by diazotization of appropriate halogen-substituted 4-aminoquinolines in fluoboric acid at -5 degrees C followed by coupling with dimethylamine. Among these new compounds, 8-chloro-4-(3,3-dimethyl-1-triazeno)quinoline produces significant antitumor activity against both P-388 and L1210 murine leukemias. Although only marginally active or inactive against P-388, the other chloro, bromo, or iodo analogues show activity against L1210 comparable to that of dacarbazine (DIC). However, none of these compounds is active against B-16 melanoma. Compared with DIC these new agents demonstrate a higher in vitro affinity for melanin; however, this affinity is apparently not correlated with their antitumor activity.

A number of hydroquinone dialdehydes and structurally related compounds were synthesized and tested for antineoplastic efficacy against transplanted murine tumors. 3,6-Dihydroxy-4,5-dimethylphthalaldehyde,3,6-dihydroxy-4,5-dipropylphthalaldehyde, and 3,6-dihydroxy-4,5-dimethylphthalaldehyde hemialdal tetraacetate significantly prolonged the survival time of mice bearing either Sarcoma 180, Ehrlich carcinoma, or adenocarcinoma 755 ascites tumors. In addition, these agents were cytotoxic to Sarcoma 180 cells in culture at concentrations in the range of 25-30 microM.

Functional groups such as nitro, chloro, bromo, and methoxy were introduced in the meta and para positions of the phenyl ring of the antineoplastic agent 2-chloromethyl-3-phenyl-1,4-naphthoquinone. Tests for tumor-inhibitory potency of these derivatives against Sarcoma 180 ascites cells in mice indicated that the para-substituted methoxyphenyl, chlorophenyl, and bromophenyl derivatives possessed antitumor activity comparable to that of the parent compound 2-chloromethyl-3-phenyl-1,4-naphthoquinone, whereas meta-substituted nitro and bromo derivatives were either inactive or only weakly active anticancer agents in this system.

Agents were designed to exploit the high tyrosinase activity in melanotic melanoma relative to normal tissues. If specific tyrosinase activation of these agents occurred, the production of toxic metabolites in the melanoma cells would produce selective cell kill. Synthesis and antitumor activities of three new amino acids, 1a [beta-[(p-hydroxyphenyl)amino]alanine hydrochloride], 1b [N delta-(p-hydroxyphenyl)ornithine hydrochloride], and 1c [N delta-(m-hydroxyphenyl)ornithine dihydrochloride], were described. Compounds 1a and 1b were approximately 2-fold more active against the B-16 melanotic melanoma than the amelanotic melanoma cell line in vitro. Compound 1b was approximately 2-fold more potent than compound 1a against either cll line and was 8-fold more potent than L-glutamic acid gamma-(4-hydroxyanilide), a natural product isolated from mushroom. No significant growth inhibitory activity was found for the m-hydroxy analogue 1c at 100 micrometers, the highest concentration tested. Similarly, compound 1b exhibited better activity against P-388 (ED50 = 9.5 x 10(-6) M) than 1a (ED50 = 3.2 x 10(-5) M) and was about 30-fold more potent than 1c. Against human epidermoid carcinoma of the nasopharynx (KB), these agents showed modest inhibitory activity with ED50 values in the range of 1.2 to 3 x 10(-4) M. No in vivo activity against P-388 and B-16 at doses up to 150-200 mg/kg was observed. The biological results suggest that a nonspecific oxidation rather than a specific tyrosinase activation is involved in the biological action of these new compounds.

Four isomers of ftorafur were synthesized as authentic samples of possible ftorafur (FT) metabolites. 2,3-Dihydrofuran was treated with perbenzoic acid in MeOH to give 2-methoxy-3-hydroxytetrahydrofuran, which upon treatment with Ac2O/pyridine yielded the key intermediate 2-methoxy-3-acetoxytetrahydrofuran. The other intermediate, 2-ethoxy-4-acetoxytetrahydrofuran, was prepared by acid hydrolysis (HCl/50% EtOH) of 1,1-diethoxy-3,4-dihydroxybutane, followed by acetylation (Ac2O/pyridine). Treatment of 2,4-bis(trimethylsilyl)-5-fluorouracil with either 2-methoxy-3-acetoxytetrahydrofuran or 2-ethoxy-4-acetoxytetrahydrofuran in 1,2-dichloroethane at room temperature using SnCl4 as catalyst afforded cis- and trans-3'-OAc-FT or 4'-OAc-FT, respectively. However, trans-3'-OAc-FT and cis-4'-OAc-FT were the major condensation products. In each case, separation of these cis and trans isomers was achieved by silica gel column chromatography. Treatment of 3'- or 4'-OAc-FT with NH3/CH3OH at 5 degrees C overnight yielded the described hydroxylated FT. Both trans-3'-OH-FT and cis-4'-OH-FT showed no significant activity against L1210 up to 100 mg/kg. These two agents produced an inhibitory effect on HeLa cell growth equal to that of ftorafur, with ID50 = 200 MICROGRAMS/KG.

A new series of hydrolytically stable and water-soluble dihydroartemisinin derivatives with optically active side chains was prepared as potential antimalarial agents. This was an effort to prepare compounds with activity superior to that of artelinic acid and to examine the impact of the stereospecificity of the introduced alkyl side chain on biological properties. The ester derivatives (6a-d) possess superior in vitro activity to artemisinin, artemether, and arteether against two strains of Plasmodium falciparum (D-6 and W-2); however, conversion of the esters to their corresponding acids drastically reduces their antimalarial activity. None of the new acids possess in vitro antimalarial activity superior to that of artelinic acid. Although there appears to be limited stereospecificity for antimalarial activity among the acids (7a-d) tested, significant differences in antimalarial activity was seen among the esters.

The usefulness of sodium artesunate (3), a water-soluble derivative of artemisinin (1), is impaired by its poor stability in aqueous solution. To overcome the ease of hydrolysis of the ester group in 3, a new series of derivatives of dihydroartemisinin (2) was prepared in which the solubilizing moiety, which contains a carboxylate group, is joined to dihydroartemisinin by an ether rather than an ester linkage. The new derivatives were prepared in good yield by treatment of dihydroartemisinin with an appropriate alcohol under boron trifluoride etherate catalysis at room temperature. All major condensation products are the beta isomer. Hydrolysis of the esters with 2.5% KOH/MeOH gave the corresponding potassium salts, which were converted to free acids (8b-d) by acidification. The derivatives were tested in vitro against two clones of human malaria, Plasmodium falciparum D-6 (Sierra Leone clone) and W-2 (Indochina clone). No cross-resistance to the antimalarial agents mefloquine, chloroquine, pyrimethamine, sulfadoxine, and quinine was observed. In general, the new compounds are more effective against the W-2 than the D-6 strain. Esters (5a-d) possess activity comparable to that of the parent compounds 1 and 2; however, conversion of the esters to their corresponding carboxylates (7a-d) or acids (8b-d), with the exception of artelinic acid (8d), drastically decreases the antimalarial activities in both cell lines. Artelinic acid, which is both soluble and stable in 2.5% K2CO3 solution, possesses superior in vivo activity against Plasmodium berghei than artemisinin or artesunic acid.