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In connection with studies of 2H-benz[cd]azulene (1) [¹] and the strongly acidic fluoradene (2) [²] particular interest[²⁻⁶] attaches to the parent system of the latter, 2aHcyclopent[cd]indene (3) and its 1 H-isomer (4) as well as to their anion (5) which is isoelectronic with [3.2.2]cy-clazine (6)[³].

Im Zusammenhang mit Untersuchungen über das 2HBenz[cd]azulen (1) [¹] sowie das hochacide Fluoraden (2)[²] kommt dessen Grundkörper, dem 2aH-Cyclopent[cd]inden (3) und dessen 1H-Isomeren (4) sowie deren Anion (5) , das dem Cycl[3.2.2]azin (6)[³] isoelektronisch ist, besonderes Interesse zu[²-⁶].

Combination of enantioselective allylation reactions with a tandem hydroformylation–Fischer indole synthesis sequence as a highly diversity-oriented strategy for the synthesis of tryptamines and homologues was explored. This modular approach allows the substituents at C3 of the indole core, the type of the amine moiety, and the distance of the amine moiety to the indole core in the final synthetic step to be defined. The starting materials required for the hydroformylation step were synthesized viairidium catalyzed enantioselective allylic substitution reactions in high yields and excellent enantioselectivities. The Rh catalyzed hydroformylation step in the presence of phenyl hydrazine, allows the in situ formed aldehyde to be trapped as the hydrazone. Subsequent acid catalyzed indolization furnishes the desired indole structures in moderate to good yields.

Mixed tetraoxanes 5a and 13 synthesized from cholic acid and 4-oxocyclohexanecarboxylic acid were as active as artemisinin against chloroquine-susceptible, chloroquine-resistant, and multidrug-resistant Plasmodium falciparum strains (IC50, IC90). Most active 13 is metabolically stable in in vitro metabolism studies. In vivo studies on tetraoxanes with a C(4'') methyl group afforded compound 15, which cured 4/5 mice at 600 and 200 mg, kg(-1), day(-1), and 2/5 mice at 50 mg, kg(-1), day(-1), showing no toxic effects. Tetraoxane 19 was an extremely active antiproliferative with LC50 of 17 nM and maximum tolerated dose of 400 mg/kg. In Fe(II)-induced scission of tetraoxane antimalarials only RO center dot radicals were detected by EPR experiments. This finding and the indication of Fe(IV)=O species led us to propose that RO center dot radicals are probably capable of inducing the parasite's death. Our results suggest that C radicals are possibly not the only lethal species derived from peroxide prodrug antimalarials, as currently believed.

Mixed tetraoxanes 5a and 13 synthesized from cholic acid and 4-oxocyclohexanecarboxylic acid were as active as artemisinin against chloroquine-susceptible, chloroquine-resistant, and multidrug-resistant Plasmodium falciparum strains (IC50, IC90). Most active 13 is metabolically stable in in vitro metabolism studies. In vivo studies on tetraoxanes with a C(4'') methyl group afforded compound 15, which cured 4/5 mice at 600 and 200 mg, kg(-1), day(-1), and 2/5 mice at 50 mg, kg(-1), day(-1), showing no toxic effects. Tetraoxane 19 was an extremely active antiproliferative with LC50 of 17 nM and maximum tolerated dose of 400 mg/kg. In Fe(II)-induced scission of tetraoxane antimalarials only RO center dot radicals were detected by EPR experiments. This finding and the indication of Fe(IV)=O species led us to propose that RO center dot radicals are probably capable of inducing the parasite's death. Our results suggest that C radicals are possibly not the only lethal species derived from peroxide prodrug antimalarials, as currently believed.