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Unusual course of the reaction was revealed on the oxidation of functionally substituted acridine containing the activated methyl groups by well-known oxidants, such as selenous acid and selenium(IV) oxide. Treatment of 2-methoxy-4,9-dimethyl-1-nitroacridine (5) with an excess of H2SeO3 in boiling ethanol gave a mixture of the normal reaction products, 2-methoxy-4-methyl-1-nitro-9-formylacridine (11) (isolated yield 29%) and 2-methoxy-4-methyl-1-nitroacridine-9-carboxylic acid (12) (36%), together with an abnormal product, 3-methoxy-5-methyl-1H-selenopheno[2,3,4-k,l]acridine-1-one (13) (21%), which is the first example of a new seleno-containing ring system. With the use of SeO2 the yield of selenolactone 13 was much lower. J. Heterocyclic Chem., 2011.

It is shown that the Michael-type adducts with cyclohexanone or methyl vinyl ketone at C-3 exist as a mixture of open-chain and cyclic tautomers in CDCl3 solutions, whereas adducts with cyclopentanones at C-3 exist only in the open-chain form.

Polycarpine 1 , a highly cytotoxic marine natural product, has been synthesized in three steps from p-methoxyphenacyl bromide 4 in 57% overall yield. The key reaction for construction of the symmetrically substituted disulfide linkage of polycarpine is the treatment of 2-amino-4-(4-methoxyphenyl)-1-methylimidazole 17 with S2Cl2 in acetic acid. In a similar way ten related compounds, including three thiazole analogues, have been prepared. Most of them exhibit high cytotoxic activities against an array of human cancer cell lines.

Fascaplysin 1, an antimicrobial and cytotoxic red pigment of the marine sponge Fascaplys-inopsis sp., has been synthesized in five steps from tryptamine 2 in 44% overall yield. The key steps in the synthesis are: (a) dehydrogenation of the dihydro-β-carboline intermediate 4 simultaneously with its benzylic oxidation on treatment with MnO2 and (b) the thermal cyclization of the resulting β-carboline 7 into a quaternary salt 8. Similarly, indoloisoquinolines 15 and 16, the tetracyclic analogues of 1, were prepared in six steps from α-amino ketone 9 in 59 and 55% overall yields, respectively.

A simple and practical approach for the synthesis of the marine sponge pigment fascaplysin was used for the total syntheses of its natural derivatives, the marine alkaloids 3-bromofascaplysin, 10-bromofascaplysin, and 3,10-dibromofascaplysin. The conditions of each step were revised, and as a result these compounds were produced by identical procedures with total yields of 40–43%.

Two new diprenylquinones, glabruquinone A (desmethylubiquinone Q 2 ) having cancer preventive properties and its minor isomer Glabruquinone B were isolated from the ascidian Aplidium glabrum . Their structures have been elucidated by NMR and mass spectra and confirmed by synthesis.