Synthetic studies on the bracken ultimate carcinogen (3) and its artificial analogues (32, 33) are described. The synthesis of (-) -ptaquilosin (2) the aglycon of a potent carcinogen ptaquiloside (1) from bracken and its (+) - enantiomer (ent- 2) was achieved starting with (+) -dimenthyl (1R, 2R) -cyclopentane-1, 2-dicarboxylate. Dehydration of ptaquilosin (2) under weakly basic conditions led to the ultimate carcinogen (3). DNA cleaving activities of both enantiomers (3) were compared, the one (3) derived from natural (-) -ptaquilosin (2) being more efficient. Reactivities of the ultimate carcinogen (3) toward DNA are described. DNA was shown to be alkylated at the particular sites of purine bases and to undergo cleavage. The molecular mechanism of DNA cleavage with the ultimate carcinogen (3) was disclosed using deoxytetranucleotide d (GTAC) as a model DNA substrate.
The conformational changes among several conformational isomers of calix  arenes can take place because the OH groups rotate through the annulus. This inversion was inhibited by the introduction of the substituents bulkier than ethyl group into the OH groups and the resulting conformational isomers were separated. The selective syntheses of all partially O-propylated compounds and conformational isomers in p-tert-butylcalix  arene were successful by the combination of protection-deprotection method and the optimization of the reaction conditions (base, temperature, solvent, etc). Several of these compounds can possess the chirality which is caused by the disappearance of the symmetries on the conformation or based on the order in the array of different substituents. We succeeded in the syntheses and the optical resolutions of these calixarenes with molecular chirality for the first time.
Optically active hydroxy acids have growing interests as the starting material of biologically active natural products. The authors have been studying the application of biocatalysts to the asymmetric synthesis of hydroxy acids. In this article, the following topics are shortly reviewed : 1) lipase-catalyzed kinetic resolution of α-benzyloxy esters;2) preparation and the synthetic utilization of optically active cyanohydrins;3) preparation of optically active mandelic acid via stereoselective oxido-reduction;4) lipase-catalyzed kinetic resolution of α- and, β-hydroxy acids;5) stereoselective reduction of β-keto esters;6) kinetic resolution in lipase-catalyzed lactonization;7) aldolase-catalyzed synthesis of sialic acid and its analogs.
Preparation and reaction of trifluoroacetimidoyl halides 1 a (X=Cl), b (X=Br), c (X=I) have been summarized. Chemistries of three types of reactive intermediates, trifluoroacetimidoyl carbocations, carbanions and radicals were discussed. Reactions of 1 a with various nucleophiles proceeded smoothly, while palladation, zincation and lithiation of 1 c enabled carbon-carbon bond formation with electrophiles at the imidoyl carbon Meanwhile, photolysis of 1 c provided the corresponding radicals which underwent intramolecular cyclization leading to 2-trifluoromethylindoles.
Group 14 metals such as silicon, germanium, and tin promote electron-transfer from a π-system and a heteroatom situated at the β position. On the basis of this effect, several electroorganic rections have been developed. Especially, the effective inter- and intra-molecular carbon-carbon bond formation reactions have been achieved by anodic oxidation of heteroatom-substituted organotin compounds.