In this short review, recent developments in the syntheses of antisense DNAs are described. The antisense DNA/RNA method is one of the ways to regulate gene expression specifically and uses sequence specific DNAs and their analogs, namely antisense DNAs. They have been designed and synthesized in order to meet requirements, for use in living systems, such as selectivity, nuclease resistance, cell membrane permeability, and duplex stability. The design is mainly focused on the modification of phosphate backbones, the modification of sugar moieties, and the introduction of functional molecules into antisense DNAs. The ability of these antisense DNAs to regulate gene expression are also discussed as well as biological studies.
Bleomycins (BLMs) are antitumor antibiotics of unusual glycopeptide structure. The potent activity of BLM is attributed to the oxygen activation and the DNA cleavage by the formation of iron-chelate of the peptide moiety. erythro-β-Hydroxy-L-histidine, a pivotal amino acid for the oxygen activation, is prepared enantioselectively by aldol reaction of (R) -3-bromoacetyl-4-isopropyl-1, 3-oxazolidin-2-one with 1-triphenylmethylimidazole-4-carbaldehyde. Model ligands for the metal binding site of BLM with 4-methoxypyridine (PYML-6) and 4-dimethylaminopyridine (PYML-8) show oxygen activation up to 97% and 125% of that of BLM, respectively. cis-β-Methylstyrene is oxidized either with Fe (III) -H2O2 or Fe (II) -O2 complex systems of BLM and PYML-6 to give the corresponding optically active epoxide. The DNA binding region of BLM is combined with PYML-6 to give the first man-designed BLM, PYML (6) -bleomycin, which shows nucleotide cleavage mode remarkably similar to that of BLM. On the other hand, PYML-6 moiety and distamycin are coupled to afford PYML (6) - (4R-APA) -distamycin which shows dramatically altered AT specific mode in the DNA scission.
A general total synthetic methodology for indole alkaloids via the route involving reductive photocyclization of enamides has been developed. Acylation of imines such as harmalane and tricyclic imine with either p-methoxybenzoyl or 3-furoyl chloride followed by reductive photocyclization furnished the compounds having skeletal structures of indole alkaloids, yohimbines and ergolines. They were then readily converted, upon modification of either methoxylated dihydrobenzene or dihydrofuran ring to respective alkaloids including yohimbine, alloyohimbine, deserpidine, and 19, 20-dehydroyohimbine in one group and lysergic acids, elymoclavine, agroclavine, lysergols, lysergines, and fumigaclavines in another group.
Some optically active diaryl selenoxides stabilized by bulky oitho substituents such as isopropyl or t-butyl group were obtained by fractionary recrystallization or by chromatographic resolutions. Optically active alkyl aryl selenoxides were synthesized by asymmetric oxidation of corresponding selenides under Sharpless oxidation conditions The absolute configurations of these optically active selenoxides were determined by X-ray diffraction and circular dichroism spectra. The rate of racemization of the optically active selenoxide under several conditions were investigated, and the mechanism involving achiral hydrate was clarified by H218O studies.