Synthesis and biological evaluation of quinocarcin derivatives

Cyanation of quinocarcin readily opened the oxazolidine ring to provide DX-52-1 (2), which was a key compound in the synthesis of quinocarcin derivatives. Various electrophilic reactions toward aromatic ring of DX-52-1 were examined, and 10-substituted (e.g., halogen, nitro, formyl, cyano, hydroxy, etc.) analogs were prepared. Dehydrocyanation of the derivatives could be achieved to reproduce the oxazolidine ring upon treatment with HCl or AgNO3. 10-Chloride 10 and 10-bromide 11 were the most promising among the derivatives prepared. Antitumor activity of 10 was extended to B-16 melanoma.     

Isolation of Magnetospirillum magneticum AMB-1 mutants defective in bacterial magnetic particle synthesis by transposon mutagenesis

Nonmagnetic mutants of Magnetospirillum magneticum AMB-1 were recovered following mini-Tn5 transposon mutagenesis. Transconjugants with kanamycin resistance were obtained at a frequency of 2.7 × 10⁻⁷ per recipient. Of 3327 transconjugants, 62 were defective for bacterial magnetic particle (BMP) synthesis. The frequency of independent transposition events for nonmagnetic mutants was about 1.4% in transconju gants. Further analysis of DNA sequences flanking transposon by inverted polymerase chain reaction allowed isolation of at least 10 genes or DNA sequences involved in BMP synthesis in M. magneticum AMB-1.     

Amplification of Dense Spectra of XeCl Excimer

Amplification process in an excimer laser of dense modes is studied. Rate-equations with wavelength dependence are used to reproduce its spectra. Two extreme cases are tried and in spite of the duration of the output pulse relative to the relaxation time, the short pulse limit is proved to describe well the oscillation process of individual mode.     

Diacylated 8-C-glucosylcyanidin 3-glucoside from the flowers of Tricyrtis formosana

A new diacylated 8-C-glucosylanthocyanin was isolated from the purple flowers of Tricyrtis formosana 'Fujimusume' as one of the major anthocyanins along with four known pigments. The structure of this pigment was determined to be 8-C-(6-O-trans-sinapoyl)-beta-glucopyranosylcyanidin 3-O-(6-O-malonyl-beta-glucopyranoside) by chemical and spectroscopic methods. In addition, four known pigments, 8-C-glucosylcyanidin 3-malonylglucoside, cyanidin 3-glucoside, cyanidin 3-rutinoside and cyanidin 3-malonylglucoside, were identified as the major anthocyanins in the flowers.     

Observation of the 7 MeV excited spin-flip and non-spin-flip partners in 16 ΛO by γ -ray spectroscopy

We have observed three γ -ray transitions in _Λ ¹⁶ O from both 7MeV excited spin-flip and non-spin-flip partners ( 2^-, 1^- ₂ to the ground-state doublet ( 1^- ₁, 0^- via the ¹⁶O(K ^-,π^-) reaction. The 7MeV excitation energies of the spin-doublet members ( 2^-, 1^- ₂ were determined to be 6784±4±4 keV and 6562±1±2 keV, respectively, and thus the spacing was obtained to be 222±4±5 keV. This is the first observation of the spin-flip state directly populated by the ( K ^-,π^- reaction. Moreover, such directly populated spin-flip and non-spin-flip partners were resolved for the first time.     

Tetracyclopenta[def,jkl,pqr,vwx]tetraphenylene: A Potential Tetraradicaloid Hydrocarbon

A tetramesityl derivative of hitherto unknown tetracyclopenta[def,jkl,pqr,vwx]tetraphenylene (TCPTP), which is a potential tetraradicaloid hydrocarbon, was synthesized. Theoretical calculations based on spin‐flip time‐dependent density functional theory predict that the closed‐shell D_2h form of TCPTP is more stable than the open‐shell D_4h form with its slightly tetraradical character. The tetramesityl derivative (Mes)₄‐TCPTP exhibits remarkable antiaromaticity as a result of the peripheral 20‐π‐electron circuit, which causes an absorption maximum at a long wavelength and a small HOMO–LUMO gap. In solution, (Mes)₄‐TCPTP most likely adopts rapidly equilibrating D_2h structures that interconvert via the D_4h transition state. X‐ray crystallographic analysis showed (Mes)₄‐TCPTP as an approximate D_2h structure.