Azobenzene derivatives with a long alkyl chain and aminoxyls

A trans-azobenzene derivative with a long alkyl chain and a TEMPO radical showed photo-induced isomerization to become the corresponding cis-isomer with a significant change of its intermolecular magnetic interaction from a weak ferromagnetic one based on the CW model to a relatively strong antiferromagnetic one based on the ST model with the J-value of 36.7 K.     

8-Methylguanosine: a powerful Z-DNA stabilizer

Various modified guanine derivatives were synthesized and introduced into G(4) of d(CGCGCG)(2) to evaluate their capacity to stabilize Z-form DNA. It was found that the incorporation of 8-methylguanosine (m(8)rG) in oligonucleotides stabilizes the Z form more dramatically than does the incorporation of 8-methyl-2'-deoxyguanosine (m(8)G). This enhancement is ascribed to a reduction in the entropic penalty, which arises from the introduction of hydrophilic groups in solvent-exposed regions. The incorporation of m(8)rG into DNA sequences markedly stabilizes the Z form even in the absence of NaCl. The Z-DNA stabilizer allows oligonucleotides with a wide range of sequences to be converted to the Z form. It could be a powerful tool for examining the molecular basis of many types of Z-form-specific reactions at the molecular level under physiological salt conditions.     

Total synthesis of γ-lycorane

The homophthalimide derivative was easily converted to the cis-octahydrophenanthridine derivative in good yield and this to γ-lycorane 1 (1).     

Final Session of ESTAC 4

Final Session of ESTAC 4     

Absolute cross sections for the 6Li(p, 3He)4He reaction at energies below 1 MeV

Total cross sections and angular distributions in the ⁶Li(p,³He)⁴He reaction have been measured over the energy range E_p = 100?700 keV. The extrapolation of the cross section to the energy region which is of interest in controlled thermonuclear reactors is given. The values of the “astrophysical S-function” are deduced from the cross sections.