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Syntheses, electronic structures in the ground state, unique photoexcited states, and spin alignment are reported for novel biradical 1, which was designed as an ideal model compound to investigate photoinduced spin alignment in the excited state. Electron spin resonance (ESR), time-resolved ESR (TRESR), and laser-excitation pulsed ESR experiments were carried out. The magnetic properties were examined with a SQUID magnetometer. In the electronic ground state, two radical moieties interact very weakly (almost no interaction) with each other through the closed-shell diphenylanthracene spin coupler. On photoirradiation, a novel lowest photoexcited state with the intermediate spin (S = 1) arising from four unpaired electrons with low-lying quintet (S = 2) photoexcited state was detected. The unique triplet state has an interesting electronic structure, the D value of which is reduced by antiferromagnetic spin alignment between two radical spins through the excited triplet spin coupler. The general theoretical predictions of the spin alignment and the reduction of the fine-structure splitting of the triplet bis(radical) systems are presented. The fine-structure splitting of the unique photoexcited triplet state of 1, as well as the existence of the low-lying quintet state, is interpreted well on the basis of theoretical predictions. Details of the spin alignment in the photoexcited states are discussed.

The structure elucidation of emestrin ( l ) , a macrocyclic epidithiodioxopiperazine derivative isolated from the mycelial acetone extract of Ernericella striata, is reported, based on its 'H and '3C n.m.r. spectra and an X-ray crystallographic study of its methanol solvate; its absolute configuration was established by its c.d. spectrum.

Three new compounds designated as cycloaspeptides A (1), B (2), and C (3) were isolated along with ergosterol from the mycelial chloroform extract of Aspergillus sp. NE-45. The structures of cycloaspeptides A. B, and C were established on the basis of chemical and spectroscopic evidence as 1, 2, and 3, respectively. Cycloaspeptides are new cyclic pentapeptides containing an anthranilic acid residue and two N-methyl amino acid residues. Keywords•\Aspergillus; cyclic peptide; cycloaspeptide A; cycloaspeptide B; cycloaspeptide C; anthranylic acid; N-methyl amino acid; amino acid analysis Aspergillus sp. NE-45 is a fungus isolated from soil of the forest between Chumro and Kuldi Ghar, Gandaki, Western Development Region in Nepal, collected by S. Udagawa in 1980.2) Three new compounds, which were designated cycloaspeptides A (1), B (2), and C (3), along with ergosterol, were isolated from the mycelial chloroform extract of this fungus. The structural elucidation of the above compounds (1-3) is reported in this paper. Cycloaspeptide A (1), mp 270-272•Ž, [ƒ¿]D -228•‹, gave a molecular ion at m/z 641 on field desorption (FD) and electron impact ionization (EI) mass spectrometry, and elemental