Natsuki Kato

Typhasterol (2-deoxycastasterone): a new plant growth regulator from cat-tail pollen

Abstract Typhasterol, a new plant growth promoting substance from Typha latifolia L. was determined to be (22 R ,23 R ,24 S )-3a,22,23-trihydroxy-24-methyl-5α-cholestan-6-one.

Syntheses of 3-substituted furans via lithium di(3-furyl)cuprate—the application of lithium di(3-furyl)cuprate to the total synthesis of dendrolasin

Abstract One step syntheses of 3-substituted furans by the reactions of a new reagent, lithium di(3-furyl)cuprate 1 , with various substrates and the application of 1 to a total synthesis of dendrolasin are described.

Introduction of furan ring by a novel reagent, lithium di(3-furyl)cuprate·2furyllithium, into less reactive oxiranes

Abstract A new reagent, lithium di(3-furyl)cuprate·2furyllithium, which is distinct from lithium di(3-furyl)cuprate, possesses an excellent nucleophilicity and gives 3-substituted furans in good yields by the reactions with less reactive oxiranes.

The effect of metal complex of thyrotropin-releasing hormone on locomotor activity of neonatal chicken

Neonatal chickens were injected intraventricularly with Ni(II), Pd(II), Cu(II) or Zn(II) complex of TRH and the potencies of stimulating locomotor activity were compared with that of TRH, Ni(II)-TRH was more potent than the ligand while Pd(II)-TRH was inert. Cu(II)- and Zn(II)-TRH induced the response to the same extent of the ligand. These results indicate that the action of TRH in the CNS resulting in the locomotor hyperactivity is dependent on the tertiary conformation of molecule which is modified by chelate formation.

Stereocontrolled synthesis of clerodin homolog A synthetic approach to structure-activity relationships

Abstract In order to elucidate the structure-activity relationships of the antifeeding diterpenes having a neo -clerodane skeleton, clerodin homolog 5 was stereoselectively synthesized through 18 steps via a key intermediate 11 . Perhydrofuro[2,3-b]furan ring in the synthesized homolog was more unstable than that of the natural product, and gave a tri -MeOH adduct 3 in a similar behavior to that of the model compounds 1 and 2 .

Structure of the diterpene clerodendrin A

Clerodendrin A (I), a bitter principle of Clerodendron tricotomum Thunb. and an antifeeding repellent, is a diterpene with the clerodon skeleton as in clerodin (II). On oxidation with sodium periodate the dihydro-tetraol (XXVI) gave the acetal (XXVII). The formation of the acetal revealed the relative configuration of the epoxide ring and the 18-hydroxy-group. The c.d. and o.r.d. curves of the αβ-unsaturated ketone (XXXII), obtained by treatment of (XXVII) with manganese dioxide, showed a positive Cotton sign. Therefore, compound (I) has the configuration antipodal to that of clerodin. This was confirmed by X-ray analysis of the p-bromobenzoate of the chlorohydrin (XXII).

Timing measurements of lutetium based scintillators combined with silicon photomultipliers for TOF-PET system

As time-of-flight PET (TOF-PET) gains popularity in clinical diagnostic, the coincidence timing resolution of PET systems becomes more crucial. The most common scintillators for commercial TOF-PET systems are Lu-based ones such as LSO or LYSO for their high light output, high density and fast decay time. Recently, LGSO with 0.025% Ce (LGSO-fast) was developed which has faster decay time than LGSO with Ce concentration of 0.1 mol% (LGSO-standard). Using the LGSO-fast in conjunction with silicon photomultiplier (Si-PM) may improve the timing performance for the development of TOF-PET systems. Consequently, we tested the basic performance of LGSO-fast and coupled them with Si-PMs to measure the coincidence timing resolution using a high bandwidth digital oscilloscope. The performance was also evaluated for LGSO-standard and other Lu-based scintillators such as lutetium fine silicate (LFS) and two types of LYSOs from other manufacturers. The light output was largest for one of the LYSO from one manufacture and smallest for the LYSO from other manufacture. Decay time was fastest for LGSO-fast (33.8 ns) and slowest for one of the LYSO (39.9 ns). Coincidence timing resolution for 2.9 mm long Lu-based scintillators, LGSO-fast was the best (156.5 ps) and one of the LYSO showed the worst (235.1 ps). For the 20 mm long scintillators, coincidence timing resolution was also best for LGSO-fast (273.2 ps) and worst for one of the LYSO (481.8 ps). We conclude that LGSO-fast combined with Si-PM showed best timing performance among measured Lu-based scintillators. Also within the same Lu-based scintillators such as LYSOs, we found that the performance differences were sometimes significant and quality control of the Lu-based scintillator is essential to achieve good performance in PET systems.

Syntheses and conformational analyses of the perhydrofuro[2,3-b]furan compounds by using lanthanide shift reagent and empirical force-field calculation

Abstract 1-t-Butyl-7-hydroxyperhydrofuro[2,3-b]furan was synthesized via a furan-alcohol which was derived by a coupling reaction with an epoxide and a new reagent, Li di(3-furyl)cuprate. The configuration of the t-butyl substituent and the conformation of the furo[2,3-b]furan ring were decided by the combination of the LIS experiment and the empirical force-field calculation.

Estimation of nitrate metabolism in intestinal tract by measuring breath nitrous oxide concentration in Chinese and Japanese.

We have previously reported that ingestion of vegetables containing high nitrate (NO3−) increases breath nitrous oxide (N2O) concentration, probably due to denitrification. In the present study, we estimated NO3− metabolism in the intestine by determining exhaled breath N2O concentration after the ingestion of vegetables by 16 healthy Chinese and Japanese. Breath samples were collected at 15-min intervals for 4 hr after subjects ingested 180 g of vegetable juice or 50 g of lettuce. Breath N2O concentration was measured by an IR-PAS analyzer. Lettuce but not vegetable juice increased N2O concentrations similarly in Japanese and Chinese. In control subjects who ingested nothing, there were significant differences between Chinese and Japanese in peak N2O concentrations (334 ± 91 vs 140 ± 24 ppb, P = 0.027) and total excretions (535 ± 143 vs 214 ± 36 μg, P = 0.036). Although the reason for this difference is unclear, Chinese subjects could produce breath N2O from other metabolic pathways than denitrification of dietary NO3−.

Absolute stereochemistries and conformations of clerodin and caryoptin. Why conflicting results in absolute stereochemistry based on CD and ORD spectra

Abstract The reverse of absolute stereochemistries of clerodin and caryoptin means that the correct chirality conflict with the absolute stereochemistries based on Cotton effects. Molecular mechanics and X-ray studies confirmed that the B ring of the 6-keto derivatives retained the boat form as the stable conformer. Furthermore, the steric factors causing the conformational changes were proved by derivation to the strain-free derivatives. The conformation of the B ring in the derivatives changed to the chair form which is confirmed by the X-ray and CD.