Solid-phase microextraction for the evaluation of partition coefficients of a chlorinated dioxin and hexachlorobenzene into humic substances.

We developed a method for the evaluation of the partition coefficients (K(oc)) of hexachlorobenzene (HCB) and 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (HpCDD) into humic substances (HSs) by using solid-phase microextraction (SPME). In the aqueous solution containing HCB or HpCDD and HS, the unbound species of HCB or HpCDD were accumulated on the SPME fiber. Subsequently, HCB or HpCDD on the SPME fiber was directly analyzed by GC-ECD. When the concentration of organic carbon in HS ([OC]) was plotted against the ratio of [HCB] or [HpCDD] in the absence of HS to that in the presence of HS, linear relationships were observed. The slope of the line corresponded to the K(oc) value. The log K(oc) values for HCB and HpCDD evaluated were in the ranges of 3.9 - 4.9 and 5.9 - 7.2, respectively. These values were the same order as those in the literature, which were evaluated by other methods (e.g., solubility enhancement, solid-phase extraction and dialysis). The relative standard deviations of the log K(oc) values evaluated in this study were within 5%.     

Selective Cadmium Fluorescence Probe Based on Bis-heterocyclic Molecule and its Imaging in Cells

Journal of Fluorescence - Fluorescence probes that selectively image cadmium are useful for detecting and tracking the amount of Cd2+ in cells and tissues. In this study, we designed and...     

Synthesis of 5-(3-indolyl)oxazole natural products. Structure revision of Almazole D

The synthesis and utility of β-oxotryptamine and β-oxytryptophan ester synthons provide a convenient entry to 5-(3-indolyl)oxazole natural products leading to a structure revision of almazole D.     

Stereochemistry of the asymmetric carbopalladation of allenes followed by nucleophilic substitution reactions with carbo- and aminonucleophiles

The stereochemistry of the asymmetric palladium-catalyzed reaction of allenes with iodobenzene followed by nucleophilic substitution reaction with sodium malonate and N-methylbenzylamine is described. On the basis of the absolute configuration of the product and the stereochemical result of a similar reaction of a chiral allene, the mechanism of the above asymmetric reactions is discussed.     

Investigation of an Olfactoryly Active Ring-Like Conformer of a Chain-Type Odorant, (3S)-3,7-dimethyloctanal,by computer calculation and graphics

The odor of (3S)-3,7-dimethyloctanal, a chain-type odorant, has some resemblance to that of ethyl (1 R, 6S)-2,2,6-trimethylcyclohexane-1-carboxylate, a ring-type odorant. We investigated the ring-like conformers of (3S)-3,7-dimethyloctanal. Two approaches, (i) systematic conformational analysis and (ii) construction of the initial structure by referring to the structure of the ring-type odorant, were considered in the search for ring-like conformers of the chain-type odorant. As a result, it was found that two stable ring-like conformers of (3S)-3,7-dimethyloctanal, obtained from the two approaches, resembled conformers of ethyl (1R, 6S)-2,2,6-trimethylcyclohexane-1-carboxylate in their three-dimensional structural features. The shapes of the two ring-like ones were not exactly the same but were quite similar. Therefore, the two ring-like conformers were considered to approximate the olfactoryly active conformer that binds and stimulates the same odor receptor as that for ethyl (1R,6S)-2,2,6-trimethylcyclohexane-1-carboxylate. In addition, ring-like conformers of another chain-type odorant, 2-methylpent-2-enal, were investigated to check the validity of the calculation method used.