Recent progress of our studies on catalytic asymmetric synthesis is reviewed focused on transition metal-catalyzed intramolecular asymmetric reactions using chiral organo-sulfur groups as main chiral auxiliaries such as asymmetric vinylcyclopropane-cyclopentene rearrangements and intramolecular asymmetric metallo-ene reactions, Lewis acid-catalyzed intramolecular asymmetric ene reactions with chiral sulfinyl groups, and palladium-catalyzed intramolecular asymmetric allylations via chiral enamines.
Interleukin-5 (IL-5) regulates the production and function of B cells, eosinophils and basophils. In particular, IL-5 plays a critical role in the development of CD5-positive B (B-1) cells. The pleiotropic activity of IL-5 on target cells is directly dependent on the initial binding to IL-5 specific cell-surface receptor (IL-5R). The IL-5 signals are mediated through the high affinity IL-5R which is composed of two different polypeptide chains, α and β. The α chain is a membrane-penetrated glycoprotein that specifically binds IL-5 and retains features common to the cytokine receptor superfamily. The β chain by itself does not bind IL-5, but it can convert the low affinity IL-5R into the high affinity IL-5R and in indispensable for IL-5 signal transduction. The β chain is shared among receptors for IL-5, IL-3 and GM-CSF and is called βc. The cytoplasmic comains of both IL-5Rα and βc are essential for signal transduction. The membrane proximal proline-rich sequence of the cytoplasmic domain of IL-5Rα was found to be essential for the IL-5-induced proliferative response, expression of nuclear proto-oncogenes such as c-jun, c-fos and c-myc, and activation of Bruton's tyrosine and JAK2 kinases. Furthermore, JAK2 activation correlates with proline residues in Pro-Pro-X-Pro motif in the cytoplasmic domain of IL-5Rα. These results indicate that activation of JAK2 and its substrate is critical to coupling IL-5-induced tyrosine phosphorylation and ultimately mitogenesis. I will discuss about molecular mechanisms of IL-5 signaling and B cell defect in X-linked immunodeficient mice in relation to IL-5 signaling.
We designed and synthesized a new sensitive and highly reactive fluorogenic reagent (1a, DMEQ-TAD) targeting a conjugated diene. DMEQ-TAD reacted quantitatively with major vitamin D metabolites and synthetic analogs under a variety of conditions to yield the corresponding 6, 19-cycloadducts as a mixture of the C (6) epimers. The stereochemistry of the adducts was determined by their CD spectra on the basis of the exciton chirality method. The fluorescent products can be quantified linearly down to 10 fmol by HPLC. The new fluorometric method was successfully used in the assays of 25-OHD3, 24, 25-(OH)2D3 and 25, 26-(OH)2D3 in the human plasma. The method was proved to be reliable and precise compared with the HPLC-UV assay method. Reactions of DMEQ-TAD with retinoic acid (21a) and its geometrical isomers (21b-d) having a conjugated pentaene system afforded 7, 10-adducts (24a-d) as major products together with 5, 8-adducts (26a-d) in about 9 : 1 ratio (70-95% yield) except for the 9Z-isomer (21e) which gave only a 5, 8, 11, 14-bis-adduct (27). DMEQ-TAD reacted with microcystins LR, YR and RR, at the conjugated diene part to yield 4, 7-cycloadducts as a pair of epimers in good yield.
A series of 4, 5-diphenylthiazoles containing morpholinoalkyl amino groups at the 2 position was synthesized and their anti-platelet activities were evaluated. The inhibitory effects of the compounds in which phenyl groups at the 4 position were substituted by methoxy groups were more potent than those of aspirin and ibuprofen on the collagen-induced rabbit platelet aggregation. These compounds were also shown to have potent efficacies on the arachidonic acid-induced platelet aggregation. On the other hand, these compounds did not affect the ADP-induced platelet aggregation similarly to non-steroidal anti-inflammatory agents. Moreover, their efficacies on the inhibition of prostaglandin synthesis were more potent than that of ibuprofen. Therefore, we thought that 2-(morpholinoalkyl)amino-4, 5-diphenylthiazoles, in spite of their basic properties, inhibited the platelet aggregation based on cyclooxygenase.
It is thought that highly reactive oxygen radicals generated at the ischemia-reperfusion in case of strokes play an important role in damaging the brain. It is well known that lipid peroxidation is propagated by active oxygen radicals, and the the brain is susceptible to the lipid peroxidation. In the previous study, we found that several Chinese herbal medicines and kampo components, which were used for the attenuation of the post-ischemic brain injury, showed a free-radical (OH·, O2&minusd; and DPPH) scavenging activity. However, it is not clear whether these Chinese herbal medicines can inhibit the lipid peroxidation reaction or not. In attempting to address this question, we have used three kinds of kampo formulations (Oren-gedoku-to (Huang-Lian-Jie-Du-Tang), Saiko-ka-ryukotsu-borei-to (Chai-Hu-Jia-Long-Gu-Mu-Li-Tang) and Keishi-bukuryo-gan (Gui-Zhi-Fu-Ling-Wan)) to measure the suppressive effect of the lipid peroxidation on the mouse cerebrum using the TBA technique in vitro and in vivo. In vitro experiments, all these Chinese herbal medicines decreased the levels of TBA-reactive substances concentration-dependently. In vivo studies, the levels of the TBA-reactive substance of the cerebrum homogenate of mice treated with these kampo formulations by p.o. for three weeks also decreased. From these results, we suggest that the pharmacological action of Chinese herbal medicines used for the attenuation of the post-ischemic brain damage not only have a free-radical scavenging activity, but also have a suppressive effect on the generation of the lipid peroxidation.
Skin permeation and its enhancing activity of Coptidis Rhizoma (Coptis japonica MAKINO) were studied in regard to its application as a bath agent. As a result, methanol extracts and three alkaloids (berberine, coptisine, and palmatine isolated from Coptidis Rhizoma) enhanced effectively the skin permeation of 5-fluorouracil, which is taken as a hydrophilic permeant. Furthermore, it was observed that diffusion coefficient is almost constant on the skin permeation of 5-fluorouracil and was also observed that these three kinds of alkaloids did not penetrate through the skin, but adsorbed into the skin. These results suggest that these three protoberberine type alkaloids increase the concentration of polar drugs in the skin and enhance the skin permeation similarly to surfactants.
Inhibitory effects of hydroquinone-α-glucoside (HQ-α-G) on the melanogenesis were investigated and compared with those of arbutin. The levels of inhibitory effects of HQ-α-G and arbutin on the tyrosinase activity were nearly the same. Inhibitory effects of both compounds on the melanogenesis, were studied using cultured B16 melanoma cells, and HQ-α-G was also found to have a similar effect to that of arbutin without inhibiting cell growth. In this experiment, while HQ-α-G hardly inhibited cell growth at 1 mM, arbutin inhibit it significantly at the same concentration. From these results it is suggested that HQ-α-G as well as arbutin inhibited the melanogenesis by affecting tyrosinase rather than by killing melanocytes. Furthermore, the melanogenesis of guineapigs with brown hair was reduced to about 80% by applying them each compound. The great differences in toxicity to normal human keratinocyte were not recognized between these two glucosides. It is, therefore, considered that HQ-α-G is an effective and safe ingredient for cosmetics.
We have established a simple method for the chiral stationary-phase liquid chromatographic resolution of racemic chlorpheniramine (Chp) and its two N-demethylated metabolites, monodesmethylchlorpheniramine (DMChp) and didesmethylchlorpheniramine (DDMChp), using an ovomucoid-conjugated column with respective quantitation limits of 5 ng/ml. The assay was used to study the age and sex difference in stereoselective N-demethylation of Chp by rat liver microsomes. The formation rate of each DMChp from racemic Chp was about 2.2 times faster with the S-(+)-enantiomer than the R-(-)-enantiomer in male rats at the age of only 8 weeks, whereas the rate of N-demethylation in male rats was not different between S-(+)- and R-(-)-enantiomers at the age of 3 and 24 weeks. The Vmax/Km value for the formation of S-(+)-DMChp increased with age in male rats, but the value in 8-week-old rats was lower than that in 3-week-old rats in the formation of R-(-)-DMChp. In female rats, on the other hand, the formation rate of DMChp from recemic Chp did not differ between S-(+)- and R-(-)-enantiomers at each age, suggesting a lack of stereoselectivity in the microsomal N-demethylation. Moreover, the Km and Vmax values for N-demethylation of Chp enantiomers were nearly identical between two consecutive ages in female rats. Further metabolism of DMChp to DDMChp was not observed between both enantiomers in male and female liver microsomes at the age of 3, 8 and 24 weeks.
The structures of by-products, observed as weak side peaks on the chromatogram by gas chromatographic analysis, were estimated by gas chromatography (GC)-mass spectrometry (MS) to be 4-(1-methylamino-pent-3'-yl)-1-methylpiperidine (III) arising from paraquat (I) and 1-butyl-2-aza-perhydroquinolidine (IV) arising from diquat (II). These by-products were resulted from the reductive cleavage at C-N bond in pyridine ring of I or II belonged to N-alkylbipyridinium derivatives. In order to confirm the estimated structures of the by-products described above, a preparative scale reduction was carried out on I and II, and we succeeded in the isolation and purification of III and IV by thin-layer chromatography. The structures of both III and IV were supported on the basis of 1H- and 13C-nuclear magnetic resonance spectra. In addition, for the purpose of discussing the regularity in this reductive cleavage reaction, the related compounds such as 1, 4-dimethylpyridinium iodide (V), 1-methyl-4-phenylpyridinium iodide (VI) and 1-dodecylpyridinium chloride (VII) replaced one in two pyridine rings by -CH3, -C6H5 and -H, and 1, 1'-diethyl-4, 4'-bipyridinium dichloride (VIII), i.e. a diethyl derivative of I, were reduced with NaBH4 (or NaBD4)-NiCl2. We elucidated by GC-MS analysis that the reductive cleavage reaction at C-N bond in V, VII and VIII except for VI occurred as side reaction. In the previous paper, we reported that a correlation between the yield of the by-product of I and amounts of reductants NaBH4 and NiCl2 in water was observed, and the yield of the by-product increased in the two-step (NaBH4 and NiCl2-NaBH4) reduction method rather than in the one-step (NiCl2-NaBH4) method.