Stereoselective synthesis of cis and trans-fused 3a-aryloctahydroindoles using cyclization of N-vinylic α-(methylthio)acetamides: synthesis of (−)-mesembrane

Treatment of N-(2-arylcyclohex-1-en-1-yl)-α-(methylthio)acetamides with N-chlorosuccinimide (NCS) gave 3a-aryl-2,3,3a,4,5,6-hexahydro-3-(methylthio)indol-2-ones. Desulfurization of the cyclization products followed by a catalytic hydrogenation of the resulting hexahydroindol-2-ones gave predominantly or exclusively trans-fused octahydroindol-2-ones. On the other hand, reduction of the desulfurization products with Et₃SiH in CF₃CO₂H exclusively provided cis-fused octahydroindol-2-ones. A chiral induction of N-[2-(3,4-dimethoxy)phenylcyclohex-1-en-1-yl]-α-(methylthio)acetamide having an (R)-1-(1-naphthyl)ethyl group on the nitrogen atom led to the synthesis of (−)-mesembrane and (−)-trans-mesembrane.     

Synthesis and evaluation of alpha-fucosidase inhibitory activity of 5a-carba-alpha-L-fucopyranose and alpha-DL-fucopyranosylamine

5a-Carba-alpha-L-fucopyranose and -alpha-DL-fucopyranosylamine were synthesized in conventional manner starting from 2,3,4-tri-O-acetyl-6-bromo-6-deoxy-5a-carba-beta-D- and -DL-glucopyranosyl bromides, respectively, and assayed for inhibitory activity against alpha-fucosidase (bovine kidney). Although the former proved to be only a moderate inhibitor (Ki = 4.3 x 10(-5) M), the latter could be shown to possess strong inhibitory potential (Ki = 2.3 x 10(-7) M). Diastereoisomeric imino-linked 5a'-carbadisaccharides were synthesized by coupling of the racemic 5a-carba-alpha-fucopyranosylamine and 1,6:3,4-dianhydro-2-azido-2-deoxy-beta-D-galactopyranose, in order to estimate approximately the inhibitory activity of individual optical antipodes of 5a-carba-alpha-fucopyranosylamine.     

Ab initio molecular orbital study of the reactivity of active alkyl groups. VI. Modified reaction model for the elimination process of nitrosation reaction

The mechanisms of nitrosation of acetone through sodium enolate [CH3COCH2]- Na+ (1) or naked enolate [CH3COCH2]- (2) with tert-butyl nitrite (CH3)3CONO (3) were studied using ab initio molecular orbital (MO) methods. When the modified complex model was used in the elimination process, our results demonstrated the predominant formation of E-1-hydroxy-imino-2-oxo-propane CH3COCH=NOH (4E), in which a counter-cation of the base catalyst did not participate during the reaction. On the other hand, participation of the counter-cation during the reaction contributed to the formation of the Z-isomer of 4 (4Z).     

Stereoselective synthesis of Nuphar quinolizidine alkaloid, (−)-deoxynupharidine

A stereoselective synthetic route to Nuphar quinolizidine alkaloid, (−)-deoxynupharidine, was established by employing reductive carbon-nitrogen bond cleavage, followed by simultaneous recyclization of a proline derivative with samarium diiodide, and an intramolecular ring-closing metathesis, as the key steps.     

Orosomucoid 1 and orosomucoid 2 types in the Taiwanese and Japanese: evidence for five new orosomucoid variants

The genetic polymorphisms of orosomucoid, ORM1 and ORM2, were analyzed by isoelectric focusing on polyacrylamide gels and subsequent immunoprinting. Sera from 600 unrelated individuals in Taiwan and Japan were examined. Five new alleles, designated ORM1*7, ORM1*8, ORM1*4.2, ORM2*8 and ORM2*10, were observed together with common and rare alleles that have been found in the Japanese and the Filipinos. As compared with the Japanese, the Taiwanese have a higher frequency of ORM1*1, and a significantly lower frequency of ORM1*2.1.     

Cellulose conformation responsible for resolution of DL-amino acids

Summary For the purpose of biochemical study, the resolution of non-derivatized DL-amino acids was carried out by using native-cellulose thin-layer and column chromatography. Its resolution capability was known to be in proportion to the increase of environmental hydrophobicity. It is suggested that the resolutions of DL-amino acids might be resulted from the cellulose conformation change under hydrophobic conditions. The model structures of cellulose are proposed in order to understand the mechanism of chiral selection of amino acids on its molecular surface. LEB/OU contribution No. 70     

Intermolecular Friedel-Crafts reaction catalyzed by InCl3

Our recent discovery that In(III) salts were able to activate halides catalytically under mild conditions for the intermolecular Friedel-Crafts cyclization prompted us to explore this highly efficient activation in intermolecular Friedel-Crafts reactions. The alkylation of p-xylene with allylic and benzylic halides was demonstrated under catalytic and mild condition to afford in some cases quantitative yields of the monoalkylated products without the need to employ large excesses of reactants.     

Stereochemical Assignment of the Protein–Protein Interaction Inhibitor JBIR‐22 by Total Synthesis

Recent reports have highlighted the biological activity associated with a subfamily of the tetramic acid class of natural products. Despite the fact that members of this subfamily act as protein–protein interaction inhibitors that are of relevance to proteasome assembly, no synthetic work has been reported. This may be due to the fact that this subfamily contains an unnatural 4,4‐disubstitued glutamic acid, the synthesis of which provides a key challenge. A highly stereoselective route to a masked form of this unnatural amino acid now enabled the synthesis of two of the possible diastereomers of JBIR‐22 and allowed the assignment of its relative and absolute stereochemistry.     

One‐Step Versus Multistep Equilibrium of Carbazole‐Bridged Dinuclear Zinc(II) Complex Formation: Metal‐Assisted π‐Association and ‐Dissociation Processes

This work demonstrates a selection criteria that determines whether molecular assembly occurs through a one‐step or stepwise manner in ligand‐bridged dinuclear zinc(II) (Zn²⁺) complex formation, which is associated with the π stacking of building blocks. The building blocks of carbazole ligands ( L¹ and L⁴ ) that contain two imidazole moieties at the 3,6‐positions form 4:2 complexes (i.e., [ L ]₄?(Zn²⁺)₂) at a molar ratio of 0.50 ([Zn²⁺]/[ L ]₀=0.50), thereby providing π stacking between the carbazole ligands. At the molar ratio of 0.67 ([Zn²⁺]/[ L ]₀=0.67), the 4:2 complexes change to 3:2 complexes (i.e., [ L ]₃?(Zn²⁺)₂) with no π‐stacked carbazole unit. In contrast, when the imidazole groups in L¹ are replaced with benzoimidazole groups ( L³ ), L³ also yields the 4:2 complex [( L³ )₄?(Zn²⁺)₂] at a molar ratio of 0.50. However, there is no structural transition from ( L³ )₄?(Zn²⁺)₂ to other complex species above a molar ratio of 0.50. Similarly, when two imidazole groups are introduced into the carbazole ring at 2,7‐positions ( L⁵ ), L⁵ also gives the 4:2 complex [( L⁵ )₄?(Zn²⁺)₂] that shows no structural transition to other complex species at a higher molar ratio.     

Extractability of dioxins from soil: II. Effects of acid or alkaline pretreatment on the extractability of dioxin homologues from soil samples

The effects of sample pretreatment on the extractability of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (CoPCBs) from three suburban soil samples were evaluated. The samples were treated with 0.1?M HCl or 0.1?M NaOH and extracted by pressurized liquid extraction (PLE) with toluene. In addition, untreated soil samples were subjected to PLE with acetone. The extractability values were compared to values obtained by toluene extraction without pretreatment. Alkaline pretreatment increased the extractability of higher-chlorinated CDDs (HiCDDs), whereas acid pretreatment slightly decreased their extractability. No change in extractability was observed for higher-chlorinated CDFs under any conditions. The extractability of lower-chlorinated CDD/Fs (LoCDD/Fs) and CoPCBs was increased only by acetone extraction. PCDD/F homologue profiles in soil humic acid fractions and those in dead leaves, a major raw material of soil humus, were also determined. These results suggest that the variations in the extractability of dioxin homologues are due mainly to variations in their physical state in the soil, especially their interactions with soil humus.