A new route to 2'-O-alkyl-2-thiouridine derivatives via 4-O-protection of the uracil base and hybridization properties of oligonucleotides incorporating these modified nucleoside derivatives

Oligonucleotides containing 2-thiouridine (s2U) in place of uridine form stable RNA duplexes with complementary RNAs. Particularly, this modified nucleoside has proved to recognize highly selectively adenosine, the genuine partner, without formation of a mismatched base pair with the guanosine counterpart. In this paper, we describe new methods for the synthesis of 2-thiouridine and various 2'-O-alkyl-2-thiouridine derivatives. Oligoribonucleotides having these modified nucleoside derivatives were synthesized, and their hybridization and structural properties were studied in detail by the 1H NMR analysis of these modified nucleosides and Tm experiments of RNA duplexes with their complementary RNA strands.     

A new synthesis of pyrroles by the condensation of cyclopropenes and nitriles mediated by gallium(III) and indium(III) salts

Gallium(III) and indium(III) halides were found to mediate the condensation of cyclopropenes and nitriles to give pyrrole derivatives in moderate yields. When excess nitrile was present, diazepine was also formed.     

Emission of 2-phenylethanol from its β-d-glucopyranoside and the biogenesis of these compounds from [H8] l-phenylalanine in rose flowers

The hydrolysis of 2-phenylethyl β-d-glucopyranoside (3) was found to be partially inhibited by feeding with 2-phenyl-N-glucosyl-acetamidiumbromide (8), a β-glucosidase inhibitor, resulting in a decrease in the diurnal emission of 2-phenylethanol (2) from Rosa damascena Mill. flowers. Detection of [1,1,2,2′,3′,4′,5′,6′-²H₈]-2 and [1,2,2′,3′,4′,5′,6′-²H₇]-2 from R. ‘Hoh-Jun’ flowers fed with [1,1,2,2′,3′,4′,5′,6′-²H₈]-3 suggested that β-glucosidase, alcohol dehydrogenase, and reductase might be involved in scent emission. Comprehensive GC-SIM analyses revealed that [1,2,2,2′,3′,4′,5′,6′-²H₈]-2 and [1,2,2,2′,3′,4′,5′,6′-²H₈]-3 must be biosynthesized from [1,2,2,2′,3′,4′,5′6′-²H₈] l-phenylalanine ([²H₈]-1) with a retention of the deuterium atom at α-position of [²H₈]-1.     

Synthetic studies on 3-arylquinazolin-4-ones: intramolecular nucleophilic aromatic substitution reaction of 2-carboxamido-3-arylquinazolin-4-ones and its application to the synthesis of secondary aryl amines

The general synthesis and a novel intramolecular nucleophilic aromatic substitution (S_NAr) reaction of 2-carboxamido-3-arylquinazolin-4-ones, a potentially useful scaffold in the field of medicinal chemistry, are described. The synthetic utility of the S_NAr reaction as a tool for the synthesis of secondary aryl amines, including diaryl amines, is also demonstrated.     

Microbiological synthesis of 16-ketopregnanes from steroidal sapogenins

Incubation of diosgenone (1, 25D-spirost-4-en-3-one) with Verticillium theobromae (Turconi) Mason et Hughes (CBS) afforded 20α-hydroxypregn-4<ne-3,16-dione (3) and 3α,11β,20α-trihydroxy-5α-pregnan-16-one (4). The same transformation products were also obtained by the use of Stachylidium bicolor Link (IFO 6647). Isolation and identification processes of the products are discussed.     

Simultaneous operation of plural separation modes in capillary electrophoresis with a chemiluminescence detector possessing a micro-space area for reaction/detection

Analysis of alpha-amino acids, proteins, and phenolic compounds was simultaneously performed using three capillaries in capillary electrophoresis with chemiluminescence detection, taking advantage of the micro-space area for reaction/detection at the tip of the capillary. The three capillaries included usual, polymer-containing, and sodium docley sulfate (SDS)-containing migration buffers for separation. The eluted samples from the capillaries, which were inserted into the chemiluminescence detection cell, were mixed with chemiluminescence reagent at the tips of the capillaries to generate visible light. The specific micro-space area for reaction/detection at the tips of the capillaries enabled the simultaneous operation of the three separation modes in the present system.     

(2,7-Disubstituted-1,8-biphenylenedioxy)bis(dimethylaluminum) as bidentate organoaluminum Lewis acids: elucidation and synthetic Utility of the double electrophilic activation phenomenon

A series of (2,7-disubstituted-1,8-biphenylenedioxy)bis(dimethylaluminum) (2) has been readily prepared in situ by treatment of the requisite 2,7-disubstituted-1,8-biphenylenediol (1) with Me3Al (2 equiv) in CH2Cl2 at room temperature; this primarily relies on the successful establishment of a new synthetic procedure of 1 starting from inexpensive m-anisidine. Evaluation of 2 as a bidentate organoaluminum Lewis acid has been performed by the reduction of ketonic substrates using Bu3SnH as a hydride source in comparison to the conventional monodentate Lewis acid dimethylaluminum 2,6-xylenoxide (11), uncovering the significantly high activation ability of 2 toward carbonyl. Particularly, (2,7-dimethyl-1,8-biphenylenedioxy)bis(dimethylaluminum) (2a) exerted the highest reactivity, which has also been emphasized in the Mukaiyama aldol reaction. The structure of the bidentate Lewis acid 2 was unambiguously determined by single-crystal X-ray diffraction analysis of 2g possessing a bulky 3,5-di-tert-butylphenyl substituent, revealing the rigid dimeric assembly in the solid state. The double electrophilic activation of carbonyl substrate by 2a has been supported by low-temperature 13C NMR analysis as well as theoretical study using the Gaussian 98 program. Moreover, unique stereoselectivity has been observed in the 2a-promoted Mukaiyama Michael addition, and highly chemoselective functionalization of carbonyl compounds in the presence of their acetal counterparts has been realized using 2a. Finally, the effectiveness of 2a for the activation of ether functionality has been demonstrated in the Claisen rearrangement of allyl vinyl ethers.     

One-dimensional ion transport in self-organized columnar ionic liquids

New fan-shaped ionic liquids forming columnar liquid crystalline phases have been prepared to obtain one-dimensional ion-transporting materials. The ionic liquids consist of two incompatible parts: an imidazolium-based ionic part as an ion-conducting part and tris(alkyloxy)phenyl parts as insulating parts. Two compounds having octyl and dodecyl chains have been synthesized. Self-assembly of these materials leads to the formation of thermotropic hexagonal columnar liquid crystalline states at room temperature. Anisotropic one-dimensional ionic conductivities have been successfully measured by the cells having comb-shaped gold electrodes. The self-organized columns have been aligned macroscopically in two directions by shearing perpendicular and parallel to the electrodes. The ionic conductivities parallel to the column axis are higher than those perpendicular to the axis. The incorporation of lithium salts in these columnar materials leads to the enhancement of the ionic conductivities and their anisotropy. These materials would be useful for anisotropic transportation of ions at the nanometer level.