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1.
The convenient method for the synthesis of 1,3-oxathiolan-2-ones by the reaction of epoxides with elemental sulfur and carbon monoxide in the presence of catalytic amount of sodium hydride has been developed. 相似文献
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Maly J Di Meo C De Francesco M Masci A Masojidek J Sugiura M Volpe A Pilloton R 《Bioelectrochemistry (Amsterdam, Netherlands)》2004,63(1-2):271-275
Electrochemical synthesis of nickel-nitrilotriacetic acid (Ni-NTA) chelators, for subsequent immobilization of (His)(6)-tagged proteins (Photosystem II (PSII) as model molecule), on Au or Au-graphite electrodes is compared to chemical synthesis. Results show: (i) higher Ni-NTA surface density, (ii) shorter treatment time (1-12 min vs. 16 h normally needed for self-assembled monolayer (SAM)), (iii) possibility of addressing the chelator to only one Au electrode, in a sensor micro-array. 相似文献
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Several transition metal salts were found to catalyze aza-Michael reactions of enones with carbamates efficiently. The catalytic activity was strongly dependent on the nature of the metal salts. While conventional Lewis acids such as BF(3).OEt(2), AlCl(3), or TiCl(4) showed lower activity, group 7-11 transition metal salts in higher oxidation states such as ReCl(5), Fe(ClO(4))(3).9H(2)O, RuCl(3).nH(2)O, OsCl(3).3H(2)O, RhCl(3).nH(2)O, PtCl(4).5H(2)O, or AuCl(3).H(2)O exhibited higher catalytic activity. [reaction: see text] 相似文献
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Ono K Yoshida A Saito N Fujishima T Honzawa S Suhara Y Kishimoto S Sugiura T Waku K Takayama H Kittaka A 《The Journal of organic chemistry》2003,68(19):7407-7415
Six novel 2-substituted analogues of 1alpha,25-dihydroxy-19-norvitamin D(3), 6a,b-8a,b, were efficiently synthesized utilizing (-)-quinic acid as the A-ring precursor. The C2-modified A-rings were prepared as 4-alkylated (3R,5R)-3,5-dihydroxycyclohexanones 12-15 from (-)-quinic acid based on radical allylation at the C4 position of methyl (-)-quinicate. The new type of the CD-ring coupling partner 23 was synthesized from 25-hydroxy Grundmann's ketone 19 to apply to the modified Julia olefination to construct a diene unit between the A-ring and the CD-ring. The coupling yields, including a deprotection step, were 47-62%. After the separation of the diastereomers based on C2 stereochemistry, the structure (2alpha or 2beta) was determined by (1)H NMR experiments and compared to DeLuca's 2-methyl- and 2-ethyl-1alpha,25-dihydroxy-19-norvitamin D(3). Thus, the synthesized 2alpha-(3-hydroxypropyl)-1alpha,25-dihydroxy-19-norvitamin D(3) (8a) showed almost the same potency in binding to the bovine thymus vitamin D receptor (VDR) as the natural hormone 1, while its beta-isomer 8b had only a 3% affinity. Both 2alpha-allyl- and 2alpha-propyl-1alpha,25-dihydroxy-19-norvitamin D(3) (6a and 7a) and their 2beta-analogues (6b and 7b) possessed a weak affinity for the VDR. The strong VDR ligand 8a was ca. 36-fold more potent in induction of HL-60 cell differentiation than 1, and interestingly, even the weaker ligand 8b showed a 6.7-fold higher potency in the cell differentiation activity than that of 1. 相似文献
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Peptide-mediated protein delivery into living cells has been attracting our attention. Among the peptides that have been reported to have carrier activity, the one from the human immunodeficient virus (HIV)-1 Tat has been most often used for the introduction of exogenous macromolecules into cells. We have shown that not only the Tat peptide, but also various arginine-rich peptides showed very similar characteristics in translocation, and the possible presence of ubiquitous internalization mechanisms among the arginine-rich peptides has also been suggested. These arginine-rich peptides includes ones derived from HIV-1 Rev and flock house virus coat proteins. The linear- and branched-chain peptides containing approximately 8 residues of arginine also show a similar ability. In this review, we present the structural variety of membrane permeable peptides and provide a survey of the findings on the translocation of these peptides through the cell membranes. 相似文献
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