Syntheses of (+/-)-methyl 6'alpha-demethyl-6'alpha-cyanoabscisate and (+/-)-methyl 6'alpha-demethyl-6'alpha-methoxycarbonylabscisate

New abscisic acid analogs possessing a cyano or methoxycarbonyl group at the 6'alpha-position of methyl abscisate were synthesized by regioselective hydrocyanation. These compounds had weak activity in the rice second leaf sheath elongation test.     

Stereo- and biochemical profiles of the 5-6- and 6-6-junction isomers of alpha-D-mannopyranosyl [60]fullerenes

The 5-6- and 6-6-junction isomers of alpha-D-mannopyranosyl [60]fullerene were studied by means of circular dichroism (CD), deuterium labeling, 1H-NMR, molecular-dynamics (MD) calculations, and a lectin-binding assay. The CD spectra of the O-acetylated derivatives allowed clear discrimination of the isomers, while the 1H-NMR spectra, with assistance from deuterium labeling and MD calculations, served to disclose the unique conformation and molecular geometry of each acetylated isomer in chloroform solution. The deprotected 5-6- and 6-6-isomers, which gave colloidal suspensions in aqueous mixtures, displayed marked activity in blocking lectin-induced hemagglutination by concanavalin A.     

Synthesis, cytostatic and anti-HCV activity of 6-(N-substituted aminomethyl)-, 6-(O-substituted hydroxymethyl)- and 6-(S-substituted sulfanylmethyl)purine nucleosides

An efficient and facile synthesis of a large series of diverse 6-(N-substituted aminomethyl)-, 6-(O-substituted hydroxymethyl)- and 6-(S-substituted sulfanylmethyl)purine nucleosides (55 examples of both ribo- and 2'-deoxyribonucleosides), aimed at identifying novel homologues of natural nucleosides, was developed. The key transformation involved nucleophilic substitutions of Tol-protected 6-(mesyloxymethyl)purine nucleosides by primary or secondary amines, alcoholates or thiolates. While the 2'-deoxyribonucleosides were inactive, the ribonucleosides exerted considerable cytostatic effects and some anti-HCV activity with low selectivity.     

Genetic properties of transposons Tn6-1, Tn6-2 and Tn19-1

The level and range transposition of the transposons Tn6-1, Tn6-2, Tn19-1, and their ability to influence plasmid transfer has been studied. The widest range of transposition was shown for transposon Tn6-2. Insertions of each of the studied transposons into different conjugative plasmids genomes resulted in change of frequencies of plasmids transfer and change of plasmids mobilization activity.     

Synthesis, cytostatic, and antiviral activity of novel 6-[2-(dialkylamino)ethyl]-, 6-(2-alkoxyethyl)-, 6-[2-(alkylsulfanyl)ethyl]-, and 6-[2-(dialkylamino)vinyl]purine nucleosides

An efficient and facile synthesis of a large series of diverse 6-[2-(dialkylamino)vinyl]-, 6-[2-(dialkylamino)ethyl]-, 6-(2-alkoxyethyl)-, and 6-[2-(alkylsulfanyl)ethyl]purine nucleosides (35 examples of both ribo- and 2'-deoxyribonucleosides) was developed. The key transformations involved conjugate nucleophilic additions of amines, alcoholates, or thiolates to Tol-protected 6-alkylylpurine or 6-vinylpurine nucleosides. 6-[(2-Dialkylamino)vinyl]- and some 6-[(2-dialkylamino)ethyl]purine ribonucleosides exerted significant cytostatic effects and some anti-HCV activity with low selectivity.     

Isomerisation and conformation studies of (+)- and (-)6-hydroxy-5, 6-dihydrouridine.

(1) "Uridine hydrates" i.e. (+)- and (-)6-hydroxy-5, 6-dihydrouridine were formed under gamma irradiation in a deaerated aqueous solution of uridine. (2) The structures of two diastereoisomers were determined by spectroscopic measurements (infrared, ultraviolet and NMR) and verified by stereospecific synthesis; uridine hydrates were prepared by mild reduction of trans(+)- and (-)iodohydrins with acetic acid and zinc power. (3) The carbon 6 epimerisation of uridine hydrates 6R or 6S was performed in triated water (pH 5.5, 30 degrees C) and at the same time tritium incorporation on carbon 5 was noted. The mechanism of these reactions could be explained by the opening of the N1-C6 bond of the pyrimidine ring, followed by ketoenolisation reaction of carbons 4 and 5. (4) The 250 MHz NMR analysis has allowed us to determine the nucleoside conformations. Nucleosides had mainly the S(C2' endo) conformation. A slight preference of gauche-gauche (gg) rotamer of the exocyclic hydroxymethyl group was noted and the aglycone was in the anti conformation.     

Theme 6- Plant Microbiome

In Vitro Cellular &; Developmental Biology - Plant -     

6-α-葡糖基-β-环糊精对辣根过氧化物酶性能的影响

辣根过氧化物酶 (ＨＲＰ ,ＥＣ1 .1 1 .1 .1 7)催化酚类及芳香胺类物质进行羟基化、氧化或聚合。这些反应在精细化学品、食品添加剂、功能性材料制备以及有机废水治理中具有重要的应用价值[1]。但是由于在某些条件下酶的稳定性及催化活性较低 ,限制了其在工业中的应用范围。酶的稳定性可以通过对酶分子所处微环境性质的调节而加以改善。实现这种作用的一种有效方法是利用一些特殊成分 ,如糖苷类、多元醇类 ,或有机溶剂与酶之间的修饰作用[2 ]。有关研究显示 ,这些成分能够起到调节酶分子的亲水性 /疏水性及空间构象 ,改善其催化性能及对环境…     

Synthesis of S6-(2,4-dinitrophenyl)-6-thioguanosine phosphoramidite and its incorporation into oligoribonucleotides

The preparation of N(2)-phenoxylacetyl-S(6)-(2,4-dinitrophenyl)-6-thioguanosine phosphoramidite and its subsequent incorporation into oligoribonucleotides is described. The identity of the oligonucleotides was confirmed by UV spectrophotometry and nucleoside composition analysis.     

Preparation of 5- and 6-(aminomethyl)fluorescein.

5(6)-Carboxyfluorescein is protected as the diacetate then reduced to 5(6)-(hydroxymethyl)fluorescein diacetate. The separated isomers are subjected to a Mitsunobu reaction with dibenzyl imidodicarbonate, yielding diprotected 5- and 6-(aminomethyl)fluorescein diacetate. Methanolysis of the acetates followed by deprotection with HBr/acetic acid gives 5- and 6-(aminomethyl)fluorescein hydrobromide.     

Mechanistic studies on type I and type II dehydroquinase with (6R)- and (6S)-6-fluoro-3-dehydroquinic acids

(6R)- and (6S)-6-Fluoro-3-dehydroquinic acids are shown to be substrates for type I and type II dehydroquinases. Their differential reactivity provides insight into details of the reaction mechanism and enables a novel enzyme-substrate imine to be trapped on the type I enzyme.