Substrate flexibility of vicenisaminyltransferase VinC involved in the biosynthesis of vicenistatin

A glycosyltransferase VinC is involved in the biosynthesis of antitumor beta-glycoside antibiotic vicenistatin. It catalyzes a glycosyl transfer reaction between dTDP-alpha-D-vicenisamine and vicenilactam. Previous identification of its broad substrate specificity toward various glycosyl acceptors enabled us to explore the potential of VinC for glycodiversification. In vitro study of the substrate specificity toward several dTDP-sugars with vicenilactam established that VinC displayed activities with alpha-anomers of several dTDP-2-deoxy-D-sugars such as mycarose, digitoxose, olivose, and 2-deoxyglucose to afford respective beta-glycosides. Notably, beta-anomers of dTDP-2-deoxy-D-sugars also appeared to be accepted by VinC to form alpha-glycosides. Furthermore, VinC is capable of catalyzing glycosyl transfer reactions from both the alpha-anomer and beta-anomer of dTDP-l-mycarose, respectively, into beta-glycoside and alpha-glycoside. These results indicate that VinC is a unique glycosyltransferase possessing broad substrate specificity. The mechanism of this axially oriented glycosidic bond formation from the equatorially oriented dTDP-sugar might be explained by conformational change of dTDP-sugar to a boat conformation during the glycosyl transfer reaction. To apply these features of VinC for glycodiversification, 22 sets of structurally diverse glycosides were constructed using unnatural glycosyl donors and acceptors.     

同步扫描-固体基质室温燐光法同时测定痕量2,6-二氨基嘌呤和硫鸟嘌呤的研究

本文提出了测定痕量2,6-二氨基嘌呤(DAP)和硫鸟嘌呤(TG)的同步扫描纸基质室温燐光(RTP)法,重原子体系为碘化钾加醋酸钠;激发和发射单色器波长差△λ=110nm;同步特征峰位波长分别为299nm(DAP)和330nm(TG)。     

Azo coupling in a series of 2,6-dialkylphenols

Conclusions The authors have studied azo coupling of 2,6-dialkylphenols with p-nitrophenyldiazonium hydro chloride.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1132–1134, May, 1968.We thank N. M. Emanuel' for his interest in this work.     

2,6-二氯甲苯氨氧化制备2,6-二氯苯腈实验

本实验属于化工基础实验 ,采用对环境友好的氨氧化催化法 ,在连续流动固定床反应器上 ,以 2 ,6 二氯甲苯为原料制备重要的有机合成中间体 2 ,6 二氯苯腈。采用正交设计法筛选到合适的反应条件。本实验可以培养学生处理较复杂问题和初步从事多相催化研究的能力     

2,6-Diaminopyridin

Ohne Zusammenfassung     

Conformational flexibility of longifolene

The flexibility of the bicyclo[2.2.1]heptane-based tricyclic bridged system in longifolene is analysed based on x-ray structural data. In this context, the molecular structure of three differently substituted longifolenes has been analysed. The highly substituentdependent conformation provides scope for the synthesis of a variety of commercially oriented products. NCL Communication Number 3459     

Synthesis and reactions of 6-chloro-2,2,6-trimethyl- and 2,6-dichloro-2,6-dimethyl-1-oxa-2,6-disilacyclohexanes

6-Chloro-2,2,6-trimethyl- and 2,6-dichloro-2,6-dimethyl-1-oxa-2,6-disilacyclohexanes have been synthesized. Their behavior in alcoholysis, amination, acetoxylation, and reduction reactions has been studied.     

Regiospecific synthesis of 2,6-bis-indazol-1-ylpyridines from 2,6-bis-hydrazinopyridine

The synthesis of 2,6-bis-hydrazonopyridines from 2,6-bis-hydrazinopyridine and the conversion of these bis-hydrazones into 2,6-bis-indazol-1-ylpyridines were studied. The conversion of bis-haloarylhydrazones to bis-indazoles was systematically optimized using iron and copper mediated reactions and various bases and ligands. By varying solvent, base, transition metal, and ligand, a novel regiospecific route to the 2,6-bis-indazol-1-ylpyridine class of ligands was developed.     

Synthesis of 3,4,7,8-bis(3-R-benzo)-2,6-dithia-1,5-diaza-2,6-dihydroanthracene 2,6-dioxides

Derivatives of a new heterocyclic quinoid system, viz., 3,4,7,8-bis (3-R-benzo)-2,6-dithia-1,5-diaza-2,6-dihydroanthracene 2,6-dioxide, were synthesized by the oxidation of 3,4,7, 8-bis (3-R-benzo)-2,6-dithia-1,5-diaza-1,2,5,6-tetrahydroanthracene 2, 6-dioxides with lead tetraacetate in acetic acid or with phenyliodoso diacetate in benzene.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 343–345, March, 1985.     

Conformational flexibility of DNA

Pulsed Electron-Electron Double Resonance (PELDOR) on double-stranded DNA (ds-DNA) was used to investigate the conformational flexibility of helical DNA. Stretching, twisting, and bending flexibility of ds-DNA was determined by incorporation of two rigid nitroxide spin labels into a series of 20 base pair (bp) DNA duplexes. Orientation-selective PELDOR experiments performed at both X-band (9 GHz/0.3 T) and G-band (180 GHz/6.4 T) with spin label distances in the range of 2-4 nm allowed us to differentiate between different simple models of DNA dynamics existing in the literature. All of our experimental results are in full agreement with a dynamic model for ds-DNA molecules, where stretching of the molecule leads to a slightly reduced radius of the helix induced by a cooperative twist-stretch coupling.     

Synthesis and reactions of 6-chloro-2,2,6-trimethyl- and 2,6-dichloro-2,6-dimethyl-1-oxa-2,6-disilacyclohexanes

6-Chloro-2,2,6-trimethyl- and 2,6-dichloro-2,6-dimethyl-1-oxa-2,6-disilacyclohexanes have been synthesized. Their behavior in alcoholysis, amination, acetoxylation, and reduction reactions has been studied.     

Dimethylamine as a Substrate in Hydroaminoalkylation Reactions

Transition‐metal‐catalyzed hydroaminoalkylations of alkenes have made great progress over the last decade and are heading to become a viable alternative to the industrial synthesis of amines through hydroformylation of alkenes and subsequent reductive amination. In the past, one major obstacle of this progress has been an inability to apply these reactions to the most important amines, methylamine and dimethylamine. Herein, we report the first successful use of dimethylamine in catalytic hydroaminoalkylations of alkenes with good yields. We also report applicability for a variety of alkenes to show the tolerance of the reaction towards different functional groups. Additionally, we present a catalytic dihydroaminoalkylation reaction using dimethylamine, which has never been reported before.