核苷环磷酰化反应中的立体化学

我们曾经报道了腺嘌呤核苷3′,5′-环磷酸酯和3′,5′-环磷酰胺对肿瘤细胞的DNA和RNA的合成有明显的抑制作用^[1]。研究这类化合物对进一步了解c-AMP在生物系统中的作用机制以及它们与蛋白激酶和磷酸二酯酶的作用情况有一定价值^[2]。因此在合成一系列腺嘌呤核苷3′,5′-环磷酸酯和3′,5′-环磷酰胺的基础上^[1～3],我们用2′-保护核苷与三价磷试剂反应,经过一步环磷酰化反应合成了核苷3′,5′-环亚磷酸衍生物,后者经氧化和脱保护即可得到核苷3′,5′-环磷酸衍生物。本文将报道核苷环磷酰化反应中的立体化学问题。     

Cyclophosphorylation of polyphenols by diamidoarylphosphites

It was found that the cyclophosphorylation of polyphenols by diamidoarylphosphites proceeds via the rupture of only one P-N bond and one P-O bond, the second P-N bond remaining intact. It is supposed that the unusual lack of reactivity of the P-N bond is due to the spatial arrangement of the amido group with respect to the reaction site in phosphorylated intermediates 5.     

Cyclophosphorylation of tert-Butyldimethylsilyl Derivatives of Cyclodextrins

A convenient method for preparing interglucoside 2,3'-cyclophosphorylated derivatives of cyclodextrins, based on the possibility of incomplete silylation of cyclodextrins by the 6 position of the glucoside units is offered.     

Theoretical Study on First Hyperpolarizabilities of End-Capped Triply Branched Dendrimers

A series of end-capped triply branched dendritic chromophores have been studied by means of density functional theory calculations. It is found that the second order nonlinear optical properties of the end-capped dendrimers are strongly dependent on the mutual orientations of the three chromophores, numbers of caps and the conjugation length of the chromophores. Large enhancement of the ˉrst hyperpolarizability can be obtained when dipole moments of three branches in the dendrimers are highly parallelized.     

First Example of Stereoselective Aza-Perkow Reaction

Russian Journal of General Chemistry -     

Stereodivergent De Novo Synthesis of Branched Amino Sugars by Lewis Acid Promoted Rearrangement of 1,2‐Oxazines

Well concealed : 1,2‐oxazines such as 1 rearrange under Lewis acidic conditions to bicyclic products of type 2 , which can be incorporated into oligosaccharides as protected amino sugar equivalents. Subsequent reductive steps provide unusual oligosaccharides 3 having C2‐branched 4‐amino sugar units. Most of the reactions proceed with excellent stereocontrol and allow the synthesis of a collection of stereoisomers.

     

New Effects in Cyclophosphorylation of Polyatomic Phenols by Phosphorous Acid Amides

Electronic effects in the design of new types of phosphocontaining cavity systems were considered. The matter of this phenomenon consists in supramolecular interaction of the organic radicals of substrates with the cyclophosphorylating reagents.     

The First Example of Optically Active Chlorophosphine: T-Butylphenylphosphinochlorioite

Abstract

In general, alkylthiophosphonium salts can react with nucleophiles both in the sense of the Arbusov rearrangement (a) and the exchange of alkylthio groups at the P atom (b). We have recently demonstrated¹ that in the case of highly “thiophilic” nucleophiles such as mercaptide anions or tris(N, N-dimethylamine)phosphine the reactive centre is the sulphur atom (c).     

First Example of 1,3-Dipolar Cycloaddition of Carbonyl Ylides to Cyclopropenes

Carbonyl ylide generated from 1-diazo-5-phenylpentane-2,5-dione in the presence of Rh₂(OAc)₄ reacts with 3-substituted cyclopropenes following the 1,3-dipolar cycloaddition pattern to afford substituted 9-oxatricyclo[3.3.1.0^2,4]nonan-6-ones.     

Branched tetrazole-containing polymers

It has been established that the polycondensation (polyalkylation) of 5-chloromethyltetrazole occurs in a basic medium to give rise to heterochain oligomeric products. When carried out in the presence of N-H unsubstituted poly(C-vinyltetrazoles), polycondensation yields high-molecular-mass graft copolymers containing side poly(methylenetetrazole) chains. Some properties of branched polymeric products that are characterized by a high density and a large relative content of nitrogen have been studied.     

Branched Aramid Nanofibers

Interconnectivity of components in three‐dimensional networks (3DNs) is essential for stress transfer in hydrogels, aerogels, and composites. Entanglement of nanoscale components in the network relies on weak short‐range intermolecular interactions. The intrinsic stiffness and rod‐like geometry of nanoscale components limit the cohesive energy of the physical crosslinks in 3DN materials. Nature realizes networked gels differently using components with extensive branching. Branched aramid nanofibers (BANFs) mimicking polymeric components of biological gels were synthesized to produce 3DNs with high efficiency stress transfer. Individual BANFs are flexible, with the number of branches controlled by base strength in the hydrolysis process. The extensive connectivity of the BANFs allows them to form hydro‐ and aerogel monoliths with an order of magnitude less solid content than rod‐like nanocomponents. Branching of nanofibers also leads to improved mechanics of gels and nanocomposites.     

Branched Aramid Nanofibers

Interconnectivity of components in three‐dimensional networks (3DNs) is essential for stress transfer in hydrogels, aerogels, and composites. Entanglement of nanoscale components in the network relies on weak short‐range intermolecular interactions. The intrinsic stiffness and rod‐like geometry of nanoscale components limit the cohesive energy of the physical crosslinks in 3DN materials. Nature realizes networked gels differently using components with extensive branching. Branched aramid nanofibers (BANFs) mimicking polymeric components of biological gels were synthesized to produce 3DNs with high efficiency stress transfer. Individual BANFs are flexible, with the number of branches controlled by base strength in the hydrolysis process. The extensive connectivity of the BANFs allows them to form hydro‐ and aerogel monoliths with an order of magnitude less solid content than rod‐like nanocomponents. Branching of nanofibers also leads to improved mechanics of gels and nanocomposites.     

The First Example of Main‐Chain Cyclic Azobenzene Polymers

A novel main‐chain azobenzene cyclic polymer, cyclic‐PEHPA, has been successfully synthesized by ‘click’ cyclization of the α‐alkyne‐ω‐azido hetero‐difunctional linear precursors (linear‐PEHPA), which is synthesized by a step‐growth polymerization of the 3′‐ethynylphenyl[4‐hexyl‐(2‐azido‐2‐methyl‐ propionate) phenyl] azobenzene (EHPA). Gel permeation chromatography, and ¹H NMR and FT‐IR spectra confirmed the complete transformation of linear‐PEHPA into cyclic‐PEHPA. With the same molecular weights, the cyclic‐PEHPAs are found to have higher glass transition temperatures than the linear‐PEHPAs, but almost the same decomposition temperatures. In addition, the obtained cyclic azobenzene polymer with lower molar mass shows a slightly better trans–cis–trans photoisomerization ability than the corresponding linear‐PEHPA.

     

超强酸性室温离子液体反应介质中烷烃羰化研究

在卤化1-烷基吡啶和1-甲基-3-烷基咪唑季胺盐与无水AlCl_3组成的超强酸性 氯铝酸室温离子液中，首次实现了烷烃与CO的直接羰化反应。2，2，4-甲基戊烷可 直接与CO反应，产物为酮。     

First Example of a Heptazine-Porphyrin Dyad; Synthesis and Spectroscopic Properties

We have prepared the first example of a porphyrin linked to an heptazine photoactive antenna. The two entities, linked with an alkyl spacer, demonstrate the activity of both active moieties. While they behave electrochemically independantly, on the other hand the spectroscopy shows the existence of energy transfer between both partners.     

Branched surface-active polylactides

A series of new branched block copolymers was synthesized and investigated, and their physicochemical and surface properties were determined. It was shown that all of the prepared block copolymers demonstrate well-defined surface activity dependent on the ratio of hydrophilic and lipophilic fragments of macromolecule as well as on the copolymer structure. The resulting copolymers were used as surfactants to obtain microemulsions and microcapsules. It was found that the size of emulsion drops stabilized by branched copolymers increased more slowly than that of drops stabilized by linear copolymers. During the preparation of microcapsules through the use of branched copolymers as surfactants, unlike that through the use of linear copolymer surfactants, a high effectiveness of encapsulation and a smaller particle size were observed.     

支化聚烯烃的合成研究*

本文综述了近年来以不同催化体系合成具有不同支化拓扑结构聚烯烃的研究进展。传统的方法主要是通过乙烯自由基聚合和前过渡金属催化剂催化乙烯与希小烯烃共聚来合成支化聚乙烯。其中,原位共聚法可合成得到具有不同支化度、不同支链长度的支化聚乙烯。新发展起来的后过渡金属催化剂,不仅可以催化单一乙烯合成出支化、超支化,甚至是树枝状等一系列不同拓扑结构的聚乙烯,而且可以催化乙烯与极性单体共聚得到末端功能化聚乙烯。