Reactions of alkyl diazoacetates with pyridinium ylides

Pyridinium (methoxycarbonyl)methylide generated from (methoxycarbonyl)methyl-pyridinium halides under the action of K₂CO₃ reacts with alkyl diazoacetates in CH₂Cl₂ at 20 °C, resulting in the successive addition of three CHCOOMe fragments from the ylide to form 3,6-bis(alkoxycarbonyl)-4,5-diazaoctadienoic acid diesters. Heating of the latter in the presence of pyridine leads to their isomerization to give tetraalkyl tetrahydropyridazine-tetracarboxylates in high yields. Under more drastic conditions (refluxing xylene in the presence of pyridine), the acyclic tetraesters undergo another transformation to form pyrrole-tetracarboxylic acid esters in yields of up to 60%. Dedicated to Corresponding Member of the Russian Academy of Sciences E. P. Serebryakov on the occasion of his 70th birthday. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 984–988, April, 2005.     

In-tip nanoreactors for cancer cells proteome profiling

Mass spectrometry (MS)-based proteome profiling is essential for molecular diagnostics in modern biomedical study. To date, sample preparation including protein extraction and proteolysis is still very challenging and lack of efficiency. Recently tips-based sample preparation protocols exhibit strong potentials to achieve the goal of “a proteome in an hour”. However, in-tip proteolysis is still rarely reported and far from ideal for dealing with complex bio-samples. In this work, nanoreactors encapsulated micropipette tips were demonstrated as high performance devices for fast (∼minutes) and multiplexing proteolysis to assist the profiling of cancer cells proteome. Nanoporous silica materials with controlled pore size and surface chemistry were prepared as nanoreactors and encapsulated in micropipette tips for efficient in situ proteolysis. The as-constructed device showed desirable sensitivity (LOD of 0.204 ± 0.008 ng/μL and LOQ of 0.937 ± 0.055 ng/μL), selectivity, stability (two months under −20 °C), reusability (at least 10 times), and little memory effect in MS based bottom-up proteomic analysis. It was used for comprehensive protein mapping from cancer cell lines. The number of identified proteins was increased by 18%, 22%, 52%, and 52% dealing with HepG2, F56, MCF7, and HCCLM3 cancer cells, compared to traditional in-solution proteolysis based bottom-up proteomic strategy. With the enhanced performance, our work built a novel, efficient and miniaturized platform for facile proteomic sample preparation, which is promising for advanced biomarkers discovery in biomedical study.     

Amine-terminated organosilica nanosphere functionalized prussian blue for the electrochemical detection of glucose

A new glucose biosensor had been developed by immobilizing positively charged gold nanoparticles (PGNs) on organosilica nanosphere functionalized prussian blue (OSiFPB)-modified gold electrode. The OSiFPB compound could not only effectively prevent the leakage of the PB mediator during measurements, but also easily form stable film on the electrode surface with efficient redox-activity and excellent conductivity. Furthermore, with the negatively charged surface of OSiFPB, this film could be used as an interface to adsorb the PGNs, which provided a congenial microenvironment for adsorbing biomolecules and decreased the electron-transfer impedance. So, with glucose oxidase as a model biomolecular, the proposed sensor showed rapid and highly sensitive amperometric response to glucose and this immobilization approach effectively improved the stability of the electron-transfer mediator. This work would be promising for construction of biosensor and bioelectronic devices.     

Preparation of chitosan functionalized monolithic silica column for hydrophilic interaction liquid chromatography

A novel cationic hydrophilic interaction monolithic stationary phase based on the chemical modification of carboxymethyl chitosan (CMCH) to the monolithic silica skeleton using carbodiimide as an activation reagent was prepared for performing capillary liquid chromatography. The amino and hydroxy moieties of CMCH functioned as both the ion-exchange sites and polar providers. The performance of the column was studied by the separation of polar acidic compounds. The chitosan functionalized monolithic silica column showed good selectivity for nucleosides, nucleotides, aromatic acids and aliphatic acids. The mechanism for the separation of these compounds was also studied. The results showed that these compounds were separated primarily based on the hydrophilic interaction mechanism.     

酸性功能化离子液体催化“一锅法”合成酰胺烷基萘酚

用磺酸型离子液体1-甲基-3-磺酸丙基咪唑硫酸氢盐([MIMPS][HSO₄])催化β-萘酚、芳香醛和酰胺（或脲）3组分“一锅法” 类Ritter反应合成了酰胺烷基萘酚。 投料比为n(β-萘酚)∶n(芳香醛)∶n(酰胺或脲)∶n([MIMPS][HSO₄])=1∶1∶1.3∶0.1,无需溶剂,恒温125 ℃反应5～40 min,通过简单水洗抽滤即可分离产物,酰胺烷基萘酚产率为85%～97%。 离子液体[MIMPS][HSO₄]可回收重复使用4次,其催化活性无明显降低。 探讨了醛、酰胺或脲结构对反应的影响及可能的反应机理。     

RAFT polymerization of a novel allene‐derived asymmetrical divinyl monomer: A facile strategy to alkene‐functionalized hyperbranched vinyl polymers with high degrees of branching

Hyperbranched vinyl polymers with high degrees of branching (DBs) up to 0.43 functionalized with numerous pendent allene groups have been successfully prepared via reversible addition fragmentation chain transfer polymerization of a state‐of‐art allene‐derived asymmetrical divinyl monomer, allenemethyl methacrylate (AMMA). The gelation did not occur until high monomer conversions (above 90%), as a result of the optimized reactivity difference between the two vinyl groups in AMMA. The branched structure was confirmed by a combination of a triple‐detection size exclusion chromatography (light scattering, refractive index, and viscosity detectors) and detailed ¹H NMR analyses. A two‐step mechanism is proposed for the evolution of branching according to the dependence of molecular weight and DB on monomer conversion. Controlled radical polymerization proceeds until moderate conversions, mainly producing linear polymers. Subsequent initiation and propagation on the polymerizable allene side chains as well as the coupling of macromolecular chains generate numerous branches at moderate‐to‐high monomer conversions, dramatically increasing the molecular weight of the polymer. AMMA was also explored as a new branching agent to construct poly(methyl methacrylate)‐type hyperbranched polymers by its copolymerization with methyl methacrylate. The DB can be effectively tuned by the amount of AMMA, showing a linear increase trend. The pendent allene groups in the side chains of the copolymers were further functionalized by epoxidation and thiol‐ene chemistry in satisfactory yields. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2959–2969     

Synthesis,characterization, and star polymer assembly of boronic acid end‐functionalized polycaprolactone

Boronic acid end‐functionalized polycaprolactone (PCL) polymers were synthesized by ring‐opening polymerization using a pinacol boronate ester‐containing (Bpin) initiator. The polymerization provides access to boron‐terminated polymers (i.e. Bpin‐PCL‐OH) with narrow molecular weight distributions (PDI = 1.09). Postsynthetic manipulation of the polymer's terminal hydroxyl group by copper‐catalyzed azide‐alkyne cycloaddition chemistry provides a series of bis end‐functionalized polymers with significant structural diversity at the termini. Deprotection of the boronate ester end group was accomplished with an acidic solid phase DOWEX resin. The boronate ester deprotection methodology does not result in hydrolysis of the polymeric backbone. The boronic acid‐tipped polymers were converted into star polymer assemblies using thermal dehydration and ligand‐facilitated trimerization. Thermal dehydration of (HO)₂B‐PCL‐OAc to the corresponding boroxine‐based star polymer assembly was inefficient and lead to degradation products. Ligand‐facilitated trimerization using either pyridine or 7‐azaindole as the Lewis base was efficient and mild. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis of acid‐sensitive latices by ring‐opening metathesis polymerization

This study describes the synthesis of polynorbornene colloidal particles able to release active molecules in response to pH change. Such functionalized polynorbornene latices with surface active molecules have been obtained by ring‐opening metathesis copolymerization in a dichloromethane/ethanol medium in the presence of α‐norbornenyl poly(ethylene oxide) macromonomer. Two different strategies of introduction of the active molecule—either at their periphery or at their core— have been contemplated. The particles have been characterized by both dynamic light scattering and transmission electron microscopy. Their size was found to range from 260 to 600 nm. The release of the active molecules was monitored by UV spectrometry. After 48 h in an appropriate HCl buffer (pH = 3) more than 80% of the initially linked active molecule was released. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 217–229, 2005     

Copolymerization of ethylene or propylene with α‐olefins containing hydroxyl groups with zirconocene/methylaluminoxane catalyst

Copolymerization of olefins (ethylene and propylene) and 5‐hexen‐1‐ol pretreated with alkylaluminum was performed using [dimethysilylbis(9‐fluorenyl)]zirconium dichloride/methylaluminoxane as the catalyst. The copolymerization required extra addition of alkylaluminum to prevent deactivation of the catalyst when 5‐hexen‐1‐ol was pretreated with trimethylaluminum, whereas the triisobutylaluminum‐treated system did not require any addition of alkylaluminum. The molecular weight of the copolymer depended on the kind of alkylaluminum compound (masking reagent, additive, and cocatalyst). ¹³C NMR analysis proved that poly(ethylene‐co‐5‐hexen‐1‐ol) containing 50 mol % of 5‐hexen‐1‐ol acted as an alternating copolymer, whereas the poly(propylene‐co‐5‐hexen‐1‐ol) acted as a random copolymer. The surface property of the copolymers was simply evaluated by means of water drop contact angle measurement. It was found that the copolymers containing large amounts of 5‐hexen‐1‐ol units showed good hydrophilic properties. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 52–58, 2004     

Synthesis of Dendronized Aromatic Polyamides with Chloromethyl Groups in the Periphery by Macromonomer Approach

The preliminary results for one-pot synthesis of dendronized aromatic polyamides with chloromethyl groups in the periphery by macromonomer approach were reported first time. The GPC analysis of the resulting dendronized polymers has shown typical weight average molecular weight (Mw) of 41554 and a polydispersity of 2.74.