A new type of corrin synthesis

Work towards a synthesis of vitamin B₁₂ has inspired a new type of corrin synthesis. The key step is a light-induced 1,16-hydrogen transfer leading to an antarafacial (π→σ)-cycloisomerization of a seco-corrinoid metal complex. The construction of the seco-corrinoid ligand system is achieved by coupling monocyclic ring precursors in their enamide or enamine form through the methods of sulfide-contraction via oxidative coupling and of iminoester-enamine condensation.     

A new type of pH-sensitive phospholipid

We describe the synthesis and characterization of a type of pH-sensitive pentaerythritol phospholipids, using a trialkoxybenzylidene acetal as the acid-labile moiety. This lipid was prepared by an eight-step synthesis via a latentiation strategy. Liposomes were prepared via the thin film extrusion method. The changes of liposomal sizes were measured by dynamic light scattering. Content release rates of the liposomes as a function of pH were monitored by using a calcein fluorescence dequenching assay. These results indicated that this new liposomal system was capable of releasing its contents under mildly acidic conditions. At last, in vitro cytotoxicity was assayed against three cell lines, suggesting this type of phospholipids was low toxic.     

A new catalytic hetero-Heck type reaction

Unsaturated N-chloroamines have been found to cyclise under palladium-catalysis in good yield, the proposed mechanism includes an oxidative addition of the chloroamine to Pd(0), thus opening a new entry to the amides of the late transition metals.     

A new type of abnormal reimer-tiemann reaction

The treatment of l, 2, 3, 4, 4a, 9b-hexahydro-3, 8-dihydroxy-7-methoxy-9b-(2'-methoxyethyl)dibenzofuran with chloroform and aqueous potassium hydroxide under conventional Reimer-Tiemann reaction conditions resulted in the replacement of the 7-methoxyl group by a carbaldehyde one. A choice between alternative pathways for this novel displacement has been facilitated by examination of the behaviour of the corresponding 7-trideuteromethoxy compound. Dichlorocarbene attack at position 7 rather than at the unsubstituted position 9 is shown to be due to steric encumbrance at the latter site.     

A new type of Zeeman-effect atomic-absorption spectrophotometer

A new type of Zeeman-effect atomic-absorption spectrophotometer has been developed. It uses fast heating of a special atomizer made from a pyro-coated graphite tube lined with tungsten-tantalum alloy, for easier determination of refractory and rare-earth elements. A boxcar integrator is used, and the atomic absorption, background absorption and atomization temperature can be recorded. By means of the Zeeman effect, the instrument can correct for background absorbance up to 2.0.     

A new type of calixarene: octahydroxypyridin

A new type of calixarene has been synthesised. Like resorcinol and a number of resorcinol derivatives, 2,6-dihydroxypyridine has been proven to form cyclic tetramers in moderate yields with a number of aliphatic and two aromatic aldehydes in acidic media. The problem of the formation of configurational isomers can be reduced by increasing the reaction temperature and time. With electron-rich aromatic aldehydes, 2,6-dihydroxypyridine unexpectedly yields deep-coloured acyclic quinoid systems. The octahydroxypyridine[4]arenes may have a high potential as receptors for molecular recognition and self organisation.     

A new type of deoxygenation of quinoxaline N-oxides

The reaction of 6-chloro-2-[2-(p-chlorobenzylidene)-1-methylhydrazino]quinoxaline 4-oxide 3a or 2-[2-(p-bromobenzylidene)-1-methylhydrazino]-6-chloroquinoxaline 4-oxide 3b with dimethyl acetylenedicarboxylate under reflux in N,N-dimethylformamide resulted in deoxygenation to give 6-chloro-2-[2-(p-chlorobenzylidene)-1-methylhydrazino]quinoxaline 4a or 2-[2-(p-bromobenzilidene)-1-methylhydrazino]-6-chloroquinoxaline 4b , respectively, while the reaction of compound 3a or 3b with dimethyl acetylenedicarboxylate under reflux in dioxane precipitated dimethyl 8-chloro-4-[2-(p-chlorobenzyli-dene)-1-methylhydrazino]-3aH-isoxazolo[2,3-a]quinoxaline-2,3-dicarboxylate 6a or dimethyl 4-[2-(p-bromobenzylidene)-1-methylhydrazino]-8-chloro-3aH-isoxazolo[2,3-a]quinoxaline-2,3-dicarboxylate 6b , respectively. Further refluxing of compound 6a or 6b in N,N-dimethylformamide provided compound 4a or 4b , respectively.     

A new type of aggregates of cyanine dyes

It was shown that aggregates of a new type are formed in an aqueous solution upon the interaction of dimers of thiamonomethinecyanines and thiapentamethinecyanines. The detected aggregates from the dimers of various dyes are named “heterocontact dimers.” It was concluded that the formation of the heterocontact aggregates is energetically favored over the J aggregates of individual dyes.     

A new type of irreversibly reductively biodegradable hydrogel

Reductively biodegradable hydrogels based on poly[N-(2-hydroxypropyl)methacrylamide] crosslinked with N-[3-(methacryloylamino)propyl] -6-{[5-({[3-(methacryloylamino)propyl]amino}carbonyl)-2-pyridyl]disulfanyl}nicotinamide intended for tissue engineering were synthesized and characterized. The rate of irreversible reductive degradation with thiol l-cysteine (a model of human body where several thiols are present in extracellular space) was studied using several l-cysteine concentrations. The mechanism of the irreversible reductive bond cleavage in the crosslinker structure was confirmed on a low-molecular-weight model. The hydrogel is stable during storage in phosphate buffered saline and is degraded relatively quickly in a concentration-dependent manner after addition of l-cysteine to the surrounding medium.     

A new type of bromide anion conducting solid

A new type of bromide anion conducting solid electrolyte was designed with the solid electrolyte based on oxybromide; the oxybromide lends unique characteristics of thermal stability and water insolubility (5.6 mg in 100 g of water at 25 degrees C) to the electrolyte which shows the highest Br- anion conductivity reported above 500 degrees C.     

A new type of angular phenothiazine ring system

The first synthesis of monoaza- and diaza-analogues of benzo[a]phenothiazine ring system is achieved under anhydrous conditions by base-catalysed reaction of o-aminoheterocyclic thiones with 2,3-dichloronaphtho-1,4-quinone. If the reactions were carried out in methanol, 2-chloro-3-methoxynaphtho-1,4-quinone was also isolated. The ease of air oxidation of the Na₂S₂O₄ reduced compounds makes them suitable for consideration as vat dyes.