Pd(O) promoted rearrangement of 2-(1,3-butadienyl)cyclopropane- 1,1-dicarboxylate esters to 2-alkenyl-3-cyclopentene-1,1-dicarboxylate esters

The title dienylcyclopropanes smoothly rearrange of five-membered rings in the presence of a Pd(O) catalyst under mild conditions.     

Preparation and biological activity of 2-[4-(thiazol-2-yl)phenyl]propionic acid derivatives inhibiting cyclooxygenase.

A series of 2-[4-(thiazol-2-yl)phenyl]propionic acids substituted at various positions were prepared by the reaction of diethyl 2-methyl-2-(4-thiocarbamoylphenyl)malonates with alpha-bromoaldehyde diethyl acetals or alpha-haloketones followed by hydrolysis of esters. The inhibition of prostaglandin H synthetase (cyclooxygenase) was assayed by use of an enzyme preparation from guinea pig polymorphonuclear leukocytes. Examination of the structure-activity relationship of these compounds indicated that the substitution pattern with halogens at position 3 (R1) of the benzene ring and a methyl group in position 4 (R2) and/or 5 (R3) of the thiazole ring were favorable for inhibitory activity. The compounds bearing bulky alkyl or polar functional groups at the R2 position were weak inhibitors. The potent inhibitors of cyclooxygenase were tested for their ability to reduce carrageenin-induced inflammation of rat paws. These derivatives had strong anti-inflammatory activity based on their strong inhibition of cyclooxygenase, with some exceptions, including those with a thiomethyl group at R1.     

Stereoselective synthesis of vinylgermanes and their facile transformation into vinyl halides

Whereas iododegermylation of (Z)-1-triethylgermyl-1-dodecene gives (Z)-1-iodo-1-dodecene, bromodegermylation proves to give (E)-1-bromo-1-dodecene. Two general procedures for the preparation of vinylgermanes are also described.     

Enantioselective synthesis of martinelline chiral core and its diastereomer using asymmetric tandem Michael-aldol reaction

The martinelline chiral core 3 and its diastereomer were synthesized by using the asymmetric tandem Michael-aldol reaction as the key step from 4-methoxycarbonylanthranilaldehyde and the α,β-unsaturated aldehyde.     

Cleavage of vinyl carbon-silicon bond with tetrabutylammonium fluoride

Dimethylphenylsilyl group is removed from a vinyl carbon with tetrabutylammonium fluoride. The presence of phenyl group on silicon atom plays a critical role. The cleavage of allyldimethylsilyl- and alkoxydimethylsilyl groups also proceeds very easily.     

The study on phosphatidylinositol-specific phospholipase C from Bacillus thuringiensis: synthesis of homogeneous substrates, substrate specificity and other properties.

The properties of phosphatidylinositol-specific phospholipase C (PI-PLC) from Bacillus thuringiensis were studied in detail. The enzyme was extremely thermostable in 0.1% bovine serum albumin and retained 73% of its activity at 100 degrees C for 10 min, while it was labile in the absence of albumin. The enzymatic activity was inhibited by HgCl2 or p-chloromercuriphenylsulfonic acid and restored by dithiothreitol. The kinetic parameters (Km and Vmax) of PI-PLC were determined for the mixed micelle of yeast phosphatidylinositol (PI)/Triton X-100 or sodium deoxycholate. Four PIs having different acyl chains: dilauroylphosphatidylinositol (DLPI), dimyristoylphosphatidylinositol (DMPI), dipalmitoylphosphatidylinositol (DPPI) and dioleoylphosphatidylinositol (DOPI) were synthesized from yeast PI through the processes of deacylation and reacylation, identified by infrared (IR) and Fourier transform nuclear magnetic resonance (FT-NMR) spectra, and subjected to the action of PI-PLC. All the synthetic PIs were hydrolyzed by this enzyme, with DLPI and DMPI being the best substrates. PI-PLC did not catalyze the hydrolysis of the phosphatidylnucleosides 5'-phosphatidylcytidine, 5'-phosphatidyluridine, 5'-phosphatidylthymidine, 5'-phosphatidyladenosine and 5'-phosphatidyl-2'-deoxyadenosine.     

Pd(O) promoted transformation of N-tosyl-2-(1,3-butadienyl)-aziridine into N-tosyl-2-vinyl-3-pyrroline

1,3-Butadienylaziridines activated by N-tosyl group smoothly rearrange to vinylpyrrolidine derivatives in the presence of a catalytic amount of Pd(PPh₃)₄. Transformation of dienylazetidines into vinylpiperidine derivatives is also described.     

Intramolecular cyclization mediated by silylmetalation of acetylenes with PhMe2SiMgMe/CuI and radical nature of the reagent

Whereas CuI catalyzed silylmagnesation of the tosylate of 5- hexyn-l-ol with the title reagent affords dimethylphenylsilylmethylenecyclopentane exclusively, the mesylate of 3-butyn-l-ol gives a mixture of unexpected silylcyclobutene and cyclopropylidene derivative.     

Regioselective stannylmetalation of acetylenes in the presence of transition-metal catalyst

The reaction of terminal acetylenes with Bu₃SnMgMe, Bu₃SnA1Et₂, or (Bu₃Sn)₂Zn in the presence of various transition-metal catalysts provides vinylstannanes in good yields. Whereas copper catalysed stannylmagnesation of 4-benzyloxy-1-butyne gives (E)-4-benzyloxy-1-tributylstannyl-1-butene exclusively, palladium catalysed stannylzincation affords 4-benzyloxy-2-tributylstannyl-1-butene preferentially.     

Modulation of oxygen-carrying capacity of artificial red cells

The oxygen-carrying capacity of artificial red cells (ARC), which were prepared by encapsulating hemoglobin (Hb) into polymerized lipid vesicles, has been investigated in detail. It was found that the effects of inositol hexaphosphate (IHP) on the oxygen affinity of stromafree Hb and ARC are quite different. By co-encapsulating IHP at a IHP:Hb molar ratio of 1.0, the oxygen affinity of the encapsulated Hb in ARC was decreased to such an extent that P₅₀ was about 60–65 mmHg, and only about 70–80% of the encapsulated Hb could be oxygenated at an oxygen partial pressure (Po₂) of about 100 mmHg. As pyridoxal 5-phosphate (PLP) and chloride ions were coencapsulated instead of IHP, P₅₀ and the Hill coefficient of the obtained ARC were adjusted to 25–30 mmHg and 2.5–2.8 respectively. The oxygen-transporting efficiency of PLP-modulated ARC was similar to or better than that of red blood cells.