Thermal and palladium-catalyzed [3 + 2] synthesis of cyclopentadienone acetals from cyclopropenone acetals and acetylenes

[reaction: see text] Substituted cyclopentadienone acetals (CPDAs) were synthesized by a thermal or palladium-catalyzed [3 + 2] cycloaddition reaction of a substituted cyclopropenone acetal to an electron-deficient acetylene. The synthesis afforded di-, tri-, and tetra-substituted CPDAs of considerable structural varieties that undergo Diels-Alder reaction to produce bicyclo[2.2.1]heptenes.     

Structure-activity relationship (SAR) studies on oxazolidinone antibacterial agents. 1. Conversion of 5-substituent on oxazolidinone

A structure-activity relationship (SAR) study on 5-substituted oxazolidinones as an antibacterial agent is described. The oxazolidinones, of which 5-acetylaminomethyl moiety was converted into other functions, were prepared and evaluated for antibacterial activity. Elongation of the methylene chain (8) and conversion of the acetamido moiety into guanidino moiety (12) decreased the antibacterial activity. The replacement of carbonyl oxygen (=O) by thiocarbonyl sulfur (=S) enhanced in vitro antibacterial activity. Especially, compound 16, which had the 5-thiourea group, showed 4-8 stronger in vitro activity than linezolid. Our SAR study revealed that the antibacterial activity was greatly affected by the conversion of 5-substituent.     

A theorem on the average number of subfaces in arrangements and oriented matroids

It is known that for simple arrangements in thed-dimensional Euclidean spaceR ^d The average number ofj-dimensional subfaces of ak-dimensional face is less than . In this paper, we show that this is also true for all arrangements inR ^d and for all oriented matroids, and we give combinatorial proofs.     

Crystal structures and topochemical polymerizations of 7,7,8,8-tetrakis(alkoxycarbonyl)quinodimethanes

Highly conjugated monomers, 7,7,8,8-tetrakis(alkoxycarbonyl)quinodimethanes (methoxy (1a), ethoxy (1b), isopropoxy (1c), benzyloxy (1d), chloroethoxy (1e), and bromoethoxy (1f)), were synthesized. Recrystallizations of 1a, 1c, 1e, and 1f yielded two crystal forms (prisms (1a-A) and needles (1a-B), needles (1c-A) and plates (1c-B), prisms (1e-A) and plates (1e-B), and prisms (1f-A) and needles (1f-B)), which have different molecular packing modes by X-ray crystal structure analysis, indicating that the crystals are polymorphic. In the photopolymerizations of these monomer crystals in the solid state, 1a-A, 1e-A, and 1f-A polymerized topochemically to give crystalline polymers. For their thermal polymerizations in the solid state, in addition to 1a-A, 1e-A, and 1f-A, 1e-B and 1f-B polymerized, but polymers formed from the 1e-B and 1f-B were amorphous. The packing of quinodimethane molecules in the crystals was defined by four kinds of parameters, stacking distance (d(s)), the distance between the reacting exomethylene carbon atoms (d(cc)), the angles formed between the stacking axis and longer axis of the monomer molecule (theta(1)), and the shorter axis of the monomer molecule (theta(2)), and then the polymerization reactivity of these quinodimethanes in the solid state was discussed on the basis of these parameters.     

Synthesis and property of soluble poly(1,1′-dialkyl-3,3′-ferrocenylenevinylene)s via titanium-induced dicarbonyl-coupling reaction of 1,1′-dialkylferrocene-3,3′-dicarbaldehydes

1,1′-Dialkylferrocene-3,3′-dicarbaldehydes ( 1a–c ) with long alkyl chains such as ethyl, hexyl, and dodecyl groups were prepared in 13–25% yield via three-step reactions. The titanium-induced dicarbonyl-coupling reaction of 1a–c gave poly(1,1′-dialkyl-3,3′-ferrocenylenevi-nylene)s ( 2a–c ) in quantitative yields, which were the molecular weights of 3000–10,000 and highly soluble in chloroform, benzene, and hexane. The electrical conductivity and the third-order nonlinear optical susceptibility for poly(1,1′-dihexyl-3,3′-ferrocenylenevinylene) ( 2b ) were estimated to be 1 × 10^?2 S/cm on doping with iodine and 1–4 × 10^?12 esu at a wavelength of 1–2.4 μm, respectively. © 1995 John Wiley & Sons, Inc.     

Structure-activity relationship (SAR) studies on oxazolidinone antibacterial agents. 2. Relationship between lipophilicity and antibacterial activity in 5-thiocarbonyl oxazolidinones

5-Thiourea and 5-dithiocarbamate oxazolidinones were synthesized as a continuation of research on 5-thiocarbonyl oxazolidinone antibacterial agents considering the hydrophobic parameters of the molecule. The structure-activity relationship (SAR) study revealed that the antibacterial activity on 5-thiocarbonyl oxazolidinones was significantly affected by the lipophilicity, especially the calculated log P value and the balance between 5-hydrophilic (or hydrophobic) substituent and hydrophobic (or hydrophilic) substituents on the benzene ring. Some of 5-thiocarbonyl oxazolidinones were found to have good in vitro antibacterial activity against gram-positive bacteria including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE).     

Preparation of dehydrated powder of hemoglobin vesicles

The carbonyl hemoglobin (CO-Hb), which was used to prevent denaturation (metHb) during the preparation of samples, was encapsulated into lipid vesicles constituted from unsaturated phospholipid, cholesterol and unsaturated fatty acid. Unsaturated components were polymerized by γ-irradiation to enhance the stability of bilayer membrane. An aqueous dispersion of resulting Hb vesicles was freeze-dried in the presence of saccharides (50–200 mM) to obtain a dehydrated powder of Hb vesicles. Change in the vesicle size, the leakage of encapsulated Hb and the oxidation of Hb to metHb were not observed. Therefore, the long-term storage of Hb vesicles can be realized as a dry powder.