Synthesis of(±)-descarboxylquadrone

The synthesis of a biologically active anlogue of the antitumor agent quadrone, termed descarboxylquadrone ($\text{3}$), is described.     

Optimization of roasting process and product quality of peanuts

Differential scanning calorimetry (DSC) was used to establish criteria for optimization of raw material selection, roasting process, eating quality, visual appearance, and shelf-life extension of peanuts [1-4]. DSC methods were developed as both predictive and analytical tools to define process operating guidelines and to correlate with traditional quality attributes of roasted peanuts [1-4].     

Oligomeric proanthocyanidins: naturally occurring O-heterocycles

This review covers the flavan-3-ols (catechins), flavan-4-ols/flavan-3,4-diols (leucoanthocyanidins), A-type proanthocyanidins, B-type proanthocyanidins including the procyanidins, prodelphinidins, propelargonidins, proteracacinidins, promelacacinidins, procassinidins, probutinidins, and non-proanthocyanidins with flavan-3-ol constituent units. Newly isolated proanthocyanidins, structure elucidation, syntheses, HPLC/MS analysis, NMR/ conformational analysis, and the effects of proanthocyanidins on human nutrition and health are reported. The literature from January 1999 to December 2001 is reviewed, and 130 references are cited.     

Molecular structures and ab initio molecular orbital calculations of the optically active derivatives of 1-aminocyclopropane-1-carboxylic acid

The novel optically active derivatives of 2,2′-disubstituted-1-aminocyclopropane-1-carboxylic acid (−)-2 and (+)-3 were synthesised from the spiro-azlactone (+)-1. Oxidation of the diol moiety of (+)-3 gave by ring enlargement the racemic mixture of 2,3-dihydrofuran derivative (±)-6. This conversion is explained by stepwise rearrangement of the initially formed tetrasubstituted cyclopropanecarbaldehyde 4 through zwitterionic's reactive intermediate 5. The formation of (±)-6 is preferred energetically as established by ab initio calculations of the ground states and possible intermediates for that rearrangement. The crystal structure and absolute configuration of the compounds (+)-1, (−)-2, (+)-3 and (−)-7 were determined by single-crystal X-ray diffraction method. All four compounds possess Z-configuration of the cyclopropane ring. The dioxolane ring in the structures (+)-1 and (−)-2 adopts half-chair conformation, while the cyclopropane ring and geminally substituted groups in the structures (−)-2, (+)-3 and (−)-7 possess the anticlinal conformation. The molecules of the compound (+)-1 are connected by very weak intermolecular hydrogen bond of C-H?O type. In the compounds (−)-2, (+)-3 and (−)-7inter- and intramolecular hydrogen bonds of N-H?O type were observed. The spiro-compound (+)-1 exhibited a more pronounced inhibitory activity against the proliferation of murine leukemia and human T-lymphocytes cells than other type of tumor cell lines and normal human fibroblast cells.     

The effective potential as an energy density: The one phase region

An explicit formula is given relating the effective potential in a finite volumeP()₂ quantum field theory to the expected energy density under the constraint of a fixed average filed. In the one phase region, i.e., where the classical potential equals its convex hull and has nonvanishing second derivative, it is shown via a central limit theorem that in the infinite volume limit the effective potential is equal to the constrained energy density, provided is sufficiently small.     

Endonucleolytic mutation analysis by internal labeling (EMAIL)

Mismatch-specific endonucleases are efficient tools for the targeted scanning of populations for subtle DNA variations. Conventional protocols involve 5'-labeled amplicon substrates and the detection of digestion products by LIF electrophoresis. A shortcoming of such protocols, however, is the limited 5'-signal strength. Normally the sensitivity of fluorescent DNA analyzers is superior to that of intercalating dye/agarose systems, however, pooling capacities of the former and latter approaches to mismatch scanning are somewhat similar. Detection is further limited by significant background. We investigated the activity of CEL nucleases using amplicon substrates labeled both internally and at each 5'-terminus. The amplicons were generated from exon 8 of the rice starch synthase IIa encoding gene. Signal of both 5'-labels was significantly reduced by enzyme activity, while that of the internal label was largely unaffected. In addition, background resulting from internal labeling was a significant improvement on that associated with 5'-labeling. Sizing of the multilabeled substrates suggests that 5'-modification enhances exonucleolytic activity, resulting in the removal of the dye-labeled terminal nucleotides. We have developed an alternative approach to mismatch detection, in which amplicon labeling is achieved via the incorporation of fluorescently labeled deoxynucleotides, which we have named Endonucleolytic Mutation Analysis by Internal Labeling (EMAIL). The strength of the EMAIL assay was demonstrated by the reclassification of a rice line as being heterozygous for the starch gene. This cultivar was assigned as being homozygous by a previous resequencing study. EMAIL shows potential for the clear identification of multiple mutations amongst allelic pools.     

Raman spectra of As4S4 polymorphs: Structural implications for amorphous As2S3 films

Raman-scattering spectra of α-As₄S₄ and β-As₄S₄ have been determined at 300 and 10 K. Although similar in overall aspect, the spectral signatures of the two polymorphs are clearly distinct. We have made a careful comparison of these first-order crystal line spectra to the sharp features reported in the Raman spectra of freshly-deposited films of amorphous As₂S₃. Prior proposals for the presence of As₄S₄ molecules in the unannealed films are supported by these comparisons, but recent contentions that actual microcrystals of β-As₄S₄ are present in the as-deposited material are clearly contradicted by the absence of any of the lattice-phonon lines which are prominent in the crystals at frequencies below 70 cm^-1.     

Pulsed NMR study of hydronium β-alumina

Pulsed ¹H NMR measurements are reported for hydronium β-alumina powder in the temperature range 77 K < T < 440 K at 16 MHz. Motional narrowing due to translation (E_A = 21 kJ mol^-1 occurs at T > 260 K. Spin-lattice relaxation is non-exponential in both the laboratory and rotating frames. The observed M₂ suggests that reorientation of H₃O⁺ may also occur, but there are no indications of reorientational minima in T₁ or T_1?.     

Application of an almost traceless linker in the synthesis of 2-alkylthiobenzimidazole combinatorial libraries

Resin-bound triphenylphosphine was coupledto 4-fluoro-3-nitrobenzyl bromide, and2-alkylthiobenzimidazoles were synthesized onresin in 4 steps using standard chemistries. Cleavage of the compounds from the resin wasachieved with 10% NaOH in MeOH to leave amethyl group at the attachment point. A totalof 47 amines and 40 electrophiles wereevaluated, defining the scope of the reactions,culminating in the synthesis of an 80-membertest library of high purity as determined by HPLC.