Synthesis of some antipyrinylazo and thiazolylazo compounds with pentan-2,4-dione and their reactions with metal ions

The reagents were synthesized by using pentan-2,4-dione as the coupling component with diazotized 4-aminoantipyrine or 2-aminothiazole. Two kinds of azo compounds were obtained under different conditions: 1-(4-antipyrinylazo)-1-(4-antipyrinylhydrazino)propan-2-one (Azonol A-1) and 3-(4-antipyrinylazo)pentan-2,4-dione (Azonol A-2) from 4-aminoantipyrine, and 1-(2-thiazolylazo)-1-(2-thiazolylhydrazino)propan-2-one (TAA-1) and 3-(2-thiazolylazo)pentan-2,4-dione (TAA-2) from 2-aminothiazole. The structure of Azonol A-1 was determined by single-crystal x-ray crystallography. The reactions of these reagents with various metal ions were examined. Azonol A-1 and TAA-1 form metal chelates at low pH values. Azonol A-1 is useful as a metallochromic indicator in titrations of bismuth with EDTA at pH 0.5–2, and as a spectrophotometric reagent for copper (II) (0.2–1.5 mg l^?1) at pH 0.3–1.2.     

UVB DNA Dosimeters Analyzed by Polymerase Chain Reactions

Abstract— Purified bacteriophage Λ DNA was dried on a UV-tran-sparent polymer film and served as a UVB dosimeter for personal and ecological applications. Bacteriophage Λ. DNA was chosen because it is commercially available and inexpensive, and its entire sequence is known. Each dosimeter contained two sets of DNA sandwiched between UV-transparent polymer films, one exposed to solar radiation (experimental) and another protected from UV radiation by black paper (control). The DNA dosimeter was then analyzed by a polymerase chain reaction (PCR) that amplifies a 500 base pair specific region of Λ DNA. Photoinduced damage in DNA blocks polymerase from synthesizing a new strand; therefore, the amount of amplified product in UV-exposed DNA was reduced from that found in control DNA. The average lesion frequency per 500 base pair per strand at 16 PCR cycles was –1.22, 1.00, 0.70 and 0.50 for 30 ng, 50 ng, 100 ng and 150 ng of dried DNA, respectively, after a total dose of 60 kj m 2 delivered with a solar UVB simulator. Although the average lesion frequency increases linearly with increasing doses for four different amounts of template DNA, the lesion frequency seems to be averaged by the amplified products from the protected Λ DNA molecules below the top few layers. The average daily dose, equivalent to the UV dose applied with the solar UVB simulator, was 10.2±0.4 kj m2 with the 50 ng containing DNA dosimeter in September 1995 in Melbourne, FL. Both 50 ng and 150 ng containing DNA dosimeters produced the same average daily dose within experimental error in January 1996, which was 5.2±0.3 kj m 2 at the same location. The dried Λ DNA dosimeter is compact, robust, safe and transportable, stable over long storage times and provides the total UVB dose integrated over the exposure time.     

Synthesis of diversely functionalized hexahydropyrrolo[2,3-b]indoles using domino reactions, olefination, isomerization and Claisen rearrangement followed by reductive cyclization

Hexahydropyrrolo[2,3-b]indoles 6 were synthesized in five steps from indolin-3-one 8 by a general and efficient method, in which elements of molecular diversity were readily added onto the 3a-position of the pyrrolo[2,3-b]indole ring system. Horner-Wadsworth-Emmons reaction of 2-allyloxyindolin-3-ones 7, derived from indolin-3-one 8 and a variety of allylic alcohols, smoothly proceeded with successive Claisen rearrangement to give the corresponding 3-allyl-3-cyanomethylindolin-2-ones 15. Indolin-2-ones 15 were converted into pyrrolo[2,3-b]indoles 6 using partial hydrolysis followed by reductive cyclization with LiAlH(4). Synthesis of N-methylated pyrrolo[2,3-b]indole derivatives 23 and 26 is also described.     

Flavonol glycosides in leaves of two Diospyros species

Fourteen flavonol glycosides including two new compounds were isolated from the leaves of two Diospyros plants (D. cathayensis and D. rhombifolia). The structures of isolated compounds were determined by spectroscopic analysis. The scavenging activity of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical of the isolated compounds was also investigated.     

Acid-catalyzed reactions of 3-(hydroxymethyl)- and 3-(1-hydroxyethyl)pyrazolo[1,5-a]pyridines

Treatment of 3-(hydroxymethyl)pyrazolo[1,5-a]pyridines with trifluoroacetic acid in refluxing dichloro-methane led to the formation of bis(pyrazolo[1,5-a]pyrid-3-yl)methanes or bis[(pyrazolo[1,5-a]pyrid-3-yl)]-methyl ethers depending upon the concentration of trifluoroacetic acid. In contrast, similar treatment of 3-(1-hydroxyethyl)pyrazolo[1,5-a]pyridines gave a mixture of 3-vinylpyrazolo[1,5-a]pyridines and 1,3-bis(pyrazolo-[1,5-a]pyrid-3-yl)-1-butenes.     

Enantioselective total synthesis of ustiloxin D

Ustiloxin D and phomopsin A are potent antimitotic agents that bind to tubulin and interfere with cellular microtubule function. A synthetic strategy has been developed to allow access to both of the natural products as well as a variety of variants of the ustiloxin and phomopsin family members in order to provide sufficient quantities for biological studies. Herein we report the enantioselective total synthesis of ustiloxin D using a longest linear sequence of 20 steps. Four of the five stereocenters were set using catalytic asymmetric methodologies. In particular, Evans's new Al-catalyzed asymmetric aldol reaction facilitated access to both syn and anti products corresponding to the different benzylic stereochemistries found in ustiloxins and phomopsins. In addition, due to its high functional group tolerance, Trost's Pd-mediated etherification was used to construct the chiral tertiary alkyl-aryl ether. Taken together, these synthetic strategies allow us to use densely functionalized intermediates to realize an efficient synthesis of ustiloxin D.     

Absolute configuration and conformation of 1,1′-spirob[benz[g]indan]

Two diastereomers of 3,3′-di-t-butyl-1,1′-spirobi[benz[g]indan] have been prepared; c.d. spectral evidence is presented for the difference between their conformations.     

Effective consideration of ring structures in CAST/CNMR for highly accurate C NMR chemical shift prediction

A new function that effectively takes into account ring structural environments achieves extensive highly accurate prediction of ¹³C NMR chemical shift in the CAST/CNMR system. The approach adapts a fast and flexible ring perception algorithm and a new CAST coding method for the ring information. ¹³C NMR chemical shift prediction is performed for complicated polycyclic natural products and their synthetic intermediates as the demonstration, which shows the reliability of the function in extending the scope of the practically accurate ¹³C NMR prediction for wide range of organic compounds.     

Packing of simulated friction modifier additives under confinement

Molecular dynamics simulations have been conducted to obtain detailed information regarding molecular structure and packing of surfactant-like "friction modifier" (FM) chains adsorbed to two confining surfaces under sliding conditions. The simulations are interpreted via the density profile, position-dependent fluctuations in the density profile, and parallel, interlayer position correlation functions. Heterogeneous FM structures were obtained. The adsorbed FM chains were found to form semi-ordered monolayers perpendicular to the atomically well-defined surface, with distinct segment positions in the density profile. More fluid layers with broader density profiles and larger fluctuations were formed by some unoriented FM chains oriented preferentially parallel to the surface, between the opposing monolayers. Segment position correlations parallel to the surface in the adsorbed layers were found at separations up to 30 A. These packings persisted for longer than 4 ns under sliding conditions that ranged from 0 to 7.5 m s(-1) (0 to 0.075 A ps(-1)). Monolayer structures were observed to remain unchanged under a wide range of normal pressures, with the corresponding changes in volume occurring in the gap between monolayers or between a monolayer and trapped fluid.     

An empirical relation between oscillator strengths calculated from the dipole length and dipole velocity formalisms in the optical absorption of conjugated molecules

It is found that a ratio between the oscillator strengths of the optical absorption calculated from the dipole length formalism and those calculated from the dipole velocity formalism is almost constant for many conjugated molecules if the calculation is made using the theoretically obtained transition energy. The value of the ratio becomes very sensitive to the molecular geometry if the calculation is made using the experimentally obtained transition energy. The origin of the constancy of the ratio is discussed.