Synthesis of some heterocyclic systems from nucleophilic substitution reactions with η6-o-dichlorobenzene-η5-cyclopentadienyliron hexafluorophosphate

A method for the synthesis of heterocylic systems related to 9,10-dihydroanthracene with two hetero-atoms at the 9,10-positions is described. It involves the nucleophilic substitution reaction of η⁶-o-dichlorobenzene-η⁵-cyclopentadienyliron hexafluorophosphate with two nucleophilic groups (OH, SH and/or NH₂) located in the 1,2-positions of a benzene ring to give a cyclopentadienyliron complexed heterocycle. Upon pyrolytic sublimation of the complex, the free heterocyclic compound is then obtained.     

Capacitive-discharge-heated anisotropic pyrolytic graphite furnace used for atomic absorption spectrometry Part 2. Experimental Verification of Temperature Distribution of the Furnace Surface and of the Gas Phase

The predictions of a theoretical model, embodied in a computer program, describing the heating characteristics of the furnace surface and the gas phase of an anisotropic pyrolytic graphite furnace heated by the capacitive discharge technique are compared with the experimental results obtained by optical pyrometry and by two-line atomic absorption spectrometry, respectively. The surface temperature gradient around the circumference of the type 1 furnace and along the optical axis of the type 3 furnace are calculated and compared with the measured temperatures. The weighted-average of the theoretically predicted gas temperature is in reasonable agreement with the effective vapour temperature measured by two-line atomic absorption method. The heating rate of the furnace does not have a significant effect on the temperature distribution of either the furnace surface or the gas phase. The effect of the difference in the temperature distribution of the type 1 and type 3 furnaces on the atomic absorption signals is also discussed.     

On the Parametrization of the Afocal Stable Distributions

Thanks to Hall's documentation of a situation he described asa ‘Comedy of errors’ in the earlier literature onstable distributions, there is now general agreement as to theparametrization of these distributions when standardized asto location and scale. However, two subtly different parametrizationsof location and scale remain current in the afocal stable cases,defined as those with characteristic exponent = 1 and skewnessparameter ß 0. The more widely used parametrization,adopted by Hall and two recent monographs, lacks the linearityproperty that is ordinarily expected of location and scale parameters.This note shows that the alternative parametrization has thislinearity property, and compares the implications of the twoparametrizations for properties of stable distributions. A thirdrecent monograph seeks to avoid these issues by denying thatthe afocal stable distributions are stable at all, but it isshown that they are, in fact, integral members of the stablefamily.     

Transformation of aminoacyl tRNAs for the in vitro selection of "drug-like" molecules

Evolutionary approaches are regularly used to isolate single molecules with desired activities from large populations of nucleic acids (approximately 10(15)). Several methods have also been developed to generate libraries of mRNA-encoded peptides and proteins for the in vitro selection of functional polypeptides. In principal, such mRNA encoding systems could be used with libraries of nonbiological polymers if the ribosome can be directed to polymerize tRNAs carrying unnatural amino acids. The fundamental problem is that current chemical aminoacylation systems cannot easily produce sufficient amounts of the numerous misacylated tRNAs required to synthesize a complex library of encoded polymers. Here, we show that bulk-aminoacylated tRNA can be transformed into N-monomethylated aminoacyl tRNA and translated. Because poly-N-methyl peptide backbones are refractory to proteases and are membrane permeable, our method provides an uncomplicated means of evolving novel drug candidates.     

Synthesis of some heterocyclic skeletons via organoiron complexes. Crystal and molecular structure of (5a,6,7,8,9,9a-η6-1,4-benzoxathiino[3,2-b]pyridine)(η5-cyclopentadienyl)iron hexafluorophosphate

Synthesis of the heterocyclic skeletons of some biologically active compounds from (η⁶-o-dichlorobenzene)(η⁵-cyclopentadienyrl)iron hexafluorophosphate in a two step procedure is described. Cyclopentadienyliron hexafluorophosphate complexes of 1,4-benzodioxino[2,3-b]pyridine, 1,4-benzoxathiino[3,2-b]pyridine, 10H-pyrido[3,2-b]benzoxazine, benzo[b]naphtho[2,3-e][1,4]dioxin, 4-methylbenzo[b]benzopyran-2-one[7,6-e][1,4]dioxin and benzo[b]anthracen-9,10-diono[1,2-e][1,4]dioxin were isolated and characterized. Upon pyrolytic sublimation of these complexes the free heterocycles were obtained and characterized. (η⁶-1,4-Benzoxathiino[3,2-b]pyridine)(η⁵-cyclopentadienyl)iron hexafluorophosphate crystalizes in the orthothombic system, space group Pbca; the dihedral angle between the planes of outer rings was found to be 176.8 (1).