The synthesis of certain 8-cyano-2,4-disubstituted-imidazo[1,5-a] pyrimidines

A number of imidazo[1,5-a]pyrimidine-8-carboxamides were synthesized by reacting various β-dicarbonyl compounds with 5(4)-aminoimidazole-4(5)carboxamide (AICA, 1 ), the non-ribosylated form of AICAR, a key intermediate in the metabolic pathway of purine biosynthesis. Cyclization of 1 with ethylacetoacetate yielded 2-methylimidazo[1,5-a]pyrimidin-1H-4-one-8-carboxamide ( 2 ). The treatment of 2 with phosphorus oxychloride gave 4-chloro-8-cyano-2-methylimidazo[1,5-a]pyrimidine ( 3 ). Various nucleophiles displaced the 4-chloro substituent of 3 under mild conditions. However, the 4-methylthio group of 8-cyano-2-methyl-4-methylthioimidazo[1,5-a)pyrimidine ( 8a ) was also displaced under very mild conditions. Even more strangely, the 4-diethylamino group of 8-cyano-4-diethylamino-2-methylimidazo[1,5-a]pyrimidine ( 5a ) was displaced by ammonia to give 4-amino-8-cyano-2-methylimidazo[1,5-a]pyrimidine ( 7 ).     

The synthesis and reactions of certain pyridazine 1-oxides

Nucleophilic displacement reactions under acidic and basic conditions have been studied with 4,6-dinitro-3-methoxypyridazine 1-oxide ( 1 ) and with 6-chloro-3-methoxy-4-nitropyridazine 1-oxide ( 2 ). Depending on the nature of the nucleophilic reagent and the conditions of the reaction we have found that the chloro group, the nitro group, as well as the methoxy group of 1 and 2 may be displaced by the nucleophile. This type of compound possesses significant in vitro antifungal activity.     

The photochemistry of 4-(n-methylanilino)-pent-3-en-2-one

Low conversion irradiation studies indicate that the cis and trans 3-acetyl-1,2-dimethylindolines are intermediate products in the photosynthetic production of 1,2-dimethylindole from 4-(N-methylanilino)-pent-3-en-2-one.     

Mercury L3 and sulfur K-edge studies of Hg-bound thiacrowns and back-extracting agents used in mercury remediation

Effective methods for the removal of mercury from water are in demand due to the high levels of mercury released from industrial and natural processes. Polymer pendant thiacrown compounds used for the sequestration of Hg(II) from aqueous solutions passed through columns have shown great promise as effective tools for remediation. The mercury can potentially be removed from the columns by extraction with diethyldithiocarbamate (dtc) and diphenylthiocarbazone, aka dithizone (dtz). In this study, Hg L3 and sulfur K-edge X-ray absorption spectroscopy are used to contrast the structure of the mercury thiacrown complex Hg[17]aneS5 with the structure of mercury bound to two potential back-extracting agents, Hg(dtc)₂ and Hg(dtz)₂. In Hg(dtc)₂, it was found that Hg(II) was bound to four sulfur atoms, with two Hg-S bond lengths of 2.66 Å and two Hg-S at 2.49 Å. In Hg(dtz)₂, Hg(II) was bound to two sulfur atoms with Hg-S bond distances of 2.38 Å and two nitrogen atoms with Hg-N at 2.54 Å. This contrasts with Hg[17]aneS5 with three Hg-S bonds at 2.40 Å. Mercury L3 and S K-edge results show that electron density shifts from sulfur in dtc and dtz, to mercury in Hg(dtc)₂ and Hg(dtz)₂.The increase in the number of bonds, and the more stable geometry and electron distribution in the back-extraction complexes confirms that these compounds are more stable than the mercury thiacrown complex, and thus suitable for regeneration of the pendant-arm [17]aneS₅ for further remediation processes.     

Two high-throughput techniques for determining wood properties as part of a molecular genetics analysis of hybrid poplar and loblolly pine

Two new high-through put techniques, computer tomography X-ray densitometry (CT scan) and pyrolysis molecular beam mass spectrometry (pyMBMS), coupled with quantitative trait loci (QTL) analysis, were tested as a means to overcome the time and cost associated with conventional characterization of biomass feedstock components. Applications of these two techniques were evaluated using hybrid poplar for the CT scan and loblolly pine for the pyMBMS. Segregating progeny from hybrid poplar varied in specific gravity, with individual mean estimates ranging from 0.21–0.41. Progeny from loblolly pine varied in lignin, α cellulose, and mannan contents, with individual mean estimates of lignin content ranging from 28.7–33.1%, α cellulose content from 28.8–43.5% and mannan content from 4.2–10.1%. QTL analysis of the loblolly pine data suggested that eleven QTLs were associated with individual feedstock characteristics and that two QTLs for several feedstock components were linked to the same position on the loblolly pine genetic map. Each QTL individually accounted for 7–13% of the total phenotypic variation in associated loblolly pine feedstock components.     

Nanomaterial characterization: considerations and needs for hazard assessment and safety evaluation

Nanotechnology is a rapidly emerging field of great interest and promise. As new materials are developed and commercialized, hazard information also needs to be generated to reassure regulators, workers, and consumers that these materials can be used safely. The biological properties of nanomaterials are closely tied to the physical characteristics, including size, shape, dissolution rate, agglomeration state, and surface chemistry, to name a few. Furthermore, these properties can be altered by the medium used to suspend or disperse these water-insoluble particles. However, the current toxicology literature lacks much of the characterization information that allows toxicologists and regulators to develop “rules of thumb” that could be used to assess potential hazards. To effectively develop these rules, toxicologists need to know the characteristics of the particle that interacts with the biological system. This void leaves the scientific community with no options other than to evaluate all materials for all potential hazards. Lack of characterization could also lead to different laboratories reporting discordant results on seemingly the same test material because of subtle differences in the particle or differences in the dispersion medium used that resulted in altered properties and toxicity of the particle. For these reasons, good characterization using a minimal characterization data set should accompany and be required of all scientific publications on nanomaterials.     

Orientation of irreversible adhesion of spherical particles on prolate spheroidal collectors

When one sphere adheres to a second sphere, the location or orientation of the adhesion on the second sphere is seldom considered. However, when a sphere adheres to a prolate spheroid, the orientation of the adhesion is sometimes critical. We have performed Brownian dynamics simulations to predict the orientation of adhesion of a sphere on a prolate spheroid. When the spheroid has a high rotational diffusion coefficient, simulations show that the spherical particle adheres near the end of the spheroid. We tested our model experimentally for two systems: (1) oppositely-charged spherical and spheroidal colloids and (2) like-charged colloidal spheres and E. coli K-12 D21 bacteria. For the latter case, the spheres have previously been shown to adhere only to one end of the bacterium. Experiments in case (1) support the results of the simulations, while data from case (2) do not agree with predictions. Case (2) data reveal that the end-on adhesion of the spheres on the bacteria is not a purely Brownian phenomenon.