The recent advances in nanotechnology and the corresponding increase in the use of nanomaterials in products in every sector of society have resulted in uncertainties regarding environmental impacts. The objectives of this review are to introduce the key aspects pertaining to nanomaterials in the environment and to discuss what is known concerning their fate, behavior, disposition, and toxicity, with a particular focus on those that make up manufactured nanomaterials. This review critiques existing nanomaterial research in freshwater, marine, and soil environments. It illustrates the paucity of existing research and demonstrates the need for additional research. Environmental scientists are encouraged to base this research on existing studies on colloidal behavior and toxicology. The need for standard reference and testing materials as well as methodology for suspension preparation and testing is also discussed.

Nanomaterials in the environment: Behavior, fate, bioavailability, and effects

Since the discovery of organic azides by Peter Griess more than 140 years ago, numerous syntheses of these energy-rich molecules have been developed. In more recent times in particular, completely new perspectives have been developed for their use in peptide chemistry, combinatorial chemistry, and heterocyclic synthesis. Organic azides have assumed an important position at the interface between chemistry, biology, medicine, and materials science. In this Review, the fundamental characteristics of azide chemistry and current developments are presented. The focus will be placed on cycloadditions (Huisgen reaction), aza ylide chemistry, and the synthesis of heterocycles. Further reactions such as the aza-Wittig reaction, the Sundberg rearrangement, the Staudinger ligation, the Boyer and Boyer-Aube rearrangements, the Curtius rearrangement, the Schmidt rearrangement, and the Hemetsberger rearrangement bear witness to the versatility of modern azide chemistry.

Organic Azides: An Exploding Diversity of a Unique Class of Compounds

Asymmetric 1,3-Dipolar Cycloaddition Reactions

One of the initial steps in the development of therapeutic agents is the identification of lead compounds that bind to the receptor or enzyme target of interest. Many analogs of these lead compounds are then synthesized to define the key recognition elements for maximal activity. In general, many compounds must be evaluated in both the lead identification and optimization steps. Increasing burdens have been placed on these efforts due to the large number of new therapeutic targets that continue to be identified thorough modern molecular biology methods.1 To address this demand, very powerful chemical and biological methods have been developed for the generation of large combinatorial libraries of peptides2 and oligonucleotides3 that are then screened against a receptor or enzyme to identify high-affinity ligands or potent inhibitors, respectively. While these studies have clearly demonstrated the power of library synthesis and screening strategies, peptides and oligonucleotides generally have poor oral activities and rapid in vivo clearance;4 therefore their utility as bioavailable therapeutic agents is often limited. Due to the favorable pharmacokinetic properties of many small organic molecules (<600-700 molecular weight),5 the design, synthesis, and evaluation of libraries of these compounds6 has rapidly become a major frontier in organic chemistry. Lorin A. Thompson was born in Lexington, KY, in 1970. He received the Bachelor of Science degree from the University of North Carolina, Chapel Hill, in 1992 where he worked under the guidance of Joseph Desimone. He is currently pursuing his doctorate in the laboratory of Jonathan Ellman at UC Berkeley where he is the 1994 Glaxo-Wellcome fellow. His research interests include the development of synthetic methodology for organic library construction.

/pdf/synthesis-and-applications-of-small-molecule-libraries-3n3gol8dyk.pdf

Synthesis and Applications of Small Molecule Libraries.

1,2-Amino Alcohols and Their Heterocyclic Derivatives as Chiral Auxiliaries in Asymmetric Synthesis

The present invention relates to a triazole compound represented by the formula (1): ##STR1## wherein R 1 represents a lower alkyl group which may have a substituent; R 2 and R 3 represent respectively hydrogen, an aryl group, a benzoyl group, a tosyl group, a lower alkoxy carbonyl group, or an aryl sulfonyl group, each of which except for hydrogen may have a substituent; provided that when R 2 is hydrogen, the triazole compound is represented by the formula (2): ##STR2## wherein R 1 and R 3 have the same as defined above.

Triazole compounds, their intermediates, and method for production of the same

The stereoselectivity of diene-transmissive Diels–Alder reaction of a cross-conjugated triene, 3-benzylidene-2,4-bis(trimethylsilyloxy)-1,4-pentadiene, with a variety of olefinic dienophiles was investigated. Cyclic dienophiles gave the stereoselective bis-adducts via the endo mono-cycloadducts, whereas the exo mono-adducts were obtained as major products in the reaction with acyclic dienophiles. The steric regulation of diene-transmissive Diels–Alder reaction was discussed.

Stereoselectivity of diene-transmissive diels-alder reaction; cycloaddition reaction of cross-conjugated triene system to olefinic dienophiles

Benzylidene(cyano)benzylamine as a 1,3-dipole

The Condensation of 9-Ethylacridine and p-Nitosodimethylaniline

エナミンがベンジリデンアセナフテノン誘導体に対して,どのような付加反応形式をとるかについて検討した。ベンゼン中べンジリデンアセナフテノン類とN-(1-シクロヘキセニル)ピロリジンーあるいはーピペリジンとの反応では, 1, 4-環化付加体のジヒドロピラン体が生成することを見いだし,その立体構造を明らかにした。IRおよびNMRスペクトルの研究からジヒドロピラン体はベンゼン,THF溶液中では2種の鎖状アルキル化体と平衡混合物として存在することが明からであり,塩酸による加水分解ついでアルコール処理によって1, 5-ジケトンおよびアルコキシジヒドロピラン体とを与えた。さらに重塩酸による加水分解反応の検討から,加水分解反応径路について考察し 1, 5- ジケトンおよびアルコキシジヒドロビラン体は,それぞれ異なるエナミン(モノアルキル化体)を経由して生成したものと推定した。 一方,反応性の弱いN-(1-シクロヘキセニル)モルホリンおよびβー位に水素をもたないN-(2-メチル-1-プロぺニル)ピペリジンはベンジリデンアセナフテノン類とは反応しなかったが,エトキシカルボニルメチレンアセナフテノンとは反応し,異なる型の1:1付加体を与えた。すなわち,前者との反応では1, 4-環化付加によるジヒドロピラン体を与えるのに対し,後者との反応では1, 2-環化付加によるスピロシクロブタン体(過塩素酸塩として単離)が生成した。

Otohiko Tsuge

Papers

Triazole compounds, their intermediates, and method for production of the same

Stereoselectivity of diene-transmissive diels-alder reaction; cycloaddition reaction of cross-conjugated triene system to olefinic dienophiles

Benzylidene(cyano)benzylamine as a 1,3-dipole

The Condensation of 9-Ethylacridine and p-Nitosodimethylaniline

The Reactions of Benzylideneacenaphthenones with Enamines