Synthesizer Quest

Molecular recognition and the quest for new catalysts in combinatorial syntheses with participation and formation of heterocycles 97LA637. 

In quest of new single-site catalysts for polymerizations of cyclic esters, a series of mononuclear yttrium(lll) complexes have been synthesized which are depicted in Scheme 221. ... 

Mikroreaktorenfur die chemische Synthese, Nachrichten aus der Chemie, May 2000 Chip technology initiates quest for small structures better temperature control on the small scale fast mixing by diffusion several kg productivity per day no novel, but better chemistry perfect control over process parameters corresponding increase in selectivity basic micro-reactor functions selected examples of use micro reactors as routine tools in the laboratory first start-up companies [113],... 

There are natural targets whose syntheses have important practical applications. For example, paclitaxel (marketed as Taxol by Bristol-Myers Squibb) is an anticancer compound originally isolated from the bark of a species of yew tree, but for a long time it seemed that natural sources would not be sufficient to meet the need. Consequently, many chemists developed synthetic approaches to paclitaxel from readily available materials, although these are not yet fully practical for manufacturing. The quest continues, and a semisynthetic route has been developed starting with a compound isolated from yew needles that can be harvested without destroying the tree. An alternative approach has employed plantcell cultures in bioreactors to produce paclitaxel from yew needles (see Chapter 7 for discussion of related matters). 

N-Fmoc-aminooxy-2-chlorotrityl polystyrene (212 mg, 0.95 mmol g 1,0.2 mmol) was placed in a reaction column (1.0 cm diameter alternatively, an appropriate reaction vessel can be used, e.g., Quest 210 synthesizer 5-mL reaction vessel) and preswollen in DCM DMF (1 1, 3mL) for 24 h (note 4). The resin was then washed with DMF (10min, 2.5 mL min-1) and Fmoc-depro-tected by treatment with 20% v/v piperidine in DMF (10 min, 2.5mL min-1). The resin was then washed with DMF (lOmin, 2.5 mL min ), after which excess DMF was removed. 

DCM is redistilled from calcium hydride and stored over molecular sieve. This reaction can be carried out in an oven-dried round-bottomed flask (10 mL) or using the Quest 210 semiautomated synthesizer 5-mL reaction vessels. 

An OMNI Fit (1.Ox 10.0cm) reaction column was used. Alternatively, this can be carried out using either the Quest 210 semiautomated synthesizer or the Advanced ChemTech peptide synthesizer. 

The field of carbon nanostructure research is vast and novel, and it experienced a major breakthrough after the discovery of fullerenes in 1985 [1], and their subsequent bulk synthesis in 1990 [2]. This event opened the minds of various scientists towards discovering novel carbon allotropes. Promptly, yet another allotrop of carbon was observed by Iijima [3], although it had previously been produced by M. Endo et al. in the 1970s by chemical vapor deposition (CVD) [4]. The most recent important advance in the quest for novel forms of carbon constitutes the isolation of graphene layers [5], which exhibit unique and exceptional electrical properties [6]. In addition, graphene nanoribbons have recently been synthesized and produced using diverse methods [7]. 

Later at the Shanghai Institute of Organic Chemistry I was joined by two research assistants, Yi De Xing and Yong Fan Zhou. As mentioned previously, there was as yet no efficient way to synthesize tribenzo[o,c,e]cyclooctene 25 (see Scheme 7). Furthermore, our research effort in the quest of the angle-strained alkyne 27 was halted at the last dehydrobromination step, from which only 28 and 29 were obtained (Scheme 7). The pen-H-H repulsion of the expected planar 27 was considered to be responsible for its instability. We reasoned that a planar derivative of 27, tailored to eliminate this unfavorable interaction, might sustain some degree... 

The HDAC inhibitors TSA and TPX (Fig. 2) have been utilized as structural leads in the early stages of the quest for new and more selective small molecule inhibitors of the HDAC enzyme family. In order to investigate the function of the individual HDAC members, Schreiber et al. synthesized a library of 7200 potential HDAC inhibitors based on the structural features of TSA and TPX [93]. The members of this library were prepared on solid support by means of split pool methods. The key characteristics of these compounds consist of a dioxane-containing capping region and a zinc binding motive, connected via an aliphatic chain. Three different zinc binders, i.e., carboxylic acid, o-aminoanilide and hydroxamic acid were used. 

Pedersen used reactions of nucleophilic substitution to synthesize most of the crown ethers he has obtained. On the other hand, Lehn and his coworkers [17] (Fig. 7.1.4) carried out cyclization reactions involving amide formation under high dilution conditions in their quest for cryptands such as 54. Pedersen analysis of the selective inclusion of alkali metal cations into the crown ethers cavity... 

Most nonlabeled reference steroids can be obtained from Sigma Aldrich (www. sigmaaldrich.com), Steraloids (www.steraloids.com), and Research Plus (www.re-searchplus.com). 3/ ,5/ -Tetrahydroaldosterone was kindly supplied by Dr. Bernhard Dick and 3a,5/l-tetrahydroaldosterone by Quest Diagnostics. Dr. Liwei Guo and Dr. William Wilson synthesized the A7 and A8 steroids used in the studies. 

By screening chemicals for properties that increase risk to the environment, it is possible to move towards the production of safer commercial products. The design of chemicals with reduced potential for adverse effects in the environment may be complicated by a tradeoff between the properties of the chemical that confer benefits and those that confer risks to the environment. This is not new and is an issue with all human activities. In fact, the adverse effects of chemicals synthesized for use by humans may be far less significant in the environment than other activities such as urbanization, use of fossil fuels, and conversion of natural areas to the production of food and fiber. Clearly, the quest for greener chemicals must be conducted in a framework of the evaluation of risks and benefits to humans and the environment. 

Most solid-phase strategies for the preparation and protection of guanidines were developed to enable the use of arginine in solid-phase peptide synthesis. In recent years, however, the biological activity of many guanidines has spurred a quest for more versatile solid-phase syntheses of this class of compound. 

In their quest for large molecular cavities capable of binding molecules or ionic guests, Vogtle and coworkers 1 synthesized non-cyclic polyaza compounds via a repetitive stepwise process (one-directional case Scheme 4.2). The use of two-directional cores (Scheme 4.5), e.g., ethylenediamine, 2,6-di(aminomethyl)pyridine (8) or l,3-di(amino-methyl)benzene, with acrylonitrile afforded the tetranitrile 9, which was reduced with Co(n)-catalyzed borohydride to produce hexaamine 10. This terminal tetraamine was subsequently treated with excess acrylonitrile to generate the octanitrile 11 although the process was terminated at this stage, a foundation of dendrimer construction was established. 

Protected neamine dimers were prepared using a Quest 210 parallel synthesizer. 5-Ethylcarboxyl-1,3,2, 6 -tetraazido-6,3, 4 -tri-6>-benzylneamine (0.0826 mmol/tube was dissolved in 1.5ml/tube containing CH2C12 distributed to each tube, which was then treated with MP-carbodiimide resin (1.15mmol/g) followed by 1,12-dodecylamine (0.0413 mmol/tube). Solutions were agitated 16 hours, filtered, concentrated, and dimers isolated as colorless foams. 

Table 1 Selected experimental neamine dimers prepared using the Quest 210 parallel synthesizer and their corresponding mass spectra characterization...

Metallated benzo[ ]furans play a very important role as nucleophiles in the quest for structurally diverse 2-substituted benzo[3]furans. For example, benzo[3]furan-2-sulfonamide 90 was synthesized by sequential reactions of a benzo[/ ]furan with -BuLi/S02, A -chlorosuccinimide (NCS), and NH4OH (Scheme 52) <1990JME749>. 

In times of multiresistant strains of bacteria, and similar threats, the quest for antibacterial, antifungal, and antimicrobial agents is still ongoing. Not surprisingly, many thiophene derivatives have been synthesized to be tested in this area. 

Merck Temperature Controller Manual Synthesizer, then evolved into the Quest 210 by Argonaut Technologies, Inc., 887 Industrial Road, Suite G, San Carlos, CA 94070, US. 

One of most important aspects of the Cold War was the race to develop and deploy nuclear weapons. The early arms race was largely focused on nuclear fission, but by the 1950s the much more powerful fusion weapons were the main area of development. The competition, however, was not only military, and the quest for new elements became a minor but important competition, primarily between American laboratories and Soviet ones. Because the equipment used to do nuclear research was used to produce elements and material for weapons, the link between the synthesis of new elements and the arms race was direct if one side could produce a new element, it revealed that that side s equipment, resources, and scientists had an advantage over the opposition. Since the equipment, resources, and scientists were also part of the nuclear arms development system, the implication was that the advantage would extend to the weapons. Even without the arms race, the competition to synthesize new elements was fierce, since international scientific status and even Nobel Prizes could be gained by such work. 

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