Synthetic Lesson

Synthetic Lesson from Patchouli Alcohol The Trouble with the Last Structural Proof [160]... 

Synthetic Lesson From Quinine 90 The Trouble with Formal Total Syntheses [161a]... 

The large molecular size and ambient operation of enzymes means that they are likely to be more suited to niche applications rather than to high-power devices, but there are important lessons to be leamt from biological catalysis that occurs in conditions under which conventional metal catalysts would fail. Development of synthetic catalysts inspired by the chemistry (although not necessarily the stmctures) of enzyme active sites may lead to future catalysts with new and improved properties. 

How might these four lessons from natural products be applied to synthetic polymers to achieve performance and degradation ... 

All chemicals, natural and synthetic, are toxic - that is, they produce adverse health effects - under some conditions of exposure. It is incorrect (but I m afraid very common) to refer to some chemicals as toxic and others as non-toxic. If this book teaches any lesson, it is that this notion is not correct. 

Approa cKing the problem from the bottom up, the chemist would be seriously challenged to design techniques for the synthesis of nanosized objects with specific geometries and function. Although synthetic methods have become much more sophisticated, the precise control of the three-dimensional structure of macromolecules, let alone assemblies of macromolecules, is in its infancy. Perhaps it is time to take a few lessons from nature. 

The speed at which things go in this business means that those of us who are on the fringes of it are always out of date, because by the time you have mastered the chemistry of 1979, you have replaced it widi the chemistry of 1983. So let me ask this question. There has been a great deal of emphasis here on CIO and on the role of chlorine in the ozone depletion but years ago from Paul Crutzen I learned the lesson that it was the nitrous oxide of the stratosphere and not Sherry Rowland s halocarbons that really held die control of the thing. Joking aside, the upfluxing molecules that do the damage — or do the necessary control, — what are they They are water vapor, they are methane, clearly they are synthetic halocarbons, but what is left of the statement that I had learned a few years ago that perhaps the major control is that due to N2O on its way up ... 

Molecular self-assembly is a widespread phenomenon in both chemistry and biochemistry. Yet it was not until the rise of supramolecular chemistry that attention has been increasingly given to the designed self-assembly of a variety of synthetic molecules and ions. While success in this enterprise has to a large extent reflected the learning of Nature s lessons, it has also been aided by an increased awareness of the latent steric and electronic information implanted in individual molecular components. It seems that there are few areas in contemporary chemistry where human creativity can be so readily expressed. 

A brief discussion of some aspects of alcohol dehydrogenase will be used to illustrate the potential for catalysis. This system is chosen for illustration because it has been studied so extensively. Lessons drawn can be applied in a broader context. The 1,4-dihydropyridine (2a) is the reductant and this affords a nico-tinium ion (1) on transfer of hydride, as illustrated in equation (1). This process is mimicked in many abiotic systems by derivatives of (2 R = alkyl or benzyl), by Hantzsch esters (7), which are synthetically readily accessible, and 1,4-dihydro derivatives (8) of pyridine-3,5-dicarboxylic acid. A typical abiotic reaction is the reduction of the activated carbonyl group of an alkyl phenylglyoxylate (9), activated by a stoichiometric amount of the powerful electrophile Mg(CI04)2, by, for example, (2b equation 8). After acrimonious debate the consensus seems to be that such reactions involve a one-step mechanism (i.e. equation 5), unless the reaction partner strongly demands a radical intermediate, as in the reduction of iron(II) to iron(III). 

Whether merely trying to leam from the lessons of enzymes, or trying to replicate essential features of them synthetically, a great opportunity exists to extend these principles further and develop catalysts that exhibit even greater rate enhancements. 

The birth and adolescence of the synthetic dye industry in the late 19th and early 20th centuries prior to WWI has been a case study in international business and economics. Fundamental lessons about building competitive advantages and industry dynamics that led to German companies ascendance over British, French, European and American rivals have been analyzed meticulously32. 

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