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Some enantiomerically pure substituted 2-oxazolidinones are excellent as chiral auxiliaries. From the pioneering studies 2 conducted in the early 1980 s of the uses of such auxiliaries has emerged what is perhaps the most widely used method today for the preparation of enantiomerically highly enriched a-alkylalkanoic acids, alcohols and aldehydes, that is, the alkylation of enolates from chiral 3-acylated 2-oxazolidinones followed by auxiliary removal2 59. The early work has been reviewed60-62. These enantiomerically pure cyclic imide auxiliaries have been used not only for alkylations but also in a plethora of a-functionalization reactions, such as diastereoselective aldol, a-hydroxylation, a-amination and Diels-Alder reactions and these are discussed elsewhere in this volume. 

There are excellent HPLC systems available on the market today, yet there is one area of concern with this instrumentation, and this rests with the detection units. Certainly the most widely used detector system employs a low dead-volume micro-ultraviolet detector. This latter unit operates near 200 nm and detects mainly unsaturated linkages in phospholipids (or lipid) samples. Some contribution by carbonyl functions can be expected. This approach is an advantage when the sample under study contains olefinic groups, but will not detect those with saturated side (hydrocarbon) chains. An alternative detector is the refractive index monitor which is often called a universal detector, since it is based on the concept that the refractive index of the solvent changes when a solute is present. The drawback of the latter unit lies in its sensitivity, which is approximately 15- to 20-fold less than that of the ultraviolet monitor. 

The multitude of hetero Diels-Alder reactions found in the literature clearly demonstrates the importance of this transformation. Thus, this type of cycloaddition is today one of the most important methods for the synthesis of heterocycles. Striking features of this method are the tremendous diversity, excellent efficiency especially in those cases where the reactive dienes and dienophiles are formed in situ, and high stereoselectivity in many cases. There is a broad scope and only little limitation. In recent years the use of Lewis acid, the development of diastereoselective and enantioselective reactions as well as the application of high pressure gave an enormous push. In addition, many of the obtained heterocycles can be transformed into acyclic compounds allowing the stereoselective preparation of e.g. amino and hydroxyl functionalized open chain compounds or even carbocycles to be of interest. Also, for the synthesis of natural products, the hetero Diels-Alder reaction is of great value. Since heterocycles,... 

The color formulator must learn as much as possible about the processing conditions the colorant system will encounter. Important conditions to determine are cycle times and process temperatures. Hot runner systems commonly used in today s injection molding processes may add temperature to the polymer melt and add to the time the polymer is under heat. Remember that the heat stability of any colorant and additive system is a function of both time and temperature. An excellent color match may be produced, but if the formulation cannot withstand the stress of processing without breaking down or changing shade, then effort and time have been wasted. 

The process of transforming diffi-action patterns in order to reinstate the underlying crystal structures in the three-dimensional direct space is governed by the theory of diffiaction. The latter rests on several basic assumptions, yet it is accurate and practical. We have no intent to cover the comprehensive derivation of the x-ray diffraction theory since it is mainly of interest to experts, and can be found in many excellent books and reviews. Therefore, in this chapter we will discuss the nature and sources of radiation that are in common use today and consider the principles and fundamental laws of diffraction in general. We will also consider diffraction from a crystalline matter - specifically from polycrystalline materials - and describe diffraction pattern as a function of crystal symmetry, atomic structure and conditions of the experiment. 

The role of experiment and measurement, the function of mathematics, the nature of scientific laws, the difference between laws and theories, the limitations of science, and many similarly provocative topics are treated clearly and without technicalities by an eminent scientist. Still an excellent introduction to scientific philosophy," H. Margenau in Physics Today. A first-rate primer. . . deserves a wide audience, Scientific American. 192pp. 5% x 8. 

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