Special Topic Carbohydrates

We will focus on the development of ruthenium-based metathesis precatalysts with enhanced activity and applications to the metathesis of alkenes with nonstandard electronic properties. In the class of molybdenum complexes [7a,g,h] recent research was mainly directed to the development of homochi-ral precatalysts for enantioselective olefin metathesis. This aspect has recently been covered by Schrock and Hoveyda in a short review and will not be discussed here [8h]. In addition, several important special topics have recently been addressed by excellent reviews, e.g., the synthesis of medium-sized rings by RCM [8a], applications of olefin metathesis to carbohydrate chemistry [8b], cross metathesis [8c,d],enyne metathesis [8e,f], ring-rearrangement metathesis [8g], enantioselective metathesis [8h], and applications of metathesis in polymer chemistry (ADMET,ROMP) [8i,j]. Application of olefin metathesis to the total synthesis of complex natural products is covered in the contribution by Mulzer et al. in this volume. 

The editorial policy of the publication will continue in its past form. To quote from Volume I It is our plan to have the individual contributors furnish critical, integrating reviews rather than mere literature surveys, and to have the articles presented in such a form as to be intelligible to the average chemist rather than only to the specialist. Invitations will be extended to selected research workers to prepare critical reviews of special topics in the broad field of the carbohydrates, including the sugars, polysaccharides and glycosides. It is also the intention to include biochemical and analytical developments in the carbohydrate field as well as critical reviews of important industrial advances. 

This paper, which deals with a rather specialized topic of carbohydrate chemistry, aims to illustrate possibilities and different strategies for the preparation of glycosides of complex molecules such as ergot alkaloids and to show pharmacological perspectives of such work. 

Starches and Other Polysaccharides Used by the Food Industry Enzymes Used to Digest Carbohydrates Absorption of Carbohydrates Special Topic Sugar Transporters I ues in Carbohydrate Nutrition Absorption Physiology... 

F. Special Topics — Resonance, molecular orbital theory, catalysis, acid-base theory, carbon acidity, aromaticity, antiaromaticity, macromolecules, lipids, amino acids, peptides, carbohydrates, nucleic acids, terpenes, asymmetric synthesis, orbital symmetry, polymers... 

The overall scope of this book is the implementation and application of available theoretical and computational methods toward understanding the structure, dynamics, and function of biological molecules, namely proteins, nucleic acids, carbohydrates, and membranes. The large number of computational tools already available in computational chemistry preclude covering all topics, as Schleyer et al. are doing in The Encyclopedia of Computational Chemistry [23]. Instead, we have attempted to create a book that covers currently available theoretical methods applicable to biomolecular research along with the appropriate computational applications. We have designed it to focus on the area of biomolecular computations with emphasis on the special requirements associated with the treatment of macromolecules. 

Enolates represent a special class of sp -hybridized C(l) nucleophiles. This is an important and developing aspect of carbohydrate reactivity and the carbonyl function can either be located at C(2), or be external to the sugar ring (as in sialic acid derivatives). Although the latter are not strictly C(l) nucleophiles, both their value in C-glycoside synthesis and relationship to other topics covered in this chapter merit inclusion of these systems. 

All chiral crown ethers incorporating one carbohydrate subunit possess two diastereo-topic faces of the macrocyclic ring. They are able to form diastereoisomeric complexes with primary alkylammonium cations. Since nonbonding interactions are responsible of the chiral recognition of optically active species, it would be desirable to form monofacial ligands in which the inclusion of a chiral molecule (or chiral ion) could proceed from the sterically hindered side only. This special molecular architecture may be followed by the fusion of the cryptand framework and the chiral unit. 

It may be found desirable to present several reviews of controversial subjects, particularly of those in fields undergoing a rapid state of development. In this way different points of view will find expression. In addition to the presentation of topics covering recent advances, we are providing occasional articles which will review thoroughly special fundamental topics in carbohydrate chemistry. These articles will cover fields which have matured and will be quite complete from the historical standpoint. After a number of years, it is hoped that the aggregate of these articles will provide a fairly complete summary of carbohydrate researches. 

In making the original selection of topics to be covered, specialists were invited to discuss specific carbohydrates, uses of carbohydrates in particular industries, and nutritional and regulative aspects. This was done in order to provide several points of view. The participants were asked also to consider their subjects in terms common to the chemist and therefore not obscured by their particular specialized terminology. The reason for this was the recognition that the choice of a carbohydrate constituent or constituents to be incorporated in a foodstuff is made by the manufacturer not only on the basis of sweetness as, for example, in the case of sucrose, but for a substantial number of other physical, chemical, and economic reasons as well. 

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