Constitutional dynamic synthesis

Hickman DT, Sreenivasachary N, Lehn JM (2008) Synthesis of components for the generation of constitutional dynamic analogues of nucleic acids. Helv Chim Acta 91 1-20... 

The reduction of yff-ketoesters to aldols is one of the most important applications of Ru(II)-BlNAP catalysts [7]. As a special bonus, the chirally labile C2 stereogenic center can be exploited in a dynamic kinetic resolution such that racemic reactants yield only one of the four conceivable stereoisomers in high diastereomeric and enantiomeric excess. This strategy has been extended to the reduction of -ketophosphonates 10. The 3-hydroxyphosphonic acids 7 which are accessible by this route constitute promising starting materials for the synthesis of peptide analog and antibiotics [8]. 

The modal constitution of things and humans requires a model of modalities , an analysis and a synthesis of the modalities of human actions in a material and social context shaped by a web of connections and arrangements. These modalities refer to the classical modal terms (necessity/obligation, possibility/permissibility, impossibility/impermissibility, contingency/Uberty). But they are not just some formal concepts, they are also meant to reflect some informal experiences of human beings who produce some situated judgments as lived and expressed in modal terms. Moreover, this view is not a static picture, but refers to a dynamic pnxress in which the scope of possibilities of the users can vary depending upon the variation of the elements and their relations that make a world. 

The cycloadduct 113 was then transformed into y,3-unsaturated cyclohexenone 114, which was subjected to intramolecular [4 + 2] cycloaddition. Upon exposure to pyrrolidine in MeOH at 60°C, enone 114 afforded intramolecular Diels-Alder adduct 116 in 78% yield after chromatography. This seemed to be the result of initial reversible iminium formation via dehydrative condensation of pyrrolidine and enone 114. Under the reaction condition, isomerization of the transient iminium species to several distinct dienamine constitutional and stereoisomeric forms would occur. Among all possible isomers in dynamic equilibration, only dienamine 115 is conducive to a favorable intramolecular Diels-Alder transition state, resulting in ketone 116 after enamine hydrolysis. The final steps of the synthesis involved Wittig methylenation followed by... 

To acquire a certain perspective, I shall provide first a brief history of MLCs and PLCs. Then I shall discuss mesophases liquid crystals constitute only one of three kinds of mesophases. Further, I shall compare heterogeneous (that is, ordinary) composites, molecular composites and PLCs. Then we shall go to the heart of this chapter the nature of liquid crystallinity and its manifestations. On this basis we shall be able to survey existing and potential structures of PLCs, using a classification developed earlier. We shall see connections between a place in this classification and properties. Thus, this chapter provides an overview of the field. Chapters 1-3 form the first part of the book, including structures, characterization and dynamics. Subsequent chapters deal with specific properties, synthesis procedures, morphologies, processing and applications. 

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