Spatially directed synthesis

Light-directed, spatially addressable synthesis is a powerful technology for generating chenoical diversity not only of peptides, but also of oligonucleotidesh i] and of other linear polymers-h l... 

Figure 14. Principle of light-directed, spatially addressable synthesis.

Another feature of the diene synthesis, spatial directivity, arises where the diene has substituents or a ring in the 1,4-positions and the dienophile is unsymmetrical with respect to plane D passing through the four reaction centers (Fig. 3c). If the substituent of the dienophile in the transition state will be located on the same side of plane D as the double-bond system of... 

In this section, methods used in the formation, i.e., the directed production, of centers of asymmetry in the total synthesis of steroids are discussed briefly. A study of this question on the basis of steroid molecules and intermediates in their synthesis consisting of condensed cyclic systems requires a consideration of both "static" stereochemistry, i.e., the comparative thermodynamic stability of cyclic systems, and of dynamic stereochemistry, i.e., the spatial directivity of reactions leading to the formation of centers of asymmetry. The existence of comparatively detailed reviews on the stereochemistry of cyclic compounds [15, 65-67] makes it possible for us not to dwell on general principles of stereochemistry but to restrict ourselves to problems connected with their direct use in total synthesis. 

Fodor, S. P. (1991). Light-directed, spatially addressable parallel chemical synthesis. Science 251, 767-773. 

The spatial separation between the components of the electron transport chain and the site of ATP synthesis was incompatible with simple interpretations of the chemical coupling hypothesis. In 1964, Paul Boyer suggested that conformational changes in components in the electron transport system consequent to electron transfer might be coupled to ATP formation, the conformational coupling hypothesis. No evidence for direct association has been forthcoming but conformational changes in the subunits of the FI particle are now included in the current mechanism for oxidative phosphorylation. 

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