Zipper strategy

The so-called zipper strategy is characterized by starting the cydization process in the middle of the chain and working its way back and forth across toward the ends. 

The "zipper" strategy goes from the middle to the ends. 

The interpolation processor has a double buffered memory that permits updates during processing. Note that interpolation happens on every sample, thereby avoiding zipper noise due to coefficient quantization. This is an expensive strategy, however it always works. 

A common observation for multiple conformations is that bonds and angles can be distorted for the atoms that are at the border between the ordered and the disordered part. A single solution is to duplicate atoms from the ordered part such that strain can be released by small movement of the atoms in the different conformers. This strategy is, of course, at the expense of additional parameters. A typical example are CA-atoms of residues with disordered side chains in many cases the positions of the CB atom will be slightly different between the different conformers, which, naturally, entails different positions of the CA and the other backbone atoms of the respective backbone atoms as well. Including more and more atoms into the disordered parts will successively resolve stereochemical problems but can lead to a zippering up of large part of the stmcture which is not always desirable—some compromise has to be accepted in such cases. 

The second strategy looks very elegant on paper but could be successful only if the polymer-analogous reactions would not proceed randomly but rather start at one terminus of the single-stranded prepolymer and proceed from there along the chain one after the other like a zipper. Such a reaction is statistically unfavorable and therefore very unlikely to take place. 

The combination of carbonylation with other reactions is one strategy often used to make a novel cascade reaction such as a zipper-type reaction [16], In the 1990s Negishi s group has reported a series of palladium-catalyzed cascade reactions involving carbonylation [17],... 

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