Entity Restraints

The time line can be a problem, especially when the optimal catalyst has yet to be developed or when no commercial catalyst is available for a particular substrate (substrate specificity) and/or when not much is known about the desired catalytic transformation (technological maturity). When developing a process for a new chemical entity (NCE) in the pharmaceutical or agrochemical industry, time restraints can be severe (see Fig. 1). In these cases it is more important to find a competitive process on time than an optimal process too late. For second generation processes, chiral switches (for existing products sold as racemates) or other products, the time factor is often not so important but here, the process must be the most cost effective. 

Upon the application of stress to the local topological knot, the polymer chain could either break (which is not thought too likely under our conditions of squeezing) or slide (as in the Doi-Edwards slip-link models. In addition, we propose as a possibility that the knot could stretch into a helical-like entity which could be followed by chain slippage. Hiis latter proposal could easily lead to an increase in the number of associative restraints. 

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