Extra long step

In Sect. 5.7 the shape of the staircase boundary of the table of formulas was discussed. It was inferred that it consists exclusively of short (one-formula) steps and long (two-formula) steps. Here we shall give alternative demonstrations for the fact that there cannot be any "extra long steps" or "high steps". Suppose there was an extra long (three-formula) step as illustrated below. 

An extra purification step is needed when long DNA fragments are used after step 4, add 1 volume of alkaline precipitation solution and 2.5 volumes of cold 100% ethanol (mix gently) and incubate for at least 20 min at -20°C (see Note 7). 

We were pleased to find that the proposed Pictet-Spengler cyclization worked remarkably well with all the substrates explored, as long as the C4-carbon was sp -hybridized (i.e., alcohol, ether, or even dioxalane Scheme 13). All reactions cleanly produced C3-C2 cyclization, and neither the potential C3-C4 cyclization nor oxazole formation was observed. More encouragingly, the C4-dioxolane (57) underwent postcyclization hydrolysis in situ to furnish dihydroazaindole 58 directly. This observation eliminated the need for an extra deprotection step in the downstream sequence and allowed access to both the tetrahydro- (such as 53 and 54) and 6,7-dihydro systems (such as 56 and 58). 

Batch continuous processing, in which part of the catalytic solution is removed to a low pressure distillation unit, on the other hand, has recently been commercialised [2-4]. Very little information is available in the public domain concerning this low pressure distillation process, but the main extra cost will be in generating the reduced pressure required for the distillation. The estimated vapour pressures at 110°C of various long chain linear aldehyde products that are commercially desirable are shown in Figure 9.1. This temperature has been chosen because this is the high temperature limit above which the rhodium triphenylphosphine complex starts to decompose. Any commercial process will require to operate the product distillation step at a pressure no higher than those shown for the individual aldehydes. 

Chiral auxiliaries play a key role in the scale up of initial samples of materials and for small quantities. In addition, this method of approach can be modified to allow for the preparation of closely related materials that are invariably required for toxicologic testing during a pharmaceutical s development. There are a number of advantages associated with the use of an established auxiliary The scope and limitations of the system are well defined it is simple to switch to the other enantiomeric series (as long as mismatched pairs do not occur) concurrent protection of sensitive functionality can be achieved. This information can result in a short development time. The auxiliary s cost has the potential to be limited through recycles. However, the need to put on and take off the auxiliary unit adds two extra steps to a synthetic sequence that will reduce the overall yield. Most auxiliaries are not cheap, and this must be considered carefully when large amounts of material are needed. Finally, because the auxiliary has to be used on a stoichiometric scale, a by-product—recovered auxiliary—will be formed somewhere in the sequence. This byproduct has to be separated from the desired product sometimes, this is not a trivial task. 

Such a diffused effect is not in contradiction to the retention of homogeneity as shown by stepwise adsorption. As long as all of the surface sites are affected equally by any changes, the homogeneity will be preserved. The direct effects of extra defects introduced into the graphitized carbon may not destroy the stepped isotherm simply because of too low a concentration. 

In the production of a block copolymer, one extra step is added. First, a long chain of styrene monomers is produced. Then a long chain of butadiene monomers is made. Next, the two chains are joined to each other. Finally, additional chains of polystyrene and polybutadiene are added, making a very long chain consisting of alternating blocks of polystyrene and polybutadiene. 

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