Model of synthon

The topic of the present section is a formulation of an alternative graph-theoretical model of synthons [16,24]. Such an approach makes it possible to build-up all concepts and notions of synthon theory [18-22] in a very transparent and easily understandable level. 

In the present applied model of synthons, directed more towards the actual needs of organic chemistry, we will distinguish diagrammatic cally two kinds of loops. The lone electron pair will correspond to the standard loop, while a single lone electron will correspond to a dashed loop ... 

The notion of reaction distance can be similarly interpreted in the framework of graph-theory model of synthons. Let Gjj be the SR-graph of isomerization S(A) — S (A) it can be written as follows [15,16]... 

PLE catalyzes the hydrolysis of a wide range of meso-diesters (Table 2). This reaction is interesting from both theoretical and practical standpoints. Indeed, the analysis of a large range of kinetic data provided sufficient information to create a detailed active site model of PLE (31). From a practical standpoint, selective hydrolysis of y j (9-cyclo-I,2-dicarboxylates leads to chiral synthons that are valuable intermediates for the synthesis of a variety of natural products. 

J. Koca, M. Kratochvfl, V. Krasmicka, L. Matyska, and J. Posplchal, "Synthon Model of Organic Chemistry and Synthesis Design", Springer-Verlag, Berlin, Heidelberg, 1989. 

The extension of the DU-model, based on the graph theoretical notions and concepts, was developed by our group [16]. This new model of organic chemistry represented by the so-called synthon model, also serves as a theoretical basis for the implementation of the program PEGAS [17]. 

The individual atom and its electronic configuration, the so-called valence state of atom, is the elementary entity of the model philosophy. The modeling of valence states of atoms and their interconversions is then extended to larger systems, the so-called synthons (see Sect. 3.5). 

Initially, the notion of the synthon was, in the frame of formalization of synthetical chemistry, introduced by Corey [23]. Based on the Corey approach, and on the Dungundji-Ugi formalization of chemistry [13], the synthon model of constitutional chemistry was introduced [18,19,21,22,24,16]. In general, it can be understood as a generalized concept of valence states of atoms and their combinations. 

The theory of the synthon model of organic chemistry, presented in previous section, found its realization in the computer program PEGAS (Program for Elective Generation of Accessible Synthons) [48]. This section is devoted to the... 

In previous sections almost all the basic algorithms of the synthon model of organic chemistry were briefly sketched. In this subsection we will present a more rigorous and detailed definition of the key algorithms, as the exact definition is needed for deep understanding of the possibilities, and limitations, of the synthon model. 

The algorithm for the computation of the reaction distance is one of the most important algorithm of the synthon model of organic chemistry. The Principle of Minimal Reaction Distance is a reaction distance analog of the Ugi s Principle of Minimal Chemical Distance and is used as the main heuristic to reduce the number of transformations employed, and synthons generated. The efficiency of the algorithm for the computation of the reaction distance is crucial for unable implementation of the whole synthon model. 

When comparing the model of the mechanism of the Peterson reaction with the scheme of the Wittig reaction generated by PEGAS, we also can find in its output synthons which are analogous to synthons generated for the Peterson reaction (Scheme 20). 

Koca J, Kratochvil M, Kvasnicka V, Matyska L, Pospichal J (1989) Synthon model of organic chemistry and synthesis design, Lecture Notes in Chemistry, vol 51 Springer, Berlin Heidelberg New York... 

Siddiqui KA, Tiekink ERT (2013) A supramolecular synthon approach to aid the discovery of architectures sustained by C-H...M hydrogen bonds. Chemical Communications Matyska L, Koca J (1991) MAPOS a computer program for organic synthesis design based on synthon model of organic chemistry. J Chem Inf Comput Sci 31(3) 380-386 http //ivan.tubert.org/caos/caos.html.Accessed 17 Oct 2012... 

Synthon Model of Organic Chemistry and Synthesis Design... 

The graph model of the synthon has already been introduced in Chap. 3. Let us consider a synthon with graph representation... 

The synthon matrices and synthon graphs are we11-developed formal tools for the description of synthons as a static objects. For the study of conversions of synthons, that is for the dynamic part of synthon model, the basic notion is that of the isomerism of synthons. 

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