By means of the electron-topologic approach, combining the methods of the pattern recognition theory and the electron and geometric description of the molecular systems under consideration, the totality of 52 sulphur-containing organic compounds is investigated. The electron-topologic activity fragment found allows to characterize correctly all the compounds of the totality and to describe successfully the influence of the structural changes in the molecular systems investigated on the garlic odor appearance.An important class of chemical compounds applied as additives for producing food flavourings is the series of sulphur-containing organic compounds possessing garlic aroma. Application of these compounds in food industry allows a considerable reduction of the valuable plant raw material. In this connection the synthesis of such compounds -flavourings with garlic aroma -is rather an actual task. At the first stage of its solution it is necessary to study the dependence of the exhibited odorant characteristics of the chemical structure.With the determination of the structure-activity relationship one may start the design of the novel compounds characterized by the found structural signs of the activity. At the final stage the directed synthesis is performed and a novel compound is investigated.In the present paper the results are given of the study of structure-odorant activity relationship for the initial sample of 52 sulphur-containing chemical com ounds. The studied series of the chemical compounds was divided into two classes, one of them (the active class g -26 molecules) including the compounds with the characteristic garlic nuance of the aroma, while the other one (non-active class -26 molecules) includes the compounds not possessing the garlic aroma.As it can be seen from Table 1 the samples of chemical compounds in both the classes are characterized by different types of molecular structures. Thus, for example, there are representatives of the acyclic, cyclic, aromatic sulphur-containing compounds, as well as the derivatives of the organic mono-, di-and trisulphides. The given consideration complicates the problem of the search of the structure-activity relationship and does not give the possibility to apply the general methods of the logico-structural analysis [I], oriented at the study of the same type of the compounds of the related structure. In this connection we have tried to use the electron-topologic method worked up earlier which proved useful at the study of the electronic and structural peculiarities of the organic compounds forming their ambergris aroma [2]. This is first of all connected with the fact that at such an approach using Y

An electronic-topological approach has been used to define an active ambergris fragment (AAF) which correctly describes the presence (or absence) of the ambergris odour of all 181 compounds investigated. The AAF consists of one oxygen atom and three carbon atoms (alpha, beta, gamma) which are separated by certain key distances and which possess certain atomic charges. The C(alpha) atom must bear at least one hydrogen atom (H(alpha)) which is located at a certain distance from one of the unshared electronic pairs of the oxygen atom.

By means of the electron-topologic approach suggested earlier, the structural and electronic features favouring meat odour occurrence are evaluated using 77 organic compounds with known odorant properties as a basis for primary logico-structural analysis. A general fragment of the type XH2 (where X = S, O, N is a hetero-atom) with a certain electronic structure and conformational property is shown to be responsible for the meat odour. The results obtained allow for a prognosis of odorant compounds and their purposeful synthesis.

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