Common Substructure

A substructure search algorithm is usually the first step in the implementation of other important topological procedures for the analysis of chemical structures such as identification of equivalent atoms, determination of maximal common substructure, ring detection, calculation of topological indices, etc. 

The similarity of the retrieved protons to those of the query structure, and the distribution of chemical shifts among protons with the same HOSE codes, can be used as measures of prediction reliability. When common substructures cannot be found for a given proton (within a predefined number of bond spheres) interpolations are applied to obtain a prediction proprietary methods are often used in commercial programs. 

Schreiber s model has also proved to be a general approach to a series of oxygenated metabolites of arachidonic acid, such as lipoxin A and lipoxin B.50 The family of linear oxygenated metabolites of arachidonic acid has been implicated in immediate hypersensitivity reactions, inflammation, and a number of other health problems. Among these metabolites, several compounds, such as lipoxin A, lipoxin B, 5,6-diHETE, and 14,15-diHETE possess 1-substituted (/ )-1 -alken-3.4-diol 84 as a common substructural moiety. Therefore, the car-binol 83 is an ideal substrate for generating compound 84 by applying Sharpless epoxidation reaction.50... 

Irreversible Cytochrome P450 Inhibition Common Substructures and Implications for Drug Development... 

Scheme 11.1 The most common substructures causing mechanism-based inactivation of cytochrome P450s ...

Secondary and tertiary amines are very common substructures in drugs and natural compounds but their efficiency and spedfidty as MBIs are highly variable (see Scheme 11.2). 

After the spectral matching process has been completed, the list of compounds with the top matching daughter spectra are identified and retrieved for each daughter spectrum in the reference compound. The molecular structures of the compounds with best matching spectra are drawn and compared for common substructures. The common substructures yield candidate spectrum/substructure correlations. Additional compounds are then tested to confirm or modify each correlation. Once the daughter spectrum is correlated with one or more substructures, this daughter spectrum is stored in the spectrum data base and is linked to the associated substructures stored in the structure data base. 

Common substructural motifs in polyketide natural products are six-membered ring lactones, lactols, and tetrahydropyrans. It was recognized by Wuts and co-workers that hydroformylation of readily available homoaUyhc alcohols would provide a direct and efficient entry into these ring systems. Such an approach was employed in a synthesis of Prelog-Djerassi lactone (Scheme 5.11) [13]. 

A key concept in the assessment of molecular similarity based on chemical graphs is that of a maximum common substructure, MCS(G,GJ), of two chem-... 

Fig. 1. An example of two hydrogen-suppressed graphs G1 G2 and a common substructure CSIG,, G2) and the maximum common substructure MCS(G1 G2) are shown above. The Tanimoto similarity index and the distance between the two chemical graphs are computed below.

Cuissart, B., Touffet, F., Cremilleux, B., Bureau, R., and Rault, S. (2002) The maximum common substructure as a molecular depiction in a supervised classification context experiments in quantitative structure/biodegradability relationships. J. Chem. Inf. Comput. Sci. 42, 1043-1052. 

New methods for the synthesis of 2,4-disubstitued oxazoles are summarized in a recent review. 2-Alkyl-1,3-oxazoles bearing alkyl, aryl, or acyl substitution at C4 are common substructures in natural products. Examples include macrolides such as rhizoxin (4), hennoxazole A (5), and phorboxazole A (6), ° as well as many cyclic peptides that incorporate an oxazole subunit presumably derived from serine. ... 

---