Structure generation fragment-based methods

D structures can be generated with fragment-based, data-based, and numerical methods. 

DENDRAL uses a set of rule-based methods to deduce the molecular structure of organic chemical compounds from chemical analysis and mass-spectrometry data. This process includes detecting structural fragments, generating structural formula from these fragments, and verifying it by determining the correlation between... 

Distinct from these are automatic methods that directly transform 2D input information on atoms, bonds, and stereochemistry into 3D atomic coordinates. The automatic methods are classified into rule-based and data-based, fragment-based, conformational analysis, and numerical methods (Fig. 5). These classes of methods overlap more or less with each other and belong more or less to the domain of automatic 3D structure generation ... 

OMEGA is a fast rule-based method and generates the conformation in a systematic manner [74]. It cuts a structure into several torsional fragments and reconstructs the molecule according to different rules with varying torsion angles. Finally, duplicate conformations (which have an RMS rz deviation less than or equal to 0.8 A)... 

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