Automated conformational analysis from crystallographic data. 1. A symmetry-modified single-linkage clustering algorithm for three-dimensional pattern recognition

Single-linkage cluster analysis is used to identify discrete conformational subgroups for a chemical fragment from crystal structure data. Fragment conformations are defined by N, torsion angles for N/ occurrences of the fragment in the Cambridge Structural Database. Conformational analysis is complicated by (a) the 2D topological symmetry of the fragment, giving rise to permutations of torsion