Cambridge Structural Database compilation

An early compilation of X-ray data for heterocyclic compounds <1972PMH(5)1> contains many examples of six-membered rings. More recent data are contained in the Cambridge Structural Database (CSD) . Determination of structures by X-ray crystallography is now routine and details of structures of specific heterocycles are best found using the CSD or by consulting the appropriate chapters in the three editions of Comprehensive Heterocyclic Chemistry. 

A summary of bond lengths and angles from X-ray structures of heterocyclic compounds studied up to 1970 has been published <1972PMH(5)1>. This compilation contains many examples, particularly of furans, thiophenes, and pyrroles and their benzo derivatives further examples are contained in the appropriate chapters of the three editions of Comprehensive Heterocyclic Chemistry. The Cambridge Structural Database (CSD) maintains a comprehensive collection of heterocyclic structures. 

The production of further comprehensive compendia of X-ray and neutron diffraction results has been precluded by the steep rise in the number of published crystal structures, as illustrated by Figure A.l. Printed compilations have been effectively superseded by computerized databases. In particular, the Cambridge Structural Database (CSD) now (October 1992) contains bibliographic, chemical, and numerical results for over 100,000 organo-carbon crystal structures. This machine-readable file fulfils the function of a comprehensive structure-by-structure compendium of molecular geometries. However, the amount of data now held in CSD is so large that there is also a need for concise, printed tabulations of average molecular dimensions. 

Figure 13 Histogram of the shorter P -P separations in crystals containing Ph4P", compiled using data from the Cambridge Structural Database...

Structural data are stored in, and can be accessed from, three primary databases which are continually updated. Data for organic and metal-organic compounds and boranes are compiled by the Cambridge Structural Database (www.ccdc. cam.ac.uk), while crystallographic data for purely inorganic compounds (e.g. metal and non-metal halides and oxides) are deposited in the Inorganic Crystal Structure Database (www.fiz-karlsruhe.de). Structural data for biological macromolecules are collected in the Protein Data Bank (www.rcsb.org/pdb). 

Two new computer-based resources were launched in the 1970s. One was the Cambridge Structural Database (CSD based in Cambridge, England), and the other was the Protein Data Bank (PDB then based at Brookhaven National Laboratory in New York). Computational chemists recognized that these compilations of 3-D molecular structures would prove very useful, especially as more pharmaceutically relevant compounds were deposited. The CSD was supported by subscribers including pharmaceutical companies. On the other hand, the PDB was supported by American taxpayers. 

From comparison of the structure with chemically similar ones, that is, by spotting unusual bond distances or intermolecular contacts. An excellent standard for such comparison is provided by the tables of bond distances in organic and inorganic or coordination compounds, which have been compiled using the Cambridge Crystallographic Database (see below). These tables are also reproduced verbatim elsewhere. ... 

---