Crystal synthon approach

The advantage of using the synthon approach is that it offers a considerable simpHfication in the understanding of crystal structures. For example, the same carboxy dimer motif 1 is present in the structures of benzoic acid, terephthalic acid, isophthahc acid, trimesic acid and adamantane-l,3,5,7-tetracarboxylic acid in zero-, one-, two- and three-dimensional arrangements [9] (see also the article by R. E. Melendez and A. D. Hamilton in this volume). 

Supramolecular Synthon Approach in the Context of Crystal Engineering... 

Sarma, J. Desiraju, G.R. The supramolecular synthon approach to crystal structure prediction. Cryst. Growth Des. 2002, 2 (2), 93-100. 

G. Desiraju supramolecular synthon approach to crystal engineering... 

For application (and indeed the first realisation ) of the supramolecular synthon approach, one requirement is a comprehensive and accessible collection of molecular crystal structures that can be used to identify robust supramolecular... 

Creative concepts in crystal engineering make use of supramolecular synthons to define specific interactions in molecular solids, which may be employed to design crystal packings The synthon approach has been used to produce close packed structures, and, on the contrary, to build open network structures. In the packing motifs of high performance pigments several types of specific interactions (synthons) can be identified. 

Progress in crystal structure prediction has been significant in recent years with parallel synthon-based and crystal structure calculation based approaches. Calculations are now sometimes able to correctly determine crystal structure in an ab initio fashion but analysis of synthons can give significant qualitative insight. 

Practical considerations may also arise. Supramolecular functionality introduced to control crystal architecture must be added without degrading the fundamental molecular properties of primary interest. Co-crystals offer an alternative approach for controlling crystal architecture without necessarily modifying the primary molecule of interest. In addition, we must recognize the role of the solvent from which the crystal grows. The occurrence of solvates and polymorphs, particularly relevant in the pharmaceutical industry, is still a relatively poorly understood aspect of crystal chemistry. The manner in which synthons are modified from normal geometries in non-crystalline organic structures is also yet to be explored fully. 

S,3 S)-83. In the first approach, the functionalization was achieved by reaction of 85 with Br2 to give a mixture of the diastereoisomeric dibromoketones (4S)-87 and (4R)-87, from which, after repeated equilibration/crystallization, the desired c/s-compound (4R)-87 was isolated in 68% yield. Dehydrobromination of (4R)-87 in pyridine gave the monobromo compound 88 from which the dihydroxy compound 89 was obtained by mild hydrolysis with NaHCOa. By treatment of 89 with 2,2-dimethoxypropane, the desired synthon 86 was obtained in a yield of 41 % referred to 85 Scheme 21). 

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