Automated library generation

In order to make the Biginelli protocol amenable to an automated library generation format, utilizing the integrated robotic interface of the instrument, attempts were made to dissolve most of the building blocks used in solvents compatible with the reaction conditions. Since many of the published protocols employ either ethanol or acetic acid as solvents in Biginelli-type condensations, a 3 1 mixture of acetic acid... 

Stadler, A. and Kappe, C.O., Automated library generation using sequential microwave-assisted chemistry. Application toward the Biginelli multicomponent condensation, /. Comb. Chem., 2001, 3,624-630. 

This transformation can also be carried out under solvent-free conditions in a domestic oven using acidic alumina and ammoniiun acetate, with or without a primary amine, to give 2,4,5-trisubstituted or 1,2,4,5-tetrasubstituted imidazoles, respectively (Scheme 15A) [69]. The automated microwave-assisted synthesis of a library of 2,4,5-triarylimidazoles from the corresponding keto-oxime has been carried out by irradiation at 200 ° C in acetic acid in the presence of ammonium acetate (Scheme 15B) [70]. Under these conditions, thermally induced in situ N - O reduction occurs upon microwave irradiation, to give a diverse set of trisubstituted imidazoles in moderate yield. Parallel synthesis of a 24-membered library of substituted 4(5)-sulfanyl-lff-imidazoles 40 has been achieved by adding an alkyl bromide and base to the reaction of a 2-oxo-thioacetamide, aldehyde and ammonium acetate (Scheme 15C) [71]. Under microwave-assisted conditions, library generation time was dramatically re-... 

This first section focuses on three major areas library generation method (mixtures and single compounds) chemistry (solid-phase and solution synthesis) and quality/speed (analytical and automation). Finally, the section ends with a chapter reviewing examples where combinatorial chemistry/rapid organic synthesis has been used for discovering novel lead structures for pharmaceutical purposes. 

The use of automation is an important component in library generation. Considerable efforts to develop automated systems for organic chemistry are underway which not only free the chemist for more productive endeavors but also assure consistency in repetitive procedures. 

Pisani L, Prokopcova H, Kremsner JM et al (2007) 5-Aroyl-3, 4-dihydropyrimidm-2-one library generation via automated sequential and parallel microwave-assisted synthesis techniques. J Comb Chem 9 415 21... 

Combinatorial chemistry technology and the merging of automated library synthesis with the traditional medicinal chemistry principles to provide a more rational approach to library generation are providing pharmaceutical companies with millions of... 

The idea and practice of evolving proteins has a long history. The overall process of inducing mutations and then selection for desirable traits has always been present, but the tools to do this work have improved immensely in recent years. Automation has made selection processes much easier, but it is really the advances made in library generation, using PCR, that have revolutionized the field. Prior to PCR, mutations could be... 

The above limitations with solid phase chemistries have necessitated the pursuit of solution-phase chemistries for library generation. The advantages of solution-phase syntheses are legion, but the major benefits include unlimited numbers and types of reaction, lower requirements of solvents and reagents compared to solid phase syntheses and that such chemistries can be developed and monitored with relative ease. A conventional solution-phase chemical synthesis involves the use of arrays of sub millimeter wells as discrete reaction vessels to which the reagents are delivered using automated robotic systems. Although such systems have been successful, the batch nature of... 

In addition, the potential of combined GC mass spectrometry (GC-MS) for determining volatile compounds, contained in very complex avor and fragrance samples, is well known. The subsequent introduction of powerful data acquisition and processing systems, including automated library search techniques, ensured that the information content of the large quantities of data generated by GC-MS instruments was fully exploited. The most frequent and simple identi cation method in GC-MS consists of the comparison of the acquired unknown mass spectra with those contained in a reference MS library. 

P Willett, J Bradshaw and D V S Green 1999. Selecting Combinatorial Libraries to Optimize rsity and Physical Properties. Journal of Chemical Information and Computer Science 39 169-177. 1 and A W R Payne 1995. A Genetic Algorithm for the Automated Generation of Molecules in Constraints. Journal of Computer-Aided Molecular Design 9 181-202. 

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