Asymmetric epoxidation pharmaceutical products synthesis

Examples of Pharmaceutical Product Synthesis In this section, a couple of examples concerning the application of the Mn(salen) asymmetric epoxidation method are described, focusing on cis substituted alkenes as intermediate substrates that are selectively oxidized by this catalytic system. Other examples of application of Mn(salen) on different classes of alkenes for the synthesis of drugs are reported in a recent review paper. ... 

The Shaipless asymmetric epoxidation reaction is often used as a key step in synthetic protocols involving the synthesis of natural products such as terpenes, carbohydrates, insect pheromones, and pharmaceutical products. The SAE reaction is characterized by its simplicity and reliability. The epoxides are obtained with predictable absolute configuration and in high enantiomeric excess (ee). Moreover, 2,3-epoxy alcohols serve as versatile intermediates for a host of stereospecific transformations. 

The importance to use optically pure isomers as pharmaceuticals, food additives, agrochemicals, (etc) is becoming more and more evident. The classical resolution still accounts for a large part of chiral production, however the asymmetric synthesis and the use of chiral separation system one becoming increasingly popular. The enantioseletive hydrolytic resolution of racemic epoxides was performed in the ZSM-5/MCM-41 membrane system containing chiral salen complexes. The chiral salen complexes immobilized on the membrane showed a very high enantioselectivity in the hydrolysis of epichlorohydrine, epoxybutane, styrene oxide and 1,2-epoxyhexane. 

Besides the more common reactions such as hydrogenation, isomerization, alkylation, and the Diels-Alder reaction. Sharpless epoxidation and dihydroxylation by asymmetrical catalysis are rapidly emerging as reactions with immense industrial potential. Table 9.7 lists some important syntheses based on asymmetric catalysis. These include processes for the pharmaceutical drugs (S)-naproxen, (S)-ibuprofen, (,S)-propranolol, L-dopa, and cilastatin, a fragrance chemical, L-menthol, and an insecticide (/ )-disparlure. Deltamethrin, an insecticide, is another very good example of industrial asymmetric synthesis. The total synthetic scheme is also given for each product. In general, the asymmetric step is the key step in the total synthesis, but this is not always so, as in the production of ibuprofen. Many of the processes listed in the table are in industrial production. 

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