Sulfides, organic enantiomeric oxidation

The typical S-oxidation with BVMOs allows the formation of chiral sulfoxides from organic sulfides. This oxidation has received much interest in organic chemistry due to its use in the synthesis of enantiomerically enriched materials as chiral auxiliaries or directly as biologically active ingredients. This reaction has been studied extensively with CHMO from Adnetohacter showing high enantioselectivi-ties in the sulfoxidation of alkyl aryl sulfides, disulfides, dialkyl sulfides, and cychc and acyclic 1,3-dithioacetals [90]. CHMO also catalyzes the enantioselective oxida-hon of organic cyclic sulfites to sulfates [91]. 

Asymmetric synthesis has emerged as a major preparative method, widely used in organic chemistry and in the total synthesis of natural products, and which is also of interest for industrial chemistry. The importance of enantiomerically pure compounds is connected with the applications in pharmaceutical industries, since very often the biological activity is strongly linked to the absolute configuration. In this article the historical developments of asymmetric synthesis will be briefly presented, as well as the main methods to prepare enantiomerically enriched compounds. Then recent asymmetric synthesis of two classes of compounds will be discussed i) Sulfoxides, chiral at sulfur ii) Ferrocenes with planar chirality. The last part of the article will be devoted to asymmetric catalysis with transition-metal complexes. The cases of asymmetric oxidation of sulfides to sulfoxides and nonlinear effects in asymmetric catalysis will be mainly considered. 

Some similarities with the Murchison meteorite can be noticed. The Murchison mineral structure is dominated with a phyllosilicate (serpentine) matrix which contains minerals such as olivine, pyroxenes, calcium carbonates, iron oxides (magnetite), iron-nickel sulfides and sulfates [23-25]. It has been altered by water, by heat, by pressure shock waves, by short-lived radionuclides [26,27]. The transformation of olivine and pyroxene chondrules seems to grow with the extent of mineral hydrolysis and the formation of water-soluble organic compounds is described at temperatures below -125 C [28,29]. Aside from any terrestrial contamination, all the classes of organic molecules considered of biological relevance are identified [30-32 and Ref therein] and also non-terrestrial amino acids and enantiomeric excesses [33-35]. 

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