Sulfoxidation biological

Impressive advances have been made in biological sulfoxidation in the last decade.25 The results augur that this approach will be of some synthetic interest in the future, instead of being an intellectual curiosity. Both isolated enzymes and whole cells have been used in the enantioselective oxidation of prochiral sulfides. 

Sulfoxide hGH. Methionine residues in proteins are susceptible to oxidation primarily to the sulfoxide. Both pituitary-derived and biosynthetic hGH undergo sulfoxidations at Met-14 and Met-125 (29). Oxidation at Met-170 has also been reported in pituitary but not biosynthetic hGH. Both desamido hGH and Met-14 sulfoxide hGH exhibit full biological activity (29). 

Dimethyl sulfoxide occurs widely at levels of <3 ppm. It has been isolated from spearmint oil, com, barley, malt, alfalfa, beets, cabbage, cucumbers, oats, onion, Swiss chard, tomatoes, raspberries, beer, coffee, milk, and tea (5). It is a common constituent of natural waters, and it occurs in seawater in the 2one of light penetration where it may represent a product of algal metaboHsm (6). Its occurrence in rainwater may result from oxidation of atmospheric dimethyl sulfide, which occurs as part of the natural transfer of sulfur of biological origin (7,8). 

The earliest attempts to obtain optically active sulfoxides by the oxidation of sulfides using oxidants such as chiral peracids did not fare well. The enantiomeric purities obtained were very low. Biological oxidants offered great improvement in a few cases, but not in others. Lately, some very encouraging progress has been made using chiral oxaziridines and peroxometal complexes as oxidants. Newer developments in the use of both chemical oxidants and biological oxidants are described below. 

A number of studies describing the oxidation of sulfides to sulfoxides by biological oxidizing agents have been published over the years2 9,13,107- Microbial systems are often... 

Further examples of the utility of the allylic sulfoxide-sulfenate interconversion in the construction of various biologically active natural products include intermediates such as the /Miydroxy-a-methylene-y-butyrolactones (e.g. 63)128 and tetrahydrochromanone derivative 64129. Interestingly, the facility and efficiency of this rearrangement has also attracted attention beyond the conventional boundaries of organic chemistry. Thus, a study on mechanism-based enzyme inactivation using an allyl sulfoxide-sulfenate rearrangement has also been published130 131. 

Biologically, the reduction of methionine sulfoxide to methionine with NADPH is catalyzed by an enzyme79. Recently, the mechanism of reduction of sulfoxides by treatment with an NADPH model has been studied80. 

Biologically active thioethers and derivatives (including sulfoxides)... 

Intriguing approaches have been developed using mannosyl fluorides,30,31 phosphites,32 and thioglycosides (Scheme 7.8).33 However, their generalities, particularly in terms of applicability to complex and biologically relevant systems, are yet to be clarified. Quite probably, the most successful donor for direct P-mannosylation is the sulfoxide developed by Crich and coworkers (Scheme 7.9).34-37 Glycosyl sulfoxides were originally developed by Kahne and have proved... 

In laboratory tests, several fungi and cultures of actinomycetes isolated from garden soil readily degraded disulfoton (Bhaskaran et al. 1973). In flooded soil under anaerobic conditions, the reduction of disulfoton sulfoxide to disulfoton was due to biological conversion (Tomizawa 1975). 

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