Biological halogenation reactions

Alkene halogenation reactions occur in nature just as they do in the laboratory but are limited primarily to marine organisms, which live in a halide-rich environment. The biological halogenation reactions are carried out by enzymes called haloperoxidases, which use H2O2 to oxidize Br or Cl ions to a biological... 

PROBABLE FATE photolysis could be important, photooxidation half-life in water 54.1-541 days, direct photolysis in the stratosphere may occur, but is insignificant in the troposphere, reaction with photochemically produced hydroxyl radicals yields a half-life of 1.45 yrs oxidation atmospheric photooxidation by hydroxyl radicals to COBT2 is relatively rapid hydrolysis too slow to be important, first-order hydrolytic half-life 687 yrs volatilization volatilization has been demonstrated, could be an important transport process, volatilization from moist soil surfaces expected to occur sorption no information is available biological processes slight potential for bioaccumulation/metabolization is known to occur in some organisms other reactionsAnteractions possibly produced by halogen reaction... 

One of the virtues of the Fischer indole synthesis is that it can frequently be used to prepare indoles having functionalized substituents. This versatility extends beyond the range of very stable substituents such as alkoxy and halogens and includes esters, amides and hydroxy substituents. Table 7.3 gives some examples. These include cases of introduction of 3-acetic acid, 3-acetamide, 3-(2-aminoethyl)- and 3-(2-hydroxyethyl)- side-chains, all of which are of special importance in the preparation of biologically active indole derivatives. Entry 11 is an efficient synthesis of the non-steroidal anti-inflammatory drug indomethacin. A noteworthy feature of the reaction is the... 

Nucleophilic substitution is one of a variety of mechanisms by which living systems detoxify halogenated organic compounds introduced into the environment Enzymes that catalyze these reactions are known as haloalkane dehalogenases The hydrolysis of 1 2 dichloroethane to 2 chloroethanol for example is a biological nude ophilic substitution catalyzed by a dehalogenase... 

Caprolactam is an amide and, therefore, undergoes the reactions of this class of compounds. It can be hydrolyzed, Ai-alkylated, O-alkylated, nitrosated, halogenated, and subjected to many other reactions (3). Caprolactam is readily converted to high molecular weight, linear nylon-6 polymers. Through a complex series of reactions, caprolactam can be converted to the biologically and nutritionally essential amino acid L-lysine (10) (see Amino acids). 

Hydrazinopyridazines such as hydralazine have a venerable history as anti hypertensive agents. It is of note that this biological activity is maintained in the face of major modifications in the heterocyclic nucleus. The key intermediate keto ester in principle can be obtained by alkylation of the anion of pi peri done 44 with ethyl bromo-acetate. The cyclic acylhydrazone formed on reaction with hydrazine (46) is then oxidized to give the aromatized compound 47. The hydroxyl group is then transformed to chloro by treatment with phosphorus oxychloride (48). Displacement of halogen with hydrazine leads to the formation of endralazine (49). ... 

Reactions of di-halogens (I2, Br2) and inter-halogens (IBr, IC1) with organic molecules containing Group 16-donor atoms (LE L = organic framework, E = S, Se, Te) have been the subject of renewed interest in the past few years both for their intrinsic interest and for their implications in different fields of research which span from synthetic to biological, material, and industrial chemistry.1 11... 

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