Hydroxylation inhibition

The fine antimony mist formed from the decomposition of the trichloride also participates in the flame-inhibiting process, deactivating oxygen, hydrogen, and hydroxyl radicals. 

The antitumor activity of geldanamycin and its derivatives appears to result from inhibition of DNA synthesis whereas RNA synthesis is not affected (261). The antitumor activity of the maytansinoids also appears to result from the inhibition of DNA synthesis. The mechanism of action of maytansine (104) has been hypothesized to be the acid catalyzed loss of water from the C-9 hydroxyl group of the carbinolamide to form a reactive acyl imine intermediate, which reacts rapidly with nucleophiles on the bases of DNA (262). 

Alanine, ( )- -(2-amino-1,3-selenazol-4-yl)-synthesis, 6, 343 Alanine, phenyl-p-hydroxylation, 7, 565 Alanine, selenienyl-synthesis, 4, 964 Alanine, y3-2-selenienyl-applications, 4, 970 Alanine, y3-3-selenienyl-applications, 4, 970 Alanine, y3-2-thienyl-biological activity, 4, 911 Alanine, -3-thienyl-biological activity, 4, 912 L-Alanine, y-L-glutamyl-y3-pyrazolyl-occurrence, 5, 303 L-Alanine, -pyrazolyl-occurrence, 5, 303 Alanine raeemase inhibition, 1, 266 Albendazole... 

FIGURE 5.46 Interaction of the serine hydroxyl residue in the catalytically active site of acetylcholinesterase enzyme with esters of organophosphates or carbamates. The interaction leads to binding of the chemical with the enzyme, inhibition of the enzyme, inhibition of acetylcholine hydrolysis, and thus accumulation of acetylcholine in the synapses. 

Cyanohydrins are prepared from unsubstituted 20-ketones by the exchange procedure but not in the presence of a diluent. A 17a-hydroxyl group inhibits the exchange reaction but 20-ketones react with potassium cyanide even in the presence of Ha-bromo or 21-acetoxy substituents. 

Direct halogenation of a 20-ketopregnane (lacking an hydroxyl at C-17) generally does not give satisfactory yields of the 21-bromo derivative, unless the presence of a C-16 substituent e.g., methoxyl or methyl) inhibits formation of the usual 17-bromo primary product. However, an indirect method has been devised. If the 20-ketaI is first prepared, it can be brominated satisfactorily at C-21 using trimethylphenylammonium tribromide as halo-... 

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