Oxo-acids of nitrogen

The oxo-acids of nitrogen known either as the free acids or in the form of their salts are listed in Tables 15.2.3 and 15.2.4. The structures of these species are shown in Figs. 15.2.2 and 15.2.3. 

Point (a) leads to facts such as the existence of P(OR)3 but not of N(OR)3, nitrogen giving instead 0=N(0R), and the marked differences between the oxides and oxo acids of nitrogen on the one hand and those of phosphorus on the other. 

The researeh on dehydroepiandrosterone (DHEA) is limited beeause of the laek of radiolabeled metabolites. Robinzon et al. [126] showed that, using pig liver mierosomes, the radiolabeled metabolites of DHEA can be prepared in stable, pure form for bioehemical smdies. They utilized pig liver microsomal (PLM) fractions to prepare pH]-labeled 7a-hydroxy-DHEA (7a-OH-DHEA), 7[3-hydroxy-DHEA (7P-OH-DHEA), and 7-oxo-DHEA substrates from 50 pM [1,2,6,7-3H]DHEA. The metabolites were separated by silica gel PLC plates using ethyl aeetate-hexane-gla-eial aeetic acid (18 8 , v/v) as the mobile phase, extracted with ethyl aeetate, and dried under a stream of nitrogen. The purity of markers was determined with the use of TLC and GC/MS. 

Cyclocondensation of malonates and acetaldehyde derivative 227 in boiling ethanol in the presence of catalytic amounts of piperidine and acetic acid under nitrogen also afforded 6-oxo-6//-pyrido[l, 2-a]-pyrimidine-7-carboxylates 228 (91MIP3). 

Tetrahydrofuran (3.2 ml) and S-(+)-3-chloro-l,2-propanediol (0.299 ml, 3.58 mmol, 1.19 eq) are mixed. The mixture of THF (3.2 ml) and S-(+)-3-chloro-1,2-propanediol (0.299 ml, 3.58 mmol, 1.19 eq) is cooled to -16°C and potassium t-butoxide (3.2 ml, 1.0 M) in THF (3.2 mmol, 1.07 eq) is added at less than -10°C. The resulting slurry is stirred at -14-0°C for 1 hour. Then added to the lithium anion mixture while maintaining both mixtures at 0°C, then rinsed in with THF (2 ml). The resultant slurry is stirred at 20-23°C for 2 hour and then cooled to 6°C and a mixture of citric acid monohydrate (0.4459 g, 2.122 mmol, 0.705 eq) in water (10 ml) is added. The resultant liquid phases are separated and the lower aqueous phase is washed with ethyl acetate (12 ml). The organic layers are combined and solvent is removed under reduced pressure until a net weight of 9.73 g remains. Heptane (10 ml) and water (5 ml) are added and solvent is removed 4-nitrobenzenesulfonyl chloride y reduced pressure until a total volume of 5 ml remains. The precipitated product is collected by vacuum filtration and washed with water (7 ml). The solids are dried in a stream of nitrogen to give (R)-[N-3-(3-fluoro-4-(4-morpholinylphenyl)-2-oxo-5-oxazolidinyl]methanol. 

Uons behave much like other mineral acids. Concentrated nitric acid Is a strong oxidizing agent. Most metals dissolve to form nitrates but with the evolution of nitrogen oxides. Concentrated nitric acid also reacts with several nonmetals to j ve the oxo acid or oxide. Nitric acid Is generally stored in dark brown bottles because of the photolytic decomposi-tton to dinltrogen tetroxlde. See also nitration. 

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