Methoxyamine, from

The amination of a,a)-dilithiumpolystyrenes was effected using two equivalents of the reagent generated from methyllithium and methoxyamine in a benzene/THF (80/20, v/v) mixture with the results shown in eq. 4. 

Cheney et al. (1995) analyzed steroids by coupling an HPLC purification step with GC/MS. The steroids were initially characterized by their HPLC retention times compared with the retention times of tritium-labeled recovery standards. Next, the nemosteroids were characterized by their GC retention times. Finally, they were identified by their unique fragmentation spectra following derivatization with heptafluorobutyric anhydride or methoxyamine hydrochloride. For structmal identification, the mass spectra were compared to appropriate reference standards. This approach is highly specific, and its sensitivity is increased by the use of SIM. The detection limit for measuring allopregnanolone achieved in the 1995 study was 0.63 pmol (0.2 ng) starting from 100-300 mg of brain tissue. 

An acyclic methoxyamine, 0-methylephedrine 333, plays a similar role in the diastereoselective Uthiation of 334. Substitution with 335 gives 336 from 322, and lithiation of 334 typically gives products 335 with >90 10 diastereoselectivity (Scheme 149) . Auxiliary removal is possible by quaternization and substitution with dimethylamine (giving 336) or other nucleophiles, producing potential ligands with planar chirality only. Usefully, the products formed by this method are enantiomeric with those formed by most other auxiliary methods when the more readily available enantiomers of the starting materials are used. 

Methoxyamine hydrochloride [593-56-6] M 83.5, m 151-152°. Crystd from absolute EtOH or EtOH by addition of ethyl ether. [Kovach et al. JACS 107 7360 1985],... 

Lithium aluminum hydride-Hexa-methylphosphoric triamide, 159 Methoxyamine, 177 Titanium(III) chloride-Diisobutyl-aluminum hydride, 303 Trimethylsilyl chlorochromate, 327 From vinylsilanes m-Chloroperbenzoic acid, 76 Miscellaneous methods to prepare ketones... 

Formation of aldimines from propanal and octanal. To a stirred solution (0°C) of 10 mmol of the methoxyamine dissolved in 30 ml of benzene (CAUTION) (previously washed with concentrated sulphuric acid and distilled) is added 10 mmol of the pure aldehyde. An immediate cloudiness usually results. The mixture is allowed to warm to room temperature and c. 15 g of anhydrous sodium sulphate added. After stirring an additional 30-40 minutes, it is filtered and the sodium sulphate washed thoroughly with dry ether. The solvent is removed first with aspirator pressure and then with a vacuum pump (0.5 mm) to generally furnish 9.5-10 mmol of the aldimine as a colourless oil. The aldimines are dissolved in tetrahydrofuran (0.4 m) and stored at —20 to — 30 °C. Attempts to store the aldimines as neat liquids result in deterioration. The solutions of aldimines are conveniently transferred via a syringe to reaction vessels. 

The chiral methoxyamine is recovered from the aqueous solution by neutralisation with solid potassium hydroxide and extraction with ether. The ethereal extract is washed with brine, dried over potassium carbonate and concentrated to give the crude chiral amine in 80-88 per cent yield. Distillation affords the pure amine (70-75% recovery) with [a] values which indicate that no racemisation has occurred. 

Gas Chromatography-Mass Spectrometry. Prepare methoxime derivatives by heating the extract from the thin-layer chromatographic plate with 100 xl of an 8% solution of methoxyamine hydrochloride in dry pyridine at 60° for 30 minutes, and evaporate in a rotary film evaporator. Silylate by dissolving the residue in 100 Lll of chloroform, adding 100 Lll of A,0-bis(trimethylsilyl)acetamide and 20 Lll of trimethylchlorosilane, then seal, and heat for 2 hours at 60°. When only 5a-estrane-3P,17a-diol is to be confirmed the methoxime formation can be omitted. Prepare a 2-cm column of Sephadex LH-20 in a Pasteur pipette with a cotton wool plug, using a... 

Electrochemistry, as a nonpolluting selective oxidation method, can be used to generate the nitroxyl radical, which initiates cyclization from methoxyamines. The carbon radical formed by cyclization is in turn oxidized to the benzylic carbonium ion, which then undergoes attack by the nucleophilic solvent (water, methanol, acetic acid, or acetonitrile) from the less hindered exo face to afford ultimately, in satisfactory yield, the (i-functionalized cyclic methoxyamine ll49-50. The major byproduct 12 is the result of rearrangement of the intermediate carbonium ion. 

The oxidation of A-alkoxyamines with lead tetraacetate generated aziridines, albeit in low yields (<20%)9 11. Despite the almost complete diastereoselectivity claimed in the preparation of A-methoxyazi ridine 1 from methoxyamine and ( )-2-butene loss of the geometrical purity was observed in the reaction of excess ( )- and (Z)-2-butene with A-(butoxy)aminc in dichloro-methane to give 2n. For this reason a two-step mechanism involving an intermediate N Pb species or nitrenium ion was proposed. However, the completely diastereoselective preparation of both trans- and cis-2 was successively claimed by different authors (GC-MS analysis)49. 

The V-phtha 1 imidt)aziridine prepared, from benzofuran, was cleaved with hot methanol with good regioselectivity and presumed trans stereochemistry to give 10 and 11, although the trans configuration of the methoxyamine was not shown by HNMR25. 

Construct an Eigen plot (see Figure 2, Chapter 6) using Equation (31) and the data of Table 5 for the formation of carbinolamine from 4-methoxybenzaldehyde and methoxyamine catalysed by general acids (AH). ... 

The data for the acid-catalysed formation of carbinolamine from methoxyamine and 4-methoxybenzaldehyde fit the Eigen equation and follow a plot similar to that shown in Figure 20. The parameters are ... 

Polymer-bound chiral hydrazines have been synthesized to furnish a-branched amides (Scheme 12.17) [13, 23], Enantiopure (i-methoxyamines 37 and 38, derived from readily available hydroxyproline and N,N-dibenzylleucinol, respectively, have been attached to solid support and transformed into the corresponding hydrazine auxiliaries 39 and 40 via several steps. The synthesis of a series of enantiomerically enriched a-branched amides required the coupling of aliphatic and aromatic aldehydes to form hydrazones 41 and 42 followed by the addition of different nucleophiles. Cleavage of the N-N bond of the resulting hydrazines 43 and 44 led to a-branched amines 45. Further conversion with benzoyl chloride or acetyl chloride furnished amides 46 in yields of 24—51% and 50-83% ee. 

Methoxyamine CH3O-NH2 54.6 228.4 Derived from AfPi in ref. 1988LIA/BAR... 

N-Homoallyl amides. A-acyl-a-methoxyamines (available from electrochemical methoxylation of amides and carbamates) are conveniently transformed to homo-allyl amines and /3-amino acids by replacement of the methoxy group. 

Chiral imines were prepared from cyclohexane and methoxyamines derived from D-camphor derivatives the imines undergo metalation and alkylation to give 2-alkylcyclohexanones of high enantiomeric... 

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