Amino Acids phenyl bearing

Tyrosine- and Phenylalanine-Derived Alkaloids Tyrosine and phenylalanine amino acids are bearing the phenyl-ethylamine moiety of many medicinally relevant alkaloids. Further hydroxylations on the aromatic carbocycle or on the aliphatic part can be observed. Methylations can occur on phenolic oxygens and on the amine, leading to catecholamines (adrenaline, noradrenaline, dopamine). Arylethylamines are also usual to react with endogenous aldehydes through Pictet-Spengler reactions [25], leading to important biosynthetic intermediates (Scheme 1.7) like ... 

An approach to the preparation of asymmetrically 1,2-disubstituted 1,2-diamines has been reported the zinc-copper-promoted reductive coupling of two different N-(4-substituted)phenyl aromatic imines, one bearing a 4-methoxy and the other a 4-chloro substituent, in the presence of either boron trifluoride or methyltrichlorosilane, gave a mixture of the three possible 1,2-diamines, where the mixed one predominated [31 ]. Low degrees of asymmetric induction were observed using 1-phenylethylamine, phenylglycinol and its 0-methyl ether, and several a-amino acid esters as the chiral auxiharies meanwhile the homocoupling process was not avoided (M.Shimizu, personal communication). 

Clerici and Porta reported that phenyl, acetyl and methyl radicals add to the Ca atom of the iminium ion, PhN+Me=CHMe, formed in situ by the titanium-catalyzed condensation of /V-methylanilinc with acetaldehyde to give PhNMeCHMePh, PhNMeCHMeAc, and PhNMeCHMe2 in 80% overall yield.83 Recently, Miyabe and co-workers studied the addition of various alkyl radicals to imine derivatives. Alkyl radicals generated from alkyl iodide and triethylborane were added to imine derivatives such as oxime ethers, hydrazones, and nitrones in an aqueous medium.84 The reaction also proceeds on solid support.85 A-sulfonylimines are also effective under such reaction conditions.86 Indium is also effective as the mediator (Eq. 11.49).87 A tandem radical addition-cyclization reaction of oxime ether and hydrazone was also developed (Eq. 11.50).88 Li and co-workers reported the synthesis of a-amino acid derivatives and amines via the addition of simple alkyl halides to imines and enamides mediated by zinc in water (Eq. 11.51).89 The zinc-mediated radical reaction of the hydrazone bearing a chiral camphorsultam provided the corresponding alkylated products with good diastereoselectivities that can be converted into enantiomerically pure a-amino acids (Eq. 11.52).90... 

V,5S)-5-Amino-4-phenyl-2,2-dimethyl-l,3-dioxane and (4i ,5i )-5-amino-(4 -biphenyl)-2,2-dimethyl-1,3-dioxane were synthesized and employed as chiral solvating agents for the ee determination of compounds bearing an acidic proton by means of NMR spectroscopy (99TA323). Based on the rigid conformation of the two amines, they are... 

Nonelectroactive benzene or toluene can be quantitatively converted to electroactive nitroderivatives. The method can be extended to any polarographic-ally inactive but easily nitrated aromatic compounds such as phenols, phenyl-bearing amino acids, and aniline derivatives. Interesting discriminations between similar compounds based on their ability to be nitrated or not can be achieved. Thus, the readily nitrated phenylbarbituric acid (phenobarbital) can be polarographically determined in the presence of a 100-fold excess of diethylbarbituric acid (barbital). The nitration of morphine also provides an excellent route for the polarographic determination of this otherwise practically nonelectroactive alkaloid. 

The benzyne created from 2-(trimethylsilyl)phenyl triflate was used in a highly diastereoselective aryne Diels-Alder reaction with a diene bearing Oppolzer s sultam. This approach to cis-functionalized 1,4-dihydronaphthalenes was reportedly the first aryne Diels-Alder reaction to provide enantioenriched cyclo-adducts. An unusual route to /3-aminoketones involves the treatment of 2-(trimethylsilyl)phenyl triflate with TBAF and an asymmetric vinyldihydropyridone. The resultant aryne Diels-Alder cycloadduct undergoes aromatization/eUmination to create the )V-acyl-/3-aminoketone (eq 13). This method was featured in a multistep synthesis of an unnatural a-amino acid. 

One of the most general and frequently applied indirect methods is the transformation of an organic compound into a nitrocompound. The method is applied to hydrocarbons and other aromatic compounds, mainly those bearing a phenyl ring, e.g. phenols, substituted anilines, phenyl-bearing amino acids etc. The nitrating mixture consists of nitric acid, either pure or... 

Great interest has been devoted to the phenyl-bearing natural amino acids, tyrosine, tryptophane and phenylalanineAfter a detailed study of the conditions of nitration, nitration tvith 0-15 N HNOj was recommended for tyrosine, l-5to3 ONHNOa... 

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