R-Amino effect

The reaction proceeds according to the principles of the r-amino effect (Scheme 11). A wide range of substituted benzyl derivatives followed this pathway. Debenzylation rather than decyanoethylation occurred—a fact attributable to the stabilization of the iminium cation that occurs in the former process, whereas destabilization would result in the latter. Furthermore, the reaction gave low yields with cation-destabilizing benzyl groups such as nitro- and difluoro-substituted derivatives. In the absence of the para-methyl group, normal para-formylation occurred and the perfluoro-phenylmethyl derivative (27, Ar = QH5) formylated normally in the ortho position. The quinazolinium intermediate 29 was mooted (see type 3 reactions for more information on this reaction). 

Dinitro-r-anilines constitute a major group of pre-emergent herbicides. The photodecomposition of these herbicides has been simulated by studying the photolysis of one typical example, Trifluralin 47 (74MI1). The major product from the action of sunlight in aqueous alkaline media was the benzimidazole 48, and the by-products included the dihyroxybenzimidazo-line 49, the benzimidazole Y-oxide, and benzimidazoline derivatives of 48, all being derived by r-amino-effect chemistry (Scheme 17). 

A remarkable transformation of nitroaniliiies 57 to N-alkyloxybenzimida-zoles 58 under alkylation conditions (NaH/RCH2X) has been shown to proceed by way of Af-alkylation/cyclization/O-alkylation and is thus not a true example of a r-amino-effect process (95SC819, 95T4101) (Scheme 21). 

IV. Type 3 Reactions Foraiation of Rings Containing More Than Six Members from r>Amino-Effect Reactions... 

A chiral catalyst consisting of Irans-RuC]2(xy]binap)(daipen) and (CH3)3COK in 2-propanol effects asymmetric hydrogenation of a-, / -, and y-amino aromatic ketones [128]. Hydrogenation of 2-(dimethylamino)acetophenone catalyzed by the (R)-XylBINAP/(R)-DAIPEN-Ru complex [(R,R)-31D] gives the R amino alcohol in 93% ee (Fig. 32.36). The optical yield is increased up to 99.8%, when... 

Gilron, I., Max, M.B., Lee, G., Booher, S.L., Sang, C.N., Chappell, A.S., and Dionne, R.A., Effects of the 2-amino-3-hydroxy-5-methyl-4-isoxazole-proprionic acid/kainate antagonist LY293558 on spontaneous and evoked postoperative pain, Clin. Pharmacol. Ther., 68, 320, 2000. 

Dean, M. A., A. S. Dhaliwal, and W. R. Jones. Effects of Zingiberaceae rhizome extract of the infectivity of cyanophage LPP-1. Trans 111 State Acad Sci Suppl 1987 80 Abstr 83. Morita, K., M. Hara, and T. Kada. Studies on natural desmutagens screening for vegetable and fruits factors active in inactivation of mutagenic pyrolysis products from amino acids. Agr Biol Chem 1978 42(6) 1235-1238. 

The degree of EDA is governed by the nature of the substituent (R). The effect of R is observed often in opposite directions between amino acid MRNi and hydroxy acid MRNi. For example, the increase in bulkiness of R increases the EDA of amino acid-MRNi but decreases that of hydroxy acid MRNi as shown in Fig. 3 (77, 72). An increase (decrease) in electron density at the chiral center of the modifying reagent increases (decreases) the EDA of amino acid-MRNi and decreases (increases) the EDA of hydroxy acid-MRNi as shown in Table 111 (52a). 

Asymmetric hydrogenation of N-acyl-x-aminocinnamic acids. Rh(I) complexes with either 1 or 2 attached to polymers with suitable swelling characteristics are very effective for asymmetric hydrogenation of dehydroamino acids. Optical yields of about 90% are possible. As expected, polymer-bound Rh(I)-l results in (R)-amino acid derivatives, whereas polymer-bound Rh(I)-2 results in (S)-amino acid derivatives. 

Banaszak, A. T. and Trench, R. K., Effects of ultraviolet (UV) radiation on marine microalgal-invertebrate symbioses. II. The synthesis of mycosporine-like amino acids in response to exposure to UV inAnthopleura elegantissima and Cassiopeiaxamachana, J. Exp. Mar. Biol. Ecol., 194, 233, 1995. 

Chantegrel, B., Deshayes, C., and Laure, R., Tandem Wolff rearrangement- fert-amino effect sequence. Synthesis of 2-oxoindolinium enolate and l//-2-benzopyrane derivatives. Tetrahedron Lett., 36, 7859, 1995. 

Henderson, A. R., The effect of feeding with a tryptophan-free amino acid mixture on rat liver magnesium ion-activated deoxyribonucleic acid-dependent ribonucleic acid polymerase, Biochem. ]., 120[1], 205, 1970. 

Comparing these results with enamide hydrogenation, it is evident that catalysts effecting R amino acid synthesis from enamides direct S-carboxylic acid formation from unsaturated acids. This implies (Scheme 9) that the preferred carboxyl-group configuration is similar in the two series. 

Clark, R.H., Chace, D.H., Spitzer, A.R. (2007) Effects of two different doses of amino acid supplementation on growth and blood amino acid levels in premature neonates admitted to the neonatal intensive care unit a randomized, controlled trial. Pediatrics, 120,1286-1296. 

Takehara, J. Hashiguchi, S. Fujii, A. Inoue, S.-I. Ikariya, T. Noyori, R. Amino alcohol effects on the ruthenium(II)-catalysed asymmetric transfer hydrogenation of ketones in propan-2-ol. Chem. Commun. 1996, 233-234. 

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