Table 1. The Effect of the Reactant Ratio upon the Product Yield in the Reaction of Val-NCA with Toluene
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 run		NCA		AlCl3		toluene		yield		T
 no.		(mmol)		(mmol)		(mmol)		(%)		(0C)
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  1		20		43		470		54		23
  2		20		20		470		25
  3		112		247		560		57		24
  4		51		151		253		56		23
  5		20		61		100		65		23
  6		20		62		100		69		18
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The reaction was normally carried out follows. To a suspension of Val-NCA (20 mmol) in toluene (9.2 g, ca. 11 ml, 100 mmol) was added 2-3 equiv of solid AlCl3 (8.0 g, 60 mmol) carefully, keeping the temperature under 10C. After all of AlCl3 was added over a period of 0.5-1.0 h, the mixture was kept stirring at room temperature for 4-5 h. The reaction mixture was not homogeneous at the first stage, but at the end of the reaction it had became a dark brown, homogeneous oil. Then the mixture was treated with ice and dilute HCl, and the organic phase and/or a solid, if there was one, were separated. The aqueous layer was concentrated as much as possible by means of a rotary evaporator to give a solid residue, which was filtered and dried. The solid was dissolved in a small amount of water and neutralized with an aqueous 1 N Na2CO3 solution. Ether or CH2Cl2 extraction of the neutral or slightly basic solution and evaporation of the solvent left a pale yellow oil which was almost chemically as well as optically pure alpha-aminoalkyl aryl ketone. Reverse addition (run 6), that is, the addition of Val-NCA to a mixture of AlCl3 and toluene, gave a result similar to that of run 5.
Unlike the reaction of Val-NCA with toluene, the reaction of Leu-NCA with toluene gave a mixture of 2-amino-4-methyl-1-(p-methylphenyl)-1-pentanone (4) (more than 97%) and the ortho-substituted product (less than 3%) as determined by 1H NMR analysis. In the case of Ala-NCA, it is possible that the product, obtained in 12.5% yield, was also a mixture of ortho- and para-isomers.
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In the reaction of Val-, Ile-, and Phe-NCA with toluene, only para-substituted products 2,3, and 5 were obtained.
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This alpha-aminoacylation was applied to the other alkylbenzenes. o-, m- and p-xylene and mesitylene also reacted with Val-NCA to form the expected products 6-9, respectively.
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Table 2. Preparation of alpha-Aminoalkyl Aryl Ketones, F-B 2-9.
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product		yield (%)		T (0C)			ee (%)
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  2		54.4			23			98
  2		69.1			18			
  3		55.4			17			65 (96)
  4		74.8			18			- (96)
  5		64.9			29			95
  6		52.5			28			96
  6		62.1			23			
  7		55.0			27			94
  8		17.7			26
  9		79.2			21			98
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Experimental Section. (Partially)

(S)-2-Amino-3-methyl-1-(p-methylphenyl)-1-butanone (2).
To a cooled mixture of AlCl3 (8.3 g, 62 mmol) and toluene (9.5 g, 100 mmol) was added Val-NCA (2.91 g, 20.3 mmol) portion by portion over a period of 1 h at under 10C. The reaction mixture was kept stirring at room temperature for 5 h and then added onto ice (100 g). A white solid (0.97 g), designated as A, was isolated and washed with 40 ml of ether. The aqueous solution was concentrated to about 15 ml. A white solid (4.15 g), designated as B, was separated, and was filtered and washed with 40 ml of ether. A portion af solid B (2.28 g) was dissolved in H2O (10 ml) and ether (40 ml), and then an aqueous 1 N NaHCO3 solution (8 ml) was added. Extraction with ether (40 ml x 2) gave 0.43 g (2.27 mmol) of a yellow solid. Then 5 ml of an aqueous 1 N NaHCO3 solution was added to the above aqueous solution. A second extraction afforded 0.72 g (3.76 mmol) of a yellow solid, and the third one afforded 29 mg. The total amount of 2 obtained was 1.18 g (6.17 mmol, yield 69.1%, 99% ee).

(S)-2-Amino-3-methyl-1-(p-methylphenyl)-1-pentanone (3).
To a cooled mixture of Ile-NCA (3.23 g, 20.5 mmol) and toluene (9.8 g, 110 mmol) was added AlCl3 (8.0 g, 60 mmol) portionwise over a period of 1 h at 10C. Solids A and B were obtained in amounts of 2.11 and 2.83 g, respectively. The workup used for 2 gave 3 (55.4% yield, 65% ee).
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