• Bulletin of the Korean Chemical Society
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• v.24 no.11
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• pp.1641-1648
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• 2003

New and facile synthetic routes for preparation of optically active norephedrine, norpseudoephedrine and cathinone with high optical purities via double asymmetric induction by employing asymmetric reduction of 2-N-protected amino (or azido)-1-phenylpropanone and 2-methanesulfonyloxy-1-phenylpropanone with CBS-catalyzed-borane and $^dIpc_2BCl$ as chiral reducing agents are described.

• Bulletin of the Korean Chemical Society
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• v.22 no.5
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• pp.443-444
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• 2001

• Bulletin of the Korean Chemical Society
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• v.25 no.5
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• pp.747-750
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• 2004

• Bulletin of the Korean Chemical Society
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• v.8 no.3
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• pp.211-214
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• 1987

Asymmetric reduction of a series of aliphatic ketones and representative other classes of ketones with potassium 9-O-isopinocampheyloxy-9-boratabicyclo[3.3.1]non ane (K 9-O-Ipc-9-BBNH) was studied. All the ketones examined were reduced smoothly to the corresponding alcohols in THF at -$78^{\circ}C$. Thus, the reduction of 2-butanone, 3-methyl-2-butanone, 3,3-dimethyl-2-butanone, 2-octanone, and 4-phenyl-2-butanone provides 51% ee, 61% ee, 44% ee, 35% ee, and 33% ee of optical inductions, respectively. The reduction of other classes of ketones gave 52% ee for 2,2-dimethylcyclopentanone, 47% ee for acetophenone, 23% ee for 3-acetylpyridine, 50% ee for methyl benzoylformate, 4.8% ee for 2-chloroacetophenone, 30% ee for trans-4-phenyl-3-butene-2-one, and 2% ee for 4-phenyl-3-butyn-2-one. Thus, the reagent was found to be most useful in the asymmetric reduction of acyclic and cyclic aliphatic series of ketones.

• Korean Journal of Mathematics
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• v.17 no.3
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• pp.299-314
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• 2009

We investigate the multiple nontrivial solutions of the asymmetric beam equation $u_{tt}+u_{xxxx}=b_1[{(u + 2)}^+-2]+b_2[{(u + 3)}^+-3]$ with Dirichlet boundary condition and periodic condition on t. We reduce this problem into a two-dimensional problem by using variational reduction method and apply the Mountain Pass theorem to find the nontrivial solutions of the equation.

• Bulletin of the Korean Chemical Society
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• v.22 no.11
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• pp.1261-1263
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• 2001

• Bulletin of the Korean Chemical Society
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• v.15 no.12
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• pp.1080-1084
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• 1994

Asymmetric inducing effects of substituents attached at nitrogen, the 5-position and boron in oxazaborolidine rings on asymmetric borane reduction of ketones were investigated. Thus, the effect of N-substituents examined with the oxazaborolidines prepared from (lR,2S)-N-alkyl norephedrine derivatives showed the remarkable decrease of enantioselectivities of the product alcohols by the variation of the steric size of alkyl groups on nitrogen from Me${\leftrightarro}$n-Bu(${\simeq}$Bn)${\leftrightarro}$ neopentyl${\leftrightarro}$i-Pr, such as 83${\%}$ ee with 5b, 22${\%}$ ee with 5c, 23${\%}$ ee with 5f, 16${\%}$ ee with 5e, and 3${\%}$ ee with 5d for the reduction of acetophenone. The presence of diphenyl groups at the 5-position enhanced the enantioselectivities dramatically. The effect of B-alkyl substituents in the oxazaborolidines derived from (lR,2S)-ephedrine showed that the enantioselectivities of product alcohols decreased gradually when the substituents were changed from hydrogen to steric bulky groups such as methyl, n-butyl, thexyl and phenyl.

• ETRI Journal
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• v.32 no.3
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• pp.447-456
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• 2010

Asymmetric regulation as applied to mobile termination rates refers to regulatory arrangements in which different mobile operators charge different termination rates, even though the services provided are essentially identical. The asymmetric regulation has been frequently used as a regulatory tool to support new entrants to a mobile market. This paper examines the economic effects of asymmetric regulation of mobile termination rates using a theoretical model and its simulation. The result shows that when there is no noticeable difference in brand loyalty between mobile operators with the high degree of substitutability between services provided by mobile operators, and the costs of new entrants are low, a reduction in the asymmetry of mobile access prices results in an enhancement of consumer welfare. These findings provide positive evidence for the argument that in certain situations asymmetric pricing of mobile access services may be counterproductive for consumer welfare.

• Bulletin of the Korean Chemical Society
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• v.12 no.5
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• pp.565-569
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• 1991

Enantioselective synthesis of 1-substituted tetrahydroisoquinoline alkaloids (1) via asymmetric reduction of 1-substituted 3,4-dihydroisoquinolines (2) and the corresponding iminium salts (3) with the selected chiral hydride reagents, such as K glucoride (5), Itsuno's reagent (6), and Mosher's reagent (7) were examined. In these reactions, dihydroisoquinolines were not reduced by the hydride reagents, whereas the iminium salts were easily reduced under the same reaction conditions found in successful reduction of ketones. Thus, the reduction of 6,7-dimethoxy-3,4-dihydroisoquinolium iodide(3a) with 5, 6 and 7 provided the product 1a with 52.3 % ee, 18 % ee, and 66.4 % ee, respectively. For 1-benzyl derivatives (3b-3d), syntheses of 1b-1d with 0.7-6.2 % ee, 5.9-21 % ee, and 1.4-2.7 % ee were achieved with chiral reducing agents 5, 6 and 7, respectively. For 1-aryl derivatives, use of 5, 6 and 7 resulted in optical inductions in the range of 25.2-43 % ee, 13-21.1 % ee, and 6.3-16 % ee, respectively.

• Journal of Magnetics
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• v.18 no.2
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• pp.117-124
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• 2013

Single-phase, brushless DC (BLDC) motors have unequal air-gaps to eliminate the dead-point where the developed torque is zero. Unfortunately, these unequal air-gaps can deteriorate the motor characteristics in the cogging torque. This paper proposes a novel design for a single-phase BLDC motor with an asymmetric notch to solve this problem. In the design method, the asymmetric notches were placed on the stator pole face, which affects the change in permanent magnet shape or the residual flux density of the permanent magnet. Parametric analysis was performed to determine the optimal size and position of the asymmetric notch to reduce the cogging torque. Finite element analysis (FEA) was used to calculate the cogging torque. A more than 28% lower cogging torque compared to the initial model with no notch was achieved.