Chiral amine catalyzed enantio- and diastereoselective Michael reaction in brine
摘要:
Simple pyrrolidine-based chiral amines were synthesized and used for the Michael addition of different ketones to a variety of nitro-olefins in brine. The effect of different surfactants and acids on the yields and stereochemical outcome of the Michael adducts was studied in detail. Chiral amine 1g was found to catalyze the formation of Michael adducts with high enantioselectivity (up to >99%), diastereoselectivity [up to 98:2 (syn:anti)] and yield (up to 94%). (C) 2012 Elsevier Ltd. All rights reserved.
peptidomimetic human immunodeficiency virus proteaseinhibitorscontaining a unique unnatural amino acid, allophenylnorstatine [Apns; (2S,3S)-3-amino-2-hydroxy-4-phenylbutyric acid], with a hydroxymethylcarbonyl isostere as the active moiety. From a structure-activity relationship study of HIV-1 protease inhibition, enzyme selectivity for other aspartyl proteases, the antiviral activity and pharmacokinetics
Bifunctional N,N‘-dioxide catalysts have been developed for highly enantioselective cyanosilylation of α,α-dialkoxy ketones. This process, catalyzed by in-situ-prepared proline-derived N,N‘-dioxide 2b, produced the corresponding cyanohydrin trimethylsilyl ethers in excellent yields (up to 99%) with high enantioselectivities (up to 93% ee). A reasonable mechanism was proposed according to the observation
双官能N,N- '二氧化物催化剂已经被开发用于α的高度对映选择性的硅氰化反应,α二烷氧基酮。此过程中,通过催化的原位制备的脯氨酸衍生Ñ,Ñ '二氧化物2b中,所产生的相应的氰醇三甲基甲硅烷基醚以优良产率(高达99%)的高对映选择性(高达93%ee)的。根据线性效应,1 H NMR谱图,分离的氰醇以及催化剂的NH和N-氧化物部分的作用,提出了合理的机理。
Amino Acids and Peptides. XVI. Synthesis of N-Terminal Tetrapeptide Analogy of Fibrin .ALPHA.-Chain and Their Inhibitory Effects on Fibrinogen/Thrombin Clotting.
N-Terminal tetrapeptide analogs of fibrin α-chain were synthesized by the solution method using a new active ester, the ester of the oxime of p-nitroacetophenone, and by the solid-phase method. Their inhibitory effects on fibrinogen/thrombin clotting were examined. Of the synthetic peptides, amide analogs of Gly-Pro-Arg-Pro exhibited a more potent inhibitory effect.
bisformamides have been shown to catalyze the asymmetric one-pot, three-component Streckerreaction, which produced the α-amino nitriles in excellent yields (up to 99%) with good enantioselectivities (up to 86% ee). Optically pure products could be obtained after a single recrystallization. A possible transition state (TS1) has been proposed to explain the origin of asymmetric inductivity and reactivity according
C 2对称的手性双甲酰胺已显示出催化不对称的一锅,三组分Strecker反应,该反应以优异的对映体选择性(高达86%ee)以优异的收率(高达99%)产生了α-氨基腈。在单次重结晶后可获得光学纯的产物。根据在B3LYP / 6-31G(d)水平下优化的催化剂2a的几何形状和产物4a的绝对构型,已经提出了一种可能的过渡态(TS 1)来解释不对称感应性和反应性的起源。