腈的生物转化不对称合成β-氨基酸和β-氨基酰胺

含有腈水合酶和酰胺水解酶的红球菌Rhodococcus erythropolis AJ270能在非常温和的条件下催化一系列β-氨基苯丙腈衍生物的水解反应, 生成相应的β-氨基酸和β-氨基酰胺. 底物结构对生物转化反应的效率及立体选择性影响很大. 3-氨基-3-苯丙腈的生物水解反应显示了较低的立体选择性, 而氮甲基取代衍生物的水解反应则显示了中等立体选择性, 生成相应S构型β-氨基酸和R构型β-氨基酰胺. 氮上大位阻取代基显著降低生物催化效率.     

Synthesis and Crystal Structure of 3,6-Bis（4,4,4- trifluorobutane- 1,3-dione）-9-n-butylcarbazole

A novel bis（β-diketonate） derivate, 3,6-bis（4,4,4-trifluorobutane-1,3-dione）-9-n- butylcarbazole 1, was synthesized and structurally characterized by single-crystal X-ray diffrac- tion. The crystal belongs to the monoclinic system, space group P2 1/c with a = 10.961（6）, b = 22.942（13）, c = 9.408（6）A, α = 90, β = 109.663（9）, y = 90°, V = 2228（2）A^3, Z = 4, Dc = 1.489 g/cm^3, C24H19F6NO4, Mr = 499.40, F（000） = 1024 and μ = 0.134 mm^-1. The structure was refined to the final R = 0.0699 and wR = 0.1627 for 3744 independent reflections （Rint = 0.1288） and 1349 observed reflections （I 〉 2σ（I））. Compound 1 consists of carbazole unit and two terminal diketonate groups, in which carbazole and its two adjacent diketonate rings are almost coplanar. Moreover, compound 1 was characterized with IR, elemental analysis, IH NMR, MS, electronic absorption, and single-photon fluorescence.     

Use of the Pictet-Spengler reaction for the synthesis of 1,4-disubstituted-1,2,3,4-tetrahydro-β-carbolines and 1,4-disubstituted-β-carbolines: formation of γ-carbolines

Microwave-assisted conjugate addition of indole on nitro-olefins furnished nitro compounds, which were reduced to tryptamines. Further, by using Pictet-Spengler condensation, new 1,4-disubstituted-1,2,3,4-tetrahydro-β-carbolines were synthesized in diastereoselective manner. Dehydrogenation of the tetrahydro-β-carbolines produced new 1,4-disubstituted-β-carbolines. As a new observation, in some of the cases, Pictet-Spengler condensation and dehydrogenation gave two products, namely 1,4-disubstituted-β-carbolines and 1,4-disubstituted-γ-carbolines. A mechanism is proposed for this observation.     

1,2-Acyl group migration in the oxidative free radical reaction of 2-substituted-1,4-quinones

Oxidative free radical reactions of 2-substituted-1,4-quinone derivatives are described. Electrophilic carbon-centered radical produced by the manganese(III) acetate oxidation of α-chloro-β-ketoester undergoes efficient addition to the C-C double bond of 5,6-dimethyl-2-(methylamino)-1,4-benzoquinone, and this reaction provides a novel method for the synthesis of spirolactam 3 and indole-2,4,7-trione 4. It shows high chemoselectivity depending on the migratory aptitude of the substituent on α-chloro-β-ketoester. Imine radical can be generated from the oxidation of β-enamino carbonyl compound with Mn(III) or Ce(IV) salt. With 2-hydroxy-1,4-naphthoquinone, spirolactam 6 was prepared from β-enamino carbonyl compound effectively. TBACN/CHCl₃ is the most effective reaction condition for the formation of 6.     

Aminomethylation of chiral silyl enol ethers: access to β-homotryptophane and β-homolysine derivatives

We describe here the aminomethylation of chiral silyl enol ether derivatives using iminium ion. The choice of judicious precursors with adequate protecting groups for the silylation/aminomethylation step was required to achieve the synthesis of β²-homotryptophane in few steps. The same methodology was used to prepare a β²-homolysine derivative.     

Silica gel accelerated aza-Michael addition of amines to α,β-unsaturated amides

A novel method to synthesize β-amino amide has been developed via conjugated addition of amine to bulky α,β-unsaturated amides promoted by silica gel. The silica gel worked efficiently to accelerate the reaction and afforded the related adduct in good to excellent yield.     

Enantioselective total synthesis of (−)-tetrahydrolipstatin using Oppolzer’s sultam directed aldol reaction

A highly practical and concise stereoselective total synthesis of (−)-tetrahydrolipstatin is achieved using Oppolzer’s sultam directed aldol reaction as the key step.     

A general synthetic approach for the synthesis of β-hydroxy-δ-lactones: asymmetric total synthesis of prelactones and epi-prelactones V and E

A general synthetic approach for the synthesis of prelactones and epi-prelactones V and E has been reported using an Evans’ aldol reaction as the key step.     

自由基环化制备β-内酰胺的理论研究

使用密度泛函方法在UB3LYP/6-311＋＋G(3df, 2p)水平上对自由基环化合成β-内酰胺的四种反应途径进行理论研究. 结合Marcus理论对影响反应的热力学及动力学因素进行分析, 发现氨基甲酰基自由基4-exo环合反应是理想的动力学控制过程; 酰胺自由基的4-exo环合反应与5-endo环合反应相比是动力学有利的转化过程; 单取代的酰胺烷基自由基的4-exo环合反应是一类动力学和热力学都较为不利的反应; 羰基自由基加成亚胺N＝C双键的4-exo环合反应与5-endo环合反应相比动力学不利而热力学有利.     

微量热法研究β-环糊精与6-苄氧基嘌呤和6-苄氨基嘌呤的主－客体相互作用

在298.15K下,用微量热法测定了重要植物生长调节物质6-苄氧基嘌呤(6-BOP)和6-苄氨基嘌呤(6-BAP)与β-环糊精(β-CD)在pH值等于8.9的水溶液中包合作用的热效应,进而用非线性拟合法计算出了主－客体包合物的化学计量比、平衡常数、标准焓变和标准熵变等热力学参数。结合主－客体相互作用的紫外光谱信息,从6-苄氧基嘌呤和6-苄氨基嘌呤的分子结构出发讨论了主-客体分子相互作用的强弱以及热力学数据的差异。结果表明,β-环糊精对6-苄氧基嘌呤和6-苄氨基嘌呤具有明显的分子识别功能。