Complete reversal in regioselectivity in the Baeyer-Villiger reaction of an alpha-CF(3)-ketone and theoretical rationale for axial orientation of sterically demanding CF(3) group at the transition state

The regioselectivity of the Baeyer-Villiger reaction of alpha-CF(3)-ketone is completely reversed from that in alpha-F(eq)-ketone. Theoretical study rationalized that the reaction proceeds with the sterically demanding CF(3) group in an axial orientation by strong dipole interaction. The guiding principle that strong dipole interaction can overcome steric repulsion as a determining factor not only in regio- but also in stereocontrol is proposed. [reaction: see text]     

Manganese-catalyzed benzene synthesis by [2+2+2] coupling of 1,3-dicarbonyl compound and terminal acetylene

Treatment of a mixture of a 1,3-dicarbonyl compound such as a beta-ketoester or 1,3-ketone and a terminal acetylene with a catalytic amount of MnBr(CO)5 in heated toluene produces a benzene derivative by a [2+2+2] coupling reaction incorporating the enol part of the dicarbonyl compound and two moles of the acetylene. When the reaction was carried out using phenylacetylene derivatives, the reaction was completely regioselective, producing p-terphenyl compounds in good to excellent yield. Aliphatic terminal acetylenes also reacted readily but gave a mixture of regioisomers. The reaction features high atom economy, neutral conditions, and functional group tolerance, and will be useful for materials-oriented studies.     

A short convergent synthesis of the side chains of brassinolide,cathasterone, and cryptolide

A new approach to steroidal derivatives of the campestane series, containing the 22α-hydroxy-, 22α,23α-dihydroxy-, and 22α-hydroxy-23-ketone moieties characteristic of brassinolide and its congeners, has been developed. The key step is the coupling of a steroidal C-22 aldehyde with an anion derived from a specially synthesized thioacetal-containing chiral synthon. The cathasterone and cryptolide side chains are prepared by reductive or hydrolytic thioketal removal, respectively. The brassinolide side chain is obtained by DIBAL-H reduction of the TBS-protected 22α-hydroxy-23-ketone.     

几种姜黄素类1,4-戊二烯-3-酮衍生物的合成及结构表征

以芳香醛和酮为原料,合成了3类姜黄素类1,5-二芳基-1,4-戊二烯-3-酮衍生物:1,5-二噻吩基-1,4-戊二烯-3-酮(Ⅰ)、1,5-二苯基-1,4-戊二烯-3-酮类(Ⅱ)和1,5-二呋喃基-1,4-戊二烯-3-酮(Ⅲ);利用元素分析、红外光谱、核磁共振谱(1 H NMR及13 C NMR)分析了产物的组成和结构,初步探讨了其反应条件和反应机理.结果表明,以无水乙醇为溶剂、8%的NaOH溶液为催化剂,反应温度为30⁵0℃时,反应产率较高.     

Dipole interaction-controlled stereoselectivity in aldol reaction of alpha-CF3 enolate with fluoral

The stereoselectivity of a reaction is generally determined by minimizing steric repulsion. However, the aldol reaction of alpha-CF(3)-ketone (Z)-enolate with fluoral anomalously gave an anti-aldol through a sterically demanding transition state, because of the strong dipole interaction of the two CF(3) groups. We have thus disclosed a paradigm shift from steric to electronic control of reaction stereoselectivity. [reaction: see text]     

1-甲基-3,4-二苯基喹啉-2(1H)-酮的合成和结构表征

以N-甲基苯胺和苯丙炔酸为原料,经过缩合、亲电环化、偶联反应合成了1-甲基-3,4-二苯基喹啉-2(1H)-酮;利用核磁共振谱和气相色谱-质谱表征了产物的结构.结果表明,所用合成方法具有产率高、反应条件温和、操作简单等优点,目标产物的总产率达62.7%.     

对映-贝壳杉烯二萜分子内氢键对6, 7位羟基化学反应性影响研究

对映-贝壳杉烯二萜分子在激烈条件下进行乙酰化反应, 反应发生在半缩醛羟基, 而非仲羟基上; 该反常现象的生产可能是由于6位仲羟基与15位羰基之间形成了分子内氢键, 本文根据^1H NMR变温实验观察分子在不同温度时6位和7位羟基质子的化学位移变化值△δ/T(Hz.K^-^1), 证明了上述假定。     

萘并吡喃的合成工艺改进及其光致变色性能

4,4′-二甲氧基二苯甲酮与乙炔钠经亲核加成反应制得1,1-二（4-甲氧基苯基）-2-丙炔-1-醇(2);以4,4′-二甲基二苯甲酮为原料,经3步反应制得中间体5-羟基-3,9-二甲基-苯并芴-7-酮（6）; 6与2经脱水反应合成了萘并吡喃（7）,总收率16.3％,其结构经¹H NMR和IR确证。采用UV-Vis研究了7的光致变色性能。结果表明：7的二甲基亚砜溶液（1.0×10^-4 mol·L^-1）在可见光区呈无色,经过254 nm紫外光照射后呈蓝色,停止紫外光照射一段时间后溶液变回无色。随着光照时间的延长,吸光度呈上升趋势;反复进行紫外光的照射,吸光度变化不明显,表明7具有良好的抗疲劳性。     

Synthesis of [3,4-(13)c(2)]-enriched bile salts as NMR probes of protein-ligand interactions

Synthetic methodology that allows for incorporation of isotopic carbon at the C-3 and C-4 positions of bile salts is reported. Three [3,4-(13)C(2)]-enriched bile salts were synthesized from either deoxycholic or lithocholic acid. The steroid 3alpha-OH group was oxidized and the A-ring was converted into the Delta(4)-3-ketone. The C-24 carboxylic acid was next converted into the carbonate group and selectively reduced to the alcohol in the presence of the A-ring enone. Following protection of the 24-OH group, the Delta(4)-3-ketone was converted into the A-ring enol lactone. Condensation of the enol lactone with [1,2-(13)C(2)]-enriched acetyl chloride and subsequent Robinson annulation afforded a [3,4-(13)C(2)]-enriched Delta(4)-3-ketone that was subsequently converted back into a 3alpha-hydroxy-5beta-reduced bile steroid. C-7 hydroxylation, when necessary, was achieved via conversion of the Delta(4)-3-ketone into the corresponding Delta(4,6)-dien-3-one, epoxidation of the Delta(6)-double bond, and hydrogenolysis/hydrogenation of the 5,6-epoxy enone system. The [3,4-(13)C(2)]-enriched bile salts were subsequently complexed to human ileal bile acid binding protein (I-BABP), and (1)H-(13)C HSQC spectra were recorded to show the utility of the compounds for investigating the interactions of bile acids with I-BABP.     

A concise total synthesis of (-)-cylindricine C through a stereoselective intramolecular aza-[3 + 3] annulation strategy

[reaction: see text] An enantioselective total synthesis of (-)-cylindricine C is described, featuring a diastereoselective intramolecular aza-[3 + 3] annulation strategy and an interesting halohydrin formation of the C4-5 olefin for construction of C4-ketone. This work provides a unique approach to this family of natural products.     

GC-MS Derivatization Studies: The Formation of Dexamethasone MO-TMS

Abstract

The 16α-methyl group in dexamethasone increases drastically the steric hindrance to reaction of both the 20-ketone and 17α-hydroxyl groups, as shown by kinetic studies with GC-MS techniques. A procedure is described for the preparation of the MO derivative (reaction et 60[ddot]C for 3 hr) and complete conversion of all hydroxyl groups to TMS ether groups (reaction at 100[ddot]C for 6 hr). The resulting MO-TMS derivative is thermostable and suitable for use in GC-MS methods. The procedures usually employed in urinary steroid studies are satisfactory for prednisone and prednisolone.     

Synthesis of (24R)-3β-chloro-7α-bromo-5-hydroxy-5α-stigmastan-6-one and study of its dehydrohalogenation products

Starting from β-cytosterol (1) and going through the intermediate 3β-chloro-5α-hydroxy-6-ketone (2), the 3β-chloro-7α-bromo-5α-hydroxy-6-ketone (3) is synthesized. Dehydrohalogenation of3 in DMF in the presence of lithium carbonate and bromide gives the 6-ketosteroids4–6, depending on the reaction conditions. Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus, 220141, Belarus, Minsk, ul. Akad. Kuprevicha, 5/2. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 617–622, September–October, 1999.     

Terpenoid ring a α-ketol sulphonate ester solvolysis: conversion of ent-3β-hydroxybeyer-15-en-2,12-dione to the isomeric ent-1α-hydroxybeyer-15-en-2,12-dione

Acetolysis of tetracyclic diterpenoid 3-equatorial, 3-axial or 1-axial sulphonate-2-ketones results in attack at the 1-axial position. Jones oxidation of the derived 1-hydroxy-2-ketone results in an unexpected ring contraction-decarboxylation giving a 2-nor-1-ketone.     

海萤荧光素类似物发光反应机理的理论研究

选取海萤类似物6-芳基-2-甲基咪唑[1,2-α]吡嗪-3(7H)酮环的C6位取代物(命名为MIPa~MIPd)进行理论研究. 采用密度泛涵理论B3LYP方法在气相和二甲亚砜(DMSO)及二甘醇二甲醚(DG)两种溶剂中, 对这些类似物在脱去二氧化碳反应过程中所涉及的2个反应路径的反应活化能和产物激发态的荧光寿命进行了计算, 结果表明, 取代吡嗪酮的过氧化四元环在DMSO溶剂中的反应活化能较低, 给电子基团作为取代基时反应更快. 在DMSO溶剂中, 路径Ⅱ的荧光量子效率比路径Ⅰ的高, 但在DG溶剂中, 路径Ⅰ的荧光效率高于路径Ⅱ的荧光效率.     

磺化侧苯基杂萘联苯聚醚酮酮的合成与性能

以4-(3-苯基-4-羟基苯基)-2,3-二氮杂萘-1-酮(DHPZ-P)、 4-(4-羟基苯基)-2,3-二氮杂萘-1-酮(DHPZ)和1,4-二(4'-氟苯甲酰基)苯(BFBB)为原料, 经溶液亲核取代缩聚反应, 通过调节DHPZ-P和DHPZ的比例, 合成了一系列侧苯基杂萘联苯聚醚酮酮(PPEKK-P), 然后以浓硫酸为磺化剂, 制备出一系列磺化侧苯基杂萘联苯聚醚酮酮(SPPEKK-P). 利用傅里叶变换红外光谱(FTIR)和氢核磁共振谱(¹H NMR)对聚合物结构进行表征, 结果表明, 磺酸基团引入到聚合物链的侧苯基上. 采用溶液浇铸法制备SPPEKK-P质子交换膜. SPPEKK-P膜的吸水率、 溶胀率和质子传导率均随离子交换容量(IEC)的增加而增加, 且具有较好的耐氧化性. IEC最高的SPPEKK-P-100膜的质子传导率在95℃能达到7.44×10^-2 S/cm, 且甲醇渗透系数为5.57×10^-8 cm²/s, 阻醇性能优于Nafion117膜.     

13β-乙基-3-甲氧基-甾-1,3,5(10),9(11)-四烯-17β-醇的间氯过氧苯甲酸氧化反应

研究了13β-乙基-3-甲氧基-甾-1,3,5(10),9(11)-四烯-17β-醇与间氯过氧苯甲酸的氧化反应, 得到了9β-羟基-11酮化合物和一个未知化合物9α-过氧甲氧基-11-酮化合物。推测了反应机理, 讨论了未知物的化学结构和构型。     

联二烯丁基硫醚衍生物合成呋喃的反应

本文报道以联二烯丁基硫醚为起始物的呋喃衍生物的合成方法.实验结果表明,β-联二烯丁基硫醚醇在氢化钠的作用下以很高的收率环化生成一个苯硫基离去的呋喃产物,β-联二烯丁基硫醚醛与外加亲核试剂作用后能得到多一个取代的类似呋喃产物,而β-联二烯丁基硫醚酮在P2O5的促进下也能环化生成呋喃衍生物.     

Steroide—XL: 16,17-azido- und 16,17-aminoalkohole des östra-1,3,5(10)-trien-3-methyläthers

The four epimeric azido alcohols of estra-1,3,5(10)-trien-3-methyl ether with nitrogen at C-16 and oxygen at C-17 were prepared by the following reactions: cleavage of the 16α,17α-epoxide 1 with sodium azide affords the 16β,17α-azido alcohol 2a. The analogous reaction of the 16β,17β-epoxide 4 gives the 17α,16β-azido alcohol 5a and the desired 16α,17β-azido alcohol 6a in low yield. 6a is obtained in a smooth reaction by substitution of the 16β,17β-bromohydrine 8 with sodium azide. Sodium borohydride reduction of the 16β-azido-17-ketone 9 yields the 16β,17β-azido alcohol 10a, reduction of 16α-azido-17-ketone 13 with lithium borohydride gives the 16α,17α-azido alcohol 14a. From the azido alcohols the corresponding amino alcohols 3a, 7a, 11a and 15a are prepared with hydrazine hydrate/Raney nickel. The amino alcohols give the acetic anhydride the corresponding acetylamino alcohols. The cis-amino alcohols 11a and 15a react with acetone to the corresponding oxazolidines 12 and 16.     

1,10-邻菲咯啉-5,6-二酮制备反应中副产物的形成与控制

由1,10-邻菲咯啉合成1,10-邻菲咯啉-5,6-二酮反应的副产物的形成与控制研究表明,1,10-邻菲咯啉在5,6位二酮化反应中的副反应产物及主产物分离时产生的副产物均为4,5-二氮杂芴-9-酮,二酮化反应条件(包括作为氧化剂的强混合酸H2SO4/HNO3的加入量、时间和温度)和主产物分离时体系的酸度对副产物的形成有重要影响,优化了二酮化反应条件和产物分离时的体系pH控制范围。在此优化条件下,可有效控制副产物的形成,使主产物1,10-邻菲咯啉-5,6-二酮的收率达到92%以上。     

Cyano-1 ceto-3 et -4 L-rhamnoses

Oxidation of 1-cyano L-rhamnose and 1-cyano 2-deoxy L-arabino 1-hexenopyranose with DMSO-(COCl)₂ or active MnO₂ gives the corresponding 3-ketone, 4-ketone or γ-pyrones.