微波水解衍生高效液相色谱法测定西洋参中的氨基酸

用微波辅助提取酸水解西洋参中的蛋白质, 对生成的氨基酸进行微波衍生后用高效液相色谱法进行测定.对微波衍生条件和微波水解的条件进行了优化.研究结果表明, 190 ℃, 15 min微波水解得到氨基酸的产率与传统加热水解(110 ℃, 24 h)的结果基本相同.用2,4-二硝基氟苯(DNFB)对氨基酸进行微波衍生, 氨基酸在微波衍生时间大于20 s时, 衍生反应基本完全; 而传统DNFB衍生需在60 ℃水浴加热1 h, 所以微波衍生法明显缩短了氨基酸分析时间.用高效液相色谱法对西洋参根中的氨基酸进行了测定, 结果令人满意.     

固-液相转移催化合成 Ⅳ.α-甲基丝氨酸及其它氨基酸

利用活化了的氨基酸酯,通过烷基化反应合成α-氨基酸是近年来使用的简便方法。特别是以苯甲醛与简单的氨基酸酯反应生成的Schiff碱为底物,用固-液相转移催化烷基化反应合成a-氨基酸,不仅条件温和,而且操作简便,原料易得,选择性好。我们采用上述方法成功地合成了α-甲基     

BPB-Ni(II)-Ala复合物法不对称合成双-α-甲基氨基酸

以2-N-(N’-苄基脯氨酰)-氨基二苯甲酮-镍(II)-丙基酸复合物为手性助剂, 与不同碳链长度的二溴烷烃反应制备 双-α-甲基氨基酸. 其中, BPB-Ni(II)-Ala复合物与1,3-二溴丙烷发生取代-消除反应后生成烯丙基取代复合物中间体, 产率高达90%, 水解生成2-甲基-2-氨基-4-烯-戊酸; 与1,4-二溴丁烷、1,5-二溴戊烷、1,6-二溴己烷可以实现双取代反应, 但所得的主要产物为单取代的BPB-Ni(II)-Ala复合物, 双-α-甲基氨基酸复合物中间体收率分别为38%, 36%, 45%, 经过水解后生成相应的双-α-甲基氨基酸, 分别为2,7-二氨基-2,7-二甲基辛二酸、2,8-二氨基-2,8-二甲基壬二酸、2,9-二氨基-2,9-二甲基癸二酸. 手性助剂2-N-(N’-苄基脯氨酰)-氨基二苯甲酮的回收率可高达95%.     

BPB-Ni(Ⅱ)-Ala复合物法不对称合成双-α-甲基氨基酸

以2-N-(N'-苄基脯氨酰)-氨基二苯甲酮-镍(Ⅱ)-丙基酸复合物为手性助剂,与不同碳链长度的二溴烷烃反应制备双-α-甲基氨基酸.其中,BPB-Ni(Ⅱ)-Ala复合物与1,3-二溴丙烷发生取代-消除反应后生成烯丙基取代复合物中间体,产率高达90%,水解生成2-甲基-2-氨基-4-烯-戊酸;与1,4-二溴丁烷、1,5-二溴戊烷、1,6-二溴己烷可以实现双取代反应,但所得的主要产物为单取代的BPB-Ni(Ⅱ)-Ala复合物,双-α-甲基氨基酸复合物中间体收率分别为38%,36%,45%,经过水解后生成相应的双-α-甲基氨基酸,分别为2,7-二氨基-2,7-二甲基辛二酸、2,8-二氨基-2,8-二甲基壬二酸、2,9-二氨基-2,9-二甲基癸二酸.手性助剂2-N-(N'-苄基脯氨酰)-氨基二苯甲酮的回收率可高达95%.     

氨基酸合成方法研究 IV: 相转移催化下N-氰甲基亚氨酸酯的烷基化反应

研究了在固液相转移催化条件下, N-氰甲基苯甲亚氨酸酯的烷基化反应, 得到烷基化产物C-烷基化的亚氨酸酯, 烷基化产品不需进一步纯化就可水解得到α-氨基酸, 利用这一方法合成了十个α-氨基酸.     

固-液相转移催化合成——Ⅲ.α-甲基苯丙氨酸的合成及苄基化反应的研究

本文以丙氨酸甲酯和苯甲醛生成的西佛碱衍生物(1)为底物,进行固-液相转移催化苄基化反应,得到的苄基化产物(2)经酸水解合成了α-甲基苯丙氨酸,考察了相转移催化条件下苄基化反应的影响因素及动力学行为,该反应具有表面反应的特性及自催化反应的动力学特征,提出了固-液相转移催化反应的可能机理。     

L-α-三氟乙酰基氧基丙酰基氯对外消旋胺及氨基酸的气相色谱拆分

L-乳酸与三氟乙酸酐反应, 生成L-α-三氟乙酰氧基乳酸, 再与二氯亚砜作用, 合成新的手性试剂----L-α-三氟乙酰氧基丙酰氯. 它与DL-α-苯乙胺及三种DL-α-氨基酸反应, 生成相应的非对映异构体酰胺, 在以Carbowax为固定相的毛细管柱上进行气相色谱拆分. 以相应的L-胺及L-氨基酸在相同条件下进行比较, 发现D-异构体的保留时间较短 .     

相转移催化不对称合成(Ⅰ)——相转移催化反应合成光学活性α-氨基酸

在固液两相条件下用手性季铵盐为相转移催化剂,邻苯二甲酰亚胺钾与α-溴代羧酸酯反应,合成了十二个具有光学活性的α-(邻苯二甲酰亚胺基)羧酸酯,经肼解和水解,得到相应的光学活性α-氨基酸,光学纯度百分率为3.6—17.8％。     

N-二异丙氧磷酰化氨基酸的合成

以亚磷酸二异丙酯为磷酰化试剂、次氯酸钠为氯代试剂首次对20种常见的α-氨基酸进行了磷酰化.通过添加适量四丁基溴化铵为相转移催化剂,使用过量的亚磷酸二异丙酯以补偿其在强碱环境中的水解,从而提高了反应产率.所得产物经核磁共振谱、红外光谱和质谱鉴定结构并分析总结了该类化合物的谱图特征规律.     

微波技术在烟草游离态及蛋白质结合态氨基酸分析中的应用研究

研究了微波萃取烟草中游离氨基酸和微波水解烟草蛋白质的样品前处理方法,对微波萃取和微波水解条件进行了优化。微波萃取后的游离氨基酸及微波水解后的氨基酸总量采用氨基酸分析仪测定,蛋白质中的氨基酸用差减法计算。微波萃取氨基酸的最佳条件为:盐酸浓度0.05 mol·L-1,物料比1∶20,微波萃取温度50℃,微波萃取时间10 min,该条件下得到的游离氨基酸萃取率与超声30 min的结果基本一致;微波水解蛋白质的最佳条件为:盐酸浓度6 mol·L-1,物料比1∶100,水解温度140℃,水解时间60 min,与传统水解24 h的结果基本一致。用微波辅助法萃取烟草中的游离氨基酸及水解烟草蛋白质,样品前处理时间大大缩短,分析结果令人满意。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.