Triterpene glycosides ofHedera helix I. The structures of glycosides L-1, L-2a,L-2b,L-3, L-4a,L-4b,L-6a,L-6b,L-6c,L-7a,and L7-b from the leaves of common ivy

The leaves of common ivy have yielded 11 triterpene glycosides: the 3-O-α-L-pyranosides of oleanolic acid (1), of echinocystic acid (2), and of hederagenin; the 3-O-[O-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranoside]s of oleanolic acid (4), of echinocystic acid (5), and of hederagenin (6); the O-α-L-rhamnopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1→6)-O-β-D-glucopyranosyl ester of hederagenin 3-O-α-L-pyranoside (7); the O-β-D-glucopyranosyl-(1→6)-O-β-D-glucopyranosyl ester of hederagenin 3-O-[O-α-L-pyranosyl-(1→2)-α-L-arabinopyranoside] (9); and the O-α-L-rhamnopyranosyl-(1→4)-O-β-D-glucopyranosyl-(1→6)-O-β-D-glucopyranosyl esters of oleanolic acid, echinocystic acid, and hederagenin 3-O-[O-α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranoside]s (8), (10), and (11), respectively. This is the first time that compounds (1), (2), (5), (7), (9), and (10) have been found in this plant. Simferopol' State University. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 742–746, November–December, 1994.     

Triterpene glycosides ofHedera helix I. The structures of glycosides L-1, L-2a, L-2b, L-3, L-4a, L-4b, L-6a, L-6b, L-6c, L-7a, and L7-b from the leaves of common ivy

The leaves of common ivy have yielded 11 triterpene glycosides: the 3-O--L-pyranosides of oleanolic acid (1), of echinocystic acid (2), and of hederagenin; the 3-O-[O--L-rhamnopyranosyl-(12)--L-arabinopyranoside]s of oleanolic acid (4), of echinocystic acid (5), and of hederagenin (6); the O--L-rhamnopyranosyl-(14)-O--D-glucopyranosyl-(16)-O--D-glucopyranosyl ester of hederagenin 3-O--L-pyranoside (7); the O--D-glucopyranosyl-(16)-O--D-glucopyranosyl ester of hederagenin 3-O-[O--L-pyranosyl-(12)--L-arabinopyranoside] (9); and the O--L-rhamnopyranosyl-(14)-O--D-glucopyranosyl-(16)-O--D-glucopyranosyl esters of oleanolic acid, echinocystic acid, and hederagenin 3-O-[O--L-rhamnopyranosyl-(12)--D-glucopyranoside]s (8), (10), and (11), respectively. This is the first time that compounds (1), (2), (5), (7), (9), and (10) have been found in this plant.Simferopol' State University. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 742–746, November–December, 1994.     

Radiolysis of L- and D-Monosaccharides

The effects of ⁶⁰Co -radiation on D-glucose, L-glucose, D-galactose, L-galactose, D-mannose, and L-mannose were studied. The yields of gaseous radiolysis products were determined. The curves of radical buildup and decay in crystalline samples were obtained. Conclusions on the relative radiation stability of these D- and L-monosaccharides to the action of nonpolarized radiation were drawn.     

Stereoselective synthesis of L-733,060

Enantioselective synthesis of non-peptidic neurokinin NK1 receptor antagonist L-733,060 is described using ring-closing metathesis as a key step, starting from l-phenylglycine.     

酶法合成L-4-甲砜基苯丙氨酸

以4-甲砜基苯丙酮酸和L-天冬氨酸为底物, 利用重组大肠杆菌DM204(pGEX-KG-aspC/BL21)表达的天冬氨酸转氨酶酶法转化得到了L-4-甲砜基苯丙氨酸, 优化得到的酶法最佳转化条件为: 转化温度37 ℃, 反应体系pH=8, 底物4-甲砜基苯丙酮酸质量分数8%, 质量分数0.6%的吐温80和10-4 mol/L Mg2+对酶活有促进作用. 在最佳工艺条件下经过12 h酶促反应, 4-甲砜基苯丙酮酸摩尔转化率达95%. 本研究利用化学生物法制备了L-4-甲砜基苯丙氨酸, 为制备其它天然氨基酸衍生物提供了新思路.     

Enantioselective Synthesis of L- and D-Carboranylalanine

The enantioselective synthesis of L- and D-carboranylalanine is reported. Imides 13 and 14 are treated with titanium tetrachloride, DIEA, and NBS to introduce a bromo functionality in 98:2 ratio at the alpha-center. Azide displacement with TMGA, displacement of the oxazolidinone template with titanium tetrabenzyloxide, and subsequent hydrogenolysis permits L- or D-carboranylalanine to be isolated in high stereoselectivity and 35-40% yields overall.     

Low-temperature thermodynamic properties of L- and DL-valines

Heat capacities C _p(T) of L-valine and DL-valine were measured in the temperature range 6–300 K with an adiabatic calorimeter; thermodynamic functions were calculated based on these measurements. At 298.15 K, the values of heat capacity, C _p; entropy, S _m ⁰ (T) ? S _m ⁰ (0); enthalpy, H _m ⁰ (T) ? H _m ⁰ (0) of L-valine are equal, respectively, to 167.9 ± 0.3 J K^?1 mol^?1; 178.5 ± 0.4 J K^?1 mol^?1; and 27510 ± 60 J mol^?1. For DL-valine, these values are equal, respectively, to 167.3 ± 0.3 J K^?1 mol^?1, 174.4 ± 0.3 J K^?1 mol^?1, and 27000 ± 50 J mol^?1. The difference between the heat capacities of enantiomer and racemate has been calculated and compared with the similar data for serines, cysteines, and phenylglycines.     

Low-temperature heat capacity of L- and DL-phenylglycines

Heat capacity of crystalline L- and DL-phenylglycines was measured in the temperature range from 6 to 305?K. For L-phenylglycine, no anomalies in the C _p (T) dependence were observed. For DL-phenylglycine, however, an anomaly in the temperature range 50?C75?K with a maximum at about 60?K was registered. The enthalpy and the entropy changes corresponding to this anomaly were estimated as 20?J?mol^?1 and 0.33?J?K^?1 mol^?1, respectively. In the temperature range 205?C225?K, an unusually large dispersion of the experimental points and a small change in the slope of the C _p (T) curve were noticed. Thermodynamic functions for L- and DL-phenylglycines in the temperature range 0?C305?K were calculated. At 298.15?K, the values of heat capacity, entropy, and enthalpy are equal to 179.1, 195.3?J?K^?1 mol^?1, and 28590?J?mol^?1 for L-phenylglycine and 177.7, 196.3?J?K^?1 mol^?1 and 28570?J?mol^?1 for DL-phenylglycine. For both L- and DL-phenylglycine, the C _p (T) at very low temperatures does not follow the Debye law C ?C T ³ . The heat capacity C _p (T) is slightly higher for L-phenylglycine, than for the racemic DL-crystal, with the exception of the phase transition region. The difference is smaller than was observed previously for the L-/DL-cysteines, and considerably smaller, than that for L-/DL- serines.     

L-(-)-肉碱的合成

探讨了以手性环氧氯丙烷为原料,对中间体进行重结晶提高光学纯度的方法合成了L-(-)-肉碱,其质量指标符合美国药典USP(24)版的要求：     

Structure of alkaloid L-5 fromColchicum luteum

Chemistry of Natural Compounds - FromColchicum luteum Baker collected in the gorge of the Sazan-Ata River in the Chimkent region have been isolated the known alkaloids colchamine,...     

L-和DL-福多司坦的太赫兹光谱分析

利用太赫兹时域光谱技术(THz-TDS)在室温下对L-福多司坦和DL-福多司坦进行测量,发现L-和DL-福多司坦在THz波段都有特征吸收峰,且两者的吸收谱有明显差异.运用密度泛函理论的B3LYP方法计算了L-和DL-福多司坦在太赫兹波段的吸收谱,并对L-和DL-福多司坦的特征吸收峰进行了指认,理论计算与实验结果基本吻合.此外,还对福多司坦胶囊成品药进行了测量,发现该胶囊的吸收谱与L-福多司坦非常吻合,证明胶囊药的主要成分为L-福多司坦.这项研究对手性物质的检测以及化合物有效成分的鉴别有一定的参考作用.     

Thin layer chromatographic resolution of some 2-arylpropionic acid enantiomers using L-(-)-serine,L-(-)-threonine and a mixture of L-(-)-serine and L-(-)-threonine-impregnated silica gel as stationary phases

Impregnated silica TLC plates with L-(-)-serine and L-(-)-threonine and a mixture of L-(-)-serine and L-(-)-threonine (1:1) as chiral selectors were prepared to use as chiral stationary phases (CSPs) in thin layer chromatography. The resolution of the enantiomers of 2-arylpropionic drugs, including ibuprofen, ibuproxam, ketoprofen, pranoprofen, benoxaprofen, flurbiprofen and tiaprofenic acid was investigated on these CSPs. A mobile phase system of acetonitrile-methanol-water (16:4:0.5, v/v/v) was used. The spots were detected with iodine vapours and the detection limits were found to range between 0.25 and 0.5 micro g/mL for all racemic compounds investigated. The effect of temperature, pH and concentration of the impregnating chiral selectors on resolution has been studied.     

Microbial and Enzymatic Synthesis of Optically Pure D- and L-3-Trimethylsilyl-alanine by Deracemization of D,L-5-Trimethylsilyl-methyl-hydantion

Summary.  The sterospecificities of hydantoinases and N-carbamoyl amino acid amidohydrolases (N-carbamoylases) from different microbial sources were investigated for the stereoselective syntheses of the unnatural silicon-containing amino acids D- and L-3-trimethylsilyl-alanine (3) from the respective racemic hydantoin D,L-1. In a preparative biotransformation, whole resting cells of Agrobacterium sp. IP I 671, immobilized in a Ca-alginate matrix, were used for the synthesis of amino acid D-3 in 88% yield and 95% enantiomeric excess. Since the purified D-N-carbamoylase from Agrobacterium sp. IP I 671 was shown to be 100%D-selective, the enantiomeric purity of 95% of D-3 arising from the transformation with the immobilized cells must be explained by the participation of a further, L-selective N-carbamoylase or, which is more likely, by racemization of the final hydrolysis product by the action of an amino acid racemase. Isolated hydantoinases from Bacillus thermoglucosidasius, Thermus sp., Arthrobacter aurescens DSM 3745, and Arthrobacter crystallopoietes DSM 20117 turned out to be stereospecific for the conversion of the D-form of hydantoin D,L-1. The enantiomerically pure L-form of 3 was also prepared. It was synthesized from racemic N-carbamoyl amino acid D,L-2 by enantiomer-specific hydrolysis of the L-form in presence of L-N-carbamoylase from Arthrobacter aurescens DSM 3747. Received December 20, 1999. Accepted January 7, 2000     

Microbial and Enzymatic Synthesis of Optically Pure D- and L-3-Trimethylsilyl-alanine by Deracemization of D,L-5-Trimethylsilyl-methyl-hydantion

 The sterospecificities of hydantoinases and N-carbamoyl amino acid amidohydrolases (N-carbamoylases) from different microbial sources were investigated for the stereoselective syntheses of the unnatural silicon-containing amino acids D- and L-3-trimethylsilyl-alanine (3) from the respective racemic hydantoin D,L-1. In a preparative biotransformation, whole resting cells of Agrobacterium sp. IP I 671, immobilized in a Ca-alginate matrix, were used for the synthesis of amino acid D-3 in 88% yield and 95% enantiomeric excess. Since the purified D-N-carbamoylase from Agrobacterium sp. IP I 671 was shown to be 100%D-selective, the enantiomeric purity of 95% of D-3 arising from the transformation with the immobilized cells must be explained by the participation of a further, L-selective N-carbamoylase or, which is more likely, by racemization of the final hydrolysis product by the action of an amino acid racemase. Isolated hydantoinases from Bacillus thermoglucosidasius, Thermus sp., Arthrobacter aurescens DSM 3745, and Arthrobacter crystallopoietes DSM 20117 turned out to be stereospecific for the conversion of the D-form of hydantoin D,L-1. The enantiomerically pure L-form of 3 was also prepared. It was synthesized from racemic N-carbamoyl amino acid D,L-2 by enantiomer-specific hydrolysis of the L-form in presence of L-N-carbamoylase from Arthrobacter aurescens DSM 3747.     

合成左旋和右旋丙叉甘油醇的新方法

Salen-CoⅢ;环氧氯丙烷;左旋;右旋;丙叉甘油醇;合成     

L-5-羟基色氨酸粉晶晶体结构解析

以50%甲醇溶液为提取溶剂,从加纳籽中提取L-5-羟基色氨酸(HTP),采用RP-HPLC获得纯度为99.5%样品,经80%甲醇溶液重结晶获得多晶粉末.利用X射线粉末衍射技术结合计算晶体学方法解析其粉晶晶体结构,模拟图谱与实验图谱的Rwp值为5.06%.结果表明:该晶体属单斜晶系,P2_1空间群,晶胞参数为a=13.69927 ±0.01967(A),b=5.34550 ±0.00756(A),c=7.88219±0.01129(A),a=y=90.00000°,β=86.25936±0.00359°,Z=2,V=579.973(A)~3,并在此基础上对其晶体生长特性进行了分析.