Chiral separation, determination of absolute configuration, and high-performance liquid chromatography detection of enantiomeric 3-hydroxyhexadecanoyl-CoA

The enoyl-coenzyme A (CoA) hydratase catalyzes the hydration of 2-enoyl-CoA to yield 3-hydroxyacyl-CoA in mitochondrial and peroxisomal β-oxidation. However, the stereospecificities of these hydratases differ from each other. To provide clear evidence of the stereospecificities of hydratases, the absolute configuration of 3-hydroxyhexadecanoyl-CoAs was determined, and they were subjected to a high-performance liquid chromatography (HPLC) using a chiral separation column. The retention time of 3(R)-hydroxyhexadecanoyl-CoA was shorter than that of 3(S)-hydroxyhexadecanoyl-CoA. The HPLC analysis carried out using a chiral separation column is considered to be useful for the study of enoyl-CoA hydratase.     

Spectrophotometric assay of 2,4-dienoyl coenzyme a reductase with 5-phenyl-2,4-pentadienoyl-coenzyme a as substrate

The spectrophotometric assay of 2,4-dienoyl coenzyme A (CoA) reductase (EC 1.1.1.34) was modified to improve the linearity and sensitivity of this method. 5-Phenyl-2,4-pentadienoyl-CoA, which has an absorbance maximum at 340 nm with an extinction coefficient of 44,300 M⁻¹ cm⁻¹, was synthesized and used as substrate. This compound is reduced by nicotinamide adenine dinucleotide phosphate (NADPH)-dependent 2,4-dienoyl-CoA reductase to 5-phenyl-3-pentenoyl-CoA. When a tissue homogenate serves as an enzyme source, the product is further metabolized by Δ³Δ²-enoyl-CoA isomerase (EC 5.3.3.8) to 5-phenyl-2-pentenoyl-CoA, which is hydrated to 5-phenyl-3-hydroxypentanoyl-CoA by enoyl-CoA hydratase (EC 4.2.1.17). The modified assay method, which measures the decrease in absorbance at 340 nm due to the reduction of 5-phenyl-2,4-pentadienoyl-CoA and the oxidation of NADPH, is linear for a longer period of time and is twice as sensitive as the conventional assay with 2,4-decadienoyl-CoA as substrate.     

Sex Pheromone Communication in Two Sympatric Neotropical Stink Bug Species Chinavia ubica and Chinavia impicticornis

Chinavia and Nezara spp. stink bugs (Heteroptera: Pentatomidae) include over100 species, with highest diversity in Afrotropical and Neotropical regions. Species thus far studied in these genera utilize trans-(Z)-(4?S)-bisabolene epoxide (BE) and cis-(Z)-(4?S)-BE as major sex pheromone components, with species specificity ensured by different ratios of the two compounds. Gas chromatography (GC) and coupled GC-mass spectrometry (GC-MS) analyses of a volatiles from C. ubica males revealed the presence of two BE isomers in approximately a 90:10 ratio, which were shown by microprobe (1)?H NMR to be cis-(Z)-BE and trans-(Z)-BE isomers, respectively. Analyses of volatiles from C. impicticornis males suggested the presence of a single isomer, trans-(Z)-BE, in high purity (>90 %). The absolute configurations of the isomers produced by C. ubica and C. impicticornis were determined using chiral GC analysis (β-DEX column). Oxidative microchemistry of synthetic standards of cis-(Z)-(4?S)-BE and trans-(Z)-(4R)-BE, and volatiles from male of C. ubica, revealed the absolute stereochemistry of the cis-(Z)-BE to be (1R,2?S,4?S) [cis-(Z)-(4?S) for short]. Similarly, analyses of trans-(Z)-(4?S)-BE and cis-(Z)-(4R)-BE standards, and volatiles from males of C. ubica and C. impicticornis, revealed the absolute stereochemistry of the trans-(Z)-BE to be (1?S,2R,4?S) [trans-(Z)-(4 S) for short]. Olfactometer bioassays with synthetic BEs confirmed attraction of female C. ubica and C. impicticornis to conspecific synthetic pheromone, but not to heterospecific synthetic pheromone. Chinavia impicticornis appeared not to discriminate behaviorally between the conspecific pheromone and its enantiomer. Coupled GC-electroantennography with antennae from females suggested that C. ubica and C. impicticornis possess olfactory receptors for both cis-(Z)-(4?S)-BE and trans-(Z)-(4?S)-BE. The results in this study confirm that C. ubica and C. impicticornis, as for other Chinavia and Nezara spp., utilize cis-(Z)-(4?S)-BE and trans-(Z)-(4?S)-BE as sex pheromone components, with different ratios guaranteeing species specificity. Furthermore, the results suggest that the absolute stereochemistry of BEs may be less important for conspecific recognition than the relative stereochemistry between the epoxide group and the alkyl substituent on the bisabolene ring.     

Partialsynthesen von Cardenoliden und Cardenolid-Analogen. VI. (20R)- und (20S)-Cardanolide

Partial Syntheses of Cardenolides and Cardenolide Analogues. VI. (20R)- and (20S)-Cardanolides (20R)-Dihydrodigitoxigenin ( 2 ) and (20S)-dihydrodigitoxigenin ( 4 ) as well as their 3-acetates 3 and 5 , respectively, were synthesized by catalytic hydrogenation of the appropriate cardenolides and separation by column chromatography on silica of the mixtures of stereoisomers. Hydroxymethylation of 3 and 5 followed by selective elimination yielded (20S)- and (20R)-14-hydroxy-22-methylene-5β,14β-cardanolide 3-acetate ( 10 and 16 ), respectively. The biological activities of the synthesized 20-stereoisomeric cardanolides are investigated and discussed. Cardanolides 10 and 16 have a strong inhibitory activity on the proliferation of Ehrlich ascites carcinoma cells in suspension culture.     

Isomerization of the double bonds of a conjugated fatty acid during β-oxidation

The β-oxidation of an unsaturated fatty acid containing conjugated double bonds at odd-numbered carbon atoms has not previously been studied. It is, therefore, not clear whether, during the β-oxidation of such an acid, the double bonds will be isomerized by enoyl-CoA isomerase (Δ³-Δ²-enoyl-CoA isomerase) with the loss or retention of its conjugated nature. To investigate the problem, (E,E)-3,5-octadienoyl-CoA was synthesized for use as a model substrate, and enoyl-CoA isomerase was partially purified from bovine liver. The isomerization was followed by spectrophotometric and gas liquid chromatographic methods, and the results suggested that the isomerization of the model substrate proceeded with retention of a conjugated double bond system. It is, therefore, proposed that the β-oxidation intermediate of α-eleostearic acid (Δ^9,11,13 fatty acid) will also isomerize with retention of the conjugated double bond system. Part of doctoral thesis submitted to University of Pretoria, Pretoria, 0001, Republic of South Africa.     

具有光学活性的环丙烷-1,2-二羧酸衍生物的合成

以光学纯的(1R,3R)-trans-蒈醛酸乙酯为起始原料,经氧化银氧化为环丙烷二羧酸单乙酯后与乙醇进行酯化反应,可得到(1R,2R)-trans-3,3-二甲基-1,2-环丙烷二羧酸二乙酯,并很好地保持了其光学纯度。将环丙烷二羧酸单乙酯在碱性条件下水解为具有光学活性的环丙烷二羧酸后,与SOCl2反应得到了具有光学活性的(1R,2R)-trans-3,3-二甲基-1,2-环丙烷二酰氯。研究了氢氧化钠用量、反应温度对产物产率和光学纯度的影响。     

毛杜仲藤中神经酰胺类化合物的分离与结构鉴定

用硅胶,重结晶等手段进行分离纯化,根据化合物的理化性质和光谱数据鉴定结构,来研究毛杜仲藤的化学成分.结果分离得到一个神经酰胺类混合物(化合物1-4),即N-(2'-羟基二十一碳酰基)-1,3,4-三羟基-2-氨基-△8,9(E)-十八碳烯,N-(2'-羟基二十二碳酰基)-1,3,4-三羟基-2-氨基-△8,9(E)-十...     

Chiral Synthesis of (Z)-3-cis-6,7-cis-9, 10-Diepoxyhenicosenes, Sex Pheromone Components of the Satin Moth, Leucoma salicis

All four isomers of (Z)-3-cis-6,7-cis-9,10-diepoxyhenicosenes, 1-4, have been synthesized using D-xylose as the chirally pure starting material. D-Xylose was first converted to 2-deoxy-4,5-O-isopropylidene-3-t-butyldimethylsilyl-D-threopentose 11, via several steps of selective protection, dehydroxylation, and deprotection. Wittig coupling of 11 with nonyltriphenylphosphonium bromide followed by hydrogenation and acid catalyzed deprotection of hydroxyl groups yielded the chiral (2R,3R)-1,2,3-triol, 14, which was used as the precursor for the C-8 to C-21 unit of the (Z)-3-cis-6,7-cis-9,10-diepoxyhenicosenes. Selective tosylation of 14 followed by stereospecific cyclization yielded (2R,3R)-1,2-epoxytetradecan-3-ol, 16, which was then divergently converted to the t-butyldimethylsilyl ether 17 and tosylate 22, respectively. Establishment of the C-5 through C-7 unit of the target molecules was accomplished via regiospecific coupling of 17 with 1-t-butyldimethylsiloxy-2-propyne to form 18. Stepwise transformation of 18 via the formation of tosylate 19, desilylation, and stereospecific cyclization to form epoxy alcohol 20, followed by P2-Ni reduction yielded a key intermediate, allylic epoxy alcohol (Z)-2-(5S,6R)-cis-5,6-epoxyheptadecen-1-ol, 21. Similarly, the coupling of 22 with 1-t-butyldimethylsiloxy-2-propyne yielded 23, which was stereospecifically cyclized to form 24. Desilylation and P2-Ni reduction of 24 gave the antipodal intermediate, (Z)-2-(5R,6S)-cis-5,6-epoxyheptadecen-1-ol, 26. Asymmetric epoxidation of antipodes 21 and 26 with (L)- or (D)-diethyl tartrates resulted in the formation of diepoxy alcohols 27 and 29 from 21, and 33 and 31 from 26, respectively. Tosylation of these diepoxy alcohols followed by coupling with lithium dibutenyl cuprate yielded the four stereoisomers of (Z)-3-cis-6,7-cis-9,10-diepoxyhenicosenes, 1-4. Analysis of the retention characteristics of these materials revealed that one or both of the S*,R*,S*,R* stereoisomers comprise the major pheromone component(s) of Leucoma salicis.     

龙眼核中的神经酰胺和脑苷脂的分离和鉴定

研究龙眼(Dimocarpus longan Lour.)果核的化学成分,采用硅胶柱色谱对龙眼果核石油醚提取物和体积分数95%乙醇提取物进行分离,并利用理化性质和光谱数据鉴定化合物的结构。从龙眼果核的提取物中分离得到一组混合神经酰胺(化合物1、2)和一组混合脑苷脂(化合物3～6),结构鉴定为Rel-(3S,4S,5S)-3-[(2'R)-2'-羟基二十二酰胺]-4-羟基-5-[(4″Z)-十四烷-4″-烯]-2,3,4,5-四氢呋喃(1)、Rel-(3S,4S,5S)-3-[(2'R)-2'-羟基二十四酰胺]-4-羟基-5-[(4″Z)-十四烷-4″-烯]-2,3,4,5-四氢呋喃(2)、1-O-(β-D-吡喃葡萄糖基)-(2S,3S,4R,8E)-2-(2'-羟基二十四酰胺)-8-十八烯-1,3,4-三醇(3)、1-O-(β-D-吡喃葡萄糖基)-(2S,3S,4R,8Z)-2-(2'-羟基二十四酰胺)-8-十八烯-1,3,4-三醇(4)、1-O-(β-D-吡喃葡萄糖基)-(2S,3S,4R,8E)-2-(2'-羟基二十二酰胺)-8-十八烯-1,3,4-三醇(5)、1-O-(β-D-吡喃葡萄糖基)-(2S,3S,4R,8Z)-2-(2'-羟基二十二酰胺)-8-十八烯-1,3,4-三醇(6)。     

(2S,4S)-1-(4-硝基苄氧羰基)-2-[(3-烯丙氧羰基)-苯基氨基甲酰基]-吡咯烷-4-基硫醇的合成工艺改进

采用价格低廉的反-4-羟基-L-脯氨酸为原料,通过7步反应,制备尔他培南的关键中间体———标题化合物,总收率37%。原料来源方便,成本低,而且减少了毒害作用,增加了安全性,适宜于工业化生产。     

硼替佐米中间体的合成及工艺优化

以异丁基硼酸、(1S,2S,3R,5S)-(+)-蒎烷二醇、二氯甲烷、ZnCl2为原料,经过酯化反应、金属化反应、亲核取代反应、水解反应等步骤,完成了硼替佐米中间体[(aR,3aS,4S,6S,7aR)-六氢-3a,8,8-三甲基-α-(2-甲基丙基)-4,6-甲桥-1,3,2-苯并二氧硼烷-2-甲胺2,2,2-三氟乙酸盐]的合成。此方法原料便宜易得、操作简单、产物收率高、后处理方便、适合工业化生产。     

Addition of N,N-Dibromobenzenesulfonamide to Methyl Oleate,Elaidate and trans-2-Hexadecenoate II

Addition of N,N-dibromobenzenesulfonamide (NNDBS) to methyl cis/trans-9-octadecenoales and methyl trans-2-hexadecenoate afforded the corresponding vicinal dibromides, bromohydrins and threo/erythro α-bromo-N-benzenesulfonamide adducts. The isomeric threo/erythro-9(10)-bromo-10(9) - (N-benzenesulfonamido) octadecanoate were inseparable mixtures, while the 2(3)-bromo-3(2)-(N-benzene-sulfonamido) hexadecanoates were separated by column chromatography. The configuration of threo and erythro adducts was established by their conversion to cis-and trans-aziridines. Structures of the products were established by spectral studies.     

The Synthesis and Absolute Configuration of Enantiomeric Pure (R)- and (S)-3-(piperidin-3-yl)-1H-Indole Derivatives

This article describes the synthesis of new chiral 3-(piperidin-3-yl)-1H-indole derivatives (R)-10a-c and (S)-11a-c from the corresponding diastereomers: (3R, 2R) and (3S, 2R)-2-[3-(1H-indol-3-yl)-1-piperidyl]-2-phenyl-acetamides (3R, 2R)-4a, (3R, 2R)-6b, (3R, 2R)-8c and (3S, 2R)-5a, (3S, 2R)-7b, (3S, 2R)-9c. Diastereomers were obtained by N-alkylation of derivatives of racemic 3-(piperidin-3-yl)-1H-indoles 1a-c using (S)-2-(4-toluenesulfonyloxy)-phenylacetic amide (S)–II. The same method was applied to obtain (3R, 2S)-methyl-2-[3-(1H-indole-3-yl)-1-piperidyl]-2-phenylacetate (3R, 2S)-2a and (3S, 2S)-methyl-2-[3-(1H-indole-3-yl)-1-piperidyl]-2-phenylacetate (3S, 2S)-3a diastereomers by treating amine 1a with (R)-2-(4-toluenesulfonyloxy)-phenylacetic acid methylester (R)-I. Systematic studies via single crystal X-ray crystallography were used to determine the molecular structure of the racemates 1a-c and the absolute configuration of the enantiomers. The solid racemates 1b and 1c were “true racemates” crystallizing in a centrosymmetric space group, while 1a formed a racemic conglomerate of homoenantiomeric crystals. The absolute configuration was determined for the enantiomeric pairs (R)-10a/(S)-11a, (R)-10b/(S)-11b, and (R)-12c/(S)-13c, as well as for (3S,2S)-3a. Spectra of ¹H, ¹³CNMR, HPLC, and HRMS for diastereomers and enantiomers were consistent with the determined structures.     

Stereoelective polymerization of β-butyrolactone

Racemic β-butyrolactone was polymerized using chiral initiators obtained from the reaction of organometallic derivatives (ZnEt₂, CdMe₂, AlEt₃) with R(−) 3,3 dimethyl-1,2 butanediol. With the zinc initiator, R(+) enantiomer is preferentially incorporated in the polymer chain with a stereoelectivity ratio r_R equal to 1.6. Crude polymer was fractionated into a crystalline, predominantly isotactic, part and an amorphous heterotactic part, both optically active. Sites of different stereospecificities, present in the initiator, are all active for the stereoelective polymerization. With the cadmium initiator, S(−) enantiomer is preferentially polymerized (r_s = 1.01), extending homosteric-antisteric rules previously established for thiiranes. Aluminium initiator leads to an homosteric process (r_R = 1.1). Chiroptical properties (o.r.d. and c.d.) of polymers prepared with zinc initiator show a predominance of R-configurational units, indicating that ring-opening occurs by O-acyl cleavage with retention of configuration.     

The crotonase superfamily: divergently related enzymes that catalyze different reactions involving acyl coenzyme a thioesters

Synergistic investigations of the reactions catalyzed by several members of an enzyme superfamily provide a more complete understanding of the relationships between structure and function than is possible from focused studies of a single enzyme alone. The crotonase (or enoyl-CoA hydratase) superfamily is such an example whereby members catalyze a wide range of metabolic reactions but share a common structural solution to a mechanistic problem. Some enzymes in the superfamily have been shown to display dehalogenase, hydratase, and isomerase activities. Others have been implicated in carbon-carbon bond formation and cleavage as well as the hydrolysis of thioesters. While seemingly unrelated mechanistically, the common theme in this superfamily is the need to stabilize an enolate anion intermediate derived from an acyl-CoA substrate. This apparently is accomplished by two structurally conserved peptidic NH groups that provide hydrogen bonds to the carbonyl moieties of the acyl-CoA substrates and form an "oxyanion hole".     

Response ofDiabrotica virgifera virgifera,D. v. Zeae,andD. porracea to stereoisomers of 8-methyl-2-decyl propanoate

The four stereoisomers of 8-methyl-2-decyl propanoate were tested in the United States and Mexico for attractiveness toDiabrotica virgifera virgifera LeConte, the western corn rootworm,D. v. zeae Krysan and Smith, the Mexican corn rootworm, andD. porracea Harold. Males ofD. v. virgifera andD. v. zeae responded strongly to the (2R,8R)-isomer and secondarily to (2S,8R), whileD. ponacea responded exclusively to the (2S,8R)-isomer. The (2S,8S)- and (2R,8S)-isomers were inactive in all tests. Synergism or inhibition was not detected when various mixtures of the isomers were tested withD. v. virgifera. These phenomena were not tested withD. v. zeae andD. ponacea.Coleoptera: Chrysomelidae.Mention of a commercial or proprietary product does not constitute an endorsement by the USDA.     

Do rat kidney cortex microsomes possess the enzymatic machinery to desaturate and chain elongate fatty acyl-CoA derivatives?

Rat kidney cortex microsomal preparations were unable to catalyze Δ9, Δ6, and Δ5 desaturation of stearoylcoenzyme A (CoA), linoleoyl-CoA and dihomo-γ-linolenoyl-CoA, respectively. The kidney cortex microsomal fraction, however, did catalyze the malonyl-CoA dependent fatty acyl-CoA elongation. The biochemical properties of palmitoyl-CoA elongation were studied as a function of protein concentration, time, reduced nicotinamide adenine dinucleotide phosphate (NADPH), malonyl-CoA and substrate concentrations; of the substrates investigated, Δ6.9.12–18∶3 was the most active. Unlike what was observed in the hepatic system, a high-carbohydrate, fat-free diet did not induced kidney fatty acid chain elongation. All intermediate kidney cortex microsomal reactions,i.e., β-ketoacyl-CoA reductase, β-hydroxyacyl-CoA dehydrase andtrans-2-enoyl-CoA reductase activities, were significantly higher (greater than one order of magnitude) than the condensing enzyme activity, suggesting that the rate-limiting step in total elongation is the initial condensation reaction. Contrary to other reports, the results suggest that the kidney cannot synthesize arachidonic acid needed for eicosanoid production.     

Stereoselective incorporation of an unsaturated isoleucine analogue into a protein expressed in E. coli

The unsaturated amino acid 2-amino-3-methyl-4-pentenoic acid (E-Ile) was prepared in the form of its (2S,3S),(2R,3R) and (2S,3R),(2R,3S) stereoisomeric pairs. The translational activities of SS-E-Ile and SR-E-Ile were assessed in an E. coli strain rendered auxotrophic for isoleucine. SS-E-Ile was incorporated into the test protein mouse dihydrofolate reductase (mDHFR) in place of isoleucine at a rate of up to 72 %; SR-E-Ile yielded no conclusive evidence for incorporation. ATP/PPi exchange assays indicated that SS-E-Ile was activated by the isoleucyl-tRNA synthetase at a rate comparable to that characteristic of isoleucine; SR-E-Ile was activated approximately 100-times more slowly than SS-E-Ile.     

旋光性N-(2,6-二甲苯基)-N-酰基丙氨酸甲酯类化合物的合成及生物活性研究

以α-氯丙酸、甲醇、2,6-二甲基苯胺为起始原料,合成了N-(2,6-二甲苯基)丙氨酸甲酯。以S(-)-α-甲基苄胺为化学拆分剂,利用非对映异构体在不同溶剂中溶解度的差异,分离得到了R(+)、S(-)-N-(2,6-二甲苯基)-丙氨酸的两个旋光异构体和反-R(+)、反-S(-)、顺-R(+)和顺-S(-)-二氯菊酸的4个旋光异构体。两个N-(2,6-二甲苯基)-丙氨酸旋光异构体与甲醇反应得到两种N-(2,6-二甲苯基)丙氨酸甲酯的旋光异构体。最后N-(2,6-二甲苯基)-丙氨酸甲酯的旋光异构体与二氯菊酰氯的7个异构体进行反应,合成了19个N-(2,6-二甲苯基)-N-酰基丙氨酸甲酯类化合物,其中18个具有旋光性。这些化合物的结构经GC-MS、FTIR测定后确认。对19个标题化合物进行了杀菌、杀虫生物活性实验,结果表明,部分化合物显示出较高的杀虫、杀菌活性。     

Einsatz der Molekularbiologie in Stoffwechseluntersuchungen des Fettsäure-Abbaus am Beispiel der 3, 2trans-Enoyl-CoA-Isomerase

Recombinant DNA-Techniques in the Study of Fatty Acid Metabolism, Paradigma Demonstrated with 3, 2trans-Enoyl-CoA-Isomerase The enzymatic degradation of saturated and unsaturated fatty acids occurs predominantly in mitochondria. The key enzyme for the degradation of unsaturated fatty acids is the 3, 2trans-enoyl-CoA isomerase which transforms cis- as well as trans-double bonds of unsaturated fatty acyl-CoA esters with rather comparable velocity into the corresponding 2trans-enoyl-CoA intermediate and thereby in one common to that of the β-oxidation spirale of saturated fatty acids. We have purified the isomerase and determined the primary structure by molecular cloning. To elucidate the isomerase mechanism we compared homologies with the enoyl-CoA hydratase, carried out site directed mutagenesis and expressed the wild type and mutant isomerase in E. coli. The recombinant 3, 2trans-enoyl-CoA isomerases are being used for cristallization studies. Human and rodent isomerase are highly homologous. We elucidated the mitochondrial import of the isomerase. Recently the organization of the human isomerase gene has been analyzed in our laboratory.