Ab Initio Study of the Various Pathways of the Decomposition ([2+2]elimination) of 2-Chloroethyltrichlorosilane

Abstract

The decomposition of 2-chloroethyltrichlorosilane (1) to ethylene-tetrachlorosilane (2), hydrogen chloride-ethylenetrichlorosilane (3), and ethylenechloride-trichlorosilane (4) was investigated using ab initio Molecular Orbital (MO) and Density Functional Theory (DFT). Study on the HF/6-31G level of theory revealed that the required energy for the decomposition of compound 1 to 2, 3, and 4 is 59.86, 101.13, and 63.29 kcal mol^?, respectively. MP2/6-31G*//HF/6-31G* calculated barrier height for the decomposition of compound 1 to 2, 3, and 4 is 60.59, 94.04, and 66.91 kcal mol^?1, respectively. Also, B3LYP/6-31G*//HF/6-31G* results indicate that the barrier height for the decomposition of compound 1 to 2, 3, and 4 is 51.71, 85.38, and 53.74 kcal mol^?1, respectively. Among the three methods, which have been used to calculate the barrier height of the decomposition of compound 1 to 2–4, B3LYP/6-31G**//HF/6-31G** is in good agreement with the reported experimental data. Contrary to the previously evaluated experimental values for the decomposition of compoun 1 to 3 and 4, all three methods predict a higher energy barrier for these reactions.     

Vinyl Glycosides in Oligosaccharide Synthesis (Part 6): 3-Buten-2-YL 2-Azido-2-Deoxy Glycosides and 3-Buten-2-YL 2-Phthalimido-2-Deoxy Glycosides as Novel Glycosyl Donors

ABSTRACT

An extension of the latent-active glycosylation strategy is reported whereby 3-buten-2-yl 2-deoxy-2-azidoglycosides and 3-buten-2-yl 2-deoxy-2-phthalimidoglycosides are used as building blocks for the preparation of amino sugar containing oligosaccharides. The allyl moieties of the latent substrates 5, 16 and 19 can be conveniently isomerised by treatment with a catalytic amount of (Ph₃P)₃RhCl/BuLi to give the active vinyl glycosides 6, 17 and 20 in high yield. These glycosyl donors were successfully used in glycosylations with acceptors 7, 9 and 11. In the case of glycosyl donor 6, the disaccharides 8, 10 and 12 could be obtained as anomeric mixtures or with high α-or β-selectivities depending on the reaction conditions selected. Glycosylations with glycosyl donors 17 and 20 in each case gave solely the β-linked products only in high yields.     

Atalantums H-K from the peels of Atalantia monophylla and their cytotoxicity

Abstract

Four new benzoyltyramines, atalantums H-K (1–4) and seven known compounds were isolated from the peels of Atalantia monophylla. All compounds were tested for cytotoxicity against HeLa, HCT116 and MCF-7 cell lines, as well as normal cells (Vero cells). Compound 5 showed cytotoxicity against HeLa, HCT116 and MCF-7 cell lines with IC₅₀ values ranging from 16-25?μg/mL but was inactive against Vero cells. Compound 6 also showed interesting results as compound 5 with IC₅₀ values ranging from 15-18?μg/mL and an IC₅₀ value of 80.20?μg/mL against Vero cells. This means compounds 5 and 6 can be used as lead compounds for anticancer agents.     

Influence of new effective allelochemicals on the distribution of Cleome arabica L. community in nature

Abstract

New allelochemicals were identified through bio-guided fractionation from the ethyl acetate of seeds extracts, which was the most autotoxic compared to the other plant parts. Phytochemical investigation of the seeds extracts of C. arabica by spectroscopy analyses has led to identify two new dammarane type triterpenes (4 and 9), with nine known analogues (1???3, 5???8, 10 and 11), a new cucurbitane triterpene (12), acylated dehydrodiconiferyl alcohol (13), and three highly oxygenated flavonols (14?16). The most autotoxic compounds on germination and seedling growth were elucidated as dammarane type triterpenes. However, less autotoxic effect was recorded by an inhibition under 50% for most of the identified flavonoids. These results suggest that those autotoxic substances may be used as a new bio-herbicide that may contribute to manage the distribution of C. arabica in agronomic field.

     

Synthese,Reaktionen und NMR-Spektren von 2-Brom-3-oxo-1-alkenyl- und 3-Oxo-1-alkinyl-phosphonsäure-dialkylestern

Dialkyl (E)-3-oxo-1-alkenylphosphonates (1), on reaction with bromine and subsequent HBr-elimination, yield the isomeric -bromovinyl derivatives (Z)-3 and (E)-3 and the alkinylphosphonates4. -Bromovinyl compounds3 can also be obtained by reaction of1 withNBS in aqueous solution. The configuration of the -disubstituted vinylcompounds is assigned from their¹³C-NMR spectra. Both bromovinyl compounds3 and alkinylderivatives4 are used for regioselective syntheses of acylsubstituted pyrazolylphosphonates5.

     

Concise synthesis of the retinoic acid receptor (RAR) agonist AGN-193836 utilizing a photochemical benzylic oxidation

Abstract

A new, concise synthesis of retinoic acid receptor (RAR)-α agonist AGN-193836 (1) is described which employs a photochemical benzylic methyl oxidation with molecular oxygen as the key step (3 → 2). Further this route explores the application of green photochemistry in the synthesis of drug candidates and avoids a number of toxic or highly pyrophoric reagents that had been described in previous syntheses of 1. In addition, the oxidation proved to be higher yielding when compared to potassium permanganate, a metal oxidant typically used for this –CH₃ to –CO₂H functional group conversion.     

Preparation of a set of selectively protected disaccharides for modular synthesis of heparan sulfate fragments: toward the synthesis of several <Emphasis Type="Italic">O</Emphasis>-sulfonated [β-D-GlcUA-(1→4)-β-D-GlcNAc]OPr types

A concise method for a stereocontrolled synthesis of a set of selectively protected disaccharides is reported. Coupling of the donor 11 onto acceptors 23 and 24, promoted by trimethylsilyl triflate-N-iodosuccinimide (TMSOTf-NIS), generated the disaccharides 25 and 26. Under typical conditions, condensation of the fully protected donor 12 onto acceptors 23 and 24 produced the disaccharides 27 and 28. The building blocks 25–28 were prepared in moderate yields having exclusive β-stereoselectivity. A unique pattern of protecting groups distinguished clearly between positions to be sulfated and functional groups remaining as free hydroxyl groups. Acetyl and/or levulinoyl esters temporarily protected the positions to be sulfated, while benzyl ethers were used for permanent protection. The anomeric positions were protected as allyl ethers, whereas the 4′-positions were masked as p-methoxybenzyl (PMB) ethers. The orthogonality of the PMB and allyl groups can then be used for further elongation of the chain by recurrent deprotection and activation steps. The hydroxyl group, OH-6, of glucosamine moieties was protected as a TBDPS ether to avoid oxidation. A five-step deprotection/sulfonation sequence was applied to the disaccharide 27 to generate the corresponding sulfated [β-D-GlcUA-2-OSO₃Na-(1→4)-β-D-Glc pNAc]-(1→O-Pro) 34.     

Isolation,characterization, and xanthine oxidase inhibitory activities of flavonoids from the leaves of Perilla frutescens

Abstract

Phytochemical investigation of the water extract from the leaves of Perilla frutescens (Lamiaceae) led to the isolation of a new flavanone, a new chalcone, and a new aurone, namely, (2S)-5,7-dimethoxy-8,4'-dihydroxyflavanone (1), 2',4'-dimethoxy-4,5',6'-trihydroxychalcone (2), and (Z)-4,6-dimethoxy-7,4'-dihydroxyaurone (3), respectively. The structures were unambiguously elucidated on the basis of spectroscopic data. And the absolute configuration of 1 was determined by analysis of electronic circular dichroism spectrum. The isolated compounds were evaluated for their inhibitory effects on xanthine oxidase in vitro. Among them, 2 showed more potent activity than the positive control allopurinol, a well-known XO inhibitor clinically used for treatment of gout. Lineweaver-Burk transformation of the inhibition kinetics data demonstrated that it was a mixed-type inhibitor.

     

Triterpenoid saponins with hepatoprotective effects from the fresh leaves of Metapanax delavayi

Abstract

The fresh leaves of Metapanax delavayi (Araliaceae) have been used as a common wild vegetable for salad and soup, and also herbal tea by the local people living in its growing areas of Yunnan province, China. Detailed chemical investigation led to the identification of a new triterpenoid saponin, 3-O-α-L-arabinopyranosyl-28-O-β-D-glucopyranosyl-(1→6)-O-β-D-glucopyranosyl-3β-hydroxyolean-12-ene-28,29-dioic acid (1) from the fresh leaves, together with 11 known compounds, including six triterpenoid saponins (2–7), two caffeoylquinic acid derivatives (8–9), and three flavonoid glycosides (10–12). Their structures were determined on the basis of spectroscopic analysis and acidic hydrolysis. Compounds 3–5 and 8–12 were isolated from M. delavayi for the first time. Moreover, the known saponins 3-O-β-D-xylopyranosyl-3β-hydroxyolean-12-ene-28,29-dioic acid (3) and yiyeliangwanoside IV (5) exhibited protective effects on HepG2 cells damaged by the alcohol intakes, at a concentration of 1.0?µg/mL. The results indicated M. delavayi is an ideal dietary vegetable and herbal tea with potential hepatoprotective activity.

     

A comparative study of Mentha arvensis L. and Mentha haplocalyx Briq. by HPLC

We have developed a new method to simultaneously determine five marker compounds in Menthae Herba via HPLC/PDA – including hesperidin (1), rosmarinic acid (2), diosmin (3), didymin (4) and buddleoside (5). The newly developed method was successfully used to analyse for two species (Mentha arvensis L. and Mentha haplocalyx Briq.) of Menthae Herba, and the satisfactory results were obtained from the validation of developed method. The pattern analysis could greatly discriminate between M. arvensis L. and M. haplocalyx Briq. In conclusion, the proposed HPLC/PDA method is suitable for quality evaluation of Menthae Herba.     

Antimicrobial pentacyclic triterpenes and glycosides from the stem bark of Cussonia bancoensis

Abstract

The stem bark of Cussonia bancoensis is used traditionally for the treatment of different types of infection and pain. A bioassay guided fractionation of the methanol stem bark extract led to the isolation of five pentacyclic triterpenes and glycosides identified based on spectroscopic data as 23-hydroxyursolic acid (CB1), hederagenin (CB2), 3-O-α-L-arabinopyranosyl-echinocystic acid (CB3), 3-O-α-L-arabinopyranosyl- oleanolic acid (CB4) and 3-O-α-L-arabinopyranosyl-ursolic acid (CB5). CB2 - CB5 are being reported for the first time from this species. The compounds were evaluated for antimicrobial activity against ten microorganisms using the HT-SPOTi method. CB3 demonstrated remarkable antimicrobial activity against S. aureus, S. pyogens, E. faecalis, S. typhi and C. albicans at MICs between 3.12 and 12.5?µg/mL. Among the studied compounds, it was observed that hydroxylation of position C-16 of the oleanane skeleton may enhance antimicrobial activity. This study gives insight into the anti-infective constituents of the stem bark of C. bancoensis and justifies its use in ethnomedicine.     

Synthesis of Potential Impurities of Bicalutamide

Bicalutamide is an oral nonsteroidal, anti-androgen drug used for prostate cancer. It binds to the androgen receptor. During the bulk synthesis of bicalutamide, various impurities are formed. The present work details the development of simple processes for the preparation of impurities of bicalutamide, viz bical-sulfoxides (6), bical-deshydroxy (10), bical-desfluoro (10a), bical-2-fluoro (10b), and bical-3-fluoro (10c).     

Polymerisation of styrene in microemulsion with catanionic surfactant mixtures

The use of aqueous catanionic surfactant mixtures in the oil-in-water (o/w) microemulsion polymerisation of styrene is reported. Catanionic surfactant mixtures of dodecyltrimethylammonium bromide 1 and sodium dodecylsulfate 3, or decanediyl-1,10-bis(dimethyldodecylammonium bromide) 2, a gemini surfactant, and the anionic surfactant 3 were used. Phase behaviour and polymerisation properties of the microemulsions were studied as a function of the total surfactant concentration and the cationic/anionic surfactant ratio. Single-phase o/w microemulsions were only formed if either the cationic or anionic surfactant were present in large excess. Upon -irradiation, polymer nanoparticles were obtained. Using dynamic light scattering, the particle radii were determined to be 10 to 20 nm, the size depending on the total surfactant concentration, the cationic/anionic surfactant ratio and the surfactant/styrene ratio. Size exclusion chromatography indicated molecular weights of polystyrene of between 3×10⁵ and 1.4×10⁶ Daltons. Catanionic 1/3 and 2/3 mixtures differ in their styrene solubilizations. In a 1- or 3-rich system, the solubilization efficiency can be improved by increasing the concentration of the oppositely charged minor surfactant component, while in a 2-rich system the addition of 3 only diminishes the efficiency. Possible reasons for the different behaviours are discussed.     

Studies on Pyrazine Derivatives,XLIII: Synthesis and Antituberculosis Activity of 6-(1,2,3,4-Tetrahydroisoquinolino) and 6-(1,3,3-Trimethyl-6-azabicyclo-[3, 2, 1]-octano)-pyrazinocarboxylic Acid Derivatives

The reactivity of the chloride atom of 2-cyano-6-chloropyrazine was used in the reactions with amines, 1,2,3,4-tetrahydroisoquinoline and 1,3,3-trimethyl-6-azabicyclo-[3,2,1]-octane, which yielded the substrates for the syntheses of a series of new derivatives. The bulk of them were tested for their tuberculostatic activity. MIC values of the most active ones ( 2a , b , 5b , 7a , 9b , and 11b ) were within 3.1–50 μ g/mL.     

Unusual regioselective acylation of the primary hydroxy groups of β-cyclodextrin

The reaction of -cyclodextrin (1) with palmitoyl (2) and valeryl (4) chlorides in DMF or Py, unlike previously studied acetylation of 1, involves only the primary hydroxy groups of 1. The outcome of the reaction depends on the reaction conditions and the nature of the acid scavenger used (Et₃N, Prⁱ ₂NEt, PhNMe₂, Py). ¹³C NMR spectroscopy was shown to be an effective tool in determining the number and position of aliphatic carboxylic acid residues introduced into 1. A hypothesis stating that preliminary formation of a reactive inclusion complex (acid chloride1) is required for the acylation of 1 to occur is proposed and substantiated. This hypothesis provides a unified explanation for a variety of unusual facts observed in the acylation of 1 and its derivatives.     

The antioxidant compounds isolated from the fruits of chinese wild raspberry Rubus Chingii Hu

Abstract

Raspberry, the fruit of Rubus Chingji Hu, is a widely distributed economic staple food in China. It has long been used as a traditional medicine in mainland China to treat kidney enuresis, nocturnal emission and premature ejaculation in clinic. In this paper, six known compounds (1?–?6) were purified from the fruits of Rubus chingji. Their structures were elucidated as (16α)-16,17-dihydroxy-ent-kauran-2-one17-O-β-D-glucopyranoside (1), (16R) -16,17-dihydroxy-ent-kaurane-2-one (2), 3,3′-di-O-methylellagic acid 4-(5′′-acetyl)-α-L-arabinofuranoside (3), quercilicoside A (4), esculetine (5) and ethyl-β-D-glucoside (6). All the compounds were isolated from Rubus Chingji Hu for the first time. Compounds 3 and 5 shown distinctive free radical scavenging activities in DPPH and FRAP assays. In addition, no cytotoxicity was observed for compounds 3 and 5 against different cancer cells, suggesting that they might be useful as potential antioxidant agents against various reactive oxygen species.

     

Synthesis of γ-Cyclodextrin Pyrene-Labeled at the Hetero Rim and Its Use in Fluorescent Molecular Sensing

Fluorogenic active host labeled at the upper and lower rims of -cyclodextrin, namely, mono-3^A-deoxy-3^A-pyrenebutylamido-6^X-O-mono-pyrenebutylate-mono-altro--cyclodetrin (mixture -1,X = A, B, C, D, E, F, G, or H), has been synthesized in order to investigate their host-guest complexation with steroidal compoundsusing fluorescence spectra. Monomer and excimer fluorescence was observed for mixture host. Inclusion of a guest molecule in the cyclodextrin cavity resultedin increased monomer fluorescence and decreased excimer fluorescence. The extent of monomerand excimer fluorescence variations ofmixture -1 with the guestwas used as an indication for the sensing ability. The guest inducedfluorescence changes were measured for 10^-7 M solutions of mixture -1.The values I/I ⁰ , where I ⁰ and I are fluorescence intensities in the absence and presence of a guest, respectively, and I is I ⁰ - I, were then used to describe the sensing ability.     

Preparation of Some Fused Pyridopyrimidine and Pyridothienotriazine Derivatives for Biological Evaluation

Compounds 2 and 9 were formed using 3-(4-chloro-phenyl)-1-pyridin-2-yl propenone ( 1 ) and malononitrile or ethyl cyanoacetate, respectively. The pyridine derivative 2 was in turn used as a precursor for the preparation of some pyridopyrimidine and fused pyridopyrimidine derivatives 3–8 On the other hand, the pyridine derivative 9 was used for the preparation of thienopyridine derivatives 11 and 12 Nitrozation of compound 12 afforded pyridothienotriazine derivative 13 Some of the prepared products showed potent antimicrobial activity.     

The effect of short alkane bridges in stability of bisbenzimidazole-2-ylidene silver(I) complexes: synthesis,crystal structure and antibacterial activity

Three bisbenzimidazolium salts, 3,3-(alkane-1,n-diyl)bisbenzylbenzimidazolium dibromide/dihexafluorophosphate (1a/b–3a/b) (where alkane?=?ethane, propane or butane and n?=?2, 3, or 4), were synthesized. The bromide salts were subsequently used as precursors to prepare their respective Ag(I)-NHC complexes via in situ deprotonation method. The successful formation of all bisbenzimidazolium salts and complexes were proved by elemental analysis, ¹H-NMR, ¹³C-NMR and FT-IR analyses. From single-crystal X-ray diffraction analyses, 4 has been established as a binuclear complex with the molecule arranged as in trans-conformation. Salts 1b–3b and Ag(I)-NHC complexes 4–6 were then screened for their antibacterial potential against E. coli (ATCC 25922) and S. aureus (ATCC 12600). All the bisbenzimidazolium salts do not show any activity against both bacteria while 4 exhibits the highest activity against both bacteria in all methods followed by 5 and 6.     

Basische Tetrahydro-dibenzofuran-Derivate mit einem Abstand von drei C-Atomen zwischen dem Stickstoff und dem quartären C-Atom

Pummerer's ketone (1) is a pharmacophoric synthon, which can be used for a great number of synthetic variations. We have investigated the insertion of basic groups into C-1, C-2 and C-3. TheClaisen rearrangement of the allylic alcohols2 a and2 b leads to3 a and3 b, the reduction of which produces4 a and4 b. TheMannich reaction of1 unexpectedly gives the 2-aminoalkylcompounds7 c-j and the synthesis of the derivatives2e-j was performed by aminolysis of the 3-chloro-compound2 d.