bluuebunny/crossref_metadata_2025_split huggingface dataset:
New Acylated Triterpene Saponins from Polygala arenaria
Authors: Mitaine‐Offer Anne‐Claire , Miyamoto Tomofumi , Laurens Véronique , Delaude Clément , Lacaille‐Dubois Marie‐Aleth 
Published: August 2003

AbstractEight new acylated triterpene saponins 1–8 were isolated from the roots of Polygala arenaria as four inseparable (E)/(Z) mixtures of the 4‐methoxycinnamoyl and 3,4‐dimethoxycinnamoyl derivatives by repeated MPLC over silica gel. Their structures were established mainly by 600‐MHz 2D‐NMR techniques (1H,1H‐COSY, TOCSY, NOESY, HSQC, HMBC) as 3‐O‐(β‐D‐glucopyranosyl)presenegenin 28‐(O‐β‐D‐galactopyranosyl‐(1→4)‐O‐[β‐D‐glucopyranosyl‐(1→3)]‐O‐β‐D‐xylopyranosyl‐(1→4)‐O‐α‐L‐rhamnopyranosyl‐(1→2)‐{4‐O‐[(E)‐4‐methoxycinnamoyl]}‐β‐D‐fucopyranosyl) ester and its (Z)‐isomer (1/2), 3‐O‐(β‐D‐glucopyranosyl)presenegenin 28‐(O‐β‐D‐galactopyranosyl‐(1→4)‐O‐[β‐D‐glucopyranosyl‐(1→3)]‐O‐β‐D‐xylopyranosyl‐(1→4)‐O‐α‐L‐rhamnopyranosyl‐(1→2)‐{4‐O‐[(E)‐3,4‐dimethoxycinnamoyl]}‐β‐D‐fucopyranosyl) ester and its (Z)‐isomer (3/4), 3‐O‐(β‐D‐glucopyranosyl)presenegenin 28‐(O‐β‐D‐glucopyranosyl‐(1→3)‐O‐α‐L‐arabinopyranosyl‐(1→4)‐O‐α‐L‐rhamnopyranosyl‐(1→2)‐{4‐O‐[(E)‐4‐methoxycinnamoyl]}‐β‐D‐fucopyranosyl) ester and its (Z)‐isomer (5/6), and 3‐O‐(β‐D‐glucopyranosyl)presenegenin 28‐(O‐β‐D‐glucopyranosyl‐(1→3)‐O‐α‐L‐arabinopyranosyl‐(1→4)‐O‐α‐L‐rhamnopyranosyl‐(1→2)‐{4‐O‐[(E)‐3,4‐dimethoxycinnamoyl]}‐β‐D‐fucopyranosyl) ester and its (Z)‐isomer (7/8) (presenegenin=(2β,3β)‐2,3,27‐trihydroxyolean‐12‐ene‐23,28‐dioic acid). In our in vitro lymphocyte proliferation assay (Jurkat T‐leukemia cells), a fraction containing 1–4 showed a concentration‐dependent immunomodulatory effect. This effect was not found for the prosapogenin (tenuifolin=3‐O‐(β‐D‐glucopyranosyl)presenegenin), underlining the importance of the acyloligosaccharidic moiety.
Cytotoxic Pentacyclic Triterpenoids from the Rhizome of Astilbe chinensis
Authors: Sun Hongxiang , Zhang Jianxin , Ye Yiping , Pan Yuanjiang , Shen Yueao 
Published: August 2003

AbstractGuided by in vitro antineoplastic tests, four cytotoxic pentacyclic triterpenoids, 3β‐hydroxyolean‐12‐en‐27‐oic acid (1), 3β‐hydroxyurs‐12‐en‐27‐oic acid (2), 3β,6β‐dihydroxyolean‐12‐en‐27‐oic acid (3), and 3β‐acetoxyolean‐12‐en‐27‐oic acid (4) were isolated from the rhizome of Astilbe chinensis. Their structures were determined on the basis of chemical evidence and extensive spectroscopic methods including one‐dimensional and two‐dimensional NMR. These compounds showed cytotoxic activities against HO‐8910, Hela and HL60 cell lines. In addition, β‐sitosterol palmitate, daucosterol, and β‐sitosterol have also been isolated.
Novel Sesquiterpenes from the Fungus Lactarius piperatus
Authors: Wang Ying , Yang Sheng‐Ping , Yue Jian‐Min , Chow Sharon , Kitching William 
Published: August 2003

AbstractFour novel sesquiterpenes, namely 7α,8β,13‐trihydroxy‐5,13‐marasmanolide (2), isoplorantinone (5), 4,8,14‐trihydroxyilludala‐2,6,8‐triene (6), and 8‐hydroxy‐8,9‐secolactara‐1,6‐dien‐5,13‐olide (10), together with six known ones, 7α,8β‐dihydroxy‐5,13‐marasmanolide (1), 7α,8α‐dihydroxy‐5,13‐marasmanolide (3), isolactarorufin (4), blennin A (7), blennin D (8), and lactarorufin (9), were isolated from the ethanolic extract of Lactarius piperatus. The structures of these sesquiterpenes, representing diversified structural types, were determined mainly by spectroscopic methods, especially 2D‐NMR techniques. The structure of 6 was further confirmed by a single‐crystal X‐ray‐diffraction determination.
Simultaneous Determination of Chromium(VI) and Aluminum(III) by Adsorptive Stripping Voltammetry with Pyrocatechol Violet
Authors: Vargas Miguel Cámara , Renedo Olga Domínguez , Arcos Martinez M. Julia 
Published: August 2003

AbstractA new methodology is presented for the simultaneous determination of chromium(VI) and aluminum(III) by differential‐pulse adsorptive stripping voltammetry (DPAdSV) with Pyrocatechol Violet (PCV) as a complexing agent. In this procedure, a partial least‐squares regression (PLS) is used for the resolution of the strongly overlapping voltammetric signals from mixtures of CrVIand AlIIIin the presence of PCV. The procedure was successfully applied to the determination of these metals in river water.
Binuclear Nickel(II) and Cobalt(III) Complexes with Dissimilar Bridges: Synthesis, Spectroscopy, Crystal Structure, and Magnetism
Authors: Wang Qing‐Lun , Yu Li‐Hua , Liao Dai‐Zheng , Yan Shi‐Ping , Jiang Zong‐Hui , Cheng Peng 
Published: August 2003

AbstractTwo novel binuclear nickel(II) and cobalt(III) complexes with two or three dissimilar bridges, [Ni2(tacn)2(μ‐N3)2(μ‐O2CPh)](ClO4)⋅H2O (1) and [Co2(tacn)2(μ‐N3)(μ‐OH)(μ‐O2CPh)](ClO4)3 (2) (tacn=1,4,7‐triazacyclononane), were synthesized and structurally as well as magnetically characterized. Both compounds have a discrete binuclear structure, bridged by two N3− ions and one carboxylato group of the benzoate ion for 1 and one N3− ion, one carboxylato group of the benzoate ion, and one hydroxy group for 2; the macrocyclic ligand tacn acts as terminal ligand. The magnetic data of compound 1 were analyzed by means of Ĥ = −2JŜ1Ŝ2−D(Ŝ12+Ŝ22), leading to J = 19.6 cm−1, g=2.07, D = 4.01 cm−1, and zJ′ = $\rm{-}$0.32 cm−1. The ferromagnetic interaction is discussed on the basis of the structural features.
New Long‐Chain Esters and Adenine Analogs from the Leaves of Formosan Bridelia balansae
Authors: Tsai Yeh‐Hsin , Chen Ih‐Sheng , Tsai Ian‐Lih 
Published: August 2003

AbstractSix new compounds, including the two long‐chain esters balansenate I (=6,8,11‐trimethyldodecanoic acid (2E)‐3‐methylhexadec‐2‐enyl ester; 1) and balansenate II (=10,12,15‐trimethylhexadedecanoic acid (2E)‐3‐methylhexadec‐2‐enyl ester; 2), the eburicane‐like triterpenoid bridelone (=hexadecahydro‐4,4,10,13,14‐pentamethyl‐17‐(5‐methyl‐1,4‐dimethylenehexyl)‐3H‐cyclopenta[a]phenanthren‐3‐one; 3), the ‘deimino‐xanthine', bridelonine (=5‐(3‐methylbut‐2‐enyl)pyrrolo[3,4‐d]imidazole‐4,6(1H,5H)‐dione; 6), and the two adenine analogs 9‐(3‐methylbut‐2‐enyl)adenine (7) and 1‐(3‐methylbut‐2‐enyl)adenine (8), besides three known compounds, i.e., N6‐(3‐methylbut‐2‐enyl)adenine (4), 3‐(3‐methylbut‐2‐enyl)adenine (5), and adenine (9), were isolated from the leaves of Formosan Bridelia balansae. The novel skeleton of 6 consists of a fused pyrrolidine‐2,5‐dione and imidazole moiety. The already known adenines 7 and 8 were isolated for the first time from a plant. The structures of the isolated compounds were elucidated by spectroscopic analyses.
Synthesis and Evaluation of Chromogenic and Fluorogenic Analogs of Glycerol for Enzyme Assays
Authors: González‐García Eva Maria , Grognux Johann , Wahler Denis , Reymond Jean‐Louis 
Published: August 2003

AbstractThe branched glycerol analogs 1 and 2 were prepared. Mono‐ester derivatives of these triols undergo a chromogenic or fluorogenic reaction in the presence of NaIO4. In contrast, both the diesters and the triols are themselves not chromogenic or fluorogenic. Diester derivatives of these triols can be used as probes for lipases. The tris‐phosphate derivative of 1 is a fluorogenic substrate for various phosphatases.
Metal Complexes of Functionalized Sulfur‐Containing Ligands. Part XIX
Authors: Stachel Hans‐Dietrich , Immerz‐Winkler Elisabeth , Poschenrieder Hermann , Windt Andreas , Weigand Wolfgang , Drescher Norbert , Wünsch Ralf 
Published: August 2003

AbstractThe title compounds were prepared starting from the dihydropyrrolones 4–6. Nucleophilic displacement and ring closure yielded the 1H‐pyrrolo[3,2‐c]isothiazol‐5(4H)‐ones 8 and 10. The fused systems formed salts with strong acids and electrophiles (15, 16), as well as with bases. Oxidation led either to S(2)‐oxides (18a, 20a) or to the corresponding bicyclic sultams (18b, 20b), depending on the reaction conditions. The sulfinamide 18a was also obtained from the known 1,2‐dithiolopyrrolone S‐oxide 21 by a ring‐opening/ring‐closure reaction sequence. O‐Methylation of 8 furnished the ‘azafulvene' 17. The oxidative addition of [Pt(η2‐C2H4)L2] (24a: L=Ph3P, 24b: L=1/2 dppf, 24c: L=1/2 (R,R)‐diop) to 18a and 20a led to the cis‐amido‐sulfenato Pt complexes 25 and 26a–c, respectively.
Synthesis, and Antimycobacterial and Cytotoxic Evaluation of Certain Fluoroquinolone Derivatives
Authors: Sheu Jia‐Yuh , Chen Yeh‐Long , Tzeng Cherng‐Chyi , Hsu Shu‐Lin , Fang Kuo‐Chang , Wang Tai‐Chi 
Published: August 2003

AbstractCertain 1‐ethyl‐ and 1‐aryl‐6‐fluoro‐1,4‐dihydroquinol‐4‐one derivatives were synthesized and evaluated for antimycobacterial and cytotoxic activities. Preliminary results indicated that, for 1‐aryl‐6‐fluoroquinolones, both 7‐(piperazin‐1‐yl)‐ and 7‐(4‐methylpiperazin‐1‐yl) derivatives, 9b and 11a, are able to completely inhibit the growth of M. tuberculosis at a concentration of 6.25 μg/ml, while the 7‐[4‐(2‐oxo‐2‐phenylethyl)piperazin‐1‐yl] derivative 13 exhibits only 31% growth inhibition at the same concentration. For 1‐ethyl‐6‐fluoroquinolones, both 7‐[4‐(2‐oxopropyl)piperazin‐1‐yl]‐ and 7‐[4‐(2‐oxo‐2‐phenylethyl)piperazin‐1‐yl]‐derivatives, 2a and 2b, respectively, show complete inhibition, while their 2‐iminoethyl and substituted phenyl counterparts 3a and 2c are less active. In addition, the 6,8‐difluoro derivative was a more‐favorable inhibitor than its 6‐fluoro counterpart (2b vs. 2d). These results deserve full attention especially because 2a, 2b, 9b, and 11a are non‐cytotoxic at a concentration of 100 μM. Furthermore, compound 9b proved to be a potent anti‐TB agent with selective index (SI)>40 and an EC90 value of 5.75 μg/ml.
Glycosylidene Carbenes. Part 32
Authors: Mangholz Sissi E. , Briner Karin , Bernet Bruno , Vasella Andrea 
Published: August 2003

AbstractAcylation and sulfonylation of the N,N′‐unsubstituted glucosylidenespirodiaziridines 1A/1B 95 : 5 with Ac2O, BzCl, FmocCl, TsCl, (naphthalen‐2‐yl)sulfonyl, and (2,4,6‐triisopropylphenyl)sulfonyl chloride, and concomitant rearrangement gave the acylated and sulfonylated gluconolactone hydrazones 2B–2G in 40–83% yield (Scheme 2). Similarly, the galacto and manno analogues 3A/3B 95 : 5 and 5A/5B 55 : 45 and the mannofuransoylidene‐diaziridine 30 were acetylated and tosylated to give 4A, 4B, 6, 31A, and 31B (55–73% yield; Schemes 2 and 5). 15N‐Labelling of 11A/11B and 14A/14B showed that the pseudoequatorial NH of the gluco diaziridines 1 and the pseudoaxial NH of the galacto diaziridines 3 were preferentially acetylated and tosylated (Scheme 3). Sulfonylation of the N‐methylated diaziridines 19A/19B 72 : 28, 22A/22B 85 : 15, 25A/25B 85 : 15, 28A/28B 80 : 20, and 33A/33B/33C/33D 76 : 4 : 12 : 8 yielded the N‐methyl‐N‐tosylglyconolactone hydrazones 20, 23, 26, 29, and 34 (44–66%; Schemes 4 and 5). The methylated N‐atom of the diaziridines proved more reactive, irrespective of the configuration at C(2) and C(4). The products were readily hydrolysed to glyconolactones.
Reactions of Phosphate Radicals with Monosubstituted Benzenes. A Mechanistic Investigation
Authors: Rosso Janina A. , Caregnato Paula , Mora Verónica C. , Gonzalez Mónica C. , Mártire Daniel O. 
Published: August 2003

AbstractThe kinetics and reaction mechanism of phosphate radicals with substituted benzenes, PhX (X=OH, Me, H, Cl, MeO, and CHO), were studied by flash photolysis and continuous irradiation of aqueous solutions containing potassium peroxodiphosphate (K4[(PO3)2O2]). The rate constants for the reactions of phosphate radicals with the aromatic contaminants PhX were measured and the reaction intermediates and products detected. A correlation between the logarithm of the rate constant for every substrate with H2PO4., HPO4.−, and PO4.2− and the logarithm of the dissociation constant Ka for H3PO4, $\rm{ H_2 PO_4^ -}$, and $\rm{ HPO_4^{2 - }}$ was found. A general mechanism is proposed (Scheme 1), which accounts for the experimental results.
Chemical Constituents from the Whole Plant of Euphorbia altotibetic
Authors: Li Pan , Feng Zhang Xiao , Ye Deng , Huan Wang , Da Gang Wu , Dong Luo Xiao 
Published: August 2003

AbstractFour new jatrophane diterpenoids, altotibetin A (1), altotibetin B (2), altotibetin C (3), altotibetin D (4), and nine known compounds, β‐sitosterol, cycloart‐23‐ene‐3β,25‐diol, cycloart‐25‐ene‐3β,24‐diol, lupeol acetate, scopoletin, kaempferol, uracil, uridine, astragalin, and daucosterol have been isolated from the whole plant of Euphorbia altotibetic Pauls. Their structures were established by spectral methods, and the configurations of 1 and 2 were confirmed by X‐ray analysis.
Nucleotides. Part LXXII
Authors: Beier Markus , Pfleiderer Wolfgang 
Published: August 2003

AbstractThe synthesis of various N‐methylated nucleosides (m6A, m3C, m4C, m3U) is described. These minor nucleosides can be obtained by simple methylation with diazomethane of [2‐(4‐nitrophenyl)ethoxy]carbonyl(npeoc)‐protected nucleosides. These methylated compounds are easily further derivatized to fit into the scheme of the [2‐(dansyl)ethoxy]carbonyl (dnseoc) approach for RNA synthesis (dansyl=[5‐(dimethylamino)naphthalen‐1‐yl]sulfonyl). Various oligoribonucleotides containing N6‐methyladenosine were synthesized, underlining the usefulness of the dnseoc approach, especially for the synthesis of natural tRNA‐derived oligoribonucleotide sequences.
Novel Anti‐Inflammatory Constituents of Artocarpus rigida
Authors: Lu Yi‐Huang , Lin Chun‐Nan , Ko Horng‐Huey , Yang Sheng‐Zehn , Tsao Lo‐Ti , Wang Jih‐Pyang 
Published: August 2003

AbstractA novel phenolic compound containing an oxepine ring, artocarpol I (1), and a new biphenylpropanoid, artocarpol J (2), were isolated from the root bark of Artocarpus rigida. The structures, including relative configurations, were elucidated by spectroscopic data. Compound 1 and artocarpol J peracetate (3) strongly inhibited in a concentration‐dependent manner the formyl‐Met‐Leu‐Phe (fMLP)/cytochalasin B (CB)‐stimulated superoxide anion formation in neutrophils with IC50 values of 17.1±0.40 and 20.5±2.60 μM, respectively. Biogenetically, all the novel phenolic compounds isolated from this plant seem to be derived from stilbene.
Helix Formation and Folding in γ‐Peptides and Their Vinylogues
Authors: Baldauf Carsten , Günther Robert , Hofmann Hans‐Jörg 
Published: August 2003

AbstractA complete overview of all possible periodic structures with characteristic H‐bonding patterns is provided for oligomers composed of γ‐amino acids (γ‐peptides) and their vinylogues by a systematic conformational search on hexamer model compounds employing ab initio MO theory at various levels of approximation (HF/6‐31G*, DFT/B3LYP/6‐31G*, SCRF/HF/6‐31G*, PCM//HF/6‐31G*). A wide variety of structures with definite backbone conformations and H‐bonds formed in forward and backward directions along the sequence was found in this class of foldamers. All formally conceivable H‐bonded pseudocycles between 7‐ and 24‐membered rings are predicted in the periodic hexamer structures, which are mostly helices. The backbone elongation in comparison to α‐ and β‐peptides allows several possibilities to realize identical H‐bonding patterns. In good agreement with experimental data, helical structures with 14‐ and 9‐membered pseudocycles are most stable. It is shown that the introduction of an (E)‐double bond into the backbone of the γ‐amino acid constituents, which leads to vinylogous γ‐amino acids, supports the folding into helices with larger H‐bonded pseudocycles in the resulting vinylogous γ‐peptides. Due to the considerable potential for secondary‐structure formation, γ‐peptides and their vinylogues might be useful tools in peptide and protein design and even in material sciences.
Synthese von Polymethintetrathiafulvalenen durch Dimerisierung von ω‐(1,3‐Dithiol‐2‐yliden)polyenalen mit dem Lawesson‐Reagens: Carotinoide und supracarotinoide Tetrathiafulvalene
Authors: Märkl von Gottfried , Aschenbrenner Norbert , Baur Andreas , Rastorfer Corinna , Kreitmeier Peter 
Published: August 2003

AbstractSynthesis of Polymethinetetrathiafulvalenes by Dimerization of ω‐(1,3‐Dithiol‐2‐ylidene)polyenals with the Lawesson Reagent: Carotenoid and Supracarotenoid TetrathiafulvalenesThe dimerization of aldehydes via their unstable thioaldehydes giving 1,3‐dithietanes, which undergo sulfur extrusion to give alkenes (see Scheme 8) is used for a new, general synthesis of tetrahiafulvalenes with polymethine spacers. In the presence of the Lawesson reagent 19, the 2‐(ω‐oxopolyenylidene)‐1,3‐dithiol‐4,5‐dicarbonitriles 6 and 13 and the ω‐(1,3‐benzodithiol‐2‐yliden)polyenals 8 and 15 can be dimerized via the thioaldehydes. The aldehydes 6 and 13 are obtained by reaction of the unsaturated dialdehydes 4, 2,7‐dimethylocta‐2,4,6‐trienedial (14a) and crocetindialdehyde (14b) with 1 mol of 2‐thioxo‐1,3‐dithiole‐4,5‐dicarbonitrile (5) and 2 mol of triphenylphosphine (Schemes 5 and 6). The ω‐(1,3‐benzodithiol‐2‐yliden)polyenales 8 and 15 were prepared by the Wittig reaction of the dialdehydes with 1 mol of (1,3‐benzodithiol‐(2‐yl)tributylphosphoniumtetrafluoroborate (12) (Schemes 7 and 6).Starting from the corresponding aldehydes 6 and 13, the polymethinetetrathiafulvalenes 7d, 16a, and 16b with conjugated 16 and 32 polymethine chains become available (Schemes 9 and 10), which we call carotinoid and supracarotinoid tetrathiafulvalenes. The (benzodithiol‐2‐yliden)acetaldehyde (8a) and ‐butenal (8b) are dimerized to give the tetrathiafulvalenes 9a and 9b with 4 and 8 methine C‐atoms, respectively (Scheme 11). In case of 15a und 15b, the Lawesson method fails, the dimer 17a with 16 methine C‐atoms can be obtained from 15a via the McMurry reaction (Scheme 13).The intermediate thioaldehydes can be intercepted by the formation of Diels–Alder adducts with hexachlorocyclopentadiene and hexa‐2,4‐diene (Scheme 12). The redox potentials E1/2 of the described polymethinetetrathiafulvalenes are reported.
Synthese von neuen (Phenylalkyl)aminen zur Untersuchung von Struktur–Aktivitätsbeziehungen. Mitteilung 2
Authors: Trachsel Daniel 
Published: August 2003

AbstractSynthesis of Novel (Phenylalkyl)amines for the Investigation of Structure–Activity Relationships. Part 21). 4‐Thio‐Substituted [2‐(2,5‐Dimethoxyphenyl)ethyl]amines (=2,5‐Dimethoxybenzeneethanamines)The 4‐substituted [2‐(2,5‐dimethoxyphenyl)ethyl]amines (=2,5‐dimethoxybenzeneethanamines) and its α‐methyl analogs are known to act as potent 5‐HT2A/C ligands, which have, depending on their 4‐substituent, agonistic or antagonistic character. Generally, compounds with a small lipophilic substituent typically are agonists and those with a larger lipophilic substituent predominantly antagonists or at least partial agonists. Since little is known about the transition and more information is needed about the structural requirements of the 4‐substituent to control the functional activity, 12 novel 4‐thio‐substituted [2‐(2,5‐dimethoxyphenyl)ethyl]amines were synthesized and spectroscopically characterized. Thus 2,5‐dimethoxybenzenethiol (7) was converted to the thioether derivatives 8a–l with several alkyl, fluoroalkyl, alkenyl, and benzyl halides. Subsequent Vilsmeier‐formylation afforded the benzaldehydes 9a–l, condensation with MeNO2 the nitroethenyl derivatives 10a–l, and reduction with AlH3 the desired (2‐phenylethyl)amines 11a–l.
Allylic Sulfones Containing Triene Moieties as Key Synthons for Carotenoid Synthesis
Authors: Ji Minkoo , Choi Hojin , Jeong Young Cheol , Jin Jingquan , Baik Woonphil , Lee Sijoon , Kim Jeong Soo , Park Minsoo , Koo Sangho 
Published: August 2003

AbstractAn efficient synthetic method for the allylic sulfone 2 containing a conjugated triene moiety has been proposed involving i) coupling of allylic sulfones 4 with the C5 bromoallylic sulfide 5, ii) base‐promoted dehydrosulfonation in the presence of allylic sulfide, and iii) selective oxidation of the resulting trienyl sulfide to the corresponding sulfone. Total synthesis of lycopene starting from the C15 allylic sulfone 2b has been described, where the new C10 bis(chloroallylic) sulfone 11 proved to be a useful substitute for the C10 bis(chloroallylic) sulfide 3, which did not require the problematic chemoselective sulfur oxidation in a conjugated polyene.
Stereochemistry of the Conversion of 2‐Phenoxyethanol into Phenol and Acetaldehyde by Acetobacterium sp.
Authors: Speranza Giovanna , Mueller Britta , Orlandi Maximilian , Morelli Carlo F. , Manitto Paolo , Schink Bernhard 
Published: August 2003

AbstractThe conversion of 2‐phenoxyethanol to phenol and acetate by the anaerobic bacterium Acetobacterium sp. strain LuPhet1 proceeds through acetaldehyde with concomitant migration of a H‐atom from C(1) to C(2) of the glycolic moiety. Separate feeding experiments with (R)‐ and (S)‐2‐phenoxy(1‐2H)ethanol, prepared via chemoenzymatic syntheses, indicate that the H‐atom involved in the 1,2‐shift is the pro‐S one of the enantiotopic couple of the alcohol function.
Design and Synthesis of Guanidinoglycosides Directed against the TAR RNA of HIV‐1
Authors: Wang Min , Tu Peng‐Fei , Xu Zhi‐Dong , Yu Xiao‐Lin , Yang Ming 
Published: August 2003

AbstractReplication of human immunodeficiency virus type 1 (HIV‐1) requires specific interactions of the Tat protein with the transactivation responsive region (TAR) RNA. Tat‐TAR RNA Interaction is mediated by a short arginine‐rich domain of the protein. Disruption of this interaction could, in theory, create a state of complete viral latency. Here, four novel 6‐amino‐6‐deoxytrehalose guanidinoglycoside derivatives (10 and 13–15) as target molecules have been designed to bind to TAR RNA for blocking the interaction of Tat‐TAR RNA. They were obtained by coupling 6‐amino‐6‐deoxy‐α,α‐trehalose (6) with the protected amino acids, deprotection by catalytic hydrogenation, followed by guanidinylated with S‐methylisothiourea sulfate. Their abilities to inhibit Tat‐TAR RNA interaction were determined by a Tat‐dependent HIV‐1 long terminal repeats (LTR)‐driven chloramphenicol acetyltransferase (CAT) assays.
A Diterpenoid with a New Skeleton and Cytotoxic Terpenoids Isolated from Amentotaxus formosana
Authors: Su Huey‐Jen , Wang Li‐Wen , Lin Chun‐Nan , Day Shiow‐Hwa , Wei Bai‐Luh , Yang Sheng‐Zehn , Won Shen‐Jeu 
Published: August 2003

AbstractThe new diterpenoid 6α‐hydroxy‐ent‐kaur‐16‐en‐15‐one (1) and a diterpenoid with a new skeleton, i.e., amentotaxin BB (5), as well as three new lanostanoids, i.e., (3β,23R)‐3‐methoxy‐24‐methylenelanost‐8‐en‐23‐ol (6), (23S)‐23‐methoxy‐24‐methylenelanost‐8‐en‐3‐one (7), and (3β,24ξ)‐3‐methoxy‐24‐methyl‐9,19‐cyclolanostan‐25‐ol (8), were isolated from the bark and leaves of Amentotaxus formosana. Their structures, including the relative configurations, were elucidated from spectroscopic data. Compound 1 and a known compound, ent‐kaur‐16‐en‐15‐one (2), showed potent cytotoxic effects against a number of cancer cells in vitro.
Zn2+‐Complexation by a β‐Peptidic Helix and Hairpin Containing β3hCys and β3hHis Building Blocks: Evidence from CD Measurements. Preliminary Communication
Authors: Rossi Francesco , Lelais Gérald , Seebach Dieter 
Published: August 2003

AbstractTwo new β3‐homohistidine‐ and β3‐homocysteine‐containing β‐peptides have been prepared by solid‐phase synthesis. A β‐octapeptide (2) contains seven β3‐amino acids and one β2‐amino acid. The β2/β3 segment has been placed in the middle of this peptide, which contains β3‐amino acids of alternating configuration, to induce the formation of a hairpin secondary structure. A β‐decapeptide (3) has been designed to fold to a 314‐helical secondary structure with neighboring His side chains in 6‐ and 9‐positions. Circular‐dichroism (CD) measurements show the capability of both peptides to bind Zn2+ ions in aqueous solution. In the case of the β‐octapeptide, binding of Zn2+ causes a dramatic change of the CD spectrum, indicating a change or a stabilization of its secondary structure. Zn2+ Ions clearly stabilize the 314‐helix of the β‐decapeptide, in neutral and basic solution. For the construction of the two new β‐peptides, we needed to have a supply of the β‐amino acid derivatives Fmoc‐β3hCys(Trt)‐OH and Fmoc‐β3hHis(Trt)‐OH, the preparation of which is described herein.