Die Glykoside der Wurzeln von Xysmalobium dilatatum Weimarck. 2. Mitteilung: Teilstruktur der Dilatoside. Glykoside und Aglykone, 328. Mitteilung

The four dilatosides A, B, C and D (ester glycosides isolated from Xysmalobium dilatatum) differ from each other only in the sugar portion. They all contain the same aglycone: 12-O-acetyl-17-isolineolone (=12-O-acetyl-17-isodeacyl-cynanchogenin) ( 6 ). Its mass spectrum is discussed. In dilatoside A ( 1 ) three molecules of D -oleandrose ( 7 ) are linked to this aglycone, in dilatoside B ( 2 ) one D -canarose ( 8 ) and two oleandrose units, in dilatoside C ( 3 ) two canarose and three oleandrose, and in dilatoside D ( 4 ) probably three canarose and two oleandrose units.     

Determination of Water- and Fat-Soluble Vitamins in Multivitamin Preparations by High-Performance Liquid Chromatography

An optimized method based on high-performance liquid chromatography with multiwavelength UV detection is proposed. The method provides the determination of vitamins B1 and B2, nicotinic acid, nicotinamide, pantothenic acid, folic acid, vitamins B6, B12, K3, H, D2, and D3, and vitamin A and E acetates in multivitamin preparations using two chromatographic procedures. Relative standard deviations for most of vitamins are 3–10%.     

Medicinal flowers. IV. Marigold. (2): Structures of new ionone and sesquiterpene glycosides from Egyptian Calendula officinalis

Following the characterization of hypoglycemic, gastric emptying inhibitory, and gastroprotective principles and the structure elucidation of calendasaponins A, B, C, and D, two new ionone glucosides (officinosides A and B), and two sesquiterpene oligoglycosides (officinosides C and D), were isolated from the flowers of Egyptian Calendula officinalis. The structures of the officinosides were elucidated on the basis of chemical and physicochemical evidence.     

Total syntheses of epothilones B and D

Total syntheses of the microtubule stabilizing antitumor drugs epothilone B and D are described, starting from optically pure (S)-malic acid and methyl (R)-3-hydroxy-2-methylpropionate. The synthesis is highly convergent by coupling the three fragments C1-C6 (fragment D), C7-C10 (fragment C), and C11-C21 (fragment B). Key steps are two stereoselective Wittig type olefinations to generate the 12,13- and 16,17-double bonds, an enantioselective Mukaiyama aldol addition to synthesize fragment D, and a sulfone anion allyl iodide alkylation to connect fragments B and C. Finally fragment D was attached to the B + C fragment via aldol addition.     

Magnetic properties of all-carbon graphene-fullerene nanobuds

The magnetic properties of proposed all-carbon graphene-fullerene nanobuds have been investigated through spin-polarized density functional theory. Four structures (A, B, C and D) are proposed in terms of the geometry, and analysis of the formation of new chemical bonds in the nanobuds is conducted. Cases A and B possess magnetic moments of nearly 6 μ(B), originating from unpaired spins due to the chemical bond formation from two next-nearest atoms in graphene. In Cases C and D, the connections of two atoms in different sublattices of graphene cannot generate unpaired spins, resulting in non-magnetic states. The magnetic nanobuds hold great promise for new spintronics and guide the controllable experimental synthesis of desired geometries.     

Use of isothermal microcalorimetry in pharmaceutical preformulation studies,Part I. Monitoring crystalline phase transitions

Solid-state transformation kinetics of two crystal forms of a synthetic tetrapeptide was monitored by isothermal microcalorimetry and complementary solid-state analytical techniques. Form B, the crystal form obtained from the synthetic process transformed to Form D upon exposure to higher relative humidity conditions (>60% RH). The transformation occurred rapidly at higher temperature, and relative humidities. An intermediate phase of very low crystallinity (amorphous-like phase) was observed when transformation was slow. Form D was observed to be physically stable at higher relative humidities and thus the preferred crystal form for development. Exposure of Form B to high relative humidity was the only process through which Form D was obtained. Optimal conditions for transformation of Form B to Form D were determined by microcalorimetric experiments and were used for larger scale processing of Form B to Form D.     

Taumycins A and B, two bioactive lipodepsipeptides from the Madagascar sponge Fascaplysinopsis sp

Two closely related lipodepsipeptides, taumycins A and B (1 and 2) have been isolated from the Madagascar sponge Fascaplysinopsis sp. The two compounds have the same 12-membered oxodepsipeptide ring system in common. Both were toxic to brine shrimp larvae, and taumycin A (1 microM), but not taumycin B, inhibited growth of the human UT-7 leukemic cell line. The structure of the two compounds, likely to be derived from microorganisms, was established by MS and 1D and 2D NMR data.     

Self-Inclusion Complexes Derived from Cyclodextrins: Synthesis and Characterization of 6(A),6(B)-Bis-O-[p-(allyloxy)phenyl]-Substituted beta-Cyclodextrins

The syntheses, structures, and spectroscopic properties of 6(A),6(B)-bis-O-[p-(allyloxy)phenyl]-substituted beta-cyclodextrins have been investigated. Selective activation of the 6(A),6(B)-hydroxy groups was carried out by treating heptakis(2,3-di-O-methyl)-beta-cyclodextrin (1) with 2,4-dimethoxybenzene-1,5-disulfonyl chloride to give 6(A),6(B)-bissulfonate ester 2 in a yield of only 3%. This material was treated with sodium p-(allyloxy)phenoxide in DMF to form 6(A),6(B)-bis-O-[p-(allyloxy)phenyl]-heptakis(2,3-di-O-methyl)-beta-cyclodextrin (3), which had two isomers. One (3A) has the two p-(allyloxy)phenyl arms directed away from the cyclodextrin cavity, and the other (3B) has one of the p-(allyloxy)phenyl groups through the cavity to form a self-inclusion complex. When either 3A or 3B was treated with methyl iodide and sodium hydride, the resulting permethylated 6(A),6(B)-bis-O-[p-(allyloxy)phenyl]heptakis(2,3-di-O-methyl)-6(C),6(D),6(E),6(F),6(G)-penta-O-methyl-beta-cyclodextrin (4) was composed of two isomers, in which 4B is a self-inclusion complex. 3A and 3B also can be converted into a mixture of 3A and 3B in strong base but not when melted in the absence of base. 4A and 4B do not isomerize. Detailed 1D and 2D NMR spectroscopic studies were carried out to characterize the structures of these new compounds, and molecular mechanics techniques were used to explain the experimental facts.     

Bilosespens A and B: two novel cytotoxic sesterpenes from the marine sponge Dysidea cinerea

[formula: see text] Two novel sesterpenes, bilosespens A and B (1 and 2) were isolated from the Red Sea sponge Dysidea cinerea collected in the Dahlak archipelago, Eritrea. The structure of the mixture of the two inseparable compounds was established by spectroscopic analysis, mainly by 1D and 2D NMR measurements. The mixture of bilosespens A and B is cytotoxic to a few human cancer cells.     

Determination of the rate of intramolecular exchange between two complex spin systems from the NMR spectra

Reversible 1,2-shifts of the ethyl group in the 9-ethyl-9, 10-dimethylphenanthrenonium ion lead to a reversible change of the ring hydrogen states (A′B′C′D′ ? A″B″C″D″). Line shape analysis for the determination of the exchange rate was performed for this case of intramolecular exchange between the two multi-spin systems. The calculations are based on density matrix formalism.     

Analysis of new benzo-di-lactones and quinones from Lysimachia Fordiana Oliv

Four pigments including two new skeleton benzo-di-lactones fordianin A (1) and fordianin B (2), and another two new quinones fordianaquinone A (3) and fordianaquinone B (4) were firstly isolated from the acetone extract of the leaves of Lysimachia fordiana Oliv. Their structures were elucidated on the basis of spectroscopic methods, mainly 1D and 2D NMR. These four new pigments were evaluated for cytotoxicity against the A549 (human lung cancer) and HeLa (human cervical carcinoma) cell lines.     

alpha-TEPHOS: a cyclodextrin-derived tetraphosphine for multiple metal binding

The tetraphosphine 6(A),6(B),6(D),6(E)-tetradeoxy-6(A),6(B),6(D),6(E)-tetra(diphenylphosphinyl)-2(A),2(B),2(C),2(D),2(E),2(F),3(A),3(B),3(C),3(D),3(E),3(F),6(C),6(F)-tetradeca-O-methyl-alpha-cyclodextrin (alpha-TEPHOS) has been prepared in high yield by reacting 6(A),6(B),6(D),6(E)-tetra-O-methylsulfonyl-2(A),2(B),2(C),2(D), 2(E),2(F),3(A),3(B),3(C),3(D),3(E),3(F),6(C),6(F)-tetradeca-O-methyl-alpha-cyclodextrin with excess PPh(2)Li. The product was purified in its BH(3)-protected form. alpha-TEPHOS is the first optically active tetraphosphine in which the four phosphine units are tethered to a cavity-shaped scaffold. When reacted with [AuCl(tetrahydrothiophene)], alpha-TEPHOS led to the corresponding tetragold complex [(alpha-TEPHOS)(AuCl)(4)] in which the four gold atoms are all located close to the primary face of the cyclodextrin. Reaction with [PdCl(o-C(6)H(4)CH(2)NMe(2))](2) gave the C(2)-symmetrical complex [(alpha-TEPHOS){PdCl(o-C(6)H(4)CH(2)NMe(2))}(4)]. Treatment of the ligand with two equiv. of [Rh(norbornadiene)(tetrahydrofuran)(2)]BF(4) afforded selectively the bimetallic complex [(alpha-TEPHOS){Rh(norbornadiene)}(2)](BF(4))(2) in which each metal centre is coordinated to two phosphorus atoms belonging to adjacent glucose units.     

Combined 1H, 13C and 11B NMR and mass spectral assignments of boronate complexes of D‐(+)‐glucose,D‐(+)‐mannose,methyl‐α‐D‐glucopyranoside,methyl‐β‐D‐galactopyranoside and methyl‐α‐D‐mannopyranoside

Complex formation between N‐butylboronic acid and D ‐(+)‐glucose, D ‐(+)‐mannose, methyl‐α‐D ‐glucopyranoside, methyl‐β‐D ‐galactopyranoside and methyl α‐D ‐mannopyranoside under neutral conditions was investigated by ¹H, ¹³C and ¹¹B NMR spectroscopy and gas chromatography–mass spectrometry (GC–MS) D ‐(+)‐Glucose and D ‐(+)‐mannose formed complexes where the boronates are attached to the 1,2:4,6‐ and 2,3:5,6‐positions of the furanose forms, respectively. On the other hand, the boronic acid binds to the 4,6‐positions of the two methyl derivatives of glucose and galactose. Methyl α‐D ‐mannopyranoside binds two boronates at the 2,3:4,6‐positions. ¹¹B NMR was used to show the ring size of the complexed sugars and the boronate. GC–MS confirmed the assignments. Copyright © 2003 John Wiley & Sons, Ltd.     

Xylocarpins A and B, two new mexicanolides from the seeds of a Chinese mangrove Xylocarpus granatum: NMR investigation in mixture

Xylocarpins A and B, two new mexicanolides with a tiglate group at C-3, have been identified in the mixture using NMR spectroscopy. Both compounds were isolated in the mixture from the seeds of a Chinese mangrove Xylocarpus granatum. The first complete assignments of 1H and 13C NMR data for these mexicanolides were achieved by means of 2D NMR techniques, including 1H-1H COSY, HSQC, HMBC and NOESY spectra. In order to separate xylocarpins A (1) and B (2) by chemical method, the mixture of two compounds was reduced with sodium borohydride in anhydrous methanol. However, the reduction led to the opening of the delta-lactone ring in xylocarpin B and afforded compound 3 as the main product. The complete NMR assignments of compound 3 were also achieved by means of the above 2D NMR techniques. Moreover, xylocarpin A was easily transformed into xylocarpin B during our normal liquid column chromatography. From this point of view, xylocarpin A was deemed to be the genuine natural product and xylocarpin B might be an artifact.     

Kinetics of a second order reaction involving two intermediate second order reactions

We have studied the kinetics of a reaction in which starting materials A and B react to form the products C and D directly, as well as by way of two additional intermediate reactions. In the first intermediate reaction, A and C react to form D and E, and in the second intermediate reaction, B and E react to form 2C. There are three conservation laws, which effectively reduce the number of variables to two, resulting in nonlinear coupled first order differential equations for [A](t) and [B](t). These equations are readily solved by standard numerical procedures, for various values of the relative reaction rates and starting concentrations. Our results are used to fit experimental data for the case in which A and B are 1-acetyl-4-(1-ethoxycarbonyl-1-cyano)methylene-1,4-dihydroquinoline and water, for which the first and third reverse reactions can be neglected.     

Ligands rock & roll: stepwise twisting of two cis-coordinated lopsided N-heterocycles in an octahedral bis(2-phenylazopyridine)-ruthenium(II) complex with seven atropisomers

1H NMR data of alpha-[Ru(azpy)2(MeBim)2](PF6)2 (azpy=2-phenylazopyridine, MeBim=1-methylbenzimidazole), 2, revealed the presence of a total of seven atropisomers at -95 degrees C: three head-to-tail, HT, isomers (A, C, and D), and four head-to-head, HH, isomers which, due to the presence of an intrinsic C2 axis in the alpha-[Ru(azpy)2] moiety, are two sets of identical pairs (B/B and E/E). The NMR data of 2 represent a unique example of a coordination compound that shows a variable temperature (VT) behavior with more, well-defined steps of slow-to-fast exchange of its atropisomers. At 65 degrees C, all atropisomers are in fast exchange; on lowering the temperature the sharp signals first broaden (at room temperature) and consecutively split up into two sets of relatively sharp signals, in slow exchange, at about 0 degrees C (D, 40 %, and the coalesced signals of ABBCEE, 60 %). Upon further cooling, the set of peaks belonging to D remain sharp until the lowest recording temperatures. The signals of the other set of resonances, on the other hand, first broaden again and then separate into two sets of broad peaks (C/E/E and A) and one set of sharp peaks (B and B in fast exchange); on lowering the temperature even more, these signals broaden once again and finally, at -95 degrees C, are split up into a total of four sets of signal (A, B/B, C, and E/E). At low temperatures, ROESY experiments revealed that atropisomerization occurs through the synchronous rotation of both MeBim ligands in the interconversion of the two "identical" HH atropisomers B and B, as well as in the interconversion between C and E/E. The HH rotamers B/B furthermore exhibit a slow-to-fast exchange atropisomerization behavior that is observed independently from the other dynamic processes in this compound. The versatile cis bifunctional binding of the DNA model bases (MeBim ligands) in 2 parallels the observation of alpha-[Ru(azpy)2Cl2] which shows extraordinarly high cytotoxicity against tumor cell lines.     

Two New Norsesquiterpenes from Ixeris polycephala

The whole herb of Ixeris polycephala is used for treatment of appendicitis, measles, and larynx paining1. However its chemical constituents were not reported until now. From the title plant collected in Gansu Province, we found two new norsesquiterpenes b…     

The structure of new lignans from the seeds of phytolacca americana

From the seeds of Phytolacca americana two new lignans, Americanin B and D, have been isolated and their structures elucidated mainly by spectroscopic methods     

Sulfur-containing and dimeric flavanols from Glycosmis montana

Two novel sulfur-containing flavanols, glymontanines A and B, and two new flavanol dimers, montahomobisflavans A and B, were isolated from the twigs and leaves of Glycosmis montana. Their structures were elucidated by spectroscopic methods including 2D NMR analysis.     

DFT Study on Two C4N12O4 Isomers with Pagodane- and Isopagodane-like Structures

1 INTRODUCTION Pagodane (Fig. 1) first synthesized[1] in 1983 has been studied by Prinzbach and coworkers for more than twenty years[2, 3]. Described as a waxy solid melting without decomposition and stable to at least 600 ℃ in gas phase, pagodane is interesting for its exotic structure and as an introduction to the family of substituted dodecahedranes[2]. Owing to its unu- sual structure, pagodane has provided experimenters and theorists with a challenge to characterize and cal- culate …