Methyl 4-Carbomethoxy-3-Hydroxy-5-Methyl-Phenyl-Acetoacetate from the Disilylated Dianion of Methyl Acetoacetate

Recently, Chaley and Chan¹ reported a novel synthesis of methyl olivetolate (3a) from the annelation of 1,3-bis(trimethylsiloxy)-1-methoxybuta-1,3-diene (1) with the acid chloride 2a and titanium tetrachloride at room temperature. In view of their success, we attempted to apply this methodology for a convenient synthesis of isotopically labelled orsellinic acid in order to unravel its biosynthesis to cyclopentanoids.     

On the generation of transient acoustic pulses in water

This paper discusses a method for finding the input voltage to a ceramic transducer, in water, that will produce a predetermined pressure signature. For a given pressure signature and a given transducer, the required voltage is derived via the Fast Fourier Transform technique. This voltage is generated with a digital synthesizer and applied to the transducer. The corresponding measured radiated pressure agress, fairly well, with the expected result.     

Trichodermadiene: a new trichothecene

A new trichothecene, trichodermadiene ($\text{3}$), possessing a dienic ester side chain has been isolated and characterized.     

Stereoselective Nazarov cyclizations of bridged bicyclic dienones

[reaction: see text] Bridged bicyclic dienones underwent silyl-directed Nazarov cyclization with generally very high diastereoselectivity. In most cases, a strong preference for cyclization to the product with an exo-disposed cyclopentenone was seen. However, the presence of additional unsaturation in the three-carbon bridge of a bicyclo[3.2.1]octadiene system caused complete reversal in selectivity with exclusive formation of the endo-cyclopentenone. The observed selectivities are believed to result from a combination of steric and electronic effects.     

Der Satz von der Zerlegung Finslerscher Zahlen in Primfaktoren

Ohne Zusammenfassung     

13C NMR investigation of tautomeric and acid-base equilibria of pyrazolone T and three analogs

Pyrazolone T and three derivatives have been characterized by ¹³C and, in part, ¹⁵N nmr at several pH values. The ¹³C chemical shifts have been assigned at, or near, the equivalence points and pK_a values of these four compounds. Closely situatued quaternary carbon signals were assigned by means of a heteronuclear chemical shift correlation (FLOCK) experiment which is sensitive to, and was optimized for, 3-bond C-H couplings. The ¹³C chemical shift data indicate the existence of both tautomeric and acid-base equilibria and demonstrate that the four congeners exist in surprisingly different forms at certain common pH values.     

Preparative separation of isomeric 2-(2-quinolinyl)-1H-indene-1,3(2H)-dione monosulfonic acids of the color additive D&C Yellow No. 10 (quinoline yellow) by pH-zone-refining counter-current chromatography

The main components of the color additive D&C Yellow No. 10 (Quinoline Yellow, Color Index No. 47005), 2-(2-quinolinyl)-1H-indene-1,3(2H)-dione-6'-sulfonic acid (6SA) and 2-(2-quinolinyl)-1H-indene-1,3(2H)-dione-8'-sulfonic acid (8SA), were isolated from the dye mixture by pH-zone-refining counter-current chromatography (CCC) in the ion-exchange mode. These positional isomers were separated from a portion of dye using sulfuric acid as the retainer acid and dodecylamine as the ligand (ion exchanger). The added ligand enhanced the partitioning of the hydrophilic components in the organic stationary phase of the two-phase solvent system that consisted of isoamyl alcohol-methyl tert.-butyl ether-acetonitrile-water (3:1:1:5). Thus, separation of 1.8 g of D&C Yellow No. 10 using the above method resulted in 0.6 g of 6SA and 0.18 g of 8SA of over 99% purity. The isolated compounds were characterized by mass spectrometry and proton nuclear magnetic resonance with correlated spectroscopy assignments. The study exemplifies a new field of applications for pH-zone-refining CCC, to the separation of positional isomers of strongly hydrophylic compounds containing sulfonic acid groups.     

Fluctuations in the ensemble of reaction pathways

The dominant reaction pathway is a rigorous framework to microscopically compute the most probable trajectories, in nonequilibrium transitions. In the low-temperature regime, such dominant pathways encode the information about the reaction mechanism and can be used to estimate nonequilibrium averages of arbitrary observables. On the other hand, at sufficiently high temperatures, the stochastic fluctuations around the dominant paths become important and have to be taken into account. In this work, we develop a technique to systematically include the effects of such stochastic fluctuations, to order k(B)T. This method is used to compute the probability for a transition to take place through a specific reaction channel and to evaluate the reaction rate.     

Preparative separation of 1,3,6-pyrenetrisulfonic acid trisodium salt from the color additive D&C Green No. 8 (pyranine) by pH-zone-refining counter-current chromatography

In developing analytical methods for batch certification of the color additive D&C Green No. 8 (G8), the U.S. Food and Drug Administration needed the trisodium salt of 1,3,6-pyrenetrisulfonic acid (P3S) for use as a reference material. Since P3S was not commercially available, preparative quantities of it were separated from portions of a sample of G8 that contained ～3.5% P3S. The separations were performed by pH-zone-refining counter-current chromatography using dodecylamine (DA) as the hydrophobic counterion. The added DA enabled partitioning of the polysulfonated components into the organic stationary phase of the two-phase solvent system used, 1-butanol-water (1:1). Thus, a typical separation that involved 20.3g of G8, using sulfuric acid as the retainer acid and 20% DA in the stationary phase and 0.1M sodium hydroxide as the mobile phase, resulted in ～0.58 g of P3S of greater than 99% purity. The identification and characterization of the separated P3S were performed by elemental analyses, proton nuclear magnetic resonance, high-resolution mass spectrometry, ultra-violet spectra, and high-performance liquid chromatography.     

High resolution 3-D shapes of fish schools: A new method to use the water column backscatter from hydrographic MultiBeam Echo Sounders

The Multi-Beam Echo Sounder (MBES) is a tool that allows getting information about bathymetric, morphological and compositional characteristics of the seabed surface. Although this is still one of the most important features in hydrography, MBES can now also discriminate the acoustic imaging of the water mass by recording sampled reflectivity measurements along each beam. In this paper, two MBES, namely the Kongsberg Simrad EM3002D (300 kHz) and the Reson Seabed8125-H (455 kHz), which are generally employed to study seafloor characteristics, have been used for the identification of fish schools in the water column at very high resolution. In particular, a methodology to identify and analyse fish schools through the Water Column Backscatter (WCB) is presented. This methodology made it possible to obtain a wide variety of fish schools shape in 3-D (in our case, anchovies and sardines), which allowed a first study on the ecological behaviour of the schools according to their shape. All data were collected along with Kongsberg Simrad EK60 scientific echo sounder, allowing also a comparison of different approaches to fish schools identification. The data presented in this paper were collected during two oceanographic surveys within the project MEDIAS (MEDiteranean International Acoustic Survey), Ancheva 2010 and Ancheva 2011. Beyond the mere visualization of school shapes, we also attempted to gain numerical values of the school volumes and to realize a more detailed study of anchovies and sardines school shapes. In line with the current literature, this study showed that there are three main factors influencing the shape of a school, namely the depth of the bottom, the time of the day when data are acquired and the density of individuals in the investigated area.