A concise synthetic approach to the sorbicillactones: total synthesis of sorbicillactone A and 9-epi-sorbicillactone A

A concise (12 step) total synthesis of sorbicillactone A and 9-epi-sorbicillactone A is reported. Unlike typical routes to the sorbicillinoids, this strategy does not start from sorbicillin and allows for the production of the bicyclic core on a multigram scale. The intramolecular conjugate addition of a tethered malonate serves as an effective means of introducing the lactone ring and provides a synthetic handle for installing the amide nitrogen.     

Fixed points and graph images for minimal maps on the once punctured torus

A fixed point detection theorem for a family of maps defined on the once punctured torus is proved. As a consequence, we produce an example of a homotopy class [f] of self-maps on the once punctured torus that illustrates the following: (i) there is a map in the homotopy class that has no fixed points, and (ii) if the image of f lies in a 1-complex that embeds as a homotopy equivalence, then f must have a fixed point.     

Acetic acid-confined synthesis of uniform three-dimensional (3D) bismuth telluride nanocrystals consisting of few-quintuple-layer nanoplatelets

High-selectivity, uniform three-dimensional (3D) flower-like bismuth telluride (Bi(2)Te(3)) nanocrystals consisting of few-quintuple-layer nanoplatelets with a thickness down to 4.5 nm were synthesized for the first time by a facile, one-pot polyol method with acetic acid as the structure-director. Micrometre-sized 2D films and honeycomb-like spheres can be obtained using the uniform 3D Bi(2)Te(3) nanocrystals as building blocks.     

Antioxidant capacity and larvicidal and antifungal activities of essential oils and extracts from Piper krukoffii

The leaves and twigs of Piper krukoffii, collected in the Carajás National Forest, north Brazil, yielded essential oils (2.0% and 0.8%), the main constituents of which were myristicin (40.3% and 26.7%), apiole (25.4% and 34.1%) and elemicin (2.8% and 3.0%). The antioxidant activities of the oils, methanol extract and its sub-fractions were evaluated. The DPPH EC50 values varied from the ethyl acetate sub-fraction (73.4 +/- 3.7 microg/mL) to the methanol extract (24.9 +/- 0.8 microg/mL), and the ABTS TEAC values ranged in the same order from 265.7 to 349.2 microMol TE/g. These results indicated a significant antioxidant activity for the plant. The lignans (-)-kusunokin, yatein, (-)-hinokin and cubebin were identified in the methanol extract. The hydro-methanolic sub-fraction showed a high value for total phenol content (106.5 +/- 0.7 mg GAE/g), as well as 1H NMR signals for sugar moieties. Crude extracts and sub-fractions were also able to inhibit beta-carotene bleaching, varying from 22.4 to 47.1%. The oils from the leaves and twigs showed strong larvicidal (21.4 and 3.6 microg/mL) and fungicide (0.5 and 0.1 microg/mL) activities.     

Variability in the Chemical Composition of Myrcia sylvatica (G. Mey) DC. Essential Oils Growing in the Brazilian Amazon

Myrcia sylvatica (G. Mey) DC. is known as “insulin plant” because local communities use the infusions of various organs empirically to treat diabetes. The leaves of seven specimens of Myrcia sylvatica (Msy-01 to Msy-07) were collected in the Brazilian Amazon. Furthermore, the essential oils were extracted by hydrodistillation and analyzed by gas chromatography coupled to mass spectrometry, and their chemical compositions were submitted to multivariate analysis (Principal Component Analysis and Hierarchical Cluster Analysis). The multivariate analysis displayed the formation of four chemical profiles (chemotypes), described for the first time as follows: chemotype I (specimen Msy-01) was characterized by germacrene B (24.5%), γ-elemene (12.5%), and β-caryophyllene (10.0%); chemotype II (specimens Msy-03, -06 and -07) by spathulenol (11.1–16.0%), germacrene B (7.8–20.7%), and γ-elemene (2.9–7.6%); chemotype III (Msy-04 and -05) by spathulenol (9.8–10.1%), β-caryophyllene (2.5–10.1%), and δ-cadinene (4.8-5.6%); and chemotype IV, (Msy-02) by spathulenol (13.4%), caryophyllene oxide (15.0%), and α-cadinol (8.9%). There is a chemical variability in the essential oils of Myrcia sylvatica occurring in the Amazon region.     

Consistency of post-Newtonian waveforms with numerical relativity

General relativity predicts the gravitational wave signatures of coalescing binary black holes. Explicit waveform predictions for such systems, required for optimal analysis of observational data, have so far been achieved primarily using the post-Newtonian (PN) approximation. The quality of this treatment is unclear, however, for the important late-inspiral portion. We derive late-inspiral waveforms via a complementary approach, direct numerical simulation of Einstein's equations. We compare waveform phasing from simulations of the last approximately 14 cycles of gravitational radiation from equal-mass, nonspinning black holes with the corresponding 2.5PN, 3PN, and 3.5PN orbital phasing. We find phasing agreement consistent with internal error estimates for either approach, suggesting that PN waveforms for this system are effective until the last orbit prior to final merger.     

A six-coordinate aryl-germanium complex formed by the Kläui ligand

PhGeCl₃ reacts with Na{[OP(OEt)₂]₃CoCp} to give the six-coordinate complex PhCl₂Ge{[OP(OEt)₂]₃CoCp}, characterised spectroscopically and by an X-ray crystal structure determination which showed a firmly-attached tridentate ligand [Ge-O 1.973(2) Å].     

Regioselective synthesis of 2,4,6-triaminopyridines

A regioselective synthesis of 2,4,6-trisubstituted pyridine is described starting from 2,6-dibromo-4-nitropyridine. All three different regioisomers of the 2,4,6-triamino substituted pyridine have been synthesized in four to five steps. The method described is a general route to unsymmetrical 2,4,6-trisubstituted amino pyridines.     

Finite-aperture effects for Fourier transform systems with convergent illumination. Part I: 2-D system analysis

The Optical Fourier Transform (OFT) is one of the most fundamental operations in analogue Optical Signal Processing (OSP). There are many optical arrangements for implementing the OFT, however one which is particularly popular is the Scaled Optical Fourier Transform (SOFT) because it offers the user the ability to scale the output Fourier distribution. In this paper we study some of the practical limits introduced by using a converging spherical lens of finite aperture to produce the illuminating field in the implementation of the SOFT. By deriving simple rules of thumb, based on examining phase and intensity deviations from the ideal unapertured case, we define an area inside the geometric shadow, which we refer to as a sub-geometric shadow. Inside this sub-geometric shadow we show that the worst-case errors in the resulting SOFT, arising due to diffraction, can be quantified and avoided.