Sylvatine,a new alkamide from Piper sylvaticum roxb. (Piperaceae)

The structure of sylvatine (1), a new alkamide from Piper sylvaticum, has been elucidated from spectroscopic studies, chemical reactions and correlation with compounds of known structures.     

Revealing the order of a vortex through its intensity record

We show that the intensity distribution of an optical vortex contains information of its order. Specifically, the number of dark rings in the Fourier transform of the intensity is found to be equal to the order of the vortex. Based on this property and the orthogonality of Laguerre polynomials, we demonstrate the feasibility of an experimental technique for determining the order of optical vortices. It shows the beauty of going to complementary spaces, which has been employed earlier also to find the information not available in other domains.     

Olefin epoxidation with tert-butyl hydroperoxide catalyzed by functionalized polymer-supported copper(II) Schiff base complex

Abstract  

A new polymer-supported Cu(II) Schiff base complex has been synthesized and characterized by elemental (including metal) analysis, FT-IR spectroscopy, UV–Vis diffuse reflectance spectroscopy, thermogravimetric analysis, and scanning electron microscopy. The catalytic performance of this complex was evaluated in the epoxidation of styrene in acetonitrile/N,N-dimethylformamide (9:1) mixture with 70% tert-butyl hydroperoxide as an oxidizing agent under liquid phase reaction conditions for selective synthesis of styrene oxide. Suitable reaction conditions have been optimized by considering the effects of various reaction parameters such as temperature, reaction time, solvent, oxidant, catalyst amount, and styrene to hydroperoxide molar ratio for the maximum conversion of styrene as well as selectivity of styrene oxide. We have also investigated the epoxidation reaction of various olefins under the optimized reaction conditions. Comparison between catalytic activities of the polymer-supported Cu(II) Schiff base complex and its homogeneous analogue showed that the polymer-supported catalyst was more active. This heterogeneous complex was reused for five times. The selectivity of the heterogeneous catalyst does not change even after five times of reusing.     

Maximal Distance Travelled by N Vicious Walkers Till Their Survival

We consider N Brownian particles moving on a line starting from initial positions \(\mathbf{{u}}\equiv \{u_1,u_2,\ldots u_N\}\) such that \(0 . Their motion gets stopped at time \(t_s\) when either two of them collide or when the particle closest to the origin hits the origin for the first time. For \(N=2\) , we study the probability distribution function \(p_1(m|\mathbf{{u}})\) and \(p_2(m|\mathbf{{u}})\) of the maximal distance travelled by the \(1^{\text {st}}\) and \(2^{\text {nd}}\) walker till \(t_s\) . For general N particles with identical diffusion constants \(D\) , we show that the probability distribution \(p_N(m|\mathbf{u})\) of the global maximum \(m_N\) , has a power law tail \(p_i(m|\mathbf{{u}}) \sim {N^2B_N\mathcal {F}_{N}(\mathbf{u})}/{m^{\nu _N}}\) with exponent \(\nu _N =N^2+1\) . We obtain explicit expressions of the function \(\mathcal {F}_{N}(\mathbf{u})\) and of the N dependent amplitude \(B_N\) which we also analyze for large N using techniques from random matrix theory. We verify our analytical results through direct numerical simulations.     

A novel intramolecular arene-alkene photocycloaddition in 2-alkenyl naphtha-4-chromanones—a short route to functionalised multicyclic systems

On irradiation, 2-methyl-2-ethenyl naphtha-4-chromanone 1 undergoes an unusual intramolecular arene-alkene photocyclisation, followed by rearrangements to give a [5.3.1.0^6,1]benzotricycloundecene, 5.     

Enzymatic synthesis of optically active amino acids. Effect of solvent on the enantioselectivity of lipase-catalysed ring-opening of oxazolin-5-ones.

Reaction medium plays an important role in governing the enantioselectivity of the lipase-catalysed ring opening of 4-substituted-2-phenyl-oxazolin-5-ones.     

Biosynthesis of furanochromones in Pimpinella monoica

During a search for bioactive compounds from indigenous plants,Pimpinella monoica (Umbelliferae) was found to contain furocoumarin, isopimpenellin (3) and five biogenetically related furocoumarins viz khellin (1), visnagin (2), visamminol (4), ammiol (5) and khellol (6). Labelled (i) and (2) were isolated from [1−¹⁴C]- and [2−¹⁴C]-acetates. Labelling pattern, determined by degradation of biosynthesised compounds, establishes the polyketide origin of their aromatic and pyrone rings while the furan ring originates via an acetate-mevalonate pathway. The plant also utilises glycine and leucine as substratevia acetate. Biotransformation of [3−³H]-visnagin to (6) but not to (2) was also observed.     

The nature of molecular beam epitaxial growth examined via computer simulations

Man-made synthetic structures involving epitaxially grown thin films of one or more compound semiconductors have been finding an increasingly important role in semiconductor device technology.¹ Remarkable advances have been made over the past decade in the realization of a variety of such structures involving III-V, II-VI. and IV-VI compound semiconductors, as well as combinations of semiconductors with dielectrics and metals.' The major part of this progress has come about primarily due to the advent of, and refinements in, two vapor phase growth techniques — molecular beam epitaxy (MBE)' and metal-organic chemical vapor deposition (MO-CVD).³ The underlying motivation has been the remarkably altered and potentially useful electronic and optical properties of electrons, holes, and light arising from their confinement in a quasi-two-dimensional environment in the ultrathin films (thickness less than the particle deBroglie wavelength).⁴ However, confinement of the par- ticles in such ultrathin layers (typically 10 to 200 Å) places stringent requirements on the atomic level structural and chemical perfection of the films and their interfaces involved. At the same time, spatial control of the abruptness (in the growth direction) and uniformity (in the planes normal to the growth direction) of dopant distribution becomes equally sig- nificant in realizing the potential electrical and optical properties of camers and light in such structures. Both MBE and MO-CVD have been shown to meet these stringent requirements for the growth of III-V compound semiconductors, although differences between materials and structures produced by these techniques also remain. The purpose of this article is to review the progress made in understanding the process of MBE growth with particular focus on computer simulations of the growth proess.^1–15 These simulations have provided con- siderable insight into the role played by the atomistic surface kinetic processes in controlling the morphology of the growing surfaces and consequently the resulting nature of the interfaces formed upon deposition of another material on such surfaces.