Highly enantioselective mukaiyama aldol reactions catalyzed by a chiral oxazaborolidinium ion: total synthesis of (-)-inthomycin C

A cationic oxazaborolidinium-catalyzed asymmetric Mukaiyama aldol reaction of (1-methoxy-2-methyl-propenyloxy)-trimethylsilane with various aldehydes including α,β-disubstituted acroleins has been developed in high yields and enantioselectivities. The synthetic utility of this methodology was demonstrated in the first short synthesis of naturally occurring inthomycin C in high enantiopurity.     

On the temperature dependent frequency factor in thermoluminescence

In thermoluminescence (TL), frequency factor might not always be temperature independent. In the present article we consider a method of two heating rates for evaluation of temperature exponent for the case of temperature dependent frequency factor in TL. The method has been analysed by applying it both to numerical and experimental TL peaks.     

Fabrication of polyindene and polyindole nanostructures

One-dimensional (1D) nanostructures of fused ring polymeric systems: polyindene (PIn) and polyindole (PInd) were fabricated onto glass substrates using a chemical vapor deposition (CVD) method. Morphology of fabricated PIn and PInd structures studied using Olympus microscope reveals formation of 1D straight tubular, smooth and fluorescent nanostructures. The results obtained were further correlated with scanning electron microscopic (SEM) studies of PIn and PInd nanostructures, indicating appearance of fine nanothread entangled network (having diameter ∼ 50 nm) for PIn, and well-defined, straight and aligned nanotubes (having diameter ∼ 60 nm) for PInd. A comparative study on the morphology/dimensions of fabricated PIn and PInd nanostructures with the nanosized PIn and PInd structures obtained by oxidative synthetic routes is also discussed. The structural composition of fabricated PIn and PInd nanostructures is confirmed by Fourier transform infrared (FTIR) spectroscopy, thereby indicating existence of all infrared markers corresponding to the characteristic bands present in PIn and PInd. The study suggests that the fabricated PIn and PInd nanodimensional structures may find potential applications in the field of nanotechnology.     

A conjecture on the lengths of filling pairs

Geometriae Dedicata - A pair $$(\alpha , \beta )$$ of simple closed geodesics on a closed and oriented hyperbolic surface $$M_g$$ of genus g is called a filling pair if the complementary components...     

Determination and correlation of heavy atom positions in the derivatives used in the X-ray analysis of ribonuclease A at 2.5 Å resolution

The analysis of four heavy atom derivatives of ribonuclease A is described leading to isomorphous phasing at 2.5 resolution. Differences in the characteristics of the derivatives are discussed with respect to the determination of their heavy atom parameters and the correlation of sites between derivatives to produce a self consistent set. The criteria used to ensure consistency are described. In the final phase analysis using refined heavy atom parameters the least squaresR factors of the derivatives were .124, .143, .101, and .067 respectively, and the mean figure of merit for the 3444 observed reflexions was 0.66.In recognition of C. H. Carlisle's pioneering work in this field.     

Exact energy eigenvalues for the doubly anharmonic oscillator

The exact energy eigenvalues for the potentialV(r) = 1/2 ² r ² + 1/4r⁴ +1/6 r⁶ and the conditions for their occurrence have been determined.     

Crystal and molecular structure ofp-aminobenzene sulfonacetamide sodium [sulfacetamide sodium] monohydrate

The crystal and molecular structure ofp-aminobenzene sulfonacetamide sodium, C₈H₉N₂NaO₃S·H₂O, an important substituted sulfa drug, has been determined from diffractometric data using MoK radiation. The crystals are monoclinic, witha=6.614(2),b=23.788(6),c=7.012(2) Å,=103.13(2)°, and space groupP2₁/c. The structure was solved by the heavyatom method, and refined by full-matrix least squares to a finalR value of 0.040 with 1435 unique reflections. In packing, the molecules form dimers through pairs of N-HN and N-HO hydrogen bonds. The molecules are further stabilized by O-HO and O-HN hydrogen bonds.