A dimethylzinc/diphenylphosphinoylimine approach to the asymmetric synthesis of the calcimimetic agent NPS R‐568

An asymmetric synthesis of the calcimimetic agent NPS R‐568 using a (1R,2S)‐N‐benzylephedrine‐promoted addition of dimethylzinc to a diphenylphosphinoylimine derived from 3‐methoxybenzaldehyde is described. The enantiomeric ratio of the key amine fragment was determined to be 93:7 (86% ee), favoring the (R)‐enantiomer by derivatization and chiral stationary phase HPLC analysis. Copyright © 2010 John Wiley & Sons, Ltd.     

Quantification of piperine in different varieties of Piper nigrum by a validated high-performance thin-layer chromatography‒densitometry method

JPC – Journal of Planar Chromatography – Modern TLC - Piperine is the most important alkaloid molecule present in Piper nigrum. In this study, a simple, rapid, quantitative...     

Iodine-Methanol Induced Novel Fragmentation of Bicyclic Diones to Anisole Derivatives

The cyclic diones (1), (5), (8) and (11) on treatment with iodine and methanol underwent fragmentation yielding the anisole derivatives (4), (6), (9) and (12) respectively.     

Microwave‐assisted synthesis,spectroscopy and biological aspects of binuclear titanocene chelates of isatin‐2,3‐bis(thiosemicarbazones)

The reactions of bis(cyclopentadienyl)titanium(IV) chloride with a new class of bis(thiosemicarbazones) (H₂L), derived by condensing isatin with different N(4)‐substituted thiosemicarbazides, have been studied both by a conventional stirring method and also using microwave technology. Binuclear products of type [{(η⁵‐C₅H₅)₂TiCl} ₂(L)] have been isolated in both cases. Tentative structural conclusions are drawn for the reaction products based upon analysis, electrical conductance, magnetic moment and spectral (UV‐visible, IR, ¹H NMR and ¹³C NMR) data. FAB mass spectra of these compounds were also recorded to confirm the binuclear structures. Studies were conducted to assess the growth inhibiting potential of the ligands and complexes against various fungal, viral and bacterial strains. Copyright © 2008 John Wiley & Sons, Ltd.     

Imaging elastic property of surfaces at nanoscale using atomic force microscope

We present a simple technique to characterize and image the distribution of local elastic property using ultrasonic atomic force microscope (UAFM). We interpret the UAFM images using simple arguments. We have demonstrated the capability of the UAFM technique to image the distribution of the local elastic property of the sample surface and semi-quantitatively map the local stiffness of the sample surface using a few selected samples. The local stiffness of the sample surface was obtained by measuring the changes in the frequency of contact resonance peak values and could verify the same using force-distance measurement at the same regions on the sample surface.     

Vitrification,relaxation and free volume in glycerol–water binary liquid mixture: Spin probe ESR studies

Glass transition and relaxation of the glycerol–water (G–W) binary mixture system have been studied over the glycerol concentration range of 5–85 mol% by using the highly sensitive technique of electron spin resonance (ESR). For the water rich mixture the glass transition, sensed by the dissolved spin probe, arises from the vitrified mesoscopic portion of the binary system. The concentration dependence of the glass transition temperature manifests a closely related molecular level cooperativity in the system. A drastic change in the mesoscopic structure of the system at the critical concentration of 40 mol% is confirmed by an estimation of the spin probe effective volume in a temperature range where the tracer reorientation is strongly coupled to the system dynamics.     

Aromatic motifs in the design of Ephedra ligands for application in the asymmetric addition of diethylzinc to aldehydes and diphenylphosphinoylimines

Using N-benzylephedrine as a model, a collection of N-arylmethylephedrine derivatives has been prepared. These derivatives were prepared by treatment of ephedrine with selected aldehydes to create oxazolidines 8a–e. Reduction of the oxazolidines with lithium aluminum hydride afforded the target β-amino alcohols 9a–e. When applied in the catalytic asymmetric addition of diethylzinc to aldehydes and diphenylphosphinoylimines, the derivatives yielded product enantioselectivities that were comparable to those of N-benzylephedrine. An N-cyclohexylmethylephedrine derivative was also prepared; this β-aminoalcohol did not perform well in the catalytic addition of diethylzinc to 2-naphthaldehyde, thus suggesting that the aromatic motif is important in terms of maintaining a reasonable level of asymmetric induction. Finally, N-benzyl-N-methyl-2-amino-1,2-diphenyl-1-ethanol, an analogue of the N-benzylephedrine derivative, was prepared. This compound yielded comparable enantioselectivities in the catalytic asymmetric addition when employed as a ligand.