The structures of vepridimerines A-D,four new dimeric prenylated quinolone alkaloids from Vepris lousii and Oricia renieri (Rutaceae)

Four new isomeric dimeric prenylated quinolone alkaloids, vepridimerines A-D, have been isolated from the bark of Vepris louisii and Oricia renieri (Rutaceae) and have been assigned structures (2)–(5) respectively on the basis of spectroscopic evidence, in particular¹H and¹³C n.m.r. data.     

Infrared and mass spectra of purine and substituted dihydropurines

Infrared spectra (potassium bromide) of purine, 7 (9)-deuteriopurine, 6-deuteriopurine, 8-deuteriopurine and a number of substituted dihydropurines are presented. The latter compounds are the 6-α-hydroxyalkyl-1,6 (or 3,6)dihydropurines formed by photoaddition of the respective alcohols to purine (4-6). From the comparative spectra of purine and its mono-deuterated derivatives, it is possible to make assignments of N-H and N-D stretching vibrations and tentative assignments of C-H deformation modes. The spectra of the substituted dihydropurines show evidence of interesting hydrogen-bonding interactions which are demonstrated most clearly in the distinct differences between the spectra of the diastereomeric purine-ethanol adducts. Mass spectra of these compounds all indicate progressive scission of HCN molecules from the principal radical-ion. In the case of the photo-adducts, HCN scission is preceded by scission at the site (i.e. 6-position) of alcohol addition to the purine ring.     

Use of surface charges from DFT calculations to predict intestinal absorption

A model for prediction of percent intestinal absorption (%Abs) of neutral molecules was developed based upon surface charges of the molecule calculated by density functional theory (DFT). The surface charges are decomposed into sigma moments which are correlated to a partition coefficient representing transfer of the molecule between water and the epithelial membrane. The model was built and tested using a data set of 241 drugs. It achieved an RMS deviation of 13% on a training set of 38 compounds as well as on a test set of 107 drugs for which the experimental data were classified as high quality. Property maps of the molecule, depicting which atoms contribute to or hinder absorption, are produced to aid drug design.     

The structure of tamariscol,a new pacifigorgiane sesquiterpenoid alcohol from the liverwort frullania tamarisci

Tamariscol, a new sesquiterpenoid alcohol with the rare pacifigorgiane carbon skeleton, is a major constituent of the liverwort $\text{Frullania tamarisci}$, collected in Scotland. It has been assigned the structure and relative configuration (1) on the basis of ¹³C (including 2D INADEQUATE) and ¹H nmr spectroscopic evidence.     

Quantitative Tortuosity Measurements of Carbonate Rocks Using Pulsed Field Gradient NMR

Transport in Porous Media - Tortuosity is an important physical characteristic of porous materials; for example, it is a critical parameter determining the effective diffusion coefficient dictating...