Absolute configuration, predominant conformations, and vibrational circular dichroism spectra of enantiomers of n-butyl tert-butyl sulfoxide.

Alkylation of the alpha-carbanion of (R)-(-)-tert-butyl methyl sulfoxide (4) with n-propyl bromide afforded (+)-n-butyl tert-butyl sulfoxide (1) to which the absolute configuration (R) was ascribed. This assignment was confirmed by X-ray analysis of the complex 6 obtained from the enantiomerically pure sulfoxide (-)-1 and mercury chloride. Vibrational absorption and circular dichroism spectra of (+)-1 were measured in CDCl3 solution in the 2000-900 cm(-1) region and compared with the ab initio predictions of absorption and VCD spectra obtained with density functional theory using the B3LYP/6-31G basis set for different conformers of (R)-1. This comparison indicated also that (+)-1 is of the (R)-configuration.

X-ray and 13C solid-state NMR studies of N-benzoyl-phenylalanine.

A crystalline sample of N-benzoyl-DL-phenylalanine 1 and a polycrystalline sample of N-benzoyl-L-phenylalanine 2 were studied using 13C high-resolution solid-state NMR spectroscopy. The X-ray structure of the DL form was established. Sample 1 crystallizes in a monoclinic form with a P21/c space group, a=11.338(1) A, b=9.185(1) A, c=14.096(2) A, beta=107.53(3) degrees, V=1400(3) A3, Z=4 and R=0.053. The principal elements of the 13C chemical shift tensors deltaii for 1 and 2, selectively 13C (99%) labeled at the carboxyl groups were calculated. On the basis of 13C (delta)ii analysis the hydrogen bonding pattern for sample 2 was deduced. Enriched samples were used to establish the intermolecular distance between chemically equivalent nuclei for 1 and spatial proximity in heterogeneous domain for 2, employing the ODESSA pulse sequence. The consistence of the complementary approach covering X-ray data, analysis of the 13C (delta)ii parameters and ODESSA results is revealed.

X-ray and high resolution selenium-77 solid state NMR spectroscopy as complementary probes to structural studies of organophosphorus diselenides.

77Se high resolution solid state NMR spectroscopy was employed to study structural properties of bis(diisopropoxyphosphorothioyl) diselenide 1 and bis(dineopentoxyphosphorothioyl) diselenide 2. The principal elements Tii of 77Se effective dipolar/chemical shift tensor were calculated from spinning sideband intensities employing the WIN-MAS program. The values of anisotropy and asymmetry parameters reflect the distortion of the selenium environment. It was found that the T33 component mostly contributes to changes in the isotropic chemical shifts. 77Se CP/MAS experiments were used to decide the assignment of space group by counting the number of crystallographically unique selenium centers in the unit cell. Crystals of diselenide 1 are triclinic, space group P1 with a = 8.485(3) A, b = 8.508(1) A, c = 8.511(2) A, alpha = 98.835(15) degrees, beta = 111.653(24) degrees, gamma = 93.524(21) degrees, V = 559.5(3) A3, Dc = 1.544(2) g/cm3 and Z = 1. Refinement using 2222 reflections for 157 variables gives R = 0.037. Crystals of diselenide 2 are triclinic, space group P1 with a = 9.1418(8) A, b = 9.1465(8) A, c = 9.9200(9) A, alpha = 74.751(8) degrees, beta = 74.629(7) degrees, gamma = 82.216(7) degrees, V = 769.7(1) A3, Dc = 1.365(2) g/cm3 and Z = 1. Refinement using 3316 reflections for 297 variables gives R = 0.0272.

Effects of cation interactions on sugar anion conformation in complexes of lactobionate and gluconate with calcium, sodium or potassium.

In the investigated compounds, the tetrahydrated calcium chloride salt of lactobionic acid (Ca2+.-Cl(-).C12H21O12(-).4H2O), potassium lactobionate (K+.-C12H21O12-), sodium lactobionate monohydrate (Na+.-C12H21O12-.H2O) and calcium galactonate hydrate (Ca2+.2C6H11O7(-).5H2O), the cations and hydrogen-bonding systems have a strong influence on the geometries and conformations of the carbohydrate anions.