Wiesław R. Majzner

Enzyme-promoted kinetic resolution of racemic, P-chiral phosphonyl and phosphorylacetates

Abstract A series of racemic methyl phosphonyl- and phosphorylacetates were hydrolyzed in the presence of porcine liver esterase (PLE) under kinetic resolution conditions to give the corresponding P-chiral phosphonyl- and phosphorylacetic acids and recovered esters in moderate to high enantiomeric purity (up to 95% ee). The Jones PLE active site model was applied to explain the enantioselectivity of this reaction.

Transformation of Carotol into the Hydroindane‐Derived Musk Odorant

Ozonolysis of carotol (1) gives dihydroxy ketone 2 (63% yield), the absolute configuration of which was established by X-ray crystallography. An acidic dehydration of 2 delivers a mixture of isomeric ketones 3 and 4 (3:1) that, catalysed by Pd/C in cyclohexene, yields a 1:1 thermodynamic mixture of 3 and 6. Ketone 6 exhibits an intensive musk odour. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Crystal and molecular structure of the levorotatory (1R,2S)-ephedrinium (S)-t-butylsulfinylacetate: a definitive proof of the absolute configuration of enantiomeric t-butyl methyl sulfoxides

Abstract The levorotatory enantiomer of t-butylsulfinylacetic acid 3 was obtained in the reaction of the α-carbanion of (+)-t-butyl methyl sulfoxide 1 with carbon dioxide. The same enantiopure form of the acid 3 was isolated from its diastereomerically pure levorotatory salt 5 with (−)-(1R,2S)-ephedrine. The structure of this salt was determined by X-ray analysis and the absolute configuration (S) at sulfur was ascribed to the t-butylsulfinylacetate anion. Consequently, the absolute configuration (S) was assigned to the acid (−)-3 and its precursor (+)-t-butyl methyl sulfoxide 1.

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.

Kinetic Resolution of Racemic Cyclic Sulfoxides Using Hydrolytic Enzymes

Selected racemic trans-2-alkoxycarbonyl-3,6-dihydro-2H-thiopyran S-oxides 2a–h have been subjected to enzyme-assisted hydrolysis under conditions of kinetic resolution to give the corresponding acids and recovered esters with moderate to high enantiomeric purities (up to 95%). The enantioselectivity of the reaction was found to be strongly dependent on the structures of the substrates used.

Structural Investigation of Biologically Active Phenolic Compounds Isolated from European Tree Species

X-ray structures of two compounds isolated from wood knots of coniferous trees, namely dihydrokaempferol (3,5,8,13-tetrahydroxyflavanon) and lariciresinol (3,14-dimetoxy-7,10-epoxylignan-4,15,19-triol), are presented here. Diffraction data for the dihydrokaempferol crystals were collected on a CAD4 diffractometer and on a synchrotron for the lariciresinol crystal. The investigated compounds inhibit lipid peroxidation and lariciresinol is additionally a good scavenger of superoxide radicals. The structural data presented in this work provide a useful basis for designing more active compounds with potential use as antioxidants.

An expedient, stereoselective synthesis of highly functionalized cyclic compounds

New thiophosphates containing functionalized cyclic ketone derivatives as ligands have been stereoselectively prepared from readily available starting materials. Full axial stereoselectivity of the NaBH4 reduction of the carbonyl group in thiophosphates providing the corresponding thiols or sulfides has been demonstrated. The sulfides have been transformed into new functionalized cyclic Baylis–Hillman type adducts of defined configuration. The prospects for the useful synthetic application of these adducts appear to be very promising.

SOLID STATE CONFORMATION OF THE ANOMERIC EFFECT IN 2-PHOSPHORYL-, 2-THIOPHOSPHORYL- AND 2-SELENOPHOSPHORYL-SUBSTITUTED 1,3-DITHIOLANES

Abstract The crystal structure of the title compounds 1–3 have been determined by X-ray diffraction studies. The 1,3-dithiolane ring in all three compounds adopts a twist conformation with the Ph2P=X group being pseudoaxial. The structural data suggest that the ns → σC-P* negative hyperconjugation is responsible for the anomeric effect in 1,3-dithiolanes.

X-ray structure of a novel histidine-copper(II) complex

A new crystal structure of the dichloro(L-histidine)copper(II) half-hydrate is reported. In this complex, histidine acts as a bidentate ligand to the copper(II) cation. The coordination sphere of the copper cation is created by the carboxyl oxygen and the amine nitrogen from main chain group of histidine. Two additional chloride anions complete the square coordination of the central Cu+2 cation. In the crystal, the copper cations are additionally surrounded by two chloride anions from neighboring complex molecules, which are located in the distant axial position and fill up the stretched octahedral coordination sphere Cu+2. In the presented complex, the histidine molecule exists as a zwitter ion with an unprotonated negatively charged carboxyl group and with double protonated positively charged imidazole ring. Crystallographic study was supported by IR measurements confirming the presence of water in the crystal structure.

Synthesis and Structural Studies ofSP andRP Diastereomers of Deoxyxylothymidyl-3′-O-acetylthymidyl (3′,5′)-O-(2-Cyanoethyl)phosphorothioate in Solution and in the Solid State

The synthesis and full assignment of the molecular structure of the diastereomers of deoxyxylothymidyl-3′-O-acetylthymidyl (3′,5′)-O-(2-cyanoethyl)phosphorothioate (1) in the liquid phase based on 1 H, 13C, 1D and 2D homo- and heteronuclear PFG (Pulse Field Gradient) NMR spectroscopic experiments are reported. The pseudorotation parameters of deoxyribose and deoxyxylose were analyzed by means of the PSEUROT program. The absolute configuration RP and SP of the phosphorus centers was deduced from 1H ROESY experiment. The 31P CP/MAS technique was used to establish the ratio between the amorphous and crystalline phases, and to test the progress of crystallization. The differences in the 31P δii principal elements of the chemical shift tensor, in particular the δ33 parameter, for crystalline and amorphous phases were calculated. Finally, the X-ray data for the SP diastereomer are reported. The influence of weak C−H···S hydrogen bonding on the molecular packing of both Rp-1 and SP-1, and the significance of this type of intermolecular interaction for phosphorothioate systems is discussed.