The convenient route to cd fragment for the synthesis of vitamin D3 relatives

The efficient degradation of $\text{1}$ to the α-methylene ketone $\text{4}$ is described. Compound $\text{4}$ was then converted to the allylic alcohol $\text{8a}$ - the precursor of vitamin D³ relatives.     

Some analytical semigroups occurring in probability theory

One-parameter semigroups occurring in operator-limit distributions are investigated. The topological-algebraic background of the relevant monoids is discussed and Lie semigroup theory is applied to the Urbanik Decomposability Semigroup.     

Correction procedure for the electron microprobe analysis of porous materials

A correction method is proposed for the quantitative determination of stoichiometric ratios in porous materials by electron microprobe analysis. Analysis of this kind of material is complicated by an imperfect surface that can only be improved to some extent. The correction is based on a linear dependence (different for each element) of the analyses on a sum of weight concentrations of oxides. With this correction it is possible to use analyses affected by the imperfection of the surface with much better confidence compared to common normalisation. An example is presented for a series of ceramic superconductors Bi_2.1(SrCa)_2.9Cu₂O₈₊.     

Carbamoylimidazolium and thiocarbamoylimidazolium salts: novel reagents for the synthesis of ureas, thioureas, carbamates, thiocarbamates and amides

Carbamoylimidazolium salts act as efficient N,N-disubstituted carbamoylating reagents. These salts are readily prepared by the sequential treatment of secondary amines with N,N′-carbonyldiimidazole (CDI) and iodomethane. The carbamoylimidazolium salts are more efficient carbamoyl transfer reagents than the intermediate carbamoylimidazoles, as a result of the ‘imidazolium’ effect. Kinetic studies on the base promoted hydrolysis of both carbamoylimidazoles and carbamoylimidazolium salts reveal over a hundred-fold rate acceleration. The salts react with amines, thiols, phenols/alcohols, and carboxylic acids in high yields, without the need for subsequent chromatographic purification of the products, producing ureas, thiocarbamates, carbamates, and amides, respectively. Analogous thiocarbamoylimidazolium salts were also synthesized from secondary amines and N,N′-thiocarbonyldiimidazole (TCDI), followed by methylation with iodomethane.     

Synthesis and evaluation of the catalytic properties of semicarbazides derived from N-triphenylmethyl-aziridine-2-carbohydrazides

A straightforward synthesis of a series of new catalysts derived from N-triphenylmethyl-aziridine-2-carbohydrazides is described. The new compounds have been tested for the enantioselective addition of diethyl- and phenylethynylzinc to aryl and alkyl aldehydes, which afforded the corresponding chiral alcohols in high chemical yields (up to 92%) and with excellent ee’s of approximately 90%.     

Comparison of the Microbiological Activities of Different Varieties of Hop (Humulus lupulus) Extracts by Thin-Layer Chromatography—Direct Bioautography

JPC – Journal of Planar Chromatography – Modern TLC - Commercially available hop pellets of different origins were extracted by use of ethanol and water, chromatographed on silica...     

Strong Mixing and Operator-Selfdecomposability

For nonstationary, strongly mixing sequences of random variables taking their values in a finite-dimensional Euclidean space, with the partial sums being normalized via matrix multiplication, with certain standard conditions being met (an “infinitesimality” assumption, and a restriction to “full” distributions), the possible limit distributions are precisely the operator-self-decomposable laws.