The adsorption and reaction of 2-butanol on clean and oxygen-covered Pd(100)

The surface chemistry of 2-butanol is explored on clean Pd(100), c(2 × 2)-O/Pd(100) and p(2 × 2)-O/Pd(100) surfaces by means of temperature-programmed desorption, reflection–absorption infrared and X-ray photoelectron spectroscopies. 2-Butanol adsorbs molecularly on clean and oxygen-covered Pd(100) below ～ 190 K, but then appears to react to form 2-butoxide species at ～ 200 K. Both 2-butanone and 2-butanol desorb from the clean surface at ～ 226 K, by β-hydride elimination from the 2-butoxide species and rehydrogenation of the 2-butoxide, respectively. In contrast, almost exclusively 2-butanone is formed on oxygen-covered surfaces. Butanone desorbs at ～ 195 K and ～ 260 K from c(2 × 2)-O/Pd(100) with the 195 K peak being the most intense. However, on p(2 × 2)-O/Pd(100), 2-butanone desorbs at ～ 195 K and ～ 295 K, and the latter peak is the most intense. The ～ 195 K, 2-butanone state is proposed to occur due to abstraction by adsorbed atomic oxygen and the change in relative intensity of these features is ascribed to the lower ability of surface hydroxyl groups to facilitate β-hydride elimination on oxygen-covered surfaces. Further heating results in the formation of hydrogen and carbon monoxide and leaves a small amount of carbon deposited on the surface.     

Synthesis, determination of absolute configuration, and biological evaluation of spiro-fused thiadiazoline inhibitors of kinesin spindle protein (KSP)

A facile and highly convergent synthesis of biologically active spiro-fused thiadiazoline KSP inhibitors is reported. The highlights of the synthesis include the Michael reaction and cyclization of thiosemicarbazone to 1,3,4-thiadiazoline. This chemistry lends itself to the preparation of (+)-2, a potent and orally bioavailable anti-cancer agent, and to the development of a structure-activity relationship program.     

Psilocin analogs II. Synthesis of 3-[2-(dialkylamino)ethyl]-, 3-[2-(N-methyl-N-alkylamino)ethyl]-, and 3-[2-(cycloalkylamino)ethyl]indol-4-ols

Structural alteration of the N^b-substituents of psilocin (3-[2-dimethylamino)ethyl]indol-4-ol) ( 12a ) has led to a number of compounds containing known pharmacophoric groups. Further, it is hoped that the subtle changes in the nature of these substituents may lead to a clearer understanding of the structure-activity relationships of the 4-hydroxytryptamine hallucinogens.     

Physical properties and structure of fine core–shell particles used as packing materials for chromatography: Relationships between particle characteristics and column performance

The recent development of new brands of packing materials made of fine porous-shell particles, e.g., Halo and Kinetex, has brought great improvements in potential column efficiency, demanding considerable progress in the design of chromatographic instruments. Columns packed with Halo and Kinetex particles provide minimum values of their reduced plate heights of nearly 1.5 and 1.2, respectively. These packing materials have physical properties that set them apart from conventional porous particles. The kinetic performance of 4.6 mm I.D. columns packed with these two new materials is analyzed based on the results of a series of nine independent and complementary experiments: low-temperature nitrogen adsorption (LTNA), scanning electron microscopy (SEM), inverse size-exclusion chromatography (ISEC), Coulter counter particle size distributions, pycnometry, height equivalent to a theoretical plate (HETP), peak parking method (PP), total pore blocking method (TPB), and local electrochemical detection across the column exit section (LED). The results of this work establish links between the physical properties of these superficially porous particles and the excellent kinetic performance of columns packed with them. It clarifies the fundamental origin of the difference in the chromatographic performances of the Halo and the Kinetex columns.     

Oligosaccharide-peptide ligation of glycosyl thiolates with dehydropeptides: synthesis of S-linked mucin-related glycopeptide conjugates

A chemoselective strategy for oligosaccharide-peptide ligation is described in which alpha-thio analogues of mucin-related glycoconjugates can be readily accessed through site-selective conjugate addition of complex oligosaccharide thiolates to dehydroalanine-containing peptides. The efficiency of the ligation is highlighted by the rapid convergent assembly of thio-isosteres of the four tumor-associated carbohydrate antigens, T(N), T, ST(N), and 2,6-ST, as a pair of diastereoisomers at the newly formed cysteine stereocenter. The process proceeds in high yield and with complete retention of the alpha-anomeric configuration.     

Psilocin analogs. III. Synthesis of 5-methoxy- and 5-hydroxy-1,2,3,4-tetrahydro-9H-pyrido[3,4-b]indoles

A number of tetrahydro-β-carbolines were prepared with oxygen substituents at C-5. This class of compounds represents a hybrid between two naturally occurring groups of hallucinogenic molecules, the 4-hydroxytryptamines and the 6- and 7-oxygenated β-carbolines.