Synthesis of "sugar-rods" with phytohemagglutinin cross-linking properties by using the palladium-catalyzed Sonogashira reaction

A palladium-catalyzed Sonogashira reaction has been applied for the syntheses of divalent "sugar-rods" which exhibited excellent lectin cross-linking properties. The procedure, which involves a tetrakis(triphenylphosphine)palladium-catalyzed cross-coupling reaction between an alkyne and a halogen-bearing sp2-carbon in DMF at 60 degrees C, is very efficient and the dimeric or heterobifunctional "sugar-rods" (8-13, 15-17) were isolated in 65-100% yields. Dimers 8a and 15a were both shown to form insoluble cross-linked lattices when mixed with the tetrameric plant lectin from Canavalia ensiformis (Concavalin A, Con A). Moreover, the relative inhibitory properties of the synthetic dimannosides were determined by means of the hemagglutination of rabbit erythrocytes, whereby dimer 15a was shown to be 20-fold more potent than monomeric methyl alpha-D-mannopyranoside.     

Determination of non-homogeneous high-concentration depth distributions using elastic backscattering data

A computer program has been developed by which the depth concentration distribution of a two-element bulk sample can be determined from elastic backscattering data. The presented calculative procedure can be applied to non-homogeneous high concentrations, where the composition variation as a function of depth has to be considered to obtain correct distributions. Two samples with different compositions, nitrogen in titanium and gold in silicon, were analysed with 2MeVH⁺ and He⁺ ions, respectively, to illustrate the versatility of the calculative program.     

Structure of the bromination product of 2-ethyl-1,4-benzothiazin-3(4H)-one

2-Ethyl-1,4-benzothiazin-3(4H)-one and bromine react smoothly to give Z-2-(1-bromoethylidine)-2(H)-1,4-benzothiazin-3(4H)-one, which results from a complex bromination-oxidation sequence. The structure of this product was determined by an X-ray study.     

Benzo[b]thiophene derivatives. XX. The sulfur isostere of 5,6-Dihydroxytryptamine

3β-Aminoethyl-5,6-dihydroxybenzo[b]thiophene, the sulfur bioisostere of 5,6-dihydroxytryptamine, a selective neurotoxin, has been synthesized and shown to have significant effect on biogenic amine levels both centrally and peripherally. A derivative, 3β-aminoethyl-5,6-isopropylidenedioxybenzo[b]thiophene, showed significant but opposite activity. The syntheses and preliminary pharmacology are reported.     

A dynamic model of the purchase of gasoline

Government regulators and gasoline retailers can manipulate certain inputs to the gasoline purchase process: station hours, inventory allocations, odd-even plans, etc. If one could model the purchasing dynamics, these inputs could be timed and otherwise planned to minimize inconvenience to the consumer. In this paper, we recognize that the refilling of gasoline tanks is a renewal process. The simplest model, is then, a first-order partial differential equation of continuity plus an integral boundary condition. Many properties of this model are derived here including an important mathematical link with the theory of queues (yielding estimates of daily average line lengths, for instance). The paper concludes with several simulations which demonstrate the significance of the dynamic effects (over-shoot, resonance) and the important effect of the retailers management rules on the length of gas lines.     

Analytical methods in oceanography I. Inorganic methods

Man's speculations on the nature of sea water have been recorded since the time of the ancient Greeks, but it was not until 1670, when Robert Boyle published a work entitled Observations and Experiments on the Saltiness of the Sea, that any systematic chemical measurements were carried out. Since these early days analytical chemistry has developed into the principal tool used to investigate sea water and marine processes.