The application of diethylaminosulfur trifluoride in the synthesis of fluorinated sterols and bile acids

Methyl 3,3-(ethylenedioxy)-6β-fluoro-5β-cholan-24-oate has been prepared starting from hyodeoxycholic acid and 3,3-(ethylenedioxy)-7( and β)-fluorocholestan-22-al starting from stigmasterol, using diethylaminosulfur trifluoride as the fluorinating agent. These molecules will be used to synthesize analogs of the aminosterol antibiotic squalamine.     

Reactivity of pseudobases from pyridinium salts competition between hydrogen transfer and ring-opening reactions

The reactions of 3-cyano-1-methylpyridinium iodide (1a) and l-benzyl-3-cyanopyridinium chloride (1b) in aqueous NaOH have been studied over a range of concentrations from N 0.5 to N 2.5 with respect to the hydroxide ion, and with the concentrations of the reactants at different ratios. It has been found that the intermediate, not isolable pseudobases can undergo, depending on the experimental conditions, two competitive reaction channels, namely, a redox process leading to the dihydropyridines 3–5 and pyridones 2,6, and a ring-opening reaction leading to the pentadienenitrile 7, 2-imino-3-pyridinecarbaldehyde 8, and 2-(aryl)alkylamino-3-pyridinecarbaldehyde 9.     

Oxidation of 3-hydroxykynurenine. A reexamination

The oxidation mixture of 3-hydroxykynurenine ( 1 ), treated with aqueous acetic anhydride and, subsequently, with acidic methanol, yields the 1-hydroxy-3-carbomethoxy-5-methoxy-11-(β-aspartoyl-N-acetyl-methyl ester)pyrido[3,2-a]phenoxazine ( 5 ), the 1-hydroxy-11-(β-aspartoyl-N-acetyl-methyl ester)-5.H-pyrido[3,2-a]-phenoxazin-5-one ( 6 ), the 1-methoxy-11-(β-aspartoyl-N-acetyl-methyl ester)-5H-pyrido[3,2-a]phenoxazin-5-one ( 6a ), the l,5-dimethoxy-11-(β-aspartoyl-N-acetyl-methyl ester)pyrido[3,2-a]phenoxazine ( 7 ) and the 1-methyl-1(1′-[11-(β-aspartoyl-methyl esterimino)]ethenyl)ketal-1H,5H-pyrido[3,2-a]phenoxazin-5-one ( 8 ). A probable scheme, for the compound formation, is reported.     

Photochemistry of ommochromes and related compounds. Part II

The visible light irradiated solutions of the 1-methyl-1-(1′-[11-(β-aspartoyl-methyl ester-imino)]ethenyl]-ketal-1H,5H-pyrido[3,2-a]phenoxazin-5-one ( 1 ) and the 1,5-dimethoxy-11-(β-aspartoyl-N-acetyl-methyl ester)-pyrido[3,2-a]phenoxazine ( 2 ) [1], in methanol and acidic methanol, are examined. Both methanolic solutions undergo light induced transformation according to an opening of the phenoxazinone and phenoxazine systems, not reversible in darkness. On the contrary, 1 and 2 in methanol-acid solutions, under visible light irradiation, yield a solvent photoaddition, reversible in darkness. Some phototransformation products are examined and a plausible mechanism, for the reactions explanation, is suggested.     

A dynamic production planning and scheduling algorithm for two products processed on one line

This paper presents a dynamic production planning and scheduling algorithm for two products processed on one line over a fixed time horizon. Production rates are assumed fixed, and restrictions are placed or inventory levels and production run lengths. The resulting problem is a nonlinear binary program, which is solved using an implicit enumeration strategy. The algorithm focuses on the run changeover period while developing tighter bounds on the length of the upcoming run to improve computational efficiency. About 99% pf 297 randomly generated problems with varying demand patterns are solved in less than 15 seconds of CPU time on a CDC Cyber 172 Computer. A mixed integer programming formulation of the generalized multi-product case under no-backlogging of demand is also given.     

Experimental evidence of transversal oscillations in a sea-connected rectangular basin

The response of a rectangular basin along a straight, perfectly reflecting coastline, subject to monochromatic waves coming either normally or obliquely from the sea, was investigated theoretically and experimentally.While the theoretical analysis allowed recognition of various kinds of longitudinal and transversal oscillations and their properties as a function of the geometrical dimensions of the basin, wave length and wave incidence, the experimental investigation confirmed, both for normal and oblique incidence, the validity of the theoretical results and particularly the importance of the transversal oscillations.     

A column generation algorithm for the vehicle routing problem with soft time windows

The Vehicle Routing Problem with Time Windows consists of computing a minimum cost set of routes for a fleet of vehicles of limited capacity visiting a given set of customers with known demand, with the additional constraint that each customer must be visited in a specified time window. We consider the case in which time window constraints are relaxed into “soft” constraints, that is penalty terms are added to the solution cost whenever a vehicle serves a customer outside of his time window. We present a branch-and-price algorithm which is the first exact optimization algorithm for this problem.     

Shear thickening and shear-induced agglomeration of chemical mechanical polishing slurries using electrolytes

Chemical mechanical polishing is a fundamental technology used in the semiconductor manufacturing industry to polish and planarize a wide range of materials for the fabrication of microelectronic devices. During the high-shear (～1,000,000 s^?1) polishing process, it is hypothesized that individual slurry particles are driven together to form large agglomerates (≥0.5 µm). These agglomerates are believed to trigger a shear-induced thickening effect and cause defects during polishing. We examined how the addition of various monovalent salts (CsCl, KCl, LiCl, and NaCl) and electrostatic stabilizing bases (KOH, NaOH, or CsOH) influenced the slurry’s thickening behavior. Overall, as the added salt concentration was increased from 0.02 to 0.15 M, the shear rate at which the slurry thickened (i.e., the critical shear rate) decreased. Slurries with added CsCl, NaCl, and LiCl thickened at comparable shear rates (～20,000–70,000 s^?1) and, in general, followed ion hydration theory (poorly hydrated ions caused the slurry to thicken at lower shear rates). However, slurries with added KCl portrayed thickening behavior at higher critical shear rates (～35,000–100,000 s^?1) than other chloride salts. Also, slurries stabilized with CsOH thickened at higher shear rates (～90,000–140,000 s^?1), regardless of the added salt cation or concentration, than the slurries with KOH or NaOH. The NaOH-stabilized slurries displayed thickening at the lowest shear rates (～20,000 s^?1). The thickening dependence on slurry base cation indicates the existence of additional close-range structure forces that are not predicted by the Derjaguin–Landau–Verwey–Overbeek colloidal stability theory.