On the mechanism of the reduction of 1-phenyl-3-(4-pyridinylmethylene)-2-oxindole with sodium borohydride in methanol

Sodium borohydride reduction of 1-phenyl-3-(4-pyridinylmethylene)-2-oxindole 1 in methanol gives a high yield of the oxindole 2 , a precursor to linopirdine. The reduction is accelerated by methanol and the major by-products during this reduction are the diastereomeric Michael adducts between 1 and 2 and the overreduced products, 9 and 11 . Surprisingly, indole 9 is not derived from further reduction of 2 but is formed concurrently, whereas the ring opened product 11 is the unexpected reduction product derived from 2 .     

Adjoint and defect error bounding and correction for functional estimates

We present two error estimation approaches for bounding or correcting the error in functional estimates such as lift or drag. Adjoint methods quantify the error in a particular output functional that results from residual errors in approximating the solution to the partial differential equation. Defect methods can be used to bound or reduce the error in the entire solution, with corresponding improvements to functional estimates. Both approaches rely on smooth solution reconstructions and may be used separately or in combination to obtain highly accurate solutions with asymptotically sharp error bounds. The adjoint theory is presented for both smooth and shocked problems; numerical experiments confirm fourth-order error estimates for a pressure integral of shocked quasi-1D Euler flow. By employing defect and adjoint methods together and accounting for errors in approximating the geometry, it is possible to obtain functional estimates that exceed the order of accuracy of the discretization process and the reconstruction approach. Superconvergent drag estimates are obtained for subsonic Euler flow over a lifting airfoil.     

Stereoselective Synthesis of HIV-1 Protease Inhibitor, DMP 323

DMP 323, a potent HIV-1 protease inhibitor, has been synthesized by an efficient stereoselective process, amenable to large scale preparations. The core C(2) symmetric diol was synthesized by a stereoselective pinacol coupling of CBZ protected D-phenylalanine. Judicious selection of protecting groups allowed cyclic urea formation under mild conditions, enhanced the ease of bis-alkylation, and led to intermediates which were easily purified without chromatography. Additionally, a one-pot, high yield process was developed to prepare the alkylating agent, 4-[(triphenylmethoxy)methyl]benzyl chloride from 1,4-benzenedimethanol.     

The synthesis of fluoroether-fluorosilicone hybrid polymers

The replacement of the fluorocarbon segment in the general class of hybrid fluorocarbon-fluorosilicones by fluoroether units was investigated in order to improve low temperature properties without sacrificing high temperature performance. The effects of the co-reactant halogens (bromine and iodine) and metallic fluorides (potassium fluoride and cesium fluoride) on the product yields in the syntheses of the requisite α,ω-dihalo-F-ether intermediates [1] from the corresponding acyl or diacyl fluorides were studied. While a better yield was obtained with bromine than with iodine, the iodoperfluoroethers produced superior yields in the subsequent ethylene addition reactions, as expected. Potassium fluoride was preferable to cesium fluoride in the synthesis of the iodo-F-ethers, since cesium fluoride effects decomposition of the ethers.     

On-line liquid chromatography-electrospray ionization mass spectrometry for determination of the brevetoxin profile in natural “red tide” algae blooms

Reversed-phase liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) was employed to analyze brevetoxin compounds associated with naturally occurring red tide blooms collected from Sarasota Bay, FL, USA. The LC-ESI-MS method utilizes a C₁₈ microbore column with a mobile phase consisting of methanol-water (85:15, v/v), a flow-rate of 8 μl/min and a post-column split ratio of 3:1 (UV-absorbance detector-mass spectrometer). Three known brevetoxins Btx-2, Btx-1 and Btx-3 were detected at 60 μg/l, 10 μg/l and 5.7 μg/l levels, respectively, in the natrual red tide bloom samples. This distribution differed quantitatively from that found in red tide culture extract samples. Btx-9 was not detected either in natural red tide bloom extracts or in red tide culture extracts, possibly due to the instability of this compound. An unknown component with a molecular mass of 941 found in the natural bloom extract was postulated to have the structure of a reduced form (hydrogenation of two double bonds in the alkyl side chain) of Btx-5.     

An ‘Emergent Model’ for Rate of Change

Does speed provide a ‘model for’ rate of change in other contexts? Does JavaMathWorlds (JMW), animated simulation software, assist in the development of the ‘model for’ rate of change? This project investigates the transference of understandings of rate gained in a motion context to a non-motion context. Students were 27 14–15 year old students at an Australian secondary school. The instructional sequence, utilising JMW, provided rich learning experiences of rate of change in the context of a moving elevator. This context connects to students’ prior knowledge. The data taken from pre- and post-tests and student interviews revealed a wide variation in students’ understanding of rate of change. The variation was mapped on a hypothetical learning trajectory and interpreted in the terms of the ‘emergent models’ theory (Gravemeijer, Math Think Learn 1(2):155–177, 1999) and illustrated by specific examples from the data. The results demonstrate that most students were able to use the ‘model of’ rate of change developed in a vertical motion context as a ‘model for’ rate of change in a horizontal motion context. A smaller majority of students were able to use their, often incomplete, ‘model of’ rate of change as a ‘model for’ reasoning about rate of change in a non-motion context.     

Mono-nitration of aromatic compounds via their nitric acid salts

Aromatic compounds bearing a basic nitrogen atom can be converted to the corresponding nitric acid salts. Mono-nitration of the compounds can be carried out by adding a dichloromethane solution of the salts to sulfuric acid, or by adding acetyl chloride (or trifluoroacetic anhydride) to a dichloromethane solution of the salts. This protocol provides, among other benefits, the most convenient and reliable way for the prevention of over-/under-nitration and is especially suitable for scale-up.