Lower level duality and the global solution of generalized semi-infinite programs

The reformulation of generalized semi-infinite programs (GSIP) to simpler problems is considered. These reformulations are achieved under the assumption that a duality property holds for the lower level program (LLP). Lagrangian duality is used in the general case to establish the relationship between the GSIP and a related semi-infinite program (SIP). Practical aspects of this reformulation, including how to bound the duality multipliers, are also considered. This SIP reformulation result is then combined with recent advances for the global, feasible solution of SIP to develop a global, feasible point method for the solution of GSIP. Reformulations to finite nonlinear programs, and the practical aspects of solving these reformulations globally, are also discussed. When the LLP is a linear program or second-order cone program, specific duality results can be used that lead to stronger results. Numerical examples demonstrate that the global solution of GSIP is computationally practical via the solution of these duality-based reformulations.     

Electrophoretic and chromatographic evaluation of transgenic barley expressing a bacterial dihydrodipicolinate synthase

Nutritional quality of human and animal foodstuffs is determined by the content of essential amino acids. Barley is the fourth most important cereal of the world and the second most important cereal grown in the Czech Republic. Cereal grains such as barley contain insufficient levels of some essential amino acids, especially lysine. Dihydrodipicolinate synthase is the key enzyme involved in the regulatory step for lysine biosynthesis. Two constructs pBract214::sTPdapA and pBract214::mdapA containing the dapA gene from Escherichia coli coding for the bacterial dihydrodipicolinate synthase were used for transformation of barley. An Agrobacterium-mediated technique was used for transformation of immature embryos of spring barley cv. Golden Promise. Transgenic barley plants of the T0 and T1 generations were evaluated by PCR, real-time PCR, gel electrophoresis, and Western blot. Amino acid content was analyzed by HPLC after HCl hydrolysis. The lysine content in leaves of the T1 generation plant no. 5/5 was 50% higher than in wild-type plants; the lysine content in seeds of T2 generation plant no. 5/16 was 30% higher than in wild-type seeds of spring barley cv. Golden Promise.     

Estimation of slow diffusion rates in confined systems: CCl4 in zeolite NaA

Often the rate of passage of gaseous molecules through model zeolites is too small to be computed directly. An estimate for the rate of passage of CCl₄ through the 8-ring window in a model of zeolite A has been obtained by combining a direct evaluation of the free energy profile and an adaptation of the rare events method. First the free energy profile is found from a direct evaluation of the canonical partition function at high dilution and the transition state theory rate constant obtained. The dynamic correction factor is then estimated from molecular dynamics runs and used to compute the actual rate k_eff. The method is used to estimate the rate of passage through the 8-ring window in a rigid model of zeolite A, and the results are compared with those obtained from rigid models with expanded windows and from the flexible model. Even a small expansion in the 8-ring window diameter increases the rate significantly, but the changes associated with a flexible cage are small.     

44-Methylgambierone,a new gambierone analogue isolated from Gambierdiscus australes

A new analogue of gambierone, 44-methylgambierone, was isolated from the benthic dinoflagellate Gambierdiscus australes collected from Raoul Island (Rangitahua/Kermadec Islands). This molecule has been previously reported as maitotoxin-3. The structure of 44-methylgambierone was elucidated using 1D- and 2D-nuclear magnetic resonance spectroscopy and mass spectrometry techniques. The nine-ring polyether backbone (A–I) and functional groups (carbonyl, terminal diol, 1,3-diene and monosulphate) are the same for both compounds with the addition of an olefinic methyl group being the only modification in 44-methylgambierone.     

A biomimetic synthesis of chrysanthemol

The factors governing the competitiun between 1,2-and 1,3-eliminations have been studied and the results obtained have been applied to a biomimetic synthesis of chrysanthemol.     

Thermal and photo-decomposition of 1,4-disubstituted alkylaminoanthraquinone dyes in polymers and solution: A chromatographic and spectroscopic study

The photo-decomposition products of five 1,4-disubstituted anthraquinones produced in polyester and nylon 6,6 fabrics and related solvents have been compared with those produced in the thermal oxidation of the dyes on silica gel plates at 150°C. Using TLC, ultraviolet-visible absorption spectroscopy and mass spectrometry, the decomposition products were found to be generally very similar. The number and complexity of the products formed were found to be very dependent on the duration of exposure. These results indicated that the thermal and light stability of the dye is considerably less than that predicted by normal visual colour assessments. From an analysis of the products of decomposition early theories on N-dealkylation are confirmed and their arguments on N-formylation are partially resolved.     

Development of an alanine-derived chiral stabilized azomethine ylid based on the 5-(2′-naphthyl)morpholin-2-one template

A rows to enantiomerically pure -methyl functionalized proline derivatives is presented, using a 1,3-dipolar cycloaddition strategy based upon a homochiral 5-(2-naphthyl)morpholin-2-one template. A mild means of generating stabilized azomethine ylids using sonication and Lewis acid catalysis is developed, avoiding the use of excessive temperatures.Dyson Perrins Laboratory, University of Oxford, South Parks Road, Oxford, OX1 3QY, UK. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1393–1401, October, 1995. Original article submitted September 18, 1995.     

Effect of methoxyl group position on the regioselectivity of ammonia substitution reactions involving 3,3'-dichloro-2,2'-binaphthoquinones

A series of methoxyl-substituted 3,3'-dichloro-2,2'-binaphthoquinones 2 were prepared and evaluated for regioselectivity in ammonia substitution reactions. Biquinone 2b underwent regiospecific amination at the unsubstituted chloronaphthoquinone unit whereas the isomeric biquinone, 2c, produced moderate regioselectivity (85:15). Biquinone 2d, however, showed no level of regioselectivity demonstrating that the position of the methoxyl group influences the regiochemistry. The intramolecular hydrogen bond in biquinone 5 altered the regioselectivity. Semiempirical calculations revealed comparatively larger LUMO coefficients at the chlorinated carbons that underwent preferential substitution.     

Synthesis of a novel class of chiral polyaromatic amide dendrimers bearing an amino acid derived C3-symmetric core

Chiral polyaromatic amide dendrimers incorporating a C₃-core have been prepared as potential catalysts for asymmetric reactions.     

Synthesis of enantiomerically pure α-amino acids via chemo- and diastereoselective alkylation of (5S)-5-phenyl-5,6-dihydro-2H-1,4-oxazin-2-one

(5S)-5-Phenyl-5,6-dihydro-2H-1,4-oxazin-2-one 2 undergoes lewis acidmediated chemo- and diastereoselective nucleophilic addition of Grignard reagents to furnish adducts 3 which can be dismantled to allow ready access to enantiomerically pure (S)-α-amino acids 4.