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11.
Francisco Palacios Ana M. Ochoa de Retana Rafael López de Munain José M. Ezpeleta 《Tetrahedron》2005,61(5):1087-1094
A simple method for the preparation of phosphorus-containing pyrimidine analogues such as 2,5-dihydro-2-ethoxy-1,5,2-diazaphosphinine 2-oxides 9, 12-15 and adducts 3, 10 is described. Dihydrophosphinines 9, 12-15 are prepared from primary enamine phosphonates and nitriles or from phosphonates and nitriles in the presence of base, while highly stable hydrogen-bonded amine-dihydro-diazaphosphinine adducts 3, 10 are obtained by the addition of amine to dihydrophosphinines 9 or by reaction of alkylphosphonates with nitriles in the presence of LDA. 相似文献
12.
Francisco Palacios Ana M. Ochoa de RetanaSergio Pascual Guillermo Fernández de Trocóniz 《Tetrahedron》2011,67(8):1575-1579
A simple and efficient synthesis of fluoroalkylated α-amino nitrile (4) derivatives by regioselective 1,2-addition of trimethylsilyl cyanide to fluoroalkylated α,β-unsaturated imines (1) is described. Fluoroalkylated β-amino nitriles (7) are also prepared by regioselective 1,2-addition of α-carbanions derived from acetonitrile to fluoroalkylated α,β-unsaturated imines (1). Fluoroalkylated α-(4) and β-amino nitriles (7) are also prepared through an ‘one pot’ procedure by reaction of enaminophosphonate 2 with BuLi, addition of aldehydes and subsequent addition of either trimethylsilyl cyanide or α-carbanion derived from acetonitrile. Basic hydrolysis of α-(4) and β-amino nitriles (7) gives fluoroalkylated α-(5) and β-amino acids (8). 相似文献
13.
Gabriela Ionita Petre Ionita Victor EM. Sahini Constantin Luca 《Journal of inclusion phenomena and macrocyclic chemistry》2001,39(3-4):269-271
The kinetics of oxidation of amino acids (Arg, His, Lys, Phe, Thr and Tyr), a dipeptide (Gly-His), and BSA (bovine serum albumin) by two persistent water soluble free radicals of the hydrazyl type has been studied.The rate decreases in the order Arg>Lys>Tyr>Thr>HisBSAPheGly-His with bothfree radicals. Addition to the reaction mixture of - and -cyclodextrin decreases the oxidation rate, probably due to amino acidencapsulation in the cyclodextrin cavity. -Cyclodextrin protects more efficiently against oxidation than -cyclodextrin. 相似文献
14.
Suárez M Martínez-Alvarez R Martín N Verdecia Y Ochoa E Alba L Seoane C Kayali N 《Rapid communications in mass spectrometry : RCM》2002,16(8):749-754
A variety of 5-alkoxycarbonyl-4-aryl-6-methyl-3,4-dihydro-2(1H)-pyridones and hexahydrofuro[3,4-b]-2(1H)-pyridones have been investigated by electron impact (EI) and electrospray ionisation (ESI) techniques. Sequential product ion fragmentation (MS(n)) was performed to elucidate the degradation pathways for these compounds. Comparisons are made between positive and negative even-electron ions from ESI spectra and the molecular radical cations obtained under EI conditions. The data collected in this paper provide information on the strong impact that different substituents have on the ion fragmentation process. 相似文献
15.
16.
5-Amino-3-oxo-2H, 4H-1,2,6-thiadiazine 1,1-dioxide and the monopotassium salt of 3,5-dioxo-2H, 4H,6H-1,2,6-thiadiazine 1,1-dioxide was obtained by condensation of sulfamide and ethyl cyanacetate and diethyl malonate, respectively. 7-Oxo-1H,4H,6H-imidazo[2,3-c]-1,2,6-thia-diazine 5,5-dioxide was prepared by a multi-step reaction sequence from 5-amino-3-oxo-2H, 4H-1,2,6-thiadiazine 1,1-dioxide. 相似文献
17.
18.
Jorge A. Soria-Alcaraz Gabriela Ochoa Jerry Swan Martin Carpio Hector Puga Edmund K. Burke 《European Journal of Operational Research》2014
Course timetabling is an important and recurring administrative activity in most educational institutions. This article combines a general modeling methodology with effective learning hyper-heuristics to solve this problem. The proposed hyper-heuristics are based on an iterated local search procedure that autonomously combines a set of move operators. Two types of learning for operator selection are contrasted: a static (offline) approach, with a clear distinction between training and execution phases; and a dynamic approach that learns on the fly. The resulting algorithms are tested over the set of real-world instances collected by the first and second International Timetabling competitions. The dynamic scheme statistically outperforms the static counterpart, and produces competitive results when compared to the state-of-the-art, even producing a new best-known solution. Importantly, our study illustrates that algorithms with increased autonomy and generality can outperform human designed problem-specific algorithms. 相似文献
19.
In this paper the optimization of additively decomposed discrete functions is investigated. For these functions genetic algorithms have exhibited a poor performance. First the schema theory of genetic algorithms is reformulated in probability theory terms. A schema defines the structure of a marginal distribution. Then the conceptual algorithm BEDA is introduced. BEDA uses a Boltzmann distribution to generate search points. From BEDA a new algorithm, FDA, is derived. FDA uses a factorization of the distribution. The factorization captures the structure of the given function. The factorization problem is closely connected to the theory of conditional independence graphs. For the test functions considered, the performance of FDA—in number of generations till convergence—is similar to that of a genetic algorithm for the OneMax function. This result is theoretically explained. 相似文献
20.
P. Goya A. Martinez C. Ochoa M. Stud M.L. Jimeno C. Foces-Foces F.H. Cano M. Martinez-Ripoll 《Tetrahedron》1985,41(15):3105-3116
Bisthiadiazinylmethane derivatives obtained from 1,2,6-thiadiazine 1,1-dioxides and formaldehyde, undergo unusual intramolecular cyclizations to thiadiazino [4,3-g] [2,1,3] benzothiadiazine tetraoxides. The structures of the newly synthesized compounds are discussed on the basis of 1H and 13C-NMR data and X-ray analysis. 相似文献