نتایج جستجو برای: ring transformation
تعداد نتایج: 341445 فیلتر نتایج به سال:
The structurally intriguing terpenes pallambins C and D have been assembled in only 11 steps from a cheap commodity chemical: furfuryl alcohol. This synthesis, which features a redox-economic approach free of protecting-group manipulations, assembles all four-ring systems via a sequential cyclization strategy. Of these four-ring constructing operations, two are classical (Robinson annulation an...
We show that the Kähler-Ricci flow on an algebraic manifold of positive Kodaira dimension and semi-ample canonical line bundle converges to a unique canonical metric on its canonical model. It is also shown that there exists a canonical measure of analytic Zariski decomposition on an algebraic manifold of positive Kodaira dimension. Such a canonical measure is unique and invariant under biratio...
Selective synthesis of unsymmetric dibenzo[a,e]pentalenes by a rhodium-catalysed stitching reaction.
A rhodium-catalysed stitching reaction between 2-(silylethynyl)arylboronates and 2-(silylethynyl)aryl bromides has been developed for the synthesis of unsymmetric dibenzo[a,e]pentalenes. The introduction of appropriately sized silyl groups on the starting substrates led to a high crossover selectivity without using an excess amount of either substrate. The present stitching reaction could produ...
Organocatalytic activation of readily available substrates has led to the rapid development of many enantioselective reactions in the last decade. In N-heterocyclic carbene (NHC) catalysis, reactions of enals with enones or enone derivatives have been extensively investigated and are reported to undergo a diverse set of transformations based on the catalytically generated enolate and homoenolat...
Pairs (A,B) of mutually annihilating operators AB = BA = 0 on a finite dimensional vector space over an algebraically closed field were classified by Gelfand and Ponomarev [Russian Math. Surveys 23 (1968) 1–58] by method of linear relations. The classification of (A,B) over any field was derived by Nazarova, Roiter, Sergeichuk, and Bondarenko [J. Soviet Math. 3 (1975) 636–654] from the classifi...
The title compound, C(19)H(28)O(3), the fungal-transformed metabolite of the steroid methyl-oestrenol contains four fused rings A, B, C and D. Ring A adopts a half-chair and the trans-fused rings B and C adopt chair confirmations; the five-membered D ring is folded like an envelope. In the crystal, adjacent mol-ecules are linked by O-H⋯O(carbon-yl) and O-H⋯O(hy-droxy) hydrogen bonds into a laye...
abstract in this thesis at first we comput the determinant of hankel matrix with enteries a_k (x)=?_(m=0)^k??((2k+2-m)¦(k-m)) x^m ? by using a new operator, ? and by writing and solving differential equation of order two at points x=2 and x=-2 . also we show that this determinant under k-binomial transformation is invariant.
1. Introduction Ringwooodite, produced by shock metamorphism, is common in and adjacent to melt veins in highly shocked chondrites. Although ringwoodite can crystallize from the silicate melt in the shock-vein or pockets, most of the easily observed ringwoodite in shock veins is formed by the transformation of olivine in host-rock fragments entrained in the melt or olivine along shock-vein marg...
We examined the pathway by which the fungicide biphenyl is metabolized in the imperfect fungus Paecilomyces lilacinus. The initial oxidation yielded the three monohydroxylated biphenyls. Further hydroxylation occurred on the first and the second aromatic ring systems, resulting in the formation of five di- and trihydroxylated metabolites. The fungus could cleave the aromatic structures, resulti...
Facial expressions are facial movements reflecting the internal emotional states of a character or in response to social communications. Realistic facial animation should consider at least two factors: believable facial expression visual effect and valid facial movements. However, most research tends to separate these two issues. In this paper, we present a framework for generating facial anima...
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