نتایج جستجو برای: asymmetric water entry
تعداد نتایج: 682689 فیلتر نتایج به سال:
OBJECTIVE To determine whether water exposure causes middle ear contamination in patients with collar button tympanostomy tubes (TTs). METHOD AND DESIGN An in vitro model of a human head that contained an auricle, external auditory canal, tympanic membrane with TT, middle ear, eustachian tube, and mastoid cavity was developed. Two electrodes connected to an external ohmmeter resided in the mi...
Chiral amines are often critical components of pharmaceutical agents. For example, about 15-25% of the singleenantiomer products in development contain this unit according to a recent analysis.1 The development of practical methods for the synthesis of enantiomerically pure amines is therefore of great interest. Traditional resolution methods and enzymatic transaminase technology are frequent c...
Mountain ash (Eucalyptus regnans F.J. Muell.) forest catchments exhibit a strong relationship between stand age and runoff, attributed inter alia to differences in tree water use. However, the tree water use component of the mountain ash forest water balance is poorly quantified. We have used the sap flow technique to obtain estimates of daily water use in large mountain ash trees. First, the s...
We consider two biological phenomena taking place at the air-water interface: the water lapping of felines and the water running of lizards. Although seemingly disparate motions, we show that they are intimately linked by their underlying hydrodynamics and belong to a broader class of processes called Froude mechanisms. We describe how both felines and lizards exploit inertia to defeat gravity,...
Ansa-bridged prodiginines are bioactive pigments produced by bacteria. Certain of these structures are reported to be antagonists of protein-protein interactions involved in apoptosis. We describe a new entry to alkaloids of this type, demonstrated with a concise asymmetric synthesis of (+)-roseophilin (3). Our route constructs the pyrrolophane motif via phosphoryl transfer-terminated macroaldo...
An unprecedented technique for the in situ generation of indolyl ortho-quinodimethanes from 2-methylindole-based methylenemalononitriles by amine-mediated remote C(sp(3) )-H deprotonation was developed. These intermediates were efficiently trapped by diverse enals to provide a rapid entry to 2,9-dihydro-1H-carbazole-3-carboxyaldehyde structures through a formal asymmetric [4+2] eliminative cycl...
A surfactant-type asymmetric organocatalyst (STAO) catalyzed highly efficient Michael addition to nitroalkenes with high stereoselectivities in water without using any organic solvents or additional additives.
Ag(+) mediated aggregation behaviour of two different amphiphilic zinc phthalocyanines (Zn-Pcs) (symmetric and asymmetric) has been investigated in solution, at the air-water interface and in Langmuir-Blodgett (LB) films transferred onto glass substrates. A 4 : 1 ([Ag(+)]/[Pc]) complexation was observed for both symmetric and asymmetric Zn-Pcs at high [Ag(+)] concentrations which led to the for...
Asymmetric N-alkylations of isatins with enals were shown to be feasible via a prolinol-catalyzed iminium activation, and N-alkylated isatins were obtained in good yields and with excellent enantioselectivity. The biologically useful N-alkylated isatins also served as valuable synthetic precursors, and could be readily converted to chiral N-alkylated indole derivatives. The described method pro...
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