133 research outputs found
Stereospecific Allylic Functionalization:The Reactions of Allylboronate Complexes with Electrophiles
Allylboronic esters react readily with carbonyls and imines (Ï€-electrophiles), but are unreactive toward a range of other electrophiles. By addition of an aryllithium, the corresponding allylboronate complexes display enhanced nucleophilicity, enabling addition to a range of electrophiles (tropylium, benzodithiolylium, activated pyridines, Eschenmoser's salt, Togni's reagent, Selectfluor, diisopropyl azodicarboxylate (DIAD), MeSX) in high regio- and stereocontrol. This protocol provides access to key new functionalities, including quaternary stereogenic centers bearing moieties such as fluorine and the trifluoromethyl group. The allylboronate complexes were determined to be 7 to 10 orders of magnitude more reactive than the parent boronic ester.</p
Diastereofacial selectivity in intramolecular 1,4-conjugate additions: conclusive evidence for the importance of ground-state conformations and the .sigma.* orbital effect
A New, Iterative Strategy for the Synthesis of Unsymmetrical Polyynes: Application to the Total Synthesis of 15, 16-Dihydrominquartynoic Acid
The Origin of Diastereofacial Control in Allylboration Reactions Using Tartrate Ester Derived Allylboronates: Attractive Interactions between the Lewis Acid Coordinated Aldehyde Carbonyl Group and an Ester Carbonyl Oxygen
Telemetric monitoring of fetal blood pressure and heart rate in the freely moving pregnant sheep: a feasibility study
Remote telemetric monitoring of fetal haemodynamics in pregnant sheep would allow unrestricted animal movement,
minimize suffering and distress, and improve animal welfare, while enhancing the quality of data collected. This may also be
useful in clinical practice following fetal surgery. Using an open fetal surgical technique at approximately two-thirds of
gestation, we implanted the catheter of a D70-PCTP haemodynamic telemetric device (Data Sciences International, Tilburg,
The Netherlands) into the carotid artery of the fetal sheep (n ¼ 4). The attached transmitter was secured to the posterior
aspect of the maternal anterior abdominal wall. Two receivers, with a range of 1 m each, were sited in an 11 m2 sheep
enclosure to maximize animal freedom while allowing continuous monitoring of the ewe. The receivers were connected by
cable to a nearby computer. In the first two procedures, both fetuses died eight and 12 days after surgery, and the catheter tip
was observed to be lying in the bicarotid trunk. In the next two procedures the catheter tip was threaded further upstream
from the insertion point, in an attempt to reach the fetal aorta, and both fetuses survived until the scheduled postmortem
examination at the end of pregnancy. After catheter implantation, fetal blood pressure (BP) and heart rate (HR) were
successfully recorded continuously for seven days and then hourly per day for a further three weeks. The fetal BP and HR
values were in the normal range for healthy sheep fetuses.PublishedN/
Stereospecific Allylic Functionalization: The Reactions of Allylboronate Complexes with Electrophiles
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