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Biomedical subjects

A T Merritt

Publications and source records attributed to A T Merritt.

6 recordsLinked to original sources
PubMed2001

Palladium-catalyzed tandem reactions to form 1-vinyl-1h-isochromene derivatives.

The palladium-catalyzed reaction of pinacolone with tert-butyldimethyl(3-(2-bromophenyl)allyloxy)silane results in direct formation of 1-vinyl-3-tert-butyl-1H-isochromene. This is the result of a ketone arylation followed by an intramolecular cyclization of the enolate with the allylic system. The use of a lithium diamide base appears to be essential for success. The tert-butyldimethylsilyl protecting group is also an essential choice as it furnishes the appropriate reactivity to promote allylic substitution after the aryl coupling process. The use of more effective leaving groups, such as acetate, results in reaction of the allylic group, and no aryl coupling is observed. Through the appropriate selection of phosphine ligand and solvent, either the cyclized isochromene product or the noncyclized intermediate may be formed selectively. A short combinatorial study of the scope and limitations of the reaction, involving 24 ketones, is described.

Journal Article↗
PubMed1998

Solution phase combinatorial chemistry.

Combinatorial chemistry and parallel array synthesis techniques are now used extensively in the drug discovery process. Although published literature has been dominated by solid phase chemistry approaches, the use of solution phase techniques has also been widely explored. This review considers the advantages and disadvantages of choosing solution phase approaches in the various stages of drug discovery and optimisation, and assesses the practical issues related to these approaches. The uses of standard solution chemistry, the related liquid phase approach, and of supported materials to enhance solution phase chemistry are all illustrated by a comprehensive review of the published literature over the past three years.

Chemistry, Pharmaceutical↗
PubMed1990

Correlation of patent ductus arteriosus shunting with plasma atrial natriuretic factor concentration in preterm infants with respiratory distress syndrome.

The concentration of plasma atrial natriuretic factor (ANF) and the mechanism for its secretion were investigated in 17 preterm infants with respiratory distress. Their mean gestational age was 29 wk and wt 1250 g. The infants were followed during the first week of life by sequential Doppler ultrasound studies. Ductal openness versus closure and amount of ductal flow were correlated with plasma ANF concentrations. In a subset of 10 infants, sequential Doppler color flow mapping was used to quantify the ductal flow. During the first 72 h, plasma ANF was high, 361 pg/mL; it decreased to 96 pg/mL by the end of the 1st wk. The ANF level was significantly higher when the ductus was open than closed (393 versus 123 pg/mL, p less than 0.05). In patients with open ductus and bidirectional foramen ovale shunting (n = 3) ANF was 567 pg/mL and in those with left-to-right shunt 355 pg/mL (n 15, NS). The left atrial size, i.e. the left atrial to aortic root ratio, correlated with the amount of ductal shunting (r = 0.63, p less than 0.01) and with ANF concentration (r = 0.46, p less than 0.02). The correlation of ANF values and the magnitude of left-to-right ductal shunting assessed by color flow mapping was highly significant (r = 0.66, p less than 0.001). In these patients, the elevation of ANF is reflective of ductal flow.

Age Factors↗
PubMed1987

Insidious hydrocephalus in the preterm newborn following discharge from the nursery.

Posthemorrhagic ventriculomegaly may be due to perinatal brain damage and consequent cerebral atrophy, or represent progressive hydrocephalus due to impairment of CSF flow and reabsorption. 'Arrested' hydrocephalus occurs when the CSF pathways are adequate and, hence, intracranial hypertension no longer exists. The differential diagnosis is often difficult and insidious progressive hydrocephalus should always be a concern in the high-risk preterm newborn. We report 10 preterm infants who were discharged with the diagnosis of arrested hydrocephalus (7) or cerebral atrophy (3), and who later developed progressive severe hydrocephalus 1.5-15 months after the discharge. Five had been treated with intermittent lumbar punctures, while 4 had not received any treatment prior to nursery discharge. One infant died prior to the shunt procedure. Progressive insidious hydrocephalus should be suspected in preterm infants with intracranial hemorrhage following discharge from the nursery.

Cerebral Ventricles↗