115 research outputs found
Switching the stereochemical outcome of 6-endo-trig cyclizations; Synthesis of 2,6-Cis-6-substituted 4-oxopipecolic acids
A base-mediated 6-endo-trig cyclization of
readily accessible enone-derived α-amino acids has been
developed for the direct synthesis of novel 2,6-cis-6-
substituted-4-oxo-L-pipecolic acids. A range of aliphatic and
aryl side chains were tolerated by this mild procedure to give
the target compounds in good overall yields. Molecular
modeling of the 6-endo-trig cyclization allowed some insight as
to how these compounds were formed, with the enolate
intermediate generated via an equilibrium process, followed by irreversible tautomerization/neutralization providing the driving force for product formation. Stereoselective reduction and deprotection of the resulting 2,6-cis-6-substituted 4-oxo-L-pipecolic acids to the corresponding 4-hydroxy-L-pipecolic acids was also performed
Dating the detachment fault system of the Ruby Mountains, Nevada: Significance for the kinematics of low‐angle normal faults
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94601/1/tect2138.pd
Quantification of three macrolide antibiotics in pharmaceutical lots by HPLC: Development, validation and application to a simultaneous separation
A new validated high performance liquid chromatographic (HPLC) method with rapid analysis time and high efficiency, for the analysis of erythromycin, azithromycin and spiramycin, under isocratic conditions with ODB RP18 as a stationary phase is described. Using an eluent composed of acetonitrile –2-methyl-2-propanol –hydrogenphosphate buffer, pH 6.5, with 1.5% triethylamine (33:7: up to 100, v/v/v), delivered at a flow-rate of 1.0 mL min-1. Ultra Violet (UV) detection is performed at 210 nm. The selectivity is satisfactory enough and no problematic interfering peaks are observed. The procedure is quantitatively characterized and repeatability, linearity, detection and quantification limits are very satisfactory. The method is applied successfully for the assay of the studied drugs in pharmaceutical dosage forms as tablets and powder for oral suspension. Recovery experiments revealed recovery of 97.13–100.28%
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