Synthesis of racemic cis-5-hydroxy-3-phthalimidoglutarimide. A metabolite of thalidomide isolated from human plasma

[reaction: see text] A synthesis of the glutarimide-derived metabolite of thalidomide, 5'-hydroxythalidomide (2), is described. The synthesis employed the lactone derivative of N-benzyloxycarbonyl (CBZ)-protected 4-hydroxyglutamic acid 12, which is prepared by a de novo route from diethyl acetamidomalonate. The reaction of 12 with 4-methoxybenzylamine gave the corresponding isoglutamine, which then provided the key CBZ-protected N-PMB-glutarimide 14 after dehydration. Deprotection of both the CBZ and PMB groups followed by phthalimidation and deacetylation of the 3-amino-5-acetoxyglutarimide 16 afforded 2.     

Cross‐Linked Aptamer–Lipid Micelles for Excellent Stability and Specificity in Target‐Cell Recognition

The specific binding ability of DNA–lipid micelles (DLMs) can be increased by the introduction of an aptamer. However, supramolecular micellar structures based on self‐assemblies of amphiphilic DLMs are expected to demonstrate low stability when interacting with cell membranes under certain conditions, which could lead to a reduction in selectivity for targeting cancer cells. We herein report a straightforward cross‐linking strategy that relies on a methacrylamide branch to link aptamer and lipid segments. By an efficient photoinduced polymerization process, covalently linked aptamer–lipid units help stabilize the micelle structure and enhance aptamer probe stability, further improving the targeting ability of the resulting nanoassembly. Besides the development of a facile cross‐linking method, this study clarifies the relationship between aptamer–lipid concentration and the corresponding binding ability.     

Development and validation of an LC-MS assay for finasteride and its application to prostate cancer prevention trial sample analysis

An analytical method is developed and validated for the quantitative determination of finasteride, a potent 5 alpha-reductase inhibitor, in human plasma. Calibration curves are linear in the concentration range of 1 to 100 ng/mL. Sample pretreatment involves a liquid-liquid extraction with ethyl acetate using 0.2 mL aliquots of plasma. Finasteride and the internal standard (beclomethasone) are separated on a Waters Symmetry Shield RP18 column (50 x 2.1 mm, 3.5 microm) and eluted using a gradient mobile phase composed of acetonitrile and 10mM ammonium acetate with 0.1% formic acid. The column eluant is monitored by mass spectrometry with electrospray ionization. A complete validation of the method is performed. For quality control samples at three different concentrations that were analyzed in quintuplicate, on six separate occasions, the accuracy and precision range from 95.2% to 101% and 3.4% to 7.3%, respectively. The developed method is subsequently applied to measure the steady state finasteride concentration of patients who participated in the Prostate Cancer Prevention Trial.     

A high-performance liquid chromatography method using ultraviolet and fluorescence detection for the quantitation of UCN-01, 7-hydroxystaurosporine, from human plasma and saliva

UCN-01, 7-hydroxystaurosporine, is an antagonist of protein kinase C, as well as causing cell cycle arrest. We developed and validated an HPLC assay method for the quantitation of UCN-01. Plasma and saliva standard curves were prepared at concentrations ranging from 0.2 to 20.0 microgram/mL and 4.0 to 200.0 ng/mL, respectively. The sample preparation consisted of acetonitrile precipitation. Separation was accomplished on a phenyl column and a C-18 precolumn insert utilizing a gradient-profile consisting of ammonium acetate and acetonitrile. UV detection was set at 295 nm for UCN-01 and 323 nm for umbelliferone, the internal standard. For fluorescence detection, excitation occurred at 290 nm, while emission was at 400 nm. The retention times were around 4 min for umbelliferone and 9.1 for UCN-01. Inter- and intra-assay errors of accuracy were less than 7. 0% and 10.7%, respectively, for the plasma standard curve and less than 7.1% and 6.7%, respectively, for the saliva standard curve. The recoveries of UCN-01 and umbelliferone from saliva were 81.4 +/- 0. 9% and 106.3 +/- 10.2%, respectively. The recovery of UCN-01 from plasma was 97.9 +/- 7.1% and for umbelliferone was 103.3 +/- 2.3%. This method is suitable for quantifying UCN-01 in patient samples and further characterizing the clinical pharmacology of this compound. Published in 2000 by John Wiley & Sons, Ltd.     

A high-performance liquid chromatography method using ultraviolet detection for the quantitation of flavopiridol from human plasma

Flavopiridol is an inhibitor of cyclin-dependent kinase, a key regulator of cell cycle, and is currently under clinical trials. We developed and validated an HPLC assay method for the quantitation of flavopiridol in human plasma samples. The sample preparation consisted of protein precipitation with acetonitrile. Separation was accomplished on a C(18) column and a C(18) precolumn insert utilizing a gradient profile consisting of ammonium acetate and methanol. Ultraviolet detection was set at 268 nm for flavopiridol and 323 nm for umbelliferone, the internal standard. The method was validated over flavopiridol concentration range of 0.025-3.0 microg/mL using 250 microL of plasma. The assay was linear over this concentration range with a coefficient of variation less than 10% for inter- and intra-assay. The retention times were around 6.2 min for umbelliferone and 9.8 min for flavopiridol. The recoveries of flavopiridol and umbelliferone were 88.6 +/- 1.0% and 97.1 +/- 3.7%, respectively. This method is suitable for quantifying flavopiridol in plasma samples and further characterizing the clinical pharmacology of this compound.     

Closed‐System One‐Pot Block Copolymerization by Temperature‐Modulated Monomer Segregation

A biphasic one‐pot polymerization method enables the preparation of block copolymers from monomers with similar and competitive reactivities without the addition of external materials. AB diblock copolymers were prepared by encapsulating a frozen solution of monomer B on the bottom of a reaction vessel, while the solution polymerization of monomer A was conducted in a liquid layer above. Physical separation between the solid and liquid phases permitted only homopolymerization of monomer A until heating above the melting point of the lower phase, which released monomer B, allowing the addition of the second block to occur. The triggered release of monomer B allowed for chain extension without additional deoxygenation steps or exogenous monomer addition. A method for the closed (i.e., without addition of external reagents) one‐pot synthesis of block copolymers with conventional glassware using straightforward experimental techniques has thus been developed.     

Carbon-oxygen bond formation via organometallic Baeyer-Villiger transformations: a computational study on the impact of metal identity

Metal-mediated formation of C-O bonds is an important transformation that can occur by a variety of mechanisms. Recent studies suggest that oxygen-atom insertion into metal-hydrocarbyl bonds in a reaction that resembles the Baeyer-Villiger transformation is a viable process. In an effort to identify promising new systems, this study is designed to assess the impact of metal identity on such O-atom insertions for the reaction [(bpy)(x)M(Me)(OOH)](n) → [(bpy)(x)M(OMe)(OH)](n) (x = 1 or 2; bpy = 2,2'-bipyridyl; n is varied to maintain the d-electron count at d(6) or d(8)). Six d(8)-square-planar complexes (M = Pt(II), Pd(II), Ni(II), Ir(I), Rh(I), and Co(I)) and eight d(6)-octahedral systems (M = Ir(III), Rh(III), Co(III), Fe(II) Ru(II), Os(II), Mn(I), and Tc(I)) are studied. Using density functional theory calculations, the structures and energies of ground-state and transition-state species are elucidated. This study shows clear trends in calculated ΔG(++)'s for the O-atom insertions. The organometallic Baeyer-Villiger insertions are favored by lower coordination numbers (x = 1 versus x = 2), earlier transition metals, and first-row (3d) transition metals.     

Cooperativity between low-valent iron and potassium promoters in dinitrogen fixation

A density functional theory (DFT) study was performed to understand the role of cooperativity between iron-β-diketiminate fragments and potassium promoters in N(2) activation. Sequential addition of iron fragments to N(2) reveals that a minimum of three Fe centers interact with N(2) in order to break the triple bond. The potassium promoter stabilizes the N(3-) ligand formed upon N(2) scission, thus making the activated iron nitride complex more energetically accessible. Reduction of the complex and stabilization of N(3-) by K(+) have similar impact on the energetics in the gas phase. However, upon inclusion of continuum THF solvent effects, coordination of K(+) has a reduced influence upon the overall energetics of dinitrogen fixation; thus, reduction of the trimetallic Fe complex becomes more impactful than coordination of K(+) vis-à-vis N(2) activation upon the inclusion of solvent effects.