Gregory R. Cook

Coumarin-suberoylanilide hydroxamic acid as a fluorescent probe for determining binding affinities and off-rates of histone deacetylase inhibitors

Histone deacetylases (HDACs) are intimately involved in epigenetic regulation and, thus, are one of the key therapeutic targets for cancer, and two HDAC inhibitors, namely suberoylanilide hydroxamic acid (SAHA) and romidepsin, have been recently approved for cancer treatment. Because the screening and detailed characterization of HDAC inhibitors has been time-consuming, we synthesized coumarin-SAHA (c-SAHA) as a fluorescent probe for determining the binding affinities (K(d)) and the dissociation off-rates (k(off)) of the enzyme-inhibitor complexes. The determination of the above parameters relies on the changes in the fluorescence emission intensity (λ(ex)=325 nm, λ(em)=400 nm) of c-SAHA due to its competitive binding against other HDAC inhibitors, and such determination neither requires employment of polarization accessories nor is dependent on the fluorescence energy transfer from the enzymes tryptophan residues to the probe. Our highly sensitive and robust analytical protocol presented here is applicable to most of the HDAC isozymes, and it can be easily adopted in a high-throughput mode for screening the HDAC inhibitors as well as for quantitatively determining their K(d) and k(off) values.

Aza-annulation as a route to hydroxylated alkaloid lipids. The synthesis of (±)-prosopinine

Abstract The total synthesis of (±)-prosopinine is described. Aza-annulation was used to generate the six-membered nitrogen heterocycle, stereochemical control was achieved through the use of the δ-lactam template, and homologation of the lactam introduced the alkyl chain substituent on the piperidine ring.

Asymmetric synthesis of aminochromanes via intramolecular indium-mediated allylation of chiral hydrazones.

The asymmetric intramolecular indium-mediated cyclization reaction delivers chromanes with excellent diastereoselectivity (68-91% yield, dr >99:1). The reaction was efficient for aryl substrates with both electron-withdrawing and -donating groups. Carboxylic acid additives were found to be necessary for optimal reaction.

Stereoselective synthesis of d-erythro- and l-threo-sphinganines via palladium-catalyzed equilibration and Suzuki coupling

Abstract The Pd-catalyzed isomerization of 5-vinyloxazolines was utilized for the stereoselective synthesis of d - erythro - and l - threo -spinganine triacetate. A hydroboration/Suzuki coupling sequence was employed to elongate the hydrophobic chain.

Enantioselective reduction of ketones. Examination of bifunctional ligands

Abstract New bifunctional ligands based on a cis -amino indanol framework have been evaluated in the reduction of prochiral ketones. These reductions proceed with high chemical efficiency and good-to-excellent enantioselectivity using borane and 10 mol% of an oxazaborolidine derived from cis -2-amino indanol ligand containing a 2-sulfonylpyridyl tether attached to the amino group.

Reversal of stereochemistry in diethylzinc addition to aldehydes by a simple change of the backbone substituent in L-serine derived ligands

Abstract A change in the backbone substituent from phenyl to butyl group in L-serine-derived ligands provides a simple way to prepare enantiomeric products in diethylzinc addition to aldehydes. A change in the backbone substituent from phenyl ( 4 ) to butyl group ( 10 ) in L -serine-derived ligands provides a simple way to prepare enantiomeric products in diethylzinc addition to aldehydes. Download full-size image

Palladium-Mediated Dynamic Kinetic Resolution: Stereoselective Synthesis of Vicinal Diamines

Can an adjacent stereocenter control selectivity in the palladium-catalyzed allylic substitution reaction? If the intermediate π-allyl palladium complex can undergo rapid inversion, the answer is yes (see reaction scheme). Starting from chiral 5-vinyloxazolidinones, trapping of intermediates 1 and 2, which are in a dynamic equilibrium, with nitrogen-containing nucleophiles leads to the quantitative formation of diamines as single diastereomers.

PALLADIUM-CATALYZED FORMATION AND STEREOSELECTIVE ISOMERIZATION OF 5-VINYLOXAZOLINES. APPLICATION TO THE FORMAL SYNTHESIS OF (S, S)-4-AMINO-3-HYDROXY- 5-PHENYLPENTANOIC ACID

Abstract Vinyloxazolidinones have been found to undergo Pd(0)-catalyzed ionization followed by loss of carbon dioxide and subsequent cyclization to form vinyloxazolines. The reaction occurred under mild conditions, and enhancement of diastereomeric ratios with chiral substrates was obtained. 4-Benzyl-5-vinyloxazoline prepared by this method has been utilized in the stereoselective synthesis of (S,S)-4-amino-3-hydroxy-5-phenylpentanoic acid (AHPPA).

Histone deacetylase activators: N-acetylthioureas serve as highly potent and isozyme selective activators for human histone deacetylase-8 on a fluorescent substrate

We report, for the first time, that certain N-acetylthiourea derivatives serve as highly potent and isozyme selective activators for the recombinant form of human histone deacetylase-8 in the assay system containing Fluor-de-Lys as a fluorescent substrate. The experimental data reveals that such activating feature is manifested via decrease in the K(m) value of the enzymes substrate and increase in the catalytic turnover rate of the enzyme.

CHLORIDE EFFECT ON THE PALLADIUM-CATALYZED ALLYLIC SUBSTITUTION VS ELIMINATION OF CYCLIC VINYLOXAZOLIDINONES AND OXAZOLINES

Abstract The introduction of catalytic amounts of lithium chloride, or the utilization of chloride containing catalyst sources completely inhibited elimination in the Pd-catalyzed allylic substitution of vinyloxazolidinones and oxazolines.