Paul Helquist

Histone deacetylase inhibitor treatment dramatically reduces cholesterol accumulation in Niemann-Pick type C1 mutant human fibroblasts

Niemann-Pick type C (NPC) disease is predominantly caused by mutations in the NPC1 protein that affect intracellular cholesterol trafficking and cause accumulation of unesterified cholesterol and other lipids in lysosomal storage organelles. We report the use of a series of small molecule histone deacetylase (HDAC) inhibitors in tissue culture models of NPC human fibroblasts. Some HDAC inhibitors lead to a dramatic correction in the NPC phenotype in cells with either one or two copies of the NPC1I1061T mutation, and for several of the inhibitors, correction is associated with increased expression of NPC1 protein. Increased NPC1I1061T protein levels may partially account for the correction of the phenotype, because this mutant can promote cholesterol efflux if it is delivered to late endosomes and lysosomes. The HDAC inhibitor treatment is ineffective in an NPC2 mutant human fibroblast line. Analysis of the isoform selectivity of the compounds used implicates HDAC1 and/or HDAC2 as likely targets for the observed correction, although other HDACs may also play a role. LBH589 (panobinostat) is an orally available HDAC inhibitor that crosses the blood–brain barrier and is currently in phase III clinical trials for several types of cancer. It restores cholesterol homeostasis in cultured NPC1 mutant fibroblasts to almost normal levels within 72 h when used at 40 nM. The findings that HDAC inhibitors can correct cholesterol storage defects in human NPC1 mutant cells provide the potential basis for treatment options for NPC disease.

Prediction of enantioselectivity in rhodium catalyzed hydrogenations.

Using the Q2MM method, new molecular mechanics parameters were developed to perform initial screening of a chiral library to focus the experimental screening for the rhodium catalyzed hydrogenation of enamides. Computational predictions agree very well with experimental data.

Synthesis of primary aryl amines through a copper-assisted aromatic substitution reaction with sodium azide.

A method is presented by which aryl halides and azides are converted to the corresponding primary aryl amines with copper(I) and sodium azide.

Inhibition of Histone Deacetylases: A Pharmacological Approach to the Treatment of Non-Cancer Disorders

The dynamics of gene expression are regulated by histone acetylases (HATs) and histone deacetylases (HDACs) that control the acetylation state of lysine side chains of the histone proteins of chromatin. The catalytic activity of these two enzymes remodels chromatin to control gene expression without altering gene sequence. Treatment of cancer has been the primary target for the clinical development of HDAC inhibitors, culminating in approval for the first HDAC inhibitor for the treatment of cutaneous T cell lymphoma. Beyond cancer, HDAC inhibition has potential for the treatment of many other diseases. The HDAC inhibitors phenylbutyric acid, valproic acid, and suberoylanilide hydroxamic acid (SAHA) have been shown to correct errant gene expression, ameliorate the progression of disease, and restore absent synthetic or metabolic activities for a diverse group of non-cancer disorders. These benefits have been found in patients with sickle cell anemia, HIV, and cystic fibrosis. In vitro and in vivo models of spinal muscular atrophy, muscular dystrophy, and neurodegenerative, and inflammatory disorders also show response to HDAC inhibitors. This review examines the application of HDAC inhibition as a treatment for a wide-range of non-cancer disorders, many of which are rare diseases that urgently need therapy. Inhibition of the HDACs has general potential as a pharmacological epigenetic approach for gene therapy.

Selective oxidation of benzylic and allylic alcohols using Mn(OAc)3/catalytic 2,3-dichloro-5,6-dicyano-1,4-benzoquinone.

A practical, chemoselective oxidation of alcohols employing catalytic quantities of DDQ as the oxidant and Mn(OAc)(3) as the co-oxidant is described. Electron-rich benzylic alcohols are oxidized efficiently to their corresponding carbonyls, but less electron-rich benzylic alcohols remain unchanged. Allylic alcohols are rapidly oxidized to their corresponding aldehyde or ketone counterparts in high yields. This protocol is operationally simple, employs an inexpensive source of Mn(OAc)(3), has short reaction times, and exhibits a significant chemoselectivity favoring allylic alcohols over benzylic alcohols. This procedure also avoids the use of very large excesses of reagents and sometimes poor reproducibility that characterize previously developed reagents such as MnO(2).

Functionalized oxazoles from rhodiumi-catalyzed reaction of dimethyl diazomalonate with nitriles☆

Abstract Rhodium(II) acetate catalyzes the reaction of dimethyl diazomalonate with nitriles to give 4-carbomethoxy-5-methoxy-1,3-oxazo1es. Oxazole formation exceeds cyclopropane formation even in cases of conjugated and non-conjugated unsaturated nitriles.

Thiadiazole carbamates: potent inhibitors of lysosomal acid lipase and potential Niemann-Pick type C disease therapeutics.

Niemann-Pick type C (NPC) disease is a lysosomal storage disorder characterized at the cellular level by abnormal accumulation of cholesterol and other lipids in lysosomal storage organelles. Lysosomal acid lipase (LAL) has been recently identified as a potential therapeutic target for NPC. LAL can be specifically inhibited by a variety of 3,4-disubstituted thiadiazole carbamates. An efficient synthesis of the C(3) oxygenated/C(4) aminated analogues has been developed that furnishes the products in high yields and high degrees of purity. Common intermediates can also be used for the synthesis of the C(3) carbon substituted derivatives. Herein we tested various thiadiazole carbamates, amides, esters, and ketones for inhibition of LAL. In addition, we tested a diverse selection of commercially available non-thiadiazole carbamates. Our studies show that, among the compounds examined herein, only thiadiazole carbamates are effective inhibitors of LAL. We present a mechanism for LAL inhibition by these compounds whereby LAL transiently carbamoylates the enzyme similarly to previously described inhibition of acetylcholinesterase by rivastigmine and other carbamates as well as acylation of various lipases by orlistat.

Intramolecular hydroamination of aminoalkynes with silver-phenanthroline catalysts.

Intramolecular hydroamination of several aminoalkynes catalyzed by silver-phenanthroline complexes is reported. This catalyst system complements previous protocols by employing air- and moisture-stable complexes without compromising activity or reaction control. Some of the hydroamination products are subject to a useful aerobic oxidation. Silver-phenanthroline complexes have successfully demonstrated efficacy in the desymmetrization of a prochiral diyne.

Development of a Q2MM Force Field for the Asymmetric Rhodium Catalyzed Hydrogenation of Enamides

The rhodium catalyzed asymmetric hydrogenation of enamides to generate amino acid products and derivatives is a widely used method to generate unnatural amino acids. The choice of a chiral ligand is of utmost importance in this reaction and is often based on high throughput screening or simply trial and error. A virtual screening method can greatly increase the speed of the ligand screening process by calculating expected enantiomeric excesses from relative energies of diastereomeric transition states. Utilizing the Q2MM method, new molecular mechanics parameters are derived to model the hydride transfer transition state in the reaction. The new parameters were based off of structures calculated at the B3LYP/LACVP** level of theory and added to the MM3* force field. The new parameters were validated against a test set of experimental data utilizing a wide range of bis-phosphine ligands. The computational model agreed with experimental data well overall, with an unsigned mean error of 0.6 kcal/mol against a set of 18 data points from experiment. The major errors in the computational model were due either to large energetic errors at high e.e., still resulting in qualitative agreement, or cases where large steric interactions prevent the reaction from proceeding as expected.

Enantioselective synthesis of salmeterol via asymmetric borane reduction

Abstract Enantioselective syntheses of both enantiomers of salmeterol are accomplished using asymmetric borane reductions with chiral oxazaborolidines as catalysts.