James L. Gleason

Incorporation of histone deacetylase inhibition into the structure of a nuclear receptor agonist

1,25-dihydroxyvitamin D3 (1,25D) regulates gene expression by signaling through the nuclear vitamin D receptor (VDR) transcription factor and exhibits calcium homeostatic, anticancer, and immunomodulatory properties. Histone deacetylase inhibitors (HDACis) alter nuclear and cytoplasmic protein acetylation, modify gene expression, and have potential for treatment of cancer and other indications. The function of nuclear receptor ligands, including 1,25D, can be enhanced in combination with HDACi. We designed triciferol, a hybrid molecule in which the 1,25D side chain was replaced with the dienyl hydroxamic acid of HDACi trichostatin A. Triciferol binds directly to the VDR, and functions as an agonist with 1,25D-like potency on several 1,25D target genes. Moreover, unlike 1,25D, triciferol induces marked tubulin hyperacetylation, and augments histone acetylation at concentrations that largely overlap those where VDR agonism is observed. Triciferol also exhibits more efficacious antiproliferative and cytotoxic activities than 1,25D in four cancer cell models in vitro. The bifunctionality of triciferol is notable because (i) the HDACi activity is generated by modifying the 1,25D side chain without resorting to linker technology and (ii) 1,25D and HDACi have sympathetic, but very distinct biochemical targets; the hydrophobic VDR ligand binding domain and the active sites of HDACs, which are zinc metalloenzymes. These studies demonstrate the feasibility of combining HDAC inhibition with nuclear receptor agonism to enhance their therapeutic potential.

Stereoselective formation of alpha-quaternary stereocenters in the Mannich reaction.

Condensation of alpha,alpha-disubstituted lithium enolates derived from bicyclic thioglycolate lactams with benzenesulfonyl imines affords Mannich addition products with excellent diastereoselectivity. Cleavage of the auxiliary under hydrolytic or reducing conditions affords beta-amino acids and alcohols, respectively.

Docking ligands into flexible and solvated macromolecules. 6. Development and application to the docking of HDACs and other zinc metalloenzymes inhibitors.

Metalloenzymes are ubiquitous proteins which feature one or more metal ions either directly involved in the enzymatic activity and/or structural properties (i.e., zinc fingers). Several members of this class take advantage of the Lewis acidic properties of zinc ions to carry out their various catalytic transformations including isomerization or amide cleavage. These enzymes have been validated as drug targets for a number of diseases including cancer; however, despite their pharmaceutical relevance and the availability of crystal structures, structure-based drug design methods have been poorly and indirectly parametrized for these classes of enzymes. More specifically, the metal coordination component and proton transfers of the process of drugs binding to metalloenzymes have been inadequately modeled by current docking programs, if at all. In addition, several known issues, such as coordination geometry, atomic charge variability, and a potential proton transfer from small molecules to a neighboring basic residue, have often been ignored. We report herein the development of specific functions and parameters to account for zinc-drug coordination focusing on the above-listed phenomena and their impact on docking to zinc metalloenzymes. These atom-type-dependent but atomic charge-independent functions implemented into Fitted 3.1 enable the simulation of drug binding to metalloenzymes, considering an acid-base reaction with a neighboring residue when necessary with good accuracy.

Vitamin D receptor agonist/histone deacetylase inhibitor molecular hybrids

Incorporation of zinc-binding groups into the side-chain of 1alpha,25-dihydroxyvitamin D(3) (1,25D) fully bifunctional hybrid molecules which act both as vitamin D receptor agonists and histone deacetylase inhibitors. These bifunctional hybrids display in vitro antiproliferative activity against the AT84 squamous carcinoma cell line while lacking the in vivo hypercalcemic effects of 1,25D.

A one-step synthesis of pseudoephedrine glycinamide, a versatile precursor for the synthesis of α-amino acids

Abstract Both enantiomers of pseudoephedrine glycinamide [(+)- or (−)- 1 ] were synthesized by either of two procedures: (1) a standard two-step coupling of N -Boc-Gly with pseudoephedrine followed by deprotection, or (2) a more economical one-step coupling reaction of Gly-OMe with pseudoephedrine mediated by LiCl and base.

Synthetically Accessible Non-Secosteroidal Hybrid Molecules Combining Vitamin D Receptor Agonism and Histone Deacetylase Inhibition

1,25-Dihydroxyvitamin D(3) (1,25D), the hormonal form of vitamin D, and several analogs have failed as monotherapies for cancer because of poor efficacy or acquired resistance. However, 1,25D analogs are amenable to bifunctionalization. Preclinical studies have revealed combinatorial effects of 1,25D analogs and histone deacetylase inhibitors (HDACi). Secosteroidal hybrid molecules combining vitamin D receptor (VDR) agonism with HDACi displayed enhanced efficacy but are laborious to synthesize. Here, we have developed easily assembled, fully integrated, non-secosteroidal VDR agonist/HDACi hybrids. The most promising are full VDR agonists with ~10-fold lower potency than 1,25D. Structure/function studies revealed that antiproliferative activity against 1,25D-resistant squamous carcinoma cells required VDR agonism and HDACi. Remarkably, modeling and X-ray crystallography reveal non-secosteroidal hybrids bind in the VDR ligand binding domain in the opposite orientation of their secosteroidal counterparts.

Antiestrogens: structure activity relationships and use in breast cancer treatment

About 70% of breast tumors express estrogen receptor alpha (ERα), which mediates the proliferative effects of estrogens on breast epithelial cells, and are candidates for treatment with antiestrogens, steroidal or non-steroidal molecules designed to compete with estrogens and antagonize ERs. The variable patterns of activity of antiestrogens (AEs) in estrogen target tissues and the lack of systematic cross-resistance between different types of molecules have provided evidence for different mechanisms of action. AEs are typically classified as selective estrogen receptor modulators (SERMs), which display tissue-specific partial agonist activity (e.g. tamoxifen and raloxifene), or as pure AEs (e.g. fulvestrant), which enhance ERα post-translational modification by ubiquitin-like molecules and accelerate its proteasomal degradation. Characterization of second- and third-generation AEs, however, suggests the induction of diverse ERα structural conformations, resulting in variable degrees of receptor downregulation and different patterns of systemic properties in animal models and in the clinic.

An o-Aminoanilide Analogue of 1α,25-Dihydroxyvitamin D3 Functions as a Strong Vitamin D Receptor Antagonist

Vitamin D receptor (VDR) antagonists have therapeutic potential in treatment of allergic conditions and hypercalcemia driven by granulomatous diseases. We have identified an o-aminoanilide analogue of the hormonal form of vitamin D with a dienyl side chain that functions as a strong VDR antagonist. Modeling studies indicate that antagonism arises from side chain rigidity, when compared to a more flexible saturated analogue, which interferes with H12 folding/alignment.

Preparation of active esters on solid support for aqueous-phase peptide couplings

TentaGel supported active esters analogous to those prepared from solution-phase reagents such as 1-hydroxybenzotriazole, N-hydroxysuccinimide, and pentafluorophenol were prepared and examined for their ability to effect aqueous-phase peptide couplings. HOBt esters showed high hydrolysis rates, relative to peptide coupling, while active esters derived from 4-hydroxy-2,3,5,6-tetrafluorobenzoic acid produced mainly dipeptide coupling products when treated with amino acids in water.

A Concise Total Synthesis of (R)‐Puraquinonic Acid

isolated from mycelial cultures of Mycena Pura and which possesses mild differentiation-inducing activity towards HL60 cells, is an intriguing example of a molecule containing a challenging quaternary stereocenter. The majority of illudalane sesquiterpenoids contain geminal dimethyl groups at C11, which are either prochiral or diastereotopic. In contrast, in the structure of 1, one of the methyl groups of the geminal dimethyl groups has undergone oxidation resulting in a new quaternary stereocenter. Importantly, the stereodefining groups in 1, the methyl and hydroxyethyl groups, are far removed from the stereocenter and offer only a minimum of electronic differentiation. Thus, while 1 may appear at first glance to be a simple molecule, its synthesis in enantiopure form is a significant challenge. Indeed, while an efficient 10step synthesis of racemic 1 has been reported, the only enantioselective synthesis of 1 exceeds 30 steps in length. We have previously developed a method for the formation of quaternary stereocenters based on the stereoselective generation and alkylation of a,a-disubstituted amide enolates from easily prepared bicyclic thioglycolate lactam 3 (Scheme 2). Sequential double alkylation of bicyclic lactam 3 followed by a dissolving metal reduction results in stereoselective formation of an a,a-disubstituted enolate (5), where the enolate geometry is regulated by the combination of the conformation of the starting bicycle and the configuration of the a-stereocenter. The resulting enolate possesses a C2-pseudosymmetric auxiliary and undergoes highly diastereoselective alkylations (6) and Mannich additions (7). Importantly, the stereoselectivity of enolate generation and subsequent alkylation is based on the order of alkylation and not the size of the substituents, such that quaternary stereocenters bearing three groups of nearly identical size (e.g. ethyl, propyl, and allyl) can be formed with excellent stereoselectivity. We felt that this method would be ideal for the synthesis of 1, because it would allow for an early-stage introduction of the quaternary stereocenter. Our retrosynthetic analysis (Scheme 3) suggested that the quinoid ring in 1 might be generated by oxidation of a Diels– Alder adduct of dimethyl acetylenedicarboxylate 10 and diene 9. Diene 9 could be envisaged as coming from a tandem ring-closing ene–yne/diene–ene cross metathesis of 1,6-enyne 11 and 3-buten-1-ol. Finally, we fully expected that 11 could be generated stereoselectively through a dialkylation/reduction/alkylation sequence using thioglycolate lactam 3. ImporScheme 1. Structure of (R)-puraquinonic acid and the illudalane skeleton.