Ling-Wei Hsin

Quinazolin-4-one Derivatives as Selective Histone Deacetylase-6 Inhibitors for the Treatment of Alzheimer’s Disease

Novel quinazolin-4-one derivatives containing a hydroxamic acid moiety were designed and synthesized. All compounds were subjected to histone deacetylase (HDAC) enzymatic assays to identify selective HDAC6 inhibitors with nanomolar IC50 values. (E)-3-(2-Ethyl-7-fluoro-4-oxo-3-phenethyl-3,4-dihydroquinazolin-6-yl)-N-hydroxyacrylamide, 4b, is the most potent HDAC6 inhibitor (IC50, 8 nM). In vitro, these compounds induced neurite outgrowth accompanied by growth-associated protein 43 expression, and they enhanced the synaptic activities of PC12 and SH-SY5Y neuronal cells without producing toxic or mitogenic effects. Several of the compounds dramatically increased nonhistone protein acetylation, specifically of α-tubulin. Some of the more potent HDAC6 inhibitors decreased zinc-mediated β-amyloid aggregation in vitro. N-Hydroxy-3-(2-methyl-4-oxo-3-phenethyl-3,4-dihydro-quinazolin-7-yl)-acrylamide, 3f, the most promising drug candidate, selectively inhibits HDAC6 (IC50, 29 nM), practically does not affect human ether-a-go-go-related membrane channel activity (IC50 >10 μM) or cytochrome P450 activity (IC50 >6.5 μM) in vitro, and significantly improves learning-based performances of mice with β-amyloid-induced hippocampal lesions.

CRHR1 receptor binding and lipophilicity of pyrrolopyrimidines, potential nonpeptide corticotropin-releasing hormone type 1 receptor antagonists

A series of compounds related to N-butyl-N-ethyl[2,5,6-trimethyl-7-(2,4,6-trimethylphenyl)pyrrolo[2,3-d]pyrimidin-4-yl]amine (1, antalarmin) have been prepared and evaluated for their CRHR1 binding affinity as the initial step in the development of selective high affinity hydrophilic nonpeptide corticotropin-releasing hormone type 1 receptor (CRHR1) antagonists. Calculated log P (Clog P) values were used to evaluate the rank order of hydrophilicity for these analogues. Introducing oxygenated functionalities (delta-hydroxy or bis-beta-ethereal) into 1 gave more hydrophilic compounds, which had good affinity for the receptor. Introducing an amino group or shortening the alkyl side chain was detrimental to CRHR1 affinity. The alcohol 4-[ethyl[2,5,6-trimethyl-7-(2,4,6-trimethylphenyl)pyrrolo[2,3-d]pyrimidin-4-yl]amino]butan-1-ol (3), bearing a terminal hydroxyl group on an N-alkyl side-chain, showed the highest CRHR1 binding affinity among these compounds (K(i)=0.68 nM), and is one of the highest affinity CRHR1 ligands known. Compounds 3-5, and 8, which are likely to be less lipophilic than 1, have high CRHR1 affinity and may be valuable probes to further study the CRH system.

N-Cubylmethyl substituted morphinoids as novel narcotic antagonists

N-Cubylmethylnormorphine (1) and N-cubylmethylnoroxymorphone (2) have been synthesized and found to be more potent ligands at the mu and kappa opioid receptors than morphine and oxymorphone respectively. In the guinea-pig ileum preparation, compounds 1 and 2 were characterized as opioid mu antagonists (Ke = 68 and 16 nM, respectively). Compound 2 also showed effective kappa-antagonism (Ke = 22 nM). The narcotic antagonism activity of 1 has been confirmed by in vivo assays.

Synthesis and biological activity of fluoro-substituted pyrrolo[2,3-d]pyrimidines: the development of potential positron emission tomography imaging agents for the corticotropin-releasing hormone type 1 receptor.

A series of fluoro-substituted 4-(dialkylamino)pyrrolo[2,3-d]pyrimidines was synthesized and their binding affinity for corticotropin-releasing hormone type 1 receptor (CRHR1) was investigated. Compounds 11a and 11b possessed very high CRHR1 affinity (Ki=3.5, 0.91 nM, respectively). They are promising candidates for the development of 18F-containing nonpeptide PET radioligands for CRHR1.

N-Arylated pyrrolidin-2-ones and morpholin-3-ones as potassium channel openers

Based on the most stable conformation of ZD6169, a series of N-arylated derivatives of oxazolidindione (2), morpholin-3-one (3-5), piperidin-2-one (6), and pyrrolidin-2-one (7-13) was synthesized and evaluated for potassium channel opening activity. In the in-vitro assays, N-(4-benzoylphenyl)-piperidin-2-on (6) and N-(4-benzoylphenyl)-3,3-dimethyl-pyrrolidin-2-one (9) demonstrated potent and selective relaxant activity at the bladder detrusor muscle [IC50, bladder)=7.4 and 6.7 microM, respectively; IC50 ratio (portal vein/bladder)=41 and 51, respectively].

Identification of a novel “almost neutral” μ‐opioid receptor antagonist in CHO cells expressing the cloned human μ‐opioid receptor

The basal (constitutive) activity of G protein‐coupled receptors allows for the measurement of inverse agonist activity. Some competitive antagonists turn into inverse agonists under conditions where receptors are constitutively active. In contrast, neutral antagonists have no inverse agonist activity, and they block both agonist and inverse agonist activity. The μ‐opioid receptor (MOR) demonstrates detectable constitutive activity only after a state of dependence is produced by chronic treatment with a MOR agonist. We therefore sought to identify novel MOR inverse agonists and novel neutral MOR antagonists in both untreated and agonist‐treated MOR cells. CHO cells expressing the cloned human mu receptor (hMOR‐CHO cells) were incubated for 20 h with medium (control) or 10 μM (2S,4aR,6aR,7R,9S,10aS,10bR)‐9‐(benzoyloxy)‐2‐(3‐furanyl)dodecahydro‐6a,10b‐dimethyl‐4,10‐dioxo‐2H‐naphtho‐[2,1‐c]pyran‐7‐carboxylic acid methyl ester (herkinorin, HERK). HERK treatment generates a high degree of basal signaling and enhances the ability to detect inverse agonists. [35S]‐GTP‐γ‐S assays were conducted using established methods. We screened 21 MOR “antagonists” using membranes prepared from HERK‐treated hMOR‐CHO cells. All antagonists, including CTAP and 6β‐naltrexol, were inverse agonists. However, LTC‐274 ((−)‐3‐cyclopropylmethyl‐2,3,4,4α,5,6,7,7α‐octahydro‐1H‐benzofuro[3,2‐e]isoquinolin‐9‐ol)) showed the lowest efficacy as an inverse agonist, and, at concentrations less than 5 nM, had minimal effects on basal [35S]‐GTP‐γ‐S binding. Other efforts in this study identified KC‐2‐009 ((+)‐3‐((1R,5S)‐2‐((Z)‐3‐phenylallyl)‐2‐azabicyclo[3.3.1]nonan‐5‐yl)phenol hydrochloride) as an inverse agonist at untreated MOR cells. In HERK‐treated cells, KC‐2‐009 had the highest efficacy as an inverse agonist. In summary, we identified a novel and selective MOR inverse agonist (KC‐2‐009) and a novel MOR antagonist (LTC‐274) that shows the least inverse agonist activity among 21 MOR antagonists. LTC‐274 is a promising lead compound for developing a true MOR neutral antagonist. Synapse 64:280–288, 2010.

Novel radical synthesis of morphine fragments spiro[benzofuran-3(2H),4'-piperidine] and octahydro-1H-benzofuro[3,2-e]isoquinoline

Abstract A new strategy for the synthesis of oxide-containing fragments of morphine has been developed. Thus, the tricyclic (ANO) morphine fragment spiro[7-methoxybenzofuran-3(2H),4′-1′-methylpiperidine] (1) was obtained as the sole product via an intramolecular radical cyclization of 4-[(2′-bromo-6′-methoxyphenoxy)methyl]-1-methyl-1,2,5,6,-tetrahydropyridine (9); while the tetracyclic (ACNO) fragment 9-methoxy-3-methyl-2,3,4,4aα,5,6,7,7aα-octahydro-1H-benzofuro[3,2-e]isoquinoline (3) and its 4-oxo analog 4 were synthesized in a similar fashion starting from 5,6,7,8-tetrahydroisoquinoline (10).

The development of a potential single photon emission computed tomography (SPECT) imaging agent for the corticotropin-releasing hormone receptor type 1

A high-affinity radioligand for CRHR1 has been prepared that can serve as a template for the development of SPECT imaging agents. The 5-chloro-N-cyclopropylmethyl-N-(2,6-dichloro-4-iodophenyl)-2-methyl-N-propylpyrimidine-4,6-diamine (6b, Ki = 14 nM), and the corresponding 4-bromophenyl analogue (6a, Ki = 21 nM), were synthesized in four steps from compound 3.

Synthesis and dopamine transporter affinity of chiral 1-[2-[bis(4-fluorophenyl)methoxy]ethyl]-4-(2-hydroxypropyl)piperazines as potential cocaine abuse therapeutic agents

A series of optically pure phenyl-and non-phenyl-substituted 1-[2-[bis(4-fluorophenyl)methoxy]ethyl]-4-(2-hydroxypropyl)piperazines was synthesized and their binding affinity for dopamine transporter (DAT) was investigated. The analogues with a hydroxyl group in the S configuration were more selective for the DAT over the serotonin transporter (SERT) than the corresponding R enantiomers. Compound (+)-11 showed high affinity and selectivity for DAT over the SERT and, therefore, is a potential candidate for the development of a long-acting cocaine abuse therapeutic agent.

Synthesis of [3H](4-fluorobutyl)propyl[2,5,6-trimethyl-7-(2,4,6-trimethylphenyl)pyrrolo[2,3-d]pyrimidin-4-yl]amine: a potent radioligand for corticotropin-releasing hormone type 1 receptor

[3H](4-Fluorobutyl)propyl[2,5,6-trimethyl-7-(2,4,6-trimethylphenyl)pyrrolo[2,3-d]pyrimidin-4-yl]amine ([3H]LWH-154), a novel potent radiolabelled analog of the nonpeptide corticotropin-releasing hormone type 1 receptor (CRHR1) selective antagonist, butylethyl[2,5,6-trimethyl-7-(2,4,6-trimethylphenyl)pyrrolo[2,3-d]pyrimidin-4-yl]amine (antalarmin), was prepared for the development of positron emission tomography radiotracers for CRHR1 and evaluation as a nonpeptide radioligand for use in pharmacological studies. The precursor (4-fluorobutyl)prop-2-enyl[2,5,6-trimethyl-7-(2,4,6-trimethylphenyl)pyrrolo[2,3-d]pyrimidin-4-yl]amine (6) for tritiation was prepared in two steps from 3 in 76% total yield. Catalytic reduction of unsaturated fluoride 6 using tritium gas and palladium as catalyst gave [3H]LWH-154. After HPLC purification, [3H]LWH-154 of high radiochemical purity was obtained with a specific activity of 69 Ci/mmol. Copyright