Gyoon-Hee Han

A new strategy for enantiospecific construction of the Securinega alkaloids has been developed and applied in total syntheses of (+)-14,15-dihydronorsecurinine (8), (-)-norsecurinine (6), and phyllanthine (2). The B-ring and C7 absolute stereochemistry of these biologically active alkaloids originated from trans-4-hydroxy-L-proline (10), which was converted to ketonitrile 13 via a high-yielding eight-step sequence. Treatment of this ketonitrile with SmI2 afforded the 6-azabicyclo[3.2.1]octane B/

A convenient nonelectrochemical amide oxidation method has been developed. The process involves a cuprous ion-promoted decomposition of o- diazobenzamides like 4, generated in situ from the corresponding o -aminobenzamides, to give N -acyliminium ion intermediate 9 via a 1,5- H -atom transfer, followed by metal-catalyzed oxidation of the resulting α-amidyl radical. The transformation produces α-methoxybenzamides 15 in good yields. An attempt was made to apply this oxidation method to a total syn

Glycosylation of the hemagglutinin (HA) and neuraminidase (NA) of the influenza provides crucial means for immune evasion and viral fitness in a host population. However, the time-dependent dynamics of each glycosylation sites have not been addressed. We monitored the potential N-linked glycosylation (NLG) sites of over 10,000 HA and NA of H1N1 subtype isolated from human, avian, and swine species over the past century. The results show a shift in glycosylation sites as a hallmark of 1918 and 20

In light of the anti-inflammatory properties of histone deacetylase (HDAC) inhibitors, such as suberoylanilide hydroxamic acid (SAHA) and trichostatin A (TSA), we examined a new HDAC inhibitor KBH-A42 for its anti-inflammatory activities. KBH-A42 showed noteworthy anti-inflammatory properties in vitro via suppression of the production of TNF-alpha, a proinflammatory cytokine, and nitric oxide (NO), a proinflammatory effector molecule, in LPS-stimulated RAW264.7 cells and peritoneal macrophages.

An inexpensive proline derivative and chiral control feature in the total synthesis of securinega alkaloids (-)-norsecurinine (1) and phyllanthine (2). Key steps in the synthesis of 1 include an intramolecular ketonitrile coupling and application of a radical-based generation of N-acylimines. The total synthesis of 2 utilizes a stereoselective imino Diels - Alder construction of the methoxypiperidine ring.

Hydroxamate-based HDAC inhibitors have promising anticancer activities but metabolic instability and poor pharmacokinetics leading to poor in vivo results. QSAR and PK studies of HDAC inhibitors showed that a γ-lactam core and a modified cap group, including halo, alkyl, and alkoxy groups with various carbon chain linkers, improved HDAC inhibition and metabolic stability. The biological properties of the γ-lactam HDAC inhibitors were evaluated; the compound designated 8f had potent anticancer ac

It is well known that the transient and prolonged misfolding nature of amyloid-β (Aβ) makes it difficult to perform proper in vitro studies and obtain consistent results. From monomers to fibrils, the aggregated forms of Aβ are significant hallmarks in the Alzheimer's disease (AD) cascade and become the valuable targets for early diagnosis and therapy for AD. Thus, development of optimized in vitro fibrillogenic conditions to induce the desired Aβ states is essential to AD research. In this stud