Synthesis and Absolute Configurations of Six Natural Phenylpropanoids

Design, synthesis and evaluation of bioactivity of peptidomimetics based on chloroalkene dipeptide isosteres

Ample biologically active peptides have been found, identified and modified for use in drug discovery to date. However, several factors, such as low metabolic stability due to proteolysis and non-specific interactions with multiple off-target molecules, might limit the therapeutic use of peptides. To enhance the stability and/or bioactivity of peptides, the development of "peptidomimetics," which mimick peptide molecules, is considered to be idealistic. Hence, chloroalkene dipeptide isosteres (CADIs) was designed, and their synthetic methods have been developed by us. Briefly, in a CADI an amide bond in peptides is replaced with a chloroalkene structure. CADIs might be superior mimetics of amide bonds because the Van der Waals radii (VDR) and the electronegativity value of a chlorine atom are close to those of the replaced oxygen atom. By a developed method of the "liner synthesis", N-tert-butylsulfonyl protected CADIs can be synthesized via a key reaction involving diastereoselective allylic alkylation using organocopper reagents. On the other hand, by a developed method of the "convergent synthesis", N-fluorenylmethoxycarbonyl (Fmoc)-protected carboxylic acids can be also constructed based on N- and C-terminal analogues from corresponding amino acid starting materials via an Evans syn aldol reaction and the Ichikawa allylcyanate rearrangement reaction involving a [3.3] sigmatropic rearrangement. Notably, CADIs can also be applied for Fmoc-based solid-phase peptide synthesis and therefore introduced into bioactive peptides including as the Arg-Gly-Asp (RGD) peptide and the amyloid β fragment Lys-Leu-Val-Phe-Phe (KLVFF) peptide, which are correlated with cell attachment and Alzheimer's disease (AD), respectively. These CADI-containing peptidomimetics stabilized the conformation and enhanced the potency of the cyclic RGD peptide and the cyclic KLVFF peptide.

Isolation and structure characterization of cytotoxic alkaloids from Micromelum integerrimum

Ten undescribed alkaloids, named integerrines A-J, including one racemic heterodimer of carbazole and indole, two racemic, two scalemic, and one enantiomerically enriched biscarbazoles, two aldoximes, and one racemic pyrrolone, were isolated from the dried leaves and stems of Micromelum integerrimum. The racemic or scalemic compounds were resolved using chiral-phase HPLC and their configurations were determined by comparison of experimental and calculated ECD data. Four compounds exhibited moderate to weak cytotoxicities against HepG2, HTC-116, HeLa, and PANC-1 cell lines, with IC₅₀ values of 14.1-67.5 μM.

Phenylpropanoids from Juglans mandshurica exhibit cytotoxicities on liver cancer cell lines through apoptosis induction

Three new phenylpropanoids (1-3) together with six known congeners (4-9) were isolated from the bark of Juglans mandshurica Maxim using anti-hepatoma activity as a guide. Their structures were determined by comprehensive NMR and HRESIMS spectroscopic data analyses. All the isolated compounds were evaluated for their growth inhibitory activities against two kinds of liver cancer cell lines (HepG2 and Hep3B). Among them, compound 4 showed moderate cytotoxic activities against HepG2 and Hep3B cell lines with IC₅₀ values of 58.58 and 69.87μM. Compound 5 exhibited 50% cell death rate in HepG2 and Hep3B cell lines at 63.70 and 46.45μM, respectively. Further observation of morphological changes and Western blot demonstrated that compounds 4 and 5 exhibited their cytotoxic activities through the induction of apoptosis. A structure-activity relationship study suggested that an α, β-unsaturated aldehyde might be the most important functional group.

Applications of oxazolidinones as chiral auxiliaries in the asymmetric alkylation reaction applied to total synthesis

In this review, a number of applications of chiral oxazolidinones in the asymmetric alkylation reaction applied to total synthesis are described.