Synthesis and SAR studies of marine natural products ma’edamines A, B and their analogues
作者:Sanjay Saha、Ch. Venkata Ramana Reddy、Shili Xu、Saranya Sankar、Nouri Neamati、Balaram Patro
DOI:10.1016/j.bmcl.2013.07.017
日期:2013.9
The synthesis of several analogues of ma’edamines A and B are reported. The synthesized compounds were tested on hormone receptor positive and HER2 positive breast cancer cell lines, by MTT assay. MED-114, 115, 117, 119, 120, 124, 128 and 131 were found to be equally active as Lapatinib on HER2 +ve cell line SKBR3.
Combinatorial Synthesis through Disulfide Exchange: Discovery of Potent Psammaplin A Type Antibacterial Agents Active against Methicillin-ResistantStaphylococcus aureus (MRSA)
作者:K. C. Nicolaou、Robert Hughes、Jeffrey A. Pfefferkorn、Sofia Barluenga、A. J. Roecker
Psammaplin A is a symmetrical bromotyrosine -derived disulfide natural product isolated from the Psammaplysilla sponge, which exhibits in vitro antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). Inspired by the structure of this marine natural product, a combinatorial scrambling strategy for the construction of heterodimeric disulfide analogues was developed and applied to the construction of a 3828-membered library starting from 88 homodimeric disulfides. These psammaplin A analogues were screened directly against various gram positive bacterial strains leading to the discovery of a series of potent antibacterial agents active against methicillin-resistant Staphylococcus aureus (MRSA), Among the most active leads derived from these studies are compounds 104. 105, 113, 115, 123, and 128. The present, catalytically-induced. disulfide exchange strategy may be extendable to other types of building blocks bearing thiol groups facilitating the construction of diverse discovery-oriented combinatorial libraries.
<scp>l</scp>-Thyroxin and the Nonclassical Thyroid Hormone TETRAC Are Potent Activators of PPARγ
Thyroid hormones (THs) operate numerous physiological processes through modulation of the nuclear thyroid hormone receptors and several other proteins. We report direct activation of the nuclear peroxisome proliferator-activated receptor gamma (PPAR gamma) and retinoid X receptor (RXR) by classical and nonclassical THs as another molecular activity of THs. The T4 metabolite TETRAC was the most active TH on PPAR gamma with nanomolar potency and binding affinity. We demonstrate that TETRAC promotes PPAR gamma/RXR signaling in cell-free, cellular, and in vivo settings. Simultaneous activation of the heterodimer partners PPAR gamma and RXR resulted in high dimer activation efficacy. Compared to fatty acids as known natural ligands of PPAR gamma and RXR, TETRAC differs markedly in its molecular structure and the PPAR gamma-TETRAC complex revealed a distinctive binding mode of the TH. Our observations suggest a potential connection of TH and PPAR signaling through overlapping ligand recognition and may hold implications for TH and PPAR pharmacology.
Racemization in Suzuki Couplings: A Quantitative Study Using 4-Hydroxyphenylglycine and Tyrosine Derivatives as Probe Molecules
Reaction conditions considered to be typical in Suzuki couplings can cause significant (up to 34% of the unwanted enantiomer) loss of optical purity in sensitive substrates such as hydroxyphenylglycine 1. This may be remedied using sodium succinate instead of sodium carbonate as base, but chemical yields are somewhat lower. Optically pure biaryl amino acids related to those found in the chloropeptins and vancomycin were synthesized by Suzuki coupling of 1 with indolylboronic acids 6-8 and with cyclic boronic acid 9.
Improved Synthesis of L,L-Cycloisodityrosine Subunit of Antitumor Agents Deoxybouvardin and RA-VII
作者:Samir Ghosh、A. Sanjeev Kumar、G. N. Mehta、R. Soundararajan
DOI:10.1080/00397910903245166
日期:2010.7.27
A facile synthesis of the core cycloisodityrosine 14-membered ring system is detailed from commercially available L-tyrosine through a novel synthetic approach to aryl boronic acid 12 via intramolecular cyclization.