Synthesis of plaunotol derivatives and their antibacterial activities against Helicobacter pylori

Insights into the Design of Inhibitors of the Urease Enzyme - A Major Target for the Treatment of Helicobacter pylori Infections

Expressed by a variety of plants, fungi and bacteria, the urease enzyme is directly associated with the virulence factor of many bacteria, including Helicobacter pylori, a gram-negative bacterium related to several gastrointestinal diseases and responsible for one of the most frequent bacterial infections throughout the world. The Helicobacter pylori Urease (HPU) is a nickel-dependent metalloenzyme expressed in response to the environmental stress caused by the acidic pH of the stomach. The enzyme promotes the increase of gastric pH through acid neutralization by the products of urea hydrolysis, then critically contributing to the colonization and pathogenesis of the microorganism. At the same time, standard treatments for Helicobacter pylori infections have limitations such as the increasing bacterial resistance to the antibiotics used in the clinical practice. As a strategy for the development of novel treatments, urease inhibitors have proved to be promising, with a wide range of chemical compounds, including natural, synthetic and semisynthetic products to be researched and potentially developed as new drugs. In this context, this review highlights the advances in the field of HPU inhibition, presenting and discussing the basis for the research of new molecules aiming at the identification of more efficient therapeutic entities.

Farnesyl diphosphate analogues with omega-bioorthogonal azide and alkyne functional groups for protein farnesyl transferase-catalyzed ligation reactions

Eleven farnesyl diphosphate analogues, which contained omega-azide or alkyne substituents suitable for bioorthogonal Staudinger and Huisgen [3 + 2] cycloaddition coupling reactions, were synthesized. The analogues were evaluated as substrates for the alkylation of peptide cosubstrates by yeast protein farnesyl transferase. Five of the diphosphates were good alternative substrates for farnesyl diphosphate (FPP). Steady-state kinetic constants were measured for the active compounds, and the products were characterized by HPLC and LC-MS. Two of the analogues gave steady-state kinetic parameters (kcat and Km) very similar to those of the natural substrate.

Solid-phase selenium-catalyzed selective allylic chlorination of polyprenoids: facile syntheses of biologically active terpenoids

Regioselective halogenation of the terminal isopropylidene unit of different acyclic polyolefinic polyprenoids (farnesyl acetate, geranylgeranyl acetate, squalene, etc.) using NCS/catalytic polymer-supported selenenyl bromide is described; good to excellent yields are obtained (68-96%). The first applications of this protocol include the concise synthesis of bioactive terpenoids 1-3.

An Effective and Highly Stereoselective Julia Olefination of Cyclopropyl Carbinol Mediated by CeCl3·7H2O/NaI

[reaction: see text] An efficient and highly stereoselective synthesis of functionalized trisubstituted E-olefins from cyclopropyl carbinol derivatives via a Julia-type olefination mediated by an intriguing Lewis acidic system consisting of CeCl(3).7H(2)O and NaI in refluxing acetonitrile is reported. This facile olefination allows for the iterative incorporation of methylcyclopropyl ketone as a C(5) prenylation synthon in the synthesis of acyclic terpenoids, as demonstrated in the facile synthesis of plaunotol 6E-isomer 12, a biologically significant diterpene diol, and naturally occurring diterpene 17.