β-(1→3,1→6)-d-glucans produced by Diaporthe sp. endophytes: Purification, chemical characterization and antiproliferative activity against MCF-7 and HepG2-C3A cells.

This study reports the characterization and antiproliferative activity of exopolysaccharides (EPS) produced by submerged cultures of the endophytes Diaporthe sp. JF766998 and Diaporthe sp. JF767007 isolated from the medicinal plant Piper hispidum Sw.

Olefin metathesis-iodoetherification-dehydroiodination strategy for spiroketal subunits of polyether antibiotics.

The convergent synthesis of two pentacyclic analogues of the polyether monensin A is described. Although different with respect to the configuration of the alcohol at the 3 position of the six-membered ring of the spiroketal subunit, the configuration at the acetal center in both structures is unchanged and is consistent with the anomeric effect. The key synthetic steps are the coupling of two complex segments via an olefin metathesis, and the subsequent conversion of a dihydroxyalkene to the spiroketal through an iodoetherification-dehydroiodination sequence.