A new function of isonitrile as an inhibitor of the Pdr5p multidrug ABC transporter in Saccharomyces cerevisiae.

Pdr5p in Saccharomyces cerevisiae is a functional homologue of mammalian P-glycoprotein implicated in multidrug resistance (MDR). In order to obtain useful inhibitors to overcome MDR in clinical tumors, screening of Pdr5p inhibitors has been carried out. We isolated a fungal strain producing Pdr5p inhibitors using our original assay system, and it was classified as Trichoderma sp.

Boron-mediated aldol reaction of carboxylic esters.

This Account outlines the unique features of the boron-mediated aldol reaction of carboxylic esters, which include (i) facile isomerization of E-enolate to Z-enolate and (ii) formation of a doubly borylated enolate upon enolization of acetate esters. The first carbon-bound boron enolates were spectroscopically characterized, and they appeared to be responsible for these unique properties. Furthermore, complementary anti- and syn-selective boron-mediated asymmetric aldol reactions of chiral propionate esters have been developed.

Mechanism of the double aldol reaction: the first spectroscopic characterization of a carbon-bound boron enolate derived from carboxylic esters.

The novel doubly borylated enolate is identified as an intermediate of the double aldol reaction of acetate esters. As a precursor to the formation of the doubly borylated enolate, carbon-bound boron enolates of carboxylic esters are spectroscopically characterized for the first time. When 2,6-diisopropylphenyl acetate (10d) is treated with c-Hex(2)BOTf (1.

Boron-mediated aldol reaction of carboxylic esters: complementary anti- and syn-selective asymmetric aldol reactions.

The boron-mediated aldol reaction of carboxylic esters is described in detail. Contrary to the general belief that carboxylic esters are inert under the condition of the boron enolate formation, propionate esters are enolized with certain combinations of a boron triflate and an amine. More importantly, the stereochemical course of the aldol reaction can be controlled by the judicious selection of the enolization reagents.