Exploring a De Novo Route to Bradyrhizose: Synthesis and Isomeric Equilibrium of Bradyrhizose Diastereomers≠.

A de novo asymmetric strategy for the synthesis of d-bradyrhizose diastereomers from an achiral ketoenolester precursor is described. Key transformations used in the stereodivergent approach include two Noyori asymmetric reductions, an Achmatowicz rearrangement, diastereoselective alkene oxidations, and the first example of a palladium(0)-catalyzed glycosylation of a vinylogous pyranone. The isomeric composition of the bicyclic reducing sugars obtained was analyzed and their behaviour was compared to the natural product, revealing key stereocentres that impact the overall distribution.

Structure-activity relationship of avocadyne.

Avocado consumption is associated with numerous health benefits. Avocadyne is a terminally unsaturated, 17-carbon long acetogenin found almost exclusively in avocados with noted anti-leukemia and anti-viral properties. In this study, specific structural features such as the terminal triple bond, odd number of carbons, and stereochemistry are shown to be critical to its ability to suppress mitochondrial fatty acid oxidation and impart selective activity in vitro and in vivo. Together, this is the first study to conduct a structure-activity analysis on avocadyne and outline the chemical moieties critical to fatty acid oxidation suppression.

De Novo Asymmetric Synthesis of Avocadyne, Avocadene, and Avocadane Stereoisomers.

The de novo asymmetric synthesis of all possible stereoisomers of two polyketide natural products, avocadyne, avocadene, and the saturated variant avocadane, is described. The stereodivergent synthesis of the 12 congeners is accomplished in 4-6 steps from an achiral acylpyruvate derivative, which, in turn, is prepared in five steps from commercially available materials. The approach uses, sequentially, a Noyori asymmetric reduction, a diastereoselective chelate- or directed reduction of a ß-hydroxyketone, and an ester reduction to a primary alcohol.