LC-HRMS-Database Screening Metrics for Rapid Prioritization of Samples to Accelerate the Discovery of Structurally New Natural Products.

In order to accelerate the isolation and characterization of structurally new or novel secondary metabolites, it is crucial to develop efficient strategies that prioritize samples with greatest promise early in the workflow so that resources can be utilized in a more efficient and cost-effective manner. We have developed a metrics-based prioritization approach using exact LC-HRMS, which uses data for 24 618 marine natural products held in the PharmaSea database. Each sample was evaluated and allocated a metric score by a software algorithm based on the ratio of new masses over the total (sample novelty), ratio of known masses over the total (chemical novelty), number of peaks above a defined peak area threshold (sample complexity), and peak area (sample diversity). Samples were then ranked and prioritized based on these metric scores. To validate the approach, eight marine sponges and six tunicate samples collected from the Fiji Islands were analyzed, metric scores calculated, and samples targeted for isolation and characterization of new compounds. Structures of new compounds were elucidated by spectroscopic techniques, including 1D and 2D NMR, MS, and MS/MS. Structures were confirmed by computer-assisted structure elucidation methods (CASE) using the ACD/Structure Elucidator Suite.

Palladium-catalysed synthesis of aryl-alkyl ethers using alkoxysilanes as nucleophiles.

Changing the activator from tetrabutyl ammonium fluoride (TBAF) to sodium hydroxide unexpectedly switches the catalytic pathway of the Hiyama coupling reaction of vinyl trialkoxysilanes with aryl bromides into a Pd catalysed C-O bond forming reaction; if the correct conditions are used, high yields of aryl-alkyl ethers are observed. In addition, coupling between readily available tetraalkoxysilanes and aryl bromides can also be realised with NaOH or TBAF activation. The reactions take place in only 20 minutes if microwave heating is employed.

A convenient catalyst system for microwave accelerated cross-coupling of a range of aryl boronic acids with aryl chlorides.

A convenient microwave accelerated cross-coupling procedure between aryl chlorides with a range of boronic acids has been developed. An explanation for the low reactivity of highly fluorinated boronic acids in Suzuki coupling is provided.