The Three Pillars of Natural Product Dereplication. Alkaloids from the Bulbs of Urceolina peruviana (C. Presl) J.F. Macbr. as a Preliminary Test Case.

The role and importance of the identification of natural products are discussed in the perspective of the study of secondary metabolites. The rapid identification of already reported compounds, or structural dereplication, is recognized as a key element in natural product chemistry. The biological taxonomy of metabolite producing organisms, the knowledge of metabolite molecular structures, and the availability of metabolite spectroscopic signatures are considered as the three pillars of structural dereplication. The role and the construction of databases is illustrated by references to the KNApSAcK, UNPD, CSEARCH, and COCONUT databases, and by the importance of calculated taxonomic and spectroscopic data as substitutes for missing or lost original ones. Two NMR-based tools, the PNMRNP database that derives from UNPD, and KnapsackSearch, a database generator that provides taxonomically focused libraries of compounds, are proposed to the community of natural product chemists. The study of the alkaloids from Urceolina peruviana, a plant from the Andes used in traditional medicine for antibacterial and anticancer actions, has given the opportunity to test different approaches to dereplication, favoring the use of publicly available data sources.

Convergent Evolution of Diastereomeric Mixtures of 5-Methoxy-pentylzirconocenes toward Trans-1,2-substituted Cyclopentanes.

The access to 1,2- and 1,1,2-substituted trans cyclopentanes via a sequential hydrozirconation/TMSOTf-mediated cyclization applied to 5-methoxypent-1-enes is presented. Involving a transient carbocation, the reaction was shown to be diastereo-convergent. Possibly performed in a nonracemic version, the reaction proved compatible with a range of functional groups affording a large panel of cyclopentanes.

Homoallylic amines as efficient chiral inducing frameworks in the conjugate addition of amides to α,ß-unsaturated esters. An entry to enantio-enriched diversely substituted amines.

The diastereoselective conjugate addition of secondary homoallylamines, obtained in the enantioenriched form via allylmetallation of imines, to α,ß-unsaturated esters is reported. This method allows access to valuable building blocks as well as heterocyclic skeletons, providing tertiary amines bearing two chains integrating a stereogenic center adjacent to the nitrogen atom.