Enantioselective Synthesis of (+)-Penostatin E

Asymmetric synthesis of penostatins A-D from L-ascorbic acid

The first asymmetric synthesis of (-)-penostatins B and D and the practical synthesis of (+)-penostatins A and C have been accomplished through a flexible strategy. The features of the synthesis are a BF3·OEt2-mediated Diels-Alder reaction of chiral dienophiles and methylcyclopentadienes with high chemo-, regio-, and stereoselectivity, followed by ozonolysis to install the common trisubstituted cyclopentane intermediate, and a hetero-Diels-Alder reaction with easily tunable facial selectivity, followed by sulfonate elimination to construct both enantiomeric tricyclic systems for penostatins A/C and B/D, respectively.

Enantioselective Total Synthesis of (+)-Penostatins A and C

A stereoselective and column-economic approach to (+)-penostatins A and C has been developed. The multisubstituted A ring and B/C rings in their unique tricyclic framework are constructed through a Diels-Alder reaction/ozonolysis sequence and an exo intramolecular hetero-Diels-Alder reaction with high chemo-, regio-, and stereoselectivity. Using this route, (+)-penostatins A and C can be synthesized in 19 and 20 steps, respectively, with a good overall yield involving only five or six column chromatographic purifications.

Enantioselective anti- and syn-(Borylmethyl)allylation of Aldehydes via Brønsted Acid Catalysis

The enantioselective anti- and syn-(borylmethyl)allylation of aldehydes via phosphoric acid catalysis is reported. Both (E)- and (Z)-γ-borylmethyl allylboronate reagents were prepared via the Cu-catalyzed highly stereoselective protoboration of 1,3-dienylboronate. Chiral phosphoric acid-catalyzed aldehyde allylation with either the (E)- or (Z)-allylboron reagent provided 1,2-anti- or 1,2-syn-adducts in good yields with high enantioselectivities. The application to the synthesis of morinol D was accomplished.

Asymmetric Total Syntheses of (+)-Penostatins A and C

Penostatins A and C are cytotoxic natural products that show promising selective inhibitory activity against PTP1B. Here the first asymmetric total syntheses of (+)-penostatins A and C are reported. Our strategy features (i) a new method for the synthesis of 6-alkyl-3-hydroxy-2-pyrones, (ii) a cascade involving the intramolecular Diels-Alder reaction of 2-pyrone and a retro-hetero-Diels-Alder (decarboxylation) reaction, (iii) Ando-Horner-Wadsworth-Emmons olefination/lactonization, and (iv) selenoxide elimination. Our study confirmed the absolute configurations of penostatins A and C and laid the groundwork for further bioactivity studies.

Marine natural products

This review covers the literature published in 2014 for marine natural products (MNPs), with 1116 citations (753 for the period January to December 2014) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1378 in 456 papers for 2014), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

A Ce(OTf)3/PyBox catalyzed enantioselective Hosomi–Sakurai reaction of aldehydes with allyltrimethylsilane

An approach to the efficient synthesis of enantioselective homoallylic alcohols has been developed by the use of a catalytic amount of a cerium/PyBox complex.