Total Synthesis of the Oxopolyene Macrolide (−)-Marinisporolide C

Synthesis of Polyene Bioactive Natural Products: FR252921 and Vitamin A

A formal synthesis of FR252921, a potent macrocyclic immunosuppressive agent, and a six-step synthesis of vitamin A have been demonstrated. The application of a ruthenium-catalyzed step-economic and environmentally benign strategy for the highly stereo- and chemoselective construction of valuable polyene motifs of FR252921 and vitamin A highlights the syntheses. The key features for the synthesis FR252921 include preparation of the triene moiety followed by two consecutive peptide couplings of the three fragments.

Inspirations from tetrafibricin and related polyketides: new methods and strategies for 1,5-polyol synthesis

Covering: up to 2019 Selective synthesis with control of remote stereogenic centers has long been a challenge in organic chemistry. In recent years the interest in this topic has been energized by isolation and synthetic studies of tetrafibricin and other natural products containing 1,5-polyols, such as amphidinol 3, marinomycins, and caylobolide. Here we discuss recent developments in 1,5-polyol synthesis, including an overview of selected bioactive natural products in this class and examples of new synthetic methodologies and strategies dedicated to remote stereocontrol in these structures. To illustrate in greater depth, we review several instructive examples of how these innovations have been applied in synthetic studies on tetrafibricin.

Unified Strategy for 1,5,9- and 1,5,7-Triols via Configuration-Encoded 1,5-Polyol Synthesis: Preparation and Coupling of C15-C25 and C26-C40 Fragments of Tetrafibricin

Diverse classes of natural products contain chiral 1,5,9- and 1,5,7-triol stereotriads, including the novel fibrinogen receptor antagonist tetrafibricin. Biological activities associated with compounds containing these motifs warrant targeted synthetic strategies to 1,5-polyol families from cheap and easily accessible reagents while avoiding the need to determine configurations at each alcohol stereocenter. In the accompanying paper, we present a solution to these problems via an iterative configuration-encoded strategy that exploits Julia-Kocienski couplings of enantiopure α-silyloxy-γ-sulfononitrile building blocks. The stereocontrol is unambiguous, and the building blocks are available in multigram quantities via asymmetric catalysis. This approach efficiently accessed a C26-C40 subunit of tetrafibricin that contains a syn, syn-1,5,9-triol and all of the stereochemistry and functionality needed to advance toward tetrafibricin. A modification afforded the anti, syn-1,5,7-triol within the C15-C25 fragment of tetrafibricin by merging 1,5-polyol synthesis with diastereoselective intramolecular conjugate addition. The union of the C15-C25 and C26-C40 fragments was achieved via a BF₃·OEt₂-mediated Mukaiyama aldol construction with high 1,3- anti stereoinduction, revealing some unexpected insights on the impact of silyl protecting groups on 1,3- anti diastereocontrol by a β-siloxyaldehyde aldol acceptor. Directed 1,3- anti reduction completed the stereostructure of the C15-C40 portion of tetrafibricin, with configurations established by a combination of NMR experiments.

Regioselective and Stereoselective Heck-Matsuda Arylations of Trisubstituted Allylic Alkenols and Their Silyl and Methyl Ether Derivatives To Access Two Contiguous Stereogenic Centers: Expanding the Redox-Relay Process and Application in the Total Synthesis of meso-Hexestrol

Novel palladium-catalyzed redox-relay Heck arylation reactions of trisubstituted allylic alkenols were developed employing silyl and methyl ethers. The reactions proceeded under mild conditions in moderate to high yields in an excellent anti diastereoselectivity to form α,β-disubstituted methyl ketones containing two contiguous stereocenters. The new redox-relay arylations using silyl and methyl ethers of the starting alkenols demonstrate that the presence of a free hydroxyl group is not a sine qua non condition for an effective redox-relay process as previously thought. Deuterium-labeled alkenols 2-d-10a, 2-d-10b, and 2-d-10c permitted tracking the palladium-hydride reinsertion steps in the conversion of the starting free alcohols, silyl, and methyl ethers into the corresponding methyl ketone 3-d-11a, with >98% deuterium retention. Moreover, the synthetic potential of the method was demonstrated with a straightforward synthesis of the meso-hexestrol in 4 steps, in 41% overall yield from alkenol 10a.

Studies toward the synthesis of strevertenes A and G: stereoselective construction of C1–C19segments of the molecules

Efficient route for the stereoselective synthesis of common C₁–C₁₉segment of strevertenes A and G has been developed.

Marine natural products

Covering: 2015. Previous review: Nat. Prod. Rep., 2016, 33, 382-431This review covers the literature published in 2015 for marine natural products (MNPs), with 1220 citations (792 for the period January to December 2015) 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 (1340 in 429 papers for 2015), 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.

Elaboration of Sterically Hindered δ-Lactones through Ring-Closing Metathesis: Application to the Synthesis of the C1-C27 Fragment of Hemicalide

The synthesis of the C1-C27 fragment of hemicalide, a marine metabolite displaying a unique potent antiproliferative activity, has been accomplished. The synthetic approach highlights a remarkably efficient ring-closing metathesis reaction catalyzed by Nolan ruthenium indenylidene complexes to elaborate the highly substituted δ-lactone framework.