A Kiyooka aldol approach for the synthesis of the C(14)-C(23) segment of the diastereomeric analog of tedanolide C

Development of the Synthesis of Desepoxy-Tedanolide C

We are presenting the development of our route for the total synthesis of desepoxy-tedanolide C. Through the obtained analytical data, the proposed structure of tedanolide C is questioned and a different configuration for this natural product is proposed. Key steps of the synthesis are a Kiyooka aldol reaction that builds up the tertiary alcohol flanked by three oxygenated carbon atoms and two aldol reactions used for fragment couplings. A Julia-Kocienski olefination was used for installation of the side chain. Besides the successful synthesis, the development for the protecting group setup of the southwestern hemisphere is described in detail as well as another retrosynthetic attempt for building up the target molecule.

Synthesis of Desepoxy-Tedanolide C

The synthesis of desepoxy‐tedanolide C was accomplished and provided experimental evidence on the configuration of tedanolide C. The reported chemical shifts and coupling constants point to a configuration different from the published structure and analogous to the structures of the other members of this family of natural products. The key step is a Kiyooka aldol protocol for the stereoselective synthesis of the tertiary alcohol flanked by three additional oxygenated carbon atoms. Furthermore, two additional aldol reactions and a Julia–Kocienski olefination were used to assemble the carbon framework.

Stereoselective total synthesis of C2-symmetric natural products pyrenophorol and its derivatives

A stereoselective total synthesis of 16-membered C₂-symmetric macrodiolide Pyrenophorol, Tetrahydropyrenophorol and 4,4-diacetylpyrenophorol have been accomplished. The synthesis started from commercially available L-Aspartic acid and the key reactions involved are regioselective epoxide opening, CBS reduction, Pinnick oxidation and Mitsunobu dilactonization.

Polyoxygenated Tertiary Alcohols: A Kiyooka Approach

A Kiyooka aldol approach for the stereoselective synthesis of tertiary alcohols is presented. This approach allows for the incorporation of different substituents at all three remaining positions at the chiral center bearing the tertiary alcohol. To demonstrate the validity of this approach different chiral alcohols were depicted and the relationship of double bond geometry of the ketene acetal and the diastereoselectivity was established.

Toward the Synthesis of Phormidolides

A convergent and stereoselective approach for the synthesis of marine natural product (MNP) phormidolide D (PM D) is proposed. Two main disconnections divided PM D in three molecular fragments: the macrocyclic core 4, the stapling iodoalkene 9 corresponding to the central part of PMs, and the east fragment 5 that includes the unusual bromo-methoxy-diene moiety and a tetradecanoic acid ended with a (E)-dichloro-ene functionality. Procedures for the preparation of compounds 5, 9, and the never-reported fatty acids 7 and 8, present in PMs C and D, respectively, have been afforded with good yields and high degree of stereoselectivity. The absolute configuration of all of the generated stereocenters has been established. The reaction to link iodoalkene 9 and formylmacrolactone 4, using the Nozaki-Hiyama-Takai-Kishi coupling, gave an advanced synthetic intermediate with total stereocontrol. Finally, a deeper study of protecting groups and reaction conditions for the last step of the synthesis is needed. All the information gathered in this publication will be of great value to continue performing synthetic studies for the preparation of these NPs. The versatility and the presence of a common polyol chain in oscillariolide and PMs A-C would allow applying the same retrosynthesis for the synthesis of the mentioned MNP.

Studies towards the synthesis of tedanolide C. Construction of the C13-epi C1–C15 fragment

An advanced intermediate on route towards tedanolide C has been synthesized using highly stereoselective substrate-controlled titanium-mediated aldol reactions.

The synthesis and biological evaluation of desepoxyisotedanolide and a comparison with desepoxytedanolide

The tedanolides are biologically active polyketides that exhibit a macrolactone constructed from a primary alcohol. Since polyketidal transformations only generate secondary alcohols, it has been hypothesized by Taylor that this unique lactone could arise from a postketidal transesterification. In order to probe this hypothesis and to investigate the biological profile of the putative precursor of all members of the tedanolide family, we embarked on the synthesis of desepoxyisotedanolide and its biological evaluation in comparison to desepoxytedanolide. The biological experiments unraveled a second target for desepoxytedanolide and provided evidence that the proposed transesterification indeed provides a survival advantage for the producing microorganism.

Enantioselective synthesis of the C1-C11 fragment of tedanolide C

A convergent synthesis of the protected C(1)-C(11) fragment 6 of the targeted enantiomer of tedanolide C is described. The key step of the synthesis is the Felkin-Ahn addition of vinyl iodide 7 to aldehyde 8 that proceeds in 80% yield with 4:1 diastereoselectivity.

Stereochemically versatile synthesis of the C1-C12 fragment of tedanolide C

A flexible synthesis of the C1-C12 fragment of Tedanolide C has been accomplished in eight steps from 2-methyl-2,4-pentadienal. Asymmetric hydroformylation of a 1,3-diene allows for the late-stage generation of either C10 epimer with complete catalyst control. Diastereoselective addition of an isobutyryl β-ketoester dianion to an α,β-disubstituted chiral aldehyde sets the C5 stereochemistry while installing the geminal dimethyl unit. Differential protection of a syn-1,3-diol is performed as a highly efficient single-pot operation.