Total Synthesis of Strasseriolide A

Exploring the Synthetic Potential of Horner-Wadsworth-Emmons Reaction Toward the Synthesis of Polyketide Based Natural Products: A Review

The Horner-Wadsworth-Emmons (HWE) reaction is a commonly used and reliable phenomenon for carbon-carbon olefination in organic chemistry, carried out by treating aldehyde or ketones with phosphonate esters to afford the substituted alkenes. HWE reaction has also been observed to be involved in the stereo-controlled syntheses of naturally occurring compounds that acquire pharmaceutical profiles against various diseases. In this article, recent implementations of Horner-Wadsworth-Emmons reaction towards the notable total syntheses of naturally occurring compounds such as polyketides have been summarized.

Yamaguchi esterification: a key step toward the synthesis of natural products and their analogs-a review

The Yamaguchi reagent, based on 2,4,6-trichlorobenzoyl chloride (TCBC) and 4-dimethylaminopyridine (DMAP), is an efficient tool for conducting the intermolecular (esterification) reaction between an acid and an alcohol in the presence of a suitable base (Et3N or i Pr2NEt) and solvent (THF, DCM, or toluene). The Yamaguchi protocol is renowned for its ability to efficiently produce a diverse array of functionalized esters, promoting high yields, regioselectivity, and easy handling under mild conditions with short reaction times. Here, the recent utilization of the Yamaguchi reagent was reviewed in the synthesis of various natural products such as macrolides, terpenoids, polyketides, peptides, and metabolites.

Total Syntheses of Strasseriolide A and Strasseriolide B, Potent Antimalarial Agents

We describe the convergent total syntheses of strasseriolides A and B, which are potent antimalarial agents recently isolated from an unnamed plant found in a remote region of New Zealand. Both natural products exhibited potent activity against malaria parasite, Plasmodium falciparum. The synthesis involved asymmetric syn-aldol, asymmetric alkylation, and asymmetric Johnson-Claisen rearrangement to set six of the seven chiral centers of strasseriolide B. The synthesis also highlights the formation of an 18-membered macrolactone from a diacid by using a Yamaguchi macrolactonization protocol. Other key transformations involved Grubbs' cross-metathesis, selective 1,4-reduction, hydrostannylation reaction, and NHK coupling reaction. The convergent synthesis of strasseriolide A required 27 total synthetic steps and 16 longest linear steps from known readily available intermediates.

Collective and Diverted Total Synthesis of the Strasseriolides: A Family of Macrolides Endowed with Potent Antiplasmodial and Antitrypanosomal Activity

The strasseriolide macrolides show promising in vitro and in vivo activities against P. falciparum and T. cruzi, the parasites causing malaria and Chagas disease, respectively. However, the as yet poor understanding of structure/activity relationships and the fact that one family member proved systemically toxic for unknown reasons render a more detailed assessment of these potential lead compounds difficult. To help overcome these issues, a collective total synthesis was devised. The key steps consisted of a ring closing alkyne metathesis (RCAM) reaction to forge a common macrocyclic intermediate followed by a hydroxy-directed ruthenium catalyzed trans-hydrostannation of the propargyl alcohol site thus formed. The resulting alkenyltin derivative served as the central node of the synthesis blueprint, which could be elaborated into the natural products themselves as well as into a set of non-natural analogues according to the concept of diverted total synthesis. The recorded biological data confirmed the potency of the compounds and showed the lack of any noticeable cytotoxicity. The "northern" allylic alcohol subunit was recognized as an integral part of the pharmacophore, yet it provides opportunities for chemical modification.

Asymmetric total synthesis of humulane sesquiterpenoids alashanoids B, C, E, and F and 2,9-humuladien-6-ol-8-one

Naturally occurring sesquiterpenes having humulane frameworks are structurally intriguing and possess significant biological profiles. Asymmetric synthesis of the alashanoids B, C, E, and F and 2,9-humuladien-6-ol-8-one is achieved for the first time through a linear synthetic strategy. Intramolecular late-stage Nozaki-Hiyama-Kishi (NHK) coupling is employed to access the eleven-membered macrocyclic core present in the target molecules. The NHK precursors are accessed using the Evans and non-Evans syn and anti-aldol reaction as a key transformation. X-ray and ECD analysis reconfirmed the synthesized compounds' structures and chirotopical properties.

Total Synthesis of Antibacterial Macrolide Sorangiolide A

A convergent route for the asymmetric total synthesis of antibacterial macrolide sorangiolide A has been developed for the first time. The key feature of this synthesis includes Krische iridium-catalyzed anti-diastereoselective carbonyl crotylation, Crimmins acetate aldol, Yamaguchi esterification, Julia-Kocienski olefination, Horner-Wadsworth-Emmons olefination, and ring-closing metathesis. The origin of the low intensity of the 13C{1H} NMR signals of the C1 and C2 centers of the natural product has been investigated, disclosing possible forms of existence for the natural product in the solution phase.