Streamlined Symmetrical Total Synthesis of Disorazole B1 and Design, Synthesis, and Biological Investigation of Disorazole Analogues

Total Syntheses of Plocabulin and Its C2-Analogues

Plocabulin is a structurally unique marine natural product with potent antitumor activity, making it a promising candidate for the development of antibody-drug conjugates (ADCs). However, its extremely low natural abundance has limited further research and therapeutic exploration. In this study, we present a convergent synthetic strategy for plocabulin and its C2-analogues. Our approach enabled the synthesis of 1.23 g of plocabulin through a longest linear sequence of 12 steps and a total of 24 steps, achieving an overall yield of 19.7%.

Collective Total Synthesis of Aculeatin A, B, D, E, and F

A collective convergent approach for the enantioselective total synthesis of aculeatins A, B, D, E, and F is presented, featuring [3 + 2]-cycloaddition, iron-mediated reductive N-O bond cleavage, and cascade spirocyclization. Moreover, this short six-step strategy is supplemented in synthesizing unnatural analogs of aculeatins such as 6-epi-aculeatin D, 6-epi-aculeatin E, and 6-epi-aculeatin F.

Iso-Pentadienyl Carbonate as a Five Carbon Synthon in Manganese(I)-Catalyzed Selective Linear 1,3-Dienylation

Selective linear 1,3-dienylations are essential transformations, and numerous synthetic efforts have been documented. However, a general method enabling access to electron-rich, -poor, and biologically relevant dienyl molecules is in high demand. Hence, we report a straightforward method of manganese(I)-catalyzed C-H dienylation of arenes by using iso-pentadienyl carbonate as a five carbon synthon. This is a highly unprecedented report for selective linear 1,3-dienylation using manganese C-H activation catalysis. Our method facilitates the synthesis of varieties of dienes, including those suitable for normal or inverse electron demand Diels-Alder reactions, dienyl glycoconjugates, and unnatural amino acids. Extensive mechanistic studies, including isolation of C-H activated organo-manganese complex and isotopic analyses, have supported the proposed mechanism of this dienylation. The synthetic applicability of this method eased to deliver a 6/6/5-fused tricyclic nagilactone scaffold.

Robust Synthesis of Terpenoid Scaffolds under Mn(I)-Catalysis

The 6/6/5-fused tricyclic scaffold is a central feature of structurally complex terpenoid natural products. A step-economical cascade transformation that leads to a complex molecular skeleton is regarded as a sustainable methodology. Therefore, we report the first Mn(I)-catalyzed C(sp²)-H chemoselective in situ dienylation and diastereoselective intramolecular Diels-Alder reaction using iso-pentadienyl carbonate to access 6/6/5-fused tricyclic scaffolds. To the best of our knowledge, there is no such report thus far to utilize iso-pentadienyl carbonate as a substrate in C-H activation catalysis. Extensive mechanistic studies, such as the isolation of catalytically active organo-manganese(I) complexes, 1,3-dienyl-intermediates, and isotopic labeling experiments have supported the proposed mechanism of this cascade reaction.

Synthesis and Biological Evaluation of C(13)/C(13')-Bis(desmethyl)disorazole Z

We describe the total synthesis of the macrodiolide C(13)/C(13')-bis(desmethyl)disorazole Z through double inter-/intramolecular Stille cross-coupling of a monomeric vinyl stannane/vinyl iodide precursor to form the macrocycle. The key step in the synthesis of this precursor was a stereoselective aldol reaction of a formal Evans acetate aldol product with crotonaldehyde. As demonstrated by X-ray crystallography, the binding mode of C(13)/C(13')-bis(desmethyl)disorazole Z to tubulin is virtually identical with that of the natural product disorazole Z. Likewise, C(13)/C(13')-bis(desmethyl)disorazole Z inhibits tubulin assembly with at least the same potency as disorazole Z and it appears to be a more potent cell growth inhibitor.

Extending the Structure-Activity Relationship of Disorazole C1 : Exchanging the Oxazole Ring by Thiazole and Influence of Chiral Centers within the Disorazole Core on Cytotoxicity

The synthesis of novel disorazole C1 analogues is described and their biological activity as cytotoxic compounds is reported. Based on our convergent entry to the disorazole core we present a flexible and robust strategy to construct a variety of interesting new analogues. In particular, two regions of the molecules were examined for structural modification: 1. Replacement of the heterocyclic moiety by an exchange of the oxazole ring by a thiazole; and 2. Evaluation of the influence of the absolute configuration of the chiral centers of the molecule. Predicated on our flexible strategy we were able to construct all analogues in an efficient way and could perform an exciting SAR (structure-activity-relationship) study to obtain insight in the cytotoxic activity influenced by the chiral centers of the disorazole core.

Total Synthesis of (+)-Neopeltolide by the Macrocyclization/Transannular Pyran Cyclization Strategy

An 11-step synthesis of (+)-neopeltolide was developed. The C1-C7 carboxylic acid and the C8-C16 alcohol were prepared, each in six steps, from (R)- and (S)-epichlorohydrin, respectively. After esterification, our tandem macrocyclization/transannular pyran cyclization strategy was applied to a stereocontrolled construction of the neopeltolide macrolactone. The side chain was synthesized in six steps from ethyl 4-oxazolecarboxylate through palladium-catalyzed cross-couplings. A Mitsunobu reaction of the neopeltolide macrolactone and the side chain completed the synthesis.

Total Synthesis of (-)-Disorazole C1

Disorazoles represent a powerful class of highly potent antitubulin natural products isolated from myxobacteria. Herein, we describe a scalable and robust synthesis of (-)-disorazole C₁ with high stereoselectivity, featuring quite simple reaction conditions that can be used to produce large quantities of this remarkable biologically active compound.