Concise Total Synthesis of Complanadine A Enabled by Pyrrole-to-Pyridine Molecular Editing

Advancing Total Synthesis Through Skeletal Editing

ConspectusTotal synthesis has long been a proving ground for advancing chemical thought, pushing chemists to develop strategies that not only replicate nature's complexity but often surpass it. The pursuit of efficiency, practicality, and elegance continues to challenge and reshape the guiding principles of total synthesis. In recent years, skeletal editing has emerged as a powerful strategy for reconfiguring skeletal frameworks in ways that were previously difficult to imagine. Unlike conventional chemical synthesis approaches, which primarily rely on the logic of bond construction reactions and functional group manipulations, skeletal editing introduces elements that allow for atom insertion, deletion, and exchange and skeletal rearrangement/reorganization by harnessing the potential energy and reactivity of certain structural motifs and morphing them into new electronic and spatial configurations. The logic of modern skeletal editing has been fueling the development of new editing methods and advancing the fields of total synthesis, medicinal chemistry, materials science, and others.In this Account, we detail our program using skeletal editing-based retrosynthetic logic to facilitate natural product synthesis. We first highlight two one-carbon insertion editing strategies utilizing the Ciamician-Dennstedt rearrangement and the Büchner-Curtius-Schlotterbeck ring expansion to streamline the total syntheses of complanadine and phleghenrine Lycopodium alkaloids. We next present our synthesis of crinipellin and gibberellin diterpenes by leveraging the facile synthesis and intrinsic strain of cyclobutanes as precursors to challenging cyclopentanes via cut-and-insert editing (crinipellins) or C-C bond migratory ring expansion (GA18). Toward the end, we describe our early efforts in orchestrating structural rearrangement and functional group pairing reactions to access seven monoterpene indole alkaloids and highlight the divergent potential of skeletal editing. Each of the five examples follows a build-edit-decorate workflow, inspired by Schreiber's build-couple-pair in diversity-oriented synthesis. In the build stage, key scaffolds are efficiently assembled from starting materials with matched reactivity. The edit stage morphs these scaffolds to the desired but more challenging ones encoded by the target molecules, reminiscent of Corey's application of rearrangement transforms as a topological strategy. The decorate stage introduces additional functional groups and adjusts oxidation states to complete the total synthesis, similar to the oxidase phase of Baran's two-phase synthesis. The essence of skeletal editing-based retrosynthetic analysis is to identify latent structural relationships between the readily assembled key scaffolds constructed in the build stage and the desired ones encoded by the target molecules as well as proper editing methods to transform the former into the latter with precision. The build-edit-decorate approach parallels the dynamism of biosynthesis, enabling rapid building of complexity with great efficiency and step economy, as analyzed by the spacial scores (SPS) of each case. Drawing on these principles, chemists can adopt skeletal editing-based retrosynthetic logic by identifying latent intermediates and employing and developing strategic editing methods to overcome synthetic bottlenecks.

Revolutionizing Playing with Skeleton Atoms: Molecular Editing Surgery in Medicinal Chemistry

Finding the most perfect drug candidates in the fields of drug discovery and medicinal chemistry will remain the main interest of drug designers. This concern necessitates organic and medicinal chemists, in most examples, to precisely design and search for drug candidates that are very analogous to the present effective drugs with solving, mainly, their proven critical pharmacological and clinical issues through slightly changing one or two atoms of the principal functional skeletons of the molecules of these present therapeutics by atom swapping, removal, and/or addition procedures in organic chemical synthesis. This accurate modern chemicosimilarity tactic in drug discovery surely saves time while keeping us very close, or sometimes highly superior, to the parent pharmacophoric bioactivity (i.e., keeping considerable analogy to the parent therapeutic molecule). From this perspective and logic, the science of skeletal editing of molecules (i.e., skeletal molecular editing) arose in the era of artificial intelligence (AI) and its dramatic predictions. As a pioneer in this modern branch in pharmaceutical and therapeutic organic chemistry, in this up-to-date minireview and perspective article, an attempt was made to introduce skeletal editing and its synthetic surgeries (over molecules) to the audience (including irrelevant readers) in a simpler and more attractive way as a novel chemical technology, highlighting the previous synthetic trials (in general), demonstrating the three main techniques, and, finally, discussing the future therapeutic needs and scenarios from a medicinal chemist's viewpoint.

Convergent and Efficient Total Synthesis of (+)-Heilonine Enabled by C-H Functionalizations

We report a convergent and efficient total synthesis of the C-nor D-homo steroidal alkaloid (+)-heilonine with a hexacyclic ring system, nine stereocenters, and a trans-hydrindane moiety. Our synthesis features four selective C-H functionalizations to form key C-C bonds and stereocenters, a Stille carbonylative cross-coupling to connect the AB ring system with the DEF ring system, and a Nazarov cyclization to construct the five-membered C ring. These enabling transformations significantly reduced functional group manipulations and delivered (+)-heilonine in 11 or 13 longest linear sequence (LLS) steps.