Total Synthesis of (+)-epi-Condyfoline

Controllable skeletal reorganizations in natural product synthesis

Covering: 2016 to 2023The synthetic chemistry community is always in pursuit of efficient routes to natural products. Among the many available general strategies, skeletal reorganization, which involves the formation, cleavage, and migration of C-C and C-heteroatom bonds, stands out as a particularly useful approach for the efficient assembly of molecular skeletons. In addition, it allows for late-stage modification of natural products for quick access to other family members or unnatural derivatives. This review summarizes efficient syntheses of steroid, terpenoid, and alkaloid natural products that have been achieved by means of this strategy in the past eight years. Our goal is to illustrate the strategy's potency and reveal the spectacular human ingenuity demonstrated in its use and development.

Asymmetric Total Synthesis of (+)-Epiibogamine Enabled by Three-Component Domino Michael/Michael/Mannich Annulation of N-Sulfinyl Metallosilylenamines

The iboga alkaloids are promising antiaddictive and neuroregeneration candidates for medical treatment. There is a lack of studies for C20-epi iboga alkaloids due to the synthetic difficulties. Herein we report the shortest total synthesis of (+)-epiibogamine in seven steps from trimethyl orthobutyrate. The novel N-sulfinyl silylenamine reagent enabled the key step, with three-component domino Michael/Michael/Mannich annulation providing the 1-amino-2,4-diester scaffold with four new chiral centers, and access to the isoquinuclidine in high yield (84%) and diastereoselectivity (>95:5 dr).

N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

The synthesis of nitrogen-containing heterocycles, including natural alkaloids and other compounds presenting different types of biological activities have proved to be successful employing chiral sulfinyl imines derived from tert-butanesulfinamide. These imines are versatile chiral auxiliaries and have been extensively used as eletrophiles in a wide range of reactions. The electron-withdrawing sulfinyl group facilitates the nucleophilic addition of organometallic compounds to the iminic carbon with high diastereoisomeric excess and the free amines obtained after an easy removal of the tert-butanesulfinyl group can be transformed into enantioenriched nitrogen-containing heterocycles. The goal of this review is to the highlight enantioselective syntheses of heterocycles involving the use of chiral N-tert-butanesulfinyl imines as reaction intermediates, including the synthesis of several natural products. The synthesis of nitrogen-containing heterocycles in which the nitrogen atom is not provided by the chiral imine will not be considered in this review. The sections are organized according to the size of the heterocycles. The present work will comprehensively cover the most pertinent contributions to this research area from 2012 to 2020. We regret in advance that some contributions are excluded in order to maintain a concise format.

Natural Product Synthesis Enabled by Domino Processes Incorporating a 1,2-Rearrangement Step

The art of natural product total synthesis is closely associated with two major determinants: the development/application of novel chemical reactions and the innovation in strategic use of classic organic reactions. While purposely seeking/applying a new synthetic methodology allowing nonconventional bond disconnections could shorten the synthetic route, the development of domino processes composed of a series of well-established reactions could also lead to a concise, practical, and aesthetically appealing synthesis. As an important class of textbook reactions, the 1,2-anionotropic rearrangements discovered at the dawn of modern organic chemistry have important bearings not only on chemical synthesis but also on the conceptual breakthroughs in the field. In its basic form, the 1,2-shift affords nothing but a constitutional isomer of the starting material and is therefore not a complexity-generating transformation. However, such a simple 1,2-shift could in fact change the molecular topology if the precursor is cleverly designed. More dramatically, it can metamorphosize the structure of the substrate when it is combined with other transformations in a domino sequence. In this Outlook, we highlight recent examples of natural product synthesis featuring a key domino process incorporating a 1,2-anionotropic rearrangement. Specifically, domino reactions integrating Wagner-Meerwein, pinacol, α-ketol, α-aminoketone, α-iminol, or benzilic acid rearrangements will be discussed.

Applications of tert-butanesulfinamide in the synthesis of N-heterocycles via sulfinimines

Chiral sulfinamides are among the best known chiral auxiliaries in the stereoselective synthesis of amines and their derivatives. The most extensively used enantiopure tert-butanesulfinamide emerged as the gold standard among many others over the last two decades. The present review attempts to provide an overview of tert-butanesulfinamide mediated asymmetric N-heterocycle synthesis via sulfinimines and covers literature from 2010-2020. This methodology offers general access to structurally diverse piperidines, pyrrolidines, azetidines, and their fused derivatives that represent the structural motif of many natural products and therapeutically applicable compounds.