Total synthesis

About: Total synthesis is a research topic. Over the lifetime, 25578 publications have been published within this topic receiving 489319 citations.

Total synthesis of oxidized welwitindolinones and (-)-N-methylwelwitindolinone C isonitrile.

Abstract: We report the total synthesis of (−)-N-methylwelwitindolinone C isonitrile, in addition to the total syntheses of the 3-hydroxylated welwitindolinones. Our routes to these elusive natural products feature the strategic use of a deuterium kinetic isotope effect to improve the efficiency of a late-stage nitrene insertion reaction. We also provide a computational prediction for the stereochemical configuration at C3 of the hydroxylated welwitindolinones, which was confirmed by experimental studies.

Total synthesis of the akuammiline alkaloid (+/-)-vincorine.

Abstract: The first total synthesis of the akuammiline alkaloid (±)-vincorine (6) has been accomplished in about 1% overall yield in 31 steps. A concise assembly of the core 1,2-disubstituted 1,2,3,4-tetrahydro-4a,9a-iminoethanocarbazole (1), a distinctive feature of akuammiline and strychnos alkaloids, was developed via a three-step one-pot cascade reaction consisting of copper-catalyzed intramolecular cyclopropanation, ring-opening, and ring closure. The construction of the last seven-membered E-ring in a rigid two-ring moiety (31, 45 to 47) through Heck coupling, Michael addition, π-allyl/Heck or π-allyl/Stille coupling failed, leading us to seek an alternative method. After successful addition of an acetate side chain on C15 of the cyclohexenyl ring (D-ring) in Boc-protected 35b by a Johnson−Claisen rearrangement and multistep modification of the functionality in the rearrangement product 33a, the E-ring formation was then realized for providing pentacyclic lactam 32 through intramolecular condensation of the a...

Sequential catalytic asymmetric Heck-iminium ion cyclization: enantioselective total synthesis of the Strychnos alkaloid minfiensine.

Abstract: A catalytic asymmetric method for the chemical synthesis of alkaloids containing the 1,2,3,4-tetrahydro-9a,4a-(iminoethano)-9H-carbazole (1) moiety is reported and verified by the enantioselective total synthesis of (+)-minfiensine (4). The central step in this total synthesis is the sequential catalytic asymmetric Heck−N-acyliminium ion cyclization of dienyl carbamate triflate 10, prepared in six steps from 1,2-cyclohexanedione, to give enantiopure 3,4-dihydro-9a,4a-(iminoethano)-9H-carbazole (12) in 75% yield. Iminoethano-9H-carbazole 12 is transformed in six steps to dienyl iodide 17, which undergoes diastereoselective intramolecular Heck cyclization to form pentacyclic intermediate 18. In eight additional steps, this latter intermediate is transformed to (+)-minfiensine (4).

Total Synthesis of the Thiopeptide Promothiocin A

Abstract: The thiopeptide (or thiostrepton) antibiotics are a class of sulfur-containing highly modified cyclic peptides with interesting biological activity. Described herein is the total synthesis of the thiopeptide antibiotic promothiocin A, which utilizes a modified Bohlmann−Rahtz pyridine synthesis to establish the oxazolyl−thiazole−pyridine heterocyclic centerpiece of the antibiotic. The oxazole building blocks were obtained by a dirhodium(II)-catalyzed chemoselective carbenoid N−H insertion reaction followed by cyclodehydration, and the thiazoles by the Hantzsch reaction. Two different strategies for macrocyclization were successfully employed, with the dehydroalanine side chain of the natural product being introduced in the last steps of the synthesis.