The first total synthesis of (-)-fructigenine A and a novel approach to (-)-5-N-acetylardeemin through a common imine intermediate (+)-3 are described. The key steps include highly enantioselective preparation of (+)-3 via domino olefination/isomerization/Claisen rearrangement (OIC) of 5, reductive cyclization (RC), and regioselective oxidation of (-)-4 and a novel assembly of the pyrazino ring of these alkaloids via Ugi three-component reaction/cyclization of (+)-3 with the corresponding amino acid and isonitrile.
Hexahydropyrrolo[2,3-b]indoles 6 were synthesized in five steps from indolin-3-one 8 by a general and efficient method, in which elements of molecular diversity were readily added onto the 3a-position of the pyrrolo[2,3-b]indole ring system. Horner-Wadsworth-Emmons reaction of 2-allyloxyindolin-3-ones 7, derived from indolin-3-one 8 and a variety of allylic alcohols, smoothly proceeded with successive Claisen rearrangement to give the corresponding 3-allyl-3-cyanomethylindolin-2-ones 15. Indolin-2-ones 15 were converted into pyrrolo[2,3-b]indoles 6 using partial hydrolysis followed by reductive cyclization with LiAlH(4). Synthesis of N-methylated pyrrolo[2,3-b]indole derivatives 23 and 26 is also described.
Fused pyrrole derivatives R 0160 Synthesis of Diversely Functionalized Hexahydropyrrolo[2,3-b]indoles Using Domino Reactions, Olefination, Isomerization and Claisen Rearrangement Followed by Reductive Cyclization. -A new and efficient route to biologically interesting pyrroloindoles is developed. -(KAWASAKI*, T.; OGAWA, A.; TERASHIMA, R.; SAHEKI, T.; BAN, N.; SEKIGUCHI, H.; SAKAGUCHI, K.-E.; SAKAMOTO, M.; J. Org. Chem. 70 (2005) 8, 2957-2966; Meiji Pharm. Univ., Kiyose, Tokyo 204, Japan; Eng.) -Jannicke 37-116
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