Regio- and diastereocontrolled C–H insertion of chiral γ- and δ-lactam diazoacetates. Application to the asymmetric synthesis of (8S,8aS)-8-hydroxyindolizidine
α,β-Unsaturated Diazoketones as Platforms in the Asymmetric Synthesis of Hydroxylated Alkaloids. Total Synthesis of 1-Deoxy-8,8a-diepicastanospermine and 1,6-Dideoxyepicastanospermine and Formal Synthesis of Pumiliotoxin 251D
作者:Barbara Bernardim、Vagner D. Pinho、Antonio C. B. Burtoloso
DOI:10.1021/jo301967w
日期:2012.11.2
A versatile and concise approach for the stereoselective synthesis of mono-, di-, and trihydroxylated indolizidines is presented in four to six steps from Cbz-prolinal and a diazophosphonate. The key steps involved a Wolff rearrangement, followed by a stereoselective dihydroxylation/epoxidation reaction, from an α,β-unsaturated diazoketone. The strategy also permits extension to the synthesis of many
Nonracemic Bicyclic Lactam Lactones via Regio- and <i>cis</i>-Diastereocontrolled C−H Insertion. Asymmetric Synthesis of (8<i>S</i>,8a<i>S</i>)-Octahydroindolizidin-8-ol and (1<i>S</i>,8a<i>S</i>)-Octahydroindolizidin-1-ol
作者:Andrew G. H. Wee、Gao-Jun Fan、Hypolite M. Bayirinoba
DOI:10.1021/jo901790g
日期:2009.11.6
The Rh-2(MPPIM)(4)-catalyzed intraniolecular C-H insertion reaction of (S)- and (R)-1-benzyl-5-(alpha-diazoacetoxy)piperidin-2-one and (S)-1-benzyl-4-(alpha-diazoacetoxy)pyrrolidin-2-one proceeds with high regioselectivity and cis-diastereoselectivity to give good yields of chiral nonracemic bicyclic lactam lactones (BLLs). For (S)- and (R)-1-benzyl-5-(alpha-diazoacetoxy)piperidin-2-one, the regio selectivity of the C-H insertion is catalyst-dependent; for example, (S)-1-benzyl-5-(alpha-diazoacetoxy)piperidin-2-one undergoes C-H insertion at C-6 preferentially when Rh-2(5S-MPPIM)(4) is used, but with Rh-2(5R-MPPIM)(4), C-H insertion occurs preferentially at C-4. This effect is not observed in the reaction of (S)-1-benzyl-4-(alpha-diazoacetoxy)pyrrolidin-2-one. The utility of the BLLs as chiral building blocks in alkaloid synthesis is exemplified by the synthesis of (8S,8aS)-octahydroindolizidin-8-ol and (1S,8aS)-octahydroindolizidin-1-ol.
Facile Transformation of 2-Azetidinones to 2-Piperidones: Application to the Synthesis of the Indolizidine Skeleton and (8<i>S</i>,8a<i>S</i>)-Perhydro-8-indolizinol
作者:Hyeon Kyu Lee、Jong Soo Chun、Chwang Siek Pak
DOI:10.1021/jo026817n
日期:2003.3.1
The highly functionalized bicyclic lactam 7 was prepared from diolefinic-2-piperidone 18 by the use of ruthenium-catalyzed RCM, and in turn, 18 was derived via a two-carbon addition process from readily accessible 4-olefinic-2-azetidinone 13. Bicyclic lactams 7 and 20 could serve as potentially valuable intermediates for the chiral synthesis of various hydroxylated indolizidine alkaloids as exemplified by the synthesis of (8S,8aS)-perhydro-8-indolizinol 19.