Diastereodivergent Strategies for the Synthesis of Homochiral Aculeatins
摘要:
We report concise and stereocontrolled syntheses of aculeatins (-)-A, (+)-B, (+)-D, and (+)-6-epi-D. Diastereodivergent 1,3-inductions in Mukaiyama aldol coupling contribute to reduce steps and to increase flexibility with reactants having sterically restricted proximal substituents (i.e., CH2), involving either a good anti or a moderate syn 1,3-induction, depending on the nature of protecting group (P). In addition, the 3,5-syn-diol-ketone resulting from concomitant deprotection of the beta-alkoxy (Tr = trityl) group proves to be remarkably stable whereas the 3,5-anti diastereoisomer cyclizes spontaneously to the corresponding tetrahydropyran hemiketal, thus enabling a useful and facile separation. The second part of our study is devoted to improving the yield and the diastereoselectivity of the final phenolic oxidation reaction leading to aculeatins.
Remote Asymmetric Induction in an Intramolecular Ionic Diels−Alder Reaction: Application to the Total Synthesis of (+)-Dihydrocompactin
作者:Tarek Sammakia、Deidre M. Johns、Ganghyeok Kim、Martin A. Berliner
DOI:10.1021/ja043506g
日期:2005.5.1
The total synthesis of (+)-dihydrocompactin via an intramolecular ionic Diels-Alder reaction that proceeds with remote stereocontrol is described. This reaction proceeds by an intermediate vinyl-oxocarbenium ion (6), the conformational constraints of which lead to the observed asymmetricinduction. The sense of asymmetricinduction appears contrasteric and is explained by the proposed reactive conformation
作者:Jhillu S. Yadav、G. Madhusudhan Reddy、S. Rehana Anjum、B. V. Subba Reddy
DOI:10.1002/ejoc.201402235
日期:2014.7
A formalsynthesis of herboxidiene/GEX 1A is described. This approach demonstrates successful application of the Prins cyclization for the construction of the tetrahydropyran core of the target molecule. The chirality of the side chain has been established through the Sharpless asymmetric dihydroxylation and Evan's alkylation. The olefin cross-metathesis was applied to couple both key fragments.