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Enantioselective Butenolide Preparation for Straightforward Asymmetric Syntheses of γ‐Lactones – Paraconic Acids, Avenaciolide, and Hydroxylated Eleutherol
Author(s) -
Braukmüller Stefan,
Brückner Reinhard
Publication year - 2006
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200500961
Subject(s) - chemistry , enantioselective synthesis , butenolide , dihydroxylation , lactone , enantiomer , stereochemistry , organic chemistry , carboxylic acid , catalysis
Abstract The naturally occurring γ‐lactones (+)‐methylenolactocin ( 13 ) and its enantiomer, (+)‐protolichesterinic acid ( 14 ) and its enantiomer, (+)‐rocellaric acid ( 15 ), and the methylene bis(γ‐lactone) (–)‐avenaciolide ( 16 ) were synthesized with 95–98 % ee s in very few steps. Enantiocontrol was imposed by the asymmetric dihydroxylation of trans ‐configured β,γ‐unsaturated carboxylic esters (namely compounds 1i , 1j , and 1n ) with AD mix‐α ® [for the levorotatory target structures, except for (–)‐avenaciolide] or AD mix‐β ® [for the dextrorotatory target structures plus (–)‐avenaciolide]. β,γ‐Unsaturated carboxylic ester 1e required increased amounts of the oxidant and auxiliary to produce the hydroxy lactone R , R ‐ 3e , a precursor of the naphtho‐γ‐lactone (+)‐9‐hydroxyeleutherol ( 12 ; 96 % ee ). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)