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Stereocontrolled Synthesis of a C n –C n +6 Building Block for the Unnatural Enantiomers of Important Polyol,Polyene Antibiotics from an Epoxy Alcohol by a Reduction/Conjugate Addition/Hydroxylation Sequence
Author(s) -
Kramer Rainer,
Brückner Reinhard
Publication year - 2013
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.201300182
Subject(s) - chemistry , moiety , polyene , enantiomer , oxaziridine , stereochemistry , stereoselectivity , diol , epoxide , polyol , aliphatic compound , organic chemistry , medicinal chemistry , catalysis , polyurethane
Epoxy alcohol anti ‐ 10 , derived from a desymmetrizing Sharpless epoxidation (up to 97 % ee ) of divinylcarbinol 9 , provided the unsaturated 1,3‐diol syn ‐ 11 upon treatment with RedAl ® ; syn ‐ 11 was converted into the α,β‐unsaturated esters ( E )‐ or ( Z )‐ 7b in three steps. Cu‐promoted 1,4‐addition of vinylmagnesium halides to the ( E )‐ester proceeded with diastereoselectivities of up to 91 % and Cu‐catalyzed 1,4‐additions with diastereoselectivities of up to 82 %. The potassium enolate of the major vinylation product syn ‐ 22b was hydroxylated by the Davis oxaziridine with perfect but unprecedented diastereoselectivity. The resulting hydroxy ester, α,β syn , β,γ syn ‐ 32 , furnished the “eastern moiety” building block 6 of the title compounds in three steps.