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Stereocontrolled Synthesis of the C 21 –C 38 Fragment of the Unnatural Enantiomer of the Antibiotic Nystatin A 1
Author(s) -
Berkenbusch Thilo,
Brückner Reinhard
Publication year - 2004
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200305540
Subject(s) - polyene , stereochemistry , stereoselectivity , chemistry , aldol reaction , enantiomer , adduct , lactone , aldehyde , intramolecular force , stereoisomerism , propionates , molecule , organic chemistry , catalysis
The C 21 –C 38 fragment all‐ trans ‐ 41 of the unnatural enantiomer 1 of nystatin A 1 was prepared starting from the N ‐propionyl oxazolidinone 9 . Aldol adduct ent ‐ 8 ( ee > 96 %) derived in two steps was hydroborated with (thexyl)BH 2 . Oxidative work‐up and treatment with acid furnished δ‐lactone 4 . It contains the complete stereotetrade of the target molecule. The α,β‐unsaturated ester 28 was reached after another four steps. It should be a precursor for the polyene moieties of a variety of polyol,polyene macrolides. Illustrating that, the α,β‐unsaturated aldehyde 29 obtained from 28 and DIBAL was extended by 10 C atoms in four steps yielding the C 21 –C 38 segment 41 . The latter set of transformations included the regio‐ and stereoselective Claisen rearrangement 32 → 35 .