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Enantioselective Diels‐Alder Approach to C‐3‐Oxygenated Angucyclinones from (S S )‐2‐( p‐ Tolylsulfinyl)‐1,4‐naphthoquinone
Author(s) -
Carreño M. Carmen,
Urbano Antonio,
Di Vitta Claudio
Publication year - 2000
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/(sici)1521-3765(20000303)6:5<906::aid-chem906>3.0.co;2-g
Subject(s) - chemistry , enantioselective synthesis , sulfoxide , naphthoquinone , cyclohexene , enantiomer , kinetic resolution , olefin fiber , stereochemistry , steric effects , cycloaddition , diene , ring (chemistry) , derivative (finance) , medicinal chemistry , organic chemistry , catalysis , natural rubber , financial economics , economics
Chiral racemic vinylcyclohexenes 2 , bearing oxygenated substituents and/and a methyl group at the C‐5 position of the cyclohexene ring, were submitted to Diels‐Alder reactions with enantiomerically pure (S S )‐(2‐ p ‐tolylsulfinyl)‐1,4‐naphthoquinone [(+)‐ 1 ]. The domino cycloaddition/cycloaddition sulfoxide elimination process led to the formation of enantiomerically enriched angularly tetracyclic quinones anti ‐ 6 and syn ‐ 7 , which were obtained from the kinetic resolution of the racemic diene. In all cases, (S S )‐(2‐ p ‐tolylsulfinyl)‐1,4‐naphthoquinone reacted from the less hindered face of the more reactive s‐cis conformation, to form products in good enantiomeric excesses. Steric effects and torsional interactions in the corresponding approaches account for the observed π‐facial diastereoselectivities at both partners. The usefulness of this methodology is illustrated with the four‐step totally asymmetric synthesis of the C‐3‐oxygenated angucyclinone derivative (−)‐8‐deoxytetrangomycin 10 in 26 % overall yield and with 50 % enantiomeric purity.