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Synthesis of (−)‐Streptenol A, (±)‐Streptenol B, C and D
Author(s) -
Blechert Siegfried,
Dollt Heribert
Publication year - 1996
Publication title -
liebigs annalen
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0947-3440
DOI - 10.1002/jlac.199619961228
Subject(s) - chemistry , acetaldehyde , isomerization , stereoselectivity , acetonide , hydrolysis , stereochemistry , palladium , cleavage (geology) , wacker process , grignard reaction , medicinal chemistry , catalysis , organic chemistry , ethanol , medicine , surgery , geotechnical engineering , reagent , triamcinolone acetonide , fracture (geology) , engineering
2‐(2,2‐Dimethyl‐1,3‐dioxan‐4‐yl)acetaldehyde ( 3 ) was used for the preparation of streptenol A and B (Scheme 1) via a Grignard reaction with 1‐bromopent‐3‐ene. Hereby optically pure (4′ R )‐ 3 gave the antipode of Streptenol A. Reaction with lithiated 1‐pentyne opened access to streptenol C and D. To obtain the dienone structure of streptenol C and D, a palladium‐catalyzed alkynone isomerization was induced. Kinetic differences in the acid‐mediated cleavage of the 1,3‐acetonide protected 1,3,5‐triol system caused the stereoselectivity in the natural products. So only the (3 S * ,5 R * ) acetonide of streptenol B reacted under mild hydrolytic conditions and gave after transacetalization first a 3,5‐protected streptenol B with pure relative stereochemistry and finally (3 S * ,5 R * )‐streptenol B.