Functionally substituted vinyl carbanions, 43. Convenient transformation of hexopyranosides into α-methylene δ-lactone derivatives
✍ Scribed by Kast, Jürgen ;Hoch, Monika ;Schmidt, Richard R.
- Publisher
- John Wiley and Sons
- Year
- 1991
- Tongue
- English
- Weight
- 482 KB
- Volume
- 1991
- Category
- Article
- ISSN
- 0947-3440
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✦ Synopsis
Abstract
Treatment of glycopyranosyl phenyl sulfoxides 2ah, 1, 2bh, 1 with two equivalents of lithium diisopropylamide provides directly the C‐2‐lithiated glycal intermediates 3aAh, 1, 3bAh, 1 which, on reaction with formaldehyde as electrophile, furnish the 2‐hydroxymethyl derivatives 4ah, 1 and 4bh, 1, respectively. These compounds are transformed at elevated temperature and by acid catalysis directly into the α‐methylene‐δ‐lactones 5a, b. Correspondingly, from 2ah, 1 and methyl chloroformate as electrophile the 2‐methoxycarbonyl derivatives 6h and 61, respectively, are obtained. Treatment of 6h, 1 with Raney nickel leads to 2‐methoxycarbonyl‐substituted glycal 7 containing a β‐alkoxyacrylate moiety which again can be directly β‐C‐lithiated as demonstrated by the introduction of deuterium at C‐1.