Galacturonic Acid Derivatives, IX. Regioselective Enzymatic Acetyl Ester Hydrolysis ofD-Galacturonic Acid Derivatives and Related Reactions
✍ Scribed by Vogel, Christian ;Kramer, Sven ;Ott, Andrej-Jakob
- Book ID
- 102365996
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 420 KB
- Volume
- 1997
- Category
- Article
- ISSN
- 0947-3440
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✦ Synopsis
Abstract
A number of D‐galacturonic acid derivatives (1, 3, 7 and 9) have been selectively deacetylated in enzyme‐catalyzed reactions. The 2‐O‐acetyl groups were selectively hydrolyzed from 2,3,4‐tri‐O‐acetyl‐β‐D‐galactopyranurono‐6,1‐lactone (1), and methyl [methyl (3) and benzyl (7) 2,3,4‐tri‐O‐acetyl‐β‐D‐galactopyranosid]uronates, affording the specifically deacetylated products in good to excellent yields. The methyl 1,2,3,4‐tetra‐O‐acetyl‐α‐D‐galactopyranuronate (9) was hydrolyzed at the anomeric position in 48% yield using the acylase from Aspergillus melleus (E~1~), whereas the lipases from wheat germ (E~5~ and E~7~) catalyzed the selective cleavage of the acetyl groups in both the 1‐ and 2‐O‐positions, furnishing the methyl 3,4‐di‐O‐acetyl‐D‐galactopyranuronate (12) in 46% isolated yield. The latter compound was obtained in nearly quantitative yield by selective enzymatic deacetylation at the 2‐O‐position of 7, followed by hydrogenolytic cleavage of the anomeric O‐benzyl group. Isopropylidenation of 12 furnished the hitherto unknown methyl 3,4‐di‐O‐acetyl‐1,2‐O‐isopropylidene‐α‐D‐galactopyranuronate (13).