A Diastereoselective,
Nucleophile-Promoted Aldol-Lactonization
of Ketoacids Leading to Bicyclic-β-Lactones
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Abstract
An improved, tandem acid activation/aldol-lactonization
process
is described. This more practical protocol shortens reaction times
for the construction of bicyclic β-lactones from ketoacids and
implements the use of commercially available reagents <i>p</i>-toluenesulfonyl chloride (<i>p</i>-TsCl) as activator
and 4-dimethylaminopyridine (4-DMAP) as nucleophilic promoter (Lewis
base). Substrates with β-substituents, with respect to the carboxylic
acid, consistently showed excellent levels of diastereoselectivity
during the bis-cyclization event