4-Isopropyl-2-oxazolin-5-one anion as masked umpoled synthon for both formyl and hydroxycarbonyl anions: generation, reactivity and synthetic applications

The anion of the title compound, simply generated in the presence of catalytic amount of triethylamine, reacts with both common electrophilic olefins and aldehydes to give moderate to good yield of Michael or aldol adducts respectively. Mild acid treatment of these adducts at ambient temperature serves to demask the aldehyde function, allowing one to consider the anion of the title compound as a nucleophilic acylating equivalent of formaldehyde. On the other hand, the same anion may act as a masked umpoled synthon for a hydroxycarbonyl anion since its aldol adducts with aldehydes underwent concomitant isomerization and ring cleavage under mild basic conditions producing dipeptides which could be hydrolyzed to give the corresponding carboxylic acids. Synthetic applications of this chemistry in the area of sugar, aminosugar and non-proteinogenic aminoacid derivatives are discussed.