Organocatalytic Asymmetric Double Addition of Kojic Acids to 2‐Nitroallylic Carbonates

Abstract

2-Nitroallylic carbonates were first applied as promising biselectrophilic C3 synthons for bifunctional squaramide catalyzed asymmetric domino reaction with kojic acid derivatives to afford so far inaccessible nitro compounds bearing two hydroxypyranone units. The reaction products undergo noncatalytic epimerization at the carbon atom next to the nitro group. Plausible mechanism of the epimerization based on reversible formation of intermediate aci-nitro compound is proposed. The double addition products were transformed to configurationally stable acetates and to chiral nitro glutarates, promising precursors to chiral amino glutaric acid derivatives.

Total synthesis of (S)-forphenicinol via asymmetric organocatalysis

“…Herein, we report more efficient and convenient approach to asymmetric synthesis of (+)-(S)-forphenicinol. It is based on the formation of key stereogenic center via enantioselective Mannich-type reaction of appropriate aryl aldimine with allomaltol an available natural kojic acid derivative, [17][18][19][20][21] in the presence of chiral aminocatalyst followed by oxidative fragmentation of the g-pyranone fragment to the carboxylic group (Scheme 1c).…”

Hydroxy-directed iridium-catalyzed enantioselective formal β-C(sp2)–H allylic alkylation of α,β-unsaturated carbonyls

“…11 Later on, Zlotin and Reddy groups independently disclosed kojic acid as a nucleophile in organocatalytic asymmetric Michael reactions with electrophilic partners such as nitroolefins and β,γ-unsaturated α-ketoesters. 12 Nonetheless, compared to these organocatalytic reactions, metal catalyzed transformations of kojic acid are rare, 13 let alone their enantioselective variants. 14…”

Concise enantioselective synthesis of non-proteinogenic α-aminoacids via an organocatalytic Mannich-type reaction

“…The amino-group-free 2-substituted γ-pyrones have been recently converted to corresponding carboxylic acids via Ru III -catalyzed oxidative fragmentation. 13 Electron-rich furan and pyrrole derivatives also undergo Ru III -catalyzed oxidative cleavage. 14 a , b…”