Asymmetric hetero-Diels-Alder Reaction oftrans-1-Methoxy-3-trimethylsilyloxy-buta-1,3-diene Catalyzed by Zinc Complexes

Asymmetric hetero-Diels-Alder reactions of Danishefsky's diene and glyoxylate/pyruvate esters catalyzed by readily available zinc triflate complex with BOX ligand afforded the corresponding adduct which upon treatment with trifluoroacetic acid furnished the hetero-Diels-Alder product in 91 % enantiomeric excess and 87 % isolated yield. This reaction was applied to the concise synthesis of six-membered ulosonic acidC-glycoside.