Achiral Aldehydes as Dienophiles

6 HETERO DIELS-ALDER ADDITIONS 13.6.1 Achiral Aldehydes as Dienophiles 

The reaction of 5-nitrofuran-2-carboxaldehyde and 2,3,4,6-tetra-O-acetyl-P-o-glucopyrano-sides of ( , )-4-ethoxy-2-[(r rf-butyl)dimethylsilyloxy]butadiene can be highly diastereoselective depending on the nature of the lanthanide Lewis acid used to promote the cycloaddition (Yb(fod)3, La(fod)3). The adducts thus obtained are readily converted into (3-D-glucopyranosyl (1 4)-linked glycals [136b]. 

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