Efficient conditions for conversion of 2-substituted furans into 4-oxygenated 2-enoic acids and its application to synthesis of (+)-aspicilin,(+)-patulolide A, and (-)- …
2-Substituted furans 1a, b, c were found to be conveniently transformed into trans 4-oxo-2- enals 2a, b, c in 62-87% yields by using NBS/pyridine in THF-acetone-H2O (<-15° C then rt) or NBS/NaHCO3 in acetone-H2O (<-15° C then rt after addition of pyridine). Further oxidation of the enals 2a-c using NaClO2 led to the trans 4-oxo-2-enoic acids 3a-c in good yields. With this transformation in mind, we designed syntheses of (+)-aspicilin,(+)- ...
