Summary: Lithium diisopropylamide (LDA) removes the a-proton from the O-methyl tetronic acid (2b) leading to the vinylic carbanion (12), whereas treatment of the trimethylsilyl derivative (14) with LDA,' followed by reaction with aldehydes gives products resulting from both y- and E-addition; the directed metallations provide access to a range of 4-oxy-2-furanone derivatives found amongst natural products. ... A wide variety of compounds containing the 4-oxy-2- ...
