establishing the required stereogenic center rather than reagent control. During the course of the total synthesis toward GibberellinA3 (1), a model compound (21) as the A-ring of 1 was accomplished in five overall steps with an overall yield of 15 %, starting from furfural through conjugate addition of lithium trimethylzincate to oxabicyclo[2.2.1]heptadienedicarboxylic ester (2) as the key step. Relative