Synthetic Studies on (+)-Ophiobolin A: Asymmetric Synthesis of the Spirocyclic CD-Ring Moiety

Asymmetric synthesis of the spirocyclic CD-ring moiety of (+)-ophiobolin A is described. Fragment A, which was prepared via pig liver
esterase (PLE)-mediated kinetic resolution, and fragment B, which was prepared via diastereoselective allylation and subsequent kinetic
iodolactonization, were coupled to afford the allylsilane 2, which was successfully cyclized to the desired spirocyclic CD-ring moiety 1a in the
presence of a Lewis acid.