Synthesis of the C38-C44 segment of altohyrtin A - With an addendum on thepreparation of 8-oxabicyclo[3.2.1]oct-6-en-3-one

The densely funkctionalized C38-C44 segment F of altohyrtin A with its five contiguous stereogenic centers was prepared in 10 steps and in 28 % overal l yield (two steps per stereogenic center), from 8-oxabicyclo[3.2.1]oct-6-e n-3-one as a template. The preparation of the title compound 1, m.p. 38 deg rees C, is described on a 0.5-m scale in a three-step-two-stage reaction fr om acetone and furan. The oxacycle was stored without change at room temper ature.