Total Synthesis Highlights

33. The Burke Synthesis of (+)-Didemniserinolipid B
The sulfate (+)-didemniserinolipid B (3), isolated from the tunicate Didemnum sp, has an
intriguing spiroether core. A key step in the synthesis of 3 reported (Org. Lett. 2007, 9, 5357. ) by
Steven D. Burke of the University of Wisconsin was the selective ring-closing metathesis of 1 to
2.
The diol 6 that was used to prepare the ketal 1 was readily prepared from the inexpensive
D-mannitol (4). Many other applications can be envisioned for the enantiomerically-pure diol 6
and for the monoacetate and bis acetate that are precursors to it.
To set up the metathesis, the β,γ-unsaturated ketone 10 was needed. To this end, the keto
phosphonate derived from the addition of the phosphonate anion 8 to the lactone 7 was condensed
with phenyl acetaldehyde 9. The derived enone 10 was a 5:1 mixture of β,γ- and α,βregioisomers.