the use of (R)-18 as the chiral building block to construct the γ-lactone-δ-lactam core 3 and cross-olefin metathesis as the key reaction to couple the latter with the allylicalcohol segment (R- or S-4). The efficient construction of the core 3 was realized by taking advantage of the inherent multiple reactivities of the chiral building block (R)-18. A highly diastereoselective one-pot transformation
The first asymmetrictotalsynthesis of the unnatural enantiomer of cytotoxic awajanomycin (1) is reported. The synthetic approach features first a convergent strategy using the cross-olefin metathesis reaction to link the lipid side chain 2 and the piperidinone core structure 3. The second feature of the synthesis resides on the construction of segment 3 from the building block 5 via a three-component