Nordidemnin B (3), a cyclodepsipeptide isolated from a sea tunicate, was prepared by following a segment strategy which will permit further structural modifications. The non- proteinogenic D-Val-+(CHOH)-Gly-HIP subunit was elaborated sequentially by using a P- keto ester preparation via lithium enolate condensation with 2-acyl-3, 5-dioxo-4-methyl-l, 2, 4-oxadiazolidine (acyl-MODD) derivatives. Isopropenyl chlorocarbonate activation was ...
