The first synthetic efforts toward marineosins A and B, novel spiroaminals from a Streptomyces actinomycete, are described by evaluation
of the proposed biosynthesis. The hypothesized biosynthetic C1-C25 Diels-Alder substrate was prepared in 8 steps in 5.1% overall yield;
however, the proposed biomimetic inverse-electron-demand hetero-Diels-Alder reaction failed to deliver the marineosin core. Molecular mechanics
supports this observation.