Total Synthesis of the GRP78-Downregulatory Macrolide (+)-Prunustatin A, the Immunosuppressant (+)-SW-163A, and a JBIR-04 Diastereoisomer That Confirms JBIR-04 Has Nonidentical Stereochemistry to (+)-Prunustatin A

A unified total synthesis of the GRP78-downregulator (+)-prunustatin A and the immunosuppressant (+)-SW-163A based upon [1 + 1 + 1 + 1]-fragment condensation and macrolactonization between O(4) and C(5) is herein described. Sharpless asymmetric dihydroxylation was used to set the C(2) stereocenter present in both targets. In like fashion, coupling of the (+)-prunustatin A macrolide amine with benzoic acid furnished a JBIR-04 diastereoisomer whose NMR spectra did not match those of JBIR-04, thus confirming that it has different stereochemistry than (+)-prunustatin A.