Total Synthesis of Pactamycin and Pactamycate: A Detailed Account

This article describes synthetic studies that culminated
in the
first total synthesis of pactamycin and pactamycate and, in parallel,
the two known congeners, de-6-MSA-pactamycin and de-6-MSA-pactamycate,
lacking the 6-methylsalicylyl moiety. Starting with l-threonine
as a chiron, a series of stereocontrolled condensations
led to a key cyclopentenone harboring a spirocyclic oxazoline. A series
of systematic functionalizations led initially to the incorrect cyclopentanone
epoxide, which was “inverted” under solvolytic conditions.
Installation of the remaining groups and manipulation of the oxazoline
eventually led to pactamycin, pactamycate, and their desalicylyl analogues.