Rapid Synthesis of the Spiroketal Subunit of Neaumycin B: Stereochemical Aspects of Singly Anomeric Spiroketals and Proposal for a Stereocenter Reassignment

Neaumycin B is a complex polyketide that shows phenomenal
cytotoxicity
against U87 glioblastoma cells. The singly anomeric spiroketal core
is a notable subunit in the natural product’s structure. We
report a rapid and convergent approach to the spiroketal group, resulting
in the formation of two isomeric singly anomeric spiroketals. We describe
the origin of this rarely described outcome in spirocycle formation
and subsequently propose a correction to a stereocenter in the natural
product.