posted on 2014-01-17, 00:00authored byZhihui Peng, John A. Ragan, Roberto Colon-Cruz, Brian G. Conway, Eric M. Cordi, Kyle Leeman, Leo J. Letendre, Li-Jen Ping, Janice
E. Sieser, Robert A. Singer, Gregory W. Sluggett, Holly Strohmeyer, Brian C. Vanderplas, Jon Blunt, Nicola Mawby, Kevin Meldrum, Stuart Taylor
This
paper describes an improved sequence for the conversion of an oxazolidinone
(3) to a β-keto lactone (5). The primary
drivers behind this change were the modest and variable yields observed
in the intramolecular cyclization to generate the β-keto lactone.
Changing the cyclization substrate from oxazolidinone to alkyl ester
offered a significantly improved cyclization, as well as improvements
in the alkyne hydrogenation. Selection of the optimal substrates for
methanolysis and intermediate salt formation are also described.