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. Author manuscript; available in PMC: 2016 Oct 2.
Published in final edited form as: J Org Chem. 2015 Oct 2;80(19):9740–9766. doi: 10.1021/acs.joc.5b01844

Scheme 8. Synthesis of Enone 53 and Attempts at D Ring Synthesisa.

Scheme 8

aReagents and conditions: (a) TBSOTf, 2,6-lutidine, CH2Cl2, −50 °C; (b) n-BuLi, THF, −50 °C to rt, then DMF; (c) Ph3P=CH2, THF, 0 °C; (d) nitroethylene, CH2Cl2, 65 °C; (e) (i) KOH, MeOH, rt, then MsOH, 0 °C to rt; (ii) DBU, CH2Cl2, rt.