Total Synthesis Highlights

The side chain nitrile was prepared from the diol 12. Homologation gave the nitrile 14, that was
equilibrated to the more stable enol ether 15. The two cyclic quaternary centers of 3 were set in a
single step, by the conjugate addition of the anion of 16 to the crystalline enone 11. Mild
hydrolysis of 17 gave the keto aldehyde, that underwent aldol condensation to give the enone 18.
The hydroboration of 19 followed by coupling of the intermediate organoborane with 20 delivered
21 with 94:6 relative diastereocontrol. Formylation of the enone 22 followed by triflation and
reduction then led to 2.
Although the ketone 1 could be deprotonated with LDA, the only product observed, even at -78°C,
was the derived aldol dimer. The metalated dimethylhydrazone 25, in contrast, coupled smoothly
with 2 to give, after hydrolyis, the desired adduct 26. Pd-mediated carboxylation of the enol
triflate followed by selective oxidative cleavage and hydrolysis then completed the synthesis of
(-)-Glycinoecleptin A (3).
D. F. Taber, Org. Chem. Highlights 2011, January 3.
URL: http://www.organic-chemistry.org/Highlights/2011/03January.shtm
4. The Chen Synthesis of (-)-Nakiterpiosin
(-)-Nakiterpiosin (3), isolated from the thin encrusting sponge Terpios hoshinota, has an IC 50
against murine P388 leukemia cells of 10 ng/mL. Chuo Chen of UT Southwestern Medical Center