Fig. 3
Synthesis of 15a. Reagents and conditions: (a) 8 or 9 (2.0 equiv), K2CO3 (1.5 equiv), acetone, rt, overnight (75−80%); (b) Yeast extract (50 wt%), D-glucose, dry active baker’s yeast, H2O, rt, 36 h (67%); (c) p-NO2-C6H4CO2H (2.0 equiv), PPh3 (2.0 equiv), DEAD (2.0 equiv), THF, 0 to 50 °C, overnight (90%); (d) K2CO3 (2.0 equiv), MeOH/THF (v/v = 1:2), 0 oC, 30 min (98%); (e) TBSCl (1.2 equiv), imidazole (1.2 equiv), DMF, rt, overnight (91%); (f) NaH (5.0 equiv), iPrI (10.0 equiv), THF, reflux, overnight; then aq. HCl (2 M), rt, 1.5 h (88%); (g) LiHMDS (1.3 equiv, 1.0 M in THF), PhNTf2 (1.3 equiv), THF, −78 oC to rt, 3 h (80%). DEAD diethyl azodicarboxylate, TBSCl t-butyldimethylsilyl chloride, LiHMDS lithium hexamethyldisilazide, THF tetrahydrofuran, DMF N,N-dimethylformamide
