Reagents and conditions: (a) ethyl phosphite, o-xylene, reflux; (b) oxalyl chloride, dichloromethane, ethyl acetate, DMF (cat.); (c) LDA (1.0 eq), THF, −78 °C; (d) THF, −78 °C; (e) acetic acid, methanol, water; (f) TMSI (6.0 eq), cyclopentene, dichloromethane; (g) KHCO3, water; (h) LDA (2.0 eq), THF, −78 °C; (i) diphenyl diselenide (1.0 eq), THF, −78° to 0 °C; (j) acetic acid, ethyl acetate, water; (k) H2O2 (2.3 eq), acetic acid, THF; (l) TMSI (6.0 eq), cyclopentene, dichloromethane; (m) NaHCO3, water.