Scheme 2.

Synthesis of key intermediate 9 and unsuccessful attempts at its conversion to 1. Reagents and conditions: a) AlMe₃, CuTC/L¹* (2.4 mol %), Et₂O, −30 °C, 4.5 h; then MeLi, 12, TPPA, −30→25 °C, 17 h; b) LDA, THF, PhNTf₂, −78→25 °C, 3 h; c) 15, 9‐BBN, THF, 25 °C, 2 h; then 14, Pd(dppf)Cl₂ (3 mol %), Cs₂CO₃, H₂O, DMF, 25 °C, 1 h; d) Bi(OTf)₃ (4 mol %), CH₃CN/H₂O, 25 °C, 1.5 h, 97 %; e) DMP, CH₂Cl₂, 0→25 °C, 2 h, 86 %; f) AuCl₃ (5 mol %), CH₂Cl₂, 0 °C, 11 min; g) BH₃ ⋅THF, THF, 0→30 °C, 10 h; then NaOH, H₂O₂, THF/H₂O, 0→25 °C, 14 h; h) DMP, CH₂Cl₂, 0→30 °C, 2 h; i) LiH, TPPA, 160 °C, 1.5 h; then MeI, 25 °C, 20 h; j) ZnEt₂, CH₂I₂, DCE, 25 °C, 35 min; k) aq. HCl, MeOH, reflux, 35 min. CuTC=copper(I) thiophene‐2‐carboxylate, TPPA=tripyrrolidinophosphoric acid triamide, LDA=lithium diisopropylamide, TBS=tert‐butyldimethylsilyl, 9‐BBN=9‐borabicyclo[3.3.1]nonane, dppf=1,1′‐bis(diphenylphosphino)ferrocene, DMP=Dess–Martin periodinane, DCE=dichloroethane.