Scheme 9.

Preparation of precursors 41 (A) and 42 (B), as reported by Rizzacasa et al. [86]. Reagents and conditions: (A). i. Admix-α, MeSO₂NH₂, tBuOH, H₂O, 69%; ii. TESCl, imidazole, 93%; iii. Ni (OAc)₂.4H₂O, NaBH₄, EDA, MeOH, 73%; iv. (COCl)₂, DMSO, Et₃N, CH₂Cl₂,78%; v. 1. TIPS-≡-CH₂PPh₃⁺Br⁻, LiHMDS, −78 °C, then addition of 38, −40 °C, (3E,8Z)-isomer 49% and (3Z,8Z)-isomer 12%; vi. TBAF. (B). CH₃CH₂CH₂PPh₃⁺ Br⁻, NaHMDS, −78 °C to 0 °C, 74%; ii. DMP, 93%; iii. TIPS-≡-CH₂PPh₃⁺ Br⁻, nBuLi, THF, −40 °C to 0 °C, (1E,3E,8Z)-isomer 57%, (1Z,3E,8Z)-isomer 26%; iv. TBAF, 73%; v. 1. ZrCp₂Cl₂, iBu₂AlH, THF, 0 °C; 2. I₂, −78 °C, 64%.