text: The Shibasaki synthesis ((-) chiral, 2002) was a second published method in strychnine total synthesis using an asymmetric reaction step. Cyclohexenone 1 was reacted with dimethyl malonate 2 in an asymmetric Michael reaction using AlLibis(binaphthoxide) to form chiral diester 3. Its ketone group was protected as an acetal (2-ethyl-2-methyl-1,3-dioxolane, TsOH) and a carboxyl group was removed (LiCl, DMSO 140 °C) in monoester 4. A C2 fragment was added as Weinreb amide 5 to form PMB ether 6 using LDA. The ketone was then reduced to the alcohol (NaBHCN, TiCl) and then water was eliminated (DCC, CuCl) to form alkene 7. After ester reduction (DIBAL) to the alcohol and its TIPS protection (TIPSOTf, triethylamine), the acetal group was removed (catalytic CSA) in ketone 8. Enone 9 was then formed by Saegusa oxidation. The conversion to alcohol 10 was accomplished via a Mukaiyama aldol addition using formaldehyde, iodonation to 11 (iodine, DMAP) was followed by a Stille coupling (Pddba, PhAs, CuI) incorporating nitrobenzene unit 12.  Alcohol 13 was formed after SEM protection (SEMCl,i-Pr2NEt) and TIPS removal (HF).
  In the second part of the sequence alcohol 13 was converted to a triflate (triflic anhydride, N,N-diisopropylethylamine), then 2,2-bis(ethylthio)ethylamine 14 was added immediately followed by zinc powder, setting of a tandem reaction with nitro group reduction to the amine, 1,4-addition of the thio-amine group and amine-keto condensation to indole 16. Reaction with DMTSF gave thionium attack at C7 forming 17, the imine group was then reduced (NaBHCN, TiCl), the new amino group acylated (acetic anhydride, pyridine), both alcohol protecting groups removed (NaOMe / meOH) and the allyl alcohol group protected again (TIPS). This allowed removal of the ethylthio group (NiCl, NaBH, EtOH/MeOH) to 18. The alcohol was oxidized to the aldehyde using a Parikh-Doering oxidation and TIPS group removal gave hemiacetal 19 called (+)-diaboline which is acylated Wieland-Gumlich aldehyde.