Scheme 26. Tan's branching pathways which yield stereochemically and substitutionally diverse polyketide-like molecules. Reagents and conditions: (1) Cp₂TiCl₂, iBuMgBr, Et₂O, 0 °C → rt, 81–86%, >88 : 12 Z:E; (2) Red-Al, Et₂O, 0 °C → rt, 99%, >98 : 2 E:Z; (3) m-CPBA, NaHCO₃, CH₂Cl₂, 0 °C → rt (R = H) or –4 °C (R = Me), 91–99%, d.r. >90 : 10; (4) diethyl tartrate (matched enantiomer), Ti(OiPr)₄, tBuOOH, 4 Å sieves, CH₂Cl₂, –20 °C, (R = H) or –20 °C, (R = Me), 85–93%, d.r. 94 : 6; (5) (i) nBuLi, Me₃Al, 1,2-dichloroethane, 0 °C→ rt; (ii) NaIO₄, MeCN–H₂O, 0 °C→ rt, 68–69% (over 2 steps); (6) Dess–Martin periodinane, CH₂Cl₂, 0 °C→ rt, 85–100%; (7) SmI₂, THF, –90→ –78 °C, 65–98%; (8) NaBH(OAc)₃, AcOH, MeCN, –20 °C, 87–95%, d.r. >93 : 7; (9) Et₂BOMe, NaBH₄.