Scheme 2.

Synthesis of fragments 8 and 9 from aldehyde 15.a

^a Reagents and conditions: (a) (−)-DIPT, Ti(Oi-Pr)₄, t-BuOOH, 32% (92% ee); (b) PivOH, Ti(Oi-Pr)₄; (c) Me₂C(OMe)₂, PPTS; (d) MeLi, 59% over three steps; (e) (COCl)₂, DMSO, Et₃N; (f) CBr₄, Ph₃P, CH₂Cl₂, 65% over two steps; (g) n-BuLi, THF, 90%; (h) cat. AIBN, Bu₃SnH, C₆H₆; (i) I₂, CH₂Cl₂, 80% over two steps; (j) 1N HCl (aq.), 72%; (k) Ph₃P=CH₂; (l) 1 N HCl (aq.), 53% over three steps from 14.