Studies directed towards the total synthesis of (+)-himbacine

A convergent strategy towards himbacine (1), involving a Julia coupling between aldehyde 5 and sulfone 6 was found to be ineffective. The aldehyde 5 was synthesized via the thermal intramolecular cycloaddition of 4 with preferred formation of the endo-adduct. The Diels-Alder precursor 4 was obtained from butenolide 7, the result of a single-step condensation between the enoate derived from the (Z)-conjugated olefin 12 and 2-acetoxypropanal. In the context of the synthesis of sulfone 6 Taber's method for the synthesis of 2,6-trans-disubstituted piperidine was adapted towards a large scale synthesis of 49, a useful intermediate for the synthesis in this area.