calendic acid synthesis

Yield:-

Steps:

Multi-step reaction with 8 steps
1: 1.) n-butyl-lithium / 1.) TFH/HMPA/hexane, 0 deg C; 2.) THF/HMPA/hexane, 30 min, r.t.
2: deuterium / chlorotris(triphenylphosphine)rhodium / benzene-d6 / 12 h
3: 71 percent / PPTS / ethanol / 3 h / 35 °C
4: 68 percent / PCC / CH₂Cl₂ / 2 h / 20 °C
5: 46 percent / deuterium oxide / pyridine / 7 h / 90 - 95 °C / procedure repeated twice more
6: 1.) t-butyl-lithium / 1.) hexane, 0 deg C, 5 min; 2.) THF, 0 deg C -> r.t., 2 h
7: potassium hydroxide / aq. ethanol
8: marigold (Calendula officinalis) seed homogenate

References:

Crombie, Leslie;Holloway, Stephen J. [Journal of the Chemical Society. Perkin transactions I,1985,p. 2425 - 2434]