Enantioselective syntheses of colletodiol, colletol, and grahamimycin A.

[reaction: see text] The enantioselective synthesis of colletodiol has been achieved in 11 steps from methyl 1,3,5-octatrienoate and 16 total steps from both ethyl sorbate and methyl 1,3,5-octatrienoate. The route relies upon an enantio- and regioselective Sharpless dihydroxylation and a palladium-catalyzed reduction to form a 5-hydroxy-1-enoate and an 7-hydroxy-1,3-dienoate. These esters were further functionalized, coupled, and macrolactonized to provide colletodiol after deprotection. Grahamimycin A and colletol were synthesized in one and two steps, respectively, from colletodiol.