(+)-Neomethynolide, the aglycone of a twelve-membered ring macrolide, neomethymycin, was totally synthesized via its 8,9-didehydro derivative. The synthesis also established the stereochemistry of neomethynolide at C-10, C-11, C-12, and 8,9-double bond which had remained unproved.
Neomethynolide (1), the aglycone of a twelve-membered ring macrolide, neomethymycin, was totally synthesized in its optically active form via 8,9-didehydro-1. The construction of the skeleton was carried out by condensing a stereoselectively synthesized fragment, 4-t-butyldimethylsiloxy-5-(2-methoxyethoxymethoxy)3-methyl-1-hexyne, with Prelog-Djerassi lactonic ester, and mixed anhydride method was used for the lactonization of an intermediary hydroxy acid. The full stereochemistry of 1 was established by this synthesis.