5,7-Dihydroxy-1,5,5a,11a,13a-pentamethyl-4,8-dioxo-4,5,5a,5b,6,6a,6b,7,8,8a,9,9a,10a,11,11a,11b,12,13,13a,13b-icosahydro-1H-oxireno[6',7']naphtho[1',2':7,8]fluoreno[2,1-b]furan-6,11,12,13-tetrayl tetraacetate → Taccalonolide B

Participants

Reaction Steps

Taccalonolide A (40 mg) was dissolved in 4 mL of methanol and to this solution 8 mL of 0.05 M sodium bicarbonate was added. The solution was stirred at room temperature for 44 hours. The reaction solution was extracted with EtOAc and purified on HPLC to yield 25.8 mg of taccalonolide B. Taccalonolides N and AB were produced by hydrolysis of taccalonolides E and Z, respectively, using the same method. Taccalonolide AB was obtained as white powder. The LC/MS showed pseudomolecular ions at 677 [M+H]+, 694 [M+NH4]+, and 699 [M+Na]+, indicating the loss of an acetyl group from taccalonolide Z. The proton NMR showed the chemical shift of H-15 of taccalonolide AB at δ 4.75 (ddd, J=3.5, 9.0, 11.6 Hz), which is shifted 0.78 ppm up-field than that of taccalonolide Z, suggesting the loss of acetyl group at 15-OH. The HMBC correlation between 15-OH (δ 4.94) and C-15 (δ 71.5) confirmed the assignment.

Provenance & Evidence