Antitumor Agents. 43. Conversion of Bruceoside-A into Bruceantin

Article abstract of DOI:10.1021/jo00319a019

Bruceoside-A (1) has been converted by two methods to bruceantin (5), a potent antileukemic agent.The first method involved the hydrolysis of 1 with potassium hydroxide followed by p-toluenesulfonic acid in methanol to afford 49percent bruceolide (2).Esterification of 2 with 3,4-dimethyl-2-pentenoyl chloride (9) yielded the corresponding 3,15-diester (3) (47percent) and the 3-monoester (4) (31percent).Compound 4 was reconverted to 3 (77percent) by further esterification.Selective hydrolysis of 3 with p-toluenesulfonicacid afforded 5 in 40percent yield.The second method included the hydrolysis of 1 with potassium hydroxide to yield 57percent 15-desenecioyl bruceoside-A (6).Boron trifluoride etherate hydrolysis of the 3,4-dimethyl-2-pentenoyl ester (7), prepared by esterification of 6 with the corresponding acid chloride, gave 5 in 58percent yield.