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The substitution of alkoxy groups of enol ethers (1-methoxycyclohexenes, 1-methoxy-l-alkenes, and benzofuran) and aryl ethers (methoxynaphthalenes, cresyl methyl ethers, and dimethoxybenzenes) by hydrogen, alkyl groups, and aryl units, through Grignard reactions catalyzed by bis(triphenylphosphine)nickel dichloride or [1,3-bis-(diphenylphosphino)propane]nickel dichloride, is described. The stereochemistry of the new reaction is portrayed, especially in connection with processes involving ring opening of dihydropyrans and dihydrofurans. The reaction has been applied to the synthesis of a termite trail pheromone and the acetate of the Douglas fir beetle aggregation pheromone.

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Taxol, a potent inhibitor of cell replication, enhances the assembly of tubulin into stable microtubules and promotes the formation of microtubule bundles in cells. In addition to its unique mechanism of action, taxol exhibits unusual promise as an antitumor agent, but its application in cancer chemotherapy is hampered by its limited availability. In order to better define the structure-activity profile of taxol for the design of more accessible drugs and to provide insight into the chemical features of the taxol-microtubule interaction, taxol analogues 3-8, with deleted A-ring side chain substituents and both R and S C-2' configurations, were synthesized from baccatin III through esterification at the hindered 13-hydroxyl. Employing an improved hydroxyl protection strategy, lactate analogues 3 and 4 were prepared with reasonable efficiency owing to their simple side-chain structures, while N-benzoylisoserine analogues 7 and 8 were synthesized through esterification reactions whose rates were enhanced greatly by the participation of the amide functionality. Although less biologically active than taxol, analogues 5-7 were found to promote the polymerization of tubulin and to be cytotoxic; 5 and 6 were considerably more effective than 7, whereas 3, 4, and 8 were least active. Interestingly, tubulin polymerization was sensitive to the C-2' configuration only when the amide substituent was present in the side chain. This observation suggests that the 3'-amide substituent plays an important role in preorganizing the taxol side chain to bind to microtubules.