10.1021/ol0502026
The study by Scott T. Handy and Duncan Omune investigates the reductive cyclization of tethered bis-enones with one-carbon tethers, focusing on the influence of reaction conditions and α-substitution on the cyclization pathway. They found that the cyclization products, either pinacol or hydrodimerization-type, are highly dependent on these factors. The researchers synthesized three cyclization substrates and explored their reductive cyclization under electrochemical conditions and using samarium diiodide. They observed that electrochemical conditions favored pinacol-type products, while samarium diiodide favored reductive cyclization products. The study suggests that chelation and steric effects play a crucial role in determining the cyclization pathway, with Lewis acidic metals promoting pinacol formation and non-chelatable metals favoring reductive cyclization. This mechanistic understanding was further supported by experiments using magnesium in methanol, which resulted in pinacol products. The findings highlight the importance of reaction conditions in controlling the cyclization outcome and provide insights into the mechanism of reductive cyclization reactions.
10.1006/bioo.1996.0009
The research focused on the synthesis and chiral separation of four Z-isomers of 1,1-dichloro-2,2,3-triarylcyclopropane (DTACs), which are potent antitumor agents designed to target hormone-dependent breast cancer. The purpose of the study was to develop pure antiestrogens that lack estrogen agonist activity, potentially offering more effective treatment for breast cancer patients, especially those resistant to tamoxifen. The researchers synthesized the DTACs through a series of reactions involving Grignard reagents, dehydration of intermediate carbinols, and dichlorocyclopropanation. Key chemicals used in the process included benzyl-4-benzyloxyphenyl ketone, 4-bromoanisole, magnesium turnings, anhydrous THF, and various other reagents for the Grignard reaction and subsequent steps. The study concluded with the successful synthesis of the Z-isomers and their enantiomeric separation using chiral chromatography with amylose tris-3,5-dimethylphenyl carbamate as the chiral stationary phase. The enantiomers were characterized by high-resolution NMR, and their optical rotations were determined, providing a foundation for further biological evaluation of their antitumor activity.
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