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Unformatted text preview: 6. Rank the four ketones shown below in order of increasing C=O stretching frequency in the IR spectra. ? 7. Propose a synthesis to accomplish the following transformation: page 2 4. Acetals and Ketals have relevance beyond simple protecting groups. Exo-brevicomin is a naturally- occuring ketal that is a constituent of the pheremone system of bark beetles. Propose a synthesis of exo-brevicomin starting from the illustrated starting material. ( It will be helpful here to work backwards from the product - what is the product? From what components are such things made? If you can make this retrosynthetic disconnection, then the connection between the starting material and your target will be more obvious. Once you see the pathway in broad terms you will then have to figure out how to orchestrate the reactions you need to do. ) ? O O Et Me exo-Brevicomin OH Et OH...
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- Spring '08
- Organic chemistry